The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_pageout.c

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    1 /*
    2  * Copyright (c) 1991 Regents of the University of California.
    3  * All rights reserved.
    4  * Copyright (c) 1994 John S. Dyson
    5  * All rights reserved.
    6  * Copyright (c) 1994 David Greenman
    7  * All rights reserved.
    8  *
    9  * This code is derived from software contributed to Berkeley by
   10  * The Mach Operating System project at Carnegie-Mellon University.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. All advertising materials mentioning features or use of this software
   21  *    must display the following acknowledgement:
   22  *      This product includes software developed by the University of
   23  *      California, Berkeley and its contributors.
   24  * 4. Neither the name of the University nor the names of its contributors
   25  *    may be used to endorse or promote products derived from this software
   26  *    without specific prior written permission.
   27  *
   28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   38  * SUCH DAMAGE.
   39  *
   40  *      from: @(#)vm_pageout.c  7.4 (Berkeley) 5/7/91
   41  *
   42  *
   43  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   44  * All rights reserved.
   45  *
   46  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   47  *
   48  * Permission to use, copy, modify and distribute this software and
   49  * its documentation is hereby granted, provided that both the copyright
   50  * notice and this permission notice appear in all copies of the
   51  * software, derivative works or modified versions, and any portions
   52  * thereof, and that both notices appear in supporting documentation.
   53  *
   54  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   55  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   56  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   57  *
   58  * Carnegie Mellon requests users of this software to return to
   59  *
   60  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   61  *  School of Computer Science
   62  *  Carnegie Mellon University
   63  *  Pittsburgh PA 15213-3890
   64  *
   65  * any improvements or extensions that they make and grant Carnegie the
   66  * rights to redistribute these changes.
   67  *
   68  * $FreeBSD: releng/5.1/sys/vm/vm_pageout.c 115146 2003-05-19 00:51:07Z das $
   69  */
   70 
   71 /*
   72  *      The proverbial page-out daemon.
   73  */
   74 
   75 #include "opt_vm.h"
   76 #include <sys/param.h>
   77 #include <sys/systm.h>
   78 #include <sys/kernel.h>
   79 #include <sys/eventhandler.h>
   80 #include <sys/lock.h>
   81 #include <sys/mutex.h>
   82 #include <sys/proc.h>
   83 #include <sys/kthread.h>
   84 #include <sys/ktr.h>
   85 #include <sys/resourcevar.h>
   86 #include <sys/sched.h>
   87 #include <sys/signalvar.h>
   88 #include <sys/vnode.h>
   89 #include <sys/vmmeter.h>
   90 #include <sys/sx.h>
   91 #include <sys/sysctl.h>
   92 
   93 #include <vm/vm.h>
   94 #include <vm/vm_param.h>
   95 #include <vm/vm_object.h>
   96 #include <vm/vm_page.h>
   97 #include <vm/vm_map.h>
   98 #include <vm/vm_pageout.h>
   99 #include <vm/vm_pager.h>
  100 #include <vm/swap_pager.h>
  101 #include <vm/vm_extern.h>
  102 #include <vm/uma.h>
  103 
  104 #include <machine/mutex.h>
  105 
  106 /*
  107  * System initialization
  108  */
  109 
  110 /* the kernel process "vm_pageout"*/
  111 static void vm_pageout(void);
  112 static int vm_pageout_clean(vm_page_t);
  113 static void vm_pageout_page_free(vm_page_t);
  114 static void vm_pageout_pmap_collect(void);
  115 static void vm_pageout_scan(int pass);
  116 static int vm_pageout_free_page_calc(vm_size_t count);
  117 struct proc *pageproc;
  118 
  119 static struct kproc_desc page_kp = {
  120         "pagedaemon",
  121         vm_pageout,
  122         &pageproc
  123 };
  124 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
  125 
  126 #if !defined(NO_SWAPPING)
  127 /* the kernel process "vm_daemon"*/
  128 static void vm_daemon(void);
  129 static struct   proc *vmproc;
  130 
  131 static struct kproc_desc vm_kp = {
  132         "vmdaemon",
  133         vm_daemon,
  134         &vmproc
  135 };
  136 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
  137 #endif
  138 
  139 
  140 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
  141 int vm_pageout_deficit;         /* Estimated number of pages deficit */
  142 int vm_pageout_pages_needed;    /* flag saying that the pageout daemon needs pages */
  143 
  144 #if !defined(NO_SWAPPING)
  145 static int vm_pageout_req_swapout;      /* XXX */
  146 static int vm_daemon_needed;
  147 #endif
  148 static int vm_max_launder = 32;
  149 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
  150 static int vm_pageout_full_stats_interval = 0;
  151 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0;
  152 static int defer_swap_pageouts=0;
  153 static int disable_swap_pageouts=0;
  154 
  155 #if defined(NO_SWAPPING)
  156 static int vm_swap_enabled=0;
  157 static int vm_swap_idle_enabled=0;
  158 #else
  159 static int vm_swap_enabled=1;
  160 static int vm_swap_idle_enabled=0;
  161 #endif
  162 
  163 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
  164         CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
  165 
  166 SYSCTL_INT(_vm, OID_AUTO, max_launder,
  167         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
  168 
  169 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
  170         CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
  171 
  172 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
  173         CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
  174 
  175 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
  176         CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
  177 
  178 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
  179         CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
  180 
  181 #if defined(NO_SWAPPING)
  182 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  183         CTLFLAG_RD, &vm_swap_enabled, 0, "");
  184 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  185         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
  186 #else
  187 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  188         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
  189 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  190         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
  191 #endif
  192 
  193 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
  194         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
  195 
  196 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
  197         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
  198 
  199 static int pageout_lock_miss;
  200 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
  201         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
  202 
  203 #define VM_PAGEOUT_PAGE_COUNT 16
  204 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
  205 
  206 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
  207 
  208 #if !defined(NO_SWAPPING)
  209 typedef void freeer_fcn_t(vm_map_t, vm_object_t, vm_pindex_t);
  210 static void vm_pageout_map_deactivate_pages(vm_map_t, vm_pindex_t);
  211 static freeer_fcn_t vm_pageout_object_deactivate_pages;
  212 static void vm_req_vmdaemon(void);
  213 #endif
  214 static void vm_pageout_page_stats(void);
  215 
  216 /*
  217  * vm_pageout_clean:
  218  *
  219  * Clean the page and remove it from the laundry.
  220  * 
  221  * We set the busy bit to cause potential page faults on this page to
  222  * block.  Note the careful timing, however, the busy bit isn't set till
  223  * late and we cannot do anything that will mess with the page.
  224  */
  225 static int
  226 vm_pageout_clean(m)
  227         vm_page_t m;
  228 {
  229         vm_object_t object;
  230         vm_page_t mc[2*vm_pageout_page_count];
  231         int pageout_count;
  232         int ib, is, page_base;
  233         vm_pindex_t pindex = m->pindex;
  234 
  235         mtx_assert(&vm_page_queue_mtx, MA_OWNED);
  236 
  237         object = m->object;
  238 
  239         /*
  240          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
  241          * with the new swapper, but we could have serious problems paging
  242          * out other object types if there is insufficient memory.  
  243          *
  244          * Unfortunately, checking free memory here is far too late, so the
  245          * check has been moved up a procedural level.
  246          */
  247 
  248         /*
  249          * Don't mess with the page if it's busy, held, or special
  250          */
  251         if ((m->hold_count != 0) ||
  252             ((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) {
  253                 return 0;
  254         }
  255 
  256         mc[vm_pageout_page_count] = m;
  257         pageout_count = 1;
  258         page_base = vm_pageout_page_count;
  259         ib = 1;
  260         is = 1;
  261 
  262         /*
  263          * Scan object for clusterable pages.
  264          *
  265          * We can cluster ONLY if: ->> the page is NOT
  266          * clean, wired, busy, held, or mapped into a
  267          * buffer, and one of the following:
  268          * 1) The page is inactive, or a seldom used
  269          *    active page.
  270          * -or-
  271          * 2) we force the issue.
  272          *
  273          * During heavy mmap/modification loads the pageout
  274          * daemon can really fragment the underlying file
  275          * due to flushing pages out of order and not trying
  276          * align the clusters (which leave sporatic out-of-order
  277          * holes).  To solve this problem we do the reverse scan
  278          * first and attempt to align our cluster, then do a 
  279          * forward scan if room remains.
  280          */
  281 more:
  282         while (ib && pageout_count < vm_pageout_page_count) {
  283                 vm_page_t p;
  284 
  285                 if (ib > pindex) {
  286                         ib = 0;
  287                         break;
  288                 }
  289 
  290                 if ((p = vm_page_lookup(object, pindex - ib)) == NULL) {
  291                         ib = 0;
  292                         break;
  293                 }
  294                 if (((p->queue - p->pc) == PQ_CACHE) ||
  295                     (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
  296                         ib = 0;
  297                         break;
  298                 }
  299                 vm_page_test_dirty(p);
  300                 if ((p->dirty & p->valid) == 0 ||
  301                     p->queue != PQ_INACTIVE ||
  302                     p->wire_count != 0 ||       /* may be held by buf cache */
  303                     p->hold_count != 0) {       /* may be undergoing I/O */
  304                         ib = 0;
  305                         break;
  306                 }
  307                 mc[--page_base] = p;
  308                 ++pageout_count;
  309                 ++ib;
  310                 /*
  311                  * alignment boundry, stop here and switch directions.  Do
  312                  * not clear ib.
  313                  */
  314                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
  315                         break;
  316         }
  317 
  318         while (pageout_count < vm_pageout_page_count && 
  319             pindex + is < object->size) {
  320                 vm_page_t p;
  321 
  322                 if ((p = vm_page_lookup(object, pindex + is)) == NULL)
  323                         break;
  324                 if (((p->queue - p->pc) == PQ_CACHE) ||
  325                     (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
  326                         break;
  327                 }
  328                 vm_page_test_dirty(p);
  329                 if ((p->dirty & p->valid) == 0 ||
  330                     p->queue != PQ_INACTIVE ||
  331                     p->wire_count != 0 ||       /* may be held by buf cache */
  332                     p->hold_count != 0) {       /* may be undergoing I/O */
  333                         break;
  334                 }
  335                 mc[page_base + pageout_count] = p;
  336                 ++pageout_count;
  337                 ++is;
  338         }
  339 
  340         /*
  341          * If we exhausted our forward scan, continue with the reverse scan
  342          * when possible, even past a page boundry.  This catches boundry
  343          * conditions.
  344          */
  345         if (ib && pageout_count < vm_pageout_page_count)
  346                 goto more;
  347 
  348         /*
  349          * we allow reads during pageouts...
  350          */
  351         return vm_pageout_flush(&mc[page_base], pageout_count, 0, FALSE);
  352 }
  353 
  354 /*
  355  * vm_pageout_flush() - launder the given pages
  356  *
  357  *      The given pages are laundered.  Note that we setup for the start of
  358  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
  359  *      reference count all in here rather then in the parent.  If we want
  360  *      the parent to do more sophisticated things we may have to change
  361  *      the ordering.
  362  */
  363 int
  364 vm_pageout_flush(mc, count, flags, is_object_locked)
  365         vm_page_t *mc;
  366         int count;
  367         int flags;
  368         int is_object_locked;
  369 {
  370         vm_object_t object;
  371         int pageout_status[count];
  372         int numpagedout = 0;
  373         int i;
  374 
  375         mtx_assert(&vm_page_queue_mtx, MA_OWNED);
  376         /*
  377          * Initiate I/O.  Bump the vm_page_t->busy counter and
  378          * mark the pages read-only.
  379          *
  380          * We do not have to fixup the clean/dirty bits here... we can
  381          * allow the pager to do it after the I/O completes.
  382          *
  383          * NOTE! mc[i]->dirty may be partial or fragmented due to an
  384          * edge case with file fragments.
  385          */
  386         for (i = 0; i < count; i++) {
  387                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, ("vm_pageout_flush page %p index %d/%d: partially invalid page", mc[i], i, count));
  388                 vm_page_io_start(mc[i]);
  389                 pmap_page_protect(mc[i], VM_PROT_READ);
  390         }
  391         object = mc[0]->object;
  392         vm_page_unlock_queues();
  393         if (!is_object_locked)
  394                 VM_OBJECT_LOCK(object);
  395         vm_object_pip_add(object, count);
  396         VM_OBJECT_UNLOCK(object);
  397 
  398         vm_pager_put_pages(object, mc, count,
  399             (flags | ((object == kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
  400             pageout_status);
  401 
  402         VM_OBJECT_LOCK(object);
  403         vm_page_lock_queues();
  404         for (i = 0; i < count; i++) {
  405                 vm_page_t mt = mc[i];
  406 
  407                 switch (pageout_status[i]) {
  408                 case VM_PAGER_OK:
  409                 case VM_PAGER_PEND:
  410                         numpagedout++;
  411                         break;
  412                 case VM_PAGER_BAD:
  413                         /*
  414                          * Page outside of range of object. Right now we
  415                          * essentially lose the changes by pretending it
  416                          * worked.
  417                          */
  418                         pmap_clear_modify(mt);
  419                         vm_page_undirty(mt);
  420                         break;
  421                 case VM_PAGER_ERROR:
  422                 case VM_PAGER_FAIL:
  423                         /*
  424                          * If page couldn't be paged out, then reactivate the
  425                          * page so it doesn't clog the inactive list.  (We
  426                          * will try paging out it again later).
  427                          */
  428                         vm_page_activate(mt);
  429                         break;
  430                 case VM_PAGER_AGAIN:
  431                         break;
  432                 }
  433 
  434                 /*
  435                  * If the operation is still going, leave the page busy to
  436                  * block all other accesses. Also, leave the paging in
  437                  * progress indicator set so that we don't attempt an object
  438                  * collapse.
  439                  */
  440                 if (pageout_status[i] != VM_PAGER_PEND) {
  441                         vm_object_pip_wakeup(object);
  442                         vm_page_io_finish(mt);
  443                         if (!vm_page_count_severe() || !vm_page_try_to_cache(mt))
  444                                 pmap_page_protect(mt, VM_PROT_READ);
  445                 }
  446         }
  447         if (!is_object_locked)
  448                 VM_OBJECT_UNLOCK(object);
  449         return numpagedout;
  450 }
  451 
  452 #if !defined(NO_SWAPPING)
  453 /*
  454  *      vm_pageout_object_deactivate_pages
  455  *
  456  *      deactivate enough pages to satisfy the inactive target
  457  *      requirements or if vm_page_proc_limit is set, then
  458  *      deactivate all of the pages in the object and its
  459  *      backing_objects.
  460  *
  461  *      The object and map must be locked.
  462  */
  463 static void
  464 vm_pageout_object_deactivate_pages(map, object, desired)
  465         vm_map_t map;
  466         vm_object_t object;
  467         vm_pindex_t desired;
  468 {
  469         vm_page_t p, next;
  470         int actcount, rcount, remove_mode;
  471 
  472         GIANT_REQUIRED;
  473         if (object->type == OBJT_DEVICE || object->type == OBJT_PHYS)
  474                 return;
  475 
  476         while (object) {
  477                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
  478                         return;
  479                 if (object->paging_in_progress)
  480                         return;
  481 
  482                 remove_mode = 0;
  483                 if (object->shadow_count > 1)
  484                         remove_mode = 1;
  485                 /*
  486                  * scan the objects entire memory queue
  487                  */
  488                 rcount = object->resident_page_count;
  489                 p = TAILQ_FIRST(&object->memq);
  490                 vm_page_lock_queues();
  491                 while (p && (rcount-- > 0)) {
  492                         if (pmap_resident_count(map->pmap) <= desired) {
  493                                 vm_page_unlock_queues();
  494                                 return;
  495                         }
  496                         next = TAILQ_NEXT(p, listq);
  497                         cnt.v_pdpages++;
  498                         if (p->wire_count != 0 ||
  499                             p->hold_count != 0 ||
  500                             p->busy != 0 ||
  501                             (p->flags & (PG_BUSY|PG_UNMANAGED)) ||
  502                             !pmap_page_exists_quick(vm_map_pmap(map), p)) {
  503                                 p = next;
  504                                 continue;
  505                         }
  506                         actcount = pmap_ts_referenced(p);
  507                         if (actcount) {
  508                                 vm_page_flag_set(p, PG_REFERENCED);
  509                         } else if (p->flags & PG_REFERENCED) {
  510                                 actcount = 1;
  511                         }
  512                         if ((p->queue != PQ_ACTIVE) &&
  513                                 (p->flags & PG_REFERENCED)) {
  514                                 vm_page_activate(p);
  515                                 p->act_count += actcount;
  516                                 vm_page_flag_clear(p, PG_REFERENCED);
  517                         } else if (p->queue == PQ_ACTIVE) {
  518                                 if ((p->flags & PG_REFERENCED) == 0) {
  519                                         p->act_count -= min(p->act_count, ACT_DECLINE);
  520                                         if (!remove_mode && (vm_pageout_algorithm || (p->act_count == 0))) {
  521                                                 pmap_remove_all(p);
  522                                                 vm_page_deactivate(p);
  523                                         } else {
  524                                                 vm_pageq_requeue(p);
  525                                         }
  526                                 } else {
  527                                         vm_page_activate(p);
  528                                         vm_page_flag_clear(p, PG_REFERENCED);
  529                                         if (p->act_count < (ACT_MAX - ACT_ADVANCE))
  530                                                 p->act_count += ACT_ADVANCE;
  531                                         vm_pageq_requeue(p);
  532                                 }
  533                         } else if (p->queue == PQ_INACTIVE) {
  534                                 pmap_remove_all(p);
  535                         }
  536                         p = next;
  537                 }
  538                 vm_page_unlock_queues();
  539                 object = object->backing_object;
  540         }
  541 }
  542 
  543 /*
  544  * deactivate some number of pages in a map, try to do it fairly, but
  545  * that is really hard to do.
  546  */
  547 static void
  548 vm_pageout_map_deactivate_pages(map, desired)
  549         vm_map_t map;
  550         vm_pindex_t desired;
  551 {
  552         vm_map_entry_t tmpe;
  553         vm_object_t obj, bigobj;
  554         int nothingwired;
  555 
  556         GIANT_REQUIRED;
  557         if (!vm_map_trylock(map))
  558                 return;
  559 
  560         bigobj = NULL;
  561         nothingwired = TRUE;
  562 
  563         /*
  564          * first, search out the biggest object, and try to free pages from
  565          * that.
  566          */
  567         tmpe = map->header.next;
  568         while (tmpe != &map->header) {
  569                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  570                         obj = tmpe->object.vm_object;
  571                         if ((obj != NULL) && (obj->shadow_count <= 1) &&
  572                                 ((bigobj == NULL) ||
  573                                  (bigobj->resident_page_count < obj->resident_page_count))) {
  574                                 bigobj = obj;
  575                         }
  576                 }
  577                 if (tmpe->wired_count > 0)
  578                         nothingwired = FALSE;
  579                 tmpe = tmpe->next;
  580         }
  581 
  582         if (bigobj)
  583                 vm_pageout_object_deactivate_pages(map, bigobj, desired);
  584 
  585         /*
  586          * Next, hunt around for other pages to deactivate.  We actually
  587          * do this search sort of wrong -- .text first is not the best idea.
  588          */
  589         tmpe = map->header.next;
  590         while (tmpe != &map->header) {
  591                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
  592                         break;
  593                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  594                         obj = tmpe->object.vm_object;
  595                         if (obj)
  596                                 vm_pageout_object_deactivate_pages(map, obj, desired);
  597                 }
  598                 tmpe = tmpe->next;
  599         }
  600 
  601         /*
  602          * Remove all mappings if a process is swapped out, this will free page
  603          * table pages.
  604          */
  605         if (desired == 0 && nothingwired) {
  606                 vm_page_lock_queues();
  607                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
  608                     vm_map_max(map));
  609                 vm_page_unlock_queues();
  610         }
  611         vm_map_unlock(map);
  612 }
  613 #endif          /* !defined(NO_SWAPPING) */
  614 
  615 /*
  616  * Warning! The page queue lock is released and reacquired.
  617  */
  618 static void
  619 vm_pageout_page_free(vm_page_t m)
  620 {
  621         vm_object_t object = m->object;
  622 
  623         mtx_assert(&vm_page_queue_mtx, MA_OWNED);
  624         vm_page_busy(m);
  625         vm_page_unlock_queues();
  626         /*
  627          * Avoid a lock order reversal.  The page must be busy.
  628          */
  629         VM_OBJECT_LOCK(object);
  630         vm_page_lock_queues();
  631         pmap_remove_all(m);
  632         vm_page_free(m);
  633         VM_OBJECT_UNLOCK(object);
  634         cnt.v_dfree++;
  635 }
  636 
  637 /*
  638  * This routine is very drastic, but can save the system
  639  * in a pinch.
  640  */
  641 static void
  642 vm_pageout_pmap_collect(void)
  643 {
  644         int i;
  645         vm_page_t m;
  646         static int warningdone;
  647 
  648         if (pmap_pagedaemon_waken == 0)
  649                 return;
  650         if (warningdone < 5) {
  651                 printf("collecting pv entries -- suggest increasing PMAP_SHPGPERPROC\n");
  652                 warningdone++;
  653         }
  654         vm_page_lock_queues();
  655         for (i = 0; i < vm_page_array_size; i++) {
  656                 m = &vm_page_array[i];
  657                 if (m->wire_count || m->hold_count || m->busy ||
  658                     (m->flags & (PG_BUSY | PG_UNMANAGED)))
  659                         continue;
  660                 pmap_remove_all(m);
  661         }
  662         vm_page_unlock_queues();
  663         pmap_pagedaemon_waken = 0;
  664 }
  665         
  666 /*
  667  *      vm_pageout_scan does the dirty work for the pageout daemon.
  668  */
  669 static void
  670 vm_pageout_scan(int pass)
  671 {
  672         vm_page_t m, next;
  673         struct vm_page marker;
  674         int save_page_shortage;
  675         int save_inactive_count;
  676         int page_shortage, maxscan, pcount;
  677         int addl_page_shortage, addl_page_shortage_init;
  678         struct proc *p, *bigproc;
  679         vm_offset_t size, bigsize;
  680         vm_object_t object;
  681         int actcount;
  682         int vnodes_skipped = 0;
  683         int maxlaunder;
  684         int s;
  685         struct thread *td;
  686 
  687         GIANT_REQUIRED;
  688         /*
  689          * Decrease registered cache sizes.
  690          */
  691         EVENTHANDLER_INVOKE(vm_lowmem, 0);
  692         /*
  693          * We do this explicitly after the caches have been drained above.
  694          */
  695         uma_reclaim();
  696         /*
  697          * Do whatever cleanup that the pmap code can.
  698          */
  699         vm_pageout_pmap_collect();
  700 
  701         addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
  702 
  703         /*
  704          * Calculate the number of pages we want to either free or move
  705          * to the cache.
  706          */
  707         page_shortage = vm_paging_target() + addl_page_shortage_init;
  708         save_page_shortage = page_shortage;
  709         save_inactive_count = cnt.v_inactive_count;
  710 
  711         /*
  712          * Initialize our marker
  713          */
  714         bzero(&marker, sizeof(marker));
  715         marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
  716         marker.queue = PQ_INACTIVE;
  717         marker.wire_count = 1;
  718 
  719         /*
  720          * Start scanning the inactive queue for pages we can move to the
  721          * cache or free.  The scan will stop when the target is reached or
  722          * we have scanned the entire inactive queue.  Note that m->act_count
  723          * is not used to form decisions for the inactive queue, only for the
  724          * active queue.
  725          *
  726          * maxlaunder limits the number of dirty pages we flush per scan.
  727          * For most systems a smaller value (16 or 32) is more robust under
  728          * extreme memory and disk pressure because any unnecessary writes
  729          * to disk can result in extreme performance degredation.  However,
  730          * systems with excessive dirty pages (especially when MAP_NOSYNC is
  731          * used) will die horribly with limited laundering.  If the pageout
  732          * daemon cannot clean enough pages in the first pass, we let it go
  733          * all out in succeeding passes.
  734          */
  735         if ((maxlaunder = vm_max_launder) <= 1)
  736                 maxlaunder = 1;
  737         if (pass)
  738                 maxlaunder = 10000;
  739 rescan0:
  740         addl_page_shortage = addl_page_shortage_init;
  741         maxscan = cnt.v_inactive_count;
  742 
  743         for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
  744              m != NULL && maxscan-- > 0 && page_shortage > 0;
  745              m = next) {
  746 
  747                 cnt.v_pdpages++;
  748 
  749                 if (m->queue != PQ_INACTIVE) {
  750                         goto rescan0;
  751                 }
  752 
  753                 next = TAILQ_NEXT(m, pageq);
  754 
  755                 /*
  756                  * skip marker pages
  757                  */
  758                 if (m->flags & PG_MARKER)
  759                         continue;
  760 
  761                 /*
  762                  * A held page may be undergoing I/O, so skip it.
  763                  */
  764                 if (m->hold_count) {
  765                         vm_pageq_requeue(m);
  766                         addl_page_shortage++;
  767                         continue;
  768                 }
  769                 /*
  770                  * Don't mess with busy pages, keep in the front of the
  771                  * queue, most likely are being paged out.
  772                  */
  773                 if (m->busy || (m->flags & PG_BUSY)) {
  774                         addl_page_shortage++;
  775                         continue;
  776                 }
  777 
  778                 vm_page_lock_queues();
  779                 /*
  780                  * If the object is not being used, we ignore previous 
  781                  * references.
  782                  */
  783                 if (m->object->ref_count == 0) {
  784                         vm_page_flag_clear(m, PG_REFERENCED);
  785                         pmap_clear_reference(m);
  786 
  787                 /*
  788                  * Otherwise, if the page has been referenced while in the 
  789                  * inactive queue, we bump the "activation count" upwards, 
  790                  * making it less likely that the page will be added back to 
  791                  * the inactive queue prematurely again.  Here we check the 
  792                  * page tables (or emulated bits, if any), given the upper 
  793                  * level VM system not knowing anything about existing 
  794                  * references.
  795                  */
  796                 } else if (((m->flags & PG_REFERENCED) == 0) &&
  797                         (actcount = pmap_ts_referenced(m))) {
  798                         vm_page_activate(m);
  799                         vm_page_unlock_queues();
  800                         m->act_count += (actcount + ACT_ADVANCE);
  801                         continue;
  802                 }
  803 
  804                 /*
  805                  * If the upper level VM system knows about any page 
  806                  * references, we activate the page.  We also set the 
  807                  * "activation count" higher than normal so that we will less 
  808                  * likely place pages back onto the inactive queue again.
  809                  */
  810                 if ((m->flags & PG_REFERENCED) != 0) {
  811                         vm_page_flag_clear(m, PG_REFERENCED);
  812                         actcount = pmap_ts_referenced(m);
  813                         vm_page_activate(m);
  814                         vm_page_unlock_queues();
  815                         m->act_count += (actcount + ACT_ADVANCE + 1);
  816                         continue;
  817                 }
  818 
  819                 /*
  820                  * If the upper level VM system doesn't know anything about 
  821                  * the page being dirty, we have to check for it again.  As 
  822                  * far as the VM code knows, any partially dirty pages are 
  823                  * fully dirty.
  824                  */
  825                 if (m->dirty == 0) {
  826                         vm_page_test_dirty(m);
  827                 } else {
  828                         vm_page_dirty(m);
  829                 }
  830                 vm_page_unlock_queues();
  831 
  832                 /*
  833                  * Invalid pages can be easily freed
  834                  */
  835                 if (m->valid == 0) {
  836                         vm_page_lock_queues();
  837                         vm_pageout_page_free(m);
  838                         vm_page_unlock_queues();
  839                         --page_shortage;
  840 
  841                 /*
  842                  * Clean pages can be placed onto the cache queue.  This
  843                  * effectively frees them.
  844                  */
  845                 } else if (m->dirty == 0) {
  846                         vm_page_lock_queues();
  847                         vm_page_cache(m);
  848                         vm_page_unlock_queues();
  849                         --page_shortage;
  850                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
  851                         /*
  852                          * Dirty pages need to be paged out, but flushing
  853                          * a page is extremely expensive verses freeing
  854                          * a clean page.  Rather then artificially limiting
  855                          * the number of pages we can flush, we instead give
  856                          * dirty pages extra priority on the inactive queue
  857                          * by forcing them to be cycled through the queue
  858                          * twice before being flushed, after which the
  859                          * (now clean) page will cycle through once more
  860                          * before being freed.  This significantly extends
  861                          * the thrash point for a heavily loaded machine.
  862                          */
  863                         vm_page_lock_queues();
  864                         vm_page_flag_set(m, PG_WINATCFLS);
  865                         vm_pageq_requeue(m);
  866                         vm_page_unlock_queues();
  867                 } else if (maxlaunder > 0) {
  868                         /*
  869                          * We always want to try to flush some dirty pages if
  870                          * we encounter them, to keep the system stable.
  871                          * Normally this number is small, but under extreme
  872                          * pressure where there are insufficient clean pages
  873                          * on the inactive queue, we may have to go all out.
  874                          */
  875                         int swap_pageouts_ok;
  876                         struct vnode *vp = NULL;
  877                         struct mount *mp;
  878 
  879                         object = m->object;
  880 
  881                         if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
  882                                 swap_pageouts_ok = 1;
  883                         } else {
  884                                 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
  885                                 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
  886                                 vm_page_count_min());
  887                                                                                 
  888                         }
  889 
  890                         /*
  891                          * We don't bother paging objects that are "dead".  
  892                          * Those objects are in a "rundown" state.
  893                          */
  894                         if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
  895                                 vm_pageq_requeue(m);
  896                                 continue;
  897                         }
  898 
  899                         /*
  900                          * The object is already known NOT to be dead.   It
  901                          * is possible for the vget() to block the whole
  902                          * pageout daemon, but the new low-memory handling
  903                          * code should prevent it.
  904                          *
  905                          * The previous code skipped locked vnodes and, worse,
  906                          * reordered pages in the queue.  This results in
  907                          * completely non-deterministic operation and, on a
  908                          * busy system, can lead to extremely non-optimal
  909                          * pageouts.  For example, it can cause clean pages
  910                          * to be freed and dirty pages to be moved to the end
  911                          * of the queue.  Since dirty pages are also moved to
  912                          * the end of the queue once-cleaned, this gives
  913                          * way too large a weighting to defering the freeing
  914                          * of dirty pages.
  915                          *
  916                          * We can't wait forever for the vnode lock, we might
  917                          * deadlock due to a vn_read() getting stuck in
  918                          * vm_wait while holding this vnode.  We skip the 
  919                          * vnode if we can't get it in a reasonable amount
  920                          * of time.
  921                          */
  922                         if (object->type == OBJT_VNODE) {
  923                                 vp = object->handle;
  924 
  925                                 mp = NULL;
  926                                 if (vp->v_type == VREG)
  927                                         vn_start_write(vp, &mp, V_NOWAIT);
  928                                 if (vget(vp, LK_EXCLUSIVE|LK_TIMELOCK, curthread)) {
  929                                         ++pageout_lock_miss;
  930                                         vn_finished_write(mp);
  931                                         if (object->flags & OBJ_MIGHTBEDIRTY)
  932                                                 vnodes_skipped++;
  933                                         continue;
  934                                 }
  935 
  936                                 /*
  937                                  * The page might have been moved to another
  938                                  * queue during potential blocking in vget()
  939                                  * above.  The page might have been freed and
  940                                  * reused for another vnode.  The object might
  941                                  * have been reused for another vnode.
  942                                  */
  943                                 if (m->queue != PQ_INACTIVE ||
  944                                     m->object != object ||
  945                                     object->handle != vp) {
  946                                         if (object->flags & OBJ_MIGHTBEDIRTY)
  947                                                 vnodes_skipped++;
  948                                         vput(vp);
  949                                         vn_finished_write(mp);
  950                                         continue;
  951                                 }
  952         
  953                                 /*
  954                                  * The page may have been busied during the
  955                                  * blocking in vput();  We don't move the
  956                                  * page back onto the end of the queue so that
  957                                  * statistics are more correct if we don't.
  958                                  */
  959                                 if (m->busy || (m->flags & PG_BUSY)) {
  960                                         vput(vp);
  961                                         vn_finished_write(mp);
  962                                         continue;
  963                                 }
  964 
  965                                 /*
  966                                  * If the page has become held it might
  967                                  * be undergoing I/O, so skip it
  968                                  */
  969                                 if (m->hold_count) {
  970                                         vm_pageq_requeue(m);
  971                                         if (object->flags & OBJ_MIGHTBEDIRTY)
  972                                                 vnodes_skipped++;
  973                                         vput(vp);
  974                                         vn_finished_write(mp);
  975                                         continue;
  976                                 }
  977                         }
  978 
  979                         /*
  980                          * If a page is dirty, then it is either being washed
  981                          * (but not yet cleaned) or it is still in the
  982                          * laundry.  If it is still in the laundry, then we
  983                          * start the cleaning operation. 
  984                          *
  985                          * This operation may cluster, invalidating the 'next'
  986                          * pointer.  To prevent an inordinate number of
  987                          * restarts we use our marker to remember our place.
  988                          *
  989                          * decrement page_shortage on success to account for
  990                          * the (future) cleaned page.  Otherwise we could wind
  991                          * up laundering or cleaning too many pages.
  992                          */
  993                         vm_page_lock_queues();
  994                         s = splvm();
  995                         TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq);
  996                         splx(s);
  997                         if (vm_pageout_clean(m) != 0) {
  998                                 --page_shortage;
  999                                 --maxlaunder;
 1000                         }
 1001                         s = splvm();
 1002                         next = TAILQ_NEXT(&marker, pageq);
 1003                         TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq);
 1004                         splx(s);
 1005                         vm_page_unlock_queues();
 1006                         if (vp) {
 1007                                 vput(vp);
 1008                                 vn_finished_write(mp);
 1009                         }
 1010                 }
 1011         }
 1012 
 1013         /*
 1014          * Compute the number of pages we want to try to move from the
 1015          * active queue to the inactive queue.
 1016          */
 1017         page_shortage = vm_paging_target() +
 1018                 cnt.v_inactive_target - cnt.v_inactive_count;
 1019         page_shortage += addl_page_shortage;
 1020 
 1021         vm_page_lock_queues();
 1022         /*
 1023          * Scan the active queue for things we can deactivate. We nominally
 1024          * track the per-page activity counter and use it to locate
 1025          * deactivation candidates.
 1026          */
 1027         pcount = cnt.v_active_count;
 1028         m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
 1029 
 1030         while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
 1031 
 1032                 /*
 1033                  * This is a consistency check, and should likely be a panic
 1034                  * or warning.
 1035                  */
 1036                 if (m->queue != PQ_ACTIVE) {
 1037                         break;
 1038                 }
 1039 
 1040                 next = TAILQ_NEXT(m, pageq);
 1041                 /*
 1042                  * Don't deactivate pages that are busy.
 1043                  */
 1044                 if ((m->busy != 0) ||
 1045                     (m->flags & PG_BUSY) ||
 1046                     (m->hold_count != 0)) {
 1047                         vm_pageq_requeue(m);
 1048                         m = next;
 1049                         continue;
 1050                 }
 1051 
 1052                 /*
 1053                  * The count for pagedaemon pages is done after checking the
 1054                  * page for eligibility...
 1055                  */
 1056                 cnt.v_pdpages++;
 1057 
 1058                 /*
 1059                  * Check to see "how much" the page has been used.
 1060                  */
 1061                 actcount = 0;
 1062                 if (m->object->ref_count != 0) {
 1063                         if (m->flags & PG_REFERENCED) {
 1064                                 actcount += 1;
 1065                         }
 1066                         actcount += pmap_ts_referenced(m);
 1067                         if (actcount) {
 1068                                 m->act_count += ACT_ADVANCE + actcount;
 1069                                 if (m->act_count > ACT_MAX)
 1070                                         m->act_count = ACT_MAX;
 1071                         }
 1072                 }
 1073 
 1074                 /*
 1075                  * Since we have "tested" this bit, we need to clear it now.
 1076                  */
 1077                 vm_page_flag_clear(m, PG_REFERENCED);
 1078 
 1079                 /*
 1080                  * Only if an object is currently being used, do we use the
 1081                  * page activation count stats.
 1082                  */
 1083                 if (actcount && (m->object->ref_count != 0)) {
 1084                         vm_pageq_requeue(m);
 1085                 } else {
 1086                         m->act_count -= min(m->act_count, ACT_DECLINE);
 1087                         if (vm_pageout_algorithm ||
 1088                             m->object->ref_count == 0 ||
 1089                             m->act_count == 0) {
 1090                                 page_shortage--;
 1091                                 if (m->object->ref_count == 0) {
 1092                                         pmap_remove_all(m);
 1093                                         if (m->dirty == 0)
 1094                                                 vm_page_cache(m);
 1095                                         else
 1096                                                 vm_page_deactivate(m);
 1097                                 } else {
 1098                                         vm_page_deactivate(m);
 1099                                 }
 1100                         } else {
 1101                                 vm_pageq_requeue(m);
 1102                         }
 1103                 }
 1104                 m = next;
 1105         }
 1106         s = splvm();
 1107 
 1108         /*
 1109          * We try to maintain some *really* free pages, this allows interrupt
 1110          * code to be guaranteed space.  Since both cache and free queues 
 1111          * are considered basically 'free', moving pages from cache to free
 1112          * does not effect other calculations.
 1113          */
 1114         while (cnt.v_free_count < cnt.v_free_reserved) {
 1115                 static int cache_rover = 0;
 1116                 m = vm_pageq_find(PQ_CACHE, cache_rover, FALSE);
 1117                 if (!m)
 1118                         break;
 1119                 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || 
 1120                     m->busy || 
 1121                     m->hold_count || 
 1122                     m->wire_count) {
 1123 #ifdef INVARIANTS
 1124                         printf("Warning: busy page %p found in cache\n", m);
 1125 #endif
 1126                         vm_page_deactivate(m);
 1127                         continue;
 1128                 }
 1129                 cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK;
 1130                 vm_pageout_page_free(m);
 1131         }
 1132         splx(s);
 1133         vm_page_unlock_queues();
 1134 #if !defined(NO_SWAPPING)
 1135         /*
 1136          * Idle process swapout -- run once per second.
 1137          */
 1138         if (vm_swap_idle_enabled) {
 1139                 static long lsec;
 1140                 if (time_second != lsec) {
 1141                         vm_pageout_req_swapout |= VM_SWAP_IDLE;
 1142                         vm_req_vmdaemon();
 1143                         lsec = time_second;
 1144                 }
 1145         }
 1146 #endif
 1147                 
 1148         /*
 1149          * If we didn't get enough free pages, and we have skipped a vnode
 1150          * in a writeable object, wakeup the sync daemon.  And kick swapout
 1151          * if we did not get enough free pages.
 1152          */
 1153         if (vm_paging_target() > 0) {
 1154                 if (vnodes_skipped && vm_page_count_min())
 1155                         (void) speedup_syncer();
 1156 #if !defined(NO_SWAPPING)
 1157                 if (vm_swap_enabled && vm_page_count_target()) {
 1158                         vm_req_vmdaemon();
 1159                         vm_pageout_req_swapout |= VM_SWAP_NORMAL;
 1160                 }
 1161 #endif
 1162         }
 1163 
 1164         /*
 1165          * If we are critically low on one of RAM or swap and low on
 1166          * the other, kill the largest process.  However, we avoid
 1167          * doing this on the first pass in order to give ourselves a
 1168          * chance to flush out dirty vnode-backed pages and to allow
 1169          * active pages to be moved to the inactive queue and reclaimed.
 1170          *
 1171          * We keep the process bigproc locked once we find it to keep anyone
 1172          * from messing with it; however, there is a possibility of
 1173          * deadlock if process B is bigproc and one of it's child processes
 1174          * attempts to propagate a signal to B while we are waiting for A's
 1175          * lock while walking this list.  To avoid this, we don't block on
 1176          * the process lock but just skip a process if it is already locked.
 1177          */
 1178         if (pass != 0 &&
 1179             ((vm_swap_size < 64 && vm_page_count_min()) ||
 1180              (swap_pager_full && vm_paging_target() > 0))) {
 1181                 bigproc = NULL;
 1182                 bigsize = 0;
 1183                 sx_slock(&allproc_lock);
 1184                 FOREACH_PROC_IN_SYSTEM(p) {
 1185                         int breakout;
 1186                         /*
 1187                          * If this process is already locked, skip it.
 1188                          */
 1189                         if (PROC_TRYLOCK(p) == 0)
 1190                                 continue;
 1191                         /*
 1192                          * If this is a system or protected process, skip it.
 1193                          */
 1194                         if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
 1195                             (p->p_flag & P_PROTECTED) ||
 1196                             ((p->p_pid < 48) && (vm_swap_size != 0))) {
 1197                                 PROC_UNLOCK(p);
 1198                                 continue;
 1199                         }
 1200                         /*
 1201                          * if the process is in a non-running type state,
 1202                          * don't touch it. Check all the threads individually.
 1203                          */
 1204                         mtx_lock_spin(&sched_lock);
 1205                         breakout = 0;
 1206                         FOREACH_THREAD_IN_PROC(p, td) {
 1207                                 if (!TD_ON_RUNQ(td) &&
 1208                                     !TD_IS_RUNNING(td) &&
 1209                                     !TD_IS_SLEEPING(td)) {
 1210                                         breakout = 1;
 1211                                         break;
 1212                                 }
 1213                         }
 1214                         if (breakout) {
 1215                                 mtx_unlock_spin(&sched_lock);
 1216                                 PROC_UNLOCK(p);
 1217                                 continue;
 1218                         }
 1219                         mtx_unlock_spin(&sched_lock);
 1220                         /*
 1221                          * get the process size
 1222                          */
 1223                         if (!vm_map_trylock_read(&p->p_vmspace->vm_map)) {
 1224                                 PROC_UNLOCK(p);
 1225                                 continue;
 1226                         }
 1227                         size = vmspace_swap_count(p->p_vmspace);
 1228                         vm_map_unlock_read(&p->p_vmspace->vm_map);
 1229                         size += vmspace_resident_count(p->p_vmspace);
 1230                         /*
 1231                          * if the this process is bigger than the biggest one
 1232                          * remember it.
 1233                          */
 1234                         if (size > bigsize) {
 1235                                 if (bigproc != NULL)
 1236                                         PROC_UNLOCK(bigproc);
 1237                                 bigproc = p;
 1238                                 bigsize = size;
 1239                         } else
 1240                                 PROC_UNLOCK(p);
 1241                 }
 1242                 sx_sunlock(&allproc_lock);
 1243                 if (bigproc != NULL) {
 1244                         struct ksegrp *kg;
 1245                         killproc(bigproc, "out of swap space");
 1246                         mtx_lock_spin(&sched_lock);
 1247                         FOREACH_KSEGRP_IN_PROC(bigproc, kg) {
 1248                                 sched_nice(kg, PRIO_MIN); /* XXXKSE ??? */
 1249                         }
 1250                         mtx_unlock_spin(&sched_lock);
 1251                         PROC_UNLOCK(bigproc);
 1252                         wakeup(&cnt.v_free_count);
 1253                 }
 1254         }
 1255 }
 1256 
 1257 /*
 1258  * This routine tries to maintain the pseudo LRU active queue,
 1259  * so that during long periods of time where there is no paging,
 1260  * that some statistic accumulation still occurs.  This code
 1261  * helps the situation where paging just starts to occur.
 1262  */
 1263 static void
 1264 vm_pageout_page_stats()
 1265 {
 1266         vm_page_t m,next;
 1267         int pcount,tpcount;             /* Number of pages to check */
 1268         static int fullintervalcount = 0;
 1269         int page_shortage;
 1270         int s0;
 1271 
 1272         page_shortage = 
 1273             (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
 1274             (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
 1275 
 1276         if (page_shortage <= 0)
 1277                 return;
 1278 
 1279         s0 = splvm();
 1280         vm_page_lock_queues();
 1281         pcount = cnt.v_active_count;
 1282         fullintervalcount += vm_pageout_stats_interval;
 1283         if (fullintervalcount < vm_pageout_full_stats_interval) {
 1284                 tpcount = (vm_pageout_stats_max * cnt.v_active_count) / cnt.v_page_count;
 1285                 if (pcount > tpcount)
 1286                         pcount = tpcount;
 1287         } else {
 1288                 fullintervalcount = 0;
 1289         }
 1290 
 1291         m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
 1292         while ((m != NULL) && (pcount-- > 0)) {
 1293                 int actcount;
 1294 
 1295                 if (m->queue != PQ_ACTIVE) {
 1296                         break;
 1297                 }
 1298 
 1299                 next = TAILQ_NEXT(m, pageq);
 1300                 /*
 1301                  * Don't deactivate pages that are busy.
 1302                  */
 1303                 if ((m->busy != 0) ||
 1304                     (m->flags & PG_BUSY) ||
 1305                     (m->hold_count != 0)) {
 1306                         vm_pageq_requeue(m);
 1307                         m = next;
 1308                         continue;
 1309                 }
 1310 
 1311                 actcount = 0;
 1312                 if (m->flags & PG_REFERENCED) {
 1313                         vm_page_flag_clear(m, PG_REFERENCED);
 1314                         actcount += 1;
 1315                 }
 1316 
 1317                 actcount += pmap_ts_referenced(m);
 1318                 if (actcount) {
 1319                         m->act_count += ACT_ADVANCE + actcount;
 1320                         if (m->act_count > ACT_MAX)
 1321                                 m->act_count = ACT_MAX;
 1322                         vm_pageq_requeue(m);
 1323                 } else {
 1324                         if (m->act_count == 0) {
 1325                                 /*
 1326                                  * We turn off page access, so that we have
 1327                                  * more accurate RSS stats.  We don't do this
 1328                                  * in the normal page deactivation when the
 1329                                  * system is loaded VM wise, because the
 1330                                  * cost of the large number of page protect
 1331                                  * operations would be higher than the value
 1332                                  * of doing the operation.
 1333                                  */
 1334                                 pmap_remove_all(m);
 1335                                 vm_page_deactivate(m);
 1336                         } else {
 1337                                 m->act_count -= min(m->act_count, ACT_DECLINE);
 1338                                 vm_pageq_requeue(m);
 1339                         }
 1340                 }
 1341 
 1342                 m = next;
 1343         }
 1344         vm_page_unlock_queues();
 1345         splx(s0);
 1346 }
 1347 
 1348 static int
 1349 vm_pageout_free_page_calc(count)
 1350 vm_size_t count;
 1351 {
 1352         if (count < cnt.v_page_count)
 1353                  return 0;
 1354         /*
 1355          * free_reserved needs to include enough for the largest swap pager
 1356          * structures plus enough for any pv_entry structs when paging.
 1357          */
 1358         if (cnt.v_page_count > 1024)
 1359                 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
 1360         else
 1361                 cnt.v_free_min = 4;
 1362         cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
 1363                 cnt.v_interrupt_free_min;
 1364         cnt.v_free_reserved = vm_pageout_page_count +
 1365                 cnt.v_pageout_free_min + (count / 768) + PQ_L2_SIZE;
 1366         cnt.v_free_severe = cnt.v_free_min / 2;
 1367         cnt.v_free_min += cnt.v_free_reserved;
 1368         cnt.v_free_severe += cnt.v_free_reserved;
 1369         return 1;
 1370 }
 1371 
 1372 /*
 1373  *      vm_pageout is the high level pageout daemon.
 1374  */
 1375 static void
 1376 vm_pageout()
 1377 {
 1378         int error, pass, s;
 1379 
 1380         mtx_lock(&Giant);
 1381 
 1382         /*
 1383          * Initialize some paging parameters.
 1384          */
 1385         cnt.v_interrupt_free_min = 2;
 1386         if (cnt.v_page_count < 2000)
 1387                 vm_pageout_page_count = 8;
 1388 
 1389         vm_pageout_free_page_calc(cnt.v_page_count);
 1390         /*
 1391          * v_free_target and v_cache_min control pageout hysteresis.  Note
 1392          * that these are more a measure of the VM cache queue hysteresis
 1393          * then the VM free queue.  Specifically, v_free_target is the
 1394          * high water mark (free+cache pages).
 1395          *
 1396          * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
 1397          * low water mark, while v_free_min is the stop.  v_cache_min must
 1398          * be big enough to handle memory needs while the pageout daemon
 1399          * is signalled and run to free more pages.
 1400          */
 1401         if (cnt.v_free_count > 6144)
 1402                 cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
 1403         else
 1404                 cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
 1405 
 1406         if (cnt.v_free_count > 2048) {
 1407                 cnt.v_cache_min = cnt.v_free_target;
 1408                 cnt.v_cache_max = 2 * cnt.v_cache_min;
 1409                 cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
 1410         } else {
 1411                 cnt.v_cache_min = 0;
 1412                 cnt.v_cache_max = 0;
 1413                 cnt.v_inactive_target = cnt.v_free_count / 4;
 1414         }
 1415         if (cnt.v_inactive_target > cnt.v_free_count / 3)
 1416                 cnt.v_inactive_target = cnt.v_free_count / 3;
 1417 
 1418         /* XXX does not really belong here */
 1419         if (vm_page_max_wired == 0)
 1420                 vm_page_max_wired = cnt.v_free_count / 3;
 1421 
 1422         if (vm_pageout_stats_max == 0)
 1423                 vm_pageout_stats_max = cnt.v_free_target;
 1424 
 1425         /*
 1426          * Set interval in seconds for stats scan.
 1427          */
 1428         if (vm_pageout_stats_interval == 0)
 1429                 vm_pageout_stats_interval = 5;
 1430         if (vm_pageout_full_stats_interval == 0)
 1431                 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
 1432 
 1433         /*
 1434          * Set maximum free per pass
 1435          */
 1436         if (vm_pageout_stats_free_max == 0)
 1437                 vm_pageout_stats_free_max = 5;
 1438 
 1439         swap_pager_swap_init();
 1440         pass = 0;
 1441         /*
 1442          * The pageout daemon is never done, so loop forever.
 1443          */
 1444         while (TRUE) {
 1445                 s = splvm();
 1446                 vm_page_lock_queues();
 1447                 /*
 1448                  * If we have enough free memory, wakeup waiters.  Do
 1449                  * not clear vm_pages_needed until we reach our target,
 1450                  * otherwise we may be woken up over and over again and
 1451                  * waste a lot of cpu.
 1452                  */
 1453                 if (vm_pages_needed && !vm_page_count_min()) {
 1454                         if (!vm_paging_needed())
 1455                                 vm_pages_needed = 0;
 1456                         wakeup(&cnt.v_free_count);
 1457                 }
 1458                 if (vm_pages_needed) {
 1459                         /*
 1460                          * Still not done, take a second pass without waiting
 1461                          * (unlimited dirty cleaning), otherwise sleep a bit
 1462                          * and try again.
 1463                          */
 1464                         ++pass;
 1465                         if (pass > 1)
 1466                                 msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
 1467                                        "psleep", hz/2);
 1468                 } else {
 1469                         /*
 1470                          * Good enough, sleep & handle stats.  Prime the pass
 1471                          * for the next run.
 1472                          */
 1473                         if (pass > 1)
 1474                                 pass = 1;
 1475                         else
 1476                                 pass = 0;
 1477                         error = msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
 1478                                     "psleep", vm_pageout_stats_interval * hz);
 1479                         if (error && !vm_pages_needed) {
 1480                                 vm_page_unlock_queues();
 1481                                 splx(s);
 1482                                 pass = 0;
 1483                                 vm_pageout_page_stats();
 1484                                 continue;
 1485                         }
 1486                 }
 1487                 if (vm_pages_needed)
 1488                         cnt.v_pdwakeups++;
 1489                 vm_page_unlock_queues();
 1490                 splx(s);
 1491                 vm_pageout_scan(pass);
 1492         }
 1493 }
 1494 
 1495 /*
 1496  * Unless the page queue lock is held by the caller, this function
 1497  * should be regarded as advisory.  Specifically, the caller should
 1498  * not msleep() on &cnt.v_free_count following this function unless
 1499  * the page queue lock is held until the msleep() is performed.
 1500  */
 1501 void
 1502 pagedaemon_wakeup()
 1503 {
 1504 
 1505         if (!vm_pages_needed && curthread->td_proc != pageproc) {
 1506                 vm_pages_needed = 1;
 1507                 wakeup(&vm_pages_needed);
 1508         }
 1509 }
 1510 
 1511 #if !defined(NO_SWAPPING)
 1512 static void
 1513 vm_req_vmdaemon()
 1514 {
 1515         static int lastrun = 0;
 1516 
 1517         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 1518                 wakeup(&vm_daemon_needed);
 1519                 lastrun = ticks;
 1520         }
 1521 }
 1522 
 1523 static void
 1524 vm_daemon()
 1525 {
 1526         struct proc *p;
 1527         int breakout;
 1528         struct thread *td;
 1529 
 1530         mtx_lock(&Giant);
 1531         while (TRUE) {
 1532                 tsleep(&vm_daemon_needed, PPAUSE, "psleep", 0);
 1533                 if (vm_pageout_req_swapout) {
 1534                         swapout_procs(vm_pageout_req_swapout);
 1535                         vm_pageout_req_swapout = 0;
 1536                 }
 1537                 /*
 1538                  * scan the processes for exceeding their rlimits or if
 1539                  * process is swapped out -- deactivate pages
 1540                  */
 1541                 sx_slock(&allproc_lock);
 1542                 LIST_FOREACH(p, &allproc, p_list) {
 1543                         vm_pindex_t limit, size;
 1544 
 1545                         /*
 1546                          * if this is a system process or if we have already
 1547                          * looked at this process, skip it.
 1548                          */
 1549                         PROC_LOCK(p);
 1550                         if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
 1551                                 PROC_UNLOCK(p);
 1552                                 continue;
 1553                         }
 1554                         /*
 1555                          * if the process is in a non-running type state,
 1556                          * don't touch it.
 1557                          */
 1558                         mtx_lock_spin(&sched_lock);
 1559                         breakout = 0;
 1560                         FOREACH_THREAD_IN_PROC(p, td) {
 1561                                 if (!TD_ON_RUNQ(td) &&
 1562                                     !TD_IS_RUNNING(td) &&
 1563                                     !TD_IS_SLEEPING(td)) {
 1564                                         breakout = 1;
 1565                                         break;
 1566                                 }
 1567                         }
 1568                         mtx_unlock_spin(&sched_lock);
 1569                         if (breakout) {
 1570                                 PROC_UNLOCK(p);
 1571                                 continue;
 1572                         }
 1573                         /*
 1574                          * get a limit
 1575                          */
 1576                         limit = OFF_TO_IDX(
 1577                             qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
 1578                                 p->p_rlimit[RLIMIT_RSS].rlim_max));
 1579 
 1580                         /*
 1581                          * let processes that are swapped out really be
 1582                          * swapped out set the limit to nothing (will force a
 1583                          * swap-out.)
 1584                          */
 1585                         if ((p->p_sflag & PS_INMEM) == 0)
 1586                                 limit = 0;      /* XXX */
 1587                         PROC_UNLOCK(p);
 1588 
 1589                         size = vmspace_resident_count(p->p_vmspace);
 1590                         if (limit >= 0 && size >= limit) {
 1591                                 vm_pageout_map_deactivate_pages(
 1592                                     &p->p_vmspace->vm_map, limit);
 1593                         }
 1594                 }
 1595                 sx_sunlock(&allproc_lock);
 1596         }
 1597 }
 1598 #endif                  /* !defined(NO_SWAPPING) */

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