FreeBSD/Linux Kernel Cross Reference
sys/vm/uma_core.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2002-2019 Jeffrey Roberson <jeff@FreeBSD.org>
      * Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
      * Copyright (c) 2004-2006 Robert N. M. Watson
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice unmodified, this list of conditions, and the following
     *    disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    /*
     * uma_core.c  Implementation of the Universal Memory allocator
     *
     * This allocator is intended to replace the multitude of similar object caches
     * in the standard FreeBSD kernel.  The intent is to be flexible as well as
     * efficient.  A primary design goal is to return unused memory to the rest of
     * the system.  This will make the system as a whole more flexible due to the
     * ability to move memory to subsystems which most need it instead of leaving
     * pools of reserved memory unused.
     *
     * The basic ideas stem from similar slab/zone based allocators whose algorithms
     * are well known.
     *
     */
    
    /*
     * TODO:
     *      - Improve memory usage for large allocations
     *      - Investigate cache size adjustments
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_ddb.h"
    #include "opt_param.h"
    #include "opt_vm.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bitset.h>
    #include <sys/domainset.h>
    #include <sys/eventhandler.h>
    #include <sys/kernel.h>
    #include <sys/types.h>
    #include <sys/limits.h>
    #include <sys/queue.h>
    #include <sys/malloc.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/sysctl.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/random.h>
    #include <sys/rwlock.h>
    #include <sys/sbuf.h>
    #include <sys/sched.h>
    #include <sys/sleepqueue.h>
    #include <sys/smp.h>
    #include <sys/smr.h>
    #include <sys/taskqueue.h>
    #include <sys/vmmeter.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_domainset.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_phys.h>
    #include <vm/vm_pagequeue.h>
    #include <vm/vm_map.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_dumpset.h>
    #include <vm/uma.h>
    #include <vm/uma_int.h>
    #include <vm/uma_dbg.h>
    
   #include <ddb/ddb.h>
   
   #ifdef DEBUG_MEMGUARD
   #include <vm/memguard.h>
   #endif
   
   #include <machine/md_var.h>
   
   #ifdef INVARIANTS
   #define UMA_ALWAYS_CTORDTOR     1
   #else
   #define UMA_ALWAYS_CTORDTOR     0
   #endif
   
   /*
    * This is the zone and keg from which all zones are spawned.
    */
   static uma_zone_t kegs;
   static uma_zone_t zones;
   
   /*
    * On INVARIANTS builds, the slab contains a second bitset of the same size,
    * "dbg_bits", which is laid out immediately after us_free.
    */
   #ifdef INVARIANTS
   #define SLAB_BITSETS    2
   #else
   #define SLAB_BITSETS    1
   #endif
   
   /*
    * These are the two zones from which all offpage uma_slab_ts are allocated.
    *
    * One zone is for slab headers that can represent a larger number of items,
    * making the slabs themselves more efficient, and the other zone is for
    * headers that are smaller and represent fewer items, making the headers more
    * efficient.
    */
   #define SLABZONE_SIZE(setsize)                                  \
       (sizeof(struct uma_hash_slab) + BITSET_SIZE(setsize) * SLAB_BITSETS)
   #define SLABZONE0_SETSIZE       (PAGE_SIZE / 16)
   #define SLABZONE1_SETSIZE       SLAB_MAX_SETSIZE
   #define SLABZONE0_SIZE  SLABZONE_SIZE(SLABZONE0_SETSIZE)
   #define SLABZONE1_SIZE  SLABZONE_SIZE(SLABZONE1_SETSIZE)
   static uma_zone_t slabzones[2];
   
   /*
    * The initial hash tables come out of this zone so they can be allocated
    * prior to malloc coming up.
    */
   static uma_zone_t hashzone;
   
   /* The boot-time adjusted value for cache line alignment. */
   int uma_align_cache = 64 - 1;
   
   static MALLOC_DEFINE(M_UMAHASH, "UMAHash", "UMA Hash Buckets");
   static MALLOC_DEFINE(M_UMA, "UMA", "UMA Misc");
   
   /*
    * Are we allowed to allocate buckets?
    */
   static int bucketdisable = 1;
   
   /* Linked list of all kegs in the system */
   static LIST_HEAD(,uma_keg) uma_kegs = LIST_HEAD_INITIALIZER(uma_kegs);
   
   /* Linked list of all cache-only zones in the system */
   static LIST_HEAD(,uma_zone) uma_cachezones =
       LIST_HEAD_INITIALIZER(uma_cachezones);
   
   /* This RW lock protects the keg list */
   static struct rwlock_padalign __exclusive_cache_line uma_rwlock;
   
   /*
    * First available virual address for boot time allocations.
    */
   static vm_offset_t bootstart;
   static vm_offset_t bootmem;
   
   static struct sx uma_reclaim_lock;
   
   /*
    * kmem soft limit, initialized by uma_set_limit().  Ensure that early
    * allocations don't trigger a wakeup of the reclaim thread.
    */
   unsigned long uma_kmem_limit = LONG_MAX;
   SYSCTL_ULONG(_vm, OID_AUTO, uma_kmem_limit, CTLFLAG_RD, &uma_kmem_limit, 0,
       "UMA kernel memory soft limit");
   unsigned long uma_kmem_total;
   SYSCTL_ULONG(_vm, OID_AUTO, uma_kmem_total, CTLFLAG_RD, &uma_kmem_total, 0,
       "UMA kernel memory usage");
   
   /* Is the VM done starting up? */
   static enum {
           BOOT_COLD,
           BOOT_KVA,
           BOOT_PCPU,
           BOOT_RUNNING,
           BOOT_SHUTDOWN,
   } booted = BOOT_COLD;
   
   /*
    * This is the handle used to schedule events that need to happen
    * outside of the allocation fast path.
    */
   static struct callout uma_callout;
   #define UMA_TIMEOUT     20              /* Seconds for callout interval. */
   
   /*
    * This structure is passed as the zone ctor arg so that I don't have to create
    * a special allocation function just for zones.
    */
   struct uma_zctor_args {
           const char *name;
           size_t size;
           uma_ctor ctor;
           uma_dtor dtor;
           uma_init uminit;
           uma_fini fini;
           uma_import import;
           uma_release release;
           void *arg;
           uma_keg_t keg;
           int align;
           uint32_t flags;
   };
   
   struct uma_kctor_args {
           uma_zone_t zone;
           size_t size;
           uma_init uminit;
           uma_fini fini;
           int align;
           uint32_t flags;
   };
   
   struct uma_bucket_zone {
           uma_zone_t      ubz_zone;
           const char      *ubz_name;
           int             ubz_entries;    /* Number of items it can hold. */
           int             ubz_maxsize;    /* Maximum allocation size per-item. */
   };
   
   /*
    * Compute the actual number of bucket entries to pack them in power
    * of two sizes for more efficient space utilization.
    */
   #define BUCKET_SIZE(n)                                          \
       (((sizeof(void *) * (n)) - sizeof(struct uma_bucket)) / sizeof(void *))
   
   #define BUCKET_MAX      BUCKET_SIZE(256)
   
   struct uma_bucket_zone bucket_zones[] = {
           /* Literal bucket sizes. */
           { NULL, "2 Bucket", 2, 4096 },
           { NULL, "4 Bucket", 4, 3072 },
           { NULL, "8 Bucket", 8, 2048 },
           { NULL, "16 Bucket", 16, 1024 },
           /* Rounded down power of 2 sizes for efficiency. */
           { NULL, "32 Bucket", BUCKET_SIZE(32), 512 },
           { NULL, "64 Bucket", BUCKET_SIZE(64), 256 },
           { NULL, "128 Bucket", BUCKET_SIZE(128), 128 },
           { NULL, "256 Bucket", BUCKET_SIZE(256), 64 },
           { NULL, NULL, 0}
   };
   
   /*
    * Flags and enumerations to be passed to internal functions.
    */
   enum zfreeskip {
           SKIP_NONE =     0,
           SKIP_CNT =      0x00000001,
           SKIP_DTOR =     0x00010000,
           SKIP_FINI =     0x00020000,
   };
   
   /* Prototypes.. */
   
   void    uma_startup1(vm_offset_t);
   void    uma_startup2(void);
   
   static void *noobj_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   static void *page_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   static void *pcpu_page_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   static void *startup_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   static void *contig_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   static void page_free(void *, vm_size_t, uint8_t);
   static void pcpu_page_free(void *, vm_size_t, uint8_t);
   static uma_slab_t keg_alloc_slab(uma_keg_t, uma_zone_t, int, int, int);
   static void cache_drain(uma_zone_t);
   static void bucket_drain(uma_zone_t, uma_bucket_t);
   static void bucket_cache_reclaim(uma_zone_t zone, bool);
   static int keg_ctor(void *, int, void *, int);
   static void keg_dtor(void *, int, void *);
   static int zone_ctor(void *, int, void *, int);
   static void zone_dtor(void *, int, void *);
   static inline void item_dtor(uma_zone_t zone, void *item, int size,
       void *udata, enum zfreeskip skip);
   static int zero_init(void *, int, int);
   static void zone_free_bucket(uma_zone_t zone, uma_bucket_t bucket, void *udata,
       int itemdomain, bool ws);
   static void zone_foreach(void (*zfunc)(uma_zone_t, void *), void *);
   static void zone_foreach_unlocked(void (*zfunc)(uma_zone_t, void *), void *);
   static void zone_timeout(uma_zone_t zone, void *);
   static int hash_alloc(struct uma_hash *, u_int);
   static int hash_expand(struct uma_hash *, struct uma_hash *);
   static void hash_free(struct uma_hash *hash);
   static void uma_timeout(void *);
   static void uma_shutdown(void);
   static void *zone_alloc_item(uma_zone_t, void *, int, int);
   static void zone_free_item(uma_zone_t, void *, void *, enum zfreeskip);
   static int zone_alloc_limit(uma_zone_t zone, int count, int flags);
   static void zone_free_limit(uma_zone_t zone, int count);
   static void bucket_enable(void);
   static void bucket_init(void);
   static uma_bucket_t bucket_alloc(uma_zone_t zone, void *, int);
   static void bucket_free(uma_zone_t zone, uma_bucket_t, void *);
   static void bucket_zone_drain(void);
   static uma_bucket_t zone_alloc_bucket(uma_zone_t, void *, int, int);
   static void *slab_alloc_item(uma_keg_t keg, uma_slab_t slab);
   static void slab_free_item(uma_zone_t zone, uma_slab_t slab, void *item);
   static uma_keg_t uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit,
       uma_fini fini, int align, uint32_t flags);
   static int zone_import(void *, void **, int, int, int);
   static void zone_release(void *, void **, int);
   static bool cache_alloc(uma_zone_t, uma_cache_t, void *, int);
   static bool cache_free(uma_zone_t, uma_cache_t, void *, void *, int);
   
   static int sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS);
   static int sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS);
   static int sysctl_handle_uma_zone_allocs(SYSCTL_HANDLER_ARGS);
   static int sysctl_handle_uma_zone_frees(SYSCTL_HANDLER_ARGS);
   static int sysctl_handle_uma_zone_flags(SYSCTL_HANDLER_ARGS);
   static int sysctl_handle_uma_slab_efficiency(SYSCTL_HANDLER_ARGS);
   static int sysctl_handle_uma_zone_items(SYSCTL_HANDLER_ARGS);
   
   static uint64_t uma_zone_get_allocs(uma_zone_t zone);
   
   static SYSCTL_NODE(_vm, OID_AUTO, debug, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
       "Memory allocation debugging");
   
   #ifdef INVARIANTS
   static uint64_t uma_keg_get_allocs(uma_keg_t zone);
   static inline struct noslabbits *slab_dbg_bits(uma_slab_t slab, uma_keg_t keg);
   
   static bool uma_dbg_kskip(uma_keg_t keg, void *mem);
   static bool uma_dbg_zskip(uma_zone_t zone, void *mem);
   static void uma_dbg_free(uma_zone_t zone, uma_slab_t slab, void *item);
   static void uma_dbg_alloc(uma_zone_t zone, uma_slab_t slab, void *item);
   
   static u_int dbg_divisor = 1;
   SYSCTL_UINT(_vm_debug, OID_AUTO, divisor,
       CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &dbg_divisor, 0,
       "Debug & thrash every this item in memory allocator");
   
   static counter_u64_t uma_dbg_cnt = EARLY_COUNTER;
   static counter_u64_t uma_skip_cnt = EARLY_COUNTER;
   SYSCTL_COUNTER_U64(_vm_debug, OID_AUTO, trashed, CTLFLAG_RD,
       &uma_dbg_cnt, "memory items debugged");
   SYSCTL_COUNTER_U64(_vm_debug, OID_AUTO, skipped, CTLFLAG_RD,
       &uma_skip_cnt, "memory items skipped, not debugged");
   #endif
   
   SYSCTL_NODE(_vm, OID_AUTO, uma, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
       "Universal Memory Allocator");
   
   SYSCTL_PROC(_vm, OID_AUTO, zone_count, CTLFLAG_RD|CTLFLAG_MPSAFE|CTLTYPE_INT,
       0, 0, sysctl_vm_zone_count, "I", "Number of UMA zones");
   
   SYSCTL_PROC(_vm, OID_AUTO, zone_stats, CTLFLAG_RD|CTLFLAG_MPSAFE|CTLTYPE_STRUCT,
       0, 0, sysctl_vm_zone_stats, "s,struct uma_type_header", "Zone Stats");
   
   static int zone_warnings = 1;
   SYSCTL_INT(_vm, OID_AUTO, zone_warnings, CTLFLAG_RWTUN, &zone_warnings, 0,
       "Warn when UMA zones becomes full");
   
   static int multipage_slabs = 1;
   TUNABLE_INT("vm.debug.uma_multipage_slabs", &multipage_slabs);
   SYSCTL_INT(_vm_debug, OID_AUTO, uma_multipage_slabs,
       CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &multipage_slabs, 0,
       "UMA may choose larger slab sizes for better efficiency");
   
   /*
    * Select the slab zone for an offpage slab with the given maximum item count.
    */
   static inline uma_zone_t
   slabzone(int ipers)
   {
   
           return (slabzones[ipers > SLABZONE0_SETSIZE]);
   }
   
   /*
    * This routine checks to see whether or not it's safe to enable buckets.
    */
   static void
   bucket_enable(void)
   {
   
           KASSERT(booted >= BOOT_KVA, ("Bucket enable before init"));
           bucketdisable = vm_page_count_min();
   }
   
   /*
    * Initialize bucket_zones, the array of zones of buckets of various sizes.
    *
    * For each zone, calculate the memory required for each bucket, consisting
    * of the header and an array of pointers.
    */
   static void
   bucket_init(void)
   {
           struct uma_bucket_zone *ubz;
           int size;
   
           for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++) {
                   size = roundup(sizeof(struct uma_bucket), sizeof(void *));
                   size += sizeof(void *) * ubz->ubz_entries;
                   ubz->ubz_zone = uma_zcreate(ubz->ubz_name, size,
                       NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
                       UMA_ZONE_MTXCLASS | UMA_ZFLAG_BUCKET |
                       UMA_ZONE_FIRSTTOUCH);
           }
   }
   
   /*
    * Given a desired number of entries for a bucket, return the zone from which
    * to allocate the bucket.
    */
   static struct uma_bucket_zone *
   bucket_zone_lookup(int entries)
   {
           struct uma_bucket_zone *ubz;
   
           for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++)
                   if (ubz->ubz_entries >= entries)
                           return (ubz);
           ubz--;
           return (ubz);
   }
   
   static int
   bucket_select(int size)
   {
           struct uma_bucket_zone *ubz;
   
           ubz = &bucket_zones[0];
           if (size > ubz->ubz_maxsize)
                   return MAX((ubz->ubz_maxsize * ubz->ubz_entries) / size, 1);
   
           for (; ubz->ubz_entries != 0; ubz++)
                   if (ubz->ubz_maxsize < size)
                           break;
           ubz--;
           return (ubz->ubz_entries);
   }
   
   static uma_bucket_t
   bucket_alloc(uma_zone_t zone, void *udata, int flags)
   {
           struct uma_bucket_zone *ubz;
           uma_bucket_t bucket;
   
           /*
            * Don't allocate buckets early in boot.
            */
           if (__predict_false(booted < BOOT_KVA))
                   return (NULL);
   
           /*
            * To limit bucket recursion we store the original zone flags
            * in a cookie passed via zalloc_arg/zfree_arg.  This allows the
            * NOVM flag to persist even through deep recursions.  We also
            * store ZFLAG_BUCKET once we have recursed attempting to allocate
            * a bucket for a bucket zone so we do not allow infinite bucket
            * recursion.  This cookie will even persist to frees of unused
            * buckets via the allocation path or bucket allocations in the
            * free path.
            */
           if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
                   udata = (void *)(uintptr_t)zone->uz_flags;
           else {
                   if ((uintptr_t)udata & UMA_ZFLAG_BUCKET)
                           return (NULL);
                   udata = (void *)((uintptr_t)udata | UMA_ZFLAG_BUCKET);
           }
           if (((uintptr_t)udata & UMA_ZONE_VM) != 0)
                   flags |= M_NOVM;
           ubz = bucket_zone_lookup(atomic_load_16(&zone->uz_bucket_size));
           if (ubz->ubz_zone == zone && (ubz + 1)->ubz_entries != 0)
                   ubz++;
           bucket = uma_zalloc_arg(ubz->ubz_zone, udata, flags);
           if (bucket) {
   #ifdef INVARIANTS
                   bzero(bucket->ub_bucket, sizeof(void *) * ubz->ubz_entries);
   #endif
                   bucket->ub_cnt = 0;
                   bucket->ub_entries = min(ubz->ubz_entries,
                       zone->uz_bucket_size_max);
                   bucket->ub_seq = SMR_SEQ_INVALID;
                   CTR3(KTR_UMA, "bucket_alloc: zone %s(%p) allocated bucket %p",
                       zone->uz_name, zone, bucket);
           }
   
           return (bucket);
   }
   
   static void
   bucket_free(uma_zone_t zone, uma_bucket_t bucket, void *udata)
   {
           struct uma_bucket_zone *ubz;
   
           if (bucket->ub_cnt != 0)
                   bucket_drain(zone, bucket);
   
           KASSERT(bucket->ub_cnt == 0,
               ("bucket_free: Freeing a non free bucket."));
           KASSERT(bucket->ub_seq == SMR_SEQ_INVALID,
               ("bucket_free: Freeing an SMR bucket."));
           if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
                   udata = (void *)(uintptr_t)zone->uz_flags;
           ubz = bucket_zone_lookup(bucket->ub_entries);
           uma_zfree_arg(ubz->ubz_zone, bucket, udata);
   }
   
   static void
   bucket_zone_drain(void)
   {
           struct uma_bucket_zone *ubz;
   
           for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++)
                   uma_zone_reclaim(ubz->ubz_zone, UMA_RECLAIM_DRAIN);
   }
   
   /*
    * Acquire the domain lock and record contention.
    */
   static uma_zone_domain_t
   zone_domain_lock(uma_zone_t zone, int domain)
   {
           uma_zone_domain_t zdom;
           bool lockfail;
   
           zdom = ZDOM_GET(zone, domain);
           lockfail = false;
           if (ZDOM_OWNED(zdom))
                   lockfail = true;
           ZDOM_LOCK(zdom);
           /* This is unsynchronized.  The counter does not need to be precise. */
           if (lockfail && zone->uz_bucket_size < zone->uz_bucket_size_max)
                   zone->uz_bucket_size++;
           return (zdom);
   }
   
   /*
    * Search for the domain with the least cached items and return it if it
    * is out of balance with the preferred domain.
    */
   static __noinline int
   zone_domain_lowest(uma_zone_t zone, int pref)
   {
           long least, nitems, prefitems;
           int domain;
           int i;
   
           prefitems = least = LONG_MAX;
           domain = 0;
           for (i = 0; i < vm_ndomains; i++) {
                   nitems = ZDOM_GET(zone, i)->uzd_nitems;
                   if (nitems < least) {
                           domain = i;
                           least = nitems;
                   }
                   if (domain == pref)
                           prefitems = nitems;
           }
           if (prefitems < least * 2)
                   return (pref);
   
           return (domain);
   }
   
   /*
    * Search for the domain with the most cached items and return it or the
    * preferred domain if it has enough to proceed.
    */
   static __noinline int
   zone_domain_highest(uma_zone_t zone, int pref)
   {
           long most, nitems;
           int domain;
           int i;
   
           if (ZDOM_GET(zone, pref)->uzd_nitems > BUCKET_MAX)
                   return (pref);
   
           most = 0;
           domain = 0;
           for (i = 0; i < vm_ndomains; i++) {
                   nitems = ZDOM_GET(zone, i)->uzd_nitems;
                   if (nitems > most) {
                           domain = i;
                           most = nitems;
                   }
           }
   
           return (domain);
   }
   
   /*
    * Safely subtract cnt from imax.
    */
   static void
   zone_domain_imax_sub(uma_zone_domain_t zdom, int cnt)
   {
           long new;
           long old;
   
           old = zdom->uzd_imax;
           do {
                   if (old <= cnt)
                           new = 0;
                   else
                           new = old - cnt;
           } while (atomic_fcmpset_long(&zdom->uzd_imax, &old, new) == 0);
   }
   
   /*
    * Set the maximum imax value.
    */
   static void
   zone_domain_imax_set(uma_zone_domain_t zdom, int nitems)
   {
           long old;
   
           old = zdom->uzd_imax;
           do {
                   if (old >= nitems)
                           break;
           } while (atomic_fcmpset_long(&zdom->uzd_imax, &old, nitems) == 0);
   }
   
   /*
    * Attempt to satisfy an allocation by retrieving a full bucket from one of the
    * zone's caches.  If a bucket is found the zone is not locked on return.
    */
   static uma_bucket_t
   zone_fetch_bucket(uma_zone_t zone, uma_zone_domain_t zdom, bool reclaim)
   {
           uma_bucket_t bucket;
           int i;
           bool dtor = false;
   
           ZDOM_LOCK_ASSERT(zdom);
   
           if ((bucket = STAILQ_FIRST(&zdom->uzd_buckets)) == NULL)
                   return (NULL);
   
           /* SMR Buckets can not be re-used until readers expire. */
           if ((zone->uz_flags & UMA_ZONE_SMR) != 0 &&
               bucket->ub_seq != SMR_SEQ_INVALID) {
                   if (!smr_poll(zone->uz_smr, bucket->ub_seq, false))
                           return (NULL);
                   bucket->ub_seq = SMR_SEQ_INVALID;
                   dtor = (zone->uz_dtor != NULL) || UMA_ALWAYS_CTORDTOR;
                   if (STAILQ_NEXT(bucket, ub_link) != NULL)
                           zdom->uzd_seq = STAILQ_NEXT(bucket, ub_link)->ub_seq;
           }
           STAILQ_REMOVE_HEAD(&zdom->uzd_buckets, ub_link);
   
           KASSERT(zdom->uzd_nitems >= bucket->ub_cnt,
               ("%s: item count underflow (%ld, %d)",
               __func__, zdom->uzd_nitems, bucket->ub_cnt));
           KASSERT(bucket->ub_cnt > 0,
               ("%s: empty bucket in bucket cache", __func__));
           zdom->uzd_nitems -= bucket->ub_cnt;
   
           /*
            * Shift the bounds of the current WSS interval to avoid
            * perturbing the estimate.
            */
           if (reclaim) {
                   zdom->uzd_imin -= lmin(zdom->uzd_imin, bucket->ub_cnt);
                   zone_domain_imax_sub(zdom, bucket->ub_cnt);
           } else if (zdom->uzd_imin > zdom->uzd_nitems)
                   zdom->uzd_imin = zdom->uzd_nitems;
   
           ZDOM_UNLOCK(zdom);
           if (dtor)
                   for (i = 0; i < bucket->ub_cnt; i++)
                           item_dtor(zone, bucket->ub_bucket[i], zone->uz_size,
                               NULL, SKIP_NONE);
   
           return (bucket);
   }
   
   /*
    * Insert a full bucket into the specified cache.  The "ws" parameter indicates
    * whether the bucket's contents should be counted as part of the zone's working
    * set.  The bucket may be freed if it exceeds the bucket limit.
    */
   static void
   zone_put_bucket(uma_zone_t zone, int domain, uma_bucket_t bucket, void *udata,
       const bool ws)
   {
           uma_zone_domain_t zdom;
   
           /* We don't cache empty buckets.  This can happen after a reclaim. */
           if (bucket->ub_cnt == 0)
                   goto out;
           zdom = zone_domain_lock(zone, domain);
   
           /*
            * Conditionally set the maximum number of items.
            */
           zdom->uzd_nitems += bucket->ub_cnt;
           if (__predict_true(zdom->uzd_nitems < zone->uz_bucket_max)) {
                   if (ws)
                           zone_domain_imax_set(zdom, zdom->uzd_nitems);
                   if (STAILQ_EMPTY(&zdom->uzd_buckets))
                           zdom->uzd_seq = bucket->ub_seq;
   
                   /*
                    * Try to promote reuse of recently used items.  For items
                    * protected by SMR, try to defer reuse to minimize polling.
                    */
                   if (bucket->ub_seq == SMR_SEQ_INVALID)
                           STAILQ_INSERT_HEAD(&zdom->uzd_buckets, bucket, ub_link);
                   else
                           STAILQ_INSERT_TAIL(&zdom->uzd_buckets, bucket, ub_link);
                   ZDOM_UNLOCK(zdom);
                   return;
           }
           zdom->uzd_nitems -= bucket->ub_cnt;
           ZDOM_UNLOCK(zdom);
   out:
           bucket_free(zone, bucket, udata);
   }
   
   /* Pops an item out of a per-cpu cache bucket. */
   static inline void *
   cache_bucket_pop(uma_cache_t cache, uma_cache_bucket_t bucket)
   {
           void *item;
   
           CRITICAL_ASSERT(curthread);
   
           bucket->ucb_cnt--;
           item = bucket->ucb_bucket->ub_bucket[bucket->ucb_cnt];
   #ifdef INVARIANTS
           bucket->ucb_bucket->ub_bucket[bucket->ucb_cnt] = NULL;
           KASSERT(item != NULL, ("uma_zalloc: Bucket pointer mangled."));
   #endif
           cache->uc_allocs++;
   
           return (item);
   }
   
   /* Pushes an item into a per-cpu cache bucket. */
   static inline void
   cache_bucket_push(uma_cache_t cache, uma_cache_bucket_t bucket, void *item)
   {
   
           CRITICAL_ASSERT(curthread);
           KASSERT(bucket->ucb_bucket->ub_bucket[bucket->ucb_cnt] == NULL,
               ("uma_zfree: Freeing to non free bucket index."));
   
           bucket->ucb_bucket->ub_bucket[bucket->ucb_cnt] = item;
           bucket->ucb_cnt++;
           cache->uc_frees++;
   }
   
   /*
    * Unload a UMA bucket from a per-cpu cache.
    */
   static inline uma_bucket_t
   cache_bucket_unload(uma_cache_bucket_t bucket)
   {
           uma_bucket_t b;
   
           b = bucket->ucb_bucket;
           if (b != NULL) {
                   MPASS(b->ub_entries == bucket->ucb_entries);
                   b->ub_cnt = bucket->ucb_cnt;
                   bucket->ucb_bucket = NULL;
                   bucket->ucb_entries = bucket->ucb_cnt = 0;
           }
   
           return (b);
   }
   
   static inline uma_bucket_t
   cache_bucket_unload_alloc(uma_cache_t cache)
   {
   
           return (cache_bucket_unload(&cache->uc_allocbucket));
   }
   
   static inline uma_bucket_t
   cache_bucket_unload_free(uma_cache_t cache)
   {
   
           return (cache_bucket_unload(&cache->uc_freebucket));
   }
   
   static inline uma_bucket_t
   cache_bucket_unload_cross(uma_cache_t cache)
   {
   
           return (cache_bucket_unload(&cache->uc_crossbucket));
   }
   
   /*
    * Load a bucket into a per-cpu cache bucket.
    */
   static inline void
   cache_bucket_load(uma_cache_bucket_t bucket, uma_bucket_t b)
   {
   
           CRITICAL_ASSERT(curthread);
           MPASS(bucket->ucb_bucket == NULL);
           MPASS(b->ub_seq == SMR_SEQ_INVALID);
   
           bucket->ucb_bucket = b;
           bucket->ucb_cnt = b->ub_cnt;
           bucket->ucb_entries = b->ub_entries;
   }
   
   static inline void
   cache_bucket_load_alloc(uma_cache_t cache, uma_bucket_t b)
   {
   
           cache_bucket_load(&cache->uc_allocbucket, b);
   }
   
   static inline void
   cache_bucket_load_free(uma_cache_t cache, uma_bucket_t b)
   {
   
           cache_bucket_load(&cache->uc_freebucket, b);
   }
   
   #ifdef NUMA
   static inline void 
   cache_bucket_load_cross(uma_cache_t cache, uma_bucket_t b)
   {
   
           cache_bucket_load(&cache->uc_crossbucket, b);
   }
   #endif
   
   /*
    * Copy and preserve ucb_spare.
    */
   static inline void
   cache_bucket_copy(uma_cache_bucket_t b1, uma_cache_bucket_t b2)
   {
   
           b1->ucb_bucket = b2->ucb_bucket;
           b1->ucb_entries = b2->ucb_entries;
           b1->ucb_cnt = b2->ucb_cnt;
   }
   
   /*
    * Swap two cache buckets.
    */
   static inline void
   cache_bucket_swap(uma_cache_bucket_t b1, uma_cache_bucket_t b2)
   {
           struct uma_cache_bucket b3;
   
           CRITICAL_ASSERT(curthread);
   
           cache_bucket_copy(&b3, b1);
           cache_bucket_copy(b1, b2);
           cache_bucket_copy(b2, &b3);
   }
   
   /*
    * Attempt to fetch a bucket from a zone on behalf of the current cpu cache.
    */
   static uma_bucket_t
   cache_fetch_bucket(uma_zone_t zone, uma_cache_t cache, int domain)
   {
           uma_zone_domain_t zdom;
           uma_bucket_t bucket;
   
           /*
            * Avoid the lock if possible.
            */
           zdom = ZDOM_GET(zone, domain);
           if (zdom->uzd_nitems == 0)
                   return (NULL);
   
           if ((cache_uz_flags(cache) & UMA_ZONE_SMR) != 0 &&
               !smr_poll(zone->uz_smr, zdom->uzd_seq, false))
                   return (NULL);
   
           /*
            * Check the zone's cache of buckets.
            */
           zdom = zone_domain_lock(zone, domain);
           if ((bucket = zone_fetch_bucket(zone, zdom, false)) != NULL)
                   return (bucket);
           ZDOM_UNLOCK(zdom);
   
           return (NULL);
   }
   
   static void
   zone_log_warning(uma_zone_t zone)
   {
           static const struct timeval warninterval = { 300, 0 };
   
           if (!zone_warnings || zone->uz_warning == NULL)
                   return;
   
           if (ratecheck(&zone->uz_ratecheck, &warninterval))
                   printf("[zone: %s] %s\n", zone->uz_name, zone->uz_warning);
   }
   
   static inline void
   zone_maxaction(uma_zone_t zone)
   {
   
           if (zone->uz_maxaction.ta_func != NULL)
                   taskqueue_enqueue(taskqueue_thread, &zone->uz_maxaction);
   }
   
   /*
    * Routine called by timeout which is used to fire off some time interval
    * based calculations.  (stats, hash size, etc.)
    *
    * Arguments:
    *      arg   Unused
    *
    * Returns:
    *      Nothing
    */
   static void
   uma_timeout(void *unused)
   {
           bucket_enable();
           zone_foreach(zone_timeout, NULL);
   
           /* Reschedule this event */
           callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
   }
   
   /*
    * Update the working set size estimate for the zone's bucket cache.
    * The constants chosen here are somewhat arbitrary.  With an update period of
    * 20s (UMA_TIMEOUT), this estimate is dominated by zone activity over the
    * last 100s.
    */
   static void
   zone_domain_update_wss(uma_zone_domain_t zdom)
   {
           long wss;
   
           ZDOM_LOCK(zdom);
           MPASS(zdom->uzd_imax >= zdom->uzd_imin);
           wss = zdom->uzd_imax - zdom->uzd_imin;
           zdom->uzd_imax = zdom->uzd_imin = zdom->uzd_nitems;
           zdom->uzd_wss = (4 * wss + zdom->uzd_wss) / 5;
           ZDOM_UNLOCK(zdom);
   }
   
   /*
    * Routine to perform timeout driven calculations.  This expands the
    * hashes and does per cpu statistics aggregation.
    *
    *  Returns nothing.
    */
   static void
   zone_timeout(uma_zone_t zone, void *unused)
   {
           uma_keg_t keg;
           u_int slabs, pages;
   
           if ((zone->uz_flags & UMA_ZFLAG_HASH) == 0)
                   goto update_wss;
   
           keg = zone->uz_keg;
   
           /*
            * Hash zones are non-numa by definition so the first domain
            * is the only one present.
            */
           KEG_LOCK(keg, 0);
           pages = keg->uk_domain[0].ud_pages;
   
           /*
            * Expand the keg hash table.
            *
            * This is done if the number of slabs is larger than the hash size.
            * What I'm trying to do here is completely reduce collisions.  This
            * may be a little aggressive.  Should I allow for two collisions max?
            */
           if ((slabs = pages / keg->uk_ppera) > keg->uk_hash.uh_hashsize) {
                  struct uma_hash newhash;
                  struct uma_hash oldhash;
                  int ret;
  
                  /*
                   * This is so involved because allocating and freeing
                   * while the keg lock is held will lead to deadlock.
                   * I have to do everything in stages and check for
                   * races.
                   */
                  KEG_UNLOCK(keg, 0);
                  ret = hash_alloc(&newhash, 1 << fls(slabs));
                  KEG_LOCK(keg, 0);
                  if (ret) {
                          if (hash_expand(&keg->uk_hash, &newhash)) {
                                  oldhash = keg->uk_hash;
                                  keg->uk_hash = newhash;
                          } else
                                  oldhash = newhash;
  
                          KEG_UNLOCK(keg, 0);
                          hash_free(&oldhash);
                          goto update_wss;
                  }
          }
          KEG_UNLOCK(keg, 0);
  
  update_wss:
          for (int i = 0; i < vm_ndomains; i++)
                  zone_domain_update_wss(ZDOM_GET(zone, i));
  }
  
  /*
   * Allocate and zero fill the next sized hash table from the appropriate
   * backing store.
   *
   * Arguments:
   *      hash  A new hash structure with the old hash size in uh_hashsize
   *
   * Returns:
   *      1 on success and 0 on failure.
   */
  static int
  hash_alloc(struct uma_hash *hash, u_int size)
  {
          size_t alloc;
  
          KASSERT(powerof2(size), ("hash size must be power of 2"));
          if (size > UMA_HASH_SIZE_INIT)  {
                  hash->uh_hashsize = size;
                  alloc = sizeof(hash->uh_slab_hash[0]) * hash->uh_hashsize;
                  hash->uh_slab_hash = malloc(alloc, M_UMAHASH, M_NOWAIT);
          } else {
                  alloc = sizeof(hash->uh_slab_hash[0]) * UMA_HASH_SIZE_INIT;
                  hash->uh_slab_hash = zone_alloc_item(hashzone, NULL,
                      UMA_ANYDOMAIN, M_WAITOK);
                  hash->uh_hashsize = UMA_HASH_SIZE_INIT;
          }
          if (hash->uh_slab_hash) {
                  bzero(hash->uh_slab_hash, alloc);
                  hash->uh_hashmask = hash->uh_hashsize - 1;
                  return (1);
          }
  
          return (0);
  }
  
  /*
   * Expands the hash table for HASH zones.  This is done from zone_timeout
   * to reduce collisions.  This must not be done in the regular allocation
   * path, otherwise, we can recurse on the vm while allocating pages.
   *
   * Arguments:
   *      oldhash  The hash you want to expand
   *      newhash  The hash structure for the new table
   *
   * Returns:
   *      Nothing
   *
   * Discussion:
   */
  static int
  hash_expand(struct uma_hash *oldhash, struct uma_hash *newhash)
  {
          uma_hash_slab_t slab;
          u_int hval;
          u_int idx;
  
          if (!newhash->uh_slab_hash)
                  return (0);
  
          if (oldhash->uh_hashsize >= newhash->uh_hashsize)
                  return (0);
  
          /*
           * I need to investigate hash algorithms for resizing without a
           * full rehash.
           */
  
          for (idx = 0; idx < oldhash->uh_hashsize; idx++)
                  while (!LIST_EMPTY(&oldhash->uh_slab_hash[idx])) {
                          slab = LIST_FIRST(&oldhash->uh_slab_hash[idx]);
                          LIST_REMOVE(slab, uhs_hlink);
                          hval = UMA_HASH(newhash, slab->uhs_data);
                          LIST_INSERT_HEAD(&newhash->uh_slab_hash[hval],
                              slab, uhs_hlink);
                  }
  
          return (1);
  }
  
  /*
   * Free the hash bucket to the appropriate backing store.
   *
   * Arguments:
   *      slab_hash  The hash bucket we're freeing
   *      hashsize   The number of entries in that hash bucket
   *
   * Returns:
   *      Nothing
   */
  static void
  hash_free(struct uma_hash *hash)
  {
          if (hash->uh_slab_hash == NULL)
                  return;
          if (hash->uh_hashsize == UMA_HASH_SIZE_INIT)
                  zone_free_item(hashzone, hash->uh_slab_hash, NULL, SKIP_NONE);
          else
                  free(hash->uh_slab_hash, M_UMAHASH);
  }
  
  /*
   * Frees all outstanding items in a bucket
   *
   * Arguments:
   *      zone   The zone to free to, must be unlocked.
   *      bucket The free/alloc bucket with items.
   *
   * Returns:
   *      Nothing
   */
  static void
  bucket_drain(uma_zone_t zone, uma_bucket_t bucket)
  {
          int i;
  
          if (bucket->ub_cnt == 0)
                  return;
  
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0 &&
              bucket->ub_seq != SMR_SEQ_INVALID) {
                  smr_wait(zone->uz_smr, bucket->ub_seq);
                  bucket->ub_seq = SMR_SEQ_INVALID;
                  for (i = 0; i < bucket->ub_cnt; i++)
                          item_dtor(zone, bucket->ub_bucket[i],
                              zone->uz_size, NULL, SKIP_NONE);
          }
          if (zone->uz_fini)
                  for (i = 0; i < bucket->ub_cnt; i++) 
                          zone->uz_fini(bucket->ub_bucket[i], zone->uz_size);
          zone->uz_release(zone->uz_arg, bucket->ub_bucket, bucket->ub_cnt);
          if (zone->uz_max_items > 0)
                  zone_free_limit(zone, bucket->ub_cnt);
  #ifdef INVARIANTS
          bzero(bucket->ub_bucket, sizeof(void *) * bucket->ub_cnt);
  #endif
          bucket->ub_cnt = 0;
  }
  
  /*
   * Drains the per cpu caches for a zone.
   *
   * NOTE: This may only be called while the zone is being torn down, and not
   * during normal operation.  This is necessary in order that we do not have
   * to migrate CPUs to drain the per-CPU caches.
   *
   * Arguments:
   *      zone     The zone to drain, must be unlocked.
   *
   * Returns:
   *      Nothing
   */
  static void
  cache_drain(uma_zone_t zone)
  {
          uma_cache_t cache;
          uma_bucket_t bucket;
          smr_seq_t seq;
          int cpu;
  
          /*
           * XXX: It is safe to not lock the per-CPU caches, because we're
           * tearing down the zone anyway.  I.e., there will be no further use
           * of the caches at this point.
           *
           * XXX: It would good to be able to assert that the zone is being
           * torn down to prevent improper use of cache_drain().
           */
          seq = SMR_SEQ_INVALID;
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0)
                  seq = smr_advance(zone->uz_smr);
          CPU_FOREACH(cpu) {
                  cache = &zone->uz_cpu[cpu];
                  bucket = cache_bucket_unload_alloc(cache);
                  if (bucket != NULL)
                          bucket_free(zone, bucket, NULL);
                  bucket = cache_bucket_unload_free(cache);
                  if (bucket != NULL) {
                          bucket->ub_seq = seq;
                          bucket_free(zone, bucket, NULL);
                  }
                  bucket = cache_bucket_unload_cross(cache);
                  if (bucket != NULL) {
                          bucket->ub_seq = seq;
                          bucket_free(zone, bucket, NULL);
                  }
          }
          bucket_cache_reclaim(zone, true);
  }
  
  static void
  cache_shrink(uma_zone_t zone, void *unused)
  {
  
          if (zone->uz_flags & UMA_ZFLAG_INTERNAL)
                  return;
  
          zone->uz_bucket_size =
              (zone->uz_bucket_size_min + zone->uz_bucket_size) / 2;
  }
  
  static void
  cache_drain_safe_cpu(uma_zone_t zone, void *unused)
  {
          uma_cache_t cache;
          uma_bucket_t b1, b2, b3;
          int domain;
  
          if (zone->uz_flags & UMA_ZFLAG_INTERNAL)
                  return;
  
          b1 = b2 = b3 = NULL;
          critical_enter();
          cache = &zone->uz_cpu[curcpu];
          domain = PCPU_GET(domain);
          b1 = cache_bucket_unload_alloc(cache);
  
          /*
           * Don't flush SMR zone buckets.  This leaves the zone without a
           * bucket and forces every free to synchronize().
           */
          if ((zone->uz_flags & UMA_ZONE_SMR) == 0) {
                  b2 = cache_bucket_unload_free(cache);
                  b3 = cache_bucket_unload_cross(cache);
          }
          critical_exit();
  
          if (b1 != NULL)
                  zone_free_bucket(zone, b1, NULL, domain, false);
          if (b2 != NULL)
                  zone_free_bucket(zone, b2, NULL, domain, false);
          if (b3 != NULL) {
                  /* Adjust the domain so it goes to zone_free_cross. */
                  domain = (domain + 1) % vm_ndomains;
                  zone_free_bucket(zone, b3, NULL, domain, false);
          }
  }
  
  /*
   * Safely drain per-CPU caches of a zone(s) to alloc bucket.
   * This is an expensive call because it needs to bind to all CPUs
   * one by one and enter a critical section on each of them in order
   * to safely access their cache buckets.
   * Zone lock must not be held on call this function.
   */
  static void
  pcpu_cache_drain_safe(uma_zone_t zone)
  {
          int cpu;
  
          /*
           * Polite bucket sizes shrinking was not enough, shrink aggressively.
           */
          if (zone)
                  cache_shrink(zone, NULL);
          else
                  zone_foreach(cache_shrink, NULL);
  
          CPU_FOREACH(cpu) {
                  thread_lock(curthread);
                  sched_bind(curthread, cpu);
                  thread_unlock(curthread);
  
                  if (zone)
                          cache_drain_safe_cpu(zone, NULL);
                  else
                          zone_foreach(cache_drain_safe_cpu, NULL);
          }
          thread_lock(curthread);
          sched_unbind(curthread);
          thread_unlock(curthread);
  }
  
  /*
   * Reclaim cached buckets from a zone.  All buckets are reclaimed if the caller
   * requested a drain, otherwise the per-domain caches are trimmed to either
   * estimated working set size.
   */
  static void
  bucket_cache_reclaim(uma_zone_t zone, bool drain)
  {
          uma_zone_domain_t zdom;
          uma_bucket_t bucket;
          long target;
          int i;
  
          /*
           * Shrink the zone bucket size to ensure that the per-CPU caches
           * don't grow too large.
           */
          if (zone->uz_bucket_size > zone->uz_bucket_size_min)
                  zone->uz_bucket_size--;
  
          for (i = 0; i < vm_ndomains; i++) {
                  /*
                   * The cross bucket is partially filled and not part of
                   * the item count.  Reclaim it individually here.
                   */
                  zdom = ZDOM_GET(zone, i);
                  if ((zone->uz_flags & UMA_ZONE_SMR) == 0 || drain) {
                          ZONE_CROSS_LOCK(zone);
                          bucket = zdom->uzd_cross;
                          zdom->uzd_cross = NULL;
                          ZONE_CROSS_UNLOCK(zone);
                          if (bucket != NULL)
                                  bucket_free(zone, bucket, NULL);
                  }
  
                  /*
                   * If we were asked to drain the zone, we are done only once
                   * this bucket cache is empty.  Otherwise, we reclaim items in
                   * excess of the zone's estimated working set size.  If the
                   * difference nitems - imin is larger than the WSS estimate,
                   * then the estimate will grow at the end of this interval and
                   * we ignore the historical average.
                   */
                  ZDOM_LOCK(zdom);
                  target = drain ? 0 : lmax(zdom->uzd_wss, zdom->uzd_nitems -
                      zdom->uzd_imin);
                  while (zdom->uzd_nitems > target) {
                          bucket = zone_fetch_bucket(zone, zdom, true);
                          if (bucket == NULL)
                                  break;
                          bucket_free(zone, bucket, NULL);
                          ZDOM_LOCK(zdom);
                  }
                  ZDOM_UNLOCK(zdom);
          }
  }
  
  static void
  keg_free_slab(uma_keg_t keg, uma_slab_t slab, int start)
  {
          uint8_t *mem;
          int i;
          uint8_t flags;
  
          CTR4(KTR_UMA, "keg_free_slab keg %s(%p) slab %p, returning %d bytes",
              keg->uk_name, keg, slab, PAGE_SIZE * keg->uk_ppera);
  
          mem = slab_data(slab, keg);
          flags = slab->us_flags;
          i = start;
          if (keg->uk_fini != NULL) {
                  for (i--; i > -1; i--)
  #ifdef INVARIANTS
                  /*
                   * trash_fini implies that dtor was trash_dtor. trash_fini
                   * would check that memory hasn't been modified since free,
                   * which executed trash_dtor.
                   * That's why we need to run uma_dbg_kskip() check here,
                   * albeit we don't make skip check for other init/fini
                   * invocations.
                   */
                  if (!uma_dbg_kskip(keg, slab_item(slab, keg, i)) ||
                      keg->uk_fini != trash_fini)
  #endif
                          keg->uk_fini(slab_item(slab, keg, i), keg->uk_size);
          }
          if (keg->uk_flags & UMA_ZFLAG_OFFPAGE)
                  zone_free_item(slabzone(keg->uk_ipers), slab_tohashslab(slab),
                      NULL, SKIP_NONE);
          keg->uk_freef(mem, PAGE_SIZE * keg->uk_ppera, flags);
          uma_total_dec(PAGE_SIZE * keg->uk_ppera);
  }
  
  static void
  keg_drain_domain(uma_keg_t keg, int domain)
  {
          struct slabhead freeslabs;
          uma_domain_t dom;
          uma_slab_t slab, tmp;
          uint32_t i, stofree, stokeep, partial;
  
          dom = &keg->uk_domain[domain];
          LIST_INIT(&freeslabs);
  
          CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u",
              keg->uk_name, keg, domain, dom->ud_free_items);
  
          KEG_LOCK(keg, domain);
  
          /*
           * Are the free items in partially allocated slabs sufficient to meet
           * the reserve? If not, compute the number of fully free slabs that must
           * be kept.
           */
          partial = dom->ud_free_items - dom->ud_free_slabs * keg->uk_ipers;
          if (partial < keg->uk_reserve) {
                  stokeep = min(dom->ud_free_slabs,
                      howmany(keg->uk_reserve - partial, keg->uk_ipers));
          } else {
                  stokeep = 0;
          }
          stofree = dom->ud_free_slabs - stokeep;
  
          /*
           * Partition the free slabs into two sets: those that must be kept in
           * order to maintain the reserve, and those that may be released back to
           * the system.  Since one set may be much larger than the other,
           * populate the smaller of the two sets and swap them if necessary.
           */
          for (i = min(stofree, stokeep); i > 0; i--) {
                  slab = LIST_FIRST(&dom->ud_free_slab);
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&freeslabs, slab, us_link);
          }
          if (stofree > stokeep)
                  LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link);
  
          if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) {
                  LIST_FOREACH(slab, &freeslabs, us_link)
                          UMA_HASH_REMOVE(&keg->uk_hash, slab);
          }
          dom->ud_free_items -= stofree * keg->uk_ipers;
          dom->ud_free_slabs -= stofree;
          dom->ud_pages -= stofree * keg->uk_ppera;
          KEG_UNLOCK(keg, domain);
  
          LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp)
                  keg_free_slab(keg, slab, keg->uk_ipers);
  }
  
  /*
   * Frees pages from a keg back to the system.  This is done on demand from
   * the pageout daemon.
   *
   * Returns nothing.
   */
  static void
  keg_drain(uma_keg_t keg)
  {
          int i;
  
          if ((keg->uk_flags & UMA_ZONE_NOFREE) != 0)
                  return;
          for (i = 0; i < vm_ndomains; i++)
                  keg_drain_domain(keg, i);
  }
  
  static void
  zone_reclaim(uma_zone_t zone, int waitok, bool drain)
  {
  
          /*
           * Set draining to interlock with zone_dtor() so we can release our
           * locks as we go.  Only dtor() should do a WAITOK call since it
           * is the only call that knows the structure will still be available
           * when it wakes up.
           */
          ZONE_LOCK(zone);
          while (zone->uz_flags & UMA_ZFLAG_RECLAIMING) {
                  if (waitok == M_NOWAIT)
                          goto out;
                  msleep(zone, &ZDOM_GET(zone, 0)->uzd_lock, PVM, "zonedrain",
                      1);
          }
          zone->uz_flags |= UMA_ZFLAG_RECLAIMING;
          ZONE_UNLOCK(zone);
          bucket_cache_reclaim(zone, drain);
  
          /*
           * The DRAINING flag protects us from being freed while
           * we're running.  Normally the uma_rwlock would protect us but we
           * must be able to release and acquire the right lock for each keg.
           */
          if ((zone->uz_flags & UMA_ZFLAG_CACHE) == 0)
                  keg_drain(zone->uz_keg);
          ZONE_LOCK(zone);
          zone->uz_flags &= ~UMA_ZFLAG_RECLAIMING;
          wakeup(zone);
  out:
          ZONE_UNLOCK(zone);
  }
  
  static void
  zone_drain(uma_zone_t zone, void *unused)
  {
  
          zone_reclaim(zone, M_NOWAIT, true);
  }
  
  static void
  zone_trim(uma_zone_t zone, void *unused)
  {
  
          zone_reclaim(zone, M_NOWAIT, false);
  }
  
  /*
   * Allocate a new slab for a keg and inserts it into the partial slab list.
   * The keg should be unlocked on entry.  If the allocation succeeds it will
   * be locked on return.
   *
   * Arguments:
   *      flags   Wait flags for the item initialization routine
   *      aflags  Wait flags for the slab allocation
   *
   * Returns:
   *      The slab that was allocated or NULL if there is no memory and the
   *      caller specified M_NOWAIT.
   */
  static uma_slab_t
  keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int domain, int flags,
      int aflags)
  {
          uma_domain_t dom;
          uma_alloc allocf;
          uma_slab_t slab;
          unsigned long size;
          uint8_t *mem;
          uint8_t sflags;
          int i;
  
          KASSERT(domain >= 0 && domain < vm_ndomains,
              ("keg_alloc_slab: domain %d out of range", domain));
  
          allocf = keg->uk_allocf;
          slab = NULL;
          mem = NULL;
          if (keg->uk_flags & UMA_ZFLAG_OFFPAGE) {
                  uma_hash_slab_t hslab;
                  hslab = zone_alloc_item(slabzone(keg->uk_ipers), NULL,
                      domain, aflags);
                  if (hslab == NULL)
                          goto fail;
                  slab = &hslab->uhs_slab;
          }
  
          /*
           * This reproduces the old vm_zone behavior of zero filling pages the
           * first time they are added to a zone.
           *
           * Malloced items are zeroed in uma_zalloc.
           */
  
          if ((keg->uk_flags & UMA_ZONE_MALLOC) == 0)
                  aflags |= M_ZERO;
          else
                  aflags &= ~M_ZERO;
  
          if (keg->uk_flags & UMA_ZONE_NODUMP)
                  aflags |= M_NODUMP;
  
          /* zone is passed for legacy reasons. */
          size = keg->uk_ppera * PAGE_SIZE;
          mem = allocf(zone, size, domain, &sflags, aflags);
          if (mem == NULL) {
                  if (keg->uk_flags & UMA_ZFLAG_OFFPAGE)
                          zone_free_item(slabzone(keg->uk_ipers),
                              slab_tohashslab(slab), NULL, SKIP_NONE);
                  goto fail;
          }
          uma_total_inc(size);
  
          /* For HASH zones all pages go to the same uma_domain. */
          if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0)
                  domain = 0;
  
          /* Point the slab into the allocated memory */
          if (!(keg->uk_flags & UMA_ZFLAG_OFFPAGE))
                  slab = (uma_slab_t )(mem + keg->uk_pgoff);
          else
                  slab_tohashslab(slab)->uhs_data = mem;
  
          if (keg->uk_flags & UMA_ZFLAG_VTOSLAB)
                  for (i = 0; i < keg->uk_ppera; i++)
                          vsetzoneslab((vm_offset_t)mem + (i * PAGE_SIZE),
                              zone, slab);
  
          slab->us_freecount = keg->uk_ipers;
          slab->us_flags = sflags;
          slab->us_domain = domain;
  
          BIT_FILL(keg->uk_ipers, &slab->us_free);
  #ifdef INVARIANTS
          BIT_ZERO(keg->uk_ipers, slab_dbg_bits(slab, keg));
  #endif
  
          if (keg->uk_init != NULL) {
                  for (i = 0; i < keg->uk_ipers; i++)
                          if (keg->uk_init(slab_item(slab, keg, i),
                              keg->uk_size, flags) != 0)
                                  break;
                  if (i != keg->uk_ipers) {
                          keg_free_slab(keg, slab, i);
                          goto fail;
                  }
          }
          KEG_LOCK(keg, domain);
  
          CTR3(KTR_UMA, "keg_alloc_slab: allocated slab %p for %s(%p)",
              slab, keg->uk_name, keg);
  
          if (keg->uk_flags & UMA_ZFLAG_HASH)
                  UMA_HASH_INSERT(&keg->uk_hash, slab, mem);
  
          /*
           * If we got a slab here it's safe to mark it partially used
           * and return.  We assume that the caller is going to remove
           * at least one item.
           */
          dom = &keg->uk_domain[domain];
          LIST_INSERT_HEAD(&dom->ud_part_slab, slab, us_link);
          dom->ud_pages += keg->uk_ppera;
          dom->ud_free_items += keg->uk_ipers;
  
          return (slab);
  
  fail:
          return (NULL);
  }
  
  /*
   * This function is intended to be used early on in place of page_alloc() so
   * that we may use the boot time page cache to satisfy allocations before
   * the VM is ready.
   */
  static void *
  startup_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
      int wait)
  {
          vm_paddr_t pa;
          vm_page_t m;
          void *mem;
          int pages;
          int i;
  
          pages = howmany(bytes, PAGE_SIZE);
          KASSERT(pages > 0, ("%s can't reserve 0 pages", __func__));
  
          *pflag = UMA_SLAB_BOOT;
          m = vm_page_alloc_contig_domain(NULL, 0, domain,
              malloc2vm_flags(wait) | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED, pages, 
              (vm_paddr_t)0, ~(vm_paddr_t)0, 1, 0, VM_MEMATTR_DEFAULT);
          if (m == NULL)
                  return (NULL);
  
          pa = VM_PAGE_TO_PHYS(m);
          for (i = 0; i < pages; i++, pa += PAGE_SIZE) {
  #if defined(__aarch64__) || defined(__amd64__) || defined(__mips__) || \
      defined(__riscv) || defined(__powerpc64__)
                  if ((wait & M_NODUMP) == 0)
                          dump_add_page(pa);
  #endif
          }
          /* Allocate KVA and indirectly advance bootmem. */
          mem = (void *)pmap_map(&bootmem, m->phys_addr,
              m->phys_addr + (pages * PAGE_SIZE), VM_PROT_READ | VM_PROT_WRITE);
          if ((wait & M_ZERO) != 0)
                  bzero(mem, pages * PAGE_SIZE);
  
          return (mem);
  }
  
  static void
  startup_free(void *mem, vm_size_t bytes)
  {
          vm_offset_t va;
          vm_page_t m;
  
          va = (vm_offset_t)mem;
          m = PHYS_TO_VM_PAGE(pmap_kextract(va));
  
          /*
           * startup_alloc() returns direct-mapped slabs on some platforms.  Avoid
           * unmapping ranges of the direct map.
           */
          if (va >= bootstart && va + bytes <= bootmem)
                  pmap_remove(kernel_pmap, va, va + bytes);
          for (; bytes != 0; bytes -= PAGE_SIZE, m++) {
  #if defined(__aarch64__) || defined(__amd64__) || defined(__mips__) || \
      defined(__riscv) || defined(__powerpc64__)
                  dump_drop_page(VM_PAGE_TO_PHYS(m));
  #endif
                  vm_page_unwire_noq(m);
                  vm_page_free(m);
          }
  }
  
  /*
   * Allocates a number of pages from the system
   *
   * Arguments:
   *      bytes  The number of bytes requested
   *      wait  Shall we wait?
   *
   * Returns:
   *      A pointer to the alloced memory or possibly
   *      NULL if M_NOWAIT is set.
   */
  static void *
  page_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
      int wait)
  {
          void *p;        /* Returned page */
  
          *pflag = UMA_SLAB_KERNEL;
          p = (void *)kmem_malloc_domainset(DOMAINSET_FIXED(domain), bytes, wait);
  
          return (p);
  }
  
  static void *
  pcpu_page_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
      int wait)
  {
          struct pglist alloctail;
          vm_offset_t addr, zkva;
          int cpu, flags;
          vm_page_t p, p_next;
  #ifdef NUMA
          struct pcpu *pc;
  #endif
  
          MPASS(bytes == (mp_maxid + 1) * PAGE_SIZE);
  
          TAILQ_INIT(&alloctail);
          flags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED | VM_ALLOC_NOOBJ |
              malloc2vm_flags(wait);
          *pflag = UMA_SLAB_KERNEL;
          for (cpu = 0; cpu <= mp_maxid; cpu++) {
                  if (CPU_ABSENT(cpu)) {
                          p = vm_page_alloc(NULL, 0, flags);
                  } else {
  #ifndef NUMA
                          p = vm_page_alloc(NULL, 0, flags);
  #else
                          pc = pcpu_find(cpu);
                          if (__predict_false(VM_DOMAIN_EMPTY(pc->pc_domain)))
                                  p = NULL;
                          else
                                  p = vm_page_alloc_domain(NULL, 0,
                                      pc->pc_domain, flags);
                          if (__predict_false(p == NULL))
                                  p = vm_page_alloc(NULL, 0, flags);
  #endif
                  }
                  if (__predict_false(p == NULL))
                          goto fail;
                  TAILQ_INSERT_TAIL(&alloctail, p, listq);
          }
          if ((addr = kva_alloc(bytes)) == 0)
                  goto fail;
          zkva = addr;
          TAILQ_FOREACH(p, &alloctail, listq) {
                  pmap_qenter(zkva, &p, 1);
                  zkva += PAGE_SIZE;
          }
          return ((void*)addr);
  fail:
          TAILQ_FOREACH_SAFE(p, &alloctail, listq, p_next) {
                  vm_page_unwire_noq(p);
                  vm_page_free(p);
          }
          return (NULL);
  }
  
  /*
   * Allocates a number of pages from within an object
   *
   * Arguments:
   *      bytes  The number of bytes requested
   *      wait   Shall we wait?
   *
   * Returns:
   *      A pointer to the alloced memory or possibly
   *      NULL if M_NOWAIT is set.
   */
  static void *
  noobj_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *flags,
      int wait)
  {
          TAILQ_HEAD(, vm_page) alloctail;
          u_long npages;
          vm_offset_t retkva, zkva;
          vm_page_t p, p_next;
          uma_keg_t keg;
  
          TAILQ_INIT(&alloctail);
          keg = zone->uz_keg;
  
          npages = howmany(bytes, PAGE_SIZE);
          while (npages > 0) {
                  p = vm_page_alloc_domain(NULL, 0, domain, VM_ALLOC_INTERRUPT |
                      VM_ALLOC_WIRED | VM_ALLOC_NOOBJ |
                      ((wait & M_WAITOK) != 0 ? VM_ALLOC_WAITOK :
                      VM_ALLOC_NOWAIT));
                  if (p != NULL) {
                          /*
                           * Since the page does not belong to an object, its
                           * listq is unused.
                           */
                          TAILQ_INSERT_TAIL(&alloctail, p, listq);
                          npages--;
                          continue;
                  }
                  /*
                   * Page allocation failed, free intermediate pages and
                   * exit.
                   */
                  TAILQ_FOREACH_SAFE(p, &alloctail, listq, p_next) {
                          vm_page_unwire_noq(p);
                          vm_page_free(p); 
                  }
                  return (NULL);
          }
          *flags = UMA_SLAB_PRIV;
          zkva = keg->uk_kva +
              atomic_fetchadd_long(&keg->uk_offset, round_page(bytes));
          retkva = zkva;
          TAILQ_FOREACH(p, &alloctail, listq) {
                  pmap_qenter(zkva, &p, 1);
                  zkva += PAGE_SIZE;
          }
  
          return ((void *)retkva);
  }
  
  /*
   * Allocate physically contiguous pages.
   */
  static void *
  contig_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
      int wait)
  {
  
          *pflag = UMA_SLAB_KERNEL;
          return ((void *)kmem_alloc_contig_domainset(DOMAINSET_FIXED(domain),
              bytes, wait, 0, ~(vm_paddr_t)0, 1, 0, VM_MEMATTR_DEFAULT));
  }
  
  /*
   * Frees a number of pages to the system
   *
   * Arguments:
   *      mem   A pointer to the memory to be freed
   *      size  The size of the memory being freed
   *      flags The original p->us_flags field
   *
   * Returns:
   *      Nothing
   */
  static void
  page_free(void *mem, vm_size_t size, uint8_t flags)
  {
  
          if ((flags & UMA_SLAB_BOOT) != 0) {
                  startup_free(mem, size);
                  return;
          }
  
          KASSERT((flags & UMA_SLAB_KERNEL) != 0,
              ("UMA: page_free used with invalid flags %x", flags));
  
          kmem_free((vm_offset_t)mem, size);
  }
  
  /*
   * Frees pcpu zone allocations
   *
   * Arguments:
   *      mem   A pointer to the memory to be freed
   *      size  The size of the memory being freed
   *      flags The original p->us_flags field
   *
   * Returns:
   *      Nothing
   */
  static void
  pcpu_page_free(void *mem, vm_size_t size, uint8_t flags)
  {
          vm_offset_t sva, curva;
          vm_paddr_t paddr;
          vm_page_t m;
  
          MPASS(size == (mp_maxid+1)*PAGE_SIZE);
  
          if ((flags & UMA_SLAB_BOOT) != 0) {
                  startup_free(mem, size);
                  return;
          }
  
          sva = (vm_offset_t)mem;
          for (curva = sva; curva < sva + size; curva += PAGE_SIZE) {
                  paddr = pmap_kextract(curva);
                  m = PHYS_TO_VM_PAGE(paddr);
                  vm_page_unwire_noq(m);
                  vm_page_free(m);
          }
          pmap_qremove(sva, size >> PAGE_SHIFT);
          kva_free(sva, size);
  }
  
  /*
   * Zero fill initializer
   *
   * Arguments/Returns follow uma_init specifications
   */
  static int
  zero_init(void *mem, int size, int flags)
  {
          bzero(mem, size);
          return (0);
  }
  
  #ifdef INVARIANTS
  static struct noslabbits *
  slab_dbg_bits(uma_slab_t slab, uma_keg_t keg)
  {
  
          return ((void *)((char *)&slab->us_free + BITSET_SIZE(keg->uk_ipers)));
  }
  #endif
  
  /*
   * Actual size of embedded struct slab (!OFFPAGE).
   */
  static size_t
  slab_sizeof(int nitems)
  {
          size_t s;
  
          s = sizeof(struct uma_slab) + BITSET_SIZE(nitems) * SLAB_BITSETS;
          return (roundup(s, UMA_ALIGN_PTR + 1));
  }
  
  #define UMA_FIXPT_SHIFT 31
  #define UMA_FRAC_FIXPT(n, d)                                            \
          ((uint32_t)(((uint64_t)(n) << UMA_FIXPT_SHIFT) / (d)))
  #define UMA_FIXPT_PCT(f)                                                \
          ((u_int)(((uint64_t)100 * (f)) >> UMA_FIXPT_SHIFT))
  #define UMA_PCT_FIXPT(pct)      UMA_FRAC_FIXPT((pct), 100)
  #define UMA_MIN_EFF     UMA_PCT_FIXPT(100 - UMA_MAX_WASTE)
  
  /*
   * Compute the number of items that will fit in a slab.  If hdr is true, the
   * item count may be limited to provide space in the slab for an inline slab
   * header.  Otherwise, all slab space will be provided for item storage.
   */
  static u_int
  slab_ipers_hdr(u_int size, u_int rsize, u_int slabsize, bool hdr)
  {
          u_int ipers;
          u_int padpi;
  
          /* The padding between items is not needed after the last item. */
          padpi = rsize - size;
  
          if (hdr) {
                  /*
                   * Start with the maximum item count and remove items until
                   * the slab header first alongside the allocatable memory.
                   */
                  for (ipers = MIN(SLAB_MAX_SETSIZE,
                      (slabsize + padpi - slab_sizeof(1)) / rsize);
                      ipers > 0 &&
                      ipers * rsize - padpi + slab_sizeof(ipers) > slabsize;
                      ipers--)
                          continue;
          } else {
                  ipers = MIN((slabsize + padpi) / rsize, SLAB_MAX_SETSIZE);
          }
  
          return (ipers);
  }
  
  struct keg_layout_result {
          u_int format;
          u_int slabsize;
          u_int ipers;
          u_int eff;
  };
  
  static void
  keg_layout_one(uma_keg_t keg, u_int rsize, u_int slabsize, u_int fmt,
      struct keg_layout_result *kl)
  {
          u_int total;
  
          kl->format = fmt;
          kl->slabsize = slabsize;
  
          /* Handle INTERNAL as inline with an extra page. */
          if ((fmt & UMA_ZFLAG_INTERNAL) != 0) {
                  kl->format &= ~UMA_ZFLAG_INTERNAL;
                  kl->slabsize += PAGE_SIZE;
          }
  
          kl->ipers = slab_ipers_hdr(keg->uk_size, rsize, kl->slabsize,
              (fmt & UMA_ZFLAG_OFFPAGE) == 0);
  
          /* Account for memory used by an offpage slab header. */
          total = kl->slabsize;
          if ((fmt & UMA_ZFLAG_OFFPAGE) != 0)
                  total += slabzone(kl->ipers)->uz_keg->uk_rsize;
  
          kl->eff = UMA_FRAC_FIXPT(kl->ipers * rsize, total);
  }
  
  /*
   * Determine the format of a uma keg.  This determines where the slab header
   * will be placed (inline or offpage) and calculates ipers, rsize, and ppera.
   *
   * Arguments
   *      keg  The zone we should initialize
   *
   * Returns
   *      Nothing
   */
  static void
  keg_layout(uma_keg_t keg)
  {
          struct keg_layout_result kl = {}, kl_tmp;
          u_int fmts[2];
          u_int alignsize;
          u_int nfmt;
          u_int pages;
          u_int rsize;
          u_int slabsize;
          u_int i, j;
  
          KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0 ||
              (keg->uk_size <= UMA_PCPU_ALLOC_SIZE &&
               (keg->uk_flags & UMA_ZONE_CACHESPREAD) == 0),
              ("%s: cannot configure for PCPU: keg=%s, size=%u, flags=0x%b",
               __func__, keg->uk_name, keg->uk_size, keg->uk_flags,
               PRINT_UMA_ZFLAGS));
          KASSERT((keg->uk_flags & (UMA_ZFLAG_INTERNAL | UMA_ZONE_VM)) == 0 ||
              (keg->uk_flags & (UMA_ZONE_NOTOUCH | UMA_ZONE_PCPU)) == 0,
              ("%s: incompatible flags 0x%b", __func__, keg->uk_flags,
               PRINT_UMA_ZFLAGS));
  
          alignsize = keg->uk_align + 1;
  
          /*
           * Calculate the size of each allocation (rsize) according to
           * alignment.  If the requested size is smaller than we have
           * allocation bits for we round it up.
           */
          rsize = MAX(keg->uk_size, UMA_SMALLEST_UNIT);
          rsize = roundup2(rsize, alignsize);
  
          if ((keg->uk_flags & UMA_ZONE_CACHESPREAD) != 0) {
                  /*
                   * We want one item to start on every align boundary in a page.
                   * To do this we will span pages.  We will also extend the item
                   * by the size of align if it is an even multiple of align.
                   * Otherwise, it would fall on the same boundary every time.
                   */
                  if ((rsize & alignsize) == 0)
                          rsize += alignsize;
                  slabsize = rsize * (PAGE_SIZE / alignsize);
                  slabsize = MIN(slabsize, rsize * SLAB_MAX_SETSIZE);
                  slabsize = MIN(slabsize, UMA_CACHESPREAD_MAX_SIZE);
                  slabsize = round_page(slabsize);
          } else {
                  /*
                   * Start with a slab size of as many pages as it takes to
                   * represent a single item.  We will try to fit as many
                   * additional items into the slab as possible.
                   */
                  slabsize = round_page(keg->uk_size);
          }
  
          /* Build a list of all of the available formats for this keg. */
          nfmt = 0;
  
          /* Evaluate an inline slab layout. */
          if ((keg->uk_flags & (UMA_ZONE_NOTOUCH | UMA_ZONE_PCPU)) == 0)
                  fmts[nfmt++] = 0;
  
          /* TODO: vm_page-embedded slab. */
  
          /*
           * We can't do OFFPAGE if we're internal or if we've been
           * asked to not go to the VM for buckets.  If we do this we
           * may end up going to the VM for slabs which we do not want
           * to do if we're UMA_ZONE_VM, which clearly forbids it.
           * In those cases, evaluate a pseudo-format called INTERNAL
           * which has an inline slab header and one extra page to
           * guarantee that it fits.
           *
           * Otherwise, see if using an OFFPAGE slab will improve our
           * efficiency.
           */
          if ((keg->uk_flags & (UMA_ZFLAG_INTERNAL | UMA_ZONE_VM)) != 0)
                  fmts[nfmt++] = UMA_ZFLAG_INTERNAL;
          else
                  fmts[nfmt++] = UMA_ZFLAG_OFFPAGE;
  
          /*
           * Choose a slab size and format which satisfy the minimum efficiency.
           * Prefer the smallest slab size that meets the constraints.
           *
           * Start with a minimum slab size, to accommodate CACHESPREAD.  Then,
           * for small items (up to PAGE_SIZE), the iteration increment is one
           * page; and for large items, the increment is one item.
           */
          i = (slabsize + rsize - keg->uk_size) / MAX(PAGE_SIZE, rsize);
          KASSERT(i >= 1, ("keg %s(%p) flags=0x%b slabsize=%u, rsize=%u, i=%u",
              keg->uk_name, keg, keg->uk_flags, PRINT_UMA_ZFLAGS, slabsize,
              rsize, i));
          for ( ; ; i++) {
                  slabsize = (rsize <= PAGE_SIZE) ? ptoa(i) :
                      round_page(rsize * (i - 1) + keg->uk_size);
  
                  for (j = 0; j < nfmt; j++) {
                          /* Only if we have no viable format yet. */
                          if ((fmts[j] & UMA_ZFLAG_INTERNAL) != 0 &&
                              kl.ipers > 0)
                                  continue;
  
                          keg_layout_one(keg, rsize, slabsize, fmts[j], &kl_tmp);
                          if (kl_tmp.eff <= kl.eff)
                                  continue;
  
                          kl = kl_tmp;
  
                          CTR6(KTR_UMA, "keg %s layout: format %#x "
                              "(ipers %u * rsize %u) / slabsize %#x = %u%% eff",
                              keg->uk_name, kl.format, kl.ipers, rsize,
                              kl.slabsize, UMA_FIXPT_PCT(kl.eff));
  
                          /* Stop when we reach the minimum efficiency. */
                          if (kl.eff >= UMA_MIN_EFF)
                                  break;
                  }
  
                  if (kl.eff >= UMA_MIN_EFF || !multipage_slabs ||
                      slabsize >= SLAB_MAX_SETSIZE * rsize ||
                      (keg->uk_flags & (UMA_ZONE_PCPU | UMA_ZONE_CONTIG)) != 0)
                          break;
          }
  
          pages = atop(kl.slabsize);
          if ((keg->uk_flags & UMA_ZONE_PCPU) != 0)
                  pages *= mp_maxid + 1;
  
          keg->uk_rsize = rsize;
          keg->uk_ipers = kl.ipers;
          keg->uk_ppera = pages;
          keg->uk_flags |= kl.format;
  
          /*
           * How do we find the slab header if it is offpage or if not all item
           * start addresses are in the same page?  We could solve the latter
           * case with vaddr alignment, but we don't.
           */
          if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) != 0 ||
              (keg->uk_ipers - 1) * rsize >= PAGE_SIZE) {
                  if ((keg->uk_flags & UMA_ZONE_NOTPAGE) != 0)
                          keg->uk_flags |= UMA_ZFLAG_HASH;
                  else
                          keg->uk_flags |= UMA_ZFLAG_VTOSLAB;
          }
  
          CTR6(KTR_UMA, "%s: keg=%s, flags=%#x, rsize=%u, ipers=%u, ppera=%u",
              __func__, keg->uk_name, keg->uk_flags, rsize, keg->uk_ipers,
              pages);
          KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_MAX_SETSIZE,
              ("%s: keg=%s, flags=0x%b, rsize=%u, ipers=%u, ppera=%u", __func__,
               keg->uk_name, keg->uk_flags, PRINT_UMA_ZFLAGS, rsize,
               keg->uk_ipers, pages));
  }
  
  /*
   * Keg header ctor.  This initializes all fields, locks, etc.  And inserts
   * the keg onto the global keg list.
   *
   * Arguments/Returns follow uma_ctor specifications
   *      udata  Actually uma_kctor_args
   */
  static int
  keg_ctor(void *mem, int size, void *udata, int flags)
  {
          struct uma_kctor_args *arg = udata;
          uma_keg_t keg = mem;
          uma_zone_t zone;
          int i;
  
          bzero(keg, size);
          keg->uk_size = arg->size;
          keg->uk_init = arg->uminit;
          keg->uk_fini = arg->fini;
          keg->uk_align = arg->align;
          keg->uk_reserve = 0;
          keg->uk_flags = arg->flags;
  
          /*
           * We use a global round-robin policy by default.  Zones with
           * UMA_ZONE_FIRSTTOUCH set will use first-touch instead, in which
           * case the iterator is never run.
           */
          keg->uk_dr.dr_policy = DOMAINSET_RR();
          keg->uk_dr.dr_iter = 0;
  
          /*
           * The primary zone is passed to us at keg-creation time.
           */
          zone = arg->zone;
          keg->uk_name = zone->uz_name;
  
          if (arg->flags & UMA_ZONE_ZINIT)
                  keg->uk_init = zero_init;
  
          if (arg->flags & UMA_ZONE_MALLOC)
                  keg->uk_flags |= UMA_ZFLAG_VTOSLAB;
  
  #ifndef SMP
          keg->uk_flags &= ~UMA_ZONE_PCPU;
  #endif
  
          keg_layout(keg);
  
          /*
           * Use a first-touch NUMA policy for kegs that pmap_extract() will
           * work on.  Use round-robin for everything else.
           *
           * Zones may override the default by specifying either.
           */
  #ifdef NUMA
          if ((keg->uk_flags &
              (UMA_ZONE_ROUNDROBIN | UMA_ZFLAG_CACHE | UMA_ZONE_NOTPAGE)) == 0)
                  keg->uk_flags |= UMA_ZONE_FIRSTTOUCH;
          else if ((keg->uk_flags & UMA_ZONE_FIRSTTOUCH) == 0)
                  keg->uk_flags |= UMA_ZONE_ROUNDROBIN;
  #endif
  
          /*
           * If we haven't booted yet we need allocations to go through the
           * startup cache until the vm is ready.
           */
  #ifdef UMA_MD_SMALL_ALLOC
          if (keg->uk_ppera == 1)
                  keg->uk_allocf = uma_small_alloc;
          else
  #endif
          if (booted < BOOT_KVA)
                  keg->uk_allocf = startup_alloc;
          else if (keg->uk_flags & UMA_ZONE_PCPU)
                  keg->uk_allocf = pcpu_page_alloc;
          else if ((keg->uk_flags & UMA_ZONE_CONTIG) != 0 && keg->uk_ppera > 1)
                  keg->uk_allocf = contig_alloc;
          else
                  keg->uk_allocf = page_alloc;
  #ifdef UMA_MD_SMALL_ALLOC
          if (keg->uk_ppera == 1)
                  keg->uk_freef = uma_small_free;
          else
  #endif
          if (keg->uk_flags & UMA_ZONE_PCPU)
                  keg->uk_freef = pcpu_page_free;
          else
                  keg->uk_freef = page_free;
  
          /*
           * Initialize keg's locks.
           */
          for (i = 0; i < vm_ndomains; i++)
                  KEG_LOCK_INIT(keg, i, (arg->flags & UMA_ZONE_MTXCLASS));
  
          /*
           * If we're putting the slab header in the actual page we need to
           * figure out where in each page it goes.  See slab_sizeof
           * definition.
           */
          if (!(keg->uk_flags & UMA_ZFLAG_OFFPAGE)) {
                  size_t shsize;
  
                  shsize = slab_sizeof(keg->uk_ipers);
                  keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - shsize;
                  /*
                   * The only way the following is possible is if with our
                   * UMA_ALIGN_PTR adjustments we are now bigger than
                   * UMA_SLAB_SIZE.  I haven't checked whether this is
                   * mathematically possible for all cases, so we make
                   * sure here anyway.
                   */
                  KASSERT(keg->uk_pgoff + shsize <= PAGE_SIZE * keg->uk_ppera,
                      ("zone %s ipers %d rsize %d size %d slab won't fit",
                      zone->uz_name, keg->uk_ipers, keg->uk_rsize, keg->uk_size));
          }
  
          if (keg->uk_flags & UMA_ZFLAG_HASH)
                  hash_alloc(&keg->uk_hash, 0);
  
          CTR3(KTR_UMA, "keg_ctor %p zone %s(%p)", keg, zone->uz_name, zone);
  
          LIST_INSERT_HEAD(&keg->uk_zones, zone, uz_link);
  
          rw_wlock(&uma_rwlock);
          LIST_INSERT_HEAD(&uma_kegs, keg, uk_link);
          rw_wunlock(&uma_rwlock);
          return (0);
  }
  
  static void
  zone_kva_available(uma_zone_t zone, void *unused)
  {
          uma_keg_t keg;
  
          if ((zone->uz_flags & UMA_ZFLAG_CACHE) != 0)
                  return;
          KEG_GET(zone, keg);
  
          if (keg->uk_allocf == startup_alloc) {
                  /* Switch to the real allocator. */
                  if (keg->uk_flags & UMA_ZONE_PCPU)
                          keg->uk_allocf = pcpu_page_alloc;
                  else if ((keg->uk_flags & UMA_ZONE_CONTIG) != 0 &&
                      keg->uk_ppera > 1)
                          keg->uk_allocf = contig_alloc;
                  else
                          keg->uk_allocf = page_alloc;
          }
  }
  
  static void
  zone_alloc_counters(uma_zone_t zone, void *unused)
  {
  
          zone->uz_allocs = counter_u64_alloc(M_WAITOK);
          zone->uz_frees = counter_u64_alloc(M_WAITOK);
          zone->uz_fails = counter_u64_alloc(M_WAITOK);
          zone->uz_xdomain = counter_u64_alloc(M_WAITOK);
  }
  
  static void
  zone_alloc_sysctl(uma_zone_t zone, void *unused)
  {
          uma_zone_domain_t zdom;
          uma_domain_t dom;
          uma_keg_t keg;
          struct sysctl_oid *oid, *domainoid;
          int domains, i, cnt;
          static const char *nokeg = "cache zone";
          char *c;
  
          /*
           * Make a sysctl safe copy of the zone name by removing
           * any special characters and handling dups by appending
           * an index.
           */
          if (zone->uz_namecnt != 0) {
                  /* Count the number of decimal digits and '_' separator. */
                  for (i = 1, cnt = zone->uz_namecnt; cnt != 0; i++)
                          cnt /= 10;
                  zone->uz_ctlname = malloc(strlen(zone->uz_name) + i + 1,
                      M_UMA, M_WAITOK);
                  sprintf(zone->uz_ctlname, "%s_%d", zone->uz_name,
                      zone->uz_namecnt);
          } else
                  zone->uz_ctlname = strdup(zone->uz_name, M_UMA);
          for (c = zone->uz_ctlname; *c != '\0'; c++)
                  if (strchr("./\\ -", *c) != NULL)
                          *c = '_';
  
          /*
           * Basic parameters at the root.
           */
          zone->uz_oid = SYSCTL_ADD_NODE(NULL, SYSCTL_STATIC_CHILDREN(_vm_uma),
              OID_AUTO, zone->uz_ctlname, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
          oid = zone->uz_oid;
          SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "size", CTLFLAG_RD, &zone->uz_size, 0, "Allocation size");
          SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "flags", CTLFLAG_RD | CTLTYPE_STRING | CTLFLAG_MPSAFE,
              zone, 0, sysctl_handle_uma_zone_flags, "A",
              "Allocator configuration flags");
          SYSCTL_ADD_U16(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "bucket_size", CTLFLAG_RD, &zone->uz_bucket_size, 0,
              "Desired per-cpu cache size");
          SYSCTL_ADD_U16(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "bucket_size_max", CTLFLAG_RD, &zone->uz_bucket_size_max, 0,
              "Maximum allowed per-cpu cache size");
  
          /*
           * keg if present.
           */
          if ((zone->uz_flags & UMA_ZFLAG_HASH) == 0)
                  domains = vm_ndomains;
          else
                  domains = 1;
          oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(zone->uz_oid), OID_AUTO,
              "keg", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
          keg = zone->uz_keg;
          if ((zone->uz_flags & UMA_ZFLAG_CACHE) == 0) {
                  SYSCTL_ADD_CONST_STRING(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "name", CTLFLAG_RD, keg->uk_name, "Keg name");
                  SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "rsize", CTLFLAG_RD, &keg->uk_rsize, 0,
                      "Real object size with alignment");
                  SYSCTL_ADD_U16(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "ppera", CTLFLAG_RD, &keg->uk_ppera, 0,
                      "pages per-slab allocation");
                  SYSCTL_ADD_U16(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "ipers", CTLFLAG_RD, &keg->uk_ipers, 0,
                      "items available per-slab");
                  SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "align", CTLFLAG_RD, &keg->uk_align, 0,
                      "item alignment mask");
                  SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "reserve", CTLFLAG_RD, &keg->uk_reserve, 0,
                      "number of reserved items");
                  SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "efficiency", CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE,
                      keg, 0, sysctl_handle_uma_slab_efficiency, "I",
                      "Slab utilization (100 - internal fragmentation %)");
                  domainoid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(oid),
                      OID_AUTO, "domain", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
                  for (i = 0; i < domains; i++) {
                          dom = &keg->uk_domain[i];
                          oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(domainoid),
                              OID_AUTO, VM_DOMAIN(i)->vmd_name,
                              CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
                          SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                              "pages", CTLFLAG_RD, &dom->ud_pages, 0,
                              "Total pages currently allocated from VM");
                          SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                              "free_items", CTLFLAG_RD, &dom->ud_free_items, 0,
                              "items free in the slab layer");
                  }
          } else
                  SYSCTL_ADD_CONST_STRING(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "name", CTLFLAG_RD, nokeg, "Keg name");
  
          /*
           * Information about zone limits.
           */
          oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(zone->uz_oid), OID_AUTO,
              "limit", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
          SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "items", CTLFLAG_RD | CTLTYPE_U64 | CTLFLAG_MPSAFE,
              zone, 0, sysctl_handle_uma_zone_items, "QU",
              "Current number of allocated items if limit is set");
          SYSCTL_ADD_U64(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "max_items", CTLFLAG_RD, &zone->uz_max_items, 0,
              "Maximum number of allocated and cached items");
          SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "sleepers", CTLFLAG_RD, &zone->uz_sleepers, 0,
              "Number of threads sleeping at limit");
          SYSCTL_ADD_U64(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "sleeps", CTLFLAG_RD, &zone->uz_sleeps, 0,
              "Total zone limit sleeps");
          SYSCTL_ADD_U64(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "bucket_max", CTLFLAG_RD, &zone->uz_bucket_max, 0,
              "Maximum number of items in each domain's bucket cache");
  
          /*
           * Per-domain zone information.
           */
          domainoid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(zone->uz_oid),
              OID_AUTO, "domain", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
          for (i = 0; i < domains; i++) {
                  zdom = ZDOM_GET(zone, i);
                  oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(domainoid),
                      OID_AUTO, VM_DOMAIN(i)->vmd_name,
                      CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
                  SYSCTL_ADD_LONG(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "nitems", CTLFLAG_RD, &zdom->uzd_nitems,
                      "number of items in this domain");
                  SYSCTL_ADD_LONG(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "imax", CTLFLAG_RD, &zdom->uzd_imax,
                      "maximum item count in this period");
                  SYSCTL_ADD_LONG(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "imin", CTLFLAG_RD, &zdom->uzd_imin,
                      "minimum item count in this period");
                  SYSCTL_ADD_LONG(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
                      "wss", CTLFLAG_RD, &zdom->uzd_wss,
                      "Working set size");
          }
  
          /*
           * General statistics.
           */
          oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(zone->uz_oid), OID_AUTO,
              "stats", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
          SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "current", CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE,
              zone, 1, sysctl_handle_uma_zone_cur, "I",
              "Current number of allocated items");
          SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "allocs", CTLFLAG_RD | CTLTYPE_U64 | CTLFLAG_MPSAFE,
              zone, 0, sysctl_handle_uma_zone_allocs, "QU",
              "Total allocation calls");
          SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "frees", CTLFLAG_RD | CTLTYPE_U64 | CTLFLAG_MPSAFE,
              zone, 0, sysctl_handle_uma_zone_frees, "QU",
              "Total free calls");
          SYSCTL_ADD_COUNTER_U64(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "fails", CTLFLAG_RD, &zone->uz_fails,
              "Number of allocation failures");
          SYSCTL_ADD_COUNTER_U64(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
              "xdomain", CTLFLAG_RD, &zone->uz_xdomain,
              "Free calls from the wrong domain");
  }
  
  struct uma_zone_count {
          const char      *name;
          int             count;
  };
  
  static void
  zone_count(uma_zone_t zone, void *arg)
  {
          struct uma_zone_count *cnt;
  
          cnt = arg;
          /*
           * Some zones are rapidly created with identical names and
           * destroyed out of order.  This can lead to gaps in the count.
           * Use one greater than the maximum observed for this name.
           */
          if (strcmp(zone->uz_name, cnt->name) == 0)
                  cnt->count = MAX(cnt->count,
                      zone->uz_namecnt + 1);
  }
  
  static void
  zone_update_caches(uma_zone_t zone)
  {
          int i;
  
          for (i = 0; i <= mp_maxid; i++) {
                  cache_set_uz_size(&zone->uz_cpu[i], zone->uz_size);
                  cache_set_uz_flags(&zone->uz_cpu[i], zone->uz_flags);
          }
  }
  
  /*
   * Zone header ctor.  This initializes all fields, locks, etc.
   *
   * Arguments/Returns follow uma_ctor specifications
   *      udata  Actually uma_zctor_args
   */
  static int
  zone_ctor(void *mem, int size, void *udata, int flags)
  {
          struct uma_zone_count cnt;
          struct uma_zctor_args *arg = udata;
          uma_zone_domain_t zdom;
          uma_zone_t zone = mem;
          uma_zone_t z;
          uma_keg_t keg;
          int i;
  
          bzero(zone, size);
          zone->uz_name = arg->name;
          zone->uz_ctor = arg->ctor;
          zone->uz_dtor = arg->dtor;
          zone->uz_init = NULL;
          zone->uz_fini = NULL;
          zone->uz_sleeps = 0;
          zone->uz_bucket_size = 0;
          zone->uz_bucket_size_min = 0;
          zone->uz_bucket_size_max = BUCKET_MAX;
          zone->uz_flags = (arg->flags & UMA_ZONE_SMR);
          zone->uz_warning = NULL;
          /* The domain structures follow the cpu structures. */
          zone->uz_bucket_max = ULONG_MAX;
          timevalclear(&zone->uz_ratecheck);
  
          /* Count the number of duplicate names. */
          cnt.name = arg->name;
          cnt.count = 0;
          zone_foreach(zone_count, &cnt);
          zone->uz_namecnt = cnt.count;
          ZONE_CROSS_LOCK_INIT(zone);
  
          for (i = 0; i < vm_ndomains; i++) {
                  zdom = ZDOM_GET(zone, i);
                  ZDOM_LOCK_INIT(zone, zdom, (arg->flags & UMA_ZONE_MTXCLASS));
                  STAILQ_INIT(&zdom->uzd_buckets);
          }
  
  #ifdef INVARIANTS
          if (arg->uminit == trash_init && arg->fini == trash_fini)
                  zone->uz_flags |= UMA_ZFLAG_TRASH | UMA_ZFLAG_CTORDTOR;
  #endif
  
          /*
           * This is a pure cache zone, no kegs.
           */
          if (arg->import) {
                  KASSERT((arg->flags & UMA_ZFLAG_CACHE) != 0,
                      ("zone_ctor: Import specified for non-cache zone."));
                  zone->uz_flags = arg->flags;
                  zone->uz_size = arg->size;
                  zone->uz_import = arg->import;
                  zone->uz_release = arg->release;
                  zone->uz_arg = arg->arg;
  #ifdef NUMA
                  /*
                   * Cache zones are round-robin unless a policy is
                   * specified because they may have incompatible
                   * constraints.
                   */
                  if ((zone->uz_flags & UMA_ZONE_FIRSTTOUCH) == 0)
                          zone->uz_flags |= UMA_ZONE_ROUNDROBIN;
  #endif
                  rw_wlock(&uma_rwlock);
                  LIST_INSERT_HEAD(&uma_cachezones, zone, uz_link);
                  rw_wunlock(&uma_rwlock);
                  goto out;
          }
  
          /*
           * Use the regular zone/keg/slab allocator.
           */
          zone->uz_import = zone_import;
          zone->uz_release = zone_release;
          zone->uz_arg = zone; 
          keg = arg->keg;
  
          if (arg->flags & UMA_ZONE_SECONDARY) {
                  KASSERT((zone->uz_flags & UMA_ZONE_SECONDARY) == 0,
                      ("Secondary zone requested UMA_ZFLAG_INTERNAL"));
                  KASSERT(arg->keg != NULL, ("Secondary zone on zero'd keg"));
                  zone->uz_init = arg->uminit;
                  zone->uz_fini = arg->fini;
                  zone->uz_flags |= UMA_ZONE_SECONDARY;
                  rw_wlock(&uma_rwlock);
                  ZONE_LOCK(zone);
                  LIST_FOREACH(z, &keg->uk_zones, uz_link) {
                          if (LIST_NEXT(z, uz_link) == NULL) {
                                  LIST_INSERT_AFTER(z, zone, uz_link);
                                  break;
                          }
                  }
                  ZONE_UNLOCK(zone);
                  rw_wunlock(&uma_rwlock);
          } else if (keg == NULL) {
                  if ((keg = uma_kcreate(zone, arg->size, arg->uminit, arg->fini,
                      arg->align, arg->flags)) == NULL)
                          return (ENOMEM);
          } else {
                  struct uma_kctor_args karg;
                  int error;
  
                  /* We should only be here from uma_startup() */
                  karg.size = arg->size;
                  karg.uminit = arg->uminit;
                  karg.fini = arg->fini;
                  karg.align = arg->align;
                  karg.flags = (arg->flags & ~UMA_ZONE_SMR);
                  karg.zone = zone;
                  error = keg_ctor(arg->keg, sizeof(struct uma_keg), &karg,
                      flags);
                  if (error)
                          return (error);
          }
  
          /* Inherit properties from the keg. */
          zone->uz_keg = keg;
          zone->uz_size = keg->uk_size;
          zone->uz_flags |= (keg->uk_flags &
              (UMA_ZONE_INHERIT | UMA_ZFLAG_INHERIT));
  
  out:
          if (booted >= BOOT_PCPU) {
                  zone_alloc_counters(zone, NULL);
                  if (booted >= BOOT_RUNNING)
                          zone_alloc_sysctl(zone, NULL);
          } else {
                  zone->uz_allocs = EARLY_COUNTER;
                  zone->uz_frees = EARLY_COUNTER;
                  zone->uz_fails = EARLY_COUNTER;
          }
  
          /* Caller requests a private SMR context. */
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0)
                  zone->uz_smr = smr_create(zone->uz_name, 0, 0);
  
          KASSERT((arg->flags & (UMA_ZONE_MAXBUCKET | UMA_ZONE_NOBUCKET)) !=
              (UMA_ZONE_MAXBUCKET | UMA_ZONE_NOBUCKET),
              ("Invalid zone flag combination"));
          if (arg->flags & UMA_ZFLAG_INTERNAL)
                  zone->uz_bucket_size_max = zone->uz_bucket_size = 0;
          if ((arg->flags & UMA_ZONE_MAXBUCKET) != 0)
                  zone->uz_bucket_size = BUCKET_MAX;
          else if ((arg->flags & UMA_ZONE_NOBUCKET) != 0)
                  zone->uz_bucket_size = 0;
          else
                  zone->uz_bucket_size = bucket_select(zone->uz_size);
          zone->uz_bucket_size_min = zone->uz_bucket_size;
          if (zone->uz_dtor != NULL || zone->uz_ctor != NULL)
                  zone->uz_flags |= UMA_ZFLAG_CTORDTOR;
          zone_update_caches(zone);
  
          return (0);
  }
  
  /*
   * Keg header dtor.  This frees all data, destroys locks, frees the hash
   * table and removes the keg from the global list.
   *
   * Arguments/Returns follow uma_dtor specifications
   *      udata  unused
   */
  static void
  keg_dtor(void *arg, int size, void *udata)
  {
          uma_keg_t keg;
          uint32_t free, pages;
          int i;
  
          keg = (uma_keg_t)arg;
          free = pages = 0;
          for (i = 0; i < vm_ndomains; i++) {
                  free += keg->uk_domain[i].ud_free_items;
                  pages += keg->uk_domain[i].ud_pages;
                  KEG_LOCK_FINI(keg, i);
          }
          if (pages != 0)
                  printf("Freed UMA keg (%s) was not empty (%u items). "
                      " Lost %u pages of memory.\n",
                      keg->uk_name ? keg->uk_name : "",
                      pages / keg->uk_ppera * keg->uk_ipers - free, pages);
  
          hash_free(&keg->uk_hash);
  }
  
  /*
   * Zone header dtor.
   *
   * Arguments/Returns follow uma_dtor specifications
   *      udata  unused
   */
  static void
  zone_dtor(void *arg, int size, void *udata)
  {
          uma_zone_t zone;
          uma_keg_t keg;
          int i;
  
          zone = (uma_zone_t)arg;
  
          sysctl_remove_oid(zone->uz_oid, 1, 1);
  
          if (!(zone->uz_flags & UMA_ZFLAG_INTERNAL))
                  cache_drain(zone);
  
          rw_wlock(&uma_rwlock);
          LIST_REMOVE(zone, uz_link);
          rw_wunlock(&uma_rwlock);
          if ((zone->uz_flags & (UMA_ZONE_SECONDARY | UMA_ZFLAG_CACHE)) == 0) {
                  keg = zone->uz_keg;
                  keg->uk_reserve = 0;
          }
          zone_reclaim(zone, M_WAITOK, true);
  
          /*
           * We only destroy kegs from non secondary/non cache zones.
           */
          if ((zone->uz_flags & (UMA_ZONE_SECONDARY | UMA_ZFLAG_CACHE)) == 0) {
                  keg = zone->uz_keg;
                  rw_wlock(&uma_rwlock);
                  LIST_REMOVE(keg, uk_link);
                  rw_wunlock(&uma_rwlock);
                  zone_free_item(kegs, keg, NULL, SKIP_NONE);
          }
          counter_u64_free(zone->uz_allocs);
          counter_u64_free(zone->uz_frees);
          counter_u64_free(zone->uz_fails);
          counter_u64_free(zone->uz_xdomain);
          free(zone->uz_ctlname, M_UMA);
          for (i = 0; i < vm_ndomains; i++)
                  ZDOM_LOCK_FINI(ZDOM_GET(zone, i));
          ZONE_CROSS_LOCK_FINI(zone);
  }
  
  static void
  zone_foreach_unlocked(void (*zfunc)(uma_zone_t, void *arg), void *arg)
  {
          uma_keg_t keg;
          uma_zone_t zone;
  
          LIST_FOREACH(keg, &uma_kegs, uk_link) {
                  LIST_FOREACH(zone, &keg->uk_zones, uz_link)
                          zfunc(zone, arg);
          }
          LIST_FOREACH(zone, &uma_cachezones, uz_link)
                  zfunc(zone, arg);
  }
  
  /*
   * Traverses every zone in the system and calls a callback
   *
   * Arguments:
   *      zfunc  A pointer to a function which accepts a zone
   *              as an argument.
   *
   * Returns:
   *      Nothing
   */
  static void
  zone_foreach(void (*zfunc)(uma_zone_t, void *arg), void *arg)
  {
  
          rw_rlock(&uma_rwlock);
          zone_foreach_unlocked(zfunc, arg);
          rw_runlock(&uma_rwlock);
  }
  
  /*
   * Initialize the kernel memory allocator.  This is done after pages can be
   * allocated but before general KVA is available.
   */
  void
  uma_startup1(vm_offset_t virtual_avail)
  {
          struct uma_zctor_args args;
          size_t ksize, zsize, size;
          uma_keg_t primarykeg;
          uintptr_t m;
          int domain;
          uint8_t pflag;
  
          bootstart = bootmem = virtual_avail;
  
          rw_init(&uma_rwlock, "UMA lock");
          sx_init(&uma_reclaim_lock, "umareclaim");
  
          ksize = sizeof(struct uma_keg) +
              (sizeof(struct uma_domain) * vm_ndomains);
          ksize = roundup(ksize, UMA_SUPER_ALIGN);
          zsize = sizeof(struct uma_zone) +
              (sizeof(struct uma_cache) * (mp_maxid + 1)) +
              (sizeof(struct uma_zone_domain) * vm_ndomains);
          zsize = roundup(zsize, UMA_SUPER_ALIGN);
  
          /* Allocate the zone of zones, zone of kegs, and zone of zones keg. */
          size = (zsize * 2) + ksize;
          for (domain = 0; domain < vm_ndomains; domain++) {
                  m = (uintptr_t)startup_alloc(NULL, size, domain, &pflag,
                      M_NOWAIT | M_ZERO);
                  if (m != 0)
                          break;
          }
          zones = (uma_zone_t)m;
          m += zsize;
          kegs = (uma_zone_t)m;
          m += zsize;
          primarykeg = (uma_keg_t)m;
  
          /* "manually" create the initial zone */
          memset(&args, 0, sizeof(args));
          args.name = "UMA Kegs";
          args.size = ksize;
          args.ctor = keg_ctor;
          args.dtor = keg_dtor;
          args.uminit = zero_init;
          args.fini = NULL;
          args.keg = primarykeg;
          args.align = UMA_SUPER_ALIGN - 1;
          args.flags = UMA_ZFLAG_INTERNAL;
          zone_ctor(kegs, zsize, &args, M_WAITOK);
  
          args.name = "UMA Zones";
          args.size = zsize;
          args.ctor = zone_ctor;
          args.dtor = zone_dtor;
          args.uminit = zero_init;
          args.fini = NULL;
          args.keg = NULL;
          args.align = UMA_SUPER_ALIGN - 1;
          args.flags = UMA_ZFLAG_INTERNAL;
          zone_ctor(zones, zsize, &args, M_WAITOK);
  
          /* Now make zones for slab headers */
          slabzones[0] = uma_zcreate("UMA Slabs 0", SLABZONE0_SIZE,
              NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);
          slabzones[1] = uma_zcreate("UMA Slabs 1", SLABZONE1_SIZE,
              NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);
  
          hashzone = uma_zcreate("UMA Hash",
              sizeof(struct slabhead *) * UMA_HASH_SIZE_INIT,
              NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);
  
          bucket_init();
          smr_init();
  }
  
  #ifndef UMA_MD_SMALL_ALLOC
  extern void vm_radix_reserve_kva(void);
  #endif
  
  /*
   * Advertise the availability of normal kva allocations and switch to
   * the default back-end allocator.  Marks the KVA we consumed on startup
   * as used in the map.
   */
  void
  uma_startup2(void)
  {
  
          if (bootstart != bootmem) {
                  vm_map_lock(kernel_map);
                  (void)vm_map_insert(kernel_map, NULL, 0, bootstart, bootmem,
                      VM_PROT_RW, VM_PROT_RW, MAP_NOFAULT);
                  vm_map_unlock(kernel_map);
          }
  
  #ifndef UMA_MD_SMALL_ALLOC
          /* Set up radix zone to use noobj_alloc. */
          vm_radix_reserve_kva();
  #endif
  
          booted = BOOT_KVA;
          zone_foreach_unlocked(zone_kva_available, NULL);
          bucket_enable();
  }
  
  /*
   * Allocate counters as early as possible so that boot-time allocations are
   * accounted more precisely.
   */
  static void
  uma_startup_pcpu(void *arg __unused)
  {
  
          zone_foreach_unlocked(zone_alloc_counters, NULL);
          booted = BOOT_PCPU;
  }
  SYSINIT(uma_startup_pcpu, SI_SUB_COUNTER, SI_ORDER_ANY, uma_startup_pcpu, NULL);
  
  /*
   * Finish our initialization steps.
   */
  static void
  uma_startup3(void *arg __unused)
  {
  
  #ifdef INVARIANTS
          TUNABLE_INT_FETCH("vm.debug.divisor", &dbg_divisor);
          uma_dbg_cnt = counter_u64_alloc(M_WAITOK);
          uma_skip_cnt = counter_u64_alloc(M_WAITOK);
  #endif
          zone_foreach_unlocked(zone_alloc_sysctl, NULL);
          callout_init(&uma_callout, 1);
          callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
          booted = BOOT_RUNNING;
  
          EVENTHANDLER_REGISTER(shutdown_post_sync, uma_shutdown, NULL,
              EVENTHANDLER_PRI_FIRST);
  }
  SYSINIT(uma_startup3, SI_SUB_VM_CONF, SI_ORDER_SECOND, uma_startup3, NULL);
  
  static void
  uma_shutdown(void)
  {
  
          booted = BOOT_SHUTDOWN;
  }
  
  static uma_keg_t
  uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit, uma_fini fini,
                  int align, uint32_t flags)
  {
          struct uma_kctor_args args;
  
          args.size = size;
          args.uminit = uminit;
          args.fini = fini;
          args.align = (align == UMA_ALIGN_CACHE) ? uma_align_cache : align;
          args.flags = flags;
          args.zone = zone;
          return (zone_alloc_item(kegs, &args, UMA_ANYDOMAIN, M_WAITOK));
  }
  
  /* Public functions */
  /* See uma.h */
  void
  uma_set_align(int align)
  {
  
          if (align != UMA_ALIGN_CACHE)
                  uma_align_cache = align;
  }
  
  /* See uma.h */
  uma_zone_t
  uma_zcreate(const char *name, size_t size, uma_ctor ctor, uma_dtor dtor,
                  uma_init uminit, uma_fini fini, int align, uint32_t flags)
  
  {
          struct uma_zctor_args args;
          uma_zone_t res;
  
          KASSERT(powerof2(align + 1), ("invalid zone alignment %d for \"%s\"",
              align, name));
  
          /* This stuff is essential for the zone ctor */
          memset(&args, 0, sizeof(args));
          args.name = name;
          args.size = size;
          args.ctor = ctor;
          args.dtor = dtor;
          args.uminit = uminit;
          args.fini = fini;
  #ifdef  INVARIANTS
          /*
           * Inject procedures which check for memory use after free if we are
           * allowed to scramble the memory while it is not allocated.  This
           * requires that: UMA is actually able to access the memory, no init
           * or fini procedures, no dependency on the initial value of the
           * memory, and no (legitimate) use of the memory after free.  Note,
           * the ctor and dtor do not need to be empty.
           */
          if ((!(flags & (UMA_ZONE_ZINIT | UMA_ZONE_NOTOUCH |
              UMA_ZONE_NOFREE))) && uminit == NULL && fini == NULL) {
                  args.uminit = trash_init;
                  args.fini = trash_fini;
          }
  #endif
          args.align = align;
          args.flags = flags;
          args.keg = NULL;
  
          sx_slock(&uma_reclaim_lock);
          res = zone_alloc_item(zones, &args, UMA_ANYDOMAIN, M_WAITOK);
          sx_sunlock(&uma_reclaim_lock);
  
          return (res);
  }
  
  /* See uma.h */
  uma_zone_t
  uma_zsecond_create(const char *name, uma_ctor ctor, uma_dtor dtor,
      uma_init zinit, uma_fini zfini, uma_zone_t primary)
  {
          struct uma_zctor_args args;
          uma_keg_t keg;
          uma_zone_t res;
  
          keg = primary->uz_keg;
          memset(&args, 0, sizeof(args));
          args.name = name;
          args.size = keg->uk_size;
          args.ctor = ctor;
          args.dtor = dtor;
          args.uminit = zinit;
          args.fini = zfini;
          args.align = keg->uk_align;
          args.flags = keg->uk_flags | UMA_ZONE_SECONDARY;
          args.keg = keg;
  
          sx_slock(&uma_reclaim_lock);
          res = zone_alloc_item(zones, &args, UMA_ANYDOMAIN, M_WAITOK);
          sx_sunlock(&uma_reclaim_lock);
  
          return (res);
  }
  
  /* See uma.h */
  uma_zone_t
  uma_zcache_create(const char *name, int size, uma_ctor ctor, uma_dtor dtor,
      uma_init zinit, uma_fini zfini, uma_import zimport, uma_release zrelease,
      void *arg, int flags)
  {
          struct uma_zctor_args args;
  
          memset(&args, 0, sizeof(args));
          args.name = name;
          args.size = size;
          args.ctor = ctor;
          args.dtor = dtor;
          args.uminit = zinit;
          args.fini = zfini;
          args.import = zimport;
          args.release = zrelease;
          args.arg = arg;
          args.align = 0;
          args.flags = flags | UMA_ZFLAG_CACHE;
  
          return (zone_alloc_item(zones, &args, UMA_ANYDOMAIN, M_WAITOK));
  }
  
  /* See uma.h */
  void
  uma_zdestroy(uma_zone_t zone)
  {
  
          /*
           * Large slabs are expensive to reclaim, so don't bother doing
           * unnecessary work if we're shutting down.
           */
          if (booted == BOOT_SHUTDOWN &&
              zone->uz_fini == NULL && zone->uz_release == zone_release)
                  return;
          sx_slock(&uma_reclaim_lock);
          zone_free_item(zones, zone, NULL, SKIP_NONE);
          sx_sunlock(&uma_reclaim_lock);
  }
  
  void
  uma_zwait(uma_zone_t zone)
  {
  
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0)
                  uma_zfree_smr(zone, uma_zalloc_smr(zone, M_WAITOK));
          else if ((zone->uz_flags & UMA_ZONE_PCPU) != 0)
                  uma_zfree_pcpu(zone, uma_zalloc_pcpu(zone, M_WAITOK));
          else
                  uma_zfree(zone, uma_zalloc(zone, M_WAITOK));
  }
  
  void *
  uma_zalloc_pcpu_arg(uma_zone_t zone, void *udata, int flags)
  {
          void *item, *pcpu_item;
  #ifdef SMP
          int i;
  
          MPASS(zone->uz_flags & UMA_ZONE_PCPU);
  #endif
          item = uma_zalloc_arg(zone, udata, flags & ~M_ZERO);
          if (item == NULL)
                  return (NULL);
          pcpu_item = zpcpu_base_to_offset(item);
          if (flags & M_ZERO) {
  #ifdef SMP
                  for (i = 0; i <= mp_maxid; i++)
                          bzero(zpcpu_get_cpu(pcpu_item, i), zone->uz_size);
  #else
                  bzero(item, zone->uz_size);
  #endif
          }
          return (pcpu_item);
  }
  
  /*
   * A stub while both regular and pcpu cases are identical.
   */
  void
  uma_zfree_pcpu_arg(uma_zone_t zone, void *pcpu_item, void *udata)
  {
          void *item;
  
  #ifdef SMP
          MPASS(zone->uz_flags & UMA_ZONE_PCPU);
  #endif
          item = zpcpu_offset_to_base(pcpu_item);
          uma_zfree_arg(zone, item, udata);
  }
  
  static inline void *
  item_ctor(uma_zone_t zone, int uz_flags, int size, void *udata, int flags,
      void *item)
  {
  #ifdef INVARIANTS
          bool skipdbg;
  
          skipdbg = uma_dbg_zskip(zone, item);
          if (!skipdbg && (zone->uz_flags & UMA_ZFLAG_TRASH) != 0 &&
              zone->uz_ctor != trash_ctor)
                  trash_ctor(item, size, udata, flags);
  #endif
          /* Check flags before loading ctor pointer. */
          if (__predict_false((uz_flags & UMA_ZFLAG_CTORDTOR) != 0) &&
              __predict_false(zone->uz_ctor != NULL) &&
              zone->uz_ctor(item, size, udata, flags) != 0) {
                  counter_u64_add(zone->uz_fails, 1);
                  zone_free_item(zone, item, udata, SKIP_DTOR | SKIP_CNT);
                  return (NULL);
          }
  #ifdef INVARIANTS
          if (!skipdbg)
                  uma_dbg_alloc(zone, NULL, item);
  #endif
          if (__predict_false(flags & M_ZERO))
                  return (memset(item, 0, size));
  
          return (item);
  }
  
  static inline void
  item_dtor(uma_zone_t zone, void *item, int size, void *udata,
      enum zfreeskip skip)
  {
  #ifdef INVARIANTS
          bool skipdbg;
  
          skipdbg = uma_dbg_zskip(zone, item);
          if (skip == SKIP_NONE && !skipdbg) {
                  if ((zone->uz_flags & UMA_ZONE_MALLOC) != 0)
                          uma_dbg_free(zone, udata, item);
                  else
                          uma_dbg_free(zone, NULL, item);
          }
  #endif
          if (__predict_true(skip < SKIP_DTOR)) {
                  if (zone->uz_dtor != NULL)
                          zone->uz_dtor(item, size, udata);
  #ifdef INVARIANTS
                  if (!skipdbg && (zone->uz_flags & UMA_ZFLAG_TRASH) != 0 &&
                      zone->uz_dtor != trash_dtor)
                          trash_dtor(item, size, udata);
  #endif
          }
  }
  
  #ifdef NUMA
  static int
  item_domain(void *item)
  {
          int domain;
  
          domain = vm_phys_domain(vtophys(item));
          KASSERT(domain >= 0 && domain < vm_ndomains,
              ("%s: unknown domain for item %p", __func__, item));
          return (domain);
  }
  #endif
  
  #if defined(INVARIANTS) || defined(DEBUG_MEMGUARD) || defined(WITNESS)
  #define UMA_ZALLOC_DEBUG
  static int
  uma_zalloc_debug(uma_zone_t zone, void **itemp, void *udata, int flags)
  {
          int error;
  
          error = 0;
  #ifdef WITNESS
          if (flags & M_WAITOK) {
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "uma_zalloc_debug: zone \"%s\"", zone->uz_name);
          }
  #endif
  
  #ifdef INVARIANTS
          KASSERT((flags & M_EXEC) == 0,
              ("uma_zalloc_debug: called with M_EXEC"));
          KASSERT(curthread->td_critnest == 0 || SCHEDULER_STOPPED(),
              ("uma_zalloc_debug: called within spinlock or critical section"));
          KASSERT((zone->uz_flags & UMA_ZONE_PCPU) == 0 || (flags & M_ZERO) == 0,
              ("uma_zalloc_debug: allocating from a pcpu zone with M_ZERO"));
  #endif
  
  #ifdef DEBUG_MEMGUARD
          if ((zone->uz_flags & UMA_ZONE_SMR) == 0 && memguard_cmp_zone(zone)) {
                  void *item;
                  item = memguard_alloc(zone->uz_size, flags);
                  if (item != NULL) {
                          error = EJUSTRETURN;
                          if (zone->uz_init != NULL &&
                              zone->uz_init(item, zone->uz_size, flags) != 0) {
                                  *itemp = NULL;
                                  return (error);
                          }
                          if (zone->uz_ctor != NULL &&
                              zone->uz_ctor(item, zone->uz_size, udata,
                              flags) != 0) {
                                  counter_u64_add(zone->uz_fails, 1);
                                  zone->uz_fini(item, zone->uz_size);
                                  *itemp = NULL;
                                  return (error);
                          }
                          *itemp = item;
                          return (error);
                  }
                  /* This is unfortunate but should not be fatal. */
          }
  #endif
          return (error);
  }
  
  static int
  uma_zfree_debug(uma_zone_t zone, void *item, void *udata)
  {
          KASSERT(curthread->td_critnest == 0 || SCHEDULER_STOPPED(),
              ("uma_zfree_debug: called with spinlock or critical section held"));
  
  #ifdef DEBUG_MEMGUARD
          if ((zone->uz_flags & UMA_ZONE_SMR) == 0 && is_memguard_addr(item)) {
                  if (zone->uz_dtor != NULL)
                          zone->uz_dtor(item, zone->uz_size, udata);
                  if (zone->uz_fini != NULL)
                          zone->uz_fini(item, zone->uz_size);
                  memguard_free(item);
                  return (EJUSTRETURN);
          }
  #endif
          return (0);
  }
  #endif
  
  static inline void *
  cache_alloc_item(uma_zone_t zone, uma_cache_t cache, uma_cache_bucket_t bucket,
      void *udata, int flags)
  {
          void *item;
          int size, uz_flags;
  
          item = cache_bucket_pop(cache, bucket);
          size = cache_uz_size(cache);
          uz_flags = cache_uz_flags(cache);
          critical_exit();
          return (item_ctor(zone, uz_flags, size, udata, flags, item));
  }
  
  static __noinline void *
  cache_alloc_retry(uma_zone_t zone, uma_cache_t cache, void *udata, int flags)
  {
          uma_cache_bucket_t bucket;
          int domain;
  
          while (cache_alloc(zone, cache, udata, flags)) {
                  cache = &zone->uz_cpu[curcpu];
                  bucket = &cache->uc_allocbucket;
                  if (__predict_false(bucket->ucb_cnt == 0))
                          continue;
                  return (cache_alloc_item(zone, cache, bucket, udata, flags));
          }
          critical_exit();
  
          /*
           * We can not get a bucket so try to return a single item.
           */
          if (zone->uz_flags & UMA_ZONE_FIRSTTOUCH)
                  domain = PCPU_GET(domain);
          else
                  domain = UMA_ANYDOMAIN;
          return (zone_alloc_item(zone, udata, domain, flags));
  }
  
  /* See uma.h */
  void *
  uma_zalloc_smr(uma_zone_t zone, int flags)
  {
          uma_cache_bucket_t bucket;
          uma_cache_t cache;
  
  #ifdef UMA_ZALLOC_DEBUG
          void *item;
  
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) != 0,
              ("uma_zalloc_arg: called with non-SMR zone."));
          if (uma_zalloc_debug(zone, &item, NULL, flags) == EJUSTRETURN)
                  return (item);
  #endif
  
          critical_enter();
          cache = &zone->uz_cpu[curcpu];
          bucket = &cache->uc_allocbucket;
          if (__predict_false(bucket->ucb_cnt == 0))
                  return (cache_alloc_retry(zone, cache, NULL, flags));
          return (cache_alloc_item(zone, cache, bucket, NULL, flags));
  }
  
  /* See uma.h */
  void *
  uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
  {
          uma_cache_bucket_t bucket;
          uma_cache_t cache;
  
          /* Enable entropy collection for RANDOM_ENABLE_UMA kernel option */
          random_harvest_fast_uma(&zone, sizeof(zone), RANDOM_UMA);
  
          /* This is the fast path allocation */
          CTR3(KTR_UMA, "uma_zalloc_arg zone %s(%p) flags %d", zone->uz_name,
              zone, flags);
  
  #ifdef UMA_ZALLOC_DEBUG
          void *item;
  
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) == 0,
              ("uma_zalloc_arg: called with SMR zone."));
          if (uma_zalloc_debug(zone, &item, udata, flags) == EJUSTRETURN)
                  return (item);
  #endif
  
          /*
           * If possible, allocate from the per-CPU cache.  There are two
           * requirements for safe access to the per-CPU cache: (1) the thread
           * accessing the cache must not be preempted or yield during access,
           * and (2) the thread must not migrate CPUs without switching which
           * cache it accesses.  We rely on a critical section to prevent
           * preemption and migration.  We release the critical section in
           * order to acquire the zone mutex if we are unable to allocate from
           * the current cache; when we re-acquire the critical section, we
           * must detect and handle migration if it has occurred.
           */
          critical_enter();
          cache = &zone->uz_cpu[curcpu];
          bucket = &cache->uc_allocbucket;
          if (__predict_false(bucket->ucb_cnt == 0))
                  return (cache_alloc_retry(zone, cache, udata, flags));
          return (cache_alloc_item(zone, cache, bucket, udata, flags));
  }
  
  /*
   * Replenish an alloc bucket and possibly restore an old one.  Called in
   * a critical section.  Returns in a critical section.
   *
   * A false return value indicates an allocation failure.
   * A true return value indicates success and the caller should retry.
   */
  static __noinline bool
  cache_alloc(uma_zone_t zone, uma_cache_t cache, void *udata, int flags)
  {
          uma_bucket_t bucket;
          int curdomain, domain;
          bool new;
  
          CRITICAL_ASSERT(curthread);
  
          /*
           * If we have run out of items in our alloc bucket see
           * if we can switch with the free bucket.
           *
           * SMR Zones can't re-use the free bucket until the sequence has
           * expired.
           */
          if ((cache_uz_flags(cache) & UMA_ZONE_SMR) == 0 &&
              cache->uc_freebucket.ucb_cnt != 0) {
                  cache_bucket_swap(&cache->uc_freebucket,
                      &cache->uc_allocbucket);
                  return (true);
          }
  
          /*
           * Discard any empty allocation bucket while we hold no locks.
           */
          bucket = cache_bucket_unload_alloc(cache);
          critical_exit();
  
          if (bucket != NULL) {
                  KASSERT(bucket->ub_cnt == 0,
                      ("cache_alloc: Entered with non-empty alloc bucket."));
                  bucket_free(zone, bucket, udata);
          }
  
          /*
           * Attempt to retrieve the item from the per-CPU cache has failed, so
           * we must go back to the zone.  This requires the zdom lock, so we
           * must drop the critical section, then re-acquire it when we go back
           * to the cache.  Since the critical section is released, we may be
           * preempted or migrate.  As such, make sure not to maintain any
           * thread-local state specific to the cache from prior to releasing
           * the critical section.
           */
          domain = PCPU_GET(domain);
          if ((cache_uz_flags(cache) & UMA_ZONE_ROUNDROBIN) != 0 ||
              VM_DOMAIN_EMPTY(domain))
                  domain = zone_domain_highest(zone, domain);
          bucket = cache_fetch_bucket(zone, cache, domain);
          if (bucket == NULL && zone->uz_bucket_size != 0 && !bucketdisable) {
                  bucket = zone_alloc_bucket(zone, udata, domain, flags);
                  new = true;
          } else {
                  new = false;
          }
  
          CTR3(KTR_UMA, "uma_zalloc: zone %s(%p) bucket zone returned %p",
              zone->uz_name, zone, bucket);
          if (bucket == NULL) {
                  critical_enter();
                  return (false);
          }
  
          /*
           * See if we lost the race or were migrated.  Cache the
           * initialized bucket to make this less likely or claim
           * the memory directly.
           */
          critical_enter();
          cache = &zone->uz_cpu[curcpu];
          if (cache->uc_allocbucket.ucb_bucket == NULL &&
              ((cache_uz_flags(cache) & UMA_ZONE_FIRSTTOUCH) == 0 ||
              (curdomain = PCPU_GET(domain)) == domain ||
              VM_DOMAIN_EMPTY(curdomain))) {
                  if (new)
                          atomic_add_long(&ZDOM_GET(zone, domain)->uzd_imax,
                              bucket->ub_cnt);
                  cache_bucket_load_alloc(cache, bucket);
                  return (true);
          }
  
          /*
           * We lost the race, release this bucket and start over.
           */
          critical_exit();
          zone_put_bucket(zone, domain, bucket, udata, false);
          critical_enter();
  
          return (true);
  }
  
  void *
  uma_zalloc_domain(uma_zone_t zone, void *udata, int domain, int flags)
  {
  #ifdef NUMA
          uma_bucket_t bucket;
          uma_zone_domain_t zdom;
          void *item;
  #endif
  
          /* Enable entropy collection for RANDOM_ENABLE_UMA kernel option */
          random_harvest_fast_uma(&zone, sizeof(zone), RANDOM_UMA);
  
          /* This is the fast path allocation */
          CTR4(KTR_UMA, "uma_zalloc_domain zone %s(%p) domain %d flags %d",
              zone->uz_name, zone, domain, flags);
  
          if (flags & M_WAITOK) {
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "uma_zalloc_domain: zone \"%s\"", zone->uz_name);
          }
          KASSERT(curthread->td_critnest == 0 || SCHEDULER_STOPPED(),
              ("uma_zalloc_domain: called with spinlock or critical section held"));
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) == 0,
              ("uma_zalloc_domain: called with SMR zone."));
  #ifdef NUMA
          KASSERT((zone->uz_flags & UMA_ZONE_FIRSTTOUCH) != 0,
              ("uma_zalloc_domain: called with non-FIRSTTOUCH zone."));
  
          if (vm_ndomains == 1)
                  return (uma_zalloc_arg(zone, udata, flags));
  
          /*
           * Try to allocate from the bucket cache before falling back to the keg.
           * We could try harder and attempt to allocate from per-CPU caches or
           * the per-domain cross-domain buckets, but the complexity is probably
           * not worth it.  It is more important that frees of previous
           * cross-domain allocations do not blow up the cache.
           */
          zdom = zone_domain_lock(zone, domain);
          if ((bucket = zone_fetch_bucket(zone, zdom, false)) != NULL) {
                  item = bucket->ub_bucket[bucket->ub_cnt - 1];
  #ifdef INVARIANTS
                  bucket->ub_bucket[bucket->ub_cnt - 1] = NULL;
  #endif
                  bucket->ub_cnt--;
                  zone_put_bucket(zone, domain, bucket, udata, true);
                  item = item_ctor(zone, zone->uz_flags, zone->uz_size, udata,
                      flags, item);
                  if (item != NULL) {
                          KASSERT(item_domain(item) == domain,
                              ("%s: bucket cache item %p from wrong domain",
                              __func__, item));
                          counter_u64_add(zone->uz_allocs, 1);
                  }
                  return (item);
          }
          ZDOM_UNLOCK(zdom);
          return (zone_alloc_item(zone, udata, domain, flags));
  #else
          return (uma_zalloc_arg(zone, udata, flags));
  #endif
  }
  
  /*
   * Find a slab with some space.  Prefer slabs that are partially used over those
   * that are totally full.  This helps to reduce fragmentation.
   *
   * If 'rr' is 1, search all domains starting from 'domain'.  Otherwise check
   * only 'domain'.
   */
  static uma_slab_t
  keg_first_slab(uma_keg_t keg, int domain, bool rr)
  {
          uma_domain_t dom;
          uma_slab_t slab;
          int start;
  
          KASSERT(domain >= 0 && domain < vm_ndomains,
              ("keg_first_slab: domain %d out of range", domain));
          KEG_LOCK_ASSERT(keg, domain);
  
          slab = NULL;
          start = domain;
          do {
                  dom = &keg->uk_domain[domain];
                  if ((slab = LIST_FIRST(&dom->ud_part_slab)) != NULL)
                          return (slab);
                  if ((slab = LIST_FIRST(&dom->ud_free_slab)) != NULL) {
                          LIST_REMOVE(slab, us_link);
                          dom->ud_free_slabs--;
                          LIST_INSERT_HEAD(&dom->ud_part_slab, slab, us_link);
                          return (slab);
                  }
                  if (rr)
                          domain = (domain + 1) % vm_ndomains;
          } while (domain != start);
  
          return (NULL);
  }
  
  /*
   * Fetch an existing slab from a free or partial list.  Returns with the
   * keg domain lock held if a slab was found or unlocked if not.
   */
  static uma_slab_t
  keg_fetch_free_slab(uma_keg_t keg, int domain, bool rr, int flags)
  {
          uma_slab_t slab;
          uint32_t reserve;
  
          /* HASH has a single free list. */
          if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0)
                  domain = 0;
  
          KEG_LOCK(keg, domain);
          reserve = (flags & M_USE_RESERVE) != 0 ? 0 : keg->uk_reserve;
          if (keg->uk_domain[domain].ud_free_items <= reserve ||
              (slab = keg_first_slab(keg, domain, rr)) == NULL) {
                  KEG_UNLOCK(keg, domain);
                  return (NULL);
          }
          return (slab);
  }
  
  static uma_slab_t
  keg_fetch_slab(uma_keg_t keg, uma_zone_t zone, int rdomain, const int flags)
  {
          struct vm_domainset_iter di;
          uma_slab_t slab;
          int aflags, domain;
          bool rr;
  
  restart:
          /*
           * Use the keg's policy if upper layers haven't already specified a
           * domain (as happens with first-touch zones).
           *
           * To avoid races we run the iterator with the keg lock held, but that
           * means that we cannot allow the vm_domainset layer to sleep.  Thus,
           * clear M_WAITOK and handle low memory conditions locally.
           */
          rr = rdomain == UMA_ANYDOMAIN;
          if (rr) {
                  aflags = (flags & ~M_WAITOK) | M_NOWAIT;
                  vm_domainset_iter_policy_ref_init(&di, &keg->uk_dr, &domain,
                      &aflags);
          } else {
                  aflags = flags;
                  domain = rdomain;
          }
  
          for (;;) {
                  slab = keg_fetch_free_slab(keg, domain, rr, flags);
                  if (slab != NULL)
                          return (slab);
  
                  /*
                   * M_NOVM means don't ask at all!
                   */
                  if (flags & M_NOVM)
                          break;
  
                  slab = keg_alloc_slab(keg, zone, domain, flags, aflags);
                  if (slab != NULL)
                          return (slab);
                  if (!rr && (flags & M_WAITOK) == 0)
                          break;
                  if (rr && vm_domainset_iter_policy(&di, &domain) != 0) {
                          if ((flags & M_WAITOK) != 0) {
                                  vm_wait_doms(&keg->uk_dr.dr_policy->ds_mask, 0);
                                  goto restart;
                          }
                          break;
                  }
          }
  
          /*
           * We might not have been able to get a slab but another cpu
           * could have while we were unlocked.  Check again before we
           * fail.
           */
          if ((slab = keg_fetch_free_slab(keg, domain, rr, flags)) != NULL)
                  return (slab);
  
          return (NULL);
  }
  
  static void *
  slab_alloc_item(uma_keg_t keg, uma_slab_t slab)
  {
          uma_domain_t dom;
          void *item;
          int freei;
  
          KEG_LOCK_ASSERT(keg, slab->us_domain);
  
          dom = &keg->uk_domain[slab->us_domain];
          freei = BIT_FFS(keg->uk_ipers, &slab->us_free) - 1;
          BIT_CLR(keg->uk_ipers, freei, &slab->us_free);
          item = slab_item(slab, keg, freei);
          slab->us_freecount--;
          dom->ud_free_items--;
  
          /*
           * Move this slab to the full list.  It must be on the partial list, so
           * we do not need to update the free slab count.  In particular,
           * keg_fetch_slab() always returns slabs on the partial list.
           */
          if (slab->us_freecount == 0) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&dom->ud_full_slab, slab, us_link);
          }
  
          return (item);
  }
  
  static int
  zone_import(void *arg, void **bucket, int max, int domain, int flags)
  {
          uma_domain_t dom;
          uma_zone_t zone;
          uma_slab_t slab;
          uma_keg_t keg;
  #ifdef NUMA
          int stripe;
  #endif
          int i;
  
          zone = arg;
          slab = NULL;
          keg = zone->uz_keg;
          /* Try to keep the buckets totally full */
          for (i = 0; i < max; ) {
                  if ((slab = keg_fetch_slab(keg, zone, domain, flags)) == NULL)
                          break;
  #ifdef NUMA
                  stripe = howmany(max, vm_ndomains);
  #endif
                  dom = &keg->uk_domain[slab->us_domain];
                  do {
                          bucket[i++] = slab_alloc_item(keg, slab);
                          if (dom->ud_free_items <= keg->uk_reserve) {
                                  /*
                                   * Avoid depleting the reserve after a
                                   * successful item allocation, even if
                                   * M_USE_RESERVE is specified.
                                   */
                                  KEG_UNLOCK(keg, slab->us_domain);
                                  goto out;
                          }
  #ifdef NUMA
                          /*
                           * If the zone is striped we pick a new slab for every
                           * N allocations.  Eliminating this conditional will
                           * instead pick a new domain for each bucket rather
                           * than stripe within each bucket.  The current option
                           * produces more fragmentation and requires more cpu
                           * time but yields better distribution.
                           */
                          if ((zone->uz_flags & UMA_ZONE_ROUNDROBIN) != 0 &&
                              vm_ndomains > 1 && --stripe == 0)
                                  break;
  #endif
                  } while (slab->us_freecount != 0 && i < max);
                  KEG_UNLOCK(keg, slab->us_domain);
  
                  /* Don't block if we allocated any successfully. */
                  flags &= ~M_WAITOK;
                  flags |= M_NOWAIT;
          }
  out:
          return i;
  }
  
  static int
  zone_alloc_limit_hard(uma_zone_t zone, int count, int flags)
  {
          uint64_t old, new, total, max;
  
          /*
           * The hard case.  We're going to sleep because there were existing
           * sleepers or because we ran out of items.  This routine enforces
           * fairness by keeping fifo order.
           *
           * First release our ill gotten gains and make some noise.
           */
          for (;;) {
                  zone_free_limit(zone, count);
                  zone_log_warning(zone);
                  zone_maxaction(zone);
                  if (flags & M_NOWAIT)
                          return (0);
  
                  /*
                   * We need to allocate an item or set ourself as a sleeper
                   * while the sleepq lock is held to avoid wakeup races.  This
                   * is essentially a home rolled semaphore.
                   */
                  sleepq_lock(&zone->uz_max_items);
                  old = zone->uz_items;
                  do {
                          MPASS(UZ_ITEMS_SLEEPERS(old) < UZ_ITEMS_SLEEPERS_MAX);
                          /* Cache the max since we will evaluate twice. */
                          max = zone->uz_max_items;
                          if (UZ_ITEMS_SLEEPERS(old) != 0 ||
                              UZ_ITEMS_COUNT(old) >= max)
                                  new = old + UZ_ITEMS_SLEEPER;
                          else
                                  new = old + MIN(count, max - old);
                  } while (atomic_fcmpset_64(&zone->uz_items, &old, new) == 0);
  
                  /* We may have successfully allocated under the sleepq lock. */
                  if (UZ_ITEMS_SLEEPERS(new) == 0) {
                          sleepq_release(&zone->uz_max_items);
                          return (new - old);
                  }
  
                  /*
                   * This is in a different cacheline from uz_items so that we
                   * don't constantly invalidate the fastpath cacheline when we
                   * adjust item counts.  This could be limited to toggling on
                   * transitions.
                   */
                  atomic_add_32(&zone->uz_sleepers, 1);
                  atomic_add_64(&zone->uz_sleeps, 1);
  
                  /*
                   * We have added ourselves as a sleeper.  The sleepq lock
                   * protects us from wakeup races.  Sleep now and then retry.
                   */
                  sleepq_add(&zone->uz_max_items, NULL, "zonelimit", 0, 0);
                  sleepq_wait(&zone->uz_max_items, PVM);
  
                  /*
                   * After wakeup, remove ourselves as a sleeper and try
                   * again.  We no longer have the sleepq lock for protection.
                   *
                   * Subract ourselves as a sleeper while attempting to add
                   * our count.
                   */
                  atomic_subtract_32(&zone->uz_sleepers, 1);
                  old = atomic_fetchadd_64(&zone->uz_items,
                      -(UZ_ITEMS_SLEEPER - count));
                  /* We're no longer a sleeper. */
                  old -= UZ_ITEMS_SLEEPER;
  
                  /*
                   * If we're still at the limit, restart.  Notably do not
                   * block on other sleepers.  Cache the max value to protect
                   * against changes via sysctl.
                   */
                  total = UZ_ITEMS_COUNT(old);
                  max = zone->uz_max_items;
                  if (total >= max)
                          continue;
                  /* Truncate if necessary, otherwise wake other sleepers. */
                  if (total + count > max) {
                          zone_free_limit(zone, total + count - max);
                          count = max - total;
                  } else if (total + count < max && UZ_ITEMS_SLEEPERS(old) != 0)
                          wakeup_one(&zone->uz_max_items);
  
                  return (count);
          }
  }
  
  /*
   * Allocate 'count' items from our max_items limit.  Returns the number
   * available.  If M_NOWAIT is not specified it will sleep until at least
   * one item can be allocated.
   */
  static int
  zone_alloc_limit(uma_zone_t zone, int count, int flags)
  {
          uint64_t old;
          uint64_t max;
  
          max = zone->uz_max_items;
          MPASS(max > 0);
  
          /*
           * We expect normal allocations to succeed with a simple
           * fetchadd.
           */
          old = atomic_fetchadd_64(&zone->uz_items, count);
          if (__predict_true(old + count <= max))
                  return (count);
  
          /*
           * If we had some items and no sleepers just return the
           * truncated value.  We have to release the excess space
           * though because that may wake sleepers who weren't woken
           * because we were temporarily over the limit.
           */
          if (old < max) {
                  zone_free_limit(zone, (old + count) - max);
                  return (max - old);
          }
          return (zone_alloc_limit_hard(zone, count, flags));
  }
  
  /*
   * Free a number of items back to the limit.
   */
  static void
  zone_free_limit(uma_zone_t zone, int count)
  {
          uint64_t old;
  
          MPASS(count > 0);
  
          /*
           * In the common case we either have no sleepers or
           * are still over the limit and can just return.
           */
          old = atomic_fetchadd_64(&zone->uz_items, -count);
          if (__predict_true(UZ_ITEMS_SLEEPERS(old) == 0 ||
             UZ_ITEMS_COUNT(old) - count >= zone->uz_max_items))
                  return;
  
          /*
           * Moderate the rate of wakeups.  Sleepers will continue
           * to generate wakeups if necessary.
           */
          wakeup_one(&zone->uz_max_items);
  }
  
  static uma_bucket_t
  zone_alloc_bucket(uma_zone_t zone, void *udata, int domain, int flags)
  {
          uma_bucket_t bucket;
          int maxbucket, cnt;
  
          CTR3(KTR_UMA, "zone_alloc_bucket zone %s(%p) domain %d", zone->uz_name,
              zone, domain);
  
          /* Avoid allocs targeting empty domains. */
          if (domain != UMA_ANYDOMAIN && VM_DOMAIN_EMPTY(domain))
                  domain = UMA_ANYDOMAIN;
          else if ((zone->uz_flags & UMA_ZONE_ROUNDROBIN) != 0)
                  domain = UMA_ANYDOMAIN;
  
          if (zone->uz_max_items > 0)
                  maxbucket = zone_alloc_limit(zone, zone->uz_bucket_size,
                      M_NOWAIT);
          else
                  maxbucket = zone->uz_bucket_size;
          if (maxbucket == 0)
                  return (false);
  
          /* Don't wait for buckets, preserve caller's NOVM setting. */
          bucket = bucket_alloc(zone, udata, M_NOWAIT | (flags & M_NOVM));
          if (bucket == NULL) {
                  cnt = 0;
                  goto out;
          }
  
          bucket->ub_cnt = zone->uz_import(zone->uz_arg, bucket->ub_bucket,
              MIN(maxbucket, bucket->ub_entries), domain, flags);
  
          /*
           * Initialize the memory if necessary.
           */
          if (bucket->ub_cnt != 0 && zone->uz_init != NULL) {
                  int i;
  
                  for (i = 0; i < bucket->ub_cnt; i++)
                          if (zone->uz_init(bucket->ub_bucket[i], zone->uz_size,
                              flags) != 0)
                                  break;
                  /*
                   * If we couldn't initialize the whole bucket, put the
                   * rest back onto the freelist.
                   */
                  if (i != bucket->ub_cnt) {
                          zone->uz_release(zone->uz_arg, &bucket->ub_bucket[i],
                              bucket->ub_cnt - i);
  #ifdef INVARIANTS
                          bzero(&bucket->ub_bucket[i],
                              sizeof(void *) * (bucket->ub_cnt - i));
  #endif
                          bucket->ub_cnt = i;
                  }
          }
  
          cnt = bucket->ub_cnt;
          if (bucket->ub_cnt == 0) {
                  bucket_free(zone, bucket, udata);
                  counter_u64_add(zone->uz_fails, 1);
                  bucket = NULL;
          }
  out:
          if (zone->uz_max_items > 0 && cnt < maxbucket)
                  zone_free_limit(zone, maxbucket - cnt);
  
          return (bucket);
  }
  
  /*
   * Allocates a single item from a zone.
   *
   * Arguments
   *      zone   The zone to alloc for.
   *      udata  The data to be passed to the constructor.
   *      domain The domain to allocate from or UMA_ANYDOMAIN.
   *      flags  M_WAITOK, M_NOWAIT, M_ZERO.
   *
   * Returns
   *      NULL if there is no memory and M_NOWAIT is set
   *      An item if successful
   */
  
  static void *
  zone_alloc_item(uma_zone_t zone, void *udata, int domain, int flags)
  {
          void *item;
  
          if (zone->uz_max_items > 0 && zone_alloc_limit(zone, 1, flags) == 0) {
                  counter_u64_add(zone->uz_fails, 1);
                  return (NULL);
          }
  
          /* Avoid allocs targeting empty domains. */
          if (domain != UMA_ANYDOMAIN && VM_DOMAIN_EMPTY(domain))
                  domain = UMA_ANYDOMAIN;
  
          if (zone->uz_import(zone->uz_arg, &item, 1, domain, flags) != 1)
                  goto fail_cnt;
  
          /*
           * We have to call both the zone's init (not the keg's init)
           * and the zone's ctor.  This is because the item is going from
           * a keg slab directly to the user, and the user is expecting it
           * to be both zone-init'd as well as zone-ctor'd.
           */
          if (zone->uz_init != NULL) {
                  if (zone->uz_init(item, zone->uz_size, flags) != 0) {
                          zone_free_item(zone, item, udata, SKIP_FINI | SKIP_CNT);
                          goto fail_cnt;
                  }
          }
          item = item_ctor(zone, zone->uz_flags, zone->uz_size, udata, flags,
              item);
          if (item == NULL)
                  goto fail;
  
          counter_u64_add(zone->uz_allocs, 1);
          CTR3(KTR_UMA, "zone_alloc_item item %p from %s(%p)", item,
              zone->uz_name, zone);
  
          return (item);
  
  fail_cnt:
          counter_u64_add(zone->uz_fails, 1);
  fail:
          if (zone->uz_max_items > 0)
                  zone_free_limit(zone, 1);
          CTR2(KTR_UMA, "zone_alloc_item failed from %s(%p)",
              zone->uz_name, zone);
  
          return (NULL);
  }
  
  /* See uma.h */
  void
  uma_zfree_smr(uma_zone_t zone, void *item)
  {
          uma_cache_t cache;
          uma_cache_bucket_t bucket;
          int itemdomain, uz_flags;
  
  #ifdef UMA_ZALLOC_DEBUG
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) != 0,
              ("uma_zfree_smr: called with non-SMR zone."));
          KASSERT(item != NULL, ("uma_zfree_smr: Called with NULL pointer."));
          SMR_ASSERT_NOT_ENTERED(zone->uz_smr);
          if (uma_zfree_debug(zone, item, NULL) == EJUSTRETURN)
                  return;
  #endif
          cache = &zone->uz_cpu[curcpu];
          uz_flags = cache_uz_flags(cache);
          itemdomain = 0;
  #ifdef NUMA
          if ((uz_flags & UMA_ZONE_FIRSTTOUCH) != 0)
                  itemdomain = item_domain(item);
  #endif
          critical_enter();
          do {
                  cache = &zone->uz_cpu[curcpu];
                  /* SMR Zones must free to the free bucket. */
                  bucket = &cache->uc_freebucket;
  #ifdef NUMA
                  if ((uz_flags & UMA_ZONE_FIRSTTOUCH) != 0 &&
                      PCPU_GET(domain) != itemdomain) {
                          bucket = &cache->uc_crossbucket;
                  }
  #endif
                  if (__predict_true(bucket->ucb_cnt < bucket->ucb_entries)) {
                          cache_bucket_push(cache, bucket, item);
                          critical_exit();
                          return;
                  }
          } while (cache_free(zone, cache, NULL, item, itemdomain));
          critical_exit();
  
          /*
           * If nothing else caught this, we'll just do an internal free.
           */
          zone_free_item(zone, item, NULL, SKIP_NONE);
  }
  
  /* See uma.h */
  void
  uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
  {
          uma_cache_t cache;
          uma_cache_bucket_t bucket;
          int itemdomain, uz_flags;
  
          /* Enable entropy collection for RANDOM_ENABLE_UMA kernel option */
          random_harvest_fast_uma(&zone, sizeof(zone), RANDOM_UMA);
  
          CTR2(KTR_UMA, "uma_zfree_arg zone %s(%p)", zone->uz_name, zone);
  
  #ifdef UMA_ZALLOC_DEBUG
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) == 0,
              ("uma_zfree_arg: called with SMR zone."));
          if (uma_zfree_debug(zone, item, udata) == EJUSTRETURN)
                  return;
  #endif
          /* uma_zfree(..., NULL) does nothing, to match free(9). */
          if (item == NULL)
                  return;
  
          /*
           * We are accessing the per-cpu cache without a critical section to
           * fetch size and flags.  This is acceptable, if we are preempted we
           * will simply read another cpu's line.
           */
          cache = &zone->uz_cpu[curcpu];
          uz_flags = cache_uz_flags(cache);
          if (UMA_ALWAYS_CTORDTOR ||
              __predict_false((uz_flags & UMA_ZFLAG_CTORDTOR) != 0))
                  item_dtor(zone, item, cache_uz_size(cache), udata, SKIP_NONE);
  
          /*
           * The race here is acceptable.  If we miss it we'll just have to wait
           * a little longer for the limits to be reset.
           */
          if (__predict_false(uz_flags & UMA_ZFLAG_LIMIT)) {
                  if (atomic_load_32(&zone->uz_sleepers) > 0)
                          goto zfree_item;
          }
  
          /*
           * If possible, free to the per-CPU cache.  There are two
           * requirements for safe access to the per-CPU cache: (1) the thread
           * accessing the cache must not be preempted or yield during access,
           * and (2) the thread must not migrate CPUs without switching which
           * cache it accesses.  We rely on a critical section to prevent
           * preemption and migration.  We release the critical section in
           * order to acquire the zone mutex if we are unable to free to the
           * current cache; when we re-acquire the critical section, we must
           * detect and handle migration if it has occurred.
           */
          itemdomain = 0;
  #ifdef NUMA
          if ((uz_flags & UMA_ZONE_FIRSTTOUCH) != 0)
                  itemdomain = item_domain(item);
  #endif
          critical_enter();
          do {
                  cache = &zone->uz_cpu[curcpu];
                  /*
                   * Try to free into the allocbucket first to give LIFO
                   * ordering for cache-hot datastructures.  Spill over
                   * into the freebucket if necessary.  Alloc will swap
                   * them if one runs dry.
                   */
                  bucket = &cache->uc_allocbucket;
  #ifdef NUMA
                  if ((uz_flags & UMA_ZONE_FIRSTTOUCH) != 0 &&
                      PCPU_GET(domain) != itemdomain) {
                          bucket = &cache->uc_crossbucket;
                  } else
  #endif
                  if (bucket->ucb_cnt == bucket->ucb_entries &&
                     cache->uc_freebucket.ucb_cnt <
                     cache->uc_freebucket.ucb_entries)
                          cache_bucket_swap(&cache->uc_freebucket,
                              &cache->uc_allocbucket);
                  if (__predict_true(bucket->ucb_cnt < bucket->ucb_entries)) {
                          cache_bucket_push(cache, bucket, item);
                          critical_exit();
                          return;
                  }
          } while (cache_free(zone, cache, udata, item, itemdomain));
          critical_exit();
  
          /*
           * If nothing else caught this, we'll just do an internal free.
           */
  zfree_item:
          zone_free_item(zone, item, udata, SKIP_DTOR);
  }
  
  #ifdef NUMA
  /*
   * sort crossdomain free buckets to domain correct buckets and cache
   * them.
   */
  static void
  zone_free_cross(uma_zone_t zone, uma_bucket_t bucket, void *udata)
  {
          struct uma_bucketlist emptybuckets, fullbuckets;
          uma_zone_domain_t zdom;
          uma_bucket_t b;
          smr_seq_t seq;
          void *item;
          int domain;
  
          CTR3(KTR_UMA,
              "uma_zfree: zone %s(%p) draining cross bucket %p",
              zone->uz_name, zone, bucket);
  
          /*
           * It is possible for buckets to arrive here out of order so we fetch
           * the current smr seq rather than accepting the bucket's.
           */
          seq = SMR_SEQ_INVALID;
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0)
                  seq = smr_advance(zone->uz_smr);
  
          /*
           * To avoid having ndomain * ndomain buckets for sorting we have a
           * lock on the current crossfree bucket.  A full matrix with
           * per-domain locking could be used if necessary.
           */
          STAILQ_INIT(&emptybuckets);
          STAILQ_INIT(&fullbuckets);
          ZONE_CROSS_LOCK(zone);
          for (; bucket->ub_cnt > 0; bucket->ub_cnt--) {
                  item = bucket->ub_bucket[bucket->ub_cnt - 1];
                  domain = item_domain(item);
                  zdom = ZDOM_GET(zone, domain);
                  if (zdom->uzd_cross == NULL) {
                          if ((b = STAILQ_FIRST(&emptybuckets)) != NULL) {
                                  STAILQ_REMOVE_HEAD(&emptybuckets, ub_link);
                                  zdom->uzd_cross = b;
                          } else {
                                  /*
                                   * Avoid allocating a bucket with the cross lock
                                   * held, since allocation can trigger a
                                   * cross-domain free and bucket zones may
                                   * allocate from each other.
                                   */
                                  ZONE_CROSS_UNLOCK(zone);
                                  b = bucket_alloc(zone, udata, M_NOWAIT);
                                  if (b == NULL)
                                          goto out;
                                  ZONE_CROSS_LOCK(zone);
                                  if (zdom->uzd_cross != NULL) {
                                          STAILQ_INSERT_HEAD(&emptybuckets, b,
                                              ub_link);
                                  } else {
                                          zdom->uzd_cross = b;
                                  }
                          }
                  }
                  b = zdom->uzd_cross;
                  b->ub_bucket[b->ub_cnt++] = item;
                  b->ub_seq = seq;
                  if (b->ub_cnt == b->ub_entries) {
                          STAILQ_INSERT_HEAD(&fullbuckets, b, ub_link);
                          if ((b = STAILQ_FIRST(&emptybuckets)) != NULL)
                                  STAILQ_REMOVE_HEAD(&emptybuckets, ub_link);
                          zdom->uzd_cross = b;
                  }
          }
          ZONE_CROSS_UNLOCK(zone);
  out:
          if (bucket->ub_cnt == 0)
                  bucket->ub_seq = SMR_SEQ_INVALID;
          bucket_free(zone, bucket, udata);
  
          while ((b = STAILQ_FIRST(&emptybuckets)) != NULL) {
                  STAILQ_REMOVE_HEAD(&emptybuckets, ub_link);
                  bucket_free(zone, b, udata);
          }
          while ((b = STAILQ_FIRST(&fullbuckets)) != NULL) {
                  STAILQ_REMOVE_HEAD(&fullbuckets, ub_link);
                  domain = item_domain(b->ub_bucket[0]);
                  zone_put_bucket(zone, domain, b, udata, true);
          }
  }
  #endif
  
  static void
  zone_free_bucket(uma_zone_t zone, uma_bucket_t bucket, void *udata,
      int itemdomain, bool ws)
  {
  
  #ifdef NUMA
          /*
           * Buckets coming from the wrong domain will be entirely for the
           * only other domain on two domain systems.  In this case we can
           * simply cache them.  Otherwise we need to sort them back to
           * correct domains.
           */
          if ((zone->uz_flags & UMA_ZONE_FIRSTTOUCH) != 0 &&
              vm_ndomains > 2 && PCPU_GET(domain) != itemdomain) {
                  zone_free_cross(zone, bucket, udata);
                  return;
          }
  #endif
  
          /*
           * Attempt to save the bucket in the zone's domain bucket cache.
           */
          CTR3(KTR_UMA,
              "uma_zfree: zone %s(%p) putting bucket %p on free list",
              zone->uz_name, zone, bucket);
          /* ub_cnt is pointing to the last free item */
          if ((zone->uz_flags & UMA_ZONE_ROUNDROBIN) != 0)
                  itemdomain = zone_domain_lowest(zone, itemdomain);
          zone_put_bucket(zone, itemdomain, bucket, udata, ws);
  }
  
  /*
   * Populate a free or cross bucket for the current cpu cache.  Free any
   * existing full bucket either to the zone cache or back to the slab layer.
   *
   * Enters and returns in a critical section.  false return indicates that
   * we can not satisfy this free in the cache layer.  true indicates that
   * the caller should retry.
   */
  static __noinline bool
  cache_free(uma_zone_t zone, uma_cache_t cache, void *udata, void *item,
      int itemdomain)
  {
          uma_cache_bucket_t cbucket;
          uma_bucket_t newbucket, bucket;
  
          CRITICAL_ASSERT(curthread);
  
          if (zone->uz_bucket_size == 0)
                  return false;
  
          cache = &zone->uz_cpu[curcpu];
          newbucket = NULL;
  
          /*
           * FIRSTTOUCH domains need to free to the correct zdom.  When
           * enabled this is the zdom of the item.   The bucket is the
           * cross bucket if the current domain and itemdomain do not match.
           */
          cbucket = &cache->uc_freebucket;
  #ifdef NUMA
          if ((cache_uz_flags(cache) & UMA_ZONE_FIRSTTOUCH) != 0) {
                  if (PCPU_GET(domain) != itemdomain) {
                          cbucket = &cache->uc_crossbucket;
                          if (cbucket->ucb_cnt != 0)
                                  counter_u64_add(zone->uz_xdomain,
                                      cbucket->ucb_cnt);
                  }
          }
  #endif
          bucket = cache_bucket_unload(cbucket);
          KASSERT(bucket == NULL || bucket->ub_cnt == bucket->ub_entries,
              ("cache_free: Entered with non-full free bucket."));
  
          /* We are no longer associated with this CPU. */
          critical_exit();
  
          /*
           * Don't let SMR zones operate without a free bucket.  Force
           * a synchronize and re-use this one.  We will only degrade
           * to a synchronize every bucket_size items rather than every
           * item if we fail to allocate a bucket.
           */
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0) {
                  if (bucket != NULL)
                          bucket->ub_seq = smr_advance(zone->uz_smr);
                  newbucket = bucket_alloc(zone, udata, M_NOWAIT);
                  if (newbucket == NULL && bucket != NULL) {
                          bucket_drain(zone, bucket);
                          newbucket = bucket;
                          bucket = NULL;
                  }
          } else if (!bucketdisable)
                  newbucket = bucket_alloc(zone, udata, M_NOWAIT);
  
          if (bucket != NULL)
                  zone_free_bucket(zone, bucket, udata, itemdomain, true);
  
          critical_enter();
          if ((bucket = newbucket) == NULL)
                  return (false);
          cache = &zone->uz_cpu[curcpu];
  #ifdef NUMA
          /*
           * Check to see if we should be populating the cross bucket.  If it
           * is already populated we will fall through and attempt to populate
           * the free bucket.
           */
          if ((cache_uz_flags(cache) & UMA_ZONE_FIRSTTOUCH) != 0) {
                  if (PCPU_GET(domain) != itemdomain &&
                      cache->uc_crossbucket.ucb_bucket == NULL) {
                          cache_bucket_load_cross(cache, bucket);
                          return (true);
                  }
          }
  #endif
          /*
           * We may have lost the race to fill the bucket or switched CPUs.
           */
          if (cache->uc_freebucket.ucb_bucket != NULL) {
                  critical_exit();
                  bucket_free(zone, bucket, udata);
                  critical_enter();
          } else
                  cache_bucket_load_free(cache, bucket);
  
          return (true);
  }
  
  static void
  slab_free_item(uma_zone_t zone, uma_slab_t slab, void *item)
  {
          uma_keg_t keg;
          uma_domain_t dom;
          int freei;
  
          keg = zone->uz_keg;
          KEG_LOCK_ASSERT(keg, slab->us_domain);
  
          /* Do we need to remove from any lists? */
          dom = &keg->uk_domain[slab->us_domain];
          if (slab->us_freecount + 1 == keg->uk_ipers) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&dom->ud_free_slab, slab, us_link);
                  dom->ud_free_slabs++;
          } else if (slab->us_freecount == 0) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&dom->ud_part_slab, slab, us_link);
          }
  
          /* Slab management. */
          freei = slab_item_index(slab, keg, item);
          BIT_SET(keg->uk_ipers, freei, &slab->us_free);
          slab->us_freecount++;
  
          /* Keg statistics. */
          dom->ud_free_items++;
  }
  
  static void
  zone_release(void *arg, void **bucket, int cnt)
  {
          struct mtx *lock;
          uma_zone_t zone;
          uma_slab_t slab;
          uma_keg_t keg;
          uint8_t *mem;
          void *item;
          int i;
  
          zone = arg;
          keg = zone->uz_keg;
          lock = NULL;
          if (__predict_false((zone->uz_flags & UMA_ZFLAG_HASH) != 0))
                  lock = KEG_LOCK(keg, 0);
          for (i = 0; i < cnt; i++) {
                  item = bucket[i];
                  if (__predict_true((zone->uz_flags & UMA_ZFLAG_VTOSLAB) != 0)) {
                          slab = vtoslab((vm_offset_t)item);
                  } else {
                          mem = (uint8_t *)((uintptr_t)item & (~UMA_SLAB_MASK));
                          if ((zone->uz_flags & UMA_ZFLAG_HASH) != 0)
                                  slab = hash_sfind(&keg->uk_hash, mem);
                          else
                                  slab = (uma_slab_t)(mem + keg->uk_pgoff);
                  }
                  if (lock != KEG_LOCKPTR(keg, slab->us_domain)) {
                          if (lock != NULL)
                                  mtx_unlock(lock);
                          lock = KEG_LOCK(keg, slab->us_domain);
                  }
                  slab_free_item(zone, slab, item);
          }
          if (lock != NULL)
                  mtx_unlock(lock);
  }
  
  /*
   * Frees a single item to any zone.
   *
   * Arguments:
   *      zone   The zone to free to
   *      item   The item we're freeing
   *      udata  User supplied data for the dtor
   *      skip   Skip dtors and finis
   */
  static __noinline void
  zone_free_item(uma_zone_t zone, void *item, void *udata, enum zfreeskip skip)
  {
  
          /*
           * If a free is sent directly to an SMR zone we have to
           * synchronize immediately because the item can instantly
           * be reallocated. This should only happen in degenerate
           * cases when no memory is available for per-cpu caches.
           */
          if ((zone->uz_flags & UMA_ZONE_SMR) != 0 && skip == SKIP_NONE)
                  smr_synchronize(zone->uz_smr);
  
          item_dtor(zone, item, zone->uz_size, udata, skip);
  
          if (skip < SKIP_FINI && zone->uz_fini)
                  zone->uz_fini(item, zone->uz_size);
  
          zone->uz_release(zone->uz_arg, &item, 1);
  
          if (skip & SKIP_CNT)
                  return;
  
          counter_u64_add(zone->uz_frees, 1);
  
          if (zone->uz_max_items > 0)
                  zone_free_limit(zone, 1);
  }
  
  /* See uma.h */
  int
  uma_zone_set_max(uma_zone_t zone, int nitems)
  {
  
          /*
           * If the limit is small, we may need to constrain the maximum per-CPU
           * cache size, or disable caching entirely.
           */
          uma_zone_set_maxcache(zone, nitems);
  
          /*
           * XXX This can misbehave if the zone has any allocations with
           * no limit and a limit is imposed.  There is currently no
           * way to clear a limit.
           */
          ZONE_LOCK(zone);
          zone->uz_max_items = nitems;
          zone->uz_flags |= UMA_ZFLAG_LIMIT;
          zone_update_caches(zone);
          /* We may need to wake waiters. */
          wakeup(&zone->uz_max_items);
          ZONE_UNLOCK(zone);
  
          return (nitems);
  }
  
  /* See uma.h */
  void
  uma_zone_set_maxcache(uma_zone_t zone, int nitems)
  {
          int bpcpu, bpdom, bsize, nb;
  
          ZONE_LOCK(zone);
  
          /*
           * Compute a lower bound on the number of items that may be cached in
           * the zone.  Each CPU gets at least two buckets, and for cross-domain
           * frees we use an additional bucket per CPU and per domain.  Select the
           * largest bucket size that does not exceed half of the requested limit,
           * with the left over space given to the full bucket cache.
           */
          bpdom = 0;
          bpcpu = 2;
  #ifdef NUMA
          if ((zone->uz_flags & UMA_ZONE_FIRSTTOUCH) != 0 && vm_ndomains > 1) {
                  bpcpu++;
                  bpdom++;
          }
  #endif
          nb = bpcpu * mp_ncpus + bpdom * vm_ndomains;
          bsize = nitems / nb / 2;
          if (bsize > BUCKET_MAX)
                  bsize = BUCKET_MAX;
          else if (bsize == 0 && nitems / nb > 0)
                  bsize = 1;
          zone->uz_bucket_size_max = zone->uz_bucket_size = bsize;
          if (zone->uz_bucket_size_min > zone->uz_bucket_size_max)
                  zone->uz_bucket_size_min = zone->uz_bucket_size_max;
          zone->uz_bucket_max = nitems - nb * bsize;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  int
  uma_zone_get_max(uma_zone_t zone)
  {
          int nitems;
  
          nitems = atomic_load_64(&zone->uz_max_items);
  
          return (nitems);
  }
  
  /* See uma.h */
  void
  uma_zone_set_warning(uma_zone_t zone, const char *warning)
  {
  
          ZONE_ASSERT_COLD(zone);
          zone->uz_warning = warning;
  }
  
  /* See uma.h */
  void
  uma_zone_set_maxaction(uma_zone_t zone, uma_maxaction_t maxaction)
  {
  
          ZONE_ASSERT_COLD(zone);
          TASK_INIT(&zone->uz_maxaction, 0, (task_fn_t *)maxaction, zone);
  }
  
  /* See uma.h */
  int
  uma_zone_get_cur(uma_zone_t zone)
  {
          int64_t nitems;
          u_int i;
  
          nitems = 0;
          if (zone->uz_allocs != EARLY_COUNTER && zone->uz_frees != EARLY_COUNTER)
                  nitems = counter_u64_fetch(zone->uz_allocs) -
                      counter_u64_fetch(zone->uz_frees);
          CPU_FOREACH(i)
                  nitems += atomic_load_64(&zone->uz_cpu[i].uc_allocs) -
                      atomic_load_64(&zone->uz_cpu[i].uc_frees);
  
          return (nitems < 0 ? 0 : nitems);
  }
  
  static uint64_t
  uma_zone_get_allocs(uma_zone_t zone)
  {
          uint64_t nitems;
          u_int i;
  
          nitems = 0;
          if (zone->uz_allocs != EARLY_COUNTER)
                  nitems = counter_u64_fetch(zone->uz_allocs);
          CPU_FOREACH(i)
                  nitems += atomic_load_64(&zone->uz_cpu[i].uc_allocs);
  
          return (nitems);
  }
  
  static uint64_t
  uma_zone_get_frees(uma_zone_t zone)
  {
          uint64_t nitems;
          u_int i;
  
          nitems = 0;
          if (zone->uz_frees != EARLY_COUNTER)
                  nitems = counter_u64_fetch(zone->uz_frees);
          CPU_FOREACH(i)
                  nitems += atomic_load_64(&zone->uz_cpu[i].uc_frees);
  
          return (nitems);
  }
  
  #ifdef INVARIANTS
  /* Used only for KEG_ASSERT_COLD(). */
  static uint64_t
  uma_keg_get_allocs(uma_keg_t keg)
  {
          uma_zone_t z;
          uint64_t nitems;
  
          nitems = 0;
          LIST_FOREACH(z, &keg->uk_zones, uz_link)
                  nitems += uma_zone_get_allocs(z);
  
          return (nitems);
  }
  #endif
  
  /* See uma.h */
  void
  uma_zone_set_init(uma_zone_t zone, uma_init uminit)
  {
          uma_keg_t keg;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          keg->uk_init = uminit;
  }
  
  /* See uma.h */
  void
  uma_zone_set_fini(uma_zone_t zone, uma_fini fini)
  {
          uma_keg_t keg;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          keg->uk_fini = fini;
  }
  
  /* See uma.h */
  void
  uma_zone_set_zinit(uma_zone_t zone, uma_init zinit)
  {
  
          ZONE_ASSERT_COLD(zone);
          zone->uz_init = zinit;
  }
  
  /* See uma.h */
  void
  uma_zone_set_zfini(uma_zone_t zone, uma_fini zfini)
  {
  
          ZONE_ASSERT_COLD(zone);
          zone->uz_fini = zfini;
  }
  
  /* See uma.h */
  void
  uma_zone_set_freef(uma_zone_t zone, uma_free freef)
  {
          uma_keg_t keg;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          keg->uk_freef = freef;
  }
  
  /* See uma.h */
  void
  uma_zone_set_allocf(uma_zone_t zone, uma_alloc allocf)
  {
          uma_keg_t keg;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          keg->uk_allocf = allocf;
  }
  
  /* See uma.h */
  void
  uma_zone_set_smr(uma_zone_t zone, smr_t smr)
  {
  
          ZONE_ASSERT_COLD(zone);
  
          KASSERT(smr != NULL, ("Got NULL smr"));
          KASSERT((zone->uz_flags & UMA_ZONE_SMR) == 0,
              ("zone %p (%s) already uses SMR", zone, zone->uz_name));
          zone->uz_flags |= UMA_ZONE_SMR;
          zone->uz_smr = smr;
          zone_update_caches(zone);
  }
  
  smr_t
  uma_zone_get_smr(uma_zone_t zone)
  {
  
          return (zone->uz_smr);
  }
  
  /* See uma.h */
  void
  uma_zone_reserve(uma_zone_t zone, int items)
  {
          uma_keg_t keg;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          keg->uk_reserve = items;
  }
  
  /* See uma.h */
  int
  uma_zone_reserve_kva(uma_zone_t zone, int count)
  {
          uma_keg_t keg;
          vm_offset_t kva;
          u_int pages;
  
          KEG_GET(zone, keg);
          KEG_ASSERT_COLD(keg);
          ZONE_ASSERT_COLD(zone);
  
          pages = howmany(count, keg->uk_ipers) * keg->uk_ppera;
  
  #ifdef UMA_MD_SMALL_ALLOC
          if (keg->uk_ppera > 1) {
  #else
          if (1) {
  #endif
                  kva = kva_alloc((vm_size_t)pages * PAGE_SIZE);
                  if (kva == 0)
                          return (0);
          } else
                  kva = 0;
  
          MPASS(keg->uk_kva == 0);
          keg->uk_kva = kva;
          keg->uk_offset = 0;
          zone->uz_max_items = pages * keg->uk_ipers;
  #ifdef UMA_MD_SMALL_ALLOC
          keg->uk_allocf = (keg->uk_ppera > 1) ? noobj_alloc : uma_small_alloc;
  #else
          keg->uk_allocf = noobj_alloc;
  #endif
          keg->uk_flags |= UMA_ZFLAG_LIMIT | UMA_ZONE_NOFREE;
          zone->uz_flags |= UMA_ZFLAG_LIMIT | UMA_ZONE_NOFREE;
          zone_update_caches(zone);
  
          return (1);
  }
  
  /* See uma.h */
  void
  uma_prealloc(uma_zone_t zone, int items)
  {
          struct vm_domainset_iter di;
          uma_domain_t dom;
          uma_slab_t slab;
          uma_keg_t keg;
          int aflags, domain, slabs;
  
          KEG_GET(zone, keg);
          slabs = howmany(items, keg->uk_ipers);
          while (slabs-- > 0) {
                  aflags = M_NOWAIT;
                  vm_domainset_iter_policy_ref_init(&di, &keg->uk_dr, &domain,
                      &aflags);
                  for (;;) {
                          slab = keg_alloc_slab(keg, zone, domain, M_WAITOK,
                              aflags);
                          if (slab != NULL) {
                                  dom = &keg->uk_domain[slab->us_domain];
                                  /*
                                   * keg_alloc_slab() always returns a slab on the
                                   * partial list.
                                   */
                                  LIST_REMOVE(slab, us_link);
                                  LIST_INSERT_HEAD(&dom->ud_free_slab, slab,
                                      us_link);
                                  dom->ud_free_slabs++;
                                  KEG_UNLOCK(keg, slab->us_domain);
                                  break;
                          }
                          if (vm_domainset_iter_policy(&di, &domain) != 0)
                                  vm_wait_doms(&keg->uk_dr.dr_policy->ds_mask, 0);
                  }
          }
  }
  
  /*
   * Returns a snapshot of memory consumption in bytes.
   */
  size_t
  uma_zone_memory(uma_zone_t zone)
  {
          size_t sz;
          int i;
  
          sz = 0;
          if (zone->uz_flags & UMA_ZFLAG_CACHE) {
                  for (i = 0; i < vm_ndomains; i++)
                          sz += ZDOM_GET(zone, i)->uzd_nitems;
                  return (sz * zone->uz_size);
          }
          for (i = 0; i < vm_ndomains; i++)
                  sz += zone->uz_keg->uk_domain[i].ud_pages;
  
          return (sz * PAGE_SIZE);
  }
  
  /* See uma.h */
  void
  uma_reclaim(int req)
  {
  
          CTR0(KTR_UMA, "UMA: vm asked us to release pages!");
          sx_xlock(&uma_reclaim_lock);
          bucket_enable();
  
          switch (req) {
          case UMA_RECLAIM_TRIM:
                  zone_foreach(zone_trim, NULL);
                  break;
          case UMA_RECLAIM_DRAIN:
          case UMA_RECLAIM_DRAIN_CPU:
                  zone_foreach(zone_drain, NULL);
                  if (req == UMA_RECLAIM_DRAIN_CPU) {
                          pcpu_cache_drain_safe(NULL);
                          zone_foreach(zone_drain, NULL);
                  }
                  break;
          default:
                  panic("unhandled reclamation request %d", req);
          }
  
          /*
           * Some slabs may have been freed but this zone will be visited early
           * we visit again so that we can free pages that are empty once other
           * zones are drained.  We have to do the same for buckets.
           */
          zone_drain(slabzones[0], NULL);
          zone_drain(slabzones[1], NULL);
          bucket_zone_drain();
          sx_xunlock(&uma_reclaim_lock);
  }
  
  static volatile int uma_reclaim_needed;
  
  void
  uma_reclaim_wakeup(void)
  {
  
          if (atomic_fetchadd_int(&uma_reclaim_needed, 1) == 0)
                  wakeup(uma_reclaim);
  }
  
  void
  uma_reclaim_worker(void *arg __unused)
  {
  
          for (;;) {
                  sx_xlock(&uma_reclaim_lock);
                  while (atomic_load_int(&uma_reclaim_needed) == 0)
                          sx_sleep(uma_reclaim, &uma_reclaim_lock, PVM, "umarcl",
                              hz);
                  sx_xunlock(&uma_reclaim_lock);
                  EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_KMEM);
                  uma_reclaim(UMA_RECLAIM_DRAIN_CPU);
                  atomic_store_int(&uma_reclaim_needed, 0);
                  /* Don't fire more than once per-second. */
                  pause("umarclslp", hz);
          }
  }
  
  /* See uma.h */
  void
  uma_zone_reclaim(uma_zone_t zone, int req)
  {
  
          switch (req) {
          case UMA_RECLAIM_TRIM:
                  zone_trim(zone, NULL);
                  break;
          case UMA_RECLAIM_DRAIN:
                  zone_drain(zone, NULL);
                  break;
          case UMA_RECLAIM_DRAIN_CPU:
                  pcpu_cache_drain_safe(zone);
                  zone_drain(zone, NULL);
                  break;
          default:
                  panic("unhandled reclamation request %d", req);
          }
  }
  
  /* See uma.h */
  int
  uma_zone_exhausted(uma_zone_t zone)
  {
  
          return (atomic_load_32(&zone->uz_sleepers) > 0);
  }
  
  unsigned long
  uma_limit(void)
  {
  
          return (uma_kmem_limit);
  }
  
  void
  uma_set_limit(unsigned long limit)
  {
  
          uma_kmem_limit = limit;
  }
  
  unsigned long
  uma_size(void)
  {
  
          return (atomic_load_long(&uma_kmem_total));
  }
  
  long
  uma_avail(void)
  {
  
          return (uma_kmem_limit - uma_size());
  }
  
  #ifdef DDB
  /*
   * Generate statistics across both the zone and its per-cpu cache's.  Return
   * desired statistics if the pointer is non-NULL for that statistic.
   *
   * Note: does not update the zone statistics, as it can't safely clear the
   * per-CPU cache statistic.
   *
   */
  static void
  uma_zone_sumstat(uma_zone_t z, long *cachefreep, uint64_t *allocsp,
      uint64_t *freesp, uint64_t *sleepsp, uint64_t *xdomainp)
  {
          uma_cache_t cache;
          uint64_t allocs, frees, sleeps, xdomain;
          int cachefree, cpu;
  
          allocs = frees = sleeps = xdomain = 0;
          cachefree = 0;
          CPU_FOREACH(cpu) {
                  cache = &z->uz_cpu[cpu];
                  cachefree += cache->uc_allocbucket.ucb_cnt;
                  cachefree += cache->uc_freebucket.ucb_cnt;
                  xdomain += cache->uc_crossbucket.ucb_cnt;
                  cachefree += cache->uc_crossbucket.ucb_cnt;
                  allocs += cache->uc_allocs;
                  frees += cache->uc_frees;
          }
          allocs += counter_u64_fetch(z->uz_allocs);
          frees += counter_u64_fetch(z->uz_frees);
          xdomain += counter_u64_fetch(z->uz_xdomain);
          sleeps += z->uz_sleeps;
          if (cachefreep != NULL)
                  *cachefreep = cachefree;
          if (allocsp != NULL)
                  *allocsp = allocs;
          if (freesp != NULL)
                  *freesp = frees;
          if (sleepsp != NULL)
                  *sleepsp = sleeps;
          if (xdomainp != NULL)
                  *xdomainp = xdomain;
  }
  #endif /* DDB */
  
  static int
  sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS)
  {
          uma_keg_t kz;
          uma_zone_t z;
          int count;
  
          count = 0;
          rw_rlock(&uma_rwlock);
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link)
                          count++;
          }
          LIST_FOREACH(z, &uma_cachezones, uz_link)
                  count++;
  
          rw_runlock(&uma_rwlock);
          return (sysctl_handle_int(oidp, &count, 0, req));
  }
  
  static void
  uma_vm_zone_stats(struct uma_type_header *uth, uma_zone_t z, struct sbuf *sbuf,
      struct uma_percpu_stat *ups, bool internal)
  {
          uma_zone_domain_t zdom;
          uma_cache_t cache;
          int i;
  
          for (i = 0; i < vm_ndomains; i++) {
                  zdom = ZDOM_GET(z, i);
                  uth->uth_zone_free += zdom->uzd_nitems;
          }
          uth->uth_allocs = counter_u64_fetch(z->uz_allocs);
          uth->uth_frees = counter_u64_fetch(z->uz_frees);
          uth->uth_fails = counter_u64_fetch(z->uz_fails);
          uth->uth_xdomain = counter_u64_fetch(z->uz_xdomain);
          uth->uth_sleeps = z->uz_sleeps;
  
          for (i = 0; i < mp_maxid + 1; i++) {
                  bzero(&ups[i], sizeof(*ups));
                  if (internal || CPU_ABSENT(i))
                          continue;
                  cache = &z->uz_cpu[i];
                  ups[i].ups_cache_free += cache->uc_allocbucket.ucb_cnt;
                  ups[i].ups_cache_free += cache->uc_freebucket.ucb_cnt;
                  ups[i].ups_cache_free += cache->uc_crossbucket.ucb_cnt;
                  ups[i].ups_allocs = cache->uc_allocs;
                  ups[i].ups_frees = cache->uc_frees;
          }
  }
  
  static int
  sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS)
  {
          struct uma_stream_header ush;
          struct uma_type_header uth;
          struct uma_percpu_stat *ups;
          struct sbuf sbuf;
          uma_keg_t kz;
          uma_zone_t z;
          uint64_t items;
          uint32_t kfree, pages;
          int count, error, i;
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error != 0)
                  return (error);
          sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
          sbuf_clear_flags(&sbuf, SBUF_INCLUDENUL);
          ups = malloc((mp_maxid + 1) * sizeof(*ups), M_TEMP, M_WAITOK);
  
          count = 0;
          rw_rlock(&uma_rwlock);
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link)
                          count++;
          }
  
          LIST_FOREACH(z, &uma_cachezones, uz_link)
                  count++;
  
          /*
           * Insert stream header.
           */
          bzero(&ush, sizeof(ush));
          ush.ush_version = UMA_STREAM_VERSION;
          ush.ush_maxcpus = (mp_maxid + 1);
          ush.ush_count = count;
          (void)sbuf_bcat(&sbuf, &ush, sizeof(ush));
  
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  kfree = pages = 0;
                  for (i = 0; i < vm_ndomains; i++) {
                          kfree += kz->uk_domain[i].ud_free_items;
                          pages += kz->uk_domain[i].ud_pages;
                  }
                  LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                          bzero(&uth, sizeof(uth));
                          strlcpy(uth.uth_name, z->uz_name, UTH_MAX_NAME);
                          uth.uth_align = kz->uk_align;
                          uth.uth_size = kz->uk_size;
                          uth.uth_rsize = kz->uk_rsize;
                          if (z->uz_max_items > 0) {
                                  items = UZ_ITEMS_COUNT(z->uz_items);
                                  uth.uth_pages = (items / kz->uk_ipers) *
                                          kz->uk_ppera;
                          } else
                                  uth.uth_pages = pages;
                          uth.uth_maxpages = (z->uz_max_items / kz->uk_ipers) *
                              kz->uk_ppera;
                          uth.uth_limit = z->uz_max_items;
                          uth.uth_keg_free = kfree;
  
                          /*
                           * A zone is secondary is it is not the first entry
                           * on the keg's zone list.
                           */
                          if ((z->uz_flags & UMA_ZONE_SECONDARY) &&
                              (LIST_FIRST(&kz->uk_zones) != z))
                                  uth.uth_zone_flags = UTH_ZONE_SECONDARY;
                          uma_vm_zone_stats(&uth, z, &sbuf, ups,
                              kz->uk_flags & UMA_ZFLAG_INTERNAL);
                          (void)sbuf_bcat(&sbuf, &uth, sizeof(uth));
                          for (i = 0; i < mp_maxid + 1; i++)
                                  (void)sbuf_bcat(&sbuf, &ups[i], sizeof(ups[i]));
                  }
          }
          LIST_FOREACH(z, &uma_cachezones, uz_link) {
                  bzero(&uth, sizeof(uth));
                  strlcpy(uth.uth_name, z->uz_name, UTH_MAX_NAME);
                  uth.uth_size = z->uz_size;
                  uma_vm_zone_stats(&uth, z, &sbuf, ups, false);
                  (void)sbuf_bcat(&sbuf, &uth, sizeof(uth));
                  for (i = 0; i < mp_maxid + 1; i++)
                          (void)sbuf_bcat(&sbuf, &ups[i], sizeof(ups[i]));
          }
  
          rw_runlock(&uma_rwlock);
          error = sbuf_finish(&sbuf);
          sbuf_delete(&sbuf);
          free(ups, M_TEMP);
          return (error);
  }
  
  int
  sysctl_handle_uma_zone_max(SYSCTL_HANDLER_ARGS)
  {
          uma_zone_t zone = *(uma_zone_t *)arg1;
          int error, max;
  
          max = uma_zone_get_max(zone);
          error = sysctl_handle_int(oidp, &max, 0, req);
          if (error || !req->newptr)
                  return (error);
  
          uma_zone_set_max(zone, max);
  
          return (0);
  }
  
  int
  sysctl_handle_uma_zone_cur(SYSCTL_HANDLER_ARGS)
  {
          uma_zone_t zone;
          int cur;
  
          /*
           * Some callers want to add sysctls for global zones that
           * may not yet exist so they pass a pointer to a pointer.
           */
          if (arg2 == 0)
                  zone = *(uma_zone_t *)arg1;
          else
                  zone = arg1;
          cur = uma_zone_get_cur(zone);
          return (sysctl_handle_int(oidp, &cur, 0, req));
  }
  
  static int
  sysctl_handle_uma_zone_allocs(SYSCTL_HANDLER_ARGS)
  {
          uma_zone_t zone = arg1;
          uint64_t cur;
  
          cur = uma_zone_get_allocs(zone);
          return (sysctl_handle_64(oidp, &cur, 0, req));
  }
  
  static int
  sysctl_handle_uma_zone_frees(SYSCTL_HANDLER_ARGS)
  {
          uma_zone_t zone = arg1;
          uint64_t cur;
  
          cur = uma_zone_get_frees(zone);
          return (sysctl_handle_64(oidp, &cur, 0, req));
  }
  
  static int
  sysctl_handle_uma_zone_flags(SYSCTL_HANDLER_ARGS)
  {
          struct sbuf sbuf;
          uma_zone_t zone = arg1;
          int error;
  
          sbuf_new_for_sysctl(&sbuf, NULL, 0, req);
          if (zone->uz_flags != 0)
                  sbuf_printf(&sbuf, "0x%b", zone->uz_flags, PRINT_UMA_ZFLAGS);
          else
                  sbuf_printf(&sbuf, "");
          error = sbuf_finish(&sbuf);
          sbuf_delete(&sbuf);
  
          return (error);
  }
  
  static int
  sysctl_handle_uma_slab_efficiency(SYSCTL_HANDLER_ARGS)
  {
          uma_keg_t keg = arg1;
          int avail, effpct, total;
  
          total = keg->uk_ppera * PAGE_SIZE;
          if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) != 0)
                  total += slabzone(keg->uk_ipers)->uz_keg->uk_rsize;
          /*
           * We consider the client's requested size and alignment here, not the
           * real size determination uk_rsize, because we also adjust the real
           * size for internal implementation reasons (max bitset size).
           */
          avail = keg->uk_ipers * roundup2(keg->uk_size, keg->uk_align + 1);
          if ((keg->uk_flags & UMA_ZONE_PCPU) != 0)
                  avail *= mp_maxid + 1;
          effpct = 100 * avail / total;
          return (sysctl_handle_int(oidp, &effpct, 0, req));
  }
  
  static int
  sysctl_handle_uma_zone_items(SYSCTL_HANDLER_ARGS)
  {
          uma_zone_t zone = arg1;
          uint64_t cur;
  
          cur = UZ_ITEMS_COUNT(atomic_load_64(&zone->uz_items));
          return (sysctl_handle_64(oidp, &cur, 0, req));
  }
  
  #ifdef INVARIANTS
  static uma_slab_t
  uma_dbg_getslab(uma_zone_t zone, void *item)
  {
          uma_slab_t slab;
          uma_keg_t keg;
          uint8_t *mem;
  
          /*
           * It is safe to return the slab here even though the
           * zone is unlocked because the item's allocation state
           * essentially holds a reference.
           */
          mem = (uint8_t *)((uintptr_t)item & (~UMA_SLAB_MASK));
          if ((zone->uz_flags & UMA_ZFLAG_CACHE) != 0)
                  return (NULL);
          if (zone->uz_flags & UMA_ZFLAG_VTOSLAB)
                  return (vtoslab((vm_offset_t)mem));
          keg = zone->uz_keg;
          if ((keg->uk_flags & UMA_ZFLAG_HASH) == 0)
                  return ((uma_slab_t)(mem + keg->uk_pgoff));
          KEG_LOCK(keg, 0);
          slab = hash_sfind(&keg->uk_hash, mem);
          KEG_UNLOCK(keg, 0);
  
          return (slab);
  }
  
  static bool
  uma_dbg_zskip(uma_zone_t zone, void *mem)
  {
  
          if ((zone->uz_flags & UMA_ZFLAG_CACHE) != 0)
                  return (true);
  
          return (uma_dbg_kskip(zone->uz_keg, mem));
  }
  
  static bool
  uma_dbg_kskip(uma_keg_t keg, void *mem)
  {
          uintptr_t idx;
  
          if (dbg_divisor == 0)
                  return (true);
  
          if (dbg_divisor == 1)
                  return (false);
  
          idx = (uintptr_t)mem >> PAGE_SHIFT;
          if (keg->uk_ipers > 1) {
                  idx *= keg->uk_ipers;
                  idx += ((uintptr_t)mem & PAGE_MASK) / keg->uk_rsize;
          }
  
          if ((idx / dbg_divisor) * dbg_divisor != idx) {
                  counter_u64_add(uma_skip_cnt, 1);
                  return (true);
          }
          counter_u64_add(uma_dbg_cnt, 1);
  
          return (false);
  }
  
  /*
   * Set up the slab's freei data such that uma_dbg_free can function.
   *
   */
  static void
  uma_dbg_alloc(uma_zone_t zone, uma_slab_t slab, void *item)
  {
          uma_keg_t keg;
          int freei;
  
          if (slab == NULL) {
                  slab = uma_dbg_getslab(zone, item);
                  if (slab == NULL) 
                          panic("uma: item %p did not belong to zone %s",
                              item, zone->uz_name);
          }
          keg = zone->uz_keg;
          freei = slab_item_index(slab, keg, item);
  
          if (BIT_TEST_SET_ATOMIC(keg->uk_ipers, freei,
              slab_dbg_bits(slab, keg)))
                  panic("Duplicate alloc of %p from zone %p(%s) slab %p(%d)",
                      item, zone, zone->uz_name, slab, freei);
  }
  
  /*
   * Verifies freed addresses.  Checks for alignment, valid slab membership
   * and duplicate frees.
   *
   */
  static void
  uma_dbg_free(uma_zone_t zone, uma_slab_t slab, void *item)
  {
          uma_keg_t keg;
          int freei;
  
          if (slab == NULL) {
                  slab = uma_dbg_getslab(zone, item);
                  if (slab == NULL) 
                          panic("uma: Freed item %p did not belong to zone %s",
                              item, zone->uz_name);
          }
          keg = zone->uz_keg;
          freei = slab_item_index(slab, keg, item);
  
          if (freei >= keg->uk_ipers)
                  panic("Invalid free of %p from zone %p(%s) slab %p(%d)",
                      item, zone, zone->uz_name, slab, freei);
  
          if (slab_item(slab, keg, freei) != item)
                  panic("Unaligned free of %p from zone %p(%s) slab %p(%d)",
                      item, zone, zone->uz_name, slab, freei);
  
          if (!BIT_TEST_CLR_ATOMIC(keg->uk_ipers, freei,
              slab_dbg_bits(slab, keg)))
                  panic("Duplicate free of %p from zone %p(%s) slab %p(%d)",
                      item, zone, zone->uz_name, slab, freei);
  }
  #endif /* INVARIANTS */
  
  #ifdef DDB
  static int64_t
  get_uma_stats(uma_keg_t kz, uma_zone_t z, uint64_t *allocs, uint64_t *used,
      uint64_t *sleeps, long *cachefree, uint64_t *xdomain)
  {
          uint64_t frees;
          int i;
  
          if (kz->uk_flags & UMA_ZFLAG_INTERNAL) {
                  *allocs = counter_u64_fetch(z->uz_allocs);
                  frees = counter_u64_fetch(z->uz_frees);
                  *sleeps = z->uz_sleeps;
                  *cachefree = 0;
                  *xdomain = 0;
          } else
                  uma_zone_sumstat(z, cachefree, allocs, &frees, sleeps,
                      xdomain);
          for (i = 0; i < vm_ndomains; i++) {
                  *cachefree += ZDOM_GET(z, i)->uzd_nitems;
                  if (!((z->uz_flags & UMA_ZONE_SECONDARY) &&
                      (LIST_FIRST(&kz->uk_zones) != z)))
                          *cachefree += kz->uk_domain[i].ud_free_items;
          }
          *used = *allocs - frees;
          return (((int64_t)*used + *cachefree) * kz->uk_size);
  }
  
  DB_SHOW_COMMAND(uma, db_show_uma)
  {
          const char *fmt_hdr, *fmt_entry;
          uma_keg_t kz;
          uma_zone_t z;
          uint64_t allocs, used, sleeps, xdomain;
          long cachefree;
          /* variables for sorting */
          uma_keg_t cur_keg;
          uma_zone_t cur_zone, last_zone;
          int64_t cur_size, last_size, size;
          int ties;
  
          /* /i option produces machine-parseable CSV output */
          if (modif[0] == 'i') {
                  fmt_hdr = "%s,%s,%s,%s,%s,%s,%s,%s,%s\n";
                  fmt_entry = "\"%s\",%ju,%jd,%ld,%ju,%ju,%u,%jd,%ju\n";
          } else {
                  fmt_hdr = "%18s %6s %7s %7s %11s %7s %7s %10s %8s\n";
                  fmt_entry = "%18s %6ju %7jd %7ld %11ju %7ju %7u %10jd %8ju\n";
          }
  
          db_printf(fmt_hdr, "Zone", "Size", "Used", "Free", "Requests",
              "Sleeps", "Bucket", "Total Mem", "XFree");
  
          /* Sort the zones with largest size first. */
          last_zone = NULL;
          last_size = INT64_MAX;
          for (;;) {
                  cur_zone = NULL;
                  cur_size = -1;
                  ties = 0;
                  LIST_FOREACH(kz, &uma_kegs, uk_link) {
                          LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                                  /*
                                   * In the case of size ties, print out zones
                                   * in the order they are encountered.  That is,
                                   * when we encounter the most recently output
                                   * zone, we have already printed all preceding
                                   * ties, and we must print all following ties.
                                   */
                                  if (z == last_zone) {
                                          ties = 1;
                                          continue;
                                  }
                                  size = get_uma_stats(kz, z, &allocs, &used,
                                      &sleeps, &cachefree, &xdomain);
                                  if (size > cur_size && size < last_size + ties)
                                  {
                                          cur_size = size;
                                          cur_zone = z;
                                          cur_keg = kz;
                                  }
                          }
                  }
                  if (cur_zone == NULL)
                          break;
  
                  size = get_uma_stats(cur_keg, cur_zone, &allocs, &used,
                      &sleeps, &cachefree, &xdomain);
                  db_printf(fmt_entry, cur_zone->uz_name,
                      (uintmax_t)cur_keg->uk_size, (intmax_t)used, cachefree,
                      (uintmax_t)allocs, (uintmax_t)sleeps,
                      (unsigned)cur_zone->uz_bucket_size, (intmax_t)size,
                      xdomain);
  
                  if (db_pager_quit)
                          return;
                  last_zone = cur_zone;
                  last_size = cur_size;
          }
  }
  
  DB_SHOW_COMMAND(umacache, db_show_umacache)
  {
          uma_zone_t z;
          uint64_t allocs, frees;
          long cachefree;
          int i;
  
          db_printf("%18s %8s %8s %8s %12s %8s\n", "Zone", "Size", "Used", "Free",
              "Requests", "Bucket");
          LIST_FOREACH(z, &uma_cachezones, uz_link) {
                  uma_zone_sumstat(z, &cachefree, &allocs, &frees, NULL, NULL);
                  for (i = 0; i < vm_ndomains; i++)
                          cachefree += ZDOM_GET(z, i)->uzd_nitems;
                  db_printf("%18s %8ju %8jd %8ld %12ju %8u\n",
                      z->uz_name, (uintmax_t)z->uz_size,
                      (intmax_t)(allocs - frees), cachefree,
                      (uintmax_t)allocs, z->uz_bucket_size);
                  if (db_pager_quit)
                          return;
          }
  }
  #endif  /* DDB */