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

     /*-
      * Copyright (c) 2002-2005, 2009 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/8.0/sys/vm/uma_core.c 194429 2009-06-18 07:27:11Z alc $");
    
    /* 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 <sys/param.h>
    #include <sys/systm.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/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_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 <machine/vmparam.h>
    
    #include <ddb/ddb.h>
    
    /*
     * 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. */
   static 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 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 uma_boot_pages_mtx;
   
   /* Is the VM done starting up? */
   static int booted = 0;
   
   /* Maximum number of allowed items-per-slab if the slab header is OFFPAGE */
   static u_int uma_max_ipers;
   static u_int uma_max_ipers_ref;
   
   /*
    * 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 {
           char *name;
           size_t size;
           uma_ctor ctor;
           uma_dtor dtor;
           uma_init uminit;
           uma_fini fini;
           uma_keg_t keg;
           int align;
           u_int32_t flags;
   };
   
   struct uma_kctor_args {
           uma_zone_t zone;
           size_t size;
           uma_init uminit;
           uma_fini fini;
           int align;
           u_int32_t flags;
   };
   
   struct uma_bucket_zone {
           uma_zone_t      ubz_zone;
           char            *ubz_name;
           int             ubz_entries;
   };
   
   #define BUCKET_MAX      128
   
   struct uma_bucket_zone bucket_zones[] = {
           { NULL, "16 Bucket", 16 },
           { NULL, "32 Bucket", 32 },
           { NULL, "64 Bucket", 64 },
           { NULL, "128 Bucket", 128 },
           { NULL, NULL, 0}
   };
   
   #define BUCKET_SHIFT    4
   #define BUCKET_ZONES    ((BUCKET_MAX >> BUCKET_SHIFT) + 1)
   
   /*
    * bucket_size[] maps requested bucket sizes to zones that allocate a bucket
    * of approximately the right size.
    */
   static uint8_t bucket_size[BUCKET_ZONES];
   
   /*
    * Flags and enumerations to be passed to internal functions.
    */
   enum zfreeskip { SKIP_NONE, SKIP_DTOR, SKIP_FINI };
   
   #define ZFREE_STATFAIL  0x00000001      /* Update zone failure statistic. */
   #define ZFREE_STATFREE  0x00000002      /* Update zone free statistic. */
   
   /* Prototypes.. */
   
   static void *obj_alloc(uma_zone_t, int, u_int8_t *, int);
   static void *page_alloc(uma_zone_t, int, u_int8_t *, int);
   static void *startup_alloc(uma_zone_t, int, u_int8_t *, int);
   static void page_free(void *, int, u_int8_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,
       int);
   static void bucket_enable(void);
   static void bucket_init(void);
   static uma_bucket_t bucket_alloc(int, int);
   static void bucket_free(uma_bucket_t);
   static void bucket_zone_drain(void);
   static int zone_alloc_bucket(uma_zone_t zone, 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_zone_t zone, uma_slab_t slab);
   static uma_keg_t uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit,
       uma_fini fini, int align, u_int32_t flags);
   static inline void zone_relock(uma_zone_t zone, uma_keg_t keg);
   static inline void keg_relock(uma_keg_t keg, uma_zone_t zone);
   
   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");
   
   /*
    * This routine checks to see whether or not it's safe to enable buckets.
    */
   
   static void
   bucket_enable(void)
   {
           if (cnt.v_free_count < cnt.v_free_min)
                   bucketdisable = 1;
           else
                   bucketdisable = 0;
   }
   
   /*
    * 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.  Initialize bucket_size[] to point
    * the range of appropriate bucket sizes at the zone.
    */
   static void
   bucket_init(void)
   {
           struct uma_bucket_zone *ubz;
           int i;
           int j;
   
           for (i = 0, j = 0; bucket_zones[j].ubz_entries != 0; j++) {
                   int size;
   
                   ubz = &bucket_zones[j];
                   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_ZFLAG_INTERNAL | UMA_ZFLAG_BUCKET);
                   for (; i <= ubz->ubz_entries; i += (1 << BUCKET_SHIFT))
                           bucket_size[i >> BUCKET_SHIFT] = j;
           }
   }
   
   /*
    * 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)
   {
           int idx;
   
           idx = howmany(entries, 1 << BUCKET_SHIFT);
           return (&bucket_zones[bucket_size[idx]]);
   }
   
   static uma_bucket_t
   bucket_alloc(int entries, int bflags)
   {
           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);
   
           ubz = bucket_zone_lookup(entries);
           bucket = zone_alloc_item(ubz->ubz_zone, NULL, bflags);
           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_bucket_t bucket)
   {
           struct uma_bucket_zone *ubz;
   
           ubz = bucket_zone_lookup(bucket->ub_entries);
           zone_free_item(ubz->ubz_zone, bucket, NULL, SKIP_NONE,
               ZFREE_STATFREE);
   }
   
   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 inline uma_keg_t
   zone_first_keg(uma_zone_t zone)
   {
   
           return (LIST_FIRST(&zone->uz_kegs)->kl_keg);
   }
   
   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);
                           KEG_LOCK(keg);
                   }
           }
           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, ZFREE_STATFREE);
           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)
   {
           void *item;
   
           if (bucket == NULL)
                   return;
   
           while (bucket->ub_cnt > 0)  {
                   bucket->ub_cnt--;
                   item = bucket->ub_bucket[bucket->ub_cnt];
   #ifdef INVARIANTS
                   bucket->ub_bucket[bucket->ub_cnt] = NULL;
                   KASSERT(item != NULL,
                       ("bucket_drain: botched ptr, item is NULL"));
   #endif
                   zone_free_item(zone, item, NULL, SKIP_DTOR, 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?
            */
           for (cpu = 0; cpu <= mp_maxid; cpu++) {
                   if (CPU_ABSENT(cpu))
                           continue;
                   cache = &zone->uz_cpu[cpu];
                   bucket_drain(zone, cache->uc_allocbucket);
                   bucket_drain(zone, cache->uc_freebucket);
                   if (cache->uc_allocbucket != NULL)
                           bucket_free(cache->uc_allocbucket);
                   if (cache->uc_freebucket != NULL)
                           bucket_free(cache->uc_freebucket);
                   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_full_bucket)) != NULL) {
                   LIST_REMOVE(bucket, ub_link);
                   ZONE_UNLOCK(zone);
                   bucket_drain(zone, bucket);
                   bucket_free(bucket);
                   ZONE_LOCK(zone);
           }
   
           /* Now we do the free queue.. */
           while ((bucket = LIST_FIRST(&zone->uz_free_bucket)) != NULL) {
                   LIST_REMOVE(bucket, ub_link);
                   bucket_free(bucket);
           }
   }
   
   /*
    * 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;
           u_int8_t flags;
           u_int8_t *mem;
           int i;
   
           /*
            * 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);
                   if (keg->uk_fini)
                           for (i = 0; i < keg->uk_ipers; i++)
                                   keg->uk_fini(
                                       slab->us_data + (keg->uk_rsize * i),
                                       keg->uk_size);
                   flags = slab->us_flags;
                   mem = slab->us_data;
   
                   if (keg->uk_flags & UMA_ZONE_VTOSLAB) {
                           vm_object_t obj;
   
                           if (flags & UMA_SLAB_KMEM)
                                   obj = kmem_object;
                           else if (flags & UMA_SLAB_KERNEL)
                                   obj = kernel_object;
                           else
                                   obj = NULL;
                           for (i = 0; i < keg->uk_ppera; i++)
                                   vsetobj((vm_offset_t)mem + (i * PAGE_SIZE),
                                       obj);
                   }
                   if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                           zone_free_item(keg->uk_slabzone, slab, NULL,
                               SKIP_NONE, ZFREE_STATFREE);
   #ifdef UMA_DEBUG
                   printf("%s: Returning %d bytes.\n",
                       keg->uk_name, UMA_SLAB_SIZE * keg->uk_ppera);
   #endif
                   keg->uk_freef(mem, UMA_SLAB_SIZE * keg->uk_ppera, flags);
           }
   }
   
   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_lock, 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;
           u_int8_t *mem;
           u_int8_t flags;
           int i;
   
           mtx_assert(&keg->uk_lock, MA_OWNED);
           slab = NULL;
   
   #ifdef UMA_DEBUG
           printf("slab_zalloc:  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) {
                           KEG_LOCK(keg);
                           return NULL;
                   }
           }
   
           /*
            * 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;
   
           /* zone is passed for legacy reasons. */
           mem = allocf(zone, keg->uk_ppera * UMA_SLAB_SIZE, &flags, wait);
           if (mem == NULL) {
                   if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                           zone_free_item(keg->uk_slabzone, slab, NULL,
                               SKIP_NONE, ZFREE_STATFREE);
                   KEG_LOCK(keg);
                   return (NULL);
           }
   
           /* 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_firstfree = 0;
           slab->us_flags = flags;
   
           if (keg->uk_flags & UMA_ZONE_REFCNT) {
                   slabref = (uma_slabrefcnt_t)slab;
                   for (i = 0; i < keg->uk_ipers; i++) {
                           slabref->us_freelist[i].us_refcnt = 0;
                           slabref->us_freelist[i].us_item = i+1;
                   }
           } else {
                   for (i = 0; i < keg->uk_ipers; i++)
                           slab->us_freelist[i].us_item = i+1;
           }
   
           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) {
                           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_VTOSLAB) {
                                   vm_object_t obj;
   
                                   if (flags & UMA_SLAB_KMEM)
                                           obj = kmem_object;
                                   else if (flags & UMA_SLAB_KERNEL)
                                           obj = kernel_object;
                                   else
                                           obj = NULL;
                                   for (i = 0; i < keg->uk_ppera; i++)
                                           vsetobj((vm_offset_t)mem +
                                               (i * PAGE_SIZE), obj);
                           }
                           if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                                   zone_free_item(keg->uk_slabzone, slab,
                                       NULL, SKIP_NONE, ZFREE_STATFREE);
                           keg->uk_freef(mem, UMA_SLAB_SIZE * keg->uk_ppera,
                               flags);
                           KEG_LOCK(keg);
                           return (NULL);
                   }
           }
           KEG_LOCK(keg);
   
           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, u_int8_t *pflag, int wait)
   {
           uma_keg_t keg;
           uma_slab_t tmps;
   
           keg = zone_first_keg(zone);
   
           /*
            * Check our small startup cache to see if it has pages remaining.
            */
           mtx_lock(&uma_boot_pages_mtx);
           if ((tmps = LIST_FIRST(&uma_boot_pages)) != NULL) {
                   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 == 0)
                   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 = 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, u_int8_t *pflag, int wait)
   {
           void *p;        /* Returned page */
   
           *pflag = UMA_SLAB_KMEM;
           p = (void *) kmem_malloc(kmem_map, 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 *
   obj_alloc(uma_zone_t zone, int bytes, u_int8_t *flags, int wait)
   {
           vm_object_t object;
           vm_offset_t retkva, zkva;
          vm_page_t p;
          int pages, startpages;
          uma_keg_t keg;
  
          keg = zone_first_keg(zone);
          object = keg->uk_obj;
          retkva = 0;
  
          /*
           * This looks a little weird since we're getting one page at a time.
           */
          VM_OBJECT_LOCK(object);
          p = TAILQ_LAST(&object->memq, pglist);
          pages = p != NULL ? p->pindex + 1 : 0;
          startpages = pages;
          zkva = keg->uk_kva + pages * PAGE_SIZE;
          for (; bytes > 0; bytes -= PAGE_SIZE) {
                  p = vm_page_alloc(object, pages,
                      VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED);
                  if (p == NULL) {
                          if (pages != startpages)
                                  pmap_qremove(retkva, pages - startpages);
                          while (pages != startpages) {
                                  pages--;
                                  p = TAILQ_LAST(&object->memq, pglist);
                                  vm_page_lock_queues();
                                  vm_page_unwire(p, 0);
                                  vm_page_free(p);
                                  vm_page_unlock_queues();
                          }
                          retkva = 0;
                          goto done;
                  }
                  pmap_qenter(zkva, &p, 1);
                  if (retkva == 0)
                          retkva = zkva;
                  zkva += PAGE_SIZE;
                  pages += 1;
          }
  done:
          VM_OBJECT_UNLOCK(object);
          *flags = UMA_SLAB_PRIV;
  
          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, u_int8_t flags)
  {
          vm_map_t map;
  
          if (flags & UMA_SLAB_KMEM)
                  map = kmem_map;
          else if (flags & UMA_SLAB_KERNEL)
                  map = kernel_map;
          else
                  panic("UMA: page_free used with invalid flags %d", flags);
  
          kmem_free(map, (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;
  
          KASSERT(keg != NULL, ("Keg is null in keg_small_init"));
          rsize = keg->uk_size;
  
          if (rsize < UMA_SMALLEST_UNIT)
                  rsize = UMA_SMALLEST_UNIT;
          if (rsize & keg->uk_align)
                  rsize = (rsize & ~keg->uk_align) + (keg->uk_align + 1);
  
          keg->uk_rsize = rsize;
          keg->uk_ppera = 1;
  
          if (keg->uk_flags & UMA_ZONE_REFCNT) {
                  rsize += UMA_FRITMREF_SZ;       /* linkage & refcnt */
                  shsize = sizeof(struct uma_slab_refcnt);
          } else {
                  rsize += UMA_FRITM_SZ;  /* Account for linkage */
                  shsize = sizeof(struct uma_slab);
          }
  
          keg->uk_ipers = (UMA_SLAB_SIZE - shsize) / rsize;
          KASSERT(keg->uk_ipers != 0, ("keg_small_init: ipers is 0"));
          memused = keg->uk_ipers * rsize + shsize;
          wastedspace = UMA_SLAB_SIZE - 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 (kmem_map) 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;
  
          if ((wastedspace >= UMA_MAX_WASTE) &&
              (keg->uk_ipers < (UMA_SLAB_SIZE / keg->uk_rsize))) {
                  keg->uk_ipers = UMA_SLAB_SIZE / keg->uk_rsize;
                  KASSERT(keg->uk_ipers <= 255,
                      ("keg_small_init: keg->uk_ipers too high!"));
  #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,
                      UMA_MAX_WASTE, keg->uk_ipers,
                      UMA_SLAB_SIZE - keg->uk_ipers * keg->uk_rsize);
  #endif
                  keg->uk_flags |= UMA_ZONE_OFFPAGE;
                  if ((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)
  {
          int pages;
  
          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"));
  
          pages = keg->uk_size / UMA_SLAB_SIZE;
  
          /* Account for remainder */
          if ((pages * UMA_SLAB_SIZE) < keg->uk_size)
                  pages++;
  
          keg->uk_ppera = pages;
          keg->uk_ipers = 1;
  
          keg->uk_flags |= UMA_ZONE_OFFPAGE;
          if ((keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
                  keg->uk_flags |= UMA_ZONE_HASH;
  
          keg->uk_rsize = keg->uk_size;
  }
  
  static void
  keg_cachespread_init(uma_keg_t keg)
  {
          int alignsize;
          int trailer;
          int pages;
          int rsize;
  
          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_ipers = ((pages * PAGE_SIZE) + trailer) / rsize;
          keg->uk_flags |= UMA_ZONE_OFFPAGE | UMA_ZONE_VTOSLAB;
          KASSERT(keg->uk_ipers <= uma_max_ipers,
              ("keg_small_init: keg->uk_ipers too high(%d) increase max_ipers",
              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_pages = 0;
          keg->uk_flags = arg->flags;
          keg->uk_allocf = page_alloc;
          keg->uk_freef = page_free;
          keg->uk_recurse = 0;
          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;
  
          /*
           * The +UMA_FRITM_SZ added to uk_size is to account for the
           * linkage that is added to the size in keg_small_init().  If
           * we don't account for this here then we may end up in
           * keg_small_init() with a calculated 'ipers' of 0.
           */
          if (keg->uk_flags & UMA_ZONE_REFCNT) {
                  if (keg->uk_flags & UMA_ZONE_CACHESPREAD)
                          keg_cachespread_init(keg);
                  else if ((keg->uk_size+UMA_FRITMREF_SZ) >
                      (UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt)))
                          keg_large_init(keg);
                  else
                          keg_small_init(keg);
          } else {
                  if (keg->uk_flags & UMA_ZONE_CACHESPREAD)
                          keg_cachespread_init(keg);
                  else if ((keg->uk_size+UMA_FRITM_SZ) >
                      (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)
                          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;
  #endif
                  if (booted == 0)
                          keg->uk_allocf = startup_alloc;
          }
  
          /*
           * Initialize keg's lock (shared among zones).
           */
          if (arg->flags & UMA_ZONE_MTXCLASS)
                  KEG_LOCK_INIT(keg, 1);
          else
                  KEG_LOCK_INIT(keg, 0);
  
          /*
           * 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 */
                  if (keg->uk_flags & UMA_ZONE_REFCNT)
                          totsize = sizeof(struct uma_slab_refcnt) +
                              keg->uk_ipers * UMA_FRITMREF_SZ;
                  else
                          totsize = sizeof(struct uma_slab) +
                              keg->uk_ipers * UMA_FRITM_SZ;
  
                  if (totsize & UMA_ALIGN_PTR)
                          totsize = (totsize & ~UMA_ALIGN_PTR) +
                              (UMA_ALIGN_PTR + 1);
                  keg->uk_pgoff = UMA_SLAB_SIZE - totsize;
  
                  if (keg->uk_flags & UMA_ZONE_REFCNT)
                          totsize = keg->uk_pgoff + sizeof(struct uma_slab_refcnt)
                              + keg->uk_ipers * UMA_FRITMREF_SZ;
                  else
                          totsize = keg->uk_pgoff + sizeof(struct uma_slab)
                              + keg->uk_ipers * UMA_FRITM_SZ;
  
                  /*
                   * 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.
                   */
                  if (totsize > UMA_SLAB_SIZE) {
                          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 %d 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_fills = zone->uz_count = 0;
          zone->uz_flags = 0;
          keg = arg->keg;
  
          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_lock = &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_lock = &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);
          }
  
          if (keg->uk_flags & UMA_ZONE_MAXBUCKET)
                  zone->uz_count = BUCKET_MAX;
          else if (keg->uk_ipers <= BUCKET_MAX)
                  zone->uz_count = keg->uk_ipers;
          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 was not empty (%d items). "
                      " Lost %d pages of memory.\n",
                      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 ((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,
                      ZFREE_STATFREE);
          }
  }
  
  /*
   * 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;
          u_int objsize, totsize, wsize;
          int i;
  
  #ifdef UMA_DEBUG
          printf("Creating uma keg headers zone and keg.\n");
  #endif
          mtx_init(&uma_mtx, "UMA lock", NULL, MTX_DEF);
  
          /*
           * Figure out the maximum number of items-per-slab we'll have if
           * we're using the OFFPAGE slab header to track free items, given
           * all possible object sizes and the maximum desired wastage
           * (UMA_MAX_WASTE).
           *
           * We iterate until we find an object size for
           * which the calculated wastage in keg_small_init() will be
           * enough to warrant OFFPAGE.  Since wastedspace versus objsize
           * is an overall increasing see-saw function, we find the smallest
           * objsize such that the wastage is always acceptable for objects
           * with that objsize or smaller.  Since a smaller objsize always
           * generates a larger possible uma_max_ipers, we use this computed
           * objsize to calculate the largest ipers possible.  Since the
           * ipers calculated for OFFPAGE slab headers is always larger than
           * the ipers initially calculated in keg_small_init(), we use
           * the former's equation (UMA_SLAB_SIZE / keg->uk_rsize) to
           * obtain the maximum ipers possible for offpage slab headers.
           *
           * It should be noted that ipers versus objsize is an inversly
           * proportional function which drops off rather quickly so as
           * long as our UMA_MAX_WASTE is such that the objsize we calculate
           * falls into the portion of the inverse relation AFTER the steep
           * falloff, then uma_max_ipers shouldn't be too high (~10 on i386).
           *
           * Note that we have 8-bits (1 byte) to use as a freelist index
           * inside the actual slab header itself and this is enough to
           * accomodate us.  In the worst case, a UMA_SMALLEST_UNIT sized
           * object with offpage slab header would have ipers =
           * UMA_SLAB_SIZE / UMA_SMALLEST_UNIT (currently = 256), which is
           * 1 greater than what our byte-integer freelist index can
           * accomodate, but we know that this situation never occurs as
           * for UMA_SMALLEST_UNIT-sized objects, we will never calculate
           * that we need to go to offpage slab headers.  Or, if we do,
           * then we trap that condition below and panic in the INVARIANTS case.
           */
          wsize = UMA_SLAB_SIZE - sizeof(struct uma_slab) - UMA_MAX_WASTE;
          totsize = wsize;
          objsize = UMA_SMALLEST_UNIT;
          while (totsize >= wsize) {
                  totsize = (UMA_SLAB_SIZE - sizeof(struct uma_slab)) /
                      (objsize + UMA_FRITM_SZ);
                  totsize *= (UMA_FRITM_SZ + objsize);
                  objsize++;
          }
          if (objsize > UMA_SMALLEST_UNIT)
                  objsize--;
          uma_max_ipers = MAX(UMA_SLAB_SIZE / objsize, 64);
  
          wsize = UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt) - UMA_MAX_WASTE;
          totsize = wsize;
          objsize = UMA_SMALLEST_UNIT;
          while (totsize >= wsize) {
                  totsize = (UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt)) /
                      (objsize + UMA_FRITMREF_SZ);
                  totsize *= (UMA_FRITMREF_SZ + objsize);
                  objsize++;
          }
          if (objsize > UMA_SMALLEST_UNIT)
                  objsize--;
          uma_max_ipers_ref = MAX(UMA_SLAB_SIZE / objsize, 64);
  
          KASSERT((uma_max_ipers_ref <= 255) && (uma_max_ipers <= 255),
              ("uma_startup: calculated uma_max_ipers values too large!"));
  
  #ifdef UMA_DEBUG
          printf("Calculated uma_max_ipers (for OFFPAGE) is %d\n", uma_max_ipers);
          printf("Calculated uma_max_ipers_slab (for OFFPAGE) is %d\n",
              uma_max_ipers_ref);
  #endif
  
          /* "manually" create the initial zone */
          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)((u_int8_t *)bootmem + (i * UMA_SLAB_SIZE));
                  slab->us_data = (u_int8_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
  
          /*
           * This is the max number of free list items we'll have with
           * offpage slabs.
           */
          slabsize = uma_max_ipers * UMA_FRITM_SZ;
          slabsize += sizeof(struct uma_slab);
  
          /* Now make a zone for slab headers */
          slabzone = uma_zcreate("UMA Slabs",
                                  slabsize,
                                  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 = uma_max_ipers_ref * UMA_FRITMREF_SZ;
          slabsize += sizeof(struct uma_slab_refcnt);
          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();
  
  #if defined(UMA_MD_SMALL_ALLOC) && !defined(UMA_MD_SMALL_ALLOC_NEEDS_VM)
          booted = 1;
  #endif
  
  #ifdef UMA_DEBUG
          printf("UMA startup complete.\n");
  #endif
  }
  
  /* see uma.h */
  void
  uma_startup2(void)
  {
          booted = 1;
          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, u_int32_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(char *name, size_t size, uma_ctor ctor, uma_dtor dtor,
                  uma_init uminit, uma_fini fini, int align, u_int32_t flags)
  
  {
          struct uma_zctor_args args;
  
          /* This stuff is essential for the zone ctor */
          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);
          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));
  }
  
  static void
  zone_lock_pair(uma_zone_t a, uma_zone_t b)
  {
          if (a < b) {
                  ZONE_LOCK(a);
                  mtx_lock_flags(b->uz_lock, MTX_DUPOK);
          } else {
                  ZONE_LOCK(b);
                  mtx_lock_flags(a->uz_lock, 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, ZFREE_STATFREE);
  }
  
  /* 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 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);
          }
  
          /*
           * 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.
           */
  zalloc_restart:
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
  
  zalloc_start:
          bucket = cache->uc_allocbucket;
  
          if (bucket) {
                  if (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();
  #ifdef INVARIANTS
                          ZONE_LOCK(zone);
                          uma_dbg_alloc(zone, NULL, item);
                          ZONE_UNLOCK(zone);
  #endif
                          if (zone->uz_ctor != NULL) {
                                  if (zone->uz_ctor(item, zone->uz_size,
                                      udata, flags) != 0) {
                                          zone_free_item(zone, item, udata,
                                              SKIP_DTOR, ZFREE_STATFAIL |
                                              ZFREE_STATFREE);
                                          return (NULL);
                                  }
                          }
                          if (flags & M_ZERO)
                                  bzero(item, zone->uz_size);
                          return (item);
                  } else if (cache->uc_freebucket) {
                          /*
                           * We have run out of items in our allocbucket.
                           * See if we can switch with our free bucket.
                           */
                          if (cache->uc_freebucket->ub_cnt > 0) {
  #ifdef UMA_DEBUG_ALLOC
                                  printf("uma_zalloc: Swapping empty with"
                                      " alloc.\n");
  #endif
                                  bucket = cache->uc_freebucket;
                                  cache->uc_freebucket = cache->uc_allocbucket;
                                  cache->uc_allocbucket = bucket;
  
                                  goto zalloc_start;
                          }
                  }
          }
          /*
           * 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.
           */
          critical_exit();
          ZONE_LOCK(zone);
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
          bucket = cache->uc_allocbucket;
          if (bucket != NULL) {
                  if (bucket->ub_cnt > 0) {
                          ZONE_UNLOCK(zone);
                          goto zalloc_start;
                  }
                  bucket = cache->uc_freebucket;
                  if (bucket != NULL && bucket->ub_cnt > 0) {
                          ZONE_UNLOCK(zone);
                          goto zalloc_start;
                  }
          }
  
          /* Since we have locked the zone we may as well send back our stats */
          zone->uz_allocs += cache->uc_allocs;
          cache->uc_allocs = 0;
          zone->uz_frees += cache->uc_frees;
          cache->uc_frees = 0;
  
          /* Our old one is now a free bucket */
          if (cache->uc_allocbucket) {
                  KASSERT(cache->uc_allocbucket->ub_cnt == 0,
                      ("uma_zalloc_arg: Freeing a non free bucket."));
                  LIST_INSERT_HEAD(&zone->uz_free_bucket,
                      cache->uc_allocbucket, ub_link);
                  cache->uc_allocbucket = NULL;
          }
  
          /* Check the free list for a new alloc bucket */
          if ((bucket = LIST_FIRST(&zone->uz_full_bucket)) != 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();
  
          /* Bump up our uz_count so we get here less */
          if (zone->uz_count < BUCKET_MAX)
                  zone->uz_count++;
  
          /*
           * Now lets just fill a bucket and put it on the free list.  If that
           * works we'll restart the allocation from the begining.
           */
          if (zone_alloc_bucket(zone, flags)) {
                  ZONE_UNLOCK(zone);
                  goto zalloc_restart;
          }
          ZONE_UNLOCK(zone);
          /*
           * 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
  
          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;
  
          mtx_assert(&keg->uk_lock, MA_OWNED);
          slab = NULL;
  
          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 != 0) {
                          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;
                          if (flags & M_NOWAIT)
                                  break;
                          msleep(keg, &keg->uk_lock, PVM, "keglimit", 0);
                          continue;
                  }
                  keg->uk_recurse++;
                  slab = keg_alloc_slab(keg, zone, flags);
                  keg->uk_recurse--;
                  /*
                   * 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 inline void
  zone_relock(uma_zone_t zone, uma_keg_t keg)
  {
          if (zone->uz_lock != &keg->uk_lock) {
                  KEG_UNLOCK(keg);
                  ZONE_LOCK(zone);
          }
  }
  
  static inline void
  keg_relock(uma_keg_t keg, uma_zone_t zone)
  {
          if (zone->uz_lock != &keg->uk_lock) {
                  ZONE_UNLOCK(zone);
                  KEG_LOCK(keg);
          }
  }
  
  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);
          /*
           * This is to prevent us from recursively trying to allocate
           * buckets.  The problem is that if an allocation forces us to
           * grab a new bucket we will call page_alloc, which will go off
           * and cause the vm to allocate vm_map_entries.  If we need new
           * buckets there too we will recurse in kmem_alloc and bad
           * things happen.  So instead we return a NULL bucket, and make
           * the code that allocates buckets smart enough to deal with it
           */
          if (keg->uk_flags & UMA_ZFLAG_BUCKET && keg->uk_recurse != 0)
                  return (NULL);
  
          for (;;) {
                  slab = keg_fetch_slab(keg, zone, flags);
                  if (slab)
                          return (slab);
                  if (flags & (M_NOWAIT | M_NOVM))
                          break;
          }
          return (NULL);
  }
  
  /*
   * uma_zone_fetch_slab_multi:  Fetches a slab from one available keg.  Returns
   * with the keg locked.  Caller must call zone_relock() afterwards if the
   * zone lock is required.  On NULL the zone 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) {
                  slab = keg_fetch_slab(last, zone, flags);
                  if (slab)
                          return (slab);
                  zone_relock(zone, last);
                  last = NULL;
          }
          /*
           * 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_relock(keg, zone);
                          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++;
                          zone_relock(zone, 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->uz_flags |= UMA_ZFLAG_FULL;
                          msleep(zone, zone->uz_lock, PVM, "zonelimit", hz/100);
                          zone->uz_flags &= ~UMA_ZFLAG_FULL;
                          continue;
                  }
          }
          return (NULL);
  }
  
  static void *
  slab_alloc_item(uma_zone_t zone, uma_slab_t slab)
  {
          uma_keg_t keg;
          uma_slabrefcnt_t slabref;
          void *item;
          u_int8_t freei;
  
          keg = slab->us_keg;
          mtx_assert(&keg->uk_lock, MA_OWNED);
  
          freei = slab->us_firstfree;
          if (keg->uk_flags & UMA_ZONE_REFCNT) {
                  slabref = (uma_slabrefcnt_t)slab;
                  slab->us_firstfree = slabref->us_freelist[freei].us_item;
          } else {
                  slab->us_firstfree = slab->us_freelist[freei].us_item;
          }
          item = slab->us_data + (keg->uk_rsize * freei);
  
          slab->us_freecount--;
          keg->uk_free--;
  #ifdef INVARIANTS
          uma_dbg_alloc(zone, slab, item);
  #endif
          /* 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_alloc_bucket(uma_zone_t zone, int flags)
  {
          uma_bucket_t bucket;
          uma_slab_t slab;
          uma_keg_t keg;
          int16_t saved;
          int max, origflags = flags;
  
          /*
           * Try this zone's free list first so we don't allocate extra buckets.
           */
          if ((bucket = LIST_FIRST(&zone->uz_free_bucket)) != NULL) {
                  KASSERT(bucket->ub_cnt == 0,
                      ("zone_alloc_bucket: Bucket on free list is not empty."));
                  LIST_REMOVE(bucket, ub_link);
          } else {
                  int bflags;
  
                  bflags = (flags & ~M_ZERO);
                  if (zone->uz_flags & UMA_ZFLAG_CACHEONLY)
                          bflags |= M_NOVM;
  
                  ZONE_UNLOCK(zone);
                  bucket = bucket_alloc(zone->uz_count, bflags);
                  ZONE_LOCK(zone);
          }
  
          if (bucket == NULL) {
                  return (0);
          }
  
  #ifdef SMP
          /*
           * This code is here to limit the number of simultaneous bucket fills
           * for any given zone to the number of per cpu caches in this zone. This
           * is done so that we don't allocate more memory than we really need.
           */
          if (zone->uz_fills >= mp_ncpus)
                  goto done;
  
  #endif
          zone->uz_fills++;
  
          max = MIN(bucket->ub_entries, zone->uz_count);
          /* Try to keep the buckets totally full */
          saved = bucket->ub_cnt;
          slab = NULL;
          keg = NULL;
          while (bucket->ub_cnt < max &&
              (slab = zone->uz_slab(zone, keg, flags)) != NULL) {
                  keg = slab->us_keg;
                  while (slab->us_freecount && bucket->ub_cnt < max) {
                          bucket->ub_bucket[bucket->ub_cnt++] =
                              slab_alloc_item(zone, slab);
                  }
  
                  /* Don't block on the next fill */
                  flags |= M_NOWAIT;
          }
          if (slab)
                  zone_relock(zone, keg);
  
          /*
           * We unlock here because we need to call the zone's init.
           * It should be safe to unlock because the slab dealt with
           * above is already on the appropriate list within the keg
           * and the bucket we filled is not yet on any list, so we
           * own it.
           */
          if (zone->uz_init != NULL) {
                  int i;
  
                  ZONE_UNLOCK(zone);
                  for (i = saved; i < bucket->ub_cnt; i++)
                          if (zone->uz_init(bucket->ub_bucket[i], zone->uz_size,
                              origflags) != 0)
                                  break;
                  /*
                   * If we couldn't initialize the whole bucket, put the
                   * rest back onto the freelist.
                   */
                  if (i != bucket->ub_cnt) {
                          int j;
  
                          for (j = i; j < bucket->ub_cnt; j++) {
                                  zone_free_item(zone, bucket->ub_bucket[j],
                                      NULL, SKIP_FINI, 0);
  #ifdef INVARIANTS
                                  bucket->ub_bucket[j] = NULL;
  #endif
                          }
                          bucket->ub_cnt = i;
                  }
                  ZONE_LOCK(zone);
          }
  
          zone->uz_fills--;
          if (bucket->ub_cnt != 0) {
                  LIST_INSERT_HEAD(&zone->uz_full_bucket,
                      bucket, ub_link);
                  return (1);
          }
  #ifdef SMP
  done:
  #endif
          bucket_free(bucket);
  
          return (0);
  }
  /*
   * Allocates an item for an internal 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)
  {
          uma_slab_t slab;
          void *item;
  
          item = NULL;
  
  #ifdef UMA_DEBUG_ALLOC
          printf("INTERNAL: Allocating one item from %s(%p)\n", zone->uz_name, zone);
  #endif
          ZONE_LOCK(zone);
  
          slab = zone->uz_slab(zone, NULL, flags);
          if (slab == NULL) {
                  zone->uz_fails++;
                  ZONE_UNLOCK(zone);
                  return (NULL);
          }
  
          item = slab_alloc_item(zone, slab);
  
          zone_relock(zone, slab->us_keg);
          zone->uz_allocs++;
          ZONE_UNLOCK(zone);
  
          /*
           * 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,
                              ZFREE_STATFAIL | ZFREE_STATFREE);
                          return (NULL);
                  }
          }
          if (zone->uz_ctor != NULL) {
                  if (zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
                          zone_free_item(zone, item, udata, SKIP_DTOR,
                              ZFREE_STATFAIL | ZFREE_STATFREE);
                          return (NULL);
                  }
          }
          if (flags & M_ZERO)
                  bzero(item, zone->uz_size);
  
          return (item);
  }
  
  /* See uma.h */
  void
  uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
  {
          uma_cache_t cache;
          uma_bucket_t bucket;
          int bflags;
          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);
  
          if (zone->uz_dtor)
                  zone->uz_dtor(item, zone->uz_size, udata);
  
  #ifdef INVARIANTS
          ZONE_LOCK(zone);
          if (zone->uz_flags & UMA_ZONE_MALLOC)
                  uma_dbg_free(zone, udata, item);
          else
                  uma_dbg_free(zone, NULL, item);
          ZONE_UNLOCK(zone);
  #endif
          /*
           * 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_internal;
  
          /*
           * 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:
          bucket = cache->uc_freebucket;
  
          if (bucket) {
                  /*
                   * Do we have room in our bucket? It is OK for this uz count
                   * check to be slightly out of sync.
                   */
  
                  if (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;
                  } else if (cache->uc_allocbucket) {
  #ifdef UMA_DEBUG_ALLOC
                          printf("uma_zfree: Swapping buckets.\n");
  #endif
                          /*
                           * We have run out of space in our freebucket.
                           * See if we can switch with our alloc bucket.
                           */
                          if (cache->uc_allocbucket->ub_cnt <
                              cache->uc_freebucket->ub_cnt) {
                                  bucket = cache->uc_freebucket;
                                  cache->uc_freebucket = cache->uc_allocbucket;
                                  cache->uc_allocbucket = bucket;
                                  goto zfree_start;
                          }
                  }
          }
          /*
           * We can get here for two reasons:
           *
           * 1) The buckets are NULL
           * 2) The alloc and free buckets are both somewhat full.
           *
           * 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();
          ZONE_LOCK(zone);
          critical_enter();
          cpu = curcpu;
          cache = &zone->uz_cpu[cpu];
          if (cache->uc_freebucket != NULL) {
                  if (cache->uc_freebucket->ub_cnt <
                      cache->uc_freebucket->ub_entries) {
                          ZONE_UNLOCK(zone);
                          goto zfree_start;
                  }
                  if (cache->uc_allocbucket != NULL &&
                      (cache->uc_allocbucket->ub_cnt <
                      cache->uc_freebucket->ub_cnt)) {
                          ZONE_UNLOCK(zone);
                          goto zfree_start;
                  }
          }
  
          /* Since we have locked the zone we may as well send back our stats */
          zone->uz_allocs += cache->uc_allocs;
          cache->uc_allocs = 0;
          zone->uz_frees += cache->uc_frees;
          cache->uc_frees = 0;
  
          bucket = cache->uc_freebucket;
          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_full_bucket,
                      bucket, ub_link);
          }
          if ((bucket = LIST_FIRST(&zone->uz_free_bucket)) != NULL) {
                  LIST_REMOVE(bucket, ub_link);
                  ZONE_UNLOCK(zone);
                  cache->uc_freebucket = bucket;
                  goto zfree_start;
          }
          /* 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
          bflags = M_NOWAIT;
  
          if (zone->uz_flags & UMA_ZFLAG_CACHEONLY)
                  bflags |= M_NOVM;
          bucket = bucket_alloc(zone->uz_count, bflags);
          if (bucket) {
                  ZONE_LOCK(zone);
                  LIST_INSERT_HEAD(&zone->uz_free_bucket,
                      bucket, ub_link);
                  ZONE_UNLOCK(zone);
                  goto zfree_restart;
          }
  
          /*
           * If nothing else caught this, we'll just do an internal free.
           */
  zfree_internal:
          zone_free_item(zone, item, udata, SKIP_DTOR, ZFREE_STATFREE);
  
          return;
  }
  
  /*
   * Frees an item to an INTERNAL zone or allocates a free bucket
   *
   * 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, int flags)
  {
          uma_slab_t slab;
          uma_slabrefcnt_t slabref;
          uma_keg_t keg;
          u_int8_t *mem;
          u_int8_t freei;
          int clearfull;
  
          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);
  
          ZONE_LOCK(zone);
  
          if (flags & ZFREE_STATFAIL)
                  zone->uz_fails++;
          if (flags & ZFREE_STATFREE)
                  zone->uz_frees++;
  
          if (!(zone->uz_flags & UMA_ZONE_VTOSLAB)) {
                  mem = (u_int8_t *)((unsigned long)item & (~UMA_SLAB_MASK));
                  keg = zone_first_keg(zone); /* Must only be one. */
                  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 {
                  /* This prevents redundant lookups via free(). */
                  if ((zone->uz_flags & UMA_ZONE_MALLOC) && udata != NULL)
                          slab = (uma_slab_t)udata;
                  else
                          slab = vtoslab((vm_offset_t)item);
                  keg = slab->us_keg;
                  keg_relock(keg, zone);
          }
          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 stuff */
          freei = ((unsigned long)item - (unsigned long)slab->us_data)
                  / keg->uk_rsize;
  
  #ifdef INVARIANTS
          if (!skip)
                  uma_dbg_free(zone, slab, item);
  #endif
  
          if (keg->uk_flags & UMA_ZONE_REFCNT) {
                  slabref = (uma_slabrefcnt_t)slab;
                  slabref->us_freelist[freei].us_item = slab->us_firstfree;
          } else {
                  slab->us_freelist[freei].us_item = slab->us_firstfree;
          }
          slab->us_firstfree = freei;
          slab->us_freecount++;
  
          /* Zone statistics */
          keg->uk_free++;
  
          clearfull = 0;
          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);
          }
          if (clearfull) {
                  zone_relock(zone, keg);
                  zone->uz_flags &= ~UMA_ZFLAG_FULL;
                  wakeup(zone);
                  ZONE_UNLOCK(zone);
          } else
                  KEG_UNLOCK(keg);
  }
  
  /* See uma.h */
  void
  uma_zone_set_max(uma_zone_t zone, int nitems)
  {
          uma_keg_t keg;
  
          ZONE_LOCK(zone);
          keg = zone_first_keg(zone);
          keg->uk_maxpages = (nitems / keg->uk_ipers) * keg->uk_ppera;
          if (keg->uk_maxpages * keg->uk_ipers < nitems)
                  keg->uk_maxpages += keg->uk_ppera;
  
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  void
  uma_zone_set_init(uma_zone_t zone, uma_init uminit)
  {
          uma_keg_t keg;
  
          ZONE_LOCK(zone);
          keg = zone_first_keg(zone);
          KASSERT(keg->uk_pages == 0,
              ("uma_zone_set_init on non-empty keg"));
          keg->uk_init = uminit;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  void
  uma_zone_set_fini(uma_zone_t zone, uma_fini fini)
  {
          uma_keg_t keg;
  
          ZONE_LOCK(zone);
          keg = zone_first_keg(zone);
          KASSERT(keg->uk_pages == 0,
              ("uma_zone_set_fini on non-empty keg"));
          keg->uk_fini = fini;
          ZONE_UNLOCK(zone);
  }
  
  /* 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)
  {
  
          ZONE_LOCK(zone);
          zone_first_keg(zone)->uk_freef = freef;
          ZONE_UNLOCK(zone);
  }
  
  /* 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;
  
          ZONE_LOCK(zone);
          keg = zone_first_keg(zone);
          keg->uk_flags |= UMA_ZFLAG_PRIVALLOC;
          keg->uk_allocf = allocf;
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  int
  uma_zone_set_obj(uma_zone_t zone, struct vm_object *obj, int count)
  {
          uma_keg_t keg;
          vm_offset_t kva;
          int pages;
  
          keg = zone_first_keg(zone);
          pages = count / keg->uk_ipers;
  
          if (pages * keg->uk_ipers < count)
                  pages++;
  
          kva = kmem_alloc_nofault(kernel_map, pages * UMA_SLAB_SIZE);
  
          if (kva == 0)
                  return (0);
          if (obj == NULL) {
                  obj = vm_object_allocate(OBJT_DEFAULT,
                      pages);
          } else {
                  VM_OBJECT_LOCK_INIT(obj, "uma object");
                  _vm_object_allocate(OBJT_DEFAULT,
                      pages, obj);
          }
          ZONE_LOCK(zone);
          keg->uk_kva = kva;
          keg->uk_obj = obj;
          keg->uk_maxpages = pages;
          keg->uk_allocf = obj_alloc;
          keg->uk_flags |= UMA_ZONE_NOFREE | UMA_ZFLAG_PRIVALLOC;
          ZONE_UNLOCK(zone);
          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);
          ZONE_LOCK(zone);
          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--;
          }
          ZONE_UNLOCK(zone);
  }
  
  /* See uma.h */
  u_int32_t *
  uma_find_refcnt(uma_zone_t zone, void *item)
  {
          uma_slabrefcnt_t slabref;
          uma_keg_t keg;
          u_int32_t *refcnt;
          int idx;
  
          slabref = (uma_slabrefcnt_t)vtoslab((vm_offset_t)item &
              (~UMA_SLAB_MASK));
          keg = slabref->us_keg;
          KASSERT(slabref != NULL && slabref->us_keg->uk_flags & UMA_ZONE_REFCNT,
              ("uma_find_refcnt(): zone possibly not UMA_ZONE_REFCNT"));
          idx = ((unsigned long)item - (unsigned long)slabref->us_data)
              / keg->uk_rsize;
          refcnt = &slabref->us_freelist[idx].us_refcnt;
          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;
          u_int8_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,
                      ZFREE_STATFAIL | ZFREE_STATFREE);
          }
  
          return (mem);
  }
  
  void
  uma_large_free(uma_slab_t slab)
  {
          vsetobj((vm_offset_t)slab->us_data, kmem_object);
          page_free(slab->us_data, slab->us_size, slab->us_flags);
          zone_free_item(slabzone, slab, NULL, SKIP_NONE, ZFREE_STATFREE);
  }
  
  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, firstfree %d\n",
                  slab->us_keg, slab->us_data, slab->us_freecount,
                  slab->us_firstfree);
  }
  
  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 %d 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 %d\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);
          for (i = 0; i <= mp_maxid; i++) {
                  if (CPU_ABSENT(i))
                          continue;
                  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, u_int64_t *allocsp,
      u_int64_t *freesp)
  {
          uma_cache_t cache;
          u_int64_t allocs, frees;
          int cachefree, cpu;
  
          allocs = frees = 0;
          cachefree = 0;
          for (cpu = 0; cpu <= mp_maxid; cpu++) {
                  if (CPU_ABSENT(cpu))
                          continue;
                  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;
          if (cachefreep != NULL)
                  *cachefreep = cachefree;
          if (allocsp != NULL)
                  *allocsp = allocs;
          if (freesp != NULL)
                  *freesp = frees;
  }
  #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;
          char *buffer;
          int buflen, count, error, i;
  
          mtx_lock(&uma_mtx);
  restart:
          mtx_assert(&uma_mtx, MA_OWNED);
          count = 0;
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link)
                          count++;
          }
          mtx_unlock(&uma_mtx);
  
          buflen = sizeof(ush) + count * (sizeof(uth) + sizeof(ups) *
              (mp_maxid + 1)) + 1;
          buffer = malloc(buflen, M_TEMP, M_WAITOK | M_ZERO);
  
          mtx_lock(&uma_mtx);
          i = 0;
          LIST_FOREACH(kz, &uma_kegs, uk_link) {
                  LIST_FOREACH(z, &kz->uk_zones, uz_link)
                          i++;
          }
          if (i > count) {
                  free(buffer, M_TEMP);
                  goto restart;
          }
          count =  i;
  
          sbuf_new(&sbuf, buffer, buflen, SBUF_FIXEDLEN);
  
          /*
           * Insert stream header.
           */
          bzero(&ush, sizeof(ush));
          ush.ush_version = UMA_STREAM_VERSION;
          ush.ush_maxcpus = (mp_maxid + 1);
          ush.ush_count = count;
          if (sbuf_bcat(&sbuf, &ush, sizeof(ush)) < 0) {
                  mtx_unlock(&uma_mtx);
                  error = ENOMEM;
                  goto out;
          }
  
          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_full_bucket, 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;
                          if (sbuf_bcat(&sbuf, &uth, sizeof(uth)) < 0) {
                                  ZONE_UNLOCK(z);
                                  mtx_unlock(&uma_mtx);
                                  error = ENOMEM;
                                  goto out;
                          }
                          /*
                           * 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:
                                  if (sbuf_bcat(&sbuf, &ups, sizeof(ups)) < 0) {
                                          ZONE_UNLOCK(z);
                                          mtx_unlock(&uma_mtx);
                                          error = ENOMEM;
                                          goto out;
                                  }
                          }
                          ZONE_UNLOCK(z);
                  }
          }
          mtx_unlock(&uma_mtx);
          sbuf_finish(&sbuf);
          error = SYSCTL_OUT(req, sbuf_data(&sbuf), sbuf_len(&sbuf));
  out:
          free(buffer, M_TEMP);
          return (error);
  }
  
  #ifdef DDB
  DB_SHOW_COMMAND(uma, db_show_uma)
  {
          u_int64_t allocs, frees;
          uma_bucket_t bucket;
          uma_keg_t kz;
          uma_zone_t z;
          int cachefree;
  
          db_printf("%18s %8s %8s %8s %12s\n", "Zone", "Size", "Used", "Free",
              "Requests");
          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;
                                  cachefree = 0;
                          } else
                                  uma_zone_sumstat(z, &cachefree, &allocs,
                                      &frees);
                          if (!((z->uz_flags & UMA_ZONE_SECONDARY) &&
                              (LIST_FIRST(&kz->uk_zones) != z)))
                                  cachefree += kz->uk_free;
                          LIST_FOREACH(bucket, &z->uz_full_bucket, ub_link)
                                  cachefree += bucket->ub_cnt;
                          db_printf("%18s %8ju %8jd %8d %12ju\n", z->uz_name,
                              (uintmax_t)kz->uk_size,
                              (intmax_t)(allocs - frees), cachefree,
                              (uintmax_t)allocs);
                  }
          }
  }
  #endif

Cache object: 39c3e9259f2a17acb001b951c42acf2a