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  * Copyright (c) 2005 Yahoo! Technologies Norway AS
    9  * All rights reserved.
   10  *
   11  * This code is derived from software contributed to Berkeley by
   12  * The Mach Operating System project at Carnegie-Mellon University.
   13  *
   14  * Redistribution and use in source and binary forms, with or without
   15  * modification, are permitted provided that the following conditions
   16  * are met:
   17  * 1. Redistributions of source code must retain the above copyright
   18  *    notice, this list of conditions and the following disclaimer.
   19  * 2. Redistributions in binary form must reproduce the above copyright
   20  *    notice, this list of conditions and the following disclaimer in the
   21  *    documentation and/or other materials provided with the distribution.
   22  * 3. All advertising materials mentioning features or use of this software
   23  *    must display the following acknowledgement:
   24  *      This product includes software developed by the University of
   25  *      California, Berkeley and its contributors.
   26  * 4. Neither the name of the University nor the names of its contributors
   27  *    may be used to endorse or promote products derived from this software
   28  *    without specific prior written permission.
   29  *
   30  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   31  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   32  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   33  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   34  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   35  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   36  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   38  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   39  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   40  * SUCH DAMAGE.
   41  *
   42  *      from: @(#)vm_pageout.c  7.4 (Berkeley) 5/7/91
   43  *
   44  *
   45  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   46  * All rights reserved.
   47  *
   48  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   49  *
   50  * Permission to use, copy, modify and distribute this software and
   51  * its documentation is hereby granted, provided that both the copyright
   52  * notice and this permission notice appear in all copies of the
   53  * software, derivative works or modified versions, and any portions
   54  * thereof, and that both notices appear in supporting documentation.
   55  *
   56  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   57  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   58  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   59  *
   60  * Carnegie Mellon requests users of this software to return to
   61  *
   62  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   63  *  School of Computer Science
   64  *  Carnegie Mellon University
   65  *  Pittsburgh PA 15213-3890
   66  *
   67  * any improvements or extensions that they make and grant Carnegie the
   68  * rights to redistribute these changes.
   69  */
   70 
   71 /*
   72  *      The proverbial page-out daemon.
   73  */
   74 
   75 #include <sys/cdefs.h>
   76 __FBSDID("$FreeBSD: head/sys/vm/vm_pageout.c 284387 2015-06-14 20:23:41Z kib $");
   77 
   78 #include "opt_vm.h"
   79 #include "opt_kdtrace.h"
   80 #include <sys/param.h>
   81 #include <sys/systm.h>
   82 #include <sys/kernel.h>
   83 #include <sys/eventhandler.h>
   84 #include <sys/lock.h>
   85 #include <sys/mutex.h>
   86 #include <sys/proc.h>
   87 #include <sys/kthread.h>
   88 #include <sys/ktr.h>
   89 #include <sys/mount.h>
   90 #include <sys/racct.h>
   91 #include <sys/resourcevar.h>
   92 #include <sys/sched.h>
   93 #include <sys/sdt.h>
   94 #include <sys/signalvar.h>
   95 #include <sys/smp.h>
   96 #include <sys/vnode.h>
   97 #include <sys/vmmeter.h>
   98 #include <sys/rwlock.h>
   99 #include <sys/sx.h>
  100 #include <sys/sysctl.h>
  101 
  102 #include <vm/vm.h>
  103 #include <vm/vm_param.h>
  104 #include <vm/vm_object.h>
  105 #include <vm/vm_page.h>
  106 #include <vm/vm_map.h>
  107 #include <vm/vm_pageout.h>
  108 #include <vm/vm_pager.h>
  109 #include <vm/vm_phys.h>
  110 #include <vm/swap_pager.h>
  111 #include <vm/vm_extern.h>
  112 #include <vm/uma.h>
  113 
  114 /*
  115  * System initialization
  116  */
  117 
  118 /* the kernel process "vm_pageout"*/
  119 static void vm_pageout(void);
  120 static void vm_pageout_init(void);
  121 static int vm_pageout_clean(vm_page_t m);
  122 static int vm_pageout_cluster(vm_page_t m);
  123 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
  124 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
  125 
  126 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
  127     NULL);
  128 
  129 struct proc *pageproc;
  130 
  131 static struct kproc_desc page_kp = {
  132         "pagedaemon",
  133         vm_pageout,
  134         &pageproc
  135 };
  136 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
  137     &page_kp);
  138 
  139 SDT_PROVIDER_DEFINE(vm);
  140 SDT_PROBE_DEFINE(vm, , , vm__lowmem_cache);
  141 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
  142 
  143 #if !defined(NO_SWAPPING)
  144 /* the kernel process "vm_daemon"*/
  145 static void vm_daemon(void);
  146 static struct   proc *vmproc;
  147 
  148 static struct kproc_desc vm_kp = {
  149         "vmdaemon",
  150         vm_daemon,
  151         &vmproc
  152 };
  153 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
  154 #endif
  155 
  156 
  157 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
  158 int vm_pageout_deficit;         /* Estimated number of pages deficit */
  159 int vm_pageout_pages_needed;    /* flag saying that the pageout daemon needs pages */
  160 int vm_pageout_wakeup_thresh;
  161 
  162 #if !defined(NO_SWAPPING)
  163 static int vm_pageout_req_swapout;      /* XXX */
  164 static int vm_daemon_needed;
  165 static struct mtx vm_daemon_mtx;
  166 /* Allow for use by vm_pageout before vm_daemon is initialized. */
  167 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
  168 #endif
  169 static int vm_max_launder = 32;
  170 static int vm_pageout_update_period;
  171 static int defer_swap_pageouts;
  172 static int disable_swap_pageouts;
  173 static int lowmem_period = 10;
  174 static int lowmem_ticks;
  175 
  176 #if defined(NO_SWAPPING)
  177 static int vm_swap_enabled = 0;
  178 static int vm_swap_idle_enabled = 0;
  179 #else
  180 static int vm_swap_enabled = 1;
  181 static int vm_swap_idle_enabled = 0;
  182 #endif
  183 
  184 static int vm_panic_on_oom = 0;
  185 
  186 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
  187         CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
  188         "panic on out of memory instead of killing the largest process");
  189 
  190 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
  191         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
  192         "free page threshold for waking up the pageout daemon");
  193 
  194 SYSCTL_INT(_vm, OID_AUTO, max_launder,
  195         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
  196 
  197 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
  198         CTLFLAG_RW, &vm_pageout_update_period, 0,
  199         "Maximum active LRU update period");
  200   
  201 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
  202         "Low memory callback period");
  203 
  204 #if defined(NO_SWAPPING)
  205 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  206         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
  207 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  208         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
  209 #else
  210 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  211         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
  212 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  213         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
  214 #endif
  215 
  216 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
  217         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
  218 
  219 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
  220         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
  221 
  222 static int pageout_lock_miss;
  223 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
  224         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
  225 
  226 #define VM_PAGEOUT_PAGE_COUNT 16
  227 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
  228 
  229 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
  230 SYSCTL_INT(_vm, OID_AUTO, max_wired,
  231         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
  232 
  233 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
  234 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
  235     vm_paddr_t);
  236 #if !defined(NO_SWAPPING)
  237 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
  238 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
  239 static void vm_req_vmdaemon(int req);
  240 #endif
  241 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
  242 
  243 /*
  244  * Initialize a dummy page for marking the caller's place in the specified
  245  * paging queue.  In principle, this function only needs to set the flag
  246  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
  247  * to one as safety precautions.
  248  */ 
  249 static void
  250 vm_pageout_init_marker(vm_page_t marker, u_short queue)
  251 {
  252 
  253         bzero(marker, sizeof(*marker));
  254         marker->flags = PG_MARKER;
  255         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
  256         marker->queue = queue;
  257         marker->hold_count = 1;
  258 }
  259 
  260 /*
  261  * vm_pageout_fallback_object_lock:
  262  * 
  263  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
  264  * known to have failed and page queue must be either PQ_ACTIVE or
  265  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
  266  * while locking the vm object.  Use marker page to detect page queue
  267  * changes and maintain notion of next page on page queue.  Return
  268  * TRUE if no changes were detected, FALSE otherwise.  vm object is
  269  * locked on return.
  270  * 
  271  * This function depends on both the lock portion of struct vm_object
  272  * and normal struct vm_page being type stable.
  273  */
  274 static boolean_t
  275 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
  276 {
  277         struct vm_page marker;
  278         struct vm_pagequeue *pq;
  279         boolean_t unchanged;
  280         u_short queue;
  281         vm_object_t object;
  282 
  283         queue = m->queue;
  284         vm_pageout_init_marker(&marker, queue);
  285         pq = vm_page_pagequeue(m);
  286         object = m->object;
  287         
  288         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
  289         vm_pagequeue_unlock(pq);
  290         vm_page_unlock(m);
  291         VM_OBJECT_WLOCK(object);
  292         vm_page_lock(m);
  293         vm_pagequeue_lock(pq);
  294 
  295         /* Page queue might have changed. */
  296         *next = TAILQ_NEXT(&marker, plinks.q);
  297         unchanged = (m->queue == queue &&
  298                      m->object == object &&
  299                      &marker == TAILQ_NEXT(m, plinks.q));
  300         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
  301         return (unchanged);
  302 }
  303 
  304 /*
  305  * Lock the page while holding the page queue lock.  Use marker page
  306  * to detect page queue changes and maintain notion of next page on
  307  * page queue.  Return TRUE if no changes were detected, FALSE
  308  * otherwise.  The page is locked on return. The page queue lock might
  309  * be dropped and reacquired.
  310  *
  311  * This function depends on normal struct vm_page being type stable.
  312  */
  313 static boolean_t
  314 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
  315 {
  316         struct vm_page marker;
  317         struct vm_pagequeue *pq;
  318         boolean_t unchanged;
  319         u_short queue;
  320 
  321         vm_page_lock_assert(m, MA_NOTOWNED);
  322         if (vm_page_trylock(m))
  323                 return (TRUE);
  324 
  325         queue = m->queue;
  326         vm_pageout_init_marker(&marker, queue);
  327         pq = vm_page_pagequeue(m);
  328 
  329         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
  330         vm_pagequeue_unlock(pq);
  331         vm_page_lock(m);
  332         vm_pagequeue_lock(pq);
  333 
  334         /* Page queue might have changed. */
  335         *next = TAILQ_NEXT(&marker, plinks.q);
  336         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
  337         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
  338         return (unchanged);
  339 }
  340 
  341 /*
  342  * vm_pageout_clean:
  343  *
  344  * Clean the page and remove it from the laundry.
  345  * 
  346  * We set the busy bit to cause potential page faults on this page to
  347  * block.  Note the careful timing, however, the busy bit isn't set till
  348  * late and we cannot do anything that will mess with the page.
  349  */
  350 static int
  351 vm_pageout_cluster(vm_page_t m)
  352 {
  353         vm_object_t object;
  354         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
  355         int pageout_count;
  356         int ib, is, page_base;
  357         vm_pindex_t pindex = m->pindex;
  358 
  359         vm_page_lock_assert(m, MA_OWNED);
  360         object = m->object;
  361         VM_OBJECT_ASSERT_WLOCKED(object);
  362 
  363         /*
  364          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
  365          * with the new swapper, but we could have serious problems paging
  366          * out other object types if there is insufficient memory.  
  367          *
  368          * Unfortunately, checking free memory here is far too late, so the
  369          * check has been moved up a procedural level.
  370          */
  371 
  372         /*
  373          * Can't clean the page if it's busy or held.
  374          */
  375         vm_page_assert_unbusied(m);
  376         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
  377         vm_page_unlock(m);
  378 
  379         mc[vm_pageout_page_count] = pb = ps = m;
  380         pageout_count = 1;
  381         page_base = vm_pageout_page_count;
  382         ib = 1;
  383         is = 1;
  384 
  385         /*
  386          * Scan object for clusterable pages.
  387          *
  388          * We can cluster ONLY if: ->> the page is NOT
  389          * clean, wired, busy, held, or mapped into a
  390          * buffer, and one of the following:
  391          * 1) The page is inactive, or a seldom used
  392          *    active page.
  393          * -or-
  394          * 2) we force the issue.
  395          *
  396          * During heavy mmap/modification loads the pageout
  397          * daemon can really fragment the underlying file
  398          * due to flushing pages out of order and not trying
  399          * align the clusters (which leave sporatic out-of-order
  400          * holes).  To solve this problem we do the reverse scan
  401          * first and attempt to align our cluster, then do a 
  402          * forward scan if room remains.
  403          */
  404 more:
  405         while (ib && pageout_count < vm_pageout_page_count) {
  406                 vm_page_t p;
  407 
  408                 if (ib > pindex) {
  409                         ib = 0;
  410                         break;
  411                 }
  412 
  413                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
  414                         ib = 0;
  415                         break;
  416                 }
  417                 vm_page_lock(p);
  418                 vm_page_test_dirty(p);
  419                 if (p->dirty == 0 ||
  420                     p->queue != PQ_INACTIVE ||
  421                     p->hold_count != 0) {       /* may be undergoing I/O */
  422                         vm_page_unlock(p);
  423                         ib = 0;
  424                         break;
  425                 }
  426                 vm_page_unlock(p);
  427                 mc[--page_base] = pb = p;
  428                 ++pageout_count;
  429                 ++ib;
  430                 /*
  431                  * alignment boundry, stop here and switch directions.  Do
  432                  * not clear ib.
  433                  */
  434                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
  435                         break;
  436         }
  437 
  438         while (pageout_count < vm_pageout_page_count && 
  439             pindex + is < object->size) {
  440                 vm_page_t p;
  441 
  442                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
  443                         break;
  444                 vm_page_lock(p);
  445                 vm_page_test_dirty(p);
  446                 if (p->dirty == 0 ||
  447                     p->queue != PQ_INACTIVE ||
  448                     p->hold_count != 0) {       /* may be undergoing I/O */
  449                         vm_page_unlock(p);
  450                         break;
  451                 }
  452                 vm_page_unlock(p);
  453                 mc[page_base + pageout_count] = ps = p;
  454                 ++pageout_count;
  455                 ++is;
  456         }
  457 
  458         /*
  459          * If we exhausted our forward scan, continue with the reverse scan
  460          * when possible, even past a page boundry.  This catches boundry
  461          * conditions.
  462          */
  463         if (ib && pageout_count < vm_pageout_page_count)
  464                 goto more;
  465 
  466         /*
  467          * we allow reads during pageouts...
  468          */
  469         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
  470             NULL));
  471 }
  472 
  473 /*
  474  * vm_pageout_flush() - launder the given pages
  475  *
  476  *      The given pages are laundered.  Note that we setup for the start of
  477  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
  478  *      reference count all in here rather then in the parent.  If we want
  479  *      the parent to do more sophisticated things we may have to change
  480  *      the ordering.
  481  *
  482  *      Returned runlen is the count of pages between mreq and first
  483  *      page after mreq with status VM_PAGER_AGAIN.
  484  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
  485  *      for any page in runlen set.
  486  */
  487 int
  488 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
  489     boolean_t *eio)
  490 {
  491         vm_object_t object = mc[0]->object;
  492         int pageout_status[count];
  493         int numpagedout = 0;
  494         int i, runlen;
  495 
  496         VM_OBJECT_ASSERT_WLOCKED(object);
  497 
  498         /*
  499          * Initiate I/O.  Bump the vm_page_t->busy counter and
  500          * mark the pages read-only.
  501          *
  502          * We do not have to fixup the clean/dirty bits here... we can
  503          * allow the pager to do it after the I/O completes.
  504          *
  505          * NOTE! mc[i]->dirty may be partial or fragmented due to an
  506          * edge case with file fragments.
  507          */
  508         for (i = 0; i < count; i++) {
  509                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
  510                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
  511                         mc[i], i, count));
  512                 vm_page_sbusy(mc[i]);
  513                 pmap_remove_write(mc[i]);
  514         }
  515         vm_object_pip_add(object, count);
  516 
  517         vm_pager_put_pages(object, mc, count, flags, pageout_status);
  518 
  519         runlen = count - mreq;
  520         if (eio != NULL)
  521                 *eio = FALSE;
  522         for (i = 0; i < count; i++) {
  523                 vm_page_t mt = mc[i];
  524 
  525                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
  526                     !pmap_page_is_write_mapped(mt),
  527                     ("vm_pageout_flush: page %p is not write protected", mt));
  528                 switch (pageout_status[i]) {
  529                 case VM_PAGER_OK:
  530                 case VM_PAGER_PEND:
  531                         numpagedout++;
  532                         break;
  533                 case VM_PAGER_BAD:
  534                         /*
  535                          * Page outside of range of object. Right now we
  536                          * essentially lose the changes by pretending it
  537                          * worked.
  538                          */
  539                         vm_page_undirty(mt);
  540                         break;
  541                 case VM_PAGER_ERROR:
  542                 case VM_PAGER_FAIL:
  543                         /*
  544                          * If page couldn't be paged out, then reactivate the
  545                          * page so it doesn't clog the inactive list.  (We
  546                          * will try paging out it again later).
  547                          */
  548                         vm_page_lock(mt);
  549                         vm_page_activate(mt);
  550                         vm_page_unlock(mt);
  551                         if (eio != NULL && i >= mreq && i - mreq < runlen)
  552                                 *eio = TRUE;
  553                         break;
  554                 case VM_PAGER_AGAIN:
  555                         if (i >= mreq && i - mreq < runlen)
  556                                 runlen = i - mreq;
  557                         break;
  558                 }
  559 
  560                 /*
  561                  * If the operation is still going, leave the page busy to
  562                  * block all other accesses. Also, leave the paging in
  563                  * progress indicator set so that we don't attempt an object
  564                  * collapse.
  565                  */
  566                 if (pageout_status[i] != VM_PAGER_PEND) {
  567                         vm_object_pip_wakeup(object);
  568                         vm_page_sunbusy(mt);
  569                         if (vm_page_count_severe()) {
  570                                 vm_page_lock(mt);
  571                                 vm_page_try_to_cache(mt);
  572                                 vm_page_unlock(mt);
  573                         }
  574                 }
  575         }
  576         if (prunlen != NULL)
  577                 *prunlen = runlen;
  578         return (numpagedout);
  579 }
  580 
  581 static boolean_t
  582 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
  583     vm_paddr_t high)
  584 {
  585         struct mount *mp;
  586         struct vnode *vp;
  587         vm_object_t object;
  588         vm_paddr_t pa;
  589         vm_page_t m, m_tmp, next;
  590         int lockmode;
  591 
  592         vm_pagequeue_lock(pq);
  593         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
  594                 if ((m->flags & PG_MARKER) != 0)
  595                         continue;
  596                 pa = VM_PAGE_TO_PHYS(m);
  597                 if (pa < low || pa + PAGE_SIZE > high)
  598                         continue;
  599                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
  600                         vm_page_unlock(m);
  601                         continue;
  602                 }
  603                 object = m->object;
  604                 if ((!VM_OBJECT_TRYWLOCK(object) &&
  605                     (!vm_pageout_fallback_object_lock(m, &next) ||
  606                     m->hold_count != 0)) || vm_page_busied(m)) {
  607                         vm_page_unlock(m);
  608                         VM_OBJECT_WUNLOCK(object);
  609                         continue;
  610                 }
  611                 vm_page_test_dirty(m);
  612                 if (m->dirty == 0 && object->ref_count != 0)
  613                         pmap_remove_all(m);
  614                 if (m->dirty != 0) {
  615                         vm_page_unlock(m);
  616                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
  617                                 VM_OBJECT_WUNLOCK(object);
  618                                 continue;
  619                         }
  620                         if (object->type == OBJT_VNODE) {
  621                                 vm_pagequeue_unlock(pq);
  622                                 vp = object->handle;
  623                                 vm_object_reference_locked(object);
  624                                 VM_OBJECT_WUNLOCK(object);
  625                                 (void)vn_start_write(vp, &mp, V_WAIT);
  626                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
  627                                     LK_SHARED : LK_EXCLUSIVE;
  628                                 vn_lock(vp, lockmode | LK_RETRY);
  629                                 VM_OBJECT_WLOCK(object);
  630                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
  631                                 VM_OBJECT_WUNLOCK(object);
  632                                 VOP_UNLOCK(vp, 0);
  633                                 vm_object_deallocate(object);
  634                                 vn_finished_write(mp);
  635                                 return (TRUE);
  636                         } else if (object->type == OBJT_SWAP ||
  637                             object->type == OBJT_DEFAULT) {
  638                                 vm_pagequeue_unlock(pq);
  639                                 m_tmp = m;
  640                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
  641                                     0, NULL, NULL);
  642                                 VM_OBJECT_WUNLOCK(object);
  643                                 return (TRUE);
  644                         }
  645                 } else {
  646                         /*
  647                          * Dequeue here to prevent lock recursion in
  648                          * vm_page_cache().
  649                          */
  650                         vm_page_dequeue_locked(m);
  651                         vm_page_cache(m);
  652                         vm_page_unlock(m);
  653                 }
  654                 VM_OBJECT_WUNLOCK(object);
  655         }
  656         vm_pagequeue_unlock(pq);
  657         return (FALSE);
  658 }
  659 
  660 /*
  661  * Increase the number of cached pages.  The specified value, "tries",
  662  * determines which categories of pages are cached:
  663  *
  664  *  0: All clean, inactive pages within the specified physical address range
  665  *     are cached.  Will not sleep.
  666  *  1: The vm_lowmem handlers are called.  All inactive pages within
  667  *     the specified physical address range are cached.  May sleep.
  668  *  2: The vm_lowmem handlers are called.  All inactive and active pages
  669  *     within the specified physical address range are cached.  May sleep.
  670  */
  671 void
  672 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
  673 {
  674         int actl, actmax, inactl, inactmax, dom, initial_dom;
  675         static int start_dom = 0;
  676 
  677         if (tries > 0) {
  678                 /*
  679                  * Decrease registered cache sizes.  The vm_lowmem handlers
  680                  * may acquire locks and/or sleep, so they can only be invoked
  681                  * when "tries" is greater than zero.
  682                  */
  683                 SDT_PROBE0(vm, , , vm__lowmem_cache);
  684                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  685 
  686                 /*
  687                  * We do this explicitly after the caches have been drained
  688                  * above.
  689                  */
  690                 uma_reclaim();
  691         }
  692 
  693         /*
  694          * Make the next scan start on the next domain.
  695          */
  696         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
  697 
  698         inactl = 0;
  699         inactmax = vm_cnt.v_inactive_count;
  700         actl = 0;
  701         actmax = tries < 2 ? 0 : vm_cnt.v_active_count;
  702         dom = initial_dom;
  703 
  704         /*
  705          * Scan domains in round-robin order, first inactive queues,
  706          * then active.  Since domain usually owns large physically
  707          * contiguous chunk of memory, it makes sense to completely
  708          * exhaust one domain before switching to next, while growing
  709          * the pool of contiguous physical pages.
  710          *
  711          * Do not even start launder a domain which cannot contain
  712          * the specified address range, as indicated by segments
  713          * constituting the domain.
  714          */
  715 again:
  716         if (inactl < inactmax) {
  717                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
  718                     low, high) &&
  719                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
  720                     tries, low, high)) {
  721                         inactl++;
  722                         goto again;
  723                 }
  724                 if (++dom == vm_ndomains)
  725                         dom = 0;
  726                 if (dom != initial_dom)
  727                         goto again;
  728         }
  729         if (actl < actmax) {
  730                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
  731                     low, high) &&
  732                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
  733                       tries, low, high)) {
  734                         actl++;
  735                         goto again;
  736                 }
  737                 if (++dom == vm_ndomains)
  738                         dom = 0;
  739                 if (dom != initial_dom)
  740                         goto again;
  741         }
  742 }
  743 
  744 #if !defined(NO_SWAPPING)
  745 /*
  746  *      vm_pageout_object_deactivate_pages
  747  *
  748  *      Deactivate enough pages to satisfy the inactive target
  749  *      requirements.
  750  *
  751  *      The object and map must be locked.
  752  */
  753 static void
  754 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
  755     long desired)
  756 {
  757         vm_object_t backing_object, object;
  758         vm_page_t p;
  759         int act_delta, remove_mode;
  760 
  761         VM_OBJECT_ASSERT_LOCKED(first_object);
  762         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
  763                 return;
  764         for (object = first_object;; object = backing_object) {
  765                 if (pmap_resident_count(pmap) <= desired)
  766                         goto unlock_return;
  767                 VM_OBJECT_ASSERT_LOCKED(object);
  768                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
  769                     object->paging_in_progress != 0)
  770                         goto unlock_return;
  771 
  772                 remove_mode = 0;
  773                 if (object->shadow_count > 1)
  774                         remove_mode = 1;
  775                 /*
  776                  * Scan the object's entire memory queue.
  777                  */
  778                 TAILQ_FOREACH(p, &object->memq, listq) {
  779                         if (pmap_resident_count(pmap) <= desired)
  780                                 goto unlock_return;
  781                         if (vm_page_busied(p))
  782                                 continue;
  783                         PCPU_INC(cnt.v_pdpages);
  784                         vm_page_lock(p);
  785                         if (p->wire_count != 0 || p->hold_count != 0 ||
  786                             !pmap_page_exists_quick(pmap, p)) {
  787                                 vm_page_unlock(p);
  788                                 continue;
  789                         }
  790                         act_delta = pmap_ts_referenced(p);
  791                         if ((p->aflags & PGA_REFERENCED) != 0) {
  792                                 if (act_delta == 0)
  793                                         act_delta = 1;
  794                                 vm_page_aflag_clear(p, PGA_REFERENCED);
  795                         }
  796                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
  797                                 vm_page_activate(p);
  798                                 p->act_count += act_delta;
  799                         } else if (p->queue == PQ_ACTIVE) {
  800                                 if (act_delta == 0) {
  801                                         p->act_count -= min(p->act_count,
  802                                             ACT_DECLINE);
  803                                         if (!remove_mode && p->act_count == 0) {
  804                                                 pmap_remove_all(p);
  805                                                 vm_page_deactivate(p);
  806                                         } else
  807                                                 vm_page_requeue(p);
  808                                 } else {
  809                                         vm_page_activate(p);
  810                                         if (p->act_count < ACT_MAX -
  811                                             ACT_ADVANCE)
  812                                                 p->act_count += ACT_ADVANCE;
  813                                         vm_page_requeue(p);
  814                                 }
  815                         } else if (p->queue == PQ_INACTIVE)
  816                                 pmap_remove_all(p);
  817                         vm_page_unlock(p);
  818                 }
  819                 if ((backing_object = object->backing_object) == NULL)
  820                         goto unlock_return;
  821                 VM_OBJECT_RLOCK(backing_object);
  822                 if (object != first_object)
  823                         VM_OBJECT_RUNLOCK(object);
  824         }
  825 unlock_return:
  826         if (object != first_object)
  827                 VM_OBJECT_RUNLOCK(object);
  828 }
  829 
  830 /*
  831  * deactivate some number of pages in a map, try to do it fairly, but
  832  * that is really hard to do.
  833  */
  834 static void
  835 vm_pageout_map_deactivate_pages(map, desired)
  836         vm_map_t map;
  837         long desired;
  838 {
  839         vm_map_entry_t tmpe;
  840         vm_object_t obj, bigobj;
  841         int nothingwired;
  842 
  843         if (!vm_map_trylock(map))
  844                 return;
  845 
  846         bigobj = NULL;
  847         nothingwired = TRUE;
  848 
  849         /*
  850          * first, search out the biggest object, and try to free pages from
  851          * that.
  852          */
  853         tmpe = map->header.next;
  854         while (tmpe != &map->header) {
  855                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  856                         obj = tmpe->object.vm_object;
  857                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
  858                                 if (obj->shadow_count <= 1 &&
  859                                     (bigobj == NULL ||
  860                                      bigobj->resident_page_count < obj->resident_page_count)) {
  861                                         if (bigobj != NULL)
  862                                                 VM_OBJECT_RUNLOCK(bigobj);
  863                                         bigobj = obj;
  864                                 } else
  865                                         VM_OBJECT_RUNLOCK(obj);
  866                         }
  867                 }
  868                 if (tmpe->wired_count > 0)
  869                         nothingwired = FALSE;
  870                 tmpe = tmpe->next;
  871         }
  872 
  873         if (bigobj != NULL) {
  874                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
  875                 VM_OBJECT_RUNLOCK(bigobj);
  876         }
  877         /*
  878          * Next, hunt around for other pages to deactivate.  We actually
  879          * do this search sort of wrong -- .text first is not the best idea.
  880          */
  881         tmpe = map->header.next;
  882         while (tmpe != &map->header) {
  883                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
  884                         break;
  885                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  886                         obj = tmpe->object.vm_object;
  887                         if (obj != NULL) {
  888                                 VM_OBJECT_RLOCK(obj);
  889                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
  890                                 VM_OBJECT_RUNLOCK(obj);
  891                         }
  892                 }
  893                 tmpe = tmpe->next;
  894         }
  895 
  896         /*
  897          * Remove all mappings if a process is swapped out, this will free page
  898          * table pages.
  899          */
  900         if (desired == 0 && nothingwired) {
  901                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
  902                     vm_map_max(map));
  903         }
  904 
  905         vm_map_unlock(map);
  906 }
  907 #endif          /* !defined(NO_SWAPPING) */
  908 
  909 /*
  910  * Attempt to acquire all of the necessary locks to launder a page and
  911  * then call through the clustering layer to PUTPAGES.  Wait a short
  912  * time for a vnode lock.
  913  *
  914  * Requires the page and object lock on entry, releases both before return.
  915  * Returns 0 on success and an errno otherwise.
  916  */
  917 static int
  918 vm_pageout_clean(vm_page_t m)
  919 {
  920         struct vnode *vp;
  921         struct mount *mp;
  922         vm_object_t object;
  923         vm_pindex_t pindex;
  924         int error, lockmode;
  925 
  926         vm_page_assert_locked(m);
  927         object = m->object;
  928         VM_OBJECT_ASSERT_WLOCKED(object);
  929         error = 0;
  930         vp = NULL;
  931         mp = NULL;
  932 
  933         /*
  934          * The object is already known NOT to be dead.   It
  935          * is possible for the vget() to block the whole
  936          * pageout daemon, but the new low-memory handling
  937          * code should prevent it.
  938          *
  939          * We can't wait forever for the vnode lock, we might
  940          * deadlock due to a vn_read() getting stuck in
  941          * vm_wait while holding this vnode.  We skip the 
  942          * vnode if we can't get it in a reasonable amount
  943          * of time.
  944          */
  945         if (object->type == OBJT_VNODE) {
  946                 vm_page_unlock(m);
  947                 vp = object->handle;
  948                 if (vp->v_type == VREG &&
  949                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
  950                         mp = NULL;
  951                         error = EDEADLK;
  952                         goto unlock_all;
  953                 }
  954                 KASSERT(mp != NULL,
  955                     ("vp %p with NULL v_mount", vp));
  956                 vm_object_reference_locked(object);
  957                 pindex = m->pindex;
  958                 VM_OBJECT_WUNLOCK(object);
  959                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
  960                     LK_SHARED : LK_EXCLUSIVE;
  961                 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
  962                         vp = NULL;
  963                         error = EDEADLK;
  964                         goto unlock_mp;
  965                 }
  966                 VM_OBJECT_WLOCK(object);
  967                 vm_page_lock(m);
  968                 /*
  969                  * While the object and page were unlocked, the page
  970                  * may have been:
  971                  * (1) moved to a different queue,
  972                  * (2) reallocated to a different object,
  973                  * (3) reallocated to a different offset, or
  974                  * (4) cleaned.
  975                  */
  976                 if (m->queue != PQ_INACTIVE || m->object != object ||
  977                     m->pindex != pindex || m->dirty == 0) {
  978                         vm_page_unlock(m);
  979                         error = ENXIO;
  980                         goto unlock_all;
  981                 }
  982 
  983                 /*
  984                  * The page may have been busied or held while the object
  985                  * and page locks were released.
  986                  */
  987                 if (vm_page_busied(m) || m->hold_count != 0) {
  988                         vm_page_unlock(m);
  989                         error = EBUSY;
  990                         goto unlock_all;
  991                 }
  992         }
  993 
  994         /*
  995          * If a page is dirty, then it is either being washed
  996          * (but not yet cleaned) or it is still in the
  997          * laundry.  If it is still in the laundry, then we
  998          * start the cleaning operation. 
  999          */
 1000         if (vm_pageout_cluster(m) == 0)
 1001                 error = EIO;
 1002 
 1003 unlock_all:
 1004         VM_OBJECT_WUNLOCK(object);
 1005 
 1006 unlock_mp:
 1007         vm_page_lock_assert(m, MA_NOTOWNED);
 1008         if (mp != NULL) {
 1009                 if (vp != NULL)
 1010                         vput(vp);
 1011                 vm_object_deallocate(object);
 1012                 vn_finished_write(mp);
 1013         }
 1014 
 1015         return (error);
 1016 }
 1017 
 1018 /*
 1019  *      vm_pageout_scan does the dirty work for the pageout daemon.
 1020  *
 1021  *      pass 0 - Update active LRU/deactivate pages
 1022  *      pass 1 - Move inactive to cache or free
 1023  *      pass 2 - Launder dirty pages
 1024  */
 1025 static void
 1026 vm_pageout_scan(struct vm_domain *vmd, int pass)
 1027 {
 1028         vm_page_t m, next;
 1029         struct vm_pagequeue *pq;
 1030         vm_object_t object;
 1031         int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
 1032         int vnodes_skipped = 0;
 1033         int maxlaunder;
 1034         boolean_t queues_locked;
 1035 
 1036         /*
 1037          * If we need to reclaim memory ask kernel caches to return
 1038          * some.  We rate limit to avoid thrashing.
 1039          */
 1040         if (vmd == &vm_dom[0] && pass > 0 &&
 1041             (ticks - lowmem_ticks) / hz >= lowmem_period) {
 1042                 /*
 1043                  * Decrease registered cache sizes.
 1044                  */
 1045                 SDT_PROBE0(vm, , , vm__lowmem_scan);
 1046                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 1047                 /*
 1048                  * We do this explicitly after the caches have been
 1049                  * drained above.
 1050                  */
 1051                 uma_reclaim();
 1052                 lowmem_ticks = ticks;
 1053         }
 1054 
 1055         /*
 1056          * The addl_page_shortage is the number of temporarily
 1057          * stuck pages in the inactive queue.  In other words, the
 1058          * number of pages from the inactive count that should be
 1059          * discounted in setting the target for the active queue scan.
 1060          */
 1061         addl_page_shortage = 0;
 1062 
 1063         /*
 1064          * Calculate the number of pages we want to either free or move
 1065          * to the cache.
 1066          */
 1067         if (pass > 0) {
 1068                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
 1069                 page_shortage = vm_paging_target() + deficit;
 1070         } else
 1071                 page_shortage = deficit = 0;
 1072 
 1073         /*
 1074          * maxlaunder limits the number of dirty pages we flush per scan.
 1075          * For most systems a smaller value (16 or 32) is more robust under
 1076          * extreme memory and disk pressure because any unnecessary writes
 1077          * to disk can result in extreme performance degredation.  However,
 1078          * systems with excessive dirty pages (especially when MAP_NOSYNC is
 1079          * used) will die horribly with limited laundering.  If the pageout
 1080          * daemon cannot clean enough pages in the first pass, we let it go
 1081          * all out in succeeding passes.
 1082          */
 1083         if ((maxlaunder = vm_max_launder) <= 1)
 1084                 maxlaunder = 1;
 1085         if (pass > 1)
 1086                 maxlaunder = 10000;
 1087 
 1088         /*
 1089          * Start scanning the inactive queue for pages we can move to the
 1090          * cache or free.  The scan will stop when the target is reached or
 1091          * we have scanned the entire inactive queue.  Note that m->act_count
 1092          * is not used to form decisions for the inactive queue, only for the
 1093          * active queue.
 1094          */
 1095         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
 1096         maxscan = pq->pq_cnt;
 1097         vm_pagequeue_lock(pq);
 1098         queues_locked = TRUE;
 1099         for (m = TAILQ_FIRST(&pq->pq_pl);
 1100              m != NULL && maxscan-- > 0 && page_shortage > 0;
 1101              m = next) {
 1102                 vm_pagequeue_assert_locked(pq);
 1103                 KASSERT(queues_locked, ("unlocked queues"));
 1104                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
 1105 
 1106                 PCPU_INC(cnt.v_pdpages);
 1107                 next = TAILQ_NEXT(m, plinks.q);
 1108 
 1109                 /*
 1110                  * skip marker pages
 1111                  */
 1112                 if (m->flags & PG_MARKER)
 1113                         continue;
 1114 
 1115                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 1116                     ("Fictitious page %p cannot be in inactive queue", m));
 1117                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 1118                     ("Unmanaged page %p cannot be in inactive queue", m));
 1119 
 1120                 /*
 1121                  * The page or object lock acquisitions fail if the
 1122                  * page was removed from the queue or moved to a
 1123                  * different position within the queue.  In either
 1124                  * case, addl_page_shortage should not be incremented.
 1125                  */
 1126                 if (!vm_pageout_page_lock(m, &next)) {
 1127                         vm_page_unlock(m);
 1128                         continue;
 1129                 }
 1130                 object = m->object;
 1131                 if (!VM_OBJECT_TRYWLOCK(object) &&
 1132                     !vm_pageout_fallback_object_lock(m, &next)) {
 1133                         vm_page_unlock(m);
 1134                         VM_OBJECT_WUNLOCK(object);
 1135                         continue;
 1136                 }
 1137 
 1138                 /*
 1139                  * Don't mess with busy pages, keep them at at the
 1140                  * front of the queue, most likely they are being
 1141                  * paged out.  Increment addl_page_shortage for busy
 1142                  * pages, because they may leave the inactive queue
 1143                  * shortly after page scan is finished.
 1144                  */
 1145                 if (vm_page_busied(m)) {
 1146                         vm_page_unlock(m);
 1147                         VM_OBJECT_WUNLOCK(object);
 1148                         addl_page_shortage++;
 1149                         continue;
 1150                 }
 1151 
 1152                 /*
 1153                  * We unlock the inactive page queue, invalidating the
 1154                  * 'next' pointer.  Use our marker to remember our
 1155                  * place.
 1156                  */
 1157                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
 1158                 vm_pagequeue_unlock(pq);
 1159                 queues_locked = FALSE;
 1160 
 1161                 /*
 1162                  * Invalid pages can be easily freed. They cannot be
 1163                  * mapped, vm_page_free() asserts this.
 1164                  */
 1165                 if (m->valid == 0 && m->hold_count == 0) {
 1166                         vm_page_free(m);
 1167                         PCPU_INC(cnt.v_dfree);
 1168                         --page_shortage;
 1169                         goto drop_page;
 1170                 }
 1171 
 1172                 /*
 1173                  * We bump the activation count if the page has been
 1174                  * referenced while in the inactive queue.  This makes
 1175                  * it less likely that the page will be added back to the
 1176                  * inactive queue prematurely again.  Here we check the 
 1177                  * page tables (or emulated bits, if any), given the upper 
 1178                  * level VM system not knowing anything about existing 
 1179                  * references.
 1180                  */
 1181                 if ((m->aflags & PGA_REFERENCED) != 0) {
 1182                         vm_page_aflag_clear(m, PGA_REFERENCED);
 1183                         act_delta = 1;
 1184                 } else
 1185                         act_delta = 0;
 1186                 if (object->ref_count != 0) {
 1187                         act_delta += pmap_ts_referenced(m);
 1188                 } else {
 1189                         KASSERT(!pmap_page_is_mapped(m),
 1190                             ("vm_pageout_scan: page %p is mapped", m));
 1191                 }
 1192 
 1193                 /*
 1194                  * If the upper level VM system knows about any page 
 1195                  * references, we reactivate the page or requeue it.
 1196                  */
 1197                 if (act_delta != 0) {
 1198                         if (object->ref_count != 0) {
 1199                                 vm_page_activate(m);
 1200                                 m->act_count += act_delta + ACT_ADVANCE;
 1201                         } else {
 1202                                 vm_pagequeue_lock(pq);
 1203                                 queues_locked = TRUE;
 1204                                 vm_page_requeue_locked(m);
 1205                         }
 1206                         goto drop_page;
 1207                 }
 1208 
 1209                 if (m->hold_count != 0) {
 1210                         /*
 1211                          * Held pages are essentially stuck in the
 1212                          * queue.  So, they ought to be discounted
 1213                          * from the inactive count.  See the
 1214                          * calculation of the page_shortage for the
 1215                          * loop over the active queue below.
 1216                          */
 1217                         addl_page_shortage++;
 1218                         goto drop_page;
 1219                 }
 1220 
 1221                 /*
 1222                  * If the page appears to be clean at the machine-independent
 1223                  * layer, then remove all of its mappings from the pmap in
 1224                  * anticipation of placing it onto the cache queue.  If,
 1225                  * however, any of the page's mappings allow write access,
 1226                  * then the page may still be modified until the last of those
 1227                  * mappings are removed.
 1228                  */
 1229                 vm_page_test_dirty(m);
 1230                 if (m->dirty == 0 && object->ref_count != 0)
 1231                         pmap_remove_all(m);
 1232 
 1233                 if (m->dirty == 0) {
 1234                         /*
 1235                          * Clean pages can be freed.
 1236                          */
 1237                         vm_page_free(m);
 1238                         PCPU_INC(cnt.v_dfree);
 1239                         --page_shortage;
 1240                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
 1241                         /*
 1242                          * Dirty pages need to be paged out, but flushing
 1243                          * a page is extremely expensive versus freeing
 1244                          * a clean page.  Rather then artificially limiting
 1245                          * the number of pages we can flush, we instead give
 1246                          * dirty pages extra priority on the inactive queue
 1247                          * by forcing them to be cycled through the queue
 1248                          * twice before being flushed, after which the
 1249                          * (now clean) page will cycle through once more
 1250                          * before being freed.  This significantly extends
 1251                          * the thrash point for a heavily loaded machine.
 1252                          */
 1253                         m->flags |= PG_WINATCFLS;
 1254                         vm_pagequeue_lock(pq);
 1255                         queues_locked = TRUE;
 1256                         vm_page_requeue_locked(m);
 1257                 } else if (maxlaunder > 0) {
 1258                         /*
 1259                          * We always want to try to flush some dirty pages if
 1260                          * we encounter them, to keep the system stable.
 1261                          * Normally this number is small, but under extreme
 1262                          * pressure where there are insufficient clean pages
 1263                          * on the inactive queue, we may have to go all out.
 1264                          */
 1265                         int swap_pageouts_ok;
 1266                         int error;
 1267 
 1268                         if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
 1269                                 swap_pageouts_ok = 1;
 1270                         } else {
 1271                                 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
 1272                                 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
 1273                                 vm_page_count_min());
 1274                                                                                 
 1275                         }
 1276 
 1277                         /*
 1278                          * We don't bother paging objects that are "dead".  
 1279                          * Those objects are in a "rundown" state.
 1280                          */
 1281                         if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
 1282                                 vm_pagequeue_lock(pq);
 1283                                 vm_page_unlock(m);
 1284                                 VM_OBJECT_WUNLOCK(object);
 1285                                 queues_locked = TRUE;
 1286                                 vm_page_requeue_locked(m);
 1287                                 goto relock_queues;
 1288                         }
 1289                         error = vm_pageout_clean(m);
 1290                         /*
 1291                          * Decrement page_shortage on success to account for
 1292                          * the (future) cleaned page.  Otherwise we could wind
 1293                          * up laundering or cleaning too many pages.
 1294                          */
 1295                         if (error == 0) {
 1296                                 page_shortage--;
 1297                                 maxlaunder--;
 1298                         } else if (error == EDEADLK) {
 1299                                 pageout_lock_miss++;
 1300                                 vnodes_skipped++;
 1301                         } else if (error == EBUSY) {
 1302                                 addl_page_shortage++;
 1303                         }
 1304                         vm_page_lock_assert(m, MA_NOTOWNED);
 1305                         goto relock_queues;
 1306                 }
 1307 drop_page:
 1308                 vm_page_unlock(m);
 1309                 VM_OBJECT_WUNLOCK(object);
 1310 relock_queues:
 1311                 if (!queues_locked) {
 1312                         vm_pagequeue_lock(pq);
 1313                         queues_locked = TRUE;
 1314                 }
 1315                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
 1316                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
 1317         }
 1318         vm_pagequeue_unlock(pq);
 1319 
 1320 #if !defined(NO_SWAPPING)
 1321         /*
 1322          * Wakeup the swapout daemon if we didn't cache or free the targeted
 1323          * number of pages. 
 1324          */
 1325         if (vm_swap_enabled && page_shortage > 0)
 1326                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 1327 #endif
 1328 
 1329         /*
 1330          * Wakeup the sync daemon if we skipped a vnode in a writeable object
 1331          * and we didn't cache or free enough pages.
 1332          */
 1333         if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target -
 1334             vm_cnt.v_free_min)
 1335                 (void)speedup_syncer();
 1336 
 1337         /*
 1338          * Compute the number of pages we want to try to move from the
 1339          * active queue to the inactive queue.
 1340          */
 1341         page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count +
 1342             vm_paging_target() + deficit + addl_page_shortage;
 1343 
 1344         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
 1345         vm_pagequeue_lock(pq);
 1346         maxscan = pq->pq_cnt;
 1347 
 1348         /*
 1349          * If we're just idle polling attempt to visit every
 1350          * active page within 'update_period' seconds.
 1351          */
 1352         if (pass == 0 && vm_pageout_update_period != 0) {
 1353                 maxscan /= vm_pageout_update_period;
 1354                 page_shortage = maxscan;
 1355         }
 1356 
 1357         /*
 1358          * Scan the active queue for things we can deactivate. We nominally
 1359          * track the per-page activity counter and use it to locate
 1360          * deactivation candidates.
 1361          */
 1362         m = TAILQ_FIRST(&pq->pq_pl);
 1363         while (m != NULL && maxscan-- > 0 && page_shortage > 0) {
 1364 
 1365                 KASSERT(m->queue == PQ_ACTIVE,
 1366                     ("vm_pageout_scan: page %p isn't active", m));
 1367 
 1368                 next = TAILQ_NEXT(m, plinks.q);
 1369                 if ((m->flags & PG_MARKER) != 0) {
 1370                         m = next;
 1371                         continue;
 1372                 }
 1373                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 1374                     ("Fictitious page %p cannot be in active queue", m));
 1375                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 1376                     ("Unmanaged page %p cannot be in active queue", m));
 1377                 if (!vm_pageout_page_lock(m, &next)) {
 1378                         vm_page_unlock(m);
 1379                         m = next;
 1380                         continue;
 1381                 }
 1382 
 1383                 /*
 1384                  * The count for pagedaemon pages is done after checking the
 1385                  * page for eligibility...
 1386                  */
 1387                 PCPU_INC(cnt.v_pdpages);
 1388 
 1389                 /*
 1390                  * Check to see "how much" the page has been used.
 1391                  */
 1392                 if ((m->aflags & PGA_REFERENCED) != 0) {
 1393                         vm_page_aflag_clear(m, PGA_REFERENCED);
 1394                         act_delta = 1;
 1395                 } else
 1396                         act_delta = 0;
 1397 
 1398                 /*
 1399                  * Unlocked object ref count check.  Two races are possible.
 1400                  * 1) The ref was transitioning to zero and we saw non-zero,
 1401                  *    the pmap bits will be checked unnecessarily.
 1402                  * 2) The ref was transitioning to one and we saw zero. 
 1403                  *    The page lock prevents a new reference to this page so
 1404                  *    we need not check the reference bits.
 1405                  */
 1406                 if (m->object->ref_count != 0)
 1407                         act_delta += pmap_ts_referenced(m);
 1408 
 1409                 /*
 1410                  * Advance or decay the act_count based on recent usage.
 1411                  */
 1412                 if (act_delta != 0) {
 1413                         m->act_count += ACT_ADVANCE + act_delta;
 1414                         if (m->act_count > ACT_MAX)
 1415                                 m->act_count = ACT_MAX;
 1416                 } else
 1417                         m->act_count -= min(m->act_count, ACT_DECLINE);
 1418 
 1419                 /*
 1420                  * Move this page to the tail of the active or inactive
 1421                  * queue depending on usage.
 1422                  */
 1423                 if (m->act_count == 0) {
 1424                         /* Dequeue to avoid later lock recursion. */
 1425                         vm_page_dequeue_locked(m);
 1426                         vm_page_deactivate(m);
 1427                         page_shortage--;
 1428                 } else
 1429                         vm_page_requeue_locked(m);
 1430                 vm_page_unlock(m);
 1431                 m = next;
 1432         }
 1433         vm_pagequeue_unlock(pq);
 1434 #if !defined(NO_SWAPPING)
 1435         /*
 1436          * Idle process swapout -- run once per second.
 1437          */
 1438         if (vm_swap_idle_enabled) {
 1439                 static long lsec;
 1440                 if (time_second != lsec) {
 1441                         vm_req_vmdaemon(VM_SWAP_IDLE);
 1442                         lsec = time_second;
 1443                 }
 1444         }
 1445 #endif
 1446 
 1447         /*
 1448          * If we are critically low on one of RAM or swap and low on
 1449          * the other, kill the largest process.  However, we avoid
 1450          * doing this on the first pass in order to give ourselves a
 1451          * chance to flush out dirty vnode-backed pages and to allow
 1452          * active pages to be moved to the inactive queue and reclaimed.
 1453          */
 1454         vm_pageout_mightbe_oom(vmd, pass);
 1455 }
 1456 
 1457 static int vm_pageout_oom_vote;
 1458 
 1459 /*
 1460  * The pagedaemon threads randlomly select one to perform the
 1461  * OOM.  Trying to kill processes before all pagedaemons
 1462  * failed to reach free target is premature.
 1463  */
 1464 static void
 1465 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
 1466 {
 1467         int old_vote;
 1468 
 1469         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
 1470             (swap_pager_full && vm_paging_target() > 0))) {
 1471                 if (vmd->vmd_oom) {
 1472                         vmd->vmd_oom = FALSE;
 1473                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
 1474                 }
 1475                 return;
 1476         }
 1477 
 1478         if (vmd->vmd_oom)
 1479                 return;
 1480 
 1481         vmd->vmd_oom = TRUE;
 1482         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
 1483         if (old_vote != vm_ndomains - 1)
 1484                 return;
 1485 
 1486         /*
 1487          * The current pagedaemon thread is the last in the quorum to
 1488          * start OOM.  Initiate the selection and signaling of the
 1489          * victim.
 1490          */
 1491         vm_pageout_oom(VM_OOM_MEM);
 1492 
 1493         /*
 1494          * After one round of OOM terror, recall our vote.  On the
 1495          * next pass, current pagedaemon would vote again if the low
 1496          * memory condition is still there, due to vmd_oom being
 1497          * false.
 1498          */
 1499         vmd->vmd_oom = FALSE;
 1500         atomic_subtract_int(&vm_pageout_oom_vote, 1);
 1501 }
 1502 
 1503 void
 1504 vm_pageout_oom(int shortage)
 1505 {
 1506         struct proc *p, *bigproc;
 1507         vm_offset_t size, bigsize;
 1508         struct thread *td;
 1509         struct vmspace *vm;
 1510 
 1511         /*
 1512          * We keep the process bigproc locked once we find it to keep anyone
 1513          * from messing with it; however, there is a possibility of
 1514          * deadlock if process B is bigproc and one of it's child processes
 1515          * attempts to propagate a signal to B while we are waiting for A's
 1516          * lock while walking this list.  To avoid this, we don't block on
 1517          * the process lock but just skip a process if it is already locked.
 1518          */
 1519         bigproc = NULL;
 1520         bigsize = 0;
 1521         sx_slock(&allproc_lock);
 1522         FOREACH_PROC_IN_SYSTEM(p) {
 1523                 int breakout;
 1524 
 1525                 PROC_LOCK(p);
 1526 
 1527                 /*
 1528                  * If this is a system, protected or killed process, skip it.
 1529                  */
 1530                 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
 1531                     P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
 1532                     p->p_pid == 1 || P_KILLED(p) ||
 1533                     (p->p_pid < 48 && swap_pager_avail != 0)) {
 1534                         PROC_UNLOCK(p);
 1535                         continue;
 1536                 }
 1537                 /*
 1538                  * If the process is in a non-running type state,
 1539                  * don't touch it.  Check all the threads individually.
 1540                  */
 1541                 breakout = 0;
 1542                 FOREACH_THREAD_IN_PROC(p, td) {
 1543                         thread_lock(td);
 1544                         if (!TD_ON_RUNQ(td) &&
 1545                             !TD_IS_RUNNING(td) &&
 1546                             !TD_IS_SLEEPING(td) &&
 1547                             !TD_IS_SUSPENDED(td)) {
 1548                                 thread_unlock(td);
 1549                                 breakout = 1;
 1550                                 break;
 1551                         }
 1552                         thread_unlock(td);
 1553                 }
 1554                 if (breakout) {
 1555                         PROC_UNLOCK(p);
 1556                         continue;
 1557                 }
 1558                 /*
 1559                  * get the process size
 1560                  */
 1561                 vm = vmspace_acquire_ref(p);
 1562                 if (vm == NULL) {
 1563                         PROC_UNLOCK(p);
 1564                         continue;
 1565                 }
 1566                 _PHOLD(p);
 1567                 if (!vm_map_trylock_read(&vm->vm_map)) {
 1568                         _PRELE(p);
 1569                         PROC_UNLOCK(p);
 1570                         vmspace_free(vm);
 1571                         continue;
 1572                 }
 1573                 PROC_UNLOCK(p);
 1574                 size = vmspace_swap_count(vm);
 1575                 vm_map_unlock_read(&vm->vm_map);
 1576                 if (shortage == VM_OOM_MEM)
 1577                         size += vmspace_resident_count(vm);
 1578                 vmspace_free(vm);
 1579                 /*
 1580                  * if the this process is bigger than the biggest one
 1581                  * remember it.
 1582                  */
 1583                 if (size > bigsize) {
 1584                         if (bigproc != NULL)
 1585                                 PRELE(bigproc);
 1586                         bigproc = p;
 1587                         bigsize = size;
 1588                 } else {
 1589                         PRELE(p);
 1590                 }
 1591         }
 1592         sx_sunlock(&allproc_lock);
 1593         if (bigproc != NULL) {
 1594                 if (vm_panic_on_oom != 0)
 1595                         panic("out of swap space");
 1596                 PROC_LOCK(bigproc);
 1597                 killproc(bigproc, "out of swap space");
 1598                 sched_nice(bigproc, PRIO_MIN);
 1599                 _PRELE(bigproc);
 1600                 PROC_UNLOCK(bigproc);
 1601                 wakeup(&vm_cnt.v_free_count);
 1602         }
 1603 }
 1604 
 1605 static void
 1606 vm_pageout_worker(void *arg)
 1607 {
 1608         struct vm_domain *domain;
 1609         int domidx;
 1610 
 1611         domidx = (uintptr_t)arg;
 1612         domain = &vm_dom[domidx];
 1613 
 1614         /*
 1615          * XXXKIB It could be useful to bind pageout daemon threads to
 1616          * the cores belonging to the domain, from which vm_page_array
 1617          * is allocated.
 1618          */
 1619 
 1620         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
 1621         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
 1622 
 1623         /*
 1624          * The pageout daemon worker is never done, so loop forever.
 1625          */
 1626         while (TRUE) {
 1627                 /*
 1628                  * If we have enough free memory, wakeup waiters.  Do
 1629                  * not clear vm_pages_needed until we reach our target,
 1630                  * otherwise we may be woken up over and over again and
 1631                  * waste a lot of cpu.
 1632                  */
 1633                 mtx_lock(&vm_page_queue_free_mtx);
 1634                 if (vm_pages_needed && !vm_page_count_min()) {
 1635                         if (!vm_paging_needed())
 1636                                 vm_pages_needed = 0;
 1637                         wakeup(&vm_cnt.v_free_count);
 1638                 }
 1639                 if (vm_pages_needed) {
 1640                         /*
 1641                          * Still not done, take a second pass without waiting
 1642                          * (unlimited dirty cleaning), otherwise sleep a bit
 1643                          * and try again.
 1644                          */
 1645                         if (domain->vmd_pass > 1)
 1646                                 msleep(&vm_pages_needed,
 1647                                     &vm_page_queue_free_mtx, PVM, "psleep",
 1648                                     hz / 2);
 1649                 } else {
 1650                         /*
 1651                          * Good enough, sleep until required to refresh
 1652                          * stats.
 1653                          */
 1654                         domain->vmd_pass = 0;
 1655                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
 1656                             PVM, "psleep", hz);
 1657 
 1658                 }
 1659                 if (vm_pages_needed) {
 1660                         vm_cnt.v_pdwakeups++;
 1661                         domain->vmd_pass++;
 1662                 }
 1663                 mtx_unlock(&vm_page_queue_free_mtx);
 1664                 vm_pageout_scan(domain, domain->vmd_pass);
 1665         }
 1666 }
 1667 
 1668 /*
 1669  *      vm_pageout_init initialises basic pageout daemon settings.
 1670  */
 1671 static void
 1672 vm_pageout_init(void)
 1673 {
 1674         /*
 1675          * Initialize some paging parameters.
 1676          */
 1677         vm_cnt.v_interrupt_free_min = 2;
 1678         if (vm_cnt.v_page_count < 2000)
 1679                 vm_pageout_page_count = 8;
 1680 
 1681         /*
 1682          * v_free_reserved needs to include enough for the largest
 1683          * swap pager structures plus enough for any pv_entry structs
 1684          * when paging. 
 1685          */
 1686         if (vm_cnt.v_page_count > 1024)
 1687                 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
 1688         else
 1689                 vm_cnt.v_free_min = 4;
 1690         vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
 1691             vm_cnt.v_interrupt_free_min;
 1692         vm_cnt.v_free_reserved = vm_pageout_page_count +
 1693             vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
 1694         vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
 1695         vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
 1696         vm_cnt.v_free_min += vm_cnt.v_free_reserved;
 1697         vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
 1698         vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
 1699         if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
 1700                 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
 1701 
 1702         /*
 1703          * Set the default wakeup threshold to be 10% above the minimum
 1704          * page limit.  This keeps the steady state out of shortfall.
 1705          */
 1706         vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
 1707 
 1708         /*
 1709          * Set interval in seconds for active scan.  We want to visit each
 1710          * page at least once every ten minutes.  This is to prevent worst
 1711          * case paging behaviors with stale active LRU.
 1712          */
 1713         if (vm_pageout_update_period == 0)
 1714                 vm_pageout_update_period = 600;
 1715 
 1716         /* XXX does not really belong here */
 1717         if (vm_page_max_wired == 0)
 1718                 vm_page_max_wired = vm_cnt.v_free_count / 3;
 1719 }
 1720 
 1721 /*
 1722  *     vm_pageout is the high level pageout daemon.
 1723  */
 1724 static void
 1725 vm_pageout(void)
 1726 {
 1727         int error;
 1728 #if MAXMEMDOM > 1
 1729         int i;
 1730 #endif
 1731 
 1732         swap_pager_swap_init();
 1733 #if MAXMEMDOM > 1
 1734         for (i = 1; i < vm_ndomains; i++) {
 1735                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
 1736                     curproc, NULL, 0, 0, "dom%d", i);
 1737                 if (error != 0) {
 1738                         panic("starting pageout for domain %d, error %d\n",
 1739                             i, error);
 1740                 }
 1741         }
 1742 #endif
 1743         error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
 1744             0, 0, "uma");
 1745         if (error != 0)
 1746                 panic("starting uma_reclaim helper, error %d\n", error);
 1747         vm_pageout_worker((void *)(uintptr_t)0);
 1748 }
 1749 
 1750 /*
 1751  * Unless the free page queue lock is held by the caller, this function
 1752  * should be regarded as advisory.  Specifically, the caller should
 1753  * not msleep() on &vm_cnt.v_free_count following this function unless
 1754  * the free page queue lock is held until the msleep() is performed.
 1755  */
 1756 void
 1757 pagedaemon_wakeup(void)
 1758 {
 1759 
 1760         if (!vm_pages_needed && curthread->td_proc != pageproc) {
 1761                 vm_pages_needed = 1;
 1762                 wakeup(&vm_pages_needed);
 1763         }
 1764 }
 1765 
 1766 #if !defined(NO_SWAPPING)
 1767 static void
 1768 vm_req_vmdaemon(int req)
 1769 {
 1770         static int lastrun = 0;
 1771 
 1772         mtx_lock(&vm_daemon_mtx);
 1773         vm_pageout_req_swapout |= req;
 1774         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 1775                 wakeup(&vm_daemon_needed);
 1776                 lastrun = ticks;
 1777         }
 1778         mtx_unlock(&vm_daemon_mtx);
 1779 }
 1780 
 1781 static void
 1782 vm_daemon(void)
 1783 {
 1784         struct rlimit rsslim;
 1785         struct proc *p;
 1786         struct thread *td;
 1787         struct vmspace *vm;
 1788         int breakout, swapout_flags, tryagain, attempts;
 1789 #ifdef RACCT
 1790         uint64_t rsize, ravailable;
 1791 #endif
 1792 
 1793         while (TRUE) {
 1794                 mtx_lock(&vm_daemon_mtx);
 1795                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
 1796 #ifdef RACCT
 1797                     racct_enable ? hz : 0
 1798 #else
 1799                     0
 1800 #endif
 1801                 );
 1802                 swapout_flags = vm_pageout_req_swapout;
 1803                 vm_pageout_req_swapout = 0;
 1804                 mtx_unlock(&vm_daemon_mtx);
 1805                 if (swapout_flags)
 1806                         swapout_procs(swapout_flags);
 1807 
 1808                 /*
 1809                  * scan the processes for exceeding their rlimits or if
 1810                  * process is swapped out -- deactivate pages
 1811                  */
 1812                 tryagain = 0;
 1813                 attempts = 0;
 1814 again:
 1815                 attempts++;
 1816                 sx_slock(&allproc_lock);
 1817                 FOREACH_PROC_IN_SYSTEM(p) {
 1818                         vm_pindex_t limit, size;
 1819 
 1820                         /*
 1821                          * if this is a system process or if we have already
 1822                          * looked at this process, skip it.
 1823                          */
 1824                         PROC_LOCK(p);
 1825                         if (p->p_state != PRS_NORMAL ||
 1826                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 1827                                 PROC_UNLOCK(p);
 1828                                 continue;
 1829                         }
 1830                         /*
 1831                          * if the process is in a non-running type state,
 1832                          * don't touch it.
 1833                          */
 1834                         breakout = 0;
 1835                         FOREACH_THREAD_IN_PROC(p, td) {
 1836                                 thread_lock(td);
 1837                                 if (!TD_ON_RUNQ(td) &&
 1838                                     !TD_IS_RUNNING(td) &&
 1839                                     !TD_IS_SLEEPING(td) &&
 1840                                     !TD_IS_SUSPENDED(td)) {
 1841                                         thread_unlock(td);
 1842                                         breakout = 1;
 1843                                         break;
 1844                                 }
 1845                                 thread_unlock(td);
 1846                         }
 1847                         if (breakout) {
 1848                                 PROC_UNLOCK(p);
 1849                                 continue;
 1850                         }
 1851                         /*
 1852                          * get a limit
 1853                          */
 1854                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
 1855                         limit = OFF_TO_IDX(
 1856                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 1857 
 1858                         /*
 1859                          * let processes that are swapped out really be
 1860                          * swapped out set the limit to nothing (will force a
 1861                          * swap-out.)
 1862                          */
 1863                         if ((p->p_flag & P_INMEM) == 0)
 1864                                 limit = 0;      /* XXX */
 1865                         vm = vmspace_acquire_ref(p);
 1866                         PROC_UNLOCK(p);
 1867                         if (vm == NULL)
 1868                                 continue;
 1869 
 1870                         size = vmspace_resident_count(vm);
 1871                         if (size >= limit) {
 1872                                 vm_pageout_map_deactivate_pages(
 1873                                     &vm->vm_map, limit);
 1874                         }
 1875 #ifdef RACCT
 1876                         if (racct_enable) {
 1877                                 rsize = IDX_TO_OFF(size);
 1878                                 PROC_LOCK(p);
 1879                                 racct_set(p, RACCT_RSS, rsize);
 1880                                 ravailable = racct_get_available(p, RACCT_RSS);
 1881                                 PROC_UNLOCK(p);
 1882                                 if (rsize > ravailable) {
 1883                                         /*
 1884                                          * Don't be overly aggressive; this
 1885                                          * might be an innocent process,
 1886                                          * and the limit could've been exceeded
 1887                                          * by some memory hog.  Don't try
 1888                                          * to deactivate more than 1/4th
 1889                                          * of process' resident set size.
 1890                                          */
 1891                                         if (attempts <= 8) {
 1892                                                 if (ravailable < rsize -
 1893                                                     (rsize / 4)) {
 1894                                                         ravailable = rsize -
 1895                                                             (rsize / 4);
 1896                                                 }
 1897                                         }
 1898                                         vm_pageout_map_deactivate_pages(
 1899                                             &vm->vm_map,
 1900                                             OFF_TO_IDX(ravailable));
 1901                                         /* Update RSS usage after paging out. */
 1902                                         size = vmspace_resident_count(vm);
 1903                                         rsize = IDX_TO_OFF(size);
 1904                                         PROC_LOCK(p);
 1905                                         racct_set(p, RACCT_RSS, rsize);
 1906                                         PROC_UNLOCK(p);
 1907                                         if (rsize > ravailable)
 1908                                                 tryagain = 1;
 1909                                 }
 1910                         }
 1911 #endif
 1912                         vmspace_free(vm);
 1913                 }
 1914                 sx_sunlock(&allproc_lock);
 1915                 if (tryagain != 0 && attempts <= 10)
 1916                         goto again;
 1917         }
 1918 }
 1919 #endif                  /* !defined(NO_SWAPPING) */

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