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

     /*-
      * Copyright (c) 2002-2005, 2009, 2013 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
     * effecient.  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: releng/10.0/sys/vm/uma_core.c 258911 2013-12-04 07:46:53Z rodrigc $");
    
    /* I should really use ktr.. */
    /*
    #define UMA_DEBUG 1
    #define UMA_DEBUG_ALLOC 1
    #define UMA_DEBUG_ALLOC_1 1
    */
    
    #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/kernel.h>
    #include <sys/types.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/rwlock.h>
    #include <sys/sbuf.h>
    #include <sys/smp.h>
    #include <sys/vmmeter.h>
    
    #include <vm/vm.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_param.h>
    #include <vm/vm_map.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.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
    
    /*
    * This is the zone and keg from which all zones are spawned.  The idea is that
    * even the zone & keg heads are allocated from the allocator, so we use the
    * bss section to bootstrap us.
    */
   static struct uma_keg masterkeg;
   static struct uma_zone masterzone_k;
   static struct uma_zone masterzone_z;
   static uma_zone_t kegs = &masterzone_k;
   static uma_zone_t zones = &masterzone_z;
   
   /* This is the zone from which all of uma_slab_t's are allocated. */
   static uma_zone_t slabzone;
   static uma_zone_t slabrefzone;  /* With refcounters (for UMA_ZONE_REFCNT) */
   
   /*
    * 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");
   
   /*
    * 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);
   
   /* This mutex protects the keg list */
   static struct mtx_padalign uma_mtx;
   
   /* Linked list of boot time pages */
   static LIST_HEAD(,uma_slab) uma_boot_pages =
       LIST_HEAD_INITIALIZER(uma_boot_pages);
   
   /* This mutex protects the boot time pages list */
   static struct mtx_padalign uma_boot_pages_mtx;
   
   /* Is the VM done starting up? */
   static int booted = 0;
   #define UMA_STARTUP     1
   #define UMA_STARTUP2    2
   
   /* Maximum number of allowed items-per-slab if the slab header is OFFPAGE */
   static const u_int uma_max_ipers = SLAB_SETSIZE;
   
   /*
    * Only mbuf clusters use ref zones.  Just provide enough references
    * to support the one user.  New code should not use the ref facility.
    */
   static const u_int uma_max_ipers_ref = PAGE_SIZE / MCLBYTES;
   
   /*
    * 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;
           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(128)
   
   struct uma_bucket_zone bucket_zones[] = {
           { NULL, "4 Bucket", BUCKET_SIZE(4), 4096 },
           { NULL, "8 Bucket", BUCKET_SIZE(8), 2048 },
           { NULL, "16 Bucket", BUCKET_SIZE(16), 1024 },
           { NULL, "32 Bucket", BUCKET_SIZE(32), 512 },
           { NULL, "64 Bucket", BUCKET_SIZE(64), 256 },
           { NULL, "128 Bucket", BUCKET_SIZE(128), 128 },
           { NULL, NULL, 0}
   };
   
   /*
    * Flags and enumerations to be passed to internal functions.
    */
   enum zfreeskip { SKIP_NONE = 0, SKIP_DTOR, SKIP_FINI };
   
   /* Prototypes.. */
   
   static void *noobj_alloc(uma_zone_t, int, uint8_t *, int);
   static void *page_alloc(uma_zone_t, int, uint8_t *, int);
   static void *startup_alloc(uma_zone_t, int, uint8_t *, int);
   static void page_free(void *, int, uint8_t);
   static uma_slab_t keg_alloc_slab(uma_keg_t, uma_zone_t, int);
   static void cache_drain(uma_zone_t);
   static void bucket_drain(uma_zone_t, uma_bucket_t);
   static void bucket_cache_drain(uma_zone_t zone);
   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 int zero_init(void *, int, int);
   static void keg_small_init(uma_keg_t keg);
   static void keg_large_init(uma_keg_t keg);
   static void zone_foreach(void (*zfunc)(uma_zone_t));
   static void zone_timeout(uma_zone_t zone);
   static int hash_alloc(struct uma_hash *);
   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_startup3(void);
   static void *zone_alloc_item(uma_zone_t, void *, int);
   static void zone_free_item(uma_zone_t, void *, void *, enum zfreeskip);
   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 zone, void *, int flags);
   static uma_slab_t zone_fetch_slab(uma_zone_t zone, uma_keg_t last, int flags);
   static uma_slab_t zone_fetch_slab_multi(uma_zone_t zone, uma_keg_t last, int flags);
   static void *slab_alloc_item(uma_keg_t keg, uma_slab_t slab);
   static void slab_free_item(uma_keg_t keg, 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(uma_zone_t zone, void **bucket, int max, int flags);
   static void zone_release(uma_zone_t zone, void **bucket, int cnt);
   
   void uma_print_zone(uma_zone_t);
   void uma_print_stats(void);
   static int sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS);
   static int sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS);
   
   SYSINIT(uma_startup3, SI_SUB_VM_CONF, SI_ORDER_SECOND, uma_startup3, NULL);
   
   SYSCTL_PROC(_vm, OID_AUTO, zone_count, CTLFLAG_RD|CTLTYPE_INT,
       0, 0, sysctl_vm_zone_count, "I", "Number of UMA zones");
   
   SYSCTL_PROC(_vm, OID_AUTO, zone_stats, CTLFLAG_RD|CTLTYPE_STRUCT,
       0, 0, sysctl_vm_zone_stats, "s,struct uma_type_header", "Zone Stats");
   
   static int zone_warnings = 1;
   TUNABLE_INT("vm.zone_warnings", &zone_warnings);
   SYSCTL_INT(_vm, OID_AUTO, zone_warnings, CTLFLAG_RW, &zone_warnings, 0,
       "Warn when UMA zones becomes full");
   
   /*
    * This routine checks to see whether or not it's safe to enable buckets.
    */
   static void
   bucket_enable(void)
   {
           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;
           int i;
   
           for (i = 0, 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);
           }
   }
   
   /*
    * 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;
   
           /*
            * This is to stop us from allocating per cpu buckets while we're
            * running out of vm.boot_pages.  Otherwise, we would exhaust the
            * boot pages.  This also prevents us from allocating buckets in
            * low memory situations.
            */
           if (bucketdisable)
                   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 ((uintptr_t)udata & UMA_ZFLAG_BUCKET)
                   return (NULL);
           if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
                   udata = (void *)(uintptr_t)zone->uz_flags;
           else
                   udata = (void *)((uintptr_t)udata | UMA_ZFLAG_BUCKET);
           if ((uintptr_t)udata & UMA_ZFLAG_CACHEONLY)
                   flags |= M_NOVM;
           ubz = bucket_zone_lookup(zone->uz_count);
           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 = ubz->ubz_entries;
           }
   
           return (bucket);
   }
   
   static void
   bucket_free(uma_zone_t zone, uma_bucket_t bucket, void *udata)
   {
           struct uma_bucket_zone *ubz;
   
           KASSERT(bucket->ub_cnt == 0,
               ("bucket_free: Freeing a non free 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++)
                   zone_drain(ubz->ubz_zone);
   }
   
   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 void
   zone_foreach_keg(uma_zone_t zone, void (*kegfn)(uma_keg_t))
   {
           uma_klink_t klink;
   
           LIST_FOREACH(klink, &zone->uz_kegs, kl_link)
                   kegfn(klink->kl_keg);
   }
   
   /*
    * 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);
   
           /* Reschedule this event */
           callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
   }
   
   /*
    * Routine to perform timeout driven calculations.  This expands the
    * hashes and does per cpu statistics aggregation.
    *
    *  Returns nothing.
    */
   static void
   keg_timeout(uma_keg_t keg)
   {
   
           KEG_LOCK(keg);
           /*
            * 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 (keg->uk_flags & UMA_ZONE_HASH &&
               keg->uk_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.
                    */
                   newhash = keg->uk_hash;
                   KEG_UNLOCK(keg);
                   ret = hash_alloc(&newhash);
                   KEG_LOCK(keg);
                   if (ret) {
                           if (hash_expand(&keg->uk_hash, &newhash)) {
                                   oldhash = keg->uk_hash;
                                   keg->uk_hash = newhash;
                           } else
                                   oldhash = newhash;
   
                           KEG_UNLOCK(keg);
                           hash_free(&oldhash);
                           return;
                   }
           }
           KEG_UNLOCK(keg);
   }
   
   static void
   zone_timeout(uma_zone_t zone)
   {
   
           zone_foreach_keg(zone, &keg_timeout);
   }
   
   /*
    * 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 sucess and 0 on failure.
    */
   static int
   hash_alloc(struct uma_hash *hash)
   {
           int oldsize;
           int alloc;
   
           oldsize = hash->uh_hashsize;
   
           /* We're just going to go to a power of two greater */
           if (oldsize)  {
                   hash->uh_hashsize = oldsize * 2;
                   alloc = sizeof(hash->uh_slab_hash[0]) * hash->uh_hashsize;
                   hash->uh_slab_hash = (struct slabhead *)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,
                       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_slab_t slab;
           int hval;
           int i;
   
           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 (i = 0; i < oldhash->uh_hashsize; i++)
                   while (!SLIST_EMPTY(&oldhash->uh_slab_hash[i])) {
                           slab = SLIST_FIRST(&oldhash->uh_slab_hash[i]);
                           SLIST_REMOVE_HEAD(&oldhash->uh_slab_hash[i], us_hlink);
                           hval = UMA_HASH(newhash, slab->us_data);
                           SLIST_INSERT_HEAD(&newhash->uh_slab_hash[hval],
                               slab, us_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, cpu queue must be locked.
    *
    * Returns:
    *      Nothing
    */
   
   static void
   bucket_drain(uma_zone_t zone, uma_bucket_t bucket)
   {
           int i;
   
           if (bucket == NULL)
                   return;
   
           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);
           bucket->ub_cnt = 0;
   }
   
   /*
    * Drains the per cpu caches for a zone.
    *
    * NOTE: This may only be called while the zone is being turn 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;
           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().
            *
            * XXX: We lock the zone before passing into bucket_cache_drain() as
            * it is used elsewhere.  Should the tear-down path be made special
            * there in some form?
            */
           CPU_FOREACH(cpu) {
                   cache = &zone->uz_cpu[cpu];
                   bucket_drain(zone, cache->uc_allocbucket);
                   bucket_drain(zone, cache->uc_freebucket);
                   if (cache->uc_allocbucket != NULL)
                           bucket_free(zone, cache->uc_allocbucket, NULL);
                   if (cache->uc_freebucket != NULL)
                           bucket_free(zone, cache->uc_freebucket, NULL);
                   cache->uc_allocbucket = cache->uc_freebucket = NULL;
           }
           ZONE_LOCK(zone);
           bucket_cache_drain(zone);
           ZONE_UNLOCK(zone);
   }
   
   /*
    * Drain the cached buckets from a zone.  Expects a locked zone on entry.
    */
   static void
   bucket_cache_drain(uma_zone_t zone)
   {
           uma_bucket_t bucket;
   
           /*
            * Drain the bucket queues and free the buckets, we just keep two per
            * cpu (alloc/free).
            */
           while ((bucket = LIST_FIRST(&zone->uz_buckets)) != NULL) {
                   LIST_REMOVE(bucket, ub_link);
                   ZONE_UNLOCK(zone);
                   bucket_drain(zone, bucket);
                   bucket_free(zone, bucket, NULL);
                   ZONE_LOCK(zone);
           }
   }
   
   static void
   keg_free_slab(uma_keg_t keg, uma_slab_t slab, int start)
   {
           uint8_t *mem;
           int i;
           uint8_t flags;
   
           mem = slab->us_data;
           flags = slab->us_flags;
           i = start;
           if (keg->uk_fini != NULL) {
                   for (i--; i > -1; i--)
                           keg->uk_fini(slab->us_data + (keg->uk_rsize * i),
                               keg->uk_size);
           }
           if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                   zone_free_item(keg->uk_slabzone, slab, NULL, SKIP_NONE);
   #ifdef UMA_DEBUG
           printf("%s: Returning %d bytes.\n", keg->uk_name,
               PAGE_SIZE * keg->uk_ppera);
   #endif
           keg->uk_freef(mem, PAGE_SIZE * keg->uk_ppera, flags);
   }
   
   /*
    * 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)
   {
           struct slabhead freeslabs = { 0 };
           uma_slab_t slab;
           uma_slab_t n;
   
           /*
            * We don't want to take pages from statically allocated kegs at this
            * time
            */
           if (keg->uk_flags & UMA_ZONE_NOFREE || keg->uk_freef == NULL)
                   return;
   
   #ifdef UMA_DEBUG
           printf("%s free items: %u\n", keg->uk_name, keg->uk_free);
   #endif
           KEG_LOCK(keg);
           if (keg->uk_free == 0)
                   goto finished;
   
           slab = LIST_FIRST(&keg->uk_free_slab);
           while (slab) {
                   n = LIST_NEXT(slab, us_link);
   
                   /* We have no where to free these to */
                   if (slab->us_flags & UMA_SLAB_BOOT) {
                           slab = n;
                           continue;
                   }
   
                   LIST_REMOVE(slab, us_link);
                   keg->uk_pages -= keg->uk_ppera;
                   keg->uk_free -= keg->uk_ipers;
   
                   if (keg->uk_flags & UMA_ZONE_HASH)
                           UMA_HASH_REMOVE(&keg->uk_hash, slab, slab->us_data);
   
                   SLIST_INSERT_HEAD(&freeslabs, slab, us_hlink);
   
                   slab = n;
           }
   finished:
           KEG_UNLOCK(keg);
   
           while ((slab = SLIST_FIRST(&freeslabs)) != NULL) {
                   SLIST_REMOVE(&freeslabs, slab, uma_slab, us_hlink);
                   keg_free_slab(keg, slab, keg->uk_ipers);
           }
   }
   
   static void
   zone_drain_wait(uma_zone_t zone, int waitok)
   {
   
           /*
            * 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_DRAINING) {
                   if (waitok == M_NOWAIT)
                           goto out;
                   mtx_unlock(&uma_mtx);
                   msleep(zone, zone->uz_lockptr, PVM, "zonedrain", 1);
                   mtx_lock(&uma_mtx);
           }
           zone->uz_flags |= UMA_ZFLAG_DRAINING;
           bucket_cache_drain(zone);
           ZONE_UNLOCK(zone);
           /*
            * The DRAINING flag protects us from being freed while
            * we're running.  Normally the uma_mtx would protect us but we
            * must be able to release and acquire the right lock for each keg.
            */
           zone_foreach_keg(zone, &keg_drain);
           ZONE_LOCK(zone);
           zone->uz_flags &= ~UMA_ZFLAG_DRAINING;
           wakeup(zone);
   out:
           ZONE_UNLOCK(zone);
   }
   
   void
   zone_drain(uma_zone_t zone)
   {
   
           zone_drain_wait(zone, M_NOWAIT);
   }
   
   /*
    * Allocate a new slab for a keg.  This does not insert the slab onto a list.
    *
    * Arguments:
    *      wait  Shall we wait?
    *
    * 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 wait)
   {
           uma_slabrefcnt_t slabref;
           uma_alloc allocf;
           uma_slab_t slab;
           uint8_t *mem;
           uint8_t flags;
           int i;
   
           mtx_assert(&keg->uk_lock, MA_OWNED);
           slab = NULL;
           mem = NULL;
   
   #ifdef UMA_DEBUG
           printf("alloc_slab:  Allocating a new slab for %s\n", keg->uk_name);
   #endif
           allocf = keg->uk_allocf;
           KEG_UNLOCK(keg);
   
           if (keg->uk_flags & UMA_ZONE_OFFPAGE) {
                   slab = zone_alloc_item(keg->uk_slabzone, NULL, wait);
                   if (slab == NULL)
                           goto out;
           }
   
           /*
            * 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)
                   wait |= M_ZERO;
           else
                   wait &= ~M_ZERO;
   
           if (keg->uk_flags & UMA_ZONE_NODUMP)
                   wait |= M_NODUMP;
   
           /* zone is passed for legacy reasons. */
           mem = allocf(zone, keg->uk_ppera * PAGE_SIZE, &flags, wait);
           if (mem == NULL) {
                   if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                           zone_free_item(keg->uk_slabzone, slab, NULL, SKIP_NONE);
                   slab = NULL;
                   goto out;
           }
   
           /* Point the slab into the allocated memory */
           if (!(keg->uk_flags & UMA_ZONE_OFFPAGE))
                   slab = (uma_slab_t )(mem + keg->uk_pgoff);
   
           if (keg->uk_flags & UMA_ZONE_VTOSLAB)
                   for (i = 0; i < keg->uk_ppera; i++)
                           vsetslab((vm_offset_t)mem + (i * PAGE_SIZE), slab);
   
           slab->us_keg = keg;
           slab->us_data = mem;
           slab->us_freecount = keg->uk_ipers;
           slab->us_flags = flags;
           BIT_FILL(SLAB_SETSIZE, &slab->us_free);
   #ifdef INVARIANTS
           BIT_ZERO(SLAB_SETSIZE, &slab->us_debugfree);
   #endif
           if (keg->uk_flags & UMA_ZONE_REFCNT) {
                   slabref = (uma_slabrefcnt_t)slab;
                   for (i = 0; i < keg->uk_ipers; i++)
                           slabref->us_refcnt[i] = 0;
           }
   
           if (keg->uk_init != NULL) {
                   for (i = 0; i < keg->uk_ipers; i++)
                           if (keg->uk_init(slab->us_data + (keg->uk_rsize * i),
                               keg->uk_size, wait) != 0)
                                   break;
                   if (i != keg->uk_ipers) {
                           keg_free_slab(keg, slab, i);
                           slab = NULL;
                           goto out;
                   }
           }
   out:
           KEG_LOCK(keg);
   
           if (slab != NULL) {
                   if (keg->uk_flags & UMA_ZONE_HASH)
                           UMA_HASH_INSERT(&keg->uk_hash, slab, mem);
   
                   keg->uk_pages += keg->uk_ppera;
                   keg->uk_free += keg->uk_ipers;
           }
   
           return (slab);
   }
   
   /*
    * 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, int bytes, uint8_t *pflag, int wait)
   {
           uma_keg_t keg;
           uma_slab_t tmps;
           int pages, check_pages;
   
           keg = zone_first_keg(zone);
           pages = howmany(bytes, PAGE_SIZE);
           check_pages = pages - 1;
           KASSERT(pages > 0, ("startup_alloc can't reserve 0 pages\n"));
   
           /*
            * Check our small startup cache to see if it has pages remaining.
            */
           mtx_lock(&uma_boot_pages_mtx);
   
           /* First check if we have enough room. */
           tmps = LIST_FIRST(&uma_boot_pages);
           while (tmps != NULL && check_pages-- > 0)
                   tmps = LIST_NEXT(tmps, us_link);
           if (tmps != NULL) {
                   /*
                    * It's ok to lose tmps references.  The last one will
                    * have tmps->us_data pointing to the start address of
                    * "pages" contiguous pages of memory.
                    */
                   while (pages-- > 0) {
                           tmps = LIST_FIRST(&uma_boot_pages);
                           LIST_REMOVE(tmps, us_link);
                   }
                   mtx_unlock(&uma_boot_pages_mtx);
                   *pflag = tmps->us_flags;
                   return (tmps->us_data);
           }
           mtx_unlock(&uma_boot_pages_mtx);
           if (booted < UMA_STARTUP2)
                   panic("UMA: Increase vm.boot_pages");
           /*
            * Now that we've booted reset these users to their real allocator.
            */
   #ifdef UMA_MD_SMALL_ALLOC
           keg->uk_allocf = (keg->uk_ppera > 1) ? page_alloc : uma_small_alloc;
   #else
           keg->uk_allocf = page_alloc;
   #endif
           return keg->uk_allocf(zone, bytes, pflag, wait);
   }
   
   /*
    * 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, int bytes, uint8_t *pflag, int wait)
  {
          void *p;        /* Returned page */
  
          *pflag = UMA_SLAB_KMEM;
          p = (void *) kmem_malloc(kmem_arena, bytes, wait);
  
          return (p);
  }
  
  /*
   * 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, int bytes, 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_first_keg(zone);
  
          npages = howmany(bytes, PAGE_SIZE);
          while (npages > 0) {
                  p = vm_page_alloc(NULL, 0, VM_ALLOC_INTERRUPT |
                      VM_ALLOC_WIRED | VM_ALLOC_NOOBJ);
                  if (p != NULL) {
                          /*
                           * Since the page does not belong to an object, its
                           * listq is unused.
                           */
                          TAILQ_INSERT_TAIL(&alloctail, p, listq);
                          npages--;
                          continue;
                  }
                  if (wait & M_WAITOK) {
                          VM_WAIT;
                          continue;
                  }
  
                  /*
                   * Page allocation failed, free intermediate pages and
                   * exit.
                   */
                  TAILQ_FOREACH_SAFE(p, &alloctail, listq, p_next) {
                          vm_page_unwire(p, 0);
                          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);
  }
  
  /*
   * 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, int size, uint8_t flags)
  {
          struct vmem *vmem;
  
          if (flags & UMA_SLAB_KMEM)
                  vmem = kmem_arena;
          else if (flags & UMA_SLAB_KERNEL)
                  vmem = kernel_arena;
          else
                  panic("UMA: page_free used with invalid flags %d", flags);
  
          kmem_free(vmem, (vm_offset_t)mem, 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);
  }
  
  /*
   * Finish creating a small uma keg.  This calculates ipers, and the keg size.
   *
   * Arguments
   *      keg  The zone we should initialize
   *
   * Returns
   *      Nothing
   */
  static void
  keg_small_init(uma_keg_t keg)
  {
          u_int rsize;
          u_int memused;
          u_int wastedspace;
          u_int shsize;
  
          if (keg->uk_flags & UMA_ZONE_PCPU) {
                  u_int ncpus = mp_ncpus ? mp_ncpus : MAXCPU;
  
                  keg->uk_slabsize = sizeof(struct pcpu);
                  keg->uk_ppera = howmany(ncpus * sizeof(struct pcpu),
                      PAGE_SIZE);
          } else {
                  keg->uk_slabsize = UMA_SLAB_SIZE;
                  keg->uk_ppera = 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 = keg->uk_size;
          if (rsize < keg->uk_slabsize / SLAB_SETSIZE)
                  rsize = keg->uk_slabsize / SLAB_SETSIZE;
          if (rsize & keg->uk_align)
                  rsize = (rsize & ~keg->uk_align) + (keg->uk_align + 1);
          keg->uk_rsize = rsize;
  
          KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0 ||
              keg->uk_rsize < sizeof(struct pcpu),
              ("%s: size %u too large", __func__, keg->uk_rsize));
  
          if (keg->uk_flags & UMA_ZONE_REFCNT)
                  rsize += sizeof(uint32_t);
  
          if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                  shsize = 0;
          else 
                  shsize = sizeof(struct uma_slab);
  
          keg->uk_ipers = (keg->uk_slabsize - shsize) / rsize;
          KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
              ("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
  
          memused = keg->uk_ipers * rsize + shsize;
          wastedspace = keg->uk_slabsize - memused;
  
          /*
           * 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_ZFLAG_CACHEONLY as a result
           * of UMA_ZONE_VM, which clearly forbids it.
           */
          if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) ||
              (keg->uk_flags & UMA_ZFLAG_CACHEONLY))
                  return;
  
          /*
           * See if using an OFFPAGE slab will limit our waste.  Only do
           * this if it permits more items per-slab.
           *
           * XXX We could try growing slabsize to limit max waste as well.
           * Historically this was not done because the VM could not
           * efficiently handle contiguous allocations.
           */
          if ((wastedspace >= keg->uk_slabsize / UMA_MAX_WASTE) &&
              (keg->uk_ipers < (keg->uk_slabsize / keg->uk_rsize))) {
                  keg->uk_ipers = keg->uk_slabsize / keg->uk_rsize;
                  KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
                      ("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
  #ifdef UMA_DEBUG
                  printf("UMA decided we need offpage slab headers for "
                      "keg: %s, calculated wastedspace = %d, "
                      "maximum wasted space allowed = %d, "
                      "calculated ipers = %d, "
                      "new wasted space = %d\n", keg->uk_name, wastedspace,
                      keg->uk_slabsize / UMA_MAX_WASTE, keg->uk_ipers,
                      keg->uk_slabsize - keg->uk_ipers * keg->uk_rsize);
  #endif
                  keg->uk_flags |= UMA_ZONE_OFFPAGE;
          }
  
          if ((keg->uk_flags & UMA_ZONE_OFFPAGE) &&
              (keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
                  keg->uk_flags |= UMA_ZONE_HASH;
  }
  
  /*
   * Finish creating a large (> UMA_SLAB_SIZE) uma kegs.  Just give in and do
   * OFFPAGE for now.  When I can allow for more dynamic slab sizes this will be
   * more complicated.
   *
   * Arguments
   *      keg  The keg we should initialize
   *
   * Returns
   *      Nothing
   */
  static void
  keg_large_init(uma_keg_t keg)
  {
  
          KASSERT(keg != NULL, ("Keg is null in keg_large_init"));
          KASSERT((keg->uk_flags & UMA_ZFLAG_CACHEONLY) == 0,
              ("keg_large_init: Cannot large-init a UMA_ZFLAG_CACHEONLY keg"));
          KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
              ("%s: Cannot large-init a UMA_ZONE_PCPU keg", __func__));
  
          keg->uk_ppera = howmany(keg->uk_size, PAGE_SIZE);
          keg->uk_slabsize = keg->uk_ppera * PAGE_SIZE;
          keg->uk_ipers = 1;
          keg->uk_rsize = keg->uk_size;
  
          /* We can't do OFFPAGE if we're internal, bail out here. */
          if (keg->uk_flags & UMA_ZFLAG_INTERNAL)
                  return;
  
          keg->uk_flags |= UMA_ZONE_OFFPAGE;
          if ((keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
                  keg->uk_flags |= UMA_ZONE_HASH;
  }
  
  static void
  keg_cachespread_init(uma_keg_t keg)
  {
          int alignsize;
          int trailer;
          int pages;
          int rsize;
  
          KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
              ("%s: Cannot cachespread-init a UMA_ZONE_PCPU keg", __func__));
  
          alignsize = keg->uk_align + 1;
          rsize = keg->uk_size;
          /*
           * 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 & keg->uk_align)
                  rsize = (rsize & ~keg->uk_align) + alignsize;
          if ((rsize & alignsize) == 0)
                  rsize += alignsize;
          trailer = rsize - keg->uk_size;
          pages = (rsize * (PAGE_SIZE / alignsize)) / PAGE_SIZE;
          pages = MIN(pages, (128 * 1024) / PAGE_SIZE);
          keg->uk_rsize = rsize;
          keg->uk_ppera = pages;
          keg->uk_slabsize = UMA_SLAB_SIZE;
          keg->uk_ipers = ((pages * PAGE_SIZE) + trailer) / rsize;
          keg->uk_flags |= UMA_ZONE_OFFPAGE | UMA_ZONE_VTOSLAB;
          KASSERT(keg->uk_ipers <= uma_max_ipers,
              ("%s: keg->uk_ipers too high(%d) increase max_ipers", __func__,
              keg->uk_ipers));
  }
  
  /*
   * 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;
  
          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_free = 0;
          keg->uk_reserve = 0;
          keg->uk_pages = 0;
          keg->uk_flags = arg->flags;
          keg->uk_allocf = page_alloc;
          keg->uk_freef = page_free;
          keg->uk_slabzone = NULL;
  
          /*
           * The master zone is passed to us at keg-creation time.
           */
          zone = arg->zone;
          keg->uk_name = zone->uz_name;
  
          if (arg->flags & UMA_ZONE_VM)
                  keg->uk_flags |= UMA_ZFLAG_CACHEONLY;
  
          if (arg->flags & UMA_ZONE_ZINIT)
                  keg->uk_init = zero_init;
  
          if (arg->flags & UMA_ZONE_REFCNT || arg->flags & UMA_ZONE_MALLOC)
                  keg->uk_flags |= UMA_ZONE_VTOSLAB;
  
          if (arg->flags & UMA_ZONE_PCPU)
  #ifdef SMP
                  keg->uk_flags |= UMA_ZONE_OFFPAGE;
  #else
                  keg->uk_flags &= ~UMA_ZONE_PCPU;
  #endif
  
          if (keg->uk_flags & UMA_ZONE_CACHESPREAD) {
                  keg_cachespread_init(keg);
          } else if (keg->uk_flags & UMA_ZONE_REFCNT) {
                  if (keg->uk_size >
                      (UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt) -
                      sizeof(uint32_t)))
                          keg_large_init(keg);
                  else
                          keg_small_init(keg);
          } else {
                  if (keg->uk_size > (UMA_SLAB_SIZE - sizeof(struct uma_slab)))
                          keg_large_init(keg);
                  else
                          keg_small_init(keg);
          }
  
          if (keg->uk_flags & UMA_ZONE_OFFPAGE) {
                  if (keg->uk_flags & UMA_ZONE_REFCNT) {
                          if (keg->uk_ipers > uma_max_ipers_ref)
                                  panic("Too many ref items per zone: %d > %d\n",
                                      keg->uk_ipers, uma_max_ipers_ref);
                          keg->uk_slabzone = slabrefzone;
                  } else
                          keg->uk_slabzone = slabzone;
          }
  
          /*
           * If we haven't booted yet we need allocations to go through the
           * startup cache until the vm is ready.
           */
          if (keg->uk_ppera == 1) {
  #ifdef UMA_MD_SMALL_ALLOC
                  keg->uk_allocf = uma_small_alloc;
                  keg->uk_freef = uma_small_free;
  
                  if (booted < UMA_STARTUP)
                          keg->uk_allocf = startup_alloc;
  #else
                  if (booted < UMA_STARTUP2)
                          keg->uk_allocf = startup_alloc;
  #endif
          } else if (booted < UMA_STARTUP2 &&
              (keg->uk_flags & UMA_ZFLAG_INTERNAL))
                  keg->uk_allocf = startup_alloc;
  
          /*
           * Initialize keg's lock
           */
          KEG_LOCK_INIT(keg, (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.  This calculates a right
           * justified offset into the memory on an ALIGN_PTR boundary.
           */
          if (!(keg->uk_flags & UMA_ZONE_OFFPAGE)) {
                  u_int totsize;
  
                  /* Size of the slab struct and free list */
                  totsize = sizeof(struct uma_slab);
  
                  /* Size of the reference counts. */
                  if (keg->uk_flags & UMA_ZONE_REFCNT)
                          totsize += keg->uk_ipers * sizeof(uint32_t);
  
                  if (totsize & UMA_ALIGN_PTR)
                          totsize = (totsize & ~UMA_ALIGN_PTR) +
                              (UMA_ALIGN_PTR + 1);
                  keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - totsize;
  
                  /*
                   * 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.
                   */
                  totsize = keg->uk_pgoff + sizeof(struct uma_slab);
                  if (keg->uk_flags & UMA_ZONE_REFCNT)
                          totsize += keg->uk_ipers * sizeof(uint32_t);
                  if (totsize > PAGE_SIZE * keg->uk_ppera) {
                          printf("zone %s ipers %d rsize %d size %d\n",
                              zone->uz_name, keg->uk_ipers, keg->uk_rsize,
                              keg->uk_size);
                          panic("UMA slab won't fit.");
                  }
          }
  
          if (keg->uk_flags & UMA_ZONE_HASH)
                  hash_alloc(&keg->uk_hash);
  
  #ifdef UMA_DEBUG
          printf("UMA: %s(%p) size %d(%d) flags %#x ipers %d ppera %d out %d free %d\n",
              zone->uz_name, zone, keg->uk_size, keg->uk_rsize, keg->uk_flags,
              keg->uk_ipers, keg->uk_ppera,
              (keg->uk_ipers * keg->uk_pages) - keg->uk_free, keg->uk_free);
  #endif
  
          LIST_INSERT_HEAD(&keg->uk_zones, zone, uz_link);
  
          mtx_lock(&uma_mtx);
          LIST_INSERT_HEAD(&uma_kegs, keg, uk_link);
          mtx_unlock(&uma_mtx);
          return (0);
  }
  
  /*
   * 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_zctor_args *arg = udata;
          uma_zone_t zone = mem;
          uma_zone_t z;
          uma_keg_t keg;
  
          bzero(zone, size);
          zone->uz_name = arg->name;
          zone->uz_ctor = arg->ctor;
          zone->uz_dtor = arg->dtor;
          zone->uz_slab = zone_fetch_slab;
          zone->uz_init = NULL;
          zone->uz_fini = NULL;
          zone->uz_allocs = 0;
          zone->uz_frees = 0;
          zone->uz_fails = 0;
          zone->uz_sleeps = 0;
          zone->uz_count = 0;
          zone->uz_flags = 0;
          zone->uz_warning = NULL;
          timevalclear(&zone->uz_ratecheck);
          keg = arg->keg;
  
          ZONE_LOCK_INIT(zone, (arg->flags & UMA_ZONE_MTXCLASS));
  
          /*
           * This is a pure cache zone, no kegs.
           */
          if (arg->import) {
                  if (arg->flags & UMA_ZONE_VM)
                          arg->flags |= UMA_ZFLAG_CACHEONLY;
                  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;
                  zone->uz_lockptr = &zone->uz_lock;
                  goto out;
          }
  
          /*
           * Use the regular zone/keg/slab allocator.
           */
          zone->uz_import = (uma_import)zone_import;
          zone->uz_release = (uma_release)zone_release;
          zone->uz_arg = zone; 
  
          if (arg->flags & UMA_ZONE_SECONDARY) {
                  KASSERT(arg->keg != NULL, ("Secondary zone on zero'd keg"));
                  zone->uz_init = arg->uminit;
                  zone->uz_fini = arg->fini;
                  zone->uz_lockptr = &keg->uk_lock;
                  zone->uz_flags |= UMA_ZONE_SECONDARY;
                  mtx_lock(&uma_mtx);
                  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);
                  mtx_unlock(&uma_mtx);
          } 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;
                  karg.zone = zone;
                  error = keg_ctor(arg->keg, sizeof(struct uma_keg), &karg,
                      flags);
                  if (error)
                          return (error);
          }
  
          /*
           * Link in the first keg.
           */
          zone->uz_klink.kl_keg = keg;
          LIST_INSERT_HEAD(&zone->uz_kegs, &zone->uz_klink, kl_link);
          zone->uz_lockptr = &keg->uk_lock;
          zone->uz_size = keg->uk_size;
          zone->uz_flags |= (keg->uk_flags &
              (UMA_ZONE_INHERIT | UMA_ZFLAG_INHERIT));
  
          /*
           * Some internal zones don't have room allocated for the per cpu
           * caches.  If we're internal, bail out here.
           */
          if (keg->uk_flags & UMA_ZFLAG_INTERNAL) {
                  KASSERT((zone->uz_flags & UMA_ZONE_SECONDARY) == 0,
                      ("Secondary zone requested UMA_ZFLAG_INTERNAL"));
                  return (0);
          }
  
  out:
          if ((arg->flags & UMA_ZONE_MAXBUCKET) == 0)
                  zone->uz_count = bucket_select(zone->uz_size);
          else
                  zone->uz_count = BUCKET_MAX;
  
          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;
  
          keg = (uma_keg_t)arg;
          KEG_LOCK(keg);
          if (keg->uk_free != 0) {
                  printf("Freed UMA keg (%s) was not empty (%d items). "
                      " Lost %d pages of memory.\n",
                      keg->uk_name ? keg->uk_name : "",
                      keg->uk_free, keg->uk_pages);
          }
          KEG_UNLOCK(keg);
  
          hash_free(&keg->uk_hash);
  
          KEG_LOCK_FINI(keg);
  }
  
  /*
   * Zone header dtor.
   *
   * Arguments/Returns follow uma_dtor specifications
   *      udata  unused
   */
  static void
  zone_dtor(void *arg, int size, void *udata)
  {
          uma_klink_t klink;
          uma_zone_t zone;
          uma_keg_t keg;
  
          zone = (uma_zone_t)arg;
          keg = zone_first_keg(zone);
  
          if (!(zone->uz_flags & UMA_ZFLAG_INTERNAL))
                  cache_drain(zone);
  
          mtx_lock(&uma_mtx);
          LIST_REMOVE(zone, uz_link);
          mtx_unlock(&uma_mtx);
          /*
           * XXX there are some races here where
           * the zone can be drained but zone lock
           * released and then refilled before we
           * remove it... we dont care for now
           */
          zone_drain_wait(zone, M_WAITOK);
          /*
           * Unlink all of our kegs.
           */
          while ((klink = LIST_FIRST(&zone->uz_kegs)) != NULL) {
                  klink->kl_keg = NULL;
                  LIST_REMOVE(klink, kl_link);
                  if (klink == &zone->uz_klink)
                          continue;
                  free(klink, M_TEMP);
          }
          /*
           * We only destroy kegs from non secondary zones.
           */
          if (keg != NULL && (zone->uz_flags & UMA_ZONE_SECONDARY) == 0)  {
                  mtx_lock(&uma_mtx);
                  LIST_REMOVE(keg, uk_link);
                  mtx_unlock(&uma_mtx);
                  zone_free_item(kegs, keg, NULL, SKIP_NONE);
          }
          ZONE_LOCK_FINI(zone);
  }
  
  /*
   * 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))
  {
          uma_keg_t keg;
          uma_zone_t zone;
  
          mtx_lock(&uma_mtx);
          LIST_FOREACH(keg, &uma_kegs, uk_link) {
                  LIST_FOREACH(zone, &keg->uk_zones, uz_link)
                          zfunc(zone);
          }
          mtx_unlock(&uma_mtx);
  }
  
  /* Public functions */
  /* See uma.h */
  void
  uma_startup(void *bootmem, int boot_pages)
  {
          struct uma_zctor_args args;
          uma_slab_t slab;
          u_int slabsize;
          int i;
  
  #ifdef UMA_DEBUG
          printf("Creating uma keg headers zone and keg.\n");
  #endif
          mtx_init(&uma_mtx, "UMA lock", NULL, MTX_DEF);
  
          /* "manually" create the initial zone */
          memset(&args, 0, sizeof(args));
          args.name = "UMA Kegs";
          args.size = sizeof(struct uma_keg);
          args.ctor = keg_ctor;
          args.dtor = keg_dtor;
          args.uminit = zero_init;
          args.fini = NULL;
          args.keg = &masterkeg;
          args.align = 32 - 1;
          args.flags = UMA_ZFLAG_INTERNAL;
          /* The initial zone has no Per cpu queues so it's smaller */
          zone_ctor(kegs, sizeof(struct uma_zone), &args, M_WAITOK);
  
  #ifdef UMA_DEBUG
          printf("Filling boot free list.\n");
  #endif
          for (i = 0; i < boot_pages; i++) {
                  slab = (uma_slab_t)((uint8_t *)bootmem + (i * UMA_SLAB_SIZE));
                  slab->us_data = (uint8_t *)slab;
                  slab->us_flags = UMA_SLAB_BOOT;
                  LIST_INSERT_HEAD(&uma_boot_pages, slab, us_link);
          }
          mtx_init(&uma_boot_pages_mtx, "UMA boot pages", NULL, MTX_DEF);
  
  #ifdef UMA_DEBUG
          printf("Creating uma zone headers zone and keg.\n");
  #endif
          args.name = "UMA Zones";
          args.size = sizeof(struct uma_zone) +
              (sizeof(struct uma_cache) * (mp_maxid + 1));
          args.ctor = zone_ctor;
          args.dtor = zone_dtor;
          args.uminit = zero_init;
          args.fini = NULL;
          args.keg = NULL;
          args.align = 32 - 1;
          args.flags = UMA_ZFLAG_INTERNAL;
          /* The initial zone has no Per cpu queues so it's smaller */
          zone_ctor(zones, sizeof(struct uma_zone), &args, M_WAITOK);
  
  #ifdef UMA_DEBUG
          printf("Initializing pcpu cache locks.\n");
  #endif
  #ifdef UMA_DEBUG
          printf("Creating slab and hash zones.\n");
  #endif
  
          /* Now make a zone for slab headers */
          slabzone = uma_zcreate("UMA Slabs",
                                  sizeof(struct uma_slab),
                                  NULL, NULL, NULL, NULL,
                                  UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);
  
          /*
           * We also create a zone for the bigger slabs with reference
           * counts in them, to accomodate UMA_ZONE_REFCNT zones.
           */
          slabsize = sizeof(struct uma_slab_refcnt);
          slabsize += uma_max_ipers_ref * sizeof(uint32_t);
          slabrefzone = uma_zcreate("UMA RCntSlabs",
                                    slabsize,
                                    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();
  
          booted = UMA_STARTUP;
  
  #ifdef UMA_DEBUG
          printf("UMA startup complete.\n");
  #endif
  }
  
  /* see uma.h */
  void
  uma_startup2(void)
  {
          booted = UMA_STARTUP2;
          bucket_enable();
  #ifdef UMA_DEBUG
          printf("UMA startup2 complete.\n");
  #endif
  }
  
  /*
   * Initialize our callout handle
   *
   */
  
  static void
  uma_startup3(void)
  {
  #ifdef UMA_DEBUG
          printf("Starting callout.\n");
  #endif
          callout_init(&uma_callout, CALLOUT_MPSAFE);
          callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
  #ifdef UMA_DEBUG
          printf("UMA startup3 complete.\n");
  #endif
  }
  
  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, M_WAITOK));
  }
  
  /* 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;
  
          /* 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;
          args.align = align;
          args.flags = flags;
          args.keg = NULL;
  
          return (zone_alloc_item(zones, &args, M_WAITOK));
  }
  
  /* See uma.h */
  uma_zone_t
  uma_zsecond_create(char *name, uma_ctor ctor, uma_dtor dtor,
                      uma_init zinit, uma_fini zfini, uma_zone_t master)
  {
          struct uma_zctor_args args;
          uma_keg_t keg;
  
          keg = zone_first_keg(master);
          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;
  
          /* XXX Attaches only one keg of potentially many. */
          return (zone_alloc_item(zones, &args, M_WAITOK));
  }
  
  /* See uma.h */
  uma_zone_t
  uma_zcache_create(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;
  
          return (zone_alloc_item(zones, &args, M_WAITOK));
  }
  
  static void
  zone_lock_pair(uma_zone_t a, uma_zone_t b)
  {
          if (a < b) {
                  ZONE_LOCK(a);
                  mtx_lock_flags(b->uz_lockptr, MTX_DUPOK);
          } else {
                  ZONE_LOCK(b);
                  mtx_lock_flags(a->uz_lockptr, MTX_DUPOK);
          }
  }
  
  static void
  zone_unlock_pair(uma_zone_t a, uma_zone_t b)
  {
  
          ZONE_UNLOCK(a);
          ZONE_UNLOCK(b);
  }
  
  int
  uma_zsecond_add(uma_zone_t zone, uma_zone_t master)
  {
          uma_klink_t klink;
          uma_klink_t kl;
          int error;
  
          error = 0;
          klink = malloc(sizeof(*klink), M_TEMP, M_WAITOK | M_ZERO);
  
          zone_lock_pair(zone, master);
          /*
           * zone must use vtoslab() to resolve objects and must already be
           * a secondary.
           */
          if ((zone->uz_flags & (UMA_ZONE_VTOSLAB | UMA_ZONE_SECONDARY))
              != (UMA_ZONE_VTOSLAB | UMA_ZONE_SECONDARY)) {
                  error = EINVAL;
                  goto out;
          }
          /*
           * The new master must also use vtoslab().
           */
          if ((zone->uz_flags & UMA_ZONE_VTOSLAB) != UMA_ZONE_VTOSLAB) {
                  error = EINVAL;
                  goto out;
          }
          /*
           * Both must either be refcnt, or not be refcnt.
           */
          if ((zone->uz_flags & UMA_ZONE_REFCNT) !=
              (master->uz_flags & UMA_ZONE_REFCNT)) {
                  error = EINVAL;
                  goto out;
          }
          /*
           * The underlying object must be the same size.  rsize
           * may be different.
           */
          if (master->uz_size != zone->uz_size) {
                  error = E2BIG;
                  goto out;
          }
          /*
           * Put it at the end of the list.
           */
          klink->kl_keg = zone_first_keg(master);
          LIST_FOREACH(kl, &zone->uz_kegs, kl_link) {
                  if (LIST_NEXT(kl, kl_link) == NULL) {
                          LIST_INSERT_AFTER(kl, klink, kl_link);
                          break;
                  }
          }
          klink = NULL;
          zone->uz_flags |= UMA_ZFLAG_MULTI;
          zone->uz_slab = zone_fetch_slab_multi;
  
  out:
          zone_unlock_pair(zone, master);
          if (klink != NULL)
                  free(klink, M_TEMP);
  
          return (error);
  }
  
  
  /* See uma.h */
  void
  uma_zdestroy(uma_zone_t zone)
  {
  
          zone_free_item(zones, zone, NULL, SKIP_NONE);
  }
  
  /* See uma.h */
  void *
  uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
  {
          void *item;
          uma_cache_t cache;
          uma_bucket_t bucket;
          int lockfail;
          int cpu;
  
          /* This is the fast path allocation */
  #ifdef UMA_DEBUG_ALLOC_1
          printf("Allocating one item from %s(%p)\n", zone->uz_name, zone);
  #endif
          CTR3(KTR_UMA, "uma_zalloc_arg thread %x zone %s flags %d", curthread,
              zone->uz_name, flags);
  
          if (flags & M_WAITOK) {
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "uma_zalloc_arg: zone \"%s\"", zone->uz_name);
          }
  #ifdef DEBUG_MEMGUARD
          if (memguard_cmp_zone(zone)) {
                  item = memguard_alloc(zone->uz_size, flags);
                  if (item != NULL) {
                          /*
                           * Avoid conflict with the use-after-free
                           * protecting infrastructure from INVARIANTS.
                           */
                          if (zone->uz_init != NULL &&
                              zone->uz_init != mtrash_init &&
                              zone->uz_init(item, zone->uz_size, flags) != 0)
                                  return (NULL);
                          if (zone->uz_ctor != NULL &&
                              zone->uz_ctor != mtrash_ctor &&
                              zone->uz_ctor(item, zone->uz_size, udata,
                              flags) != 0) {
                                  zone->uz_fini(item, zone->uz_size);
                                  return (NULL);
                          }
                          return (item);
                  }
                  /* This is unfortunate but should not be fatal. */
          }
  #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();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
  
  zalloc_start:
          bucket = cache->uc_allocbucket;
          if (bucket != NULL && bucket->ub_cnt > 0) {
                  bucket->ub_cnt--;
                  item = bucket->ub_bucket[bucket->ub_cnt];
  #ifdef INVARIANTS
                  bucket->ub_bucket[bucket->ub_cnt] = NULL;
  #endif
                  KASSERT(item != NULL, ("uma_zalloc: Bucket pointer mangled."));
                  cache->uc_allocs++;
                  critical_exit();
                  if (zone->uz_ctor != NULL &&
                      zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
                          atomic_add_long(&zone->uz_fails, 1);
                          zone_free_item(zone, item, udata, SKIP_DTOR);
                          return (NULL);
                  }
  #ifdef INVARIANTS
                  uma_dbg_alloc(zone, NULL, item);
  #endif
                  if (flags & M_ZERO)
                          bzero(item, zone->uz_size);
                  return (item);
          }
  
          /*
           * We have run out of items in our alloc bucket.
           * See if we can switch with our free bucket.
           */
          bucket = cache->uc_freebucket;
          if (bucket != NULL && bucket->ub_cnt > 0) {
  #ifdef UMA_DEBUG_ALLOC
                  printf("uma_zalloc: Swapping empty with alloc.\n");
  #endif
                  cache->uc_freebucket = cache->uc_allocbucket;
                  cache->uc_allocbucket = bucket;
                  goto zalloc_start;
          }
  
          /*
           * Discard any empty allocation bucket while we hold no locks.
           */
          bucket = cache->uc_allocbucket;
          cache->uc_allocbucket = NULL;
          critical_exit();
          if (bucket != NULL)
                  bucket_free(zone, bucket, udata);
  
          /* Short-circuit for zones without buckets and low memory. */
          if (zone->uz_count == 0 || bucketdisable)
                  goto zalloc_item;
  
          /*
           * Attempt to retrieve the item from the per-CPU cache has failed, so
           * we must go back to the zone.  This requires the zone 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.
           */
          lockfail = 0;
          if (ZONE_TRYLOCK(zone) == 0) {
                  /* Record contention to size the buckets. */
                  ZONE_LOCK(zone);
                  lockfail = 1;
          }
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
  
          /*
           * Since we have locked the zone we may as well send back our stats.
           */
          atomic_add_long(&zone->uz_allocs, cache->uc_allocs);
          atomic_add_long(&zone->uz_frees, cache->uc_frees);
          cache->uc_allocs = 0;
          cache->uc_frees = 0;
  
          /* See if we lost the race to fill the cache. */
          if (cache->uc_allocbucket != NULL) {
                  ZONE_UNLOCK(zone);
                  goto zalloc_start;
          }
  
          /*
           * Check the zone's cache of buckets.
           */
          if ((bucket = LIST_FIRST(&zone->uz_buckets)) != NULL) {
                  KASSERT(bucket->ub_cnt != 0,
                      ("uma_zalloc_arg: Returning an empty bucket."));
  
                  LIST_REMOVE(bucket, ub_link);
                  cache->uc_allocbucket = bucket;
                  ZONE_UNLOCK(zone);
                  goto zalloc_start;
          }
          /* We are no longer associated with this CPU. */
          critical_exit();
  
          /*
           * We bump the uz count when the cache size is insufficient to
           * handle the working set.
           */
          if (lockfail && zone->uz_count < BUCKET_MAX)
                  zone->uz_count++;
          ZONE_UNLOCK(zone);
  
          /*
           * Now lets just fill a bucket and put it on the free list.  If that
           * works we'll restart the allocation from the begining and it
           * will use the just filled bucket.
           */
          bucket = zone_alloc_bucket(zone, udata, flags);
          if (bucket != NULL) {
                  ZONE_LOCK(zone);
                  critical_enter();
                  cpu = curcpu;
                  cache = &zone->uz_cpu[cpu];
                  /*
                   * See if we lost the race or were migrated.  Cache the
                   * initialized bucket to make this less likely or claim
                   * the memory directly.
                   */
                  if (cache->uc_allocbucket == NULL)
                          cache->uc_allocbucket = bucket;
                  else
                          LIST_INSERT_HEAD(&zone->uz_buckets, bucket, ub_link);
                  ZONE_UNLOCK(zone);
                  goto zalloc_start;
          }
  
          /*
           * We may not be able to get a bucket so return an actual item.
           */
  #ifdef UMA_DEBUG
          printf("uma_zalloc_arg: Bucketzone returned NULL\n");
  #endif
  
  zalloc_item:
          item = zone_alloc_item(zone, udata, flags);
  
          return (item);
  }
  
  static uma_slab_t
  keg_fetch_slab(uma_keg_t keg, uma_zone_t zone, int flags)
  {
          uma_slab_t slab;
          int reserve;
  
          mtx_assert(&keg->uk_lock, MA_OWNED);
          slab = NULL;
          reserve = 0;
          if ((flags & M_USE_RESERVE) == 0)
                  reserve = keg->uk_reserve;
  
          for (;;) {
                  /*
                   * Find a slab with some space.  Prefer slabs that are partially
                   * used over those that are totally full.  This helps to reduce
                   * fragmentation.
                   */
                  if (keg->uk_free > reserve) {
                          if (!LIST_EMPTY(&keg->uk_part_slab)) {
                                  slab = LIST_FIRST(&keg->uk_part_slab);
                          } else {
                                  slab = LIST_FIRST(&keg->uk_free_slab);
                                  LIST_REMOVE(slab, us_link);
                                  LIST_INSERT_HEAD(&keg->uk_part_slab, slab,
                                      us_link);
                          }
                          MPASS(slab->us_keg == keg);
                          return (slab);
                  }
  
                  /*
                   * M_NOVM means don't ask at all!
                   */
                  if (flags & M_NOVM)
                          break;
  
                  if (keg->uk_maxpages && keg->uk_pages >= keg->uk_maxpages) {
                          keg->uk_flags |= UMA_ZFLAG_FULL;
                          /*
                           * If this is not a multi-zone, set the FULL bit.
                           * Otherwise slab_multi() takes care of it.
                           */
                          if ((zone->uz_flags & UMA_ZFLAG_MULTI) == 0) {
                                  zone->uz_flags |= UMA_ZFLAG_FULL;
                                  zone_log_warning(zone);
                          }
                          if (flags & M_NOWAIT)
                                  break;
                          zone->uz_sleeps++;
                          msleep(keg, &keg->uk_lock, PVM, "keglimit", 0);
                          continue;
                  }
                  slab = keg_alloc_slab(keg, zone, flags);
                  /*
                   * 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.
                   */
                  if (slab) {
                          MPASS(slab->us_keg == keg);
                          LIST_INSERT_HEAD(&keg->uk_part_slab, slab, us_link);
                          return (slab);
                  }
                  /*
                   * We might not have been able to get a slab but another cpu
                   * could have while we were unlocked.  Check again before we
                   * fail.
                   */
                  flags |= M_NOVM;
          }
          return (slab);
  }
  
  static uma_slab_t
  zone_fetch_slab(uma_zone_t zone, uma_keg_t keg, int flags)
  {
          uma_slab_t slab;
  
          if (keg == NULL) {
                  keg = zone_first_keg(zone);
                  KEG_LOCK(keg);
          }
  
          for (;;) {
                  slab = keg_fetch_slab(keg, zone, flags);
                  if (slab)
                          return (slab);
                  if (flags & (M_NOWAIT | M_NOVM))
                          break;
          }
          KEG_UNLOCK(keg);
          return (NULL);
  }
  
  /*
   * uma_zone_fetch_slab_multi:  Fetches a slab from one available keg.  Returns
   * with the keg locked.  On NULL no lock is held.
   *
   * The last pointer is used to seed the search.  It is not required.
   */
  static uma_slab_t
  zone_fetch_slab_multi(uma_zone_t zone, uma_keg_t last, int rflags)
  {
          uma_klink_t klink;
          uma_slab_t slab;
          uma_keg_t keg;
          int flags;
          int empty;
          int full;
  
          /*
           * Don't wait on the first pass.  This will skip limit tests
           * as well.  We don't want to block if we can find a provider
           * without blocking.
           */
          flags = (rflags & ~M_WAITOK) | M_NOWAIT;
          /*
           * Use the last slab allocated as a hint for where to start
           * the search.
           */
          if (last != NULL) {
                  slab = keg_fetch_slab(last, zone, flags);
                  if (slab)
                          return (slab);
                  KEG_UNLOCK(last);
          }
          /*
           * Loop until we have a slab incase of transient failures
           * while M_WAITOK is specified.  I'm not sure this is 100%
           * required but we've done it for so long now.
           */
          for (;;) {
                  empty = 0;
                  full = 0;
                  /*
                   * Search the available kegs for slabs.  Be careful to hold the
                   * correct lock while calling into the keg layer.
                   */
                  LIST_FOREACH(klink, &zone->uz_kegs, kl_link) {
                          keg = klink->kl_keg;
                          KEG_LOCK(keg);
                          if ((keg->uk_flags & UMA_ZFLAG_FULL) == 0) {
                                  slab = keg_fetch_slab(keg, zone, flags);
                                  if (slab)
                                          return (slab);
                          }
                          if (keg->uk_flags & UMA_ZFLAG_FULL)
                                  full++;
                          else
                                  empty++;
                          KEG_UNLOCK(keg);
                  }
                  if (rflags & (M_NOWAIT | M_NOVM))
                          break;
                  flags = rflags;
                  /*
                   * All kegs are full.  XXX We can't atomically check all kegs
                   * and sleep so just sleep for a short period and retry.
                   */
                  if (full && !empty) {
                          ZONE_LOCK(zone);
                          zone->uz_flags |= UMA_ZFLAG_FULL;
                          zone->uz_sleeps++;
                          zone_log_warning(zone);
                          msleep(zone, zone->uz_lockptr, PVM,
                              "zonelimit", hz/100);
                          zone->uz_flags &= ~UMA_ZFLAG_FULL;
                          ZONE_UNLOCK(zone);
                          continue;
                  }
          }
          return (NULL);
  }
  
  static void *
  slab_alloc_item(uma_keg_t keg, uma_slab_t slab)
  {
          void *item;
          uint8_t freei;
  
          MPASS(keg == slab->us_keg);
          mtx_assert(&keg->uk_lock, MA_OWNED);
  
          freei = BIT_FFS(SLAB_SETSIZE, &slab->us_free) - 1;
          BIT_CLR(SLAB_SETSIZE, freei, &slab->us_free);
          item = slab->us_data + (keg->uk_rsize * freei);
          slab->us_freecount--;
          keg->uk_free--;
  
          /* Move this slab to the full list */
          if (slab->us_freecount == 0) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&keg->uk_full_slab, slab, us_link);
          }
  
          return (item);
  }
  
  static int
  zone_import(uma_zone_t zone, void **bucket, int max, int flags)
  {
          uma_slab_t slab;
          uma_keg_t keg;
          int i;
  
          slab = NULL;
          keg = NULL;
          /* Try to keep the buckets totally full */
          for (i = 0; i < max; ) {
                  if ((slab = zone->uz_slab(zone, keg, flags)) == NULL)
                          break;
                  keg = slab->us_keg;
                  while (slab->us_freecount && i < max) { 
                          bucket[i++] = slab_alloc_item(keg, slab);
                          if (keg->uk_free <= keg->uk_reserve)
                                  break;
                  }
                  /* Don't grab more than one slab at a time. */
                  flags &= ~M_WAITOK;
                  flags |= M_NOWAIT;
          }
          if (slab != NULL)
                  KEG_UNLOCK(keg);
  
          return i;
  }
  
  static uma_bucket_t
  zone_alloc_bucket(uma_zone_t zone, void *udata, int flags)
  {
          uma_bucket_t bucket;
          int max;
  
          /* Don't wait for buckets, preserve caller's NOVM setting. */
          bucket = bucket_alloc(zone, udata, M_NOWAIT | (flags & M_NOVM));
          if (bucket == NULL)
                  goto out;
  
          max = MIN(bucket->ub_entries, zone->uz_count);
          bucket->ub_cnt = zone->uz_import(zone->uz_arg, bucket->ub_bucket,
              max, 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;
                  }
          }
  
  out:
          if (bucket == NULL || bucket->ub_cnt == 0) {
                  if (bucket != NULL)
                          bucket_free(zone, bucket, udata);
                  atomic_add_long(&zone->uz_fails, 1);
                  return (NULL);
          }
  
          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.
   *      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 flags)
  {
          void *item;
  
          item = NULL;
  
  #ifdef UMA_DEBUG_ALLOC
          printf("INTERNAL: Allocating one item from %s(%p)\n", zone->uz_name, zone);
  #endif
          if (zone->uz_import(zone->uz_arg, &item, 1, flags) != 1)
                  goto fail;
          atomic_add_long(&zone->uz_allocs, 1);
  
          /*
           * 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);
                          goto fail;
                  }
          }
          if (zone->uz_ctor != NULL) {
                  if (zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
                          zone_free_item(zone, item, udata, SKIP_DTOR);
                          goto fail;
                  }
          }
  #ifdef INVARIANTS
          uma_dbg_alloc(zone, NULL, item);
  #endif
          if (flags & M_ZERO)
                  bzero(item, zone->uz_size);
  
          return (item);
  
  fail:
          atomic_add_long(&zone->uz_fails, 1);
          return (NULL);
  }
  
  /* See uma.h */
  void
  uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
  {
          uma_cache_t cache;
          uma_bucket_t bucket;
          int cpu;
  
  #ifdef UMA_DEBUG_ALLOC_1
          printf("Freeing item %p to %s(%p)\n", item, zone->uz_name, zone);
  #endif
          CTR2(KTR_UMA, "uma_zfree_arg thread %x zone %s", curthread,
              zone->uz_name);
  
          /* uma_zfree(..., NULL) does nothing, to match free(9). */
          if (item == NULL)
                  return;
  #ifdef DEBUG_MEMGUARD
          if (is_memguard_addr(item)) {
                  if (zone->uz_dtor != NULL && zone->uz_dtor != mtrash_dtor)
                          zone->uz_dtor(item, zone->uz_size, udata);
                  if (zone->uz_fini != NULL && zone->uz_fini != mtrash_fini)
                          zone->uz_fini(item, zone->uz_size);
                  memguard_free(item);
                  return;
          }
  #endif
  #ifdef INVARIANTS
          if (zone->uz_flags & UMA_ZONE_MALLOC)
                  uma_dbg_free(zone, udata, item);
          else
                  uma_dbg_free(zone, NULL, item);
  #endif
          if (zone->uz_dtor != NULL)
                  zone->uz_dtor(item, zone->uz_size, udata);
  
          /*
           * 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 (zone->uz_flags & UMA_ZFLAG_FULL)
                  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.
           */
  zfree_restart:
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
  
  zfree_start:
          /*
           * 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;
          if (bucket == NULL || bucket->ub_cnt >= bucket->ub_entries)
                  bucket = cache->uc_freebucket;
          if (bucket != NULL && bucket->ub_cnt < bucket->ub_entries) {
                  KASSERT(bucket->ub_bucket[bucket->ub_cnt] == NULL,
                      ("uma_zfree: Freeing to non free bucket index."));
                  bucket->ub_bucket[bucket->ub_cnt] = item;
                  bucket->ub_cnt++;
                  cache->uc_frees++;
                  critical_exit();
                  return;
          }
  
          /*
           * We must go back the zone, which requires acquiring the zone lock,
           * which in turn means we must release and re-acquire the critical
           * section.  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.
           */
          critical_exit();
          if (zone->uz_count == 0 || bucketdisable)
                  goto zfree_item;
  
          ZONE_LOCK(zone);
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
  
          /*
           * Since we have locked the zone we may as well send back our stats.
           */
          atomic_add_long(&zone->uz_allocs, cache->uc_allocs);
          atomic_add_long(&zone->uz_frees, cache->uc_frees);
          cache->uc_allocs = 0;
          cache->uc_frees = 0;
  
          bucket = cache->uc_freebucket;
          if (bucket != NULL && bucket->ub_cnt < bucket->ub_entries) {
                  ZONE_UNLOCK(zone);
                  goto zfree_start;
          }
          cache->uc_freebucket = NULL;
  
          /* Can we throw this on the zone full list? */
          if (bucket != NULL) {
  #ifdef UMA_DEBUG_ALLOC
                  printf("uma_zfree: Putting old bucket on the free list.\n");
  #endif
                  /* ub_cnt is pointing to the last free item */
                  KASSERT(bucket->ub_cnt != 0,
                      ("uma_zfree: Attempting to insert an empty bucket onto the full list.\n"));
                  LIST_INSERT_HEAD(&zone->uz_buckets, bucket, ub_link);
          }
  
          /* We are no longer associated with this CPU. */
          critical_exit();
  
          /* And the zone.. */
          ZONE_UNLOCK(zone);
  
  #ifdef UMA_DEBUG_ALLOC
          printf("uma_zfree: Allocating new free bucket.\n");
  #endif
          bucket = bucket_alloc(zone, udata, M_NOWAIT);
          if (bucket) {
                  critical_enter();
                  cpu = curcpu;
                  cache = &zone->uz_cpu[cpu];
                  if (cache->uc_freebucket == NULL) {
                          cache->uc_freebucket = bucket;
                          goto zfree_start;
                  }
                  /*
                   * We lost the race, start over.  We have to drop our
                   * critical section to free the bucket.
                   */
                  critical_exit();
                  bucket_free(zone, bucket, udata);
                  goto zfree_restart;
          }
  
          /*
           * If nothing else caught this, we'll just do an internal free.
           */
  zfree_item:
          zone_free_item(zone, item, udata, SKIP_DTOR);
  
          return;
  }
  
  static void
  slab_free_item(uma_keg_t keg, uma_slab_t slab, void *item)
  {
          uint8_t freei;
  
          mtx_assert(&keg->uk_lock, MA_OWNED);
          MPASS(keg == slab->us_keg);
  
          /* Do we need to remove from any lists? */
          if (slab->us_freecount+1 == keg->uk_ipers) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&keg->uk_free_slab, slab, us_link);
          } else if (slab->us_freecount == 0) {
                  LIST_REMOVE(slab, us_link);
                  LIST_INSERT_HEAD(&keg->uk_part_slab, slab, us_link);
          }
  
          /* Slab management. */
          freei = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
          BIT_SET(SLAB_SETSIZE, freei, &slab->us_free);
          slab->us_freecount++;
  
          /* Keg statistics. */
          keg->uk_free++;
  }
  
  static void
  zone_release(uma_zone_t zone, void **bucket, int cnt)
  {
          void *item;
          uma_slab_t slab;
          uma_keg_t keg;
          uint8_t *mem;
          int clearfull;
          int i;
  
          clearfull = 0;
          keg = zone_first_keg(zone);
          KEG_LOCK(keg);
          for (i = 0; i < cnt; i++) {
                  item = bucket[i];
                  if (!(zone->uz_flags & UMA_ZONE_VTOSLAB)) {
                          mem = (uint8_t *)((uintptr_t)item & (~UMA_SLAB_MASK));
                          if (zone->uz_flags & UMA_ZONE_HASH) {
                                  slab = hash_sfind(&keg->uk_hash, mem);
                          } else {
                                  mem += keg->uk_pgoff;
                                  slab = (uma_slab_t)mem;
                          }
                  } else {
                          slab = vtoslab((vm_offset_t)item);
                          if (slab->us_keg != keg) {
                                  KEG_UNLOCK(keg);
                                  keg = slab->us_keg;
                                  KEG_LOCK(keg);
                          }
                  }
                  slab_free_item(keg, slab, item);
                  if (keg->uk_flags & UMA_ZFLAG_FULL) {
                          if (keg->uk_pages < keg->uk_maxpages) {
                                  keg->uk_flags &= ~UMA_ZFLAG_FULL;
                                  clearfull = 1;
                          }
  
                          /* 
                           * We can handle one more allocation. Since we're
                           * clearing ZFLAG_FULL, wake up all procs blocked
                           * on pages. This should be uncommon, so keeping this
                           * simple for now (rather than adding count of blocked 
                           * threads etc).
                           */
                          wakeup(keg);
                  }
          }
          KEG_UNLOCK(keg);
          if (clearfull) {
                  ZONE_LOCK(zone);
                  zone->uz_flags &= ~UMA_ZFLAG_FULL;
                  wakeup(zone);
                  ZONE_UNLOCK(zone);
          }
  
  }
  
  /*
   * 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 void
  zone_free_item(uma_zone_t zone, void *item, void *udata, enum zfreeskip skip)
  {
  
  #ifdef INVARIANTS
          if (skip == SKIP_NONE) {
                  if (zone->uz_flags & UMA_ZONE_MALLOC)
                          uma_dbg_free(zone, udata, item);
                  else
                          uma_dbg_free(zone, NULL, item);
          }
  #endif
          if (skip < SKIP_DTOR && zone->uz_dtor)
                  zone->uz_dtor(item, zone->uz_size, udata);
  
          if (skip < SKIP_FINI && zone->uz_fini)
                  zone->uz_fini(item, zone->uz_size);
  
          atomic_add_long(&zone->uz_frees, 1);
          zone->uz_release(zone->uz_arg, &item, 1);
  }
  
  /* See uma.h */
  int
  uma_zone_set_max(uma_zone_t zone, int nitems)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          if (keg == NULL)
                  return (0);
          KEG_LOCK(keg);
          keg->uk_maxpages = (nitems / keg->uk_ipers) * keg->uk_ppera;
          if (keg->uk_maxpages * keg->uk_ipers < nitems)
                  keg->uk_maxpages += keg->uk_ppera;
          nitems = keg->uk_maxpages * keg->uk_ipers;
          KEG_UNLOCK(keg);
  
          return (nitems);
  }
  
  /* See uma.h */
  int
  uma_zone_get_max(uma_zone_t zone)
  {
          int nitems;
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          if (keg == NULL)
                  return (0);
          KEG_LOCK(keg);
          nitems = keg->uk_maxpages * keg->uk_ipers;
          KEG_UNLOCK(keg);
  
          return (nitems);
  }
  
  /* See uma.h */
  void
  uma_zone_set_warning(uma_zone_t zone, const char *warning)
  {
  
          ZONE_LOCK(zone);
          zone->uz_warning = warning;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  int
  uma_zone_get_cur(uma_zone_t zone)
  {
          int64_t nitems;
          u_int i;
  
          ZONE_LOCK(zone);
          nitems = zone->uz_allocs - zone->uz_frees;
          CPU_FOREACH(i) {
                  /*
                   * See the comment in sysctl_vm_zone_stats() regarding the
                   * safety of accessing the per-cpu caches. With the zone lock
                   * held, it is safe, but can potentially result in stale data.
                   */
                  nitems += zone->uz_cpu[i].uc_allocs -
                      zone->uz_cpu[i].uc_frees;
          }
          ZONE_UNLOCK(zone);
  
          return (nitems < 0 ? 0 : nitems);
  }
  
  /* See uma.h */
  void
  uma_zone_set_init(uma_zone_t zone, uma_init uminit)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
          KEG_LOCK(keg);
          KASSERT(keg->uk_pages == 0,
              ("uma_zone_set_init on non-empty keg"));
          keg->uk_init = uminit;
          KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  void
  uma_zone_set_fini(uma_zone_t zone, uma_fini fini)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
          KEG_LOCK(keg);
          KASSERT(keg->uk_pages == 0,
              ("uma_zone_set_fini on non-empty keg"));
          keg->uk_fini = fini;
          KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  void
  uma_zone_set_zinit(uma_zone_t zone, uma_init zinit)
  {
  
          ZONE_LOCK(zone);
          KASSERT(zone_first_keg(zone)->uk_pages == 0,
              ("uma_zone_set_zinit on non-empty keg"));
          zone->uz_init = zinit;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  void
  uma_zone_set_zfini(uma_zone_t zone, uma_fini zfini)
  {
  
          ZONE_LOCK(zone);
          KASSERT(zone_first_keg(zone)->uk_pages == 0,
              ("uma_zone_set_zfini on non-empty keg"));
          zone->uz_fini = zfini;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  /* XXX uk_freef is not actually used with the zone locked */
  void
  uma_zone_set_freef(uma_zone_t zone, uma_free freef)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
          KEG_LOCK(keg);
          keg->uk_freef = freef;
          KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  /* XXX uk_allocf is not actually used with the zone locked */
  void
  uma_zone_set_allocf(uma_zone_t zone, uma_alloc allocf)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          KEG_LOCK(keg);
          keg->uk_allocf = allocf;
          KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  void
  uma_zone_reserve(uma_zone_t zone, int items)
  {
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          if (keg == NULL)
                  return;
          KEG_LOCK(keg);
          keg->uk_reserve = items;
          KEG_UNLOCK(keg);
  
          return;
  }
  
  /* See uma.h */
  int
  uma_zone_reserve_kva(uma_zone_t zone, int count)
  {
          uma_keg_t keg;
          vm_offset_t kva;
          int pages;
  
          keg = zone_first_keg(zone);
          if (keg == NULL)
                  return (0);
          pages = count / keg->uk_ipers;
  
          if (pages * keg->uk_ipers < count)
                  pages++;
  
  #ifdef UMA_MD_SMALL_ALLOC
          if (keg->uk_ppera > 1) {
  #else
          if (1) {
  #endif
                  kva = kva_alloc(pages * UMA_SLAB_SIZE);
                  if (kva == 0)
                          return (0);
          } else
                  kva = 0;
          KEG_LOCK(keg);
          keg->uk_kva = kva;
          keg->uk_offset = 0;
          keg->uk_maxpages = pages;
  #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_ZONE_NOFREE;
          KEG_UNLOCK(keg);
  
          return (1);
  }
  
  /* See uma.h */
  void
  uma_prealloc(uma_zone_t zone, int items)
  {
          int slabs;
          uma_slab_t slab;
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          if (keg == NULL)
                  return;
          KEG_LOCK(keg);
          slabs = items / keg->uk_ipers;
          if (slabs * keg->uk_ipers < items)
                  slabs++;
          while (slabs > 0) {
                  slab = keg_alloc_slab(keg, zone, M_WAITOK);
                  if (slab == NULL)
                          break;
                  MPASS(slab->us_keg == keg);
                  LIST_INSERT_HEAD(&keg->uk_free_slab, slab, us_link);
                  slabs--;
          }
          KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  uint32_t *
  uma_find_refcnt(uma_zone_t zone, void *item)
  {
          uma_slabrefcnt_t slabref;
          uma_slab_t slab;
          uma_keg_t keg;
          uint32_t *refcnt;
          int idx;
  
          slab = vtoslab((vm_offset_t)item & (~UMA_SLAB_MASK));
          slabref = (uma_slabrefcnt_t)slab;
          keg = slab->us_keg;
          KASSERT(keg->uk_flags & UMA_ZONE_REFCNT,
              ("uma_find_refcnt(): zone possibly not UMA_ZONE_REFCNT"));
          idx = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
          refcnt = &slabref->us_refcnt[idx];
          return refcnt;
  }
  
  /* See uma.h */
  void
  uma_reclaim(void)
  {
  #ifdef UMA_DEBUG
          printf("UMA: vm asked us to release pages!\n");
  #endif
          bucket_enable();
          zone_foreach(zone_drain);
          /*
           * 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(slabzone);
          zone_drain(slabrefzone);
          bucket_zone_drain();
  }
  
  /* See uma.h */
  int
  uma_zone_exhausted(uma_zone_t zone)
  {
          int full;
  
          ZONE_LOCK(zone);
          full = (zone->uz_flags & UMA_ZFLAG_FULL);
          ZONE_UNLOCK(zone);
          return (full);  
  }
  
  int
  uma_zone_exhausted_nolock(uma_zone_t zone)
  {
          return (zone->uz_flags & UMA_ZFLAG_FULL);
  }
  
  void *
  uma_large_malloc(int size, int wait)
  {
          void *mem;
          uma_slab_t slab;
          uint8_t flags;
  
          slab = zone_alloc_item(slabzone, NULL, wait);
          if (slab == NULL)
                  return (NULL);
          mem = page_alloc(NULL, size, &flags, wait);
          if (mem) {
                  vsetslab((vm_offset_t)mem, slab);
                  slab->us_data = mem;
                  slab->us_flags = flags | UMA_SLAB_MALLOC;
                  slab->us_size = size;
          } else {
                  zone_free_item(slabzone, slab, NULL, SKIP_NONE);
          }
  
          return (mem);
  }
  
  void
  uma_large_free(uma_slab_t slab)
  {
  
          page_free(slab->us_data, slab->us_size, slab->us_flags);
          zone_free_item(slabzone, slab, NULL, SKIP_NONE);
  }
  
  void
  uma_print_stats(void)
  {
          zone_foreach(uma_print_zone);
  }
  
  static void
  slab_print(uma_slab_t slab)
  {
          printf("slab: keg %p, data %p, freecount %d\n",
                  slab->us_keg, slab->us_data, slab->us_freecount);
  }
  
  static void
  cache_print(uma_cache_t cache)
  {
          printf("alloc: %p(%d), free: %p(%d)\n",
                  cache->uc_allocbucket,
                  cache->uc_allocbucket?cache->uc_allocbucket->ub_cnt:0,
                  cache->uc_freebucket,
                  cache->uc_freebucket?cache->uc_freebucket->ub_cnt:0);
  }
  
  static void
  uma_print_keg(uma_keg_t keg)
  {
          uma_slab_t slab;
  
          printf("keg: %s(%p) size %d(%d) flags %#x ipers %d ppera %d "
              "out %d free %d limit %d\n",
              keg->uk_name, keg, keg->uk_size, keg->uk_rsize, keg->uk_flags,
              keg->uk_ipers, keg->uk_ppera,
              (keg->uk_ipers * keg->uk_pages) - keg->uk_free, keg->uk_free,
              (keg->uk_maxpages / keg->uk_ppera) * keg->uk_ipers);
          printf("Part slabs:\n");
          LIST_FOREACH(slab, &keg->uk_part_slab, us_link)
                  slab_print(slab);
          printf("Free slabs:\n");
          LIST_FOREACH(slab, &keg->uk_free_slab, us_link)
                  slab_print(slab);
          printf("Full slabs:\n");
          LIST_FOREACH(slab, &keg->uk_full_slab, us_link)
                  slab_print(slab);
  }
  
  void
  uma_print_zone(uma_zone_t zone)
  {
          uma_cache_t cache;
          uma_klink_t kl;
          int i;
  
          printf("zone: %s(%p) size %d flags %#x\n",
              zone->uz_name, zone, zone->uz_size, zone->uz_flags);
          LIST_FOREACH(kl, &zone->uz_kegs, kl_link)
                  uma_print_keg(kl->kl_keg);
          CPU_FOREACH(i) {
                  cache = &zone->uz_cpu[i];
                  printf("CPU %d Cache:\n", i);
                  cache_print(cache);
          }
  }
  
  #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.
   *
   * XXXRW: Following the uc_allocbucket and uc_freebucket pointers here isn't
   * safe from off-CPU; we should modify the caches to track this information
   * directly so that we don't have to.
   */
  static void
  uma_zone_sumstat(uma_zone_t z, int *cachefreep, uint64_t *allocsp,
      uint64_t *freesp, uint64_t *sleepsp)
  {
          uma_cache_t cache;
          uint64_t allocs, frees, sleeps;
          int cachefree, cpu;
  
          allocs = frees = sleeps = 0;
          cachefree = 0;
          CPU_FOREACH(cpu) {
                  cache = &z->uz_cpu[cpu];
                  if (cache->uc_allocbucket != NULL)
                          cachefree += cache->uc_allocbucket->ub_cnt;
                  if (cache->uc_freebucket != NULL)
                          cachefree += cache->uc_freebucket->ub_cnt;
                  allocs += cache->uc_allocs;
                  frees += cache->uc_frees;
          }
          allocs += z->uz_allocs;
          frees += z->uz_frees;
          sleeps += z->uz_sleeps;
          if (cachefreep != NULL)
                  *cachefreep = cachefree;
          if (allocsp != NULL)
                  *allocsp = allocs;
          if (freesp != NULL)
                  *freesp = frees;
          if (sleepsp != NULL)
                  *sleepsp = sleeps;
  }
  #endif /* DDB */
  
  static int
  sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS)
  {
          uma_keg_t kz;
          uma_zone_t z;
          int count;
  
          count = 0;
          mtx_lock(&uma_mtx);
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link)
                          count++;
          }
          mtx_unlock(&uma_mtx);
          return (sysctl_handle_int(oidp, &count, 0, req));
  }
  
  static int
  sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS)
  {
          struct uma_stream_header ush;
          struct uma_type_header uth;
          struct uma_percpu_stat ups;
          uma_bucket_t bucket;
          struct sbuf sbuf;
          uma_cache_t cache;
          uma_klink_t kl;
          uma_keg_t kz;
          uma_zone_t z;
          uma_keg_t k;
          int count, error, i;
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error != 0)
                  return (error);
          sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
  
          count = 0;
          mtx_lock(&uma_mtx);
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, 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) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                          bzero(&uth, sizeof(uth));
                          ZONE_LOCK(z);
                          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;
                          LIST_FOREACH(kl, &z->uz_kegs, kl_link) {
                                  k = kl->kl_keg;
                                  uth.uth_maxpages += k->uk_maxpages;
                                  uth.uth_pages += k->uk_pages;
                                  uth.uth_keg_free += k->uk_free;
                                  uth.uth_limit = (k->uk_maxpages / k->uk_ppera)
                                      * k->uk_ipers;
                          }
  
                          /*
                           * 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;
  
                          LIST_FOREACH(bucket, &z->uz_buckets, ub_link)
                                  uth.uth_zone_free += bucket->ub_cnt;
                          uth.uth_allocs = z->uz_allocs;
                          uth.uth_frees = z->uz_frees;
                          uth.uth_fails = z->uz_fails;
                          uth.uth_sleeps = z->uz_sleeps;
                          (void)sbuf_bcat(&sbuf, &uth, sizeof(uth));
                          /*
                           * While it is not normally safe to access the cache
                           * bucket pointers while not on the CPU that owns the
                           * cache, we only allow the pointers to be exchanged
                           * without the zone lock held, not invalidated, so
                           * accept the possible race associated with bucket
                           * exchange during monitoring.
                           */
                          for (i = 0; i < (mp_maxid + 1); i++) {
                                  bzero(&ups, sizeof(ups));
                                  if (kz->uk_flags & UMA_ZFLAG_INTERNAL)
                                          goto skip;
                                  if (CPU_ABSENT(i))
                                          goto skip;
                                  cache = &z->uz_cpu[i];
                                  if (cache->uc_allocbucket != NULL)
                                          ups.ups_cache_free +=
                                              cache->uc_allocbucket->ub_cnt;
                                  if (cache->uc_freebucket != NULL)
                                          ups.ups_cache_free +=
                                              cache->uc_freebucket->ub_cnt;
                                  ups.ups_allocs = cache->uc_allocs;
                                  ups.ups_frees = cache->uc_frees;
  skip:
                                  (void)sbuf_bcat(&sbuf, &ups, sizeof(ups));
                          }
                          ZONE_UNLOCK(z);
                  }
          }
          mtx_unlock(&uma_mtx);
          error = sbuf_finish(&sbuf);
          sbuf_delete(&sbuf);
          return (error);
  }
  
  #ifdef DDB
  DB_SHOW_COMMAND(uma, db_show_uma)
  {
          uint64_t allocs, frees, sleeps;
          uma_bucket_t bucket;
          uma_keg_t kz;
          uma_zone_t z;
          int cachefree;
  
          db_printf("%18s %8s %8s %8s %12s %8s\n", "Zone", "Size", "Used", "Free",
              "Requests", "Sleeps");
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                          if (kz->uk_flags & UMA_ZFLAG_INTERNAL) {
                                  allocs = z->uz_allocs;
                                  frees = z->uz_frees;
                                  sleeps = z->uz_sleeps;
                                  cachefree = 0;
                          } else
                                  uma_zone_sumstat(z, &cachefree, &allocs,
                                      &frees, &sleeps);
                          if (!((z->uz_flags & UMA_ZONE_SECONDARY) &&
                              (LIST_FIRST(&kz->uk_zones) != z)))
                                  cachefree += kz->uk_free;
                          LIST_FOREACH(bucket, &z->uz_buckets, ub_link)
                                  cachefree += bucket->ub_cnt;
                          db_printf("%18s %8ju %8jd %8d %12ju %8ju\n", z->uz_name,
                              (uintmax_t)kz->uk_size,
                              (intmax_t)(allocs - frees), cachefree,
                              (uintmax_t)allocs, sleeps);
                          if (db_pager_quit)
                                  return;
                  }
          }
  }
  #endif

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