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

     /*
      * Copyright (c) 1991 Regents of the University of California.
      * All rights reserved.
      * Copyright (c) 1994 John S. Dyson
      * All rights reserved.
      * Copyright (c) 1994 David Greenman
      * 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_pageout.c  7.4 (Berkeley) 5/7/91
     *
     *
     * 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.
     *
     * $FreeBSD$
     */
    
    /*
     *      The proverbial page-out daemon.
     */
    
    #include "opt_vm.h"
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/resourcevar.h>
    #include <sys/signalvar.h>
    #include <sys/vnode.h>
    #include <sys/vmmeter.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_prot.h>
    #include <sys/lock.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_map.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_pager.h>
    #include <vm/swap_pager.h>
    #include <vm/vm_extern.h>
    
    /*
     * System initialization
    */
   
   /* the kernel process "vm_pageout"*/
   static void vm_pageout __P((void));
   static int vm_pageout_clean __P((vm_page_t));
   static int vm_pageout_scan __P((void));
   static int vm_pageout_free_page_calc __P((vm_size_t count));
   struct proc *pageproc;
   
   static struct kproc_desc page_kp = {
           "pagedaemon",
           vm_pageout,
           &pageproc
   };
   SYSINIT_KT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
   
   #if !defined(NO_SWAPPING)
   /* the kernel process "vm_daemon"*/
   static void vm_daemon __P((void));
   static struct   proc *vmproc;
   
   static struct kproc_desc vm_kp = {
           "vmdaemon",
           vm_daemon,
           &vmproc
   };
   SYSINIT_KT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
   #endif
   
   
   int vm_pages_needed=0;          /* Event on which pageout daemon sleeps */
   int vm_pageout_deficit=0;       /* Estimated number of pages deficit */
   int vm_pageout_pages_needed=0;  /* flag saying that the pageout daemon needs pages */
   
   extern int npendingio;
   #if !defined(NO_SWAPPING)
   static int vm_pageout_req_swapout;      /* XXX */
   static int vm_daemon_needed;
   #endif
   extern int nswiodone;
   extern int vm_swap_size;
   extern int vfs_update_wakeup;
   static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
   static int vm_pageout_full_stats_interval = 0;
   static int vm_pageout_stats_free_max=0, vm_pageout_algorithm_lru=0;
   static int defer_swap_pageouts=0;
   static int disable_swap_pageouts=0;
   
   static int max_page_launder=100;
   #if defined(NO_SWAPPING)
   static int vm_swap_enabled=0;
   static int vm_swap_idle_enabled=0;
   #else
   static int vm_swap_enabled=1;
   static int vm_swap_idle_enabled=0;
   #endif
   
   SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
           CTLFLAG_RW, &vm_pageout_algorithm_lru, 0, "LRU page mgmt");
   
   SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
           CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
   
   SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
           CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
   
   SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
           CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
   
   SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
           CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
   
   #if defined(NO_SWAPPING)
   SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
           CTLFLAG_RD, &vm_swap_enabled, 0, "");
   SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
           CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
   #else
   SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
           CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
   SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
           CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
   #endif
   
   SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
           CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
   
   SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
           CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
   
   SYSCTL_INT(_vm, OID_AUTO, max_page_launder,
           CTLFLAG_RW, &max_page_launder, 0, "Maximum number of pages to clean per pass");
   
   
   #define VM_PAGEOUT_PAGE_COUNT 16
   int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
   
   int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
   
   #if !defined(NO_SWAPPING)
   typedef void freeer_fcn_t __P((vm_map_t, vm_object_t, vm_pindex_t, int));
   static void vm_pageout_map_deactivate_pages __P((vm_map_t, vm_pindex_t));
   static freeer_fcn_t vm_pageout_object_deactivate_pages;
   static void vm_req_vmdaemon __P((void));
   #endif
   static void vm_pageout_page_stats(void);
   void pmap_collect(void);
   
   /*
    * vm_pageout_clean:
    *
    * Clean the page and remove it from the laundry.
    * 
    * We set the busy bit to cause potential page faults on this page to
    * block.  Note the careful timing, however, the busy bit isn't set till
    * late and we cannot do anything that will mess with the page.
    */
   
   static int
   vm_pageout_clean(m)
           vm_page_t m;
   {
           register vm_object_t object;
           vm_page_t mc[2*vm_pageout_page_count];
           int pageout_count;
           int i, forward_okay, backward_okay, page_base;
           vm_pindex_t pindex = m->pindex;
   
           object = m->object;
   
           /*
            * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
            * with the new swapper, but we could have serious problems paging
            * out other object types if there is insufficient memory.  
            *
            * Unfortunately, checking free memory here is far too late, so the
            * check has been moved up a procedural level.
            */
   
   #if 1
           /*
            * If not OBJT_SWAP, additional memory may be needed to do the pageout.
            * Try to avoid the deadlock.
            */
           if ((object->type == OBJT_DEFAULT) &&
               ((cnt.v_free_count + cnt.v_cache_count) < cnt.v_pageout_free_min))
                   return 0;
   #endif
   
           /*
            * Don't mess with the page if it's busy.
            */
           if ((m->hold_count != 0) ||
               ((m->busy != 0) || (m->flags & PG_BUSY)))
                   return 0;
   
   #if 0
           /*
            * XXX REMOVED XXX.  vm_object_collapse() can block, which can
            * change the page state.  Calling vm_object_collapse() might also
            * destroy or rename the page because we have not busied it yet!!!
            * So this code segment is removed.
            */
           /*
            * Try collapsing before it's too late.   XXX huh?  Why are we doing
            * this here?
            */
           if (object->backing_object) {
                   vm_object_collapse(object);
           }
   #endif
   
           mc[vm_pageout_page_count] = m;
           pageout_count = 1;
           page_base = vm_pageout_page_count;
           forward_okay = TRUE;
           if (pindex != 0)
                   backward_okay = TRUE;
           else
                   backward_okay = FALSE;
           /*
            * Scan object for clusterable pages.
            *
            * We can cluster ONLY if: ->> the page is NOT
            * clean, wired, busy, held, or mapped into a
            * buffer, and one of the following:
            * 1) The page is inactive, or a seldom used
            *    active page.
            * -or-
            * 2) we force the issue.
            */
           for (i = 1; (i < vm_pageout_page_count) && (forward_okay || backward_okay); i++) {
                   vm_page_t p;
   
                   /*
                    * See if forward page is clusterable.
                    */
                   if (forward_okay) {
                           /*
                            * Stop forward scan at end of object.
                            */
                           if ((pindex + i) > object->size) {
                                   forward_okay = FALSE;
                                   goto do_backward;
                           }
                           p = vm_page_lookup(object, pindex + i);
                           if (p) {
                                   if (((p->queue - p->pc) == PQ_CACHE) ||
                                           (p->flags & PG_BUSY) || p->busy) {
                                           forward_okay = FALSE;
                                           goto do_backward;
                                   }
                                   vm_page_test_dirty(p);
                                   if ((p->dirty & p->valid) != 0 &&
                                       (p->queue == PQ_INACTIVE) &&
                                       (p->wire_count == 0) &&
                                       (p->hold_count == 0)) {
                                           mc[vm_pageout_page_count + i] = p;
                                           pageout_count++;
                                           if (pageout_count == vm_pageout_page_count)
                                                   break;
                                   } else {
                                           forward_okay = FALSE;
                                   }
                           } else {
                                   forward_okay = FALSE;
                           }
                   }
   do_backward:
                   /*
                    * See if backward page is clusterable.
                    */
                   if (backward_okay) {
                           /*
                            * Stop backward scan at beginning of object.
                            */
                           if ((pindex - i) == 0) {
                                   backward_okay = FALSE;
                           }
                           p = vm_page_lookup(object, pindex - i);
                           if (p) {
                                   if (((p->queue - p->pc) == PQ_CACHE) ||
                                           (p->flags & PG_BUSY) || p->busy) {
                                           backward_okay = FALSE;
                                           continue;
                                   }
                                   vm_page_test_dirty(p);
                                   if ((p->dirty & p->valid) != 0 &&
                                       (p->queue == PQ_INACTIVE) &&
                                       (p->wire_count == 0) &&
                                       (p->hold_count == 0)) {
                                           mc[vm_pageout_page_count - i] = p;
                                           pageout_count++;
                                           page_base--;
                                           if (pageout_count == vm_pageout_page_count)
                                                   break;
                                   } else {
                                           backward_okay = FALSE;
                                   }
                           } else {
                                   backward_okay = FALSE;
                           }
                   }
           }
   
           /*
            * we allow reads during pageouts...
            */
           return vm_pageout_flush(&mc[page_base], pageout_count, 0);
   }
   
   /*
    * vm_pageout_flush() - launder the given pages
    *
    *      The given pages are laundered.  Note that we setup for the start of
    *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
    *      reference count all in here rather then in the parent.  If we want
    *      the parent to do more sophisticated things we may have to change
    *      the ordering.
    */
   
   int
   vm_pageout_flush(mc, count, flags)
           vm_page_t *mc;
           int count;
           int flags;
   {
           register vm_object_t object;
           int pageout_status[count];
           int numpagedout = 0;
           int i;
   
           /*
            * Initiate I/O.  Bump the vm_page_t->busy counter and
            * mark the pages read-only.
            *
            * We do not have to fixup the clean/dirty bits here... we can
            * allow the pager to do it after the I/O completes.
            */
   
           for (i = 0; i < count; i++) {
                   vm_page_io_start(mc[i]);
                   vm_page_protect(mc[i], VM_PROT_READ);
           }
   
           object = mc[0]->object;
           vm_object_pip_add(object, count);
   
           vm_pager_put_pages(object, mc, count,
               (flags | ((object == kernel_object) ? OBJPC_SYNC : 0)),
               pageout_status);
   
           for (i = 0; i < count; i++) {
                   vm_page_t mt = mc[i];
   
                   switch (pageout_status[i]) {
                   case VM_PAGER_OK:
                           numpagedout++;
                           break;
                   case VM_PAGER_PEND:
                           numpagedout++;
                           break;
                   case VM_PAGER_BAD:
                           /*
                            * Page outside of range of object. Right now we
                            * essentially lose the changes by pretending it
                            * worked.
                            */
                           pmap_clear_modify(VM_PAGE_TO_PHYS(mt));
                           mt->dirty = 0;
                           break;
                   case VM_PAGER_ERROR:
                   case VM_PAGER_FAIL:
                           /*
                            * If page couldn't be paged out, then reactivate the
                            * page so it doesn't clog the inactive list.  (We
                            * will try paging out it again later).
                            */
                           vm_page_activate(mt);
                           break;
                   case VM_PAGER_AGAIN:
                           break;
                   }
   
                   /*
                    * If the operation is still going, leave the page busy to
                    * block all other accesses. Also, leave the paging in
                    * progress indicator set so that we don't attempt an object
                    * collapse.
                    */
                   if (pageout_status[i] != VM_PAGER_PEND) {
                           vm_object_pip_wakeup(object);
                           vm_page_io_finish(mt);
                   }
           }
           return numpagedout;
   }
   
   #if !defined(NO_SWAPPING)
   /*
    *      vm_pageout_object_deactivate_pages
    *
    *      deactivate enough pages to satisfy the inactive target
    *      requirements or if vm_page_proc_limit is set, then
    *      deactivate all of the pages in the object and its
    *      backing_objects.
    *
    *      The object and map must be locked.
    */
   static void
   vm_pageout_object_deactivate_pages(map, object, desired, map_remove_only)
           vm_map_t map;
           vm_object_t object;
           vm_pindex_t desired;
           int map_remove_only;
   {
           register vm_page_t p, next;
           int rcount;
           int remove_mode;
           int s;
   
           if (object->type == OBJT_DEVICE)
                   return;
   
           while (object) {
                   if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
                           return;
                   if (object->paging_in_progress)
                           return;
   
                   remove_mode = map_remove_only;
                   if (object->shadow_count > 1)
                           remove_mode = 1;
           /*
            * scan the objects entire memory queue
            */
                   rcount = object->resident_page_count;
                   p = TAILQ_FIRST(&object->memq);
                   while (p && (rcount-- > 0)) {
                           int actcount;
                           if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
                                   return;
                           next = TAILQ_NEXT(p, listq);
                           cnt.v_pdpages++;
                           if (p->wire_count != 0 ||
                               p->hold_count != 0 ||
                               p->busy != 0 ||
                               (p->flags & PG_BUSY) ||
                               !pmap_page_exists(vm_map_pmap(map), VM_PAGE_TO_PHYS(p))) {
                                   p = next;
                                   continue;
                           }
   
                           actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(p));
                           if (actcount) {
                                   vm_page_flag_set(p, PG_REFERENCED);
                           } else if (p->flags & PG_REFERENCED) {
                                   actcount = 1;
                           }
   
                           if ((p->queue != PQ_ACTIVE) &&
                                   (p->flags & PG_REFERENCED)) {
                                   vm_page_activate(p);
                                   p->act_count += actcount;
                                   vm_page_flag_clear(p, PG_REFERENCED);
                           } else if (p->queue == PQ_ACTIVE) {
                                   if ((p->flags & PG_REFERENCED) == 0) {
                                           p->act_count -= min(p->act_count, ACT_DECLINE);
                                           if (!remove_mode && (vm_pageout_algorithm_lru || (p->act_count == 0))) {
                                                   vm_page_protect(p, VM_PROT_NONE);
                                                   vm_page_deactivate(p);
                                           } else {
                                                   s = splvm();
                                                   TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
                                                   TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
                                                   splx(s);
                                           }
                                   } else {
                                           vm_page_activate(p);
                                           vm_page_flag_clear(p, PG_REFERENCED);
                                           if (p->act_count < (ACT_MAX - ACT_ADVANCE))
                                                   p->act_count += ACT_ADVANCE;
                                           s = splvm();
                                           TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
                                           TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
                                           splx(s);
                                   }
                           } else if (p->queue == PQ_INACTIVE) {
                                   vm_page_protect(p, VM_PROT_NONE);
                           }
                           p = next;
                   }
                   object = object->backing_object;
           }
           return;
   }
   
   /*
    * deactivate some number of pages in a map, try to do it fairly, but
    * that is really hard to do.
    */
   static void
   vm_pageout_map_deactivate_pages(map, desired)
           vm_map_t map;
           vm_pindex_t desired;
   {
           vm_map_entry_t tmpe;
           vm_object_t obj, bigobj;
   
           if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT, (void *)0, curproc)) {
                   return;
           }
   
           bigobj = NULL;
   
           /*
            * first, search out the biggest object, and try to free pages from
            * that.
            */
           tmpe = map->header.next;
           while (tmpe != &map->header) {
                   if ((tmpe->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
                           obj = tmpe->object.vm_object;
                           if ((obj != NULL) && (obj->shadow_count <= 1) &&
                                   ((bigobj == NULL) ||
                                    (bigobj->resident_page_count < obj->resident_page_count))) {
                                   bigobj = obj;
                           }
                   }
                   tmpe = tmpe->next;
           }
   
           if (bigobj)
                   vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
   
           /*
            * Next, hunt around for other pages to deactivate.  We actually
            * do this search sort of wrong -- .text first is not the best idea.
            */
           tmpe = map->header.next;
           while (tmpe != &map->header) {
                   if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
                           break;
                   if ((tmpe->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
                           obj = tmpe->object.vm_object;
                           if (obj)
                                   vm_pageout_object_deactivate_pages(map, obj, desired, 0);
                   }
                   tmpe = tmpe->next;
           };
   
           /*
            * Remove all mappings if a process is swapped out, this will free page
            * table pages.
            */
           if (desired == 0)
                   pmap_remove(vm_map_pmap(map),
                           VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS);
           vm_map_unlock(map);
           return;
   }
   #endif
   
   /*
    * Don't try to be fancy - being fancy can lead to VOP_LOCK's and therefore
    * to vnode deadlocks.  We only do it for OBJT_DEFAULT and OBJT_SWAP objects
    * which we know can be trivially freed.
    */
   
   void
   vm_pageout_page_free(vm_page_t m) {
           vm_object_t object = m->object;
           int type = object->type;
   
           if (type == OBJT_SWAP || type == OBJT_DEFAULT)
                   vm_object_reference(object);
           vm_page_busy(m);
           vm_page_protect(m, VM_PROT_NONE);
           vm_page_free(m);
           if (type == OBJT_SWAP || type == OBJT_DEFAULT)
                   vm_object_deallocate(object);
   }
   
   /*
    *      vm_pageout_scan does the dirty work for the pageout daemon.
    */
   static int
   vm_pageout_scan()
   {
           vm_page_t m, next;
           int page_shortage, maxscan, pcount;
           int addl_page_shortage, addl_page_shortage_init;
           int maxlaunder;
           int launder_loop = 0;
           struct proc *p, *bigproc;
           vm_offset_t size, bigsize;
           vm_object_t object;
           int force_wakeup = 0;
           int actcount;
           int vnodes_skipped = 0;
           int s;
   
           /*
            * Do whatever cleanup that the pmap code can.
            */
           pmap_collect();
   
           addl_page_shortage_init = vm_pageout_deficit;
           vm_pageout_deficit = 0;
   
           if (max_page_launder == 0)
                   max_page_launder = 1;
   
           /*
            * Calculate the number of pages we want to either free or move
            * to the cache.
            */
   
           page_shortage = (cnt.v_free_target + cnt.v_cache_min) -
               (cnt.v_free_count + cnt.v_cache_count);
           page_shortage += addl_page_shortage_init;
   
           /*
            * Figure out what to do with dirty pages when they are encountered.
            * Assume that 1/3 of the pages on the inactive list are clean.  If
            * we think we can reach our target, disable laundering (do not
            * clean any dirty pages).  If we miss the target we will loop back
            * up and do a laundering run.
            */
   
           if (cnt.v_inactive_count / 3 > page_shortage) {
                   maxlaunder = 0;
                   launder_loop = 0;
           } else {
                   maxlaunder = 
                       (cnt.v_inactive_target > max_page_launder) ?
                       max_page_launder : cnt.v_inactive_target;
                   launder_loop = 1;
           }
   
           /*
            * Start scanning the inactive queue for pages we can move to the
            * cache or free.  The scan will stop when the target is reached or
            * we have scanned the entire inactive queue.
            */
   
   rescan0:
           addl_page_shortage = addl_page_shortage_init;
           maxscan = cnt.v_inactive_count;
           for (
               m = TAILQ_FIRST(&vm_page_queue_inactive);
               m != NULL && maxscan-- > 0 && page_shortage > 0;
               m = next
           ) {
   
                   cnt.v_pdpages++;
   
                   if (m->queue != PQ_INACTIVE) {
                           goto rescan0;
                   }
   
                   next = TAILQ_NEXT(m, pageq);
   
                   if (m->hold_count) {
                           s = splvm();
                           TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
                           TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                           splx(s);
                           addl_page_shortage++;
                           continue;
                   }
                   /*
                    * Dont mess with busy pages, keep in the front of the
                    * queue, most likely are being paged out.
                    */
                   if (m->busy || (m->flags & PG_BUSY)) {
                           addl_page_shortage++;
                           continue;
                   }
   
                   /*
                    * If the object is not being used, we ignore previous 
                    * references.
                    */
                   if (m->object->ref_count == 0) {
                           vm_page_flag_clear(m, PG_REFERENCED);
                           pmap_clear_reference(VM_PAGE_TO_PHYS(m));
   
                   /*
                    * Otherwise, if the page has been referenced while in the 
                    * inactive queue, we bump the "activation count" upwards, 
                    * making it less likely that the page will be added back to 
                    * the inactive queue prematurely again.  Here we check the 
                    * page tables (or emulated bits, if any), given the upper 
                    * level VM system not knowing anything about existing 
                    * references.
                    */
                   } else if (((m->flags & PG_REFERENCED) == 0) &&
                           (actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(m)))) {
                           vm_page_activate(m);
                           m->act_count += (actcount + ACT_ADVANCE);
                           continue;
                   }
   
                   /*
                    * If the upper level VM system knows about any page 
                    * references, we activate the page.  We also set the 
                    * "activation count" higher than normal so that we will less 
                    * likely place pages back onto the inactive queue again.
                    */
                   if ((m->flags & PG_REFERENCED) != 0) {
                           vm_page_flag_clear(m, PG_REFERENCED);
                           actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
                           vm_page_activate(m);
                           m->act_count += (actcount + ACT_ADVANCE + 1);
                           continue;
                   }
   
                   /*
                    * If the upper level VM system doesn't know anything about 
                    * the page being dirty, we have to check for it again.  As 
                    * far as the VM code knows, any partially dirty pages are 
                    * fully dirty.
                    */
                   if (m->dirty == 0) {
                           vm_page_test_dirty(m);
                   } else {
                           m->dirty = VM_PAGE_BITS_ALL;
                   }
   
                   /*
                    * Invalid pages can be easily freed
                    */
                   if (m->valid == 0) {
                           vm_pageout_page_free(m);
                           cnt.v_dfree++;
                           --page_shortage;
   
                   /*
                    * Clean pages can be placed onto the cache queue.
                    */
                   } else if (m->dirty == 0) {
                           vm_page_cache(m);
                           --page_shortage;
   
                   /*
                    * Dirty pages need to be paged out.  Note that we clean
                    * only a limited number of pages per pagedaemon pass.
                    */
                   } else if (maxlaunder > 0) {
                           int written;
                           int swap_pageouts_ok;
                           struct vnode *vp = NULL;
   
                           object = m->object;
   
                           if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
                                   swap_pageouts_ok = 1;
                           } else {
                                   swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
                                   swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
                                           (cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min);
                                                                                   
                           }
   
                           /*
                            * We don't bother paging objects that are "dead".  
                            * Those objects are in a "rundown" state.
                            */
                           if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
                                   s = splvm();
                                   TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
                                   TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                                   splx(s);
                                   continue;
                           }
   
                           /*
                            * For now we protect against potential memory
                            * deadlocks by requiring significant memory to be 
                            * free if the object is not OBJT_DEFAULT or OBJT_SWAP.
                            * We do not 'trust' any other object type to operate
                            * with low memory, not even OBJT_DEVICE.  The VM
                            * allocator will special case allocations done by
                            * the pageout daemon so the check below actually 
                            * does have some hysteresis in it.  It isn't the best
                            * solution, though.
                            */
   
                           if (
                               object->type != OBJT_DEFAULT &&
                               object->type != OBJT_SWAP &&
                               cnt.v_free_count < cnt.v_free_reserved
                           ) {
                                   s = splvm();
                                   TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
                                   TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                                   splx(s);
                                   continue;
                           }
   
                           /*
                            * Presumably we have sufficient free memory to do
                            * the more sophisticated checks and locking required
                            * for vnodes.
                            *
                            * The object is already known NOT to be dead.  The
                            * vget() may still block, though, because 
                            * VOP_ISLOCKED() doesn't check to see if an inode
                            * (v_data) is associated with the vnode.  If it isn't,
                            * vget() will load in it from disk.  Worse, vget()
                            * may actually get stuck waiting on "inode" if another
                            * process is in the process of bringing the inode in.
                            * This is bad news for us either way.
                            *
                            * So for the moment we check v_data == NULL as a
                            * workaround.  This means that vnodes which do not
                            * use v_data in the way we expect probably will not
                            * wind up being paged out by the pager and it will be
                            * up to the syncer to get them.  That's better then
                            * us blocking here.
                            *
                            * This whole code section is bogus - we need to fix
                            * the vnode pager to handle vm_page_t's without us
                            * having to do any sophisticated VOP tests.
                            */
   
                           if (object->type == OBJT_VNODE) {
                                   vp = object->handle;
   
                                   if (VOP_ISLOCKED(vp) ||
                                       vp->v_data == NULL ||
                                       vget(vp, LK_EXCLUSIVE|LK_NOOBJ, curproc)) {
                                           if ((m->queue == PQ_INACTIVE) &&
                                                   (m->hold_count == 0) &&
                                                   (m->busy == 0) &&
                                                   (m->flags & PG_BUSY) == 0) {
                                                   s = splvm();
                                                   TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
                                                   TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                                                   splx(s);
                                           }
                                           if (object->flags & OBJ_MIGHTBEDIRTY)
                                                   vnodes_skipped++;
                                           continue;
                                   }
   
                                   /*
                                    * The page might have been moved to another queue
                                    * during potential blocking in vget() above.
                                    */
                                   if (m->queue != PQ_INACTIVE) {
                                           if (object->flags & OBJ_MIGHTBEDIRTY)
                                                   vnodes_skipped++;
                                           vput(vp);
                                           continue;
                                   }
           
                                   /*
                                    * The page may have been busied during the blocking in
                                    * vput();  We don't move the page back onto the end of
                                    * the queue so that statistics are more correct if we don't.
                                    */
                                   if (m->busy || (m->flags & PG_BUSY)) {
                                           vput(vp);
                                           continue;
                                   }
   
                                   /*
                                    * If the page has become held, then skip it
                                    */
                                   if (m->hold_count) {
                                           s = splvm();
                                           TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
                                           TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
                                           splx(s);
                                           if (object->flags & OBJ_MIGHTBEDIRTY)
                                                   vnodes_skipped++;
                                           vput(vp);
                                           continue;
                                   }
                           }
   
                           /*
                            * If a page is dirty, then it is either being washed
                            * (but not yet cleaned) or it is still in the
                            * laundry.  If it is still in the laundry, then we
                            * start the cleaning operation.
                            */
                           written = vm_pageout_clean(m);
                           if (vp)
                                   vput(vp);
   
                           maxlaunder -= written;
                   }
           }
   
           /*
            * If we still have a page shortage and we didn't launder anything,
            * run the inactive scan again and launder something this time.
            */
   
           if (launder_loop == 0 && page_shortage > 0) {
                   launder_loop = 1;
                   maxlaunder = 
                       (cnt.v_inactive_target > max_page_launder) ?
                       max_page_launder : cnt.v_inactive_target;
                   goto rescan0;
           }
   
           /*
            * Compute the page shortage from the point of view of having to
            * move pages from the active queue to the inactive queue.
            */
   
           page_shortage = (cnt.v_inactive_target + cnt.v_cache_min) -
               (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
           page_shortage += addl_page_shortage;
   
           /*
            * Scan the active queue for things we can deactivate
            */
   
           pcount = cnt.v_active_count;
           m = TAILQ_FIRST(&vm_page_queue_active);
   
           while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
   
                   /*
                    * This is a consistancy check, and should likely be a panic
                    * or warning.
                    */
                   if (m->queue != PQ_ACTIVE) {
                           break;
                   }
   
                   next = TAILQ_NEXT(m, pageq);
                   /*
                    * Don't deactivate pages that are busy.
                    */
                  if ((m->busy != 0) ||
                      (m->flags & PG_BUSY) ||
                      (m->hold_count != 0)) {
                          s = splvm();
                          TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                          TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                          splx(s);
                          m = next;
                          continue;
                  }
  
                  /*
                   * The count for pagedaemon pages is done after checking the
                   * page for eligbility...
                   */
                  cnt.v_pdpages++;
  
                  /*
                   * Check to see "how much" the page has been used.
                   */
                  actcount = 0;
                  if (m->object->ref_count != 0) {
                          if (m->flags & PG_REFERENCED) {
                                  actcount += 1;
                          }
                          actcount += pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
                          if (actcount) {
                                  m->act_count += ACT_ADVANCE + actcount;
                                  if (m->act_count > ACT_MAX)
                                          m->act_count = ACT_MAX;
                          }
                  }
  
                  /*
                   * Since we have "tested" this bit, we need to clear it now.
                   */
                  vm_page_flag_clear(m, PG_REFERENCED);
  
                  /*
                   * Only if an object is currently being used, do we use the
                   * page activation count stats.
                   */
                  if (actcount && (m->object->ref_count != 0)) {
                          s = splvm();
                          TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                          TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                          splx(s);
                  } else {
                          m->act_count -= min(m->act_count, ACT_DECLINE);
                          if (vm_pageout_algorithm_lru ||
                                  (m->object->ref_count == 0) || (m->act_count == 0)) {
                                  page_shortage--;
                                  if (m->object->ref_count == 0) {
                                          vm_page_protect(m, VM_PROT_NONE);
                                          if (m->dirty == 0)
                                                  vm_page_cache(m);
                                          else
                                                  vm_page_deactivate(m);
                                  } else {
                                          vm_page_deactivate(m);
                                  }
                          } else {
                                  s = splvm();
                                  TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                                  TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                                  splx(s);
                          }
                  }
                  m = next;
          }
  
          s = splvm();
  
          /*
           * We try to maintain some *really* free pages, this allows interrupt
           * code to be guaranteed space.  Since both cache and free queues 
           * are considered basically 'free', moving pages from cache to free
           * does not effect other calculations.
           */
  
          while (cnt.v_free_count < cnt.v_free_reserved) {
                  static int cache_rover = 0;
                  m = vm_page_list_find(PQ_CACHE, cache_rover);
                  if (!m)
                          break;
                  if ((m->flags & PG_BUSY) || m->busy || m->hold_count || m->wire_count) {
  #ifdef INVARIANTS
                          printf("Warning: busy page %p found in cache\n", m);
  #endif
                          vm_page_deactivate(m);
                          continue;
                  }
                  cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK;
                  vm_pageout_page_free(m);
                  cnt.v_dfree++;
          }
          splx(s);
  
  #if !defined(NO_SWAPPING)
          /*
           * Idle process swapout -- run once per second.
           */
          if (vm_swap_idle_enabled) {
                  static long lsec;
                  if (time_second != lsec) {
                          vm_pageout_req_swapout |= VM_SWAP_IDLE;
                          vm_req_vmdaemon();
                          lsec = time_second;
                  }
          }
  #endif
                  
          /*
           * If we didn't get enough free pages, and we have skipped a vnode
           * in a writeable object, wakeup the sync daemon.  And kick swapout
           * if we did not get enough free pages.
           */
          if ((cnt.v_cache_count + cnt.v_free_count) <
                  (cnt.v_free_target + cnt.v_cache_min) ) {
                  if (vnodes_skipped &&
                      (cnt.v_cache_count + cnt.v_free_count) < cnt.v_free_min) {
                          if (!vfs_update_wakeup) {
                                  vfs_update_wakeup = 1;
                                  wakeup(&vfs_update_wakeup);
                          }
                  }
  #if !defined(NO_SWAPPING)
                  if (vm_swap_enabled &&
                          (cnt.v_free_count + cnt.v_cache_count < cnt.v_free_target)) {
                          vm_req_vmdaemon();
                          vm_pageout_req_swapout |= VM_SWAP_NORMAL;
                  }
  #endif
          }
  
          /*
           * make sure that we have swap space -- if we are low on memory and
           * swap -- then kill the biggest process.
           */
          if ((vm_swap_size == 0 || swap_pager_full) &&
              ((cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min)) {
                  bigproc = NULL;
                  bigsize = 0;
                  for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
                          /*
                           * if this is a system process, skip it
                           */
                          if ((p->p_flag & (P_SYSTEM|P_NOSWAP)) || (p->p_pid == 1) ||
                              ((p->p_pid < 48) && (vm_swap_size != 0))) {
                                  continue;
                          }
                          /*
                           * if the process is in a non-running type state,
                           * don't touch it.
                           */
                          if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
                                  continue;
                          }
                          /*
                           * get the process size
                           */
                          size = p->p_vmspace->vm_pmap.pm_stats.resident_count;
                          /*
                           * if the this process is bigger than the biggest one
                           * remember it.
                           */
                          if (size > bigsize) {
                                  bigproc = p;
                                  bigsize = size;
                          }
                  }
                  if (bigproc != NULL) {
                          killproc(bigproc, "out of swap space");
                          bigproc->p_estcpu = 0;
                          bigproc->p_nice = PRIO_MIN;
                          resetpriority(bigproc);
                          wakeup(&cnt.v_free_count);
                  }
          }
          return force_wakeup;
  }
  
  /*
   * This routine tries to maintain the pseudo LRU active queue,
   * so that during long periods of time where there is no paging,
   * that some statistic accumlation still occurs.  This code
   * helps the situation where paging just starts to occur.
   */
  static void
  vm_pageout_page_stats()
  {
          int s;
          vm_page_t m,next;
          int pcount,tpcount;             /* Number of pages to check */
          static int fullintervalcount = 0;
          int page_shortage;
  
          page_shortage = (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
              (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
          if (page_shortage <= 0)
                  return;
  
          pcount = cnt.v_active_count;
          fullintervalcount += vm_pageout_stats_interval;
          if (fullintervalcount < vm_pageout_full_stats_interval) {
                  tpcount = (vm_pageout_stats_max * cnt.v_active_count) / cnt.v_page_count;
                  if (pcount > tpcount)
                          pcount = tpcount;
          }
  
          m = TAILQ_FIRST(&vm_page_queue_active);
          while ((m != NULL) && (pcount-- > 0)) {
                  int actcount;
  
                  if (m->queue != PQ_ACTIVE) {
                          break;
                  }
  
                  next = TAILQ_NEXT(m, pageq);
                  /*
                   * Don't deactivate pages that are busy.
                   */
                  if ((m->busy != 0) ||
                      (m->flags & PG_BUSY) ||
                      (m->hold_count != 0)) {
                          s = splvm();
                          TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                          TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                          splx(s);
                          m = next;
                          continue;
                  }
  
                  actcount = 0;
                  if (m->flags & PG_REFERENCED) {
                          vm_page_flag_clear(m, PG_REFERENCED);
                          actcount += 1;
                  }
  
                  actcount += pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
                  if (actcount) {
                          m->act_count += ACT_ADVANCE + actcount;
                          if (m->act_count > ACT_MAX)
                                  m->act_count = ACT_MAX;
                          s = splvm();
                          TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                          TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                          splx(s);
                  } else {
                          if (m->act_count == 0) {
                                  /*
                                   * We turn off page access, so that we have more accurate
                                   * RSS stats.  We don't do this in the normal page deactivation
                                   * when the system is loaded VM wise, because the cost of
                                   * the large number of page protect operations would be higher
                                   * than the value of doing the operation.
                                   */
                                  vm_page_protect(m, VM_PROT_NONE);
                                  vm_page_deactivate(m);
                          } else {
                                  m->act_count -= min(m->act_count, ACT_DECLINE);
                                  s = splvm();
                                  TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
                                  TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
                                  splx(s);
                          }
                  }
  
                  m = next;
          }
  }
  
  static int
  vm_pageout_free_page_calc(count)
  vm_size_t count;
  {
          if (count < cnt.v_page_count)
                   return 0;
          /*
           * free_reserved needs to include enough for the largest swap pager
           * structures plus enough for any pv_entry structs when paging.
           */
          if (cnt.v_page_count > 1024)
                  cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
          else
                  cnt.v_free_min = 4;
          cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
                  cnt.v_interrupt_free_min;
          cnt.v_free_reserved = vm_pageout_page_count +
                  cnt.v_pageout_free_min + (count / 768) + PQ_L2_SIZE;
          cnt.v_free_min += cnt.v_free_reserved;
          return 1;
  }
  
  
  /*
   *      vm_pageout is the high level pageout daemon.
   */
  static void
  vm_pageout()
  {
          /*
           * Initialize some paging parameters.
           */
  
          cnt.v_interrupt_free_min = 2;
          if (cnt.v_page_count < 2000)
                  vm_pageout_page_count = 8;
  
          vm_pageout_free_page_calc(cnt.v_page_count);
          /*
           * free_reserved needs to include enough for the largest swap pager
           * structures plus enough for any pv_entry structs when paging.
           */
          if (cnt.v_free_count > 6144)
                  cnt.v_free_target = 3 * cnt.v_free_min + cnt.v_free_reserved;
          else
                  cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
  
          if (cnt.v_free_count > 2048) {
                  cnt.v_cache_min = cnt.v_free_target;
                  cnt.v_cache_max = 2 * cnt.v_cache_min;
                  cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
          } else {
                  cnt.v_cache_min = 0;
                  cnt.v_cache_max = 0;
                  cnt.v_inactive_target = cnt.v_free_count / 4;
          }
          if (cnt.v_inactive_target > cnt.v_free_count / 3)
                  cnt.v_inactive_target = cnt.v_free_count / 3;
  
          /* XXX does not really belong here */
          if (vm_page_max_wired == 0)
                  vm_page_max_wired = cnt.v_free_count / 3;
  
          if (vm_pageout_stats_max == 0)
                  vm_pageout_stats_max = cnt.v_free_target;
  
          /*
           * Set interval in seconds for stats scan.
           */
          if (vm_pageout_stats_interval == 0)
                  vm_pageout_stats_interval = 5;
          if (vm_pageout_full_stats_interval == 0)
                  vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
          
  
          /*
           * Set maximum free per pass
           */
          if (vm_pageout_stats_free_max == 0)
                  vm_pageout_stats_free_max = 5;
  
          max_page_launder = (cnt.v_page_count > 1800 ? 32 : 16);
  
          swap_pager_swap_init();
          /*
           * The pageout daemon is never done, so loop forever.
           */
          while (TRUE) {
                  int error;
                  int s = splvm();
                  if (!vm_pages_needed ||
                          ((cnt.v_free_count + cnt.v_cache_count) > cnt.v_free_min)) {
                          vm_pages_needed = 0;
                          error = tsleep(&vm_pages_needed,
                                  PVM, "psleep", vm_pageout_stats_interval * hz);
                          if (error && !vm_pages_needed) {
                                  splx(s);
                                  vm_pageout_page_stats();
                                  continue;
                          }
                  } else if (vm_pages_needed) {
                          vm_pages_needed = 0;
                          tsleep(&vm_pages_needed, PVM, "psleep", hz/2);
                  }
  
                  if (vm_pages_needed)
                          cnt.v_pdwakeups++;
                  vm_pages_needed = 0;
                  splx(s);
                  vm_pager_sync();
                  vm_pageout_scan();
                  vm_pageout_deficit = 0;
                  vm_pager_sync();
                  wakeup(&cnt.v_free_count);
          }
  }
  
  void
  pagedaemon_wakeup()
  {
          if (!vm_pages_needed && curproc != pageproc) {
                  vm_pages_needed++;
                  wakeup(&vm_pages_needed);
          }
  }
  
  #if !defined(NO_SWAPPING)
  static void
  vm_req_vmdaemon()
  {
          static int lastrun = 0;
  
          if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
                  wakeup(&vm_daemon_needed);
                  lastrun = ticks;
          }
  }
  
  static void
  vm_daemon()
  {
          struct proc *p;
  
          while (TRUE) {
                  tsleep(&vm_daemon_needed, PPAUSE, "psleep", 0);
                  if (vm_pageout_req_swapout) {
                          swapout_procs(vm_pageout_req_swapout);
                          vm_pageout_req_swapout = 0;
                  }
                  /*
                   * scan the processes for exceeding their rlimits or if
                   * process is swapped out -- deactivate pages
                   */
  
                  for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
                          vm_pindex_t limit, size;
  
                          /*
                           * if this is a system process or if we have already
                           * looked at this process, skip it.
                           */
                          if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
                                  continue;
                          }
                          /*
                           * if the process is in a non-running type state,
                           * don't touch it.
                           */
                          if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
                                  continue;
                          }
                          /*
                           * get a limit
                           */
                          limit = OFF_TO_IDX(
                              qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
                                  p->p_rlimit[RLIMIT_RSS].rlim_max));
  
                          /*
                           * let processes that are swapped out really be
                           * swapped out set the limit to nothing (will force a
                           * swap-out.)
                           */
                          if ((p->p_flag & P_INMEM) == 0)
                                  limit = 0;      /* XXX */
  
                          size = p->p_vmspace->vm_pmap.pm_stats.resident_count;
                          if (limit >= 0 && size >= limit) {
                                  vm_pageout_map_deactivate_pages(
                                      &p->p_vmspace->vm_map, limit);
                          }
                  }
          }
  }
  #endif

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