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

     /*
      * Copyright (c) 1991 Regents of the University of California.
      * All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
      * 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 University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
     *
     *      from: @(#)vm_page.c     7.4 (Berkeley) 5/7/91
     * $FreeBSD: src/sys/vm/vm_page.c,v 1.69.2.8 1999/09/05 08:24:34 peter Exp $
     */
    
    /*
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Authors: Avadis Tevanian, Jr., Michael Wayne Young
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     */
    
    /*
     *      Resident memory management module.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    #include <sys/proc.h>
    #include <sys/vmmeter.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_prot.h>
    #include <vm/lock.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_map.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_extern.h>
    
    static void     vm_page_queue_init __P((void));
    static vm_page_t vm_page_select_free __P((vm_object_t object,
                            vm_pindex_t pindex, int prefqueue));
    
    /*
     *      Associated with page of user-allocatable memory is a
     *      page structure.
     */
    
    static struct pglist *vm_page_buckets;  /* Array of buckets */
    static int vm_page_bucket_count;        /* How big is array? */
    static int vm_page_hash_mask;           /* Mask for hash function */
   
   struct pglist vm_page_queue_free[PQ_L2_SIZE] = {0};
   struct pglist vm_page_queue_zero[PQ_L2_SIZE] = {0};
   struct pglist vm_page_queue_active = {0};
   struct pglist vm_page_queue_inactive = {0};
   struct pglist vm_page_queue_cache[PQ_L2_SIZE] = {0};
   
   int no_queue=0;
   
   struct vpgqueues vm_page_queues[PQ_COUNT] = {0};
   int pqcnt[PQ_COUNT] = {0};
   
   static void
   vm_page_queue_init(void) {
           int i;
   
           vm_page_queues[PQ_NONE].pl = NULL;
           vm_page_queues[PQ_NONE].cnt = &no_queue;
           for(i=0;i<PQ_L2_SIZE;i++) {
                   vm_page_queues[PQ_FREE+i].pl = &vm_page_queue_free[i];
                   vm_page_queues[PQ_FREE+i].cnt = &cnt.v_free_count;
           }
           for(i=0;i<PQ_L2_SIZE;i++) {
                   vm_page_queues[PQ_ZERO+i].pl = &vm_page_queue_zero[i];
                   vm_page_queues[PQ_ZERO+i].cnt = &cnt.v_free_count;
           }
           vm_page_queues[PQ_INACTIVE].pl = &vm_page_queue_inactive;
           vm_page_queues[PQ_INACTIVE].cnt = &cnt.v_inactive_count;
   
           vm_page_queues[PQ_ACTIVE].pl = &vm_page_queue_active;
           vm_page_queues[PQ_ACTIVE].cnt = &cnt.v_active_count;
           for(i=0;i<PQ_L2_SIZE;i++) {
                   vm_page_queues[PQ_CACHE+i].pl = &vm_page_queue_cache[i];
                   vm_page_queues[PQ_CACHE+i].cnt = &cnt.v_cache_count;
           }
           for(i=0;i<PQ_COUNT;i++) {
                   if (vm_page_queues[i].pl) {
                           TAILQ_INIT(vm_page_queues[i].pl);
                   } else if (i != 0) {
                           panic("vm_page_queue_init: queue %d is null", i);
                   }
                   vm_page_queues[i].lcnt = &pqcnt[i];
           }
   }
   
   vm_page_t vm_page_array = 0;
   int vm_page_array_size = 0;
   long first_page = 0;
   static long last_page;
   static vm_size_t page_mask;
   static int page_shift;
   int vm_page_zero_count = 0;
   
   /*
    * map of contiguous valid DEV_BSIZE chunks in a page
    * (this list is valid for page sizes upto 16*DEV_BSIZE)
    */
   static u_short vm_page_dev_bsize_chunks[] = {
           0x0, 0x1, 0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f, 0xff,
           0x1ff, 0x3ff, 0x7ff, 0xfff, 0x1fff, 0x3fff, 0x7fff, 0xffff
   };
   
   static __inline int vm_page_hash __P((vm_object_t object, vm_pindex_t pindex));
   static int vm_page_freechk_and_unqueue __P((vm_page_t m));
   static void vm_page_free_wakeup __P((void));
   
   /*
    *      vm_set_page_size:
    *
    *      Sets the page size, perhaps based upon the memory
    *      size.  Must be called before any use of page-size
    *      dependent functions.
    *
    *      Sets page_shift and page_mask from cnt.v_page_size.
    */
   void
   vm_set_page_size()
   {
   
           if (cnt.v_page_size == 0)
                   cnt.v_page_size = DEFAULT_PAGE_SIZE;
           page_mask = cnt.v_page_size - 1;
           if ((page_mask & cnt.v_page_size) != 0)
                   panic("vm_set_page_size: page size not a power of two");
           for (page_shift = 0;; page_shift++)
                   if ((1 << page_shift) == cnt.v_page_size)
                           break;
   }
   
   /*
    *      vm_page_startup:
    *
    *      Initializes the resident memory module.
    *
    *      Allocates memory for the page cells, and
    *      for the object/offset-to-page hash table headers.
    *      Each page cell is initialized and placed on the free list.
    */
   
   vm_offset_t
   vm_page_startup(starta, enda, vaddr)
           register vm_offset_t starta;
           vm_offset_t enda;
           register vm_offset_t vaddr;
   {
           register vm_offset_t mapped;
           register vm_page_t m;
           register struct pglist *bucket;
           vm_size_t npages, page_range;
           register vm_offset_t new_start;
           int i;
           vm_offset_t pa;
           int nblocks;
           vm_offset_t first_managed_page;
   
           /* the biggest memory array is the second group of pages */
           vm_offset_t start;
           vm_offset_t biggestone, biggestsize;
   
           vm_offset_t total;
   
           total = 0;
           biggestsize = 0;
           biggestone = 0;
           nblocks = 0;
           vaddr = round_page(vaddr);
   
           for (i = 0; phys_avail[i + 1]; i += 2) {
                   phys_avail[i] = round_page(phys_avail[i]);
                   phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
           }
   
           for (i = 0; phys_avail[i + 1]; i += 2) {
                   int size = phys_avail[i + 1] - phys_avail[i];
   
                   if (size > biggestsize) {
                           biggestone = i;
                           biggestsize = size;
                   }
                   ++nblocks;
                   total += size;
           }
   
           start = phys_avail[biggestone];
   
           /*
            * Initialize the queue headers for the free queue, the active queue
            * and the inactive queue.
            */
   
           vm_page_queue_init();
   
           /*
            * Allocate (and initialize) the hash table buckets.
            *
            * The number of buckets MUST BE a power of 2, and the actual value is
            * the next power of 2 greater than the number of physical pages in
            * the system.
            *
            * Note: This computation can be tweaked if desired.
            */
           vm_page_buckets = (struct pglist *) vaddr;
           bucket = vm_page_buckets;
           if (vm_page_bucket_count == 0) {
                   vm_page_bucket_count = 1;
                   while (vm_page_bucket_count < atop(total))
                           vm_page_bucket_count <<= 1;
           }
           vm_page_hash_mask = vm_page_bucket_count - 1;
   
           /*
            * Validate these addresses.
            */
   
           new_start = start + vm_page_bucket_count * sizeof(struct pglist);
           new_start = round_page(new_start);
           mapped = vaddr;
           vaddr = pmap_map(mapped, start, new_start,
               VM_PROT_READ | VM_PROT_WRITE);
           start = new_start;
           bzero((caddr_t) mapped, vaddr - mapped);
           mapped = vaddr;
   
           for (i = 0; i < vm_page_bucket_count; i++) {
                   TAILQ_INIT(bucket);
                   bucket++;
           }
   
           /*
            * round (or truncate) the addresses to our page size.
            */
   
           /*
            * Pre-allocate maps and map entries that cannot be dynamically
            * allocated via malloc().  The maps include the kernel_map and
            * kmem_map which must be initialized before malloc() will work
            * (obviously).  Also could include pager maps which would be
            * allocated before kmeminit.
            *
            * Allow some kernel map entries... this should be plenty since people
            * shouldn't be cluttering up the kernel map (they should use their
            * own maps).
            */
   
           kentry_data_size = MAX_KMAP * sizeof(struct vm_map) +
               MAX_KMAPENT * sizeof(struct vm_map_entry);
           kentry_data_size = round_page(kentry_data_size);
           kentry_data = (vm_offset_t) vaddr;
           vaddr += kentry_data_size;
   
           /*
            * Validate these zone addresses.
            */
   
           new_start = start + (vaddr - mapped);
           pmap_map(mapped, start, new_start, VM_PROT_READ | VM_PROT_WRITE);
           bzero((caddr_t) mapped, (vaddr - mapped));
           start = round_page(new_start);
   
           /*
            * Compute the number of pages of memory that will be available for
            * use (taking into account the overhead of a page structure per
            * page).
            */
   
           first_page = phys_avail[0] / PAGE_SIZE;
           last_page = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE;
   
           page_range = last_page - (phys_avail[0] / PAGE_SIZE);
           npages = (total - (page_range * sizeof(struct vm_page)) -
               (start - phys_avail[biggestone])) / PAGE_SIZE;
   
           /*
            * Initialize the mem entry structures now, and put them in the free
            * queue.
            */
   
           vm_page_array = (vm_page_t) vaddr;
           mapped = vaddr;
   
           /*
            * Validate these addresses.
            */
   
           new_start = round_page(start + page_range * sizeof(struct vm_page));
           mapped = pmap_map(mapped, start, new_start,
               VM_PROT_READ | VM_PROT_WRITE);
           start = new_start;
   
           first_managed_page = start / PAGE_SIZE;
   
           /*
            * Clear all of the page structures
            */
           bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
           vm_page_array_size = page_range;
   
           cnt.v_page_count = 0;
           cnt.v_free_count = 0;
           for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
                   if (i == biggestone)
                           pa = ptoa(first_managed_page);
                   else
                           pa = phys_avail[i];
                   while (pa < phys_avail[i + 1] && npages-- > 0) {
                           ++cnt.v_page_count;
                           ++cnt.v_free_count;
                           m = PHYS_TO_VM_PAGE(pa);
                           m->phys_addr = pa;
                           m->flags = 0;
                           m->pc = (pa >> PAGE_SHIFT) & PQ_L2_MASK;
                           m->queue = PQ_FREE + m->pc;
                           TAILQ_INSERT_TAIL(vm_page_queues[m->queue].pl, m, pageq);
                           ++(*vm_page_queues[m->queue].lcnt);
                           pa += PAGE_SIZE;
                   }
           }
   
           return (mapped);
   }
   
   /*
    *      vm_page_hash:
    *
    *      Distributes the object/offset key pair among hash buckets.
    *
    *      NOTE:  This macro depends on vm_page_bucket_count being a power of 2.
    */
   static __inline int
   vm_page_hash(object, pindex)
           vm_object_t object;
           vm_pindex_t pindex;
   {
           return ((((unsigned) object) >> 5) + (pindex >> 1)) & vm_page_hash_mask;
   }
   
   /*
    *      vm_page_insert:         [ internal use only ]
    *
    *      Inserts the given mem entry into the object/object-page
    *      table and object list.
    *
    *      The object and page must be locked, and must be splhigh.
    */
   
   void
   vm_page_insert(m, object, pindex)
           register vm_page_t m;
           register vm_object_t object;
           register vm_pindex_t pindex;
   {
           register struct pglist *bucket;
   
           if (m->flags & PG_TABLED)
                   panic("vm_page_insert: already inserted");
   
           /*
            * Record the object/offset pair in this page
            */
   
           m->object = object;
           m->pindex = pindex;
   
           /*
            * Insert it into the object_object/offset hash table
            */
   
           bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
           TAILQ_INSERT_TAIL(bucket, m, hashq);
   
           /*
            * Now link into the object's list of backed pages.
            */
   
           TAILQ_INSERT_TAIL(&object->memq, m, listq);
           m->flags |= PG_TABLED;
           m->object->page_hint = m;
   
           /*
            * And show that the object has one more resident page.
            */
   
           object->resident_page_count++;
   }
   
   /*
    *      vm_page_remove:         [ internal use only ]
    *                              NOTE: used by device pager as well -wfj
    *
    *      Removes the given mem entry from the object/offset-page
    *      table and the object page list.
    *
    *      The object and page must be locked, and at splhigh.
    */
   
   void
   vm_page_remove(m)
           register vm_page_t m;
   {
           register struct pglist *bucket;
   
           if (!(m->flags & PG_TABLED))
                   return;
   
           if (m->object->page_hint == m)
                   m->object->page_hint = NULL;
   
           /*
            * Remove from the object_object/offset hash table
            */
   
           bucket = &vm_page_buckets[vm_page_hash(m->object, m->pindex)];
           TAILQ_REMOVE(bucket, m, hashq);
   
           /*
            * Now remove from the object's list of backed pages.
            */
   
           TAILQ_REMOVE(&m->object->memq, m, listq);
   
           /*
            * And show that the object has one fewer resident page.
            */
   
           m->object->resident_page_count--;
   
           m->flags &= ~PG_TABLED;
   }
   
   /*
    *      vm_page_lookup:
    *
    *      Returns the page associated with the object/offset
    *      pair specified; if none is found, NULL is returned.
    *
    *      The object must be locked.  No side effects.
    */
   
   vm_page_t
   vm_page_lookup(object, pindex)
           register vm_object_t object;
           register vm_pindex_t pindex;
   {
           register vm_page_t m;
           register struct pglist *bucket;
           int s;
   
           /*
            * Search the hash table for this object/offset pair
            */
   
           bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
   
           s = splvm();
           for (m = TAILQ_FIRST(bucket); m != NULL; m = TAILQ_NEXT(m,hashq)) {
                   if ((m->object == object) && (m->pindex == pindex)) {
                           splx(s);
                           m->object->page_hint = m;
                           return (m);
                   }
           }
           splx(s);
           return (NULL);
   }
   
   /*
    *      vm_page_rename:
    *
    *      Move the given memory entry from its
    *      current object to the specified target object/offset.
    *
    *      The object must be locked.
    */
   void
   vm_page_rename(m, new_object, new_pindex)
           register vm_page_t m;
           register vm_object_t new_object;
           vm_pindex_t new_pindex;
   {
           int s;
   
           s = splvm();
           vm_page_remove(m);
           vm_page_insert(m, new_object, new_pindex);
           splx(s);
   }
   
   /*
    * vm_page_unqueue without any wakeup
    */
   void
   vm_page_unqueue_nowakeup(m)
           vm_page_t m;
   {
           int queue = m->queue;
           struct vpgqueues *pq;
           if (queue != PQ_NONE) {
                   pq = &vm_page_queues[queue];
                   m->queue = PQ_NONE;
                   TAILQ_REMOVE(pq->pl, m, pageq);
                   --(*pq->cnt);
                   --(*pq->lcnt);
           }
   }
   
   /*
    * vm_page_unqueue must be called at splhigh();
    */
   void
   vm_page_unqueue(m)
           vm_page_t m;
   {
           int queue = m->queue;
           struct vpgqueues *pq;
           if (queue != PQ_NONE) {
                   m->queue = PQ_NONE;
                   pq = &vm_page_queues[queue];
                   TAILQ_REMOVE(pq->pl, m, pageq);
                   --(*pq->cnt);
                   --(*pq->lcnt);
                   if ((queue - m->pc) == PQ_CACHE) {
                           if ((cnt.v_cache_count + cnt.v_free_count) <
                                   (cnt.v_free_reserved + cnt.v_cache_min))
                                   pagedaemon_wakeup();
                   }
           }
   }
   
   /*
    * Find a page on the specified queue with color optimization.
    */
   vm_page_t
   vm_page_list_find(basequeue, index)
           int basequeue, index;
   {
   #if PQ_L2_SIZE > 1
   
           int i,j;
           vm_page_t m;
           int hindex;
   
           for(j = 0; j < PQ_L1_SIZE; j++) {
                   for(i = (PQ_L2_SIZE/2) - (PQ_L1_SIZE - 1);
                           (i+j) >= 0;
                           i -= PQ_L1_SIZE) {
                           hindex = (index + (i+j)) & PQ_L2_MASK;
                           m = TAILQ_FIRST(vm_page_queues[basequeue + hindex].pl);
                           if (m)
                                   return m;
   
                           hindex = (index - (i+j)) & PQ_L2_MASK;
                           m = TAILQ_FIRST(vm_page_queues[basequeue + hindex].pl);
                           if (m)
                                   return m;
                   }
           }
           return NULL;
   #else
           return TAILQ_FIRST(vm_page_queues[basequeue].pl);
   #endif
   
   }
   
   /*
    * Find a page on the specified queue with color optimization.
    */
   vm_page_t
   vm_page_select(object, pindex, basequeue)
           vm_object_t object;
           vm_pindex_t pindex;
           int basequeue;
   {
   
   #if PQ_L2_SIZE > 1
           int index;
           index = (pindex + object->pg_color) & PQ_L2_MASK;
           return vm_page_list_find(basequeue, index);
   
   #else
           return TAILQ_FIRST(vm_page_queues[basequeue].pl);
   #endif
   
   }
   
   /*
    * Find a free or zero page, with specified preference.
    */
   static vm_page_t
   vm_page_select_free(object, pindex, prefqueue)
           vm_object_t object;
           vm_pindex_t pindex;
           int prefqueue;
   {
   #if PQ_L2_SIZE > 1
           int i,j;
           int index, hindex;
   #endif
           vm_page_t m;
           int oqueuediff;
   
           if (prefqueue == PQ_ZERO)
                   oqueuediff = PQ_FREE - PQ_ZERO;
           else
                   oqueuediff = PQ_ZERO - PQ_FREE;
   
           if (object->page_hint) {
                    if (object->page_hint->pindex == (pindex - 1)) {
                           vm_offset_t last_phys;
                           if ((object->page_hint->flags & PG_FICTITIOUS) == 0) {
                                   if ((object->page_hint < &vm_page_array[cnt.v_page_count-1]) &&
                                           (object->page_hint >= &vm_page_array[0])) {
                                           int queue;
                                           last_phys = VM_PAGE_TO_PHYS(object->page_hint);
                                           m = PHYS_TO_VM_PAGE(last_phys + PAGE_SIZE);
                                           queue = m->queue - m->pc;
                                           if (queue == PQ_FREE || queue == PQ_ZERO) {
                                                   return m;
                                           }
                                   }
                           }
                   }
           }
                           
   
   #if PQ_L2_SIZE > 1
   
           index = pindex + object->pg_color;
           for(j = 0; j < PQ_L1_SIZE; j++) {
                   for(i = (PQ_L2_SIZE/2) - (PQ_L1_SIZE - 1);
                           (i + j) >= 0;
                           i -= PQ_L1_SIZE) {
   
                           hindex = prefqueue + ((index + (i+j)) & PQ_L2_MASK);
                           if (m = TAILQ_FIRST(vm_page_queues[hindex].pl)) 
                                   return m;
                           if (m = TAILQ_FIRST(vm_page_queues[hindex + oqueuediff].pl))
                                   return m;
   
                           hindex = prefqueue + ((index - (i+j)) & PQ_L2_MASK);
                           if (m = TAILQ_FIRST(vm_page_queues[hindex].pl)) 
                                   return m;
                           if (m = TAILQ_FIRST(vm_page_queues[hindex + oqueuediff].pl))
                                   return m;
                   }
           }
   #else
           if (m = TAILQ_FIRST(vm_page_queues[prefqueue].pl))
                   return m;
           else
                   return TAILQ_FIRST(vm_page_queues[prefqueue + oqueuediff].pl);
   #endif
   
           return NULL;
   }
   
   /*
    *      vm_page_alloc:
    *
    *      Allocate and return a memory cell associated
    *      with this VM object/offset pair.
    *
    *      page_req classes:
    *      VM_ALLOC_NORMAL         normal process request
    *      VM_ALLOC_SYSTEM         system *really* needs a page
    *      VM_ALLOC_INTERRUPT      interrupt time request
    *      VM_ALLOC_ZERO           zero page
    *
    *      Object must be locked.
    */
   vm_page_t
   vm_page_alloc(object, pindex, page_req)
           vm_object_t object;
           vm_pindex_t pindex;
           int page_req;
   {
           register vm_page_t m;
           struct vpgqueues *pq;
           int queue, qtype;
           int s;
   
   #ifdef DIAGNOSTIC
           m = vm_page_lookup(object, pindex);
           if (m)
                   panic("vm_page_alloc: page already allocated");
   #endif
   
           if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
                   page_req = VM_ALLOC_SYSTEM;
           };
   
           s = splvm();
   
           switch (page_req) {
   
           case VM_ALLOC_NORMAL:
                   if (cnt.v_free_count >= cnt.v_free_reserved) {
                           m = vm_page_select_free(object, pindex, PQ_FREE);
   #if defined(DIAGNOSTIC)
                           if (m == NULL)
                                   panic("vm_page_alloc(NORMAL): missing page on free queue\n");
   #endif
                   } else {
                           m = vm_page_select(object, pindex, PQ_CACHE);
                           if (m == NULL) {
                                   splx(s);
   #if defined(DIAGNOSTIC)
                                   if (cnt.v_cache_count > 0)
                                           printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
   #endif
                                   pagedaemon_wakeup();
                                   return (NULL);
                           }
                   }
                   break;
   
           case VM_ALLOC_ZERO:
                   if (cnt.v_free_count >= cnt.v_free_reserved) {
                           m = vm_page_select_free(object, pindex, PQ_ZERO);
   #if defined(DIAGNOSTIC)
                           if (m == NULL)
                                   panic("vm_page_alloc(ZERO): missing page on free queue\n");
   #endif
                   } else {
                           m = vm_page_select(object, pindex, PQ_CACHE);
                           if (m == NULL) {
                                   splx(s);
   #if defined(DIAGNOSTIC)
                                   if (cnt.v_cache_count > 0)
                                           printf("vm_page_alloc(ZERO): missing pages on cache queue: %d\n", cnt.v_cache_count);
   #endif
                                   pagedaemon_wakeup();
                                   return (NULL);
                           }
                   }
                   break;
   
           case VM_ALLOC_SYSTEM:
                   if ((cnt.v_free_count >= cnt.v_free_reserved) ||
                       ((cnt.v_cache_count == 0) &&
                       (cnt.v_free_count >= cnt.v_interrupt_free_min))) {
                           m = vm_page_select_free(object, pindex, PQ_FREE);
   #if defined(DIAGNOSTIC)
                           if (m == NULL)
                                   panic("vm_page_alloc(SYSTEM): missing page on free queue\n");
   #endif
                   } else {
                           m = vm_page_select(object, pindex, PQ_CACHE);
                           if (m == NULL) {
                                   splx(s);
   #if defined(DIAGNOSTIC)
                                   if (cnt.v_cache_count > 0)
                                           printf("vm_page_alloc(SYSTEM): missing pages on cache queue: %d\n", cnt.v_cache_count);
   #endif
                                   pagedaemon_wakeup();
                                   return (NULL);
                           }
                   }
                   break;
   
           case VM_ALLOC_INTERRUPT:
                   if (cnt.v_free_count > 0) {
                           m = vm_page_select_free(object, pindex, PQ_FREE);
   #if defined(DIAGNOSTIC)
                           if (m == NULL)
                                   panic("vm_page_alloc(INTERRUPT): missing page on free queue\n");
   #endif
                   } else {
                           splx(s);
                           pagedaemon_wakeup();
                           return (NULL);
                   }
                   break;
   
           default:
                   panic("vm_page_alloc: invalid allocation class");
           }
   
           queue = m->queue;
           qtype = queue - m->pc;
           if (qtype == PQ_ZERO)
                   --vm_page_zero_count;
           pq = &vm_page_queues[queue];
           TAILQ_REMOVE(pq->pl, m, pageq);
           --(*pq->cnt);
           --(*pq->lcnt);
           if (qtype == PQ_ZERO) {
                   m->flags = PG_ZERO|PG_BUSY;
           } else if (qtype == PQ_CACHE) {
                   vm_page_remove(m);
                   m->flags = PG_BUSY;
           } else {
                   m->flags = PG_BUSY;
           }
           m->wire_count = 0;
           m->hold_count = 0;
           m->act_count = 0;
           m->busy = 0;
           m->valid = 0;
           m->dirty = 0;
           m->queue = PQ_NONE;
   
           /* XXX before splx until vm_page_insert is safe */
           vm_page_insert(m, object, pindex);
   
           splx(s);
   
           /*
            * Don't wakeup too often - wakeup the pageout daemon when
            * we would be nearly out of memory.
            */
           if (((cnt.v_free_count + cnt.v_cache_count) <
                   (cnt.v_free_reserved + cnt.v_cache_min)) ||
                           (cnt.v_free_count < cnt.v_pageout_free_min))
                   pagedaemon_wakeup();
   
           return (m);
   }
   
   void
   vm_wait()
   {
           int s;
   
           s = splvm();
           if (curproc == pageproc) {
                   vm_pageout_pages_needed = 1;
                   tsleep(&vm_pageout_pages_needed, PSWP, "vmwait", 0);
           } else {
                   if (!vm_pages_needed) {
                           vm_pages_needed++;
                           wakeup(&vm_pages_needed);
                   }
                   tsleep(&cnt.v_free_count, PVM, "vmwait", 0);
           }
           splx(s);
   }
   
   
   /*
    *      vm_page_activate:
    *
    *      Put the specified page on the active list (if appropriate).
    *
    *      The page queues must be locked.
    */
   void
   vm_page_activate(m)
           register vm_page_t m;
   {
           int s;
   
           s = splvm();
           if (m->queue == PQ_ACTIVE)
                   panic("vm_page_activate: already active");
   
           if ((m->queue - m->pc) == PQ_CACHE)
                   cnt.v_reactivated++;
   
           vm_page_unqueue(m);
   
           if (m->wire_count == 0) {
                   m->queue = PQ_ACTIVE;
                   ++(*vm_page_queues[PQ_ACTIVE].lcnt);
                   TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                   if (m->act_count < ACT_INIT)
                           m->act_count = ACT_INIT;
                   cnt.v_active_count++;
           }
           splx(s);
   }
   
   /*
    * helper routine for vm_page_free and vm_page_free_zero
    */
   static int
   vm_page_freechk_and_unqueue(m)
           vm_page_t m;
   {
           if (m->busy ||
                   (m->flags & PG_BUSY) ||
                   ((m->queue - m->pc) == PQ_FREE) ||
                   (m->hold_count != 0)) {
                   printf("vm_page_free: pindex(%ld), busy(%d), PG_BUSY(%d), hold(%d)\n",
                           m->pindex, m->busy,
                           (m->flags & PG_BUSY) ? 1 : 0, m->hold_count);
                   if ((m->queue - m->pc) == PQ_FREE)
                           panic("vm_page_free: freeing free page");
                   else
                           panic("vm_page_free: freeing busy page");
           }
   
           vm_page_remove(m);
           vm_page_unqueue_nowakeup(m);
           if ((m->flags & PG_FICTITIOUS) != 0) {
                   return 0;
           }
           if (m->wire_count != 0) {
                   if (m->wire_count > 1) {
                           panic("vm_page_free: invalid wire count (%d), pindex: 0x%x",
                                   m->wire_count, m->pindex);
                   }
                   m->wire_count = 0;
                   cnt.v_wire_count--;
           }
   
           return 1;
   }
   
   /*
    * helper routine for vm_page_free and vm_page_free_zero
    */
   static __inline void
   vm_page_free_wakeup()
   {
           
   /*
    * if pageout daemon needs pages, then tell it that there are
    * some free.
    */
           if (vm_pageout_pages_needed) {
                   wakeup(&vm_pageout_pages_needed);
                   vm_pageout_pages_needed = 0;
           }
           /*
            * wakeup processes that are waiting on memory if we hit a
            * high water mark. And wakeup scheduler process if we have
            * lots of memory. this process will swapin processes.
            */
           if (vm_pages_needed &&
                   ((cnt.v_free_count + cnt.v_cache_count) >= cnt.v_free_min)) {
                   wakeup(&cnt.v_free_count);
                   vm_pages_needed = 0;
           }
   }
   
   /*
    *      vm_page_free:
    *
    *      Returns the given page to the free list,
    *      disassociating it with any VM object.
   *
   *      Object and page must be locked prior to entry.
   */
  void
  vm_page_free(m)
          register vm_page_t m;
  {
          int s;
          struct vpgqueues *pq;
  
          s = splvm();
  
          cnt.v_tfree++;
  
          if (!vm_page_freechk_and_unqueue(m)) {
                  splx(s);
                  return;
          }
  
          m->queue = PQ_FREE + m->pc;
          pq = &vm_page_queues[m->queue];
          ++(*pq->lcnt);
          ++(*pq->cnt);
          /*
           * If the pageout process is grabbing the page, it is likely
           * that the page is NOT in the cache.  It is more likely that
           * the page will be partially in the cache if it is being
           * explicitly freed.
           */
          if (curproc == pageproc) {
                  TAILQ_INSERT_TAIL(pq->pl, m, pageq);
          } else {
                  TAILQ_INSERT_HEAD(pq->pl, m, pageq);
          }
          vm_page_free_wakeup();
          splx(s);
  }
  
  void
  vm_page_free_zero(m)
          register vm_page_t m;
  {
          int s;
          struct vpgqueues *pq;
  
          s = splvm();
  
          cnt.v_tfree++;
  
          if (!vm_page_freechk_and_unqueue(m)) {
                  splx(s);
                  return;
          }
  
          m->queue = PQ_ZERO + m->pc;
          pq = &vm_page_queues[m->queue];
          ++(*pq->lcnt);
          ++(*pq->cnt);
  
          TAILQ_INSERT_HEAD(pq->pl, m, pageq);
          ++vm_page_zero_count;
          vm_page_free_wakeup();
          splx(s);
  }
  
  /*
   *      vm_page_wire:
   *
   *      Mark this page as wired down by yet
   *      another map, removing it from paging queues
   *      as necessary.
   *
   *      The page queues must be locked.
   */
  void
  vm_page_wire(m)
          register vm_page_t m;
  {
          int s;
  
          s = splvm();
          if (m->wire_count == 0) {
                  vm_page_unqueue(m);
                  cnt.v_wire_count++;
          }
          m->wire_count++;
          splx(s);
          ++(*vm_page_queues[PQ_NONE].lcnt);
          m->flags |= PG_MAPPED;
  }
  
  /*
   *      vm_page_unwire:
   *
   *      Release one wiring of this page, potentially
   *      enabling it to be paged again.
   *
   *      The page queues must be locked.
   */
  void
  vm_page_unwire(m)
          register vm_page_t m;
  {
          int s;
  
          s = splvm();
  
          if (m->wire_count > 0)
                  m->wire_count--;
                  
          if (m->wire_count == 0) {
                  cnt.v_wire_count--;
                  TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                  m->queue = PQ_ACTIVE;
                  ++(*vm_page_queues[PQ_ACTIVE].lcnt);
                  cnt.v_active_count++;
          }
          splx(s);
  }
  
  
  /*
   *      vm_page_deactivate:
   *
   *      Returns the given page to the inactive list,
   *      indicating that no physical maps have access
   *      to this page.  [Used by the physical mapping system.]
   *
   *      The page queues must be locked.
   */
  void
  vm_page_deactivate(m)
          register vm_page_t m;
  {
          int s;
  
          /*
           * Only move active pages -- ignore locked or already inactive ones.
           *
           * XXX: sometimes we get pages which aren't wired down or on any queue -
           * we need to put them on the inactive queue also, otherwise we lose
           * track of them. Paul Mackerras (paulus@cs.anu.edu.au) 9-Jan-93.
           */
          if (m->queue == PQ_INACTIVE)
                  return;
  
          s = splvm();
          if (m->wire_count == 0 && m->hold_count == 0) {
                  if ((m->queue - m->pc) == PQ_CACHE)
                          cnt.v_reactivated++;
                  vm_page_unqueue(m);
                  TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                  m->queue = PQ_INACTIVE;
                  ++(*vm_page_queues[PQ_INACTIVE].lcnt);
                  cnt.v_inactive_count++;
          }
          splx(s);
  }
  
  /*
   * vm_page_cache
   *
   * Put the specified page onto the page cache queue (if appropriate).
   */
  void
  vm_page_cache(m)
          register vm_page_t m;
  {
          int s;
  
          if ((m->flags & PG_BUSY) || m->busy || m->wire_count) {
                  printf("vm_page_cache: attempting to cache busy page\n");
                  return;
          }
          if ((m->queue - m->pc) == PQ_CACHE)
                  return;
  
          vm_page_protect(m, VM_PROT_NONE);
          if (m->dirty != 0) {
                  panic("vm_page_cache: caching a dirty page, pindex: %d", m->pindex);
          }
          s = splvm();
          vm_page_unqueue_nowakeup(m);
          m->queue = PQ_CACHE + m->pc;
          ++(*vm_page_queues[m->queue].lcnt);
          TAILQ_INSERT_TAIL(vm_page_queues[m->queue].pl, m, pageq);
          cnt.v_cache_count++;
          vm_page_free_wakeup();
          splx(s);
  }
  
  
  /*
   * mapping function for valid bits or for dirty bits in
   * a page
   */
  __inline int
  vm_page_bits(int base, int size)
  {
          u_short chunk;
  
          if ((base == 0) && (size >= PAGE_SIZE))
                  return VM_PAGE_BITS_ALL;
          size = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
          base = (base % PAGE_SIZE) / DEV_BSIZE;
          chunk = vm_page_dev_bsize_chunks[size / DEV_BSIZE];
          return (chunk << base) & VM_PAGE_BITS_ALL;
  }
  
  /*
   * set a page valid and clean
   */
  void
  vm_page_set_validclean(m, base, size)
          vm_page_t m;
          int base;
          int size;
  {
          int pagebits = vm_page_bits(base, size);
          m->valid |= pagebits;
          m->dirty &= ~pagebits;
          if( base == 0 && size == PAGE_SIZE)
                  pmap_clear_modify(VM_PAGE_TO_PHYS(m));
  }
  
  /*
   * set a page (partially) invalid
   */
  void
  vm_page_set_invalid(m, base, size)
          vm_page_t m;
          int base;
          int size;
  {
          int bits;
  
          m->valid &= ~(bits = vm_page_bits(base, size));
          if (m->valid == 0)
                  m->dirty &= ~bits;
  }
  
  /*
   * is (partial) page valid?
   */
  int
  vm_page_is_valid(m, base, size)
          vm_page_t m;
          int base;
          int size;
  {
          int bits = vm_page_bits(base, size);
  
          if (m->valid && ((m->valid & bits) == bits))
                  return 1;
          else
                  return 0;
  }
  
  void
  vm_page_test_dirty(m)
          vm_page_t m;
  {
          if ((m->dirty != VM_PAGE_BITS_ALL) &&
              pmap_is_modified(VM_PAGE_TO_PHYS(m))) {
                  m->dirty = VM_PAGE_BITS_ALL;
          }
  }
  
  /*
   * This interface is for merging with malloc() someday.
   * Even if we never implement compaction so that contiguous allocation
   * works after initialization time, malloc()'s data structures are good
   * for statistics and for allocations of less than a page.
   */
  void *
  contigmalloc(size, type, flags, low, high, alignment, boundary)
          unsigned long size;     /* should be size_t here and for malloc() */
          int type;
          int flags;
          unsigned long low;
          unsigned long high;
          unsigned long alignment;
          unsigned long boundary;
  {
          int i, s, start;
          vm_offset_t addr, phys, tmp_addr;
          int pass;
          vm_page_t pga = vm_page_array;
  
          size = round_page(size);
          if (size == 0)
                  panic("vm_page_alloc_contig: size must not be 0");
          if ((alignment & (alignment - 1)) != 0)
                  panic("vm_page_alloc_contig: alignment must be a power of 2");
          if ((boundary & (boundary - 1)) != 0)
                  panic("vm_page_alloc_contig: boundary must be a power of 2");
  
          start = 0;
          for (pass = 0; pass <= 1; pass++) {
                  s = splvm();
  again:
                  /*
                   * Find first page in array that is free, within range, aligned, and
                   * such that the boundary won't be crossed.
                   */
                  for (i = start; i < cnt.v_page_count; i++) {
                          int pqtype;
                          phys = VM_PAGE_TO_PHYS(&pga[i]);
                          pqtype = pga[i].queue - pga[i].pc;
                          if (((pqtype == PQ_ZERO) || (pqtype == PQ_FREE) || (pqtype == PQ_CACHE)) &&
                              (phys >= low) && (phys < high) &&
                              ((phys & (alignment - 1)) == 0) &&
                              (((phys ^ (phys + size - 1)) & ~(boundary - 1)) == 0))
                                  break;
                  }
  
                  /*
                   * If the above failed or we will exceed the upper bound, fail.
                   */
                  if ((i == cnt.v_page_count) ||
                          ((VM_PAGE_TO_PHYS(&pga[i]) + size) > high)) {
                          vm_page_t m, next;
  
  again1:
                          for (m = TAILQ_FIRST(&vm_page_queue_inactive);
                                  m != NULL;
                                  m = next) {
  
                                  if (m->queue != PQ_INACTIVE) {
                                          break;
                                  }
  
                                  next = TAILQ_NEXT(m, pageq);
                                  if (m->flags & PG_BUSY) {
                                          m->flags |= PG_WANTED;
                                          tsleep(m, PVM, "vpctw0", 0);
                                          goto again1;
                                  }
                                  vm_page_test_dirty(m);
                                  if (m->dirty) {
                                          if (m->object->type == OBJT_VNODE) {
                                                  vm_object_page_clean(m->object, 0, 0, TRUE, TRUE);
                                                  goto again1;
                                          } else if (m->object->type == OBJT_SWAP ||
                                                                  m->object->type == OBJT_DEFAULT) {
                                                  vm_page_protect(m, VM_PROT_NONE);
                                                  vm_pageout_flush(&m, 1, 0);
                                                  goto again1;
                                          }
                                  }
                                  if ((m->dirty == 0) &&
                                          (m->busy == 0) &&
                                          (m->hold_count == 0))
                                          vm_page_cache(m);
                          }
  
                          for (m = TAILQ_FIRST(&vm_page_queue_active);
                                  m != NULL;
                                  m = next) {
  
                                  if (m->queue != PQ_ACTIVE) {
                                          break;
                                  }
  
                                  next = TAILQ_NEXT(m, pageq);
                                  if (m->flags & PG_BUSY) {
                                          m->flags |= PG_WANTED;
                                          tsleep(m, PVM, "vpctw1", 0);
                                          goto again1;
                                  }
                                  vm_page_test_dirty(m);
                                  if (m->dirty) {
                                          if (m->object->type == OBJT_VNODE) {
                                                  vm_object_page_clean(m->object, 0, 0, TRUE, TRUE);
                                                  goto again1;
                                          } else if (m->object->type == OBJT_SWAP ||
                                                                  m->object->type == OBJT_DEFAULT) {
                                                  vm_page_protect(m, VM_PROT_NONE);
                                                  vm_pageout_flush(&m, 1, 0);
                                                  goto again1;
                                          }
                                  }
                                  if ((m->dirty == 0) &&
                                          (m->busy == 0) &&
                                          (m->hold_count == 0))
                                          vm_page_cache(m);
                          }
  
                          splx(s);
                          continue;
                  }
                  start = i;
  
                  /*
                   * Check successive pages for contiguous and free.
                   */
                  for (i = start + 1; i < (start + size / PAGE_SIZE); i++) {
                          int pqtype;
                          pqtype = pga[i].queue - pga[i].pc;
                          if ((VM_PAGE_TO_PHYS(&pga[i]) !=
                              (VM_PAGE_TO_PHYS(&pga[i - 1]) + PAGE_SIZE)) ||
                              ((pqtype != PQ_ZERO) && (pqtype != PQ_FREE) && (pqtype != PQ_CACHE))) {
                                  start++;
                                  goto again;
                          }
                  }
  
                  for (i = start; i < (start + size / PAGE_SIZE); i++) {
                          int pqtype;
                          vm_page_t m = &pga[i];
  
                          pqtype = m->queue - m->pc;
                          if (pqtype == PQ_CACHE)
                                  vm_page_free(m);
  
                          TAILQ_REMOVE(vm_page_queues[m->queue].pl, m, pageq);
                          --(*vm_page_queues[m->queue].lcnt);
                          cnt.v_free_count--;
                          m->valid = VM_PAGE_BITS_ALL;
                          m->flags = 0;
                          m->dirty = 0;
                          m->wire_count = 0;
                          m->busy = 0;
                          m->queue = PQ_NONE;
                          m->object = NULL;
                          vm_page_wire(m);
                  }
  
                  /*
                   * We've found a contiguous chunk that meets are requirements.
                   * Allocate kernel VM, unfree and assign the physical pages to it and
                   * return kernel VM pointer.
                   */
                  tmp_addr = addr = kmem_alloc_pageable(kernel_map, size);
                  if (addr == 0) {
                          /*
                           * XXX We almost never run out of kernel virtual
                           * space, so we don't make the allocated memory
                           * above available.
                           */
                          splx(s);
                          return (NULL);
                  }
  
                  for (i = start; i < (start + size / PAGE_SIZE); i++) {
                          vm_page_t m = &pga[i];
                          vm_page_insert(m, kernel_object,
                                  OFF_TO_IDX(tmp_addr - VM_MIN_KERNEL_ADDRESS));
                          pmap_kenter(tmp_addr, VM_PAGE_TO_PHYS(m));
                          tmp_addr += PAGE_SIZE;
                  }
  
                  splx(s);
                  return ((void *)addr);
          }
          return NULL;
  }
  
  vm_offset_t
  vm_page_alloc_contig(size, low, high, alignment)
          vm_offset_t size;
          vm_offset_t low;
          vm_offset_t high;
          vm_offset_t alignment;
  {
          return ((vm_offset_t)contigmalloc(size, M_DEVBUF, M_NOWAIT, low, high,
                                            alignment, 0ul));
  }
  
  #include "opt_ddb.h"
  #ifdef DDB
  #include <sys/kernel.h>
  
  #include <ddb/ddb.h>
  
  DB_SHOW_COMMAND(page, vm_page_print_page_info)
  {
          db_printf("cnt.v_free_count: %d\n", cnt.v_free_count);
          db_printf("cnt.v_cache_count: %d\n", cnt.v_cache_count);
          db_printf("cnt.v_inactive_count: %d\n", cnt.v_inactive_count);
          db_printf("cnt.v_active_count: %d\n", cnt.v_active_count);
          db_printf("cnt.v_wire_count: %d\n", cnt.v_wire_count);
          db_printf("cnt.v_free_reserved: %d\n", cnt.v_free_reserved);
          db_printf("cnt.v_free_min: %d\n", cnt.v_free_min);
          db_printf("cnt.v_free_target: %d\n", cnt.v_free_target);
          db_printf("cnt.v_cache_min: %d\n", cnt.v_cache_min);
          db_printf("cnt.v_inactive_target: %d\n", cnt.v_inactive_target);
  }
  
  DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
  {
          int i;
          db_printf("PQ_FREE:");
          for(i=0;i<PQ_L2_SIZE;i++) {
                  db_printf(" %d", *vm_page_queues[PQ_FREE + i].lcnt);
          }
          db_printf("\n");
                  
          db_printf("PQ_CACHE:");
          for(i=0;i<PQ_L2_SIZE;i++) {
                  db_printf(" %d", *vm_page_queues[PQ_CACHE + i].lcnt);
          }
          db_printf("\n");
  
          db_printf("PQ_ZERO:");
          for(i=0;i<PQ_L2_SIZE;i++) {
                  db_printf(" %d", *vm_page_queues[PQ_ZERO + i].lcnt);
          }
          db_printf("\n");
  
          db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
                  *vm_page_queues[PQ_ACTIVE].lcnt,
                  *vm_page_queues[PQ_INACTIVE].lcnt);
  }
  #endif /* DDB */

Cache object: b9fbf85e12c71db40a04eefdd02e09be