FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_pool.c

     /*      $NetBSD: subr_pool.c,v 1.124 2006/11/01 10:17:58 yamt Exp $     */
     
     /*-
      * Copyright (c) 1997, 1999, 2000 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Paul Kranenburg; by Jason R. Thorpe of the Numerical Aerospace
      * Simulation Facility, NASA Ames Research Center.
     *
     * 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, 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.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the NetBSD
     *      Foundation, Inc. and its contributors.
     * 4. Neither the name of The NetBSD Foundation nor the names of its
     *    contributors may be used to endorse or promote products derived
     *    from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     * ``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 FOUNDATION OR CONTRIBUTORS
     * 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.
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.124 2006/11/01 10:17:58 yamt Exp $");
    
    #include "opt_pool.h"
    #include "opt_poollog.h"
    #include "opt_lockdebug.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/errno.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/lock.h>
    #include <sys/pool.h>
    #include <sys/syslog.h>
    
    #include <uvm/uvm.h>
    
    /*
     * Pool resource management utility.
     *
     * Memory is allocated in pages which are split into pieces according to
     * the pool item size. Each page is kept on one of three lists in the
     * pool structure: `pr_emptypages', `pr_fullpages' and `pr_partpages',
     * for empty, full and partially-full pages respectively. The individual
     * pool items are on a linked list headed by `ph_itemlist' in each page
     * header. The memory for building the page list is either taken from
     * the allocated pages themselves (for small pool items) or taken from
     * an internal pool of page headers (`phpool').
     */
    
    /* List of all pools */
    LIST_HEAD(,pool) pool_head = LIST_HEAD_INITIALIZER(pool_head);
    
    /* Private pool for page header structures */
    #define PHPOOL_MAX      8
    static struct pool phpool[PHPOOL_MAX];
    #define PHPOOL_FREELIST_NELEM(idx)      (((idx) == 0) ? 0 : (1 << (idx)))
    
    #ifdef POOL_SUBPAGE
    /* Pool of subpages for use by normal pools. */
    static struct pool psppool;
    #endif
    
    static SLIST_HEAD(, pool_allocator) pa_deferinitq =
        SLIST_HEAD_INITIALIZER(pa_deferinitq);
    
    static void *pool_page_alloc_meta(struct pool *, int);
    static void pool_page_free_meta(struct pool *, void *);
    
    /* allocator for pool metadata */
    static struct pool_allocator pool_allocator_meta = {
            pool_page_alloc_meta, pool_page_free_meta,
            .pa_backingmapptr = &kmem_map,
    };
    
    /* # of seconds to retain page after last use */
    int pool_inactive_time = 10;
    
   /* Next candidate for drainage (see pool_drain()) */
   static struct pool      *drainpp;
   
   /* This spin lock protects both pool_head and drainpp. */
   struct simplelock pool_head_slock = SIMPLELOCK_INITIALIZER;
   
   typedef uint8_t pool_item_freelist_t;
   
   struct pool_item_header {
           /* Page headers */
           LIST_ENTRY(pool_item_header)
                                   ph_pagelist;    /* pool page list */
           SPLAY_ENTRY(pool_item_header)
                                   ph_node;        /* Off-page page headers */
           caddr_t                 ph_page;        /* this page's address */
           struct timeval          ph_time;        /* last referenced */
           union {
                   /* !PR_NOTOUCH */
                   struct {
                           LIST_HEAD(, pool_item)
                                   phu_itemlist;   /* chunk list for this page */
                   } phu_normal;
                   /* PR_NOTOUCH */
                   struct {
                           uint16_t
                                   phu_off;        /* start offset in page */
                           pool_item_freelist_t
                                   phu_firstfree;  /* first free item */
                           /*
                            * XXX it might be better to use
                            * a simple bitmap and ffs(3)
                            */
                   } phu_notouch;
           } ph_u;
           uint16_t                ph_nmissing;    /* # of chunks in use */
   };
   #define ph_itemlist     ph_u.phu_normal.phu_itemlist
   #define ph_off          ph_u.phu_notouch.phu_off
   #define ph_firstfree    ph_u.phu_notouch.phu_firstfree
   
   struct pool_item {
   #ifdef DIAGNOSTIC
           u_int pi_magic;
   #endif
   #define PI_MAGIC 0xdeadbeefU
           /* Other entries use only this list entry */
           LIST_ENTRY(pool_item)   pi_list;
   };
   
   #define POOL_NEEDS_CATCHUP(pp)                                          \
           ((pp)->pr_nitems < (pp)->pr_minitems)
   
   /*
    * Pool cache management.
    *
    * Pool caches provide a way for constructed objects to be cached by the
    * pool subsystem.  This can lead to performance improvements by avoiding
    * needless object construction/destruction; it is deferred until absolutely
    * necessary.
    *
    * Caches are grouped into cache groups.  Each cache group references
    * up to 16 constructed objects.  When a cache allocates an object
    * from the pool, it calls the object's constructor and places it into
    * a cache group.  When a cache group frees an object back to the pool,
    * it first calls the object's destructor.  This allows the object to
    * persist in constructed form while freed to the cache.
    *
    * Multiple caches may exist for each pool.  This allows a single
    * object type to have multiple constructed forms.  The pool references
    * each cache, so that when a pool is drained by the pagedaemon, it can
    * drain each individual cache as well.  Each time a cache is drained,
    * the most idle cache group is freed to the pool in its entirety.
    *
    * Pool caches are layed on top of pools.  By layering them, we can avoid
    * the complexity of cache management for pools which would not benefit
    * from it.
    */
   
   /* The cache group pool. */
   static struct pool pcgpool;
   
   static void     pool_cache_reclaim(struct pool_cache *, struct pool_pagelist *,
                                      struct pool_cache_grouplist *);
   static void     pcg_grouplist_free(struct pool_cache_grouplist *);
   
   static int      pool_catchup(struct pool *);
   static void     pool_prime_page(struct pool *, caddr_t,
                       struct pool_item_header *);
   static void     pool_update_curpage(struct pool *);
   
   static int      pool_grow(struct pool *, int);
   static void     *pool_allocator_alloc(struct pool *, int);
   static void     pool_allocator_free(struct pool *, void *);
   
   static void pool_print_pagelist(struct pool *, struct pool_pagelist *,
           void (*)(const char *, ...));
   static void pool_print1(struct pool *, const char *,
           void (*)(const char *, ...));
   
   static int pool_chk_page(struct pool *, const char *,
                            struct pool_item_header *);
   
   /*
    * Pool log entry. An array of these is allocated in pool_init().
    */
   struct pool_log {
           const char      *pl_file;
           long            pl_line;
           int             pl_action;
   #define PRLOG_GET       1
   #define PRLOG_PUT       2
           void            *pl_addr;
   };
   
   #ifdef POOL_DIAGNOSTIC
   /* Number of entries in pool log buffers */
   #ifndef POOL_LOGSIZE
   #define POOL_LOGSIZE    10
   #endif
   
   int pool_logsize = POOL_LOGSIZE;
   
   static inline void
   pr_log(struct pool *pp, void *v, int action, const char *file, long line)
   {
           int n = pp->pr_curlogentry;
           struct pool_log *pl;
   
           if ((pp->pr_roflags & PR_LOGGING) == 0)
                   return;
   
           /*
            * Fill in the current entry. Wrap around and overwrite
            * the oldest entry if necessary.
            */
           pl = &pp->pr_log[n];
           pl->pl_file = file;
           pl->pl_line = line;
           pl->pl_action = action;
           pl->pl_addr = v;
           if (++n >= pp->pr_logsize)
                   n = 0;
           pp->pr_curlogentry = n;
   }
   
   static void
   pr_printlog(struct pool *pp, struct pool_item *pi,
       void (*pr)(const char *, ...))
   {
           int i = pp->pr_logsize;
           int n = pp->pr_curlogentry;
   
           if ((pp->pr_roflags & PR_LOGGING) == 0)
                   return;
   
           /*
            * Print all entries in this pool's log.
            */
           while (i-- > 0) {
                   struct pool_log *pl = &pp->pr_log[n];
                   if (pl->pl_action != 0) {
                           if (pi == NULL || pi == pl->pl_addr) {
                                   (*pr)("\tlog entry %d:\n", i);
                                   (*pr)("\t\taction = %s, addr = %p\n",
                                       pl->pl_action == PRLOG_GET ? "get" : "put",
                                       pl->pl_addr);
                                   (*pr)("\t\tfile: %s at line %lu\n",
                                       pl->pl_file, pl->pl_line);
                           }
                   }
                   if (++n >= pp->pr_logsize)
                           n = 0;
           }
   }
   
   static inline void
   pr_enter(struct pool *pp, const char *file, long line)
   {
   
           if (__predict_false(pp->pr_entered_file != NULL)) {
                   printf("pool %s: reentrancy at file %s line %ld\n",
                       pp->pr_wchan, file, line);
                   printf("         previous entry at file %s line %ld\n",
                       pp->pr_entered_file, pp->pr_entered_line);
                   panic("pr_enter");
           }
   
           pp->pr_entered_file = file;
           pp->pr_entered_line = line;
   }
   
   static inline void
   pr_leave(struct pool *pp)
   {
   
           if (__predict_false(pp->pr_entered_file == NULL)) {
                   printf("pool %s not entered?\n", pp->pr_wchan);
                   panic("pr_leave");
           }
   
           pp->pr_entered_file = NULL;
           pp->pr_entered_line = 0;
   }
   
   static inline void
   pr_enter_check(struct pool *pp, void (*pr)(const char *, ...))
   {
   
           if (pp->pr_entered_file != NULL)
                   (*pr)("\n\tcurrently entered from file %s line %ld\n",
                       pp->pr_entered_file, pp->pr_entered_line);
   }
   #else
   #define pr_log(pp, v, action, file, line)
   #define pr_printlog(pp, pi, pr)
   #define pr_enter(pp, file, line)
   #define pr_leave(pp)
   #define pr_enter_check(pp, pr)
   #endif /* POOL_DIAGNOSTIC */
   
   static inline int
   pr_item_notouch_index(const struct pool *pp, const struct pool_item_header *ph,
       const void *v)
   {
           const char *cp = v;
           int idx;
   
           KASSERT(pp->pr_roflags & PR_NOTOUCH);
           idx = (cp - ph->ph_page - ph->ph_off) / pp->pr_size;
           KASSERT(idx < pp->pr_itemsperpage);
           return idx;
   }
   
   #define PR_FREELIST_ALIGN(p) \
           roundup((uintptr_t)(p), sizeof(pool_item_freelist_t))
   #define PR_FREELIST(ph) ((pool_item_freelist_t *)PR_FREELIST_ALIGN((ph) + 1))
   #define PR_INDEX_USED   ((pool_item_freelist_t)-1)
   #define PR_INDEX_EOL    ((pool_item_freelist_t)-2)
   
   static inline void
   pr_item_notouch_put(const struct pool *pp, struct pool_item_header *ph,
       void *obj)
   {
           int idx = pr_item_notouch_index(pp, ph, obj);
           pool_item_freelist_t *freelist = PR_FREELIST(ph);
   
           KASSERT(freelist[idx] == PR_INDEX_USED);
           freelist[idx] = ph->ph_firstfree;
           ph->ph_firstfree = idx;
   }
   
   static inline void *
   pr_item_notouch_get(const struct pool *pp, struct pool_item_header *ph)
   {
           int idx = ph->ph_firstfree;
           pool_item_freelist_t *freelist = PR_FREELIST(ph);
   
           KASSERT(freelist[idx] != PR_INDEX_USED);
           ph->ph_firstfree = freelist[idx];
           freelist[idx] = PR_INDEX_USED;
   
           return ph->ph_page + ph->ph_off + idx * pp->pr_size;
   }
   
   static inline int
   phtree_compare(struct pool_item_header *a, struct pool_item_header *b)
   {
   
           /*
            * we consider pool_item_header with smaller ph_page bigger.
            * (this unnatural ordering is for the benefit of pr_find_pagehead.)
            */
   
           if (a->ph_page < b->ph_page)
                   return (1);
           else if (a->ph_page > b->ph_page)
                   return (-1);
           else
                   return (0);
   }
   
   SPLAY_PROTOTYPE(phtree, pool_item_header, ph_node, phtree_compare);
   SPLAY_GENERATE(phtree, pool_item_header, ph_node, phtree_compare);
   
   /*
    * Return the pool page header based on item address.
    */
   static inline struct pool_item_header *
   pr_find_pagehead(struct pool *pp, void *v)
   {
           struct pool_item_header *ph, tmp;
   
           if ((pp->pr_roflags & PR_NOALIGN) != 0) {
                   tmp.ph_page = (caddr_t)(uintptr_t)v;
                   ph = SPLAY_FIND(phtree, &pp->pr_phtree, &tmp);
                   if (ph == NULL) {
                           ph = SPLAY_ROOT(&pp->pr_phtree);
                           if (ph != NULL && phtree_compare(&tmp, ph) >= 0) {
                                   ph = SPLAY_NEXT(phtree, &pp->pr_phtree, ph);
                           }
                           KASSERT(ph == NULL || phtree_compare(&tmp, ph) < 0);
                   }
           } else {
                   caddr_t page =
                       (caddr_t)((uintptr_t)v & pp->pr_alloc->pa_pagemask);
   
                   if ((pp->pr_roflags & PR_PHINPAGE) != 0) {
                           ph = (void *)(page + pp->pr_phoffset);
                   } else {
                           tmp.ph_page = page;
                           ph = SPLAY_FIND(phtree, &pp->pr_phtree, &tmp);
                   }
           }
   
           KASSERT(ph == NULL || ((pp->pr_roflags & PR_PHINPAGE) != 0) ||
               (ph->ph_page <= (char *)v &&
               (char *)v < ph->ph_page + pp->pr_alloc->pa_pagesz));
           return ph;
   }
   
   static void
   pr_pagelist_free(struct pool *pp, struct pool_pagelist *pq)
   {
           struct pool_item_header *ph;
           int s;
   
           while ((ph = LIST_FIRST(pq)) != NULL) {
                   LIST_REMOVE(ph, ph_pagelist);
                   pool_allocator_free(pp, ph->ph_page);
                   if ((pp->pr_roflags & PR_PHINPAGE) == 0) {
                           s = splvm();
                           pool_put(pp->pr_phpool, ph);
                           splx(s);
                   }
           }
   }
   
   /*
    * Remove a page from the pool.
    */
   static inline void
   pr_rmpage(struct pool *pp, struct pool_item_header *ph,
        struct pool_pagelist *pq)
   {
   
           LOCK_ASSERT(simple_lock_held(&pp->pr_slock));
   
           /*
            * If the page was idle, decrement the idle page count.
            */
           if (ph->ph_nmissing == 0) {
   #ifdef DIAGNOSTIC
                   if (pp->pr_nidle == 0)
                           panic("pr_rmpage: nidle inconsistent");
                   if (pp->pr_nitems < pp->pr_itemsperpage)
                           panic("pr_rmpage: nitems inconsistent");
   #endif
                   pp->pr_nidle--;
           }
   
           pp->pr_nitems -= pp->pr_itemsperpage;
   
           /*
            * Unlink the page from the pool and queue it for release.
            */
           LIST_REMOVE(ph, ph_pagelist);
           if ((pp->pr_roflags & PR_PHINPAGE) == 0)
                   SPLAY_REMOVE(phtree, &pp->pr_phtree, ph);
           LIST_INSERT_HEAD(pq, ph, ph_pagelist);
   
           pp->pr_npages--;
           pp->pr_npagefree++;
   
           pool_update_curpage(pp);
   }
   
   static boolean_t
   pa_starved_p(struct pool_allocator *pa)
   {
   
           if (pa->pa_backingmap != NULL) {
                   return vm_map_starved_p(pa->pa_backingmap);
           }
           return FALSE;
   }
   
   static int
   pool_reclaim_callback(struct callback_entry *ce, void *obj, void *arg)
   {
           struct pool *pp = obj;
           struct pool_allocator *pa = pp->pr_alloc;
   
           KASSERT(&pp->pr_reclaimerentry == ce);
           pool_reclaim(pp);
           if (!pa_starved_p(pa)) {
                   return CALLBACK_CHAIN_ABORT;
           }
           return CALLBACK_CHAIN_CONTINUE;
   }
   
   static void
   pool_reclaim_register(struct pool *pp)
   {
           struct vm_map *map = pp->pr_alloc->pa_backingmap;
           int s;
   
           if (map == NULL) {
                   return;
           }
   
           s = splvm(); /* not necessary for INTRSAFE maps, but don't care. */
           callback_register(&vm_map_to_kernel(map)->vmk_reclaim_callback,
               &pp->pr_reclaimerentry, pp, pool_reclaim_callback);
           splx(s);
   }
   
   static void
   pool_reclaim_unregister(struct pool *pp)
   {
           struct vm_map *map = pp->pr_alloc->pa_backingmap;
           int s;
   
           if (map == NULL) {
                   return;
           }
   
           s = splvm(); /* not necessary for INTRSAFE maps, but don't care. */
           callback_unregister(&vm_map_to_kernel(map)->vmk_reclaim_callback,
               &pp->pr_reclaimerentry);
           splx(s);
   }
   
   static void
   pa_reclaim_register(struct pool_allocator *pa)
   {
           struct vm_map *map = *pa->pa_backingmapptr;
           struct pool *pp;
   
           KASSERT(pa->pa_backingmap == NULL);
           if (map == NULL) {
                   SLIST_INSERT_HEAD(&pa_deferinitq, pa, pa_q);
                   return;
           }
           pa->pa_backingmap = map;
           TAILQ_FOREACH(pp, &pa->pa_list, pr_alloc_list) {
                   pool_reclaim_register(pp);
           }
   }
   
   /*
    * Initialize all the pools listed in the "pools" link set.
    */
   void
   pool_subsystem_init(void)
   {
           struct pool_allocator *pa;
           __link_set_decl(pools, struct link_pool_init);
           struct link_pool_init * const *pi;
   
           __link_set_foreach(pi, pools)
                   pool_init((*pi)->pp, (*pi)->size, (*pi)->align,
                       (*pi)->align_offset, (*pi)->flags, (*pi)->wchan,
                       (*pi)->palloc);
   
           while ((pa = SLIST_FIRST(&pa_deferinitq)) != NULL) {
                   KASSERT(pa->pa_backingmapptr != NULL);
                   KASSERT(*pa->pa_backingmapptr != NULL);
                   SLIST_REMOVE_HEAD(&pa_deferinitq, pa_q);
                   pa_reclaim_register(pa);
           }
   }
   
   /*
    * Initialize the given pool resource structure.
    *
    * We export this routine to allow other kernel parts to declare
    * static pools that must be initialized before malloc() is available.
    */
   void
   pool_init(struct pool *pp, size_t size, u_int align, u_int ioff, int flags,
       const char *wchan, struct pool_allocator *palloc)
   {
   #ifdef DEBUG
           struct pool *pp1;
   #endif
           size_t trysize, phsize;
           int off, slack, s;
   
           KASSERT((1UL << (CHAR_BIT * sizeof(pool_item_freelist_t))) - 2 >=
               PHPOOL_FREELIST_NELEM(PHPOOL_MAX - 1));
   
   #ifdef DEBUG
           /*
            * Check that the pool hasn't already been initialised and
            * added to the list of all pools.
            */
           LIST_FOREACH(pp1, &pool_head, pr_poollist) {
                   if (pp == pp1)
                           panic("pool_init: pool %s already initialised",
                               wchan);
           }
   #endif
   
   #ifdef POOL_DIAGNOSTIC
           /*
            * Always log if POOL_DIAGNOSTIC is defined.
            */
           if (pool_logsize != 0)
                   flags |= PR_LOGGING;
   #endif
   
           if (palloc == NULL)
                   palloc = &pool_allocator_kmem;
   #ifdef POOL_SUBPAGE
           if (size > palloc->pa_pagesz) {
                   if (palloc == &pool_allocator_kmem)
                           palloc = &pool_allocator_kmem_fullpage;
                   else if (palloc == &pool_allocator_nointr)
                           palloc = &pool_allocator_nointr_fullpage;
           }               
   #endif /* POOL_SUBPAGE */
           if ((palloc->pa_flags & PA_INITIALIZED) == 0) {
                   if (palloc->pa_pagesz == 0)
                           palloc->pa_pagesz = PAGE_SIZE;
   
                   TAILQ_INIT(&palloc->pa_list);
   
                   simple_lock_init(&palloc->pa_slock);
                   palloc->pa_pagemask = ~(palloc->pa_pagesz - 1);
                   palloc->pa_pageshift = ffs(palloc->pa_pagesz) - 1;
   
                   if (palloc->pa_backingmapptr != NULL) {
                           pa_reclaim_register(palloc);
                   }
                   palloc->pa_flags |= PA_INITIALIZED;
           }
   
           if (align == 0)
                   align = ALIGN(1);
   
           if ((flags & PR_NOTOUCH) == 0 && size < sizeof(struct pool_item))
                   size = sizeof(struct pool_item);
   
           size = roundup(size, align);
   #ifdef DIAGNOSTIC
           if (size > palloc->pa_pagesz)
                   panic("pool_init: pool item size (%zu) too large", size);
   #endif
   
           /*
            * Initialize the pool structure.
            */
           LIST_INIT(&pp->pr_emptypages);
           LIST_INIT(&pp->pr_fullpages);
           LIST_INIT(&pp->pr_partpages);
           LIST_INIT(&pp->pr_cachelist);
           pp->pr_curpage = NULL;
           pp->pr_npages = 0;
           pp->pr_minitems = 0;
           pp->pr_minpages = 0;
           pp->pr_maxpages = UINT_MAX;
           pp->pr_roflags = flags;
           pp->pr_flags = 0;
           pp->pr_size = size;
           pp->pr_align = align;
           pp->pr_wchan = wchan;
           pp->pr_alloc = palloc;
           pp->pr_nitems = 0;
           pp->pr_nout = 0;
           pp->pr_hardlimit = UINT_MAX;
           pp->pr_hardlimit_warning = NULL;
           pp->pr_hardlimit_ratecap.tv_sec = 0;
           pp->pr_hardlimit_ratecap.tv_usec = 0;
           pp->pr_hardlimit_warning_last.tv_sec = 0;
           pp->pr_hardlimit_warning_last.tv_usec = 0;
           pp->pr_drain_hook = NULL;
           pp->pr_drain_hook_arg = NULL;
   
           /*
            * Decide whether to put the page header off page to avoid
            * wasting too large a part of the page or too big item.
            * Off-page page headers go on a hash table, so we can match
            * a returned item with its header based on the page address.
            * We use 1/16 of the page size and about 8 times of the item
            * size as the threshold (XXX: tune)
            *
            * However, we'll put the header into the page if we can put
            * it without wasting any items.
            *
            * Silently enforce `0 <= ioff < align'.
            */
           pp->pr_itemoffset = ioff %= align;
           /* See the comment below about reserved bytes. */
           trysize = palloc->pa_pagesz - ((align - ioff) % align);
           phsize = ALIGN(sizeof(struct pool_item_header));
           if ((pp->pr_roflags & (PR_NOTOUCH | PR_NOALIGN)) == 0 &&
               (pp->pr_size < MIN(palloc->pa_pagesz / 16, phsize << 3) ||
               trysize / pp->pr_size == (trysize - phsize) / pp->pr_size)) {
                   /* Use the end of the page for the page header */
                   pp->pr_roflags |= PR_PHINPAGE;
                   pp->pr_phoffset = off = palloc->pa_pagesz - phsize;
           } else {
                   /* The page header will be taken from our page header pool */
                   pp->pr_phoffset = 0;
                   off = palloc->pa_pagesz;
                   SPLAY_INIT(&pp->pr_phtree);
           }
   
           /*
            * Alignment is to take place at `ioff' within the item. This means
            * we must reserve up to `align - 1' bytes on the page to allow
            * appropriate positioning of each item.
            */
           pp->pr_itemsperpage = (off - ((align - ioff) % align)) / pp->pr_size;
           KASSERT(pp->pr_itemsperpage != 0);
           if ((pp->pr_roflags & PR_NOTOUCH)) {
                   int idx;
   
                   for (idx = 0; pp->pr_itemsperpage > PHPOOL_FREELIST_NELEM(idx);
                       idx++) {
                           /* nothing */
                   }
                   if (idx >= PHPOOL_MAX) {
                           /*
                            * if you see this panic, consider to tweak
                            * PHPOOL_MAX and PHPOOL_FREELIST_NELEM.
                            */
                           panic("%s: too large itemsperpage(%d) for PR_NOTOUCH",
                               pp->pr_wchan, pp->pr_itemsperpage);
                   }
                   pp->pr_phpool = &phpool[idx];
           } else if ((pp->pr_roflags & PR_PHINPAGE) == 0) {
                   pp->pr_phpool = &phpool[0];
           }
   #if defined(DIAGNOSTIC)
           else {
                   pp->pr_phpool = NULL;
           }
   #endif
   
           /*
            * Use the slack between the chunks and the page header
            * for "cache coloring".
            */
           slack = off - pp->pr_itemsperpage * pp->pr_size;
           pp->pr_maxcolor = (slack / align) * align;
           pp->pr_curcolor = 0;
   
           pp->pr_nget = 0;
           pp->pr_nfail = 0;
           pp->pr_nput = 0;
           pp->pr_npagealloc = 0;
           pp->pr_npagefree = 0;
           pp->pr_hiwat = 0;
           pp->pr_nidle = 0;
   
   #ifdef POOL_DIAGNOSTIC
           if (flags & PR_LOGGING) {
                   if (kmem_map == NULL ||
                       (pp->pr_log = malloc(pool_logsize * sizeof(struct pool_log),
                        M_TEMP, M_NOWAIT)) == NULL)
                           pp->pr_roflags &= ~PR_LOGGING;
                   pp->pr_curlogentry = 0;
                   pp->pr_logsize = pool_logsize;
           }
   #endif
   
           pp->pr_entered_file = NULL;
           pp->pr_entered_line = 0;
   
           simple_lock_init(&pp->pr_slock);
   
           /*
            * Initialize private page header pool and cache magazine pool if we
            * haven't done so yet.
            * XXX LOCKING.
            */
           if (phpool[0].pr_size == 0) {
                   int idx;
                   for (idx = 0; idx < PHPOOL_MAX; idx++) {
                           static char phpool_names[PHPOOL_MAX][6+1+6+1];
                           int nelem;
                           size_t sz;
   
                           nelem = PHPOOL_FREELIST_NELEM(idx);
                           snprintf(phpool_names[idx], sizeof(phpool_names[idx]),
                               "phpool-%d", nelem);
                           sz = sizeof(struct pool_item_header);
                           if (nelem) {
                                   sz = PR_FREELIST_ALIGN(sz)
                                       + nelem * sizeof(pool_item_freelist_t);
                           }
                           pool_init(&phpool[idx], sz, 0, 0, 0,
                               phpool_names[idx], &pool_allocator_meta);
                   }
   #ifdef POOL_SUBPAGE
                   pool_init(&psppool, POOL_SUBPAGE, POOL_SUBPAGE, 0,
                       PR_RECURSIVE, "psppool", &pool_allocator_meta);
   #endif
                   pool_init(&pcgpool, sizeof(struct pool_cache_group), 0, 0,
                       0, "pcgpool", &pool_allocator_meta);
           }
   
           /* Insert into the list of all pools. */
           simple_lock(&pool_head_slock);
           LIST_INSERT_HEAD(&pool_head, pp, pr_poollist);
           simple_unlock(&pool_head_slock);
   
           /* Insert this into the list of pools using this allocator. */
           s = splvm();
           simple_lock(&palloc->pa_slock);
           TAILQ_INSERT_TAIL(&palloc->pa_list, pp, pr_alloc_list);
           simple_unlock(&palloc->pa_slock);
           splx(s);
           pool_reclaim_register(pp);
   }
   
   /*
    * De-commision a pool resource.
    */
   void
   pool_destroy(struct pool *pp)
   {
           struct pool_pagelist pq;
           struct pool_item_header *ph;
           int s;
   
           /* Remove from global pool list */
           simple_lock(&pool_head_slock);
           LIST_REMOVE(pp, pr_poollist);
           if (drainpp == pp)
                   drainpp = NULL;
           simple_unlock(&pool_head_slock);
   
           /* Remove this pool from its allocator's list of pools. */
           pool_reclaim_unregister(pp);
           s = splvm();
           simple_lock(&pp->pr_alloc->pa_slock);
           TAILQ_REMOVE(&pp->pr_alloc->pa_list, pp, pr_alloc_list);
           simple_unlock(&pp->pr_alloc->pa_slock);
           splx(s);
   
           s = splvm();
           simple_lock(&pp->pr_slock);
   
           KASSERT(LIST_EMPTY(&pp->pr_cachelist));
   
   #ifdef DIAGNOSTIC
           if (pp->pr_nout != 0) {
                   pr_printlog(pp, NULL, printf);
                   panic("pool_destroy: pool busy: still out: %u",
                       pp->pr_nout);
           }
   #endif
   
           KASSERT(LIST_EMPTY(&pp->pr_fullpages));
           KASSERT(LIST_EMPTY(&pp->pr_partpages));
   
           /* Remove all pages */
           LIST_INIT(&pq);
           while ((ph = LIST_FIRST(&pp->pr_emptypages)) != NULL)
                   pr_rmpage(pp, ph, &pq);
   
           simple_unlock(&pp->pr_slock);
           splx(s);
   
           pr_pagelist_free(pp, &pq);
   
   #ifdef POOL_DIAGNOSTIC
           if ((pp->pr_roflags & PR_LOGGING) != 0)
                   free(pp->pr_log, M_TEMP);
   #endif
   }
   
   void
   pool_set_drain_hook(struct pool *pp, void (*fn)(void *, int), void *arg)
   {
   
           /* XXX no locking -- must be used just after pool_init() */
   #ifdef DIAGNOSTIC
           if (pp->pr_drain_hook != NULL)
                   panic("pool_set_drain_hook(%s): already set", pp->pr_wchan);
   #endif
           pp->pr_drain_hook = fn;
           pp->pr_drain_hook_arg = arg;
   }
   
   static struct pool_item_header *
   pool_alloc_item_header(struct pool *pp, caddr_t storage, int flags)
   {
           struct pool_item_header *ph;
           int s;
   
           LOCK_ASSERT(simple_lock_held(&pp->pr_slock) == 0);
   
           if ((pp->pr_roflags & PR_PHINPAGE) != 0)
                   ph = (struct pool_item_header *) (storage + pp->pr_phoffset);
           else {
                   s = splvm();
                   ph = pool_get(pp->pr_phpool, flags);
                   splx(s);
           }
   
           return (ph);
   }
   
   /*
    * Grab an item from the pool; must be called at appropriate spl level
    */
   void *
   #ifdef POOL_DIAGNOSTIC
   _pool_get(struct pool *pp, int flags, const char *file, long line)
   #else
   pool_get(struct pool *pp, int flags)
   #endif
   {
           struct pool_item *pi;
           struct pool_item_header *ph;
           void *v;
   
   #ifdef DIAGNOSTIC
           if (__predict_false(pp->pr_itemsperpage == 0))
                   panic("pool_get: pool %p: pr_itemsperpage is zero, "
                       "pool not initialized?", pp);
           if (__predict_false(curlwp == NULL && doing_shutdown == 0 &&
                               (flags & PR_WAITOK) != 0))
                   panic("pool_get: %s: must have NOWAIT", pp->pr_wchan);
   
   #endif /* DIAGNOSTIC */
   #ifdef LOCKDEBUG
           if (flags & PR_WAITOK)
                   ASSERT_SLEEPABLE(NULL, "pool_get(PR_WAITOK)");
           SCHED_ASSERT_UNLOCKED();
   #endif
   
           simple_lock(&pp->pr_slock);
           pr_enter(pp, file, line);
   
    startover:
           /*
            * Check to see if we've reached the hard limit.  If we have,
            * and we can wait, then wait until an item has been returned to
            * the pool.
            */
   #ifdef DIAGNOSTIC
           if (__predict_false(pp->pr_nout > pp->pr_hardlimit)) {
                   pr_leave(pp);
                   simple_unlock(&pp->pr_slock);
                   panic("pool_get: %s: crossed hard limit", pp->pr_wchan);
           }
   #endif
           if (__predict_false(pp->pr_nout == pp->pr_hardlimit)) {
                   if (pp->pr_drain_hook != NULL) {
                           /*
                            * Since the drain hook is going to free things
                            * back to the pool, unlock, call the hook, re-lock,
                            * and check the hardlimit condition again.
                            */
                           pr_leave(pp);
                           simple_unlock(&pp->pr_slock);
                           (*pp->pr_drain_hook)(pp->pr_drain_hook_arg, flags);
                           simple_lock(&pp->pr_slock);
                           pr_enter(pp, file, line);
                           if (pp->pr_nout < pp->pr_hardlimit)
                                   goto startover;
                   }
   
                   if ((flags & PR_WAITOK) && !(flags & PR_LIMITFAIL)) {
                           /*
                            * XXX: A warning isn't logged in this case.  Should
                            * it be?
                            */
                           pp->pr_flags |= PR_WANTED;
                           pr_leave(pp);
                           ltsleep(pp, PSWP, pp->pr_wchan, 0, &pp->pr_slock);
                           pr_enter(pp, file, line);
                           goto startover;
                   }
   
                   /*
                    * Log a message that the hard limit has been hit.
                    */
                   if (pp->pr_hardlimit_warning != NULL &&
                       ratecheck(&pp->pr_hardlimit_warning_last,
                                 &pp->pr_hardlimit_ratecap))
                           log(LOG_ERR, "%s\n", pp->pr_hardlimit_warning);
   
                   pp->pr_nfail++;
   
                   pr_leave(pp);
                   simple_unlock(&pp->pr_slock);
                   return (NULL);
           }
   
           /*
            * The convention we use is that if `curpage' is not NULL, then
            * it points at a non-empty bucket. In particular, `curpage'
            * never points at a page header which has PR_PHINPAGE set and
            * has no items in its bucket.
            */
          if ((ph = pp->pr_curpage) == NULL) {
                  int error;
  
  #ifdef DIAGNOSTIC
                  if (pp->pr_nitems != 0) {
                          simple_unlock(&pp->pr_slock);
                          printf("pool_get: %s: curpage NULL, nitems %u\n",
                              pp->pr_wchan, pp->pr_nitems);
                          panic("pool_get: nitems inconsistent");
                  }
  #endif
  
                  /*
                   * Call the back-end page allocator for more memory.
                   * Release the pool lock, as the back-end page allocator
                   * may block.
                   */
                  pr_leave(pp);
                  error = pool_grow(pp, flags);
                  pr_enter(pp, file, line);
                  if (error != 0) {
                          /*
                           * We were unable to allocate a page or item
                           * header, but we released the lock during
                           * allocation, so perhaps items were freed
                           * back to the pool.  Check for this case.
                           */
                          if (pp->pr_curpage != NULL)
                                  goto startover;
  
                          pp->pr_nfail++;
                          pr_leave(pp);
                          simple_unlock(&pp->pr_slock);
                          return (NULL);
                  }
  
                  /* Start the allocation process over. */
                  goto startover;
          }
          if (pp->pr_roflags & PR_NOTOUCH) {
  #ifdef DIAGNOSTIC
                  if (__predict_false(ph->ph_nmissing == pp->pr_itemsperpage)) {
                          pr_leave(pp);
                          simple_unlock(&pp->pr_slock);
                          panic("pool_get: %s: page empty", pp->pr_wchan);
                  }
  #endif
                  v = pr_item_notouch_get(pp, ph);
  #ifdef POOL_DIAGNOSTIC
                  pr_log(pp, v, PRLOG_GET, file, line);
  #endif
          } else {
                  v = pi = LIST_FIRST(&ph->ph_itemlist);
                  if (__predict_false(v == NULL)) {
                          pr_leave(pp);
                          simple_unlock(&pp->pr_slock);
                          panic("pool_get: %s: page empty", pp->pr_wchan);
                  }
  #ifdef DIAGNOSTIC
                  if (__predict_false(pp->pr_nitems == 0)) {
                          pr_leave(pp);
                          simple_unlock(&pp->pr_slock);
                          printf("pool_get: %s: items on itemlist, nitems %u\n",
                              pp->pr_wchan, pp->pr_nitems);
                          panic("pool_get: nitems inconsistent");
                  }
  #endif
  
  #ifdef POOL_DIAGNOSTIC
                  pr_log(pp, v, PRLOG_GET, file, line);
  #endif
  
  #ifdef DIAGNOSTIC
                  if (__predict_false(pi->pi_magic != PI_MAGIC)) {
                          pr_printlog(pp, pi, printf);
                          panic("pool_get(%s): free list modified: "
                              "magic=%x; page %p; item addr %p\n",
                              pp->pr_wchan, pi->pi_magic, ph->ph_page, pi);
                  }
  #endif
  
                  /*
                   * Remove from item list.
                   */
                  LIST_REMOVE(pi, pi_list);
          }
          pp->pr_nitems--;
          pp->pr_nout++;
          if (ph->ph_nmissing == 0) {
  #ifdef DIAGNOSTIC
                  if (__predict_false(pp->pr_nidle == 0))
                          panic("pool_get: nidle inconsistent");
  #endif
                  pp->pr_nidle--;
  
                  /*
                   * This page was previously empty.  Move it to the list of
                   * partially-full pages.  This page is already curpage.
                   */
                  LIST_REMOVE(ph, ph_pagelist);
                  LIST_INSERT_HEAD(&pp->pr_partpages, ph, ph_pagelist);
          }
          ph->ph_nmissing++;
          if (ph->ph_nmissing == pp->pr_itemsperpage) {
  #ifdef DIAGNOSTIC
                  if (__predict_false((pp->pr_roflags & PR_NOTOUCH) == 0 &&
                      !LIST_EMPTY(&ph->ph_itemlist))) {
                          pr_leave(pp);
                          simple_unlock(&pp->pr_slock);
                          panic("pool_get: %s: nmissing inconsistent",
                              pp->pr_wchan);
                  }
  #endif
                  /*
                   * This page is now full.  Move it to the full list
                   * and select a new current page.
                   */
                  LIST_REMOVE(ph, ph_pagelist);
                  LIST_INSERT_HEAD(&pp->pr_fullpages, ph, ph_pagelist);
                  pool_update_curpage(pp);
          }
  
          pp->pr_nget++;
          pr_leave(pp);
  
          /*
           * If we have a low water mark and we are now below that low
           * water mark, add more items to the pool.
           */
          if (POOL_NEEDS_CATCHUP(pp) && pool_catchup(pp) != 0) {
                  /*
                   * XXX: Should we log a warning?  Should we set up a timeout
                   * to try again in a second or so?  The latter could break
                   * a caller's assumptions about interrupt protection, etc.
                   */
          }
  
          simple_unlock(&pp->pr_slock);
          return (v);
  }
  
  /*
   * Internal version of pool_put().  Pool is already locked/entered.
   */
  static void
  pool_do_put(struct pool *pp, void *v, struct pool_pagelist *pq)
  {
          struct pool_item *pi = v;
          struct pool_item_header *ph;
  
          LOCK_ASSERT(simple_lock_held(&pp->pr_slock));
          SCHED_ASSERT_UNLOCKED();
  
  #ifdef DIAGNOSTIC
          if (__predict_false(pp->pr_nout == 0)) {
                  printf("pool %s: putting with none out\n",
                      pp->pr_wchan);
                  panic("pool_put");
          }
  #endif
  
          if (__predict_false((ph = pr_find_pagehead(pp, v)) == NULL)) {
                  pr_printlog(pp, NULL, printf);
                  panic("pool_put: %s: page header missing", pp->pr_wchan);
          }
  
  #ifdef LOCKDEBUG
          /*
           * Check if we're freeing a locked simple lock.
           */
          simple_lock_freecheck((caddr_t)pi, ((caddr_t)pi) + pp->pr_size);
  #endif
  
          /*
           * Return to item list.
           */
          if (pp->pr_roflags & PR_NOTOUCH) {
                  pr_item_notouch_put(pp, ph, v);
          } else {
  #ifdef DIAGNOSTIC
                  pi->pi_magic = PI_MAGIC;
  #endif
  #ifdef DEBUG
                  {
                          int i, *ip = v;
  
                          for (i = 0; i < pp->pr_size / sizeof(int); i++) {
                                  *ip++ = PI_MAGIC;
                          }
                  }
  #endif
  
                  LIST_INSERT_HEAD(&ph->ph_itemlist, pi, pi_list);
          }
          KDASSERT(ph->ph_nmissing != 0);
          ph->ph_nmissing--;
          pp->pr_nput++;
          pp->pr_nitems++;
          pp->pr_nout--;
  
          /* Cancel "pool empty" condition if it exists */
          if (pp->pr_curpage == NULL)
                  pp->pr_curpage = ph;
  
          if (pp->pr_flags & PR_WANTED) {
                  pp->pr_flags &= ~PR_WANTED;
                  if (ph->ph_nmissing == 0)
                          pp->pr_nidle++;
                  wakeup((caddr_t)pp);
                  return;
          }
  
          /*
           * If this page is now empty, do one of two things:
           *
           *      (1) If we have more pages than the page high water mark,
           *          free the page back to the system.  ONLY CONSIDER
           *          FREEING BACK A PAGE IF WE HAVE MORE THAN OUR MINIMUM PAGE
           *          CLAIM.
           *
           *      (2) Otherwise, move the page to the empty page list.
           *
           * Either way, select a new current page (so we use a partially-full
           * page if one is available).
           */
          if (ph->ph_nmissing == 0) {
                  pp->pr_nidle++;
                  if (pp->pr_npages > pp->pr_minpages &&
                      (pp->pr_npages > pp->pr_maxpages ||
                       pa_starved_p(pp->pr_alloc))) {
                          pr_rmpage(pp, ph, pq);
                  } else {
                          LIST_REMOVE(ph, ph_pagelist);
                          LIST_INSERT_HEAD(&pp->pr_emptypages, ph, ph_pagelist);
  
                          /*
                           * Update the timestamp on the page.  A page must
                           * be idle for some period of time before it can
                           * be reclaimed by the pagedaemon.  This minimizes
                           * ping-pong'ing for memory.
                           */
                          getmicrotime(&ph->ph_time);
                  }
                  pool_update_curpage(pp);
          }
  
          /*
           * If the page was previously completely full, move it to the
           * partially-full list and make it the current page.  The next
           * allocation will get the item from this page, instead of
           * further fragmenting the pool.
           */
          else if (ph->ph_nmissing == (pp->pr_itemsperpage - 1)) {
                  LIST_REMOVE(ph, ph_pagelist);
                  LIST_INSERT_HEAD(&pp->pr_partpages, ph, ph_pagelist);
                  pp->pr_curpage = ph;
          }
  }
  
  /*
   * Return resource to the pool; must be called at appropriate spl level
   */
  #ifdef POOL_DIAGNOSTIC
  void
  _pool_put(struct pool *pp, void *v, const char *file, long line)
  {
          struct pool_pagelist pq;
  
          LIST_INIT(&pq);
  
          simple_lock(&pp->pr_slock);
          pr_enter(pp, file, line);
  
          pr_log(pp, v, PRLOG_PUT, file, line);
  
          pool_do_put(pp, v, &pq);
  
          pr_leave(pp);
          simple_unlock(&pp->pr_slock);
  
          pr_pagelist_free(pp, &pq);
  }
  #undef pool_put
  #endif /* POOL_DIAGNOSTIC */
  
  void
  pool_put(struct pool *pp, void *v)
  {
          struct pool_pagelist pq;
  
          LIST_INIT(&pq);
  
          simple_lock(&pp->pr_slock);
          pool_do_put(pp, v, &pq);
          simple_unlock(&pp->pr_slock);
  
          pr_pagelist_free(pp, &pq);
  }
  
  #ifdef POOL_DIAGNOSTIC
  #define         pool_put(h, v)  _pool_put((h), (v), __FILE__, __LINE__)
  #endif
  
  /*
   * pool_grow: grow a pool by a page.
   *
   * => called with pool locked.
   * => unlock and relock the pool.
   * => return with pool locked.
   */
  
  static int
  pool_grow(struct pool *pp, int flags)
  {
          struct pool_item_header *ph = NULL;
          char *cp;
  
          simple_unlock(&pp->pr_slock);
          cp = pool_allocator_alloc(pp, flags);
          if (__predict_true(cp != NULL)) {
                  ph = pool_alloc_item_header(pp, cp, flags);
          }
          if (__predict_false(cp == NULL || ph == NULL)) {
                  if (cp != NULL) {
                          pool_allocator_free(pp, cp);
                  }
                  simple_lock(&pp->pr_slock);
                  return ENOMEM;
          }
  
          simple_lock(&pp->pr_slock);
          pool_prime_page(pp, cp, ph);
          pp->pr_npagealloc++;
          return 0;
  }
  
  /*
   * Add N items to the pool.
   */
  int
  pool_prime(struct pool *pp, int n)
  {
          int newpages;
          int error = 0;
  
          simple_lock(&pp->pr_slock);
  
          newpages = roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;
  
          while (newpages-- > 0) {
                  error = pool_grow(pp, PR_NOWAIT);
                  if (error) {
                          break;
                  }
                  pp->pr_minpages++;
          }
  
          if (pp->pr_minpages >= pp->pr_maxpages)
                  pp->pr_maxpages = pp->pr_minpages + 1;  /* XXX */
  
          simple_unlock(&pp->pr_slock);
          return error;
  }
  
  /*
   * Add a page worth of items to the pool.
   *
   * Note, we must be called with the pool descriptor LOCKED.
   */
  static void
  pool_prime_page(struct pool *pp, caddr_t storage, struct pool_item_header *ph)
  {
          struct pool_item *pi;
          caddr_t cp = storage;
          unsigned int align = pp->pr_align;
          unsigned int ioff = pp->pr_itemoffset;
          int n;
  
          LOCK_ASSERT(simple_lock_held(&pp->pr_slock));
  
  #ifdef DIAGNOSTIC
          if ((pp->pr_roflags & PR_NOALIGN) == 0 &&
              ((uintptr_t)cp & (pp->pr_alloc->pa_pagesz - 1)) != 0)
                  panic("pool_prime_page: %s: unaligned page", pp->pr_wchan);
  #endif
  
          /*
           * Insert page header.
           */
          LIST_INSERT_HEAD(&pp->pr_emptypages, ph, ph_pagelist);
          LIST_INIT(&ph->ph_itemlist);
          ph->ph_page = storage;
          ph->ph_nmissing = 0;
          getmicrotime(&ph->ph_time);
          if ((pp->pr_roflags & PR_PHINPAGE) == 0)
                  SPLAY_INSERT(phtree, &pp->pr_phtree, ph);
  
          pp->pr_nidle++;
  
          /*
           * Color this page.
           */
          cp = (caddr_t)(cp + pp->pr_curcolor);
          if ((pp->pr_curcolor += align) > pp->pr_maxcolor)
                  pp->pr_curcolor = 0;
  
          /*
           * Adjust storage to apply aligment to `pr_itemoffset' in each item.
           */
          if (ioff != 0)
                  cp = (caddr_t)(cp + (align - ioff));
  
          /*
           * Insert remaining chunks on the bucket list.
           */
          n = pp->pr_itemsperpage;
          pp->pr_nitems += n;
  
          if (pp->pr_roflags & PR_NOTOUCH) {
                  pool_item_freelist_t *freelist = PR_FREELIST(ph);
                  int i;
  
                  ph->ph_off = cp - storage;
                  ph->ph_firstfree = 0;
                  for (i = 0; i < n - 1; i++)
                          freelist[i] = i + 1;
                  freelist[n - 1] = PR_INDEX_EOL;
          } else {
                  while (n--) {
                          pi = (struct pool_item *)cp;
  
                          KASSERT(((((vaddr_t)pi) + ioff) & (align - 1)) == 0);
  
                          /* Insert on page list */
                          LIST_INSERT_HEAD(&ph->ph_itemlist, pi, pi_list);
  #ifdef DIAGNOSTIC
                          pi->pi_magic = PI_MAGIC;
  #endif
                          cp = (caddr_t)(cp + pp->pr_size);
                  }
          }
  
          /*
           * If the pool was depleted, point at the new page.
           */
          if (pp->pr_curpage == NULL)
                  pp->pr_curpage = ph;
  
          if (++pp->pr_npages > pp->pr_hiwat)
                  pp->pr_hiwat = pp->pr_npages;
  }
  
  /*
   * Used by pool_get() when nitems drops below the low water mark.  This
   * is used to catch up pr_nitems with the low water mark.
   *
   * Note 1, we never wait for memory here, we let the caller decide what to do.
   *
   * Note 2, we must be called with the pool already locked, and we return
   * with it locked.
   */
  static int
  pool_catchup(struct pool *pp)
  {
          int error = 0;
  
          while (POOL_NEEDS_CATCHUP(pp)) {
                  error = pool_grow(pp, PR_NOWAIT);
                  if (error) {
                          break;
                  }
          }
          return error;
  }
  
  static void
  pool_update_curpage(struct pool *pp)
  {
  
          pp->pr_curpage = LIST_FIRST(&pp->pr_partpages);
          if (pp->pr_curpage == NULL) {
                  pp->pr_curpage = LIST_FIRST(&pp->pr_emptypages);
          }
  }
  
  void
  pool_setlowat(struct pool *pp, int n)
  {
  
          simple_lock(&pp->pr_slock);
  
          pp->pr_minitems = n;
          pp->pr_minpages = (n == 0)
                  ? 0
                  : roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;
  
          /* Make sure we're caught up with the newly-set low water mark. */
          if (POOL_NEEDS_CATCHUP(pp) && pool_catchup(pp) != 0) {
                  /*
                   * XXX: Should we log a warning?  Should we set up a timeout
                   * to try again in a second or so?  The latter could break
                   * a caller's assumptions about interrupt protection, etc.
                   */
          }
  
          simple_unlock(&pp->pr_slock);
  }
  
  void
  pool_sethiwat(struct pool *pp, int n)
  {
  
          simple_lock(&pp->pr_slock);
  
          pp->pr_maxpages = (n == 0)
                  ? 0
                  : roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;
  
          simple_unlock(&pp->pr_slock);
  }
  
  void
  pool_sethardlimit(struct pool *pp, int n, const char *warnmess, int ratecap)
  {
  
          simple_lock(&pp->pr_slock);
  
          pp->pr_hardlimit = n;
          pp->pr_hardlimit_warning = warnmess;
          pp->pr_hardlimit_ratecap.tv_sec = ratecap;
          pp->pr_hardlimit_warning_last.tv_sec = 0;
          pp->pr_hardlimit_warning_last.tv_usec = 0;
  
          /*
           * In-line version of pool_sethiwat(), because we don't want to
           * release the lock.
           */
          pp->pr_maxpages = (n == 0)
                  ? 0
                  : roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;
  
          simple_unlock(&pp->pr_slock);
  }
  
  /*
   * Release all complete pages that have not been used recently.
   */
  int
  #ifdef POOL_DIAGNOSTIC
  _pool_reclaim(struct pool *pp, const char *file, long line)
  #else
  pool_reclaim(struct pool *pp)
  #endif
  {
          struct pool_item_header *ph, *phnext;
          struct pool_cache *pc;
          struct pool_pagelist pq;
          struct pool_cache_grouplist pcgl;
          struct timeval curtime, diff;
  
          if (pp->pr_drain_hook != NULL) {
                  /*
                   * The drain hook must be called with the pool unlocked.
                   */
                  (*pp->pr_drain_hook)(pp->pr_drain_hook_arg, PR_NOWAIT);
          }
  
          if (simple_lock_try(&pp->pr_slock) == 0)
                  return (0);
          pr_enter(pp, file, line);
  
          LIST_INIT(&pq);
          LIST_INIT(&pcgl);
  
          /*
           * Reclaim items from the pool's caches.
           */
          LIST_FOREACH(pc, &pp->pr_cachelist, pc_poollist)
                  pool_cache_reclaim(pc, &pq, &pcgl);
  
          getmicrotime(&curtime);
  
          for (ph = LIST_FIRST(&pp->pr_emptypages); ph != NULL; ph = phnext) {
                  phnext = LIST_NEXT(ph, ph_pagelist);
  
                  /* Check our minimum page claim */
                  if (pp->pr_npages <= pp->pr_minpages)
                          break;
  
                  KASSERT(ph->ph_nmissing == 0);
                  timersub(&curtime, &ph->ph_time, &diff);
                  if (diff.tv_sec < pool_inactive_time
                      && !pa_starved_p(pp->pr_alloc))
                          continue;
  
                  /*
                   * If freeing this page would put us below
                   * the low water mark, stop now.
                   */
                  if ((pp->pr_nitems - pp->pr_itemsperpage) <
                      pp->pr_minitems)
                          break;
  
                  pr_rmpage(pp, ph, &pq);
          }
  
          pr_leave(pp);
          simple_unlock(&pp->pr_slock);
          if (LIST_EMPTY(&pq) && LIST_EMPTY(&pcgl))
                  return 0;
  
          pr_pagelist_free(pp, &pq);
          pcg_grouplist_free(&pcgl);
          return (1);
  }
  
  /*
   * Drain pools, one at a time.
   *
   * Note, we must never be called from an interrupt context.
   */
  void
  pool_drain(void *arg)
  {
          struct pool *pp;
          int s;
  
          pp = NULL;
          s = splvm();
          simple_lock(&pool_head_slock);
          if (drainpp == NULL) {
                  drainpp = LIST_FIRST(&pool_head);
          }
          if (drainpp) {
                  pp = drainpp;
                  drainpp = LIST_NEXT(pp, pr_poollist);
          }
          simple_unlock(&pool_head_slock);
          if (pp)
                  pool_reclaim(pp);
          splx(s);
  }
  
  /*
   * Diagnostic helpers.
   */
  void
  pool_print(struct pool *pp, const char *modif)
  {
          int s;
  
          s = splvm();
          if (simple_lock_try(&pp->pr_slock) == 0) {
                  printf("pool %s is locked; try again later\n",
                      pp->pr_wchan);
                  splx(s);
                  return;
          }
          pool_print1(pp, modif, printf);
          simple_unlock(&pp->pr_slock);
          splx(s);
  }
  
  void
  pool_printall(const char *modif, void (*pr)(const char *, ...))
  {
          struct pool *pp;
  
          if (simple_lock_try(&pool_head_slock) == 0) {
                  (*pr)("WARNING: pool_head_slock is locked\n");
          } else {
                  simple_unlock(&pool_head_slock);
          }
  
          LIST_FOREACH(pp, &pool_head, pr_poollist) {
                  pool_printit(pp, modif, pr);
          }
  }
  
  void
  pool_printit(struct pool *pp, const char *modif, void (*pr)(const char *, ...))
  {
  
          if (pp == NULL) {
                  (*pr)("Must specify a pool to print.\n");
                  return;
          }
  
          /*
           * Called from DDB; interrupts should be blocked, and all
           * other processors should be paused.  We can skip locking
           * the pool in this case.
           *
           * We do a simple_lock_try() just to print the lock
           * status, however.
           */
  
          if (simple_lock_try(&pp->pr_slock) == 0)
                  (*pr)("WARNING: pool %s is locked\n", pp->pr_wchan);
          else
                  simple_unlock(&pp->pr_slock);
  
          pool_print1(pp, modif, pr);
  }
  
  static void
  pool_print_pagelist(struct pool *pp, struct pool_pagelist *pl,
      void (*pr)(const char *, ...))
  {
          struct pool_item_header *ph;
  #ifdef DIAGNOSTIC
          struct pool_item *pi;
  #endif
  
          LIST_FOREACH(ph, pl, ph_pagelist) {
                  (*pr)("\t\tpage %p, nmissing %d, time %lu,%lu\n",
                      ph->ph_page, ph->ph_nmissing,
                      (u_long)ph->ph_time.tv_sec,
                      (u_long)ph->ph_time.tv_usec);
  #ifdef DIAGNOSTIC
                  if (!(pp->pr_roflags & PR_NOTOUCH)) {
                          LIST_FOREACH(pi, &ph->ph_itemlist, pi_list) {
                                  if (pi->pi_magic != PI_MAGIC) {
                                          (*pr)("\t\t\titem %p, magic 0x%x\n",
                                              pi, pi->pi_magic);
                                  }
                          }
                  }
  #endif
          }
  }
  
  static void
  pool_print1(struct pool *pp, const char *modif, void (*pr)(const char *, ...))
  {
          struct pool_item_header *ph;
          struct pool_cache *pc;
          struct pool_cache_group *pcg;
          int i, print_log = 0, print_pagelist = 0, print_cache = 0;
          char c;
  
          while ((c = *modif++) != '\0') {
                  if (c == 'l')
                          print_log = 1;
                  if (c == 'p')
                          print_pagelist = 1;
                  if (c == 'c')
                          print_cache = 1;
          }
  
          (*pr)("POOL %s: size %u, align %u, ioff %u, roflags 0x%08x\n",
              pp->pr_wchan, pp->pr_size, pp->pr_align, pp->pr_itemoffset,
              pp->pr_roflags);
          (*pr)("\talloc %p\n", pp->pr_alloc);
          (*pr)("\tminitems %u, minpages %u, maxpages %u, npages %u\n",
              pp->pr_minitems, pp->pr_minpages, pp->pr_maxpages, pp->pr_npages);
          (*pr)("\titemsperpage %u, nitems %u, nout %u, hardlimit %u\n",
              pp->pr_itemsperpage, pp->pr_nitems, pp->pr_nout, pp->pr_hardlimit);
  
          (*pr)("\n\tnget %lu, nfail %lu, nput %lu\n",
              pp->pr_nget, pp->pr_nfail, pp->pr_nput);
          (*pr)("\tnpagealloc %lu, npagefree %lu, hiwat %u, nidle %lu\n",
              pp->pr_npagealloc, pp->pr_npagefree, pp->pr_hiwat, pp->pr_nidle);
  
          if (print_pagelist == 0)
                  goto skip_pagelist;
  
          if ((ph = LIST_FIRST(&pp->pr_emptypages)) != NULL)
                  (*pr)("\n\tempty page list:\n");
          pool_print_pagelist(pp, &pp->pr_emptypages, pr);
          if ((ph = LIST_FIRST(&pp->pr_fullpages)) != NULL)
                  (*pr)("\n\tfull page list:\n");
          pool_print_pagelist(pp, &pp->pr_fullpages, pr);
          if ((ph = LIST_FIRST(&pp->pr_partpages)) != NULL)
                  (*pr)("\n\tpartial-page list:\n");
          pool_print_pagelist(pp, &pp->pr_partpages, pr);
  
          if (pp->pr_curpage == NULL)
                  (*pr)("\tno current page\n");
          else
                  (*pr)("\tcurpage %p\n", pp->pr_curpage->ph_page);
  
   skip_pagelist:
          if (print_log == 0)
                  goto skip_log;
  
          (*pr)("\n");
          if ((pp->pr_roflags & PR_LOGGING) == 0)
                  (*pr)("\tno log\n");
          else {
                  pr_printlog(pp, NULL, pr);
          }
  
   skip_log:
          if (print_cache == 0)
                  goto skip_cache;
  
  #define PR_GROUPLIST(pcg)                                               \
          (*pr)("\t\tgroup %p: avail %d\n", pcg, pcg->pcg_avail);         \
          for (i = 0; i < PCG_NOBJECTS; i++) {                            \
                  if (pcg->pcg_objects[i].pcgo_pa !=                      \
                      POOL_PADDR_INVALID) {                               \
                          (*pr)("\t\t\t%p, 0x%llx\n",                     \
                              pcg->pcg_objects[i].pcgo_va,                \
                              (unsigned long long)                        \
                              pcg->pcg_objects[i].pcgo_pa);               \
                  } else {                                                \
                          (*pr)("\t\t\t%p\n",                             \
                              pcg->pcg_objects[i].pcgo_va);               \
                  }                                                       \
          }
  
          LIST_FOREACH(pc, &pp->pr_cachelist, pc_poollist) {
                  (*pr)("\tcache %p\n", pc);
                  (*pr)("\t    hits %lu misses %lu ngroups %lu nitems %lu\n",
                      pc->pc_hits, pc->pc_misses, pc->pc_ngroups, pc->pc_nitems);
                  (*pr)("\t    full groups:\n");
                  LIST_FOREACH(pcg, &pc->pc_fullgroups, pcg_list) {
                          PR_GROUPLIST(pcg);
                  }
                  (*pr)("\t    partial groups:\n");
                  LIST_FOREACH(pcg, &pc->pc_partgroups, pcg_list) {
                          PR_GROUPLIST(pcg);
                  }
                  (*pr)("\t    empty groups:\n");
                  LIST_FOREACH(pcg, &pc->pc_emptygroups, pcg_list) {
                          PR_GROUPLIST(pcg);
                  }
          }
  #undef PR_GROUPLIST
  
   skip_cache:
          pr_enter_check(pp, pr);
  }
  
  static int
  pool_chk_page(struct pool *pp, const char *label, struct pool_item_header *ph)
  {
          struct pool_item *pi;
          caddr_t page;
          int n;
  
          if ((pp->pr_roflags & PR_NOALIGN) == 0) {
                  page = (caddr_t)((uintptr_t)ph & pp->pr_alloc->pa_pagemask);
                  if (page != ph->ph_page &&
                      (pp->pr_roflags & PR_PHINPAGE) != 0) {
                          if (label != NULL)
                                  printf("%s: ", label);
                          printf("pool(%p:%s): page inconsistency: page %p;"
                                 " at page head addr %p (p %p)\n", pp,
                                  pp->pr_wchan, ph->ph_page,
                                  ph, page);
                          return 1;
                  }
          }
  
          if ((pp->pr_roflags & PR_NOTOUCH) != 0)
                  return 0;
  
          for (pi = LIST_FIRST(&ph->ph_itemlist), n = 0;
               pi != NULL;
               pi = LIST_NEXT(pi,pi_list), n++) {
  
  #ifdef DIAGNOSTIC
                  if (pi->pi_magic != PI_MAGIC) {
                          if (label != NULL)
                                  printf("%s: ", label);
                          printf("pool(%s): free list modified: magic=%x;"
                                 " page %p; item ordinal %d; addr %p\n",
                                  pp->pr_wchan, pi->pi_magic, ph->ph_page,
                                  n, pi);
                          panic("pool");
                  }
  #endif
                  if ((pp->pr_roflags & PR_NOALIGN) != 0) {
                          continue;
                  }
                  page = (caddr_t)((uintptr_t)pi & pp->pr_alloc->pa_pagemask);
                  if (page == ph->ph_page)
                          continue;
  
                  if (label != NULL)
                          printf("%s: ", label);
                  printf("pool(%p:%s): page inconsistency: page %p;"
                         " item ordinal %d; addr %p (p %p)\n", pp,
                          pp->pr_wchan, ph->ph_page,
                          n, pi, page);
                  return 1;
          }
          return 0;
  }
  
  
  int
  pool_chk(struct pool *pp, const char *label)
  {
          struct pool_item_header *ph;
          int r = 0;
  
          simple_lock(&pp->pr_slock);
          LIST_FOREACH(ph, &pp->pr_emptypages, ph_pagelist) {
                  r = pool_chk_page(pp, label, ph);
                  if (r) {
                          goto out;
                  }
          }
          LIST_FOREACH(ph, &pp->pr_fullpages, ph_pagelist) {
                  r = pool_chk_page(pp, label, ph);
                  if (r) {
                          goto out;
                  }
          }
          LIST_FOREACH(ph, &pp->pr_partpages, ph_pagelist) {
                  r = pool_chk_page(pp, label, ph);
                  if (r) {
                          goto out;
                  }
          }
  
  out:
          simple_unlock(&pp->pr_slock);
          return (r);
  }
  
  /*
   * pool_cache_init:
   *
   *      Initialize a pool cache.
   *
   *      NOTE: If the pool must be protected from interrupts, we expect
   *      to be called at the appropriate interrupt priority level.
   */
  void
  pool_cache_init(struct pool_cache *pc, struct pool *pp,
      int (*ctor)(void *, void *, int),
      void (*dtor)(void *, void *),
      void *arg)
  {
  
          LIST_INIT(&pc->pc_emptygroups);
          LIST_INIT(&pc->pc_fullgroups);
          LIST_INIT(&pc->pc_partgroups);
          simple_lock_init(&pc->pc_slock);
  
          pc->pc_pool = pp;
  
          pc->pc_ctor = ctor;
          pc->pc_dtor = dtor;
          pc->pc_arg  = arg;
  
          pc->pc_hits   = 0;
          pc->pc_misses = 0;
  
          pc->pc_ngroups = 0;
  
          pc->pc_nitems = 0;
  
          simple_lock(&pp->pr_slock);
          LIST_INSERT_HEAD(&pp->pr_cachelist, pc, pc_poollist);
          simple_unlock(&pp->pr_slock);
  }
  
  /*
   * pool_cache_destroy:
   *
   *      Destroy a pool cache.
   */
  void
  pool_cache_destroy(struct pool_cache *pc)
  {
          struct pool *pp = pc->pc_pool;
  
          /* First, invalidate the entire cache. */
          pool_cache_invalidate(pc);
  
          /* ...and remove it from the pool's cache list. */
          simple_lock(&pp->pr_slock);
          LIST_REMOVE(pc, pc_poollist);
          simple_unlock(&pp->pr_slock);
  }
  
  static inline void *
  pcg_get(struct pool_cache_group *pcg, paddr_t *pap)
  {
          void *object;
          u_int idx;
  
          KASSERT(pcg->pcg_avail <= PCG_NOBJECTS);
          KASSERT(pcg->pcg_avail != 0);
          idx = --pcg->pcg_avail;
  
          KASSERT(pcg->pcg_objects[idx].pcgo_va != NULL);
          object = pcg->pcg_objects[idx].pcgo_va;
          if (pap != NULL)
                  *pap = pcg->pcg_objects[idx].pcgo_pa;
          pcg->pcg_objects[idx].pcgo_va = NULL;
  
          return (object);
  }
  
  static inline void
  pcg_put(struct pool_cache_group *pcg, void *object, paddr_t pa)
  {
          u_int idx;
  
          KASSERT(pcg->pcg_avail < PCG_NOBJECTS);
          idx = pcg->pcg_avail++;
  
          KASSERT(pcg->pcg_objects[idx].pcgo_va == NULL);
          pcg->pcg_objects[idx].pcgo_va = object;
          pcg->pcg_objects[idx].pcgo_pa = pa;
  }
  
  static void
  pcg_grouplist_free(struct pool_cache_grouplist *pcgl)
  {
          struct pool_cache_group *pcg;
          int s;
  
          s = splvm();
          while ((pcg = LIST_FIRST(pcgl)) != NULL) {
                  LIST_REMOVE(pcg, pcg_list);
                  pool_put(&pcgpool, pcg);
          }
          splx(s);
  }
  
  /*
   * pool_cache_get{,_paddr}:
   *
   *      Get an object from a pool cache (optionally returning
   *      the physical address of the object).
   */
  void *
  pool_cache_get_paddr(struct pool_cache *pc, int flags, paddr_t *pap)
  {
          struct pool_cache_group *pcg;
          void *object;
  
  #ifdef LOCKDEBUG
          if (flags & PR_WAITOK)
                  ASSERT_SLEEPABLE(NULL, "pool_cache_get(PR_WAITOK)");
  #endif
  
          simple_lock(&pc->pc_slock);
  
          pcg = LIST_FIRST(&pc->pc_partgroups);
          if (pcg == NULL) {
                  pcg = LIST_FIRST(&pc->pc_fullgroups);
                  if (pcg != NULL) {
                          LIST_REMOVE(pcg, pcg_list);
                          LIST_INSERT_HEAD(&pc->pc_partgroups, pcg, pcg_list);
                  }
          }
          if (pcg == NULL) {
  
                  /*
                   * No groups with any available objects.  Allocate
                   * a new object, construct it, and return it to
                   * the caller.  We will allocate a group, if necessary,
                   * when the object is freed back to the cache.
                   */
                  pc->pc_misses++;
                  simple_unlock(&pc->pc_slock);
                  object = pool_get(pc->pc_pool, flags);
                  if (object != NULL && pc->pc_ctor != NULL) {
                          if ((*pc->pc_ctor)(pc->pc_arg, object, flags) != 0) {
                                  pool_put(pc->pc_pool, object);
                                  return (NULL);
                          }
                  }
                  if (object != NULL && pap != NULL) {
  #ifdef POOL_VTOPHYS
                          *pap = POOL_VTOPHYS(object);
  #else
                          *pap = POOL_PADDR_INVALID;
  #endif
                  }
                  return (object);
          }
  
          pc->pc_hits++;
          pc->pc_nitems--;
          object = pcg_get(pcg, pap);
  
          if (pcg->pcg_avail == 0) {
                  LIST_REMOVE(pcg, pcg_list);
                  LIST_INSERT_HEAD(&pc->pc_emptygroups, pcg, pcg_list);
          }
          simple_unlock(&pc->pc_slock);
  
          return (object);
  }
  
  /*
   * pool_cache_put{,_paddr}:
   *
   *      Put an object back to the pool cache (optionally caching the
   *      physical address of the object).
   */
  void
  pool_cache_put_paddr(struct pool_cache *pc, void *object, paddr_t pa)
  {
          struct pool_cache_group *pcg;
          int s;
  
          if (__predict_false((pc->pc_pool->pr_flags & PR_WANTED) != 0)) {
                  goto destruct;
          }
  
          simple_lock(&pc->pc_slock);
  
          pcg = LIST_FIRST(&pc->pc_partgroups);
          if (pcg == NULL) {
                  pcg = LIST_FIRST(&pc->pc_emptygroups);
                  if (pcg != NULL) {
                          LIST_REMOVE(pcg, pcg_list);
                          LIST_INSERT_HEAD(&pc->pc_partgroups, pcg, pcg_list);
                  }
          }
          if (pcg == NULL) {
  
                  /*
                   * No empty groups to free the object to.  Attempt to
                   * allocate one.
                   */
                  simple_unlock(&pc->pc_slock);
                  s = splvm();
                  pcg = pool_get(&pcgpool, PR_NOWAIT);
                  splx(s);
                  if (pcg == NULL) {
  destruct:
  
                          /*
                           * Unable to allocate a cache group; destruct the object
                           * and free it back to the pool.
                           */
                          pool_cache_destruct_object(pc, object);
                          return;
                  }
                  memset(pcg, 0, sizeof(*pcg));
                  simple_lock(&pc->pc_slock);
                  pc->pc_ngroups++;
                  LIST_INSERT_HEAD(&pc->pc_partgroups, pcg, pcg_list);
          }
  
          pc->pc_nitems++;
          pcg_put(pcg, object, pa);
  
          if (pcg->pcg_avail == PCG_NOBJECTS) {
                  LIST_REMOVE(pcg, pcg_list);
                  LIST_INSERT_HEAD(&pc->pc_fullgroups, pcg, pcg_list);
          }
          simple_unlock(&pc->pc_slock);
  }
  
  /*
   * pool_cache_destruct_object:
   *
   *      Force destruction of an object and its release back into
   *      the pool.
   */
  void
  pool_cache_destruct_object(struct pool_cache *pc, void *object)
  {
  
          if (pc->pc_dtor != NULL)
                  (*pc->pc_dtor)(pc->pc_arg, object);
          pool_put(pc->pc_pool, object);
  }
  
  static void
  pool_do_cache_invalidate_grouplist(struct pool_cache_grouplist *pcgsl,
      struct pool_cache *pc, struct pool_pagelist *pq,
      struct pool_cache_grouplist *pcgdl)
  {
          struct pool_cache_group *pcg, *npcg;
          void *object;
  
          for (pcg = LIST_FIRST(pcgsl); pcg != NULL; pcg = npcg) {
                  npcg = LIST_NEXT(pcg, pcg_list);
                  while (pcg->pcg_avail != 0) {
                          pc->pc_nitems--;
                          object = pcg_get(pcg, NULL);
                          if (pc->pc_dtor != NULL)
                                  (*pc->pc_dtor)(pc->pc_arg, object);
                          pool_do_put(pc->pc_pool, object, pq);
                  }
                  pc->pc_ngroups--;
                  LIST_REMOVE(pcg, pcg_list);
                  LIST_INSERT_HEAD(pcgdl, pcg, pcg_list);
          }
  }
  
  static void
  pool_do_cache_invalidate(struct pool_cache *pc, struct pool_pagelist *pq,
      struct pool_cache_grouplist *pcgl)
  {
  
          LOCK_ASSERT(simple_lock_held(&pc->pc_slock));
          LOCK_ASSERT(simple_lock_held(&pc->pc_pool->pr_slock));
  
          pool_do_cache_invalidate_grouplist(&pc->pc_fullgroups, pc, pq, pcgl);
          pool_do_cache_invalidate_grouplist(&pc->pc_partgroups, pc, pq, pcgl);
  
          KASSERT(LIST_EMPTY(&pc->pc_partgroups));
          KASSERT(LIST_EMPTY(&pc->pc_fullgroups));
          KASSERT(pc->pc_nitems == 0);
  }
  
  /*
   * pool_cache_invalidate:
   *
   *      Invalidate a pool cache (destruct and release all of the
   *      cached objects).
   */
  void
  pool_cache_invalidate(struct pool_cache *pc)
  {
          struct pool_pagelist pq;
          struct pool_cache_grouplist pcgl;
  
          LIST_INIT(&pq);
          LIST_INIT(&pcgl);
  
          simple_lock(&pc->pc_slock);
          simple_lock(&pc->pc_pool->pr_slock);
  
          pool_do_cache_invalidate(pc, &pq, &pcgl);
  
          simple_unlock(&pc->pc_pool->pr_slock);
          simple_unlock(&pc->pc_slock);
  
          pr_pagelist_free(pc->pc_pool, &pq);
          pcg_grouplist_free(&pcgl);
  }
  
  /*
   * pool_cache_reclaim:
   *
   *      Reclaim a pool cache for pool_reclaim().
   */
  static void
  pool_cache_reclaim(struct pool_cache *pc, struct pool_pagelist *pq,
      struct pool_cache_grouplist *pcgl)
  {
  
          /*
           * We're locking in the wrong order (normally pool_cache -> pool,
           * but the pool is already locked when we get here), so we have
           * to use trylock.  If we can't lock the pool_cache, it's not really
           * a big deal here.
           */
          if (simple_lock_try(&pc->pc_slock) == 0)
                  return;
  
          pool_do_cache_invalidate(pc, pq, pcgl);
  
          simple_unlock(&pc->pc_slock);
  }
  
  /*
   * Pool backend allocators.
   *
   * Each pool has a backend allocator that handles allocation, deallocation,
   * and any additional draining that might be needed.
   *
   * We provide two standard allocators:
   *
   *      pool_allocator_kmem - the default when no allocator is specified
   *
   *      pool_allocator_nointr - used for pools that will not be accessed
   *      in interrupt context.
   */
  void    *pool_page_alloc(struct pool *, int);
  void    pool_page_free(struct pool *, void *);
  
  #ifdef POOL_SUBPAGE
  struct pool_allocator pool_allocator_kmem_fullpage = {
          pool_page_alloc, pool_page_free, 0,
          .pa_backingmapptr = &kmem_map,
  };
  #else
  struct pool_allocator pool_allocator_kmem = {
          pool_page_alloc, pool_page_free, 0,
          .pa_backingmapptr = &kmem_map,
  };
  #endif
  
  void    *pool_page_alloc_nointr(struct pool *, int);
  void    pool_page_free_nointr(struct pool *, void *);
  
  #ifdef POOL_SUBPAGE
  struct pool_allocator pool_allocator_nointr_fullpage = {
          pool_page_alloc_nointr, pool_page_free_nointr, 0,
          .pa_backingmapptr = &kernel_map,
  };
  #else
  struct pool_allocator pool_allocator_nointr = {
          pool_page_alloc_nointr, pool_page_free_nointr, 0,
          .pa_backingmapptr = &kernel_map,
  };
  #endif
  
  #ifdef POOL_SUBPAGE
  void    *pool_subpage_alloc(struct pool *, int);
  void    pool_subpage_free(struct pool *, void *);
  
  struct pool_allocator pool_allocator_kmem = {
          pool_subpage_alloc, pool_subpage_free, POOL_SUBPAGE,
          .pa_backingmapptr = &kmem_map,
  };
  
  void    *pool_subpage_alloc_nointr(struct pool *, int);
  void    pool_subpage_free_nointr(struct pool *, void *);
  
  struct pool_allocator pool_allocator_nointr = {
          pool_subpage_alloc, pool_subpage_free, POOL_SUBPAGE,
          .pa_backingmapptr = &kmem_map,
  };
  #endif /* POOL_SUBPAGE */
  
  static void *
  pool_allocator_alloc(struct pool *pp, int flags)
  {
          struct pool_allocator *pa = pp->pr_alloc;
          void *res;
  
          LOCK_ASSERT(!simple_lock_held(&pp->pr_slock));
  
          res = (*pa->pa_alloc)(pp, flags);
          if (res == NULL && (flags & PR_WAITOK) == 0) {
                  /*
                   * We only run the drain hook here if PR_NOWAIT.
                   * In other cases, the hook will be run in
                   * pool_reclaim().
                   */
                  if (pp->pr_drain_hook != NULL) {
                          (*pp->pr_drain_hook)(pp->pr_drain_hook_arg, flags);
                          res = (*pa->pa_alloc)(pp, flags);
                  }
          }
          return res;
  }
  
  static void
  pool_allocator_free(struct pool *pp, void *v)
  {
          struct pool_allocator *pa = pp->pr_alloc;
  
          LOCK_ASSERT(!simple_lock_held(&pp->pr_slock));
  
          (*pa->pa_free)(pp, v);
  }
  
  void *
  pool_page_alloc(struct pool *pp, int flags)
  {
          boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;
  
          return ((void *) uvm_km_alloc_poolpage_cache(kmem_map, waitok));
  }
  
  void
  pool_page_free(struct pool *pp, void *v)
  {
  
          uvm_km_free_poolpage_cache(kmem_map, (vaddr_t) v);
  }
  
  static void *
  pool_page_alloc_meta(struct pool *pp, int flags)
  {
          boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;
  
          return ((void *) uvm_km_alloc_poolpage(kmem_map, waitok));
  }
  
  static void
  pool_page_free_meta(struct pool *pp, void *v)
  {
  
          uvm_km_free_poolpage(kmem_map, (vaddr_t) v);
  }
  
  #ifdef POOL_SUBPAGE
  /* Sub-page allocator, for machines with large hardware pages. */
  void *
  pool_subpage_alloc(struct pool *pp, int flags)
  {
          void *v;
          int s;
          s = splvm();
          v = pool_get(&psppool, flags);
          splx(s);
          return v;
  }
  
  void
  pool_subpage_free(struct pool *pp, void *v)
  {
          int s;
          s = splvm();
          pool_put(&psppool, v);
          splx(s);
  }
  
  /* We don't provide a real nointr allocator.  Maybe later. */
  void *
  pool_subpage_alloc_nointr(struct pool *pp, int flags)
  {
  
          return (pool_subpage_alloc(pp, flags));
  }
  
  void
  pool_subpage_free_nointr(struct pool *pp, void *v)
  {
  
          pool_subpage_free(pp, v);
  }
  #endif /* POOL_SUBPAGE */
  void *
  pool_page_alloc_nointr(struct pool *pp, int flags)
  {
          boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;
  
          return ((void *) uvm_km_alloc_poolpage_cache(kernel_map, waitok));
  }
  
  void
  pool_page_free_nointr(struct pool *pp, void *v)
  {
  
          uvm_km_free_poolpage_cache(kernel_map, (vaddr_t) v);
  }

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