The Design and Implementation of the FreeBSD Operating System, Second Edition
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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 270759 2014-08-28 19:50:08Z smh $");
   77 
   78 #include "opt_vm.h"
   79 #include <sys/param.h>
   80 #include <sys/systm.h>
   81 #include <sys/kernel.h>
   82 #include <sys/eventhandler.h>
   83 #include <sys/lock.h>
   84 #include <sys/mutex.h>
   85 #include <sys/proc.h>
   86 #include <sys/kthread.h>
   87 #include <sys/ktr.h>
   88 #include <sys/mount.h>
   89 #include <sys/racct.h>
   90 #include <sys/resourcevar.h>
   91 #include <sys/sched.h>
   92 #include <sys/signalvar.h>
   93 #include <sys/smp.h>
   94 #include <sys/vnode.h>
   95 #include <sys/vmmeter.h>
   96 #include <sys/rwlock.h>
   97 #include <sys/sx.h>
   98 #include <sys/sysctl.h>
   99 
  100 #include <vm/vm.h>
  101 #include <vm/vm_param.h>
  102 #include <vm/vm_object.h>
  103 #include <vm/vm_page.h>
  104 #include <vm/vm_map.h>
  105 #include <vm/vm_pageout.h>
  106 #include <vm/vm_pager.h>
  107 #include <vm/vm_phys.h>
  108 #include <vm/swap_pager.h>
  109 #include <vm/vm_extern.h>
  110 #include <vm/uma.h>
  111 
  112 /*
  113  * System initialization
  114  */
  115 
  116 /* the kernel process "vm_pageout"*/
  117 static void vm_pageout(void);
  118 static void vm_pageout_init(void);
  119 static int vm_pageout_clean(vm_page_t);
  120 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
  121 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
  122 
  123 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
  124     NULL);
  125 
  126 struct proc *pageproc;
  127 
  128 static struct kproc_desc page_kp = {
  129         "pagedaemon",
  130         vm_pageout,
  131         &pageproc
  132 };
  133 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
  134     &page_kp);
  135 
  136 #if !defined(NO_SWAPPING)
  137 /* the kernel process "vm_daemon"*/
  138 static void vm_daemon(void);
  139 static struct   proc *vmproc;
  140 
  141 static struct kproc_desc vm_kp = {
  142         "vmdaemon",
  143         vm_daemon,
  144         &vmproc
  145 };
  146 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
  147 #endif
  148 
  149 
  150 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
  151 int vm_pageout_deficit;         /* Estimated number of pages deficit */
  152 int vm_pageout_pages_needed;    /* flag saying that the pageout daemon needs pages */
  153 int vm_pageout_wakeup_thresh;
  154 
  155 #if !defined(NO_SWAPPING)
  156 static int vm_pageout_req_swapout;      /* XXX */
  157 static int vm_daemon_needed;
  158 static struct mtx vm_daemon_mtx;
  159 /* Allow for use by vm_pageout before vm_daemon is initialized. */
  160 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
  161 #endif
  162 static int vm_max_launder = 32;
  163 static int vm_pageout_update_period;
  164 static int defer_swap_pageouts;
  165 static int disable_swap_pageouts;
  166 static int lowmem_period = 10;
  167 static int lowmem_ticks;
  168 
  169 #if defined(NO_SWAPPING)
  170 static int vm_swap_enabled = 0;
  171 static int vm_swap_idle_enabled = 0;
  172 #else
  173 static int vm_swap_enabled = 1;
  174 static int vm_swap_idle_enabled = 0;
  175 #endif
  176 
  177 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
  178         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
  179         "free page threshold for waking up the pageout daemon");
  180 
  181 SYSCTL_INT(_vm, OID_AUTO, max_launder,
  182         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
  183 
  184 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
  185         CTLFLAG_RW, &vm_pageout_update_period, 0,
  186         "Maximum active LRU update period");
  187   
  188 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
  189         "Low memory callback period");
  190 
  191 #if defined(NO_SWAPPING)
  192 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  193         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
  194 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  195         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
  196 #else
  197 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
  198         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
  199 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
  200         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
  201 #endif
  202 
  203 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
  204         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
  205 
  206 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
  207         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
  208 
  209 static int pageout_lock_miss;
  210 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
  211         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
  212 
  213 #define VM_PAGEOUT_PAGE_COUNT 16
  214 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
  215 
  216 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
  217 SYSCTL_INT(_vm, OID_AUTO, max_wired,
  218         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
  219 
  220 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
  221 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
  222     vm_paddr_t);
  223 #if !defined(NO_SWAPPING)
  224 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
  225 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
  226 static void vm_req_vmdaemon(int req);
  227 #endif
  228 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
  229 
  230 /*
  231  * Initialize a dummy page for marking the caller's place in the specified
  232  * paging queue.  In principle, this function only needs to set the flag
  233  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
  234  * to one as safety precautions.
  235  */ 
  236 static void
  237 vm_pageout_init_marker(vm_page_t marker, u_short queue)
  238 {
  239 
  240         bzero(marker, sizeof(*marker));
  241         marker->flags = PG_MARKER;
  242         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
  243         marker->queue = queue;
  244         marker->hold_count = 1;
  245 }
  246 
  247 /*
  248  * vm_pageout_fallback_object_lock:
  249  * 
  250  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
  251  * known to have failed and page queue must be either PQ_ACTIVE or
  252  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
  253  * while locking the vm object.  Use marker page to detect page queue
  254  * changes and maintain notion of next page on page queue.  Return
  255  * TRUE if no changes were detected, FALSE otherwise.  vm object is
  256  * locked on return.
  257  * 
  258  * This function depends on both the lock portion of struct vm_object
  259  * and normal struct vm_page being type stable.
  260  */
  261 static boolean_t
  262 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
  263 {
  264         struct vm_page marker;
  265         struct vm_pagequeue *pq;
  266         boolean_t unchanged;
  267         u_short queue;
  268         vm_object_t object;
  269 
  270         queue = m->queue;
  271         vm_pageout_init_marker(&marker, queue);
  272         pq = vm_page_pagequeue(m);
  273         object = m->object;
  274         
  275         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
  276         vm_pagequeue_unlock(pq);
  277         vm_page_unlock(m);
  278         VM_OBJECT_WLOCK(object);
  279         vm_page_lock(m);
  280         vm_pagequeue_lock(pq);
  281 
  282         /* Page queue might have changed. */
  283         *next = TAILQ_NEXT(&marker, plinks.q);
  284         unchanged = (m->queue == queue &&
  285                      m->object == object &&
  286                      &marker == TAILQ_NEXT(m, plinks.q));
  287         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
  288         return (unchanged);
  289 }
  290 
  291 /*
  292  * Lock the page while holding the page queue lock.  Use marker page
  293  * to detect page queue changes and maintain notion of next page on
  294  * page queue.  Return TRUE if no changes were detected, FALSE
  295  * otherwise.  The page is locked on return. The page queue lock might
  296  * be dropped and reacquired.
  297  *
  298  * This function depends on normal struct vm_page being type stable.
  299  */
  300 static boolean_t
  301 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
  302 {
  303         struct vm_page marker;
  304         struct vm_pagequeue *pq;
  305         boolean_t unchanged;
  306         u_short queue;
  307 
  308         vm_page_lock_assert(m, MA_NOTOWNED);
  309         if (vm_page_trylock(m))
  310                 return (TRUE);
  311 
  312         queue = m->queue;
  313         vm_pageout_init_marker(&marker, queue);
  314         pq = vm_page_pagequeue(m);
  315 
  316         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
  317         vm_pagequeue_unlock(pq);
  318         vm_page_lock(m);
  319         vm_pagequeue_lock(pq);
  320 
  321         /* Page queue might have changed. */
  322         *next = TAILQ_NEXT(&marker, plinks.q);
  323         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
  324         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
  325         return (unchanged);
  326 }
  327 
  328 /*
  329  * vm_pageout_clean:
  330  *
  331  * Clean the page and remove it from the laundry.
  332  * 
  333  * We set the busy bit to cause potential page faults on this page to
  334  * block.  Note the careful timing, however, the busy bit isn't set till
  335  * late and we cannot do anything that will mess with the page.
  336  */
  337 static int
  338 vm_pageout_clean(vm_page_t m)
  339 {
  340         vm_object_t object;
  341         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
  342         int pageout_count;
  343         int ib, is, page_base;
  344         vm_pindex_t pindex = m->pindex;
  345 
  346         vm_page_lock_assert(m, MA_OWNED);
  347         object = m->object;
  348         VM_OBJECT_ASSERT_WLOCKED(object);
  349 
  350         /*
  351          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
  352          * with the new swapper, but we could have serious problems paging
  353          * out other object types if there is insufficient memory.  
  354          *
  355          * Unfortunately, checking free memory here is far too late, so the
  356          * check has been moved up a procedural level.
  357          */
  358 
  359         /*
  360          * Can't clean the page if it's busy or held.
  361          */
  362         vm_page_assert_unbusied(m);
  363         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
  364         vm_page_unlock(m);
  365 
  366         mc[vm_pageout_page_count] = pb = ps = m;
  367         pageout_count = 1;
  368         page_base = vm_pageout_page_count;
  369         ib = 1;
  370         is = 1;
  371 
  372         /*
  373          * Scan object for clusterable pages.
  374          *
  375          * We can cluster ONLY if: ->> the page is NOT
  376          * clean, wired, busy, held, or mapped into a
  377          * buffer, and one of the following:
  378          * 1) The page is inactive, or a seldom used
  379          *    active page.
  380          * -or-
  381          * 2) we force the issue.
  382          *
  383          * During heavy mmap/modification loads the pageout
  384          * daemon can really fragment the underlying file
  385          * due to flushing pages out of order and not trying
  386          * align the clusters (which leave sporatic out-of-order
  387          * holes).  To solve this problem we do the reverse scan
  388          * first and attempt to align our cluster, then do a 
  389          * forward scan if room remains.
  390          */
  391 more:
  392         while (ib && pageout_count < vm_pageout_page_count) {
  393                 vm_page_t p;
  394 
  395                 if (ib > pindex) {
  396                         ib = 0;
  397                         break;
  398                 }
  399 
  400                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
  401                         ib = 0;
  402                         break;
  403                 }
  404                 vm_page_lock(p);
  405                 vm_page_test_dirty(p);
  406                 if (p->dirty == 0 ||
  407                     p->queue != PQ_INACTIVE ||
  408                     p->hold_count != 0) {       /* may be undergoing I/O */
  409                         vm_page_unlock(p);
  410                         ib = 0;
  411                         break;
  412                 }
  413                 vm_page_unlock(p);
  414                 mc[--page_base] = pb = p;
  415                 ++pageout_count;
  416                 ++ib;
  417                 /*
  418                  * alignment boundry, stop here and switch directions.  Do
  419                  * not clear ib.
  420                  */
  421                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
  422                         break;
  423         }
  424 
  425         while (pageout_count < vm_pageout_page_count && 
  426             pindex + is < object->size) {
  427                 vm_page_t p;
  428 
  429                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
  430                         break;
  431                 vm_page_lock(p);
  432                 vm_page_test_dirty(p);
  433                 if (p->dirty == 0 ||
  434                     p->queue != PQ_INACTIVE ||
  435                     p->hold_count != 0) {       /* may be undergoing I/O */
  436                         vm_page_unlock(p);
  437                         break;
  438                 }
  439                 vm_page_unlock(p);
  440                 mc[page_base + pageout_count] = ps = p;
  441                 ++pageout_count;
  442                 ++is;
  443         }
  444 
  445         /*
  446          * If we exhausted our forward scan, continue with the reverse scan
  447          * when possible, even past a page boundry.  This catches boundry
  448          * conditions.
  449          */
  450         if (ib && pageout_count < vm_pageout_page_count)
  451                 goto more;
  452 
  453         /*
  454          * we allow reads during pageouts...
  455          */
  456         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
  457             NULL));
  458 }
  459 
  460 /*
  461  * vm_pageout_flush() - launder the given pages
  462  *
  463  *      The given pages are laundered.  Note that we setup for the start of
  464  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
  465  *      reference count all in here rather then in the parent.  If we want
  466  *      the parent to do more sophisticated things we may have to change
  467  *      the ordering.
  468  *
  469  *      Returned runlen is the count of pages between mreq and first
  470  *      page after mreq with status VM_PAGER_AGAIN.
  471  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
  472  *      for any page in runlen set.
  473  */
  474 int
  475 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
  476     boolean_t *eio)
  477 {
  478         vm_object_t object = mc[0]->object;
  479         int pageout_status[count];
  480         int numpagedout = 0;
  481         int i, runlen;
  482 
  483         VM_OBJECT_ASSERT_WLOCKED(object);
  484 
  485         /*
  486          * Initiate I/O.  Bump the vm_page_t->busy counter and
  487          * mark the pages read-only.
  488          *
  489          * We do not have to fixup the clean/dirty bits here... we can
  490          * allow the pager to do it after the I/O completes.
  491          *
  492          * NOTE! mc[i]->dirty may be partial or fragmented due to an
  493          * edge case with file fragments.
  494          */
  495         for (i = 0; i < count; i++) {
  496                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
  497                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
  498                         mc[i], i, count));
  499                 vm_page_sbusy(mc[i]);
  500                 pmap_remove_write(mc[i]);
  501         }
  502         vm_object_pip_add(object, count);
  503 
  504         vm_pager_put_pages(object, mc, count, flags, pageout_status);
  505 
  506         runlen = count - mreq;
  507         if (eio != NULL)
  508                 *eio = FALSE;
  509         for (i = 0; i < count; i++) {
  510                 vm_page_t mt = mc[i];
  511 
  512                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
  513                     !pmap_page_is_write_mapped(mt),
  514                     ("vm_pageout_flush: page %p is not write protected", mt));
  515                 switch (pageout_status[i]) {
  516                 case VM_PAGER_OK:
  517                 case VM_PAGER_PEND:
  518                         numpagedout++;
  519                         break;
  520                 case VM_PAGER_BAD:
  521                         /*
  522                          * Page outside of range of object. Right now we
  523                          * essentially lose the changes by pretending it
  524                          * worked.
  525                          */
  526                         vm_page_undirty(mt);
  527                         break;
  528                 case VM_PAGER_ERROR:
  529                 case VM_PAGER_FAIL:
  530                         /*
  531                          * If page couldn't be paged out, then reactivate the
  532                          * page so it doesn't clog the inactive list.  (We
  533                          * will try paging out it again later).
  534                          */
  535                         vm_page_lock(mt);
  536                         vm_page_activate(mt);
  537                         vm_page_unlock(mt);
  538                         if (eio != NULL && i >= mreq && i - mreq < runlen)
  539                                 *eio = TRUE;
  540                         break;
  541                 case VM_PAGER_AGAIN:
  542                         if (i >= mreq && i - mreq < runlen)
  543                                 runlen = i - mreq;
  544                         break;
  545                 }
  546 
  547                 /*
  548                  * If the operation is still going, leave the page busy to
  549                  * block all other accesses. Also, leave the paging in
  550                  * progress indicator set so that we don't attempt an object
  551                  * collapse.
  552                  */
  553                 if (pageout_status[i] != VM_PAGER_PEND) {
  554                         vm_object_pip_wakeup(object);
  555                         vm_page_sunbusy(mt);
  556                         if (vm_page_count_severe()) {
  557                                 vm_page_lock(mt);
  558                                 vm_page_try_to_cache(mt);
  559                                 vm_page_unlock(mt);
  560                         }
  561                 }
  562         }
  563         if (prunlen != NULL)
  564                 *prunlen = runlen;
  565         return (numpagedout);
  566 }
  567 
  568 static boolean_t
  569 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
  570     vm_paddr_t high)
  571 {
  572         struct mount *mp;
  573         struct vnode *vp;
  574         vm_object_t object;
  575         vm_paddr_t pa;
  576         vm_page_t m, m_tmp, next;
  577         int lockmode;
  578 
  579         vm_pagequeue_lock(pq);
  580         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
  581                 if ((m->flags & PG_MARKER) != 0)
  582                         continue;
  583                 pa = VM_PAGE_TO_PHYS(m);
  584                 if (pa < low || pa + PAGE_SIZE > high)
  585                         continue;
  586                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
  587                         vm_page_unlock(m);
  588                         continue;
  589                 }
  590                 object = m->object;
  591                 if ((!VM_OBJECT_TRYWLOCK(object) &&
  592                     (!vm_pageout_fallback_object_lock(m, &next) ||
  593                     m->hold_count != 0)) || vm_page_busied(m)) {
  594                         vm_page_unlock(m);
  595                         VM_OBJECT_WUNLOCK(object);
  596                         continue;
  597                 }
  598                 vm_page_test_dirty(m);
  599                 if (m->dirty == 0 && object->ref_count != 0)
  600                         pmap_remove_all(m);
  601                 if (m->dirty != 0) {
  602                         vm_page_unlock(m);
  603                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
  604                                 VM_OBJECT_WUNLOCK(object);
  605                                 continue;
  606                         }
  607                         if (object->type == OBJT_VNODE) {
  608                                 vm_pagequeue_unlock(pq);
  609                                 vp = object->handle;
  610                                 vm_object_reference_locked(object);
  611                                 VM_OBJECT_WUNLOCK(object);
  612                                 (void)vn_start_write(vp, &mp, V_WAIT);
  613                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
  614                                     LK_SHARED : LK_EXCLUSIVE;
  615                                 vn_lock(vp, lockmode | LK_RETRY);
  616                                 VM_OBJECT_WLOCK(object);
  617                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
  618                                 VM_OBJECT_WUNLOCK(object);
  619                                 VOP_UNLOCK(vp, 0);
  620                                 vm_object_deallocate(object);
  621                                 vn_finished_write(mp);
  622                                 return (TRUE);
  623                         } else if (object->type == OBJT_SWAP ||
  624                             object->type == OBJT_DEFAULT) {
  625                                 vm_pagequeue_unlock(pq);
  626                                 m_tmp = m;
  627                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
  628                                     0, NULL, NULL);
  629                                 VM_OBJECT_WUNLOCK(object);
  630                                 return (TRUE);
  631                         }
  632                 } else {
  633                         /*
  634                          * Dequeue here to prevent lock recursion in
  635                          * vm_page_cache().
  636                          */
  637                         vm_page_dequeue_locked(m);
  638                         vm_page_cache(m);
  639                         vm_page_unlock(m);
  640                 }
  641                 VM_OBJECT_WUNLOCK(object);
  642         }
  643         vm_pagequeue_unlock(pq);
  644         return (FALSE);
  645 }
  646 
  647 /*
  648  * Increase the number of cached pages.  The specified value, "tries",
  649  * determines which categories of pages are cached:
  650  *
  651  *  0: All clean, inactive pages within the specified physical address range
  652  *     are cached.  Will not sleep.
  653  *  1: The vm_lowmem handlers are called.  All inactive pages within
  654  *     the specified physical address range are cached.  May sleep.
  655  *  2: The vm_lowmem handlers are called.  All inactive and active pages
  656  *     within the specified physical address range are cached.  May sleep.
  657  */
  658 void
  659 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
  660 {
  661         int actl, actmax, inactl, inactmax, dom, initial_dom;
  662         static int start_dom = 0;
  663 
  664         if (tries > 0) {
  665                 /*
  666                  * Decrease registered cache sizes.  The vm_lowmem handlers
  667                  * may acquire locks and/or sleep, so they can only be invoked
  668                  * when "tries" is greater than zero.
  669                  */
  670                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  671 
  672                 /*
  673                  * We do this explicitly after the caches have been drained
  674                  * above.
  675                  */
  676                 uma_reclaim();
  677         }
  678 
  679         /*
  680          * Make the next scan start on the next domain.
  681          */
  682         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
  683 
  684         inactl = 0;
  685         inactmax = vm_cnt.v_inactive_count;
  686         actl = 0;
  687         actmax = tries < 2 ? 0 : vm_cnt.v_active_count;
  688         dom = initial_dom;
  689 
  690         /*
  691          * Scan domains in round-robin order, first inactive queues,
  692          * then active.  Since domain usually owns large physically
  693          * contiguous chunk of memory, it makes sense to completely
  694          * exhaust one domain before switching to next, while growing
  695          * the pool of contiguous physical pages.
  696          *
  697          * Do not even start launder a domain which cannot contain
  698          * the specified address range, as indicated by segments
  699          * constituting the domain.
  700          */
  701 again:
  702         if (inactl < inactmax) {
  703                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
  704                     low, high) &&
  705                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
  706                     tries, low, high)) {
  707                         inactl++;
  708                         goto again;
  709                 }
  710                 if (++dom == vm_ndomains)
  711                         dom = 0;
  712                 if (dom != initial_dom)
  713                         goto again;
  714         }
  715         if (actl < actmax) {
  716                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
  717                     low, high) &&
  718                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
  719                       tries, low, high)) {
  720                         actl++;
  721                         goto again;
  722                 }
  723                 if (++dom == vm_ndomains)
  724                         dom = 0;
  725                 if (dom != initial_dom)
  726                         goto again;
  727         }
  728 }
  729 
  730 #if !defined(NO_SWAPPING)
  731 /*
  732  *      vm_pageout_object_deactivate_pages
  733  *
  734  *      Deactivate enough pages to satisfy the inactive target
  735  *      requirements.
  736  *
  737  *      The object and map must be locked.
  738  */
  739 static void
  740 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
  741     long desired)
  742 {
  743         vm_object_t backing_object, object;
  744         vm_page_t p;
  745         int act_delta, remove_mode;
  746 
  747         VM_OBJECT_ASSERT_LOCKED(first_object);
  748         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
  749                 return;
  750         for (object = first_object;; object = backing_object) {
  751                 if (pmap_resident_count(pmap) <= desired)
  752                         goto unlock_return;
  753                 VM_OBJECT_ASSERT_LOCKED(object);
  754                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
  755                     object->paging_in_progress != 0)
  756                         goto unlock_return;
  757 
  758                 remove_mode = 0;
  759                 if (object->shadow_count > 1)
  760                         remove_mode = 1;
  761                 /*
  762                  * Scan the object's entire memory queue.
  763                  */
  764                 TAILQ_FOREACH(p, &object->memq, listq) {
  765                         if (pmap_resident_count(pmap) <= desired)
  766                                 goto unlock_return;
  767                         if (vm_page_busied(p))
  768                                 continue;
  769                         PCPU_INC(cnt.v_pdpages);
  770                         vm_page_lock(p);
  771                         if (p->wire_count != 0 || p->hold_count != 0 ||
  772                             !pmap_page_exists_quick(pmap, p)) {
  773                                 vm_page_unlock(p);
  774                                 continue;
  775                         }
  776                         act_delta = pmap_ts_referenced(p);
  777                         if ((p->aflags & PGA_REFERENCED) != 0) {
  778                                 if (act_delta == 0)
  779                                         act_delta = 1;
  780                                 vm_page_aflag_clear(p, PGA_REFERENCED);
  781                         }
  782                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
  783                                 vm_page_activate(p);
  784                                 p->act_count += act_delta;
  785                         } else if (p->queue == PQ_ACTIVE) {
  786                                 if (act_delta == 0) {
  787                                         p->act_count -= min(p->act_count,
  788                                             ACT_DECLINE);
  789                                         if (!remove_mode && p->act_count == 0) {
  790                                                 pmap_remove_all(p);
  791                                                 vm_page_deactivate(p);
  792                                         } else
  793                                                 vm_page_requeue(p);
  794                                 } else {
  795                                         vm_page_activate(p);
  796                                         if (p->act_count < ACT_MAX -
  797                                             ACT_ADVANCE)
  798                                                 p->act_count += ACT_ADVANCE;
  799                                         vm_page_requeue(p);
  800                                 }
  801                         } else if (p->queue == PQ_INACTIVE)
  802                                 pmap_remove_all(p);
  803                         vm_page_unlock(p);
  804                 }
  805                 if ((backing_object = object->backing_object) == NULL)
  806                         goto unlock_return;
  807                 VM_OBJECT_RLOCK(backing_object);
  808                 if (object != first_object)
  809                         VM_OBJECT_RUNLOCK(object);
  810         }
  811 unlock_return:
  812         if (object != first_object)
  813                 VM_OBJECT_RUNLOCK(object);
  814 }
  815 
  816 /*
  817  * deactivate some number of pages in a map, try to do it fairly, but
  818  * that is really hard to do.
  819  */
  820 static void
  821 vm_pageout_map_deactivate_pages(map, desired)
  822         vm_map_t map;
  823         long desired;
  824 {
  825         vm_map_entry_t tmpe;
  826         vm_object_t obj, bigobj;
  827         int nothingwired;
  828 
  829         if (!vm_map_trylock(map))
  830                 return;
  831 
  832         bigobj = NULL;
  833         nothingwired = TRUE;
  834 
  835         /*
  836          * first, search out the biggest object, and try to free pages from
  837          * that.
  838          */
  839         tmpe = map->header.next;
  840         while (tmpe != &map->header) {
  841                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  842                         obj = tmpe->object.vm_object;
  843                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
  844                                 if (obj->shadow_count <= 1 &&
  845                                     (bigobj == NULL ||
  846                                      bigobj->resident_page_count < obj->resident_page_count)) {
  847                                         if (bigobj != NULL)
  848                                                 VM_OBJECT_RUNLOCK(bigobj);
  849                                         bigobj = obj;
  850                                 } else
  851                                         VM_OBJECT_RUNLOCK(obj);
  852                         }
  853                 }
  854                 if (tmpe->wired_count > 0)
  855                         nothingwired = FALSE;
  856                 tmpe = tmpe->next;
  857         }
  858 
  859         if (bigobj != NULL) {
  860                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
  861                 VM_OBJECT_RUNLOCK(bigobj);
  862         }
  863         /*
  864          * Next, hunt around for other pages to deactivate.  We actually
  865          * do this search sort of wrong -- .text first is not the best idea.
  866          */
  867         tmpe = map->header.next;
  868         while (tmpe != &map->header) {
  869                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
  870                         break;
  871                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
  872                         obj = tmpe->object.vm_object;
  873                         if (obj != NULL) {
  874                                 VM_OBJECT_RLOCK(obj);
  875                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
  876                                 VM_OBJECT_RUNLOCK(obj);
  877                         }
  878                 }
  879                 tmpe = tmpe->next;
  880         }
  881 
  882         /*
  883          * Remove all mappings if a process is swapped out, this will free page
  884          * table pages.
  885          */
  886         if (desired == 0 && nothingwired) {
  887                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
  888                     vm_map_max(map));
  889         }
  890 
  891         vm_map_unlock(map);
  892 }
  893 #endif          /* !defined(NO_SWAPPING) */
  894 
  895 /*
  896  *      vm_pageout_scan does the dirty work for the pageout daemon.
  897  *
  898  *      pass 0 - Update active LRU/deactivate pages
  899  *      pass 1 - Move inactive to cache or free
  900  *      pass 2 - Launder dirty pages
  901  */
  902 static void
  903 vm_pageout_scan(struct vm_domain *vmd, int pass)
  904 {
  905         vm_page_t m, next;
  906         struct vm_pagequeue *pq;
  907         vm_object_t object;
  908         int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
  909         int vnodes_skipped = 0;
  910         int maxlaunder;
  911         int lockmode;
  912         boolean_t queues_locked;
  913 
  914         /*
  915          * If we need to reclaim memory ask kernel caches to return
  916          * some.  We rate limit to avoid thrashing.
  917          */
  918         if (vmd == &vm_dom[0] && pass > 0 &&
  919             lowmem_ticks + (lowmem_period * hz) < ticks) {
  920                 /*
  921                  * Decrease registered cache sizes.
  922                  */
  923                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  924                 /*
  925                  * We do this explicitly after the caches have been
  926                  * drained above.
  927                  */
  928                 uma_reclaim();
  929                 lowmem_ticks = ticks;
  930         }
  931 
  932         /*
  933          * The addl_page_shortage is the number of temporarily
  934          * stuck pages in the inactive queue.  In other words, the
  935          * number of pages from the inactive count that should be
  936          * discounted in setting the target for the active queue scan.
  937          */
  938         addl_page_shortage = 0;
  939 
  940         /*
  941          * Calculate the number of pages we want to either free or move
  942          * to the cache.
  943          */
  944         if (pass > 0) {
  945                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
  946                 page_shortage = vm_paging_target() + deficit;
  947         } else
  948                 page_shortage = deficit = 0;
  949 
  950         /*
  951          * maxlaunder limits the number of dirty pages we flush per scan.
  952          * For most systems a smaller value (16 or 32) is more robust under
  953          * extreme memory and disk pressure because any unnecessary writes
  954          * to disk can result in extreme performance degredation.  However,
  955          * systems with excessive dirty pages (especially when MAP_NOSYNC is
  956          * used) will die horribly with limited laundering.  If the pageout
  957          * daemon cannot clean enough pages in the first pass, we let it go
  958          * all out in succeeding passes.
  959          */
  960         if ((maxlaunder = vm_max_launder) <= 1)
  961                 maxlaunder = 1;
  962         if (pass > 1)
  963                 maxlaunder = 10000;
  964 
  965         /*
  966          * Start scanning the inactive queue for pages we can move to the
  967          * cache or free.  The scan will stop when the target is reached or
  968          * we have scanned the entire inactive queue.  Note that m->act_count
  969          * is not used to form decisions for the inactive queue, only for the
  970          * active queue.
  971          */
  972         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
  973         maxscan = pq->pq_cnt;
  974         vm_pagequeue_lock(pq);
  975         queues_locked = TRUE;
  976         for (m = TAILQ_FIRST(&pq->pq_pl);
  977              m != NULL && maxscan-- > 0 && page_shortage > 0;
  978              m = next) {
  979                 vm_pagequeue_assert_locked(pq);
  980                 KASSERT(queues_locked, ("unlocked queues"));
  981                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
  982 
  983                 PCPU_INC(cnt.v_pdpages);
  984                 next = TAILQ_NEXT(m, plinks.q);
  985 
  986                 /*
  987                  * skip marker pages
  988                  */
  989                 if (m->flags & PG_MARKER)
  990                         continue;
  991 
  992                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
  993                     ("Fictitious page %p cannot be in inactive queue", m));
  994                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
  995                     ("Unmanaged page %p cannot be in inactive queue", m));
  996 
  997                 /*
  998                  * The page or object lock acquisitions fail if the
  999                  * page was removed from the queue or moved to a
 1000                  * different position within the queue.  In either
 1001                  * case, addl_page_shortage should not be incremented.
 1002                  */
 1003                 if (!vm_pageout_page_lock(m, &next)) {
 1004                         vm_page_unlock(m);
 1005                         continue;
 1006                 }
 1007                 object = m->object;
 1008                 if (!VM_OBJECT_TRYWLOCK(object) &&
 1009                     !vm_pageout_fallback_object_lock(m, &next)) {
 1010                         vm_page_unlock(m);
 1011                         VM_OBJECT_WUNLOCK(object);
 1012                         continue;
 1013                 }
 1014 
 1015                 /*
 1016                  * Don't mess with busy pages, keep them at at the
 1017                  * front of the queue, most likely they are being
 1018                  * paged out.  Increment addl_page_shortage for busy
 1019                  * pages, because they may leave the inactive queue
 1020                  * shortly after page scan is finished.
 1021                  */
 1022                 if (vm_page_busied(m)) {
 1023                         vm_page_unlock(m);
 1024                         VM_OBJECT_WUNLOCK(object);
 1025                         addl_page_shortage++;
 1026                         continue;
 1027                 }
 1028 
 1029                 /*
 1030                  * We unlock the inactive page queue, invalidating the
 1031                  * 'next' pointer.  Use our marker to remember our
 1032                  * place.
 1033                  */
 1034                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
 1035                 vm_pagequeue_unlock(pq);
 1036                 queues_locked = FALSE;
 1037 
 1038                 /*
 1039                  * We bump the activation count if the page has been
 1040                  * referenced while in the inactive queue.  This makes
 1041                  * it less likely that the page will be added back to the
 1042                  * inactive queue prematurely again.  Here we check the 
 1043                  * page tables (or emulated bits, if any), given the upper 
 1044                  * level VM system not knowing anything about existing 
 1045                  * references.
 1046                  */
 1047                 if ((m->aflags & PGA_REFERENCED) != 0) {
 1048                         vm_page_aflag_clear(m, PGA_REFERENCED);
 1049                         act_delta = 1;
 1050                 } else
 1051                         act_delta = 0;
 1052                 if (object->ref_count != 0) {
 1053                         act_delta += pmap_ts_referenced(m);
 1054                 } else {
 1055                         KASSERT(!pmap_page_is_mapped(m),
 1056                             ("vm_pageout_scan: page %p is mapped", m));
 1057                 }
 1058 
 1059                 /*
 1060                  * If the upper level VM system knows about any page 
 1061                  * references, we reactivate the page or requeue it.
 1062                  */
 1063                 if (act_delta != 0) {
 1064                         if (object->ref_count != 0) {
 1065                                 vm_page_activate(m);
 1066                                 m->act_count += act_delta + ACT_ADVANCE;
 1067                         } else {
 1068                                 vm_pagequeue_lock(pq);
 1069                                 queues_locked = TRUE;
 1070                                 vm_page_requeue_locked(m);
 1071                         }
 1072                         VM_OBJECT_WUNLOCK(object);
 1073                         vm_page_unlock(m);
 1074                         goto relock_queues;
 1075                 }
 1076 
 1077                 if (m->hold_count != 0) {
 1078                         vm_page_unlock(m);
 1079                         VM_OBJECT_WUNLOCK(object);
 1080 
 1081                         /*
 1082                          * Held pages are essentially stuck in the
 1083                          * queue.  So, they ought to be discounted
 1084                          * from the inactive count.  See the
 1085                          * calculation of the page_shortage for the
 1086                          * loop over the active queue below.
 1087                          */
 1088                         addl_page_shortage++;
 1089                         goto relock_queues;
 1090                 }
 1091 
 1092                 /*
 1093                  * If the page appears to be clean at the machine-independent
 1094                  * layer, then remove all of its mappings from the pmap in
 1095                  * anticipation of placing it onto the cache queue.  If,
 1096                  * however, any of the page's mappings allow write access,
 1097                  * then the page may still be modified until the last of those
 1098                  * mappings are removed.
 1099                  */
 1100                 vm_page_test_dirty(m);
 1101                 if (m->dirty == 0 && object->ref_count != 0)
 1102                         pmap_remove_all(m);
 1103 
 1104                 if (m->valid == 0) {
 1105                         /*
 1106                          * Invalid pages can be easily freed
 1107                          */
 1108                         vm_page_free(m);
 1109                         PCPU_INC(cnt.v_dfree);
 1110                         --page_shortage;
 1111                 } else if (m->dirty == 0) {
 1112                         /*
 1113                          * Clean pages can be placed onto the cache queue.
 1114                          * This effectively frees them.
 1115                          */
 1116                         vm_page_cache(m);
 1117                         --page_shortage;
 1118                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
 1119                         /*
 1120                          * Dirty pages need to be paged out, but flushing
 1121                          * a page is extremely expensive versus freeing
 1122                          * a clean page.  Rather then artificially limiting
 1123                          * the number of pages we can flush, we instead give
 1124                          * dirty pages extra priority on the inactive queue
 1125                          * by forcing them to be cycled through the queue
 1126                          * twice before being flushed, after which the
 1127                          * (now clean) page will cycle through once more
 1128                          * before being freed.  This significantly extends
 1129                          * the thrash point for a heavily loaded machine.
 1130                          */
 1131                         m->flags |= PG_WINATCFLS;
 1132                         vm_pagequeue_lock(pq);
 1133                         queues_locked = TRUE;
 1134                         vm_page_requeue_locked(m);
 1135                 } else if (maxlaunder > 0) {
 1136                         /*
 1137                          * We always want to try to flush some dirty pages if
 1138                          * we encounter them, to keep the system stable.
 1139                          * Normally this number is small, but under extreme
 1140                          * pressure where there are insufficient clean pages
 1141                          * on the inactive queue, we may have to go all out.
 1142                          */
 1143                         int swap_pageouts_ok;
 1144                         struct vnode *vp = NULL;
 1145                         struct mount *mp = NULL;
 1146 
 1147                         if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
 1148                                 swap_pageouts_ok = 1;
 1149                         } else {
 1150                                 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
 1151                                 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
 1152                                 vm_page_count_min());
 1153                                                                                 
 1154                         }
 1155 
 1156                         /*
 1157                          * We don't bother paging objects that are "dead".  
 1158                          * Those objects are in a "rundown" state.
 1159                          */
 1160                         if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
 1161                                 vm_pagequeue_lock(pq);
 1162                                 vm_page_unlock(m);
 1163                                 VM_OBJECT_WUNLOCK(object);
 1164                                 queues_locked = TRUE;
 1165                                 vm_page_requeue_locked(m);
 1166                                 goto relock_queues;
 1167                         }
 1168 
 1169                         /*
 1170                          * The object is already known NOT to be dead.   It
 1171                          * is possible for the vget() to block the whole
 1172                          * pageout daemon, but the new low-memory handling
 1173                          * code should prevent it.
 1174                          *
 1175                          * The previous code skipped locked vnodes and, worse,
 1176                          * reordered pages in the queue.  This results in
 1177                          * completely non-deterministic operation and, on a
 1178                          * busy system, can lead to extremely non-optimal
 1179                          * pageouts.  For example, it can cause clean pages
 1180                          * to be freed and dirty pages to be moved to the end
 1181                          * of the queue.  Since dirty pages are also moved to
 1182                          * the end of the queue once-cleaned, this gives
 1183                          * way too large a weighting to deferring the freeing
 1184                          * of dirty pages.
 1185                          *
 1186                          * We can't wait forever for the vnode lock, we might
 1187                          * deadlock due to a vn_read() getting stuck in
 1188                          * vm_wait while holding this vnode.  We skip the 
 1189                          * vnode if we can't get it in a reasonable amount
 1190                          * of time.
 1191                          */
 1192                         if (object->type == OBJT_VNODE) {
 1193                                 vm_page_unlock(m);
 1194                                 vp = object->handle;
 1195                                 if (vp->v_type == VREG &&
 1196                                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 1197                                         mp = NULL;
 1198                                         ++pageout_lock_miss;
 1199                                         if (object->flags & OBJ_MIGHTBEDIRTY)
 1200                                                 vnodes_skipped++;
 1201                                         goto unlock_and_continue;
 1202                                 }
 1203                                 KASSERT(mp != NULL,
 1204                                     ("vp %p with NULL v_mount", vp));
 1205                                 vm_object_reference_locked(object);
 1206                                 VM_OBJECT_WUNLOCK(object);
 1207                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 1208                                     LK_SHARED : LK_EXCLUSIVE;
 1209                                 if (vget(vp, lockmode | LK_TIMELOCK,
 1210                                     curthread)) {
 1211                                         VM_OBJECT_WLOCK(object);
 1212                                         ++pageout_lock_miss;
 1213                                         if (object->flags & OBJ_MIGHTBEDIRTY)
 1214                                                 vnodes_skipped++;
 1215                                         vp = NULL;
 1216                                         goto unlock_and_continue;
 1217                                 }
 1218                                 VM_OBJECT_WLOCK(object);
 1219                                 vm_page_lock(m);
 1220                                 vm_pagequeue_lock(pq);
 1221                                 queues_locked = TRUE;
 1222                                 /*
 1223                                  * The page might have been moved to another
 1224                                  * queue during potential blocking in vget()
 1225                                  * above.  The page might have been freed and
 1226                                  * reused for another vnode.
 1227                                  */
 1228                                 if (m->queue != PQ_INACTIVE ||
 1229                                     m->object != object ||
 1230                                     TAILQ_NEXT(m, plinks.q) != &vmd->vmd_marker) {
 1231                                         vm_page_unlock(m);
 1232                                         if (object->flags & OBJ_MIGHTBEDIRTY)
 1233                                                 vnodes_skipped++;
 1234                                         goto unlock_and_continue;
 1235                                 }
 1236         
 1237                                 /*
 1238                                  * The page may have been busied during the
 1239                                  * blocking in vget().  We don't move the
 1240                                  * page back onto the end of the queue so that
 1241                                  * statistics are more correct if we don't.
 1242                                  */
 1243                                 if (vm_page_busied(m)) {
 1244                                         vm_page_unlock(m);
 1245                                         addl_page_shortage++;
 1246                                         goto unlock_and_continue;
 1247                                 }
 1248 
 1249                                 /*
 1250                                  * If the page has become held it might
 1251                                  * be undergoing I/O, so skip it
 1252                                  */
 1253                                 if (m->hold_count != 0) {
 1254                                         vm_page_unlock(m);
 1255                                         addl_page_shortage++;
 1256                                         if (object->flags & OBJ_MIGHTBEDIRTY)
 1257                                                 vnodes_skipped++;
 1258                                         goto unlock_and_continue;
 1259                                 }
 1260                                 vm_pagequeue_unlock(pq);
 1261                                 queues_locked = FALSE;
 1262                         }
 1263 
 1264                         /*
 1265                          * If a page is dirty, then it is either being washed
 1266                          * (but not yet cleaned) or it is still in the
 1267                          * laundry.  If it is still in the laundry, then we
 1268                          * start the cleaning operation. 
 1269                          *
 1270                          * decrement page_shortage on success to account for
 1271                          * the (future) cleaned page.  Otherwise we could wind
 1272                          * up laundering or cleaning too many pages.
 1273                          */
 1274                         if (vm_pageout_clean(m) != 0) {
 1275                                 --page_shortage;
 1276                                 --maxlaunder;
 1277                         }
 1278 unlock_and_continue:
 1279                         vm_page_lock_assert(m, MA_NOTOWNED);
 1280                         VM_OBJECT_WUNLOCK(object);
 1281                         if (mp != NULL) {
 1282                                 if (queues_locked) {
 1283                                         vm_pagequeue_unlock(pq);
 1284                                         queues_locked = FALSE;
 1285                                 }
 1286                                 if (vp != NULL)
 1287                                         vput(vp);
 1288                                 vm_object_deallocate(object);
 1289                                 vn_finished_write(mp);
 1290                         }
 1291                         vm_page_lock_assert(m, MA_NOTOWNED);
 1292                         goto relock_queues;
 1293                 }
 1294                 vm_page_unlock(m);
 1295                 VM_OBJECT_WUNLOCK(object);
 1296 relock_queues:
 1297                 if (!queues_locked) {
 1298                         vm_pagequeue_lock(pq);
 1299                         queues_locked = TRUE;
 1300                 }
 1301                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
 1302                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
 1303         }
 1304         vm_pagequeue_unlock(pq);
 1305 
 1306 #if !defined(NO_SWAPPING)
 1307         /*
 1308          * Wakeup the swapout daemon if we didn't cache or free the targeted
 1309          * number of pages. 
 1310          */
 1311         if (vm_swap_enabled && page_shortage > 0)
 1312                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 1313 #endif
 1314 
 1315         /*
 1316          * Wakeup the sync daemon if we skipped a vnode in a writeable object
 1317          * and we didn't cache or free enough pages.
 1318          */
 1319         if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target -
 1320             vm_cnt.v_free_min)
 1321                 (void)speedup_syncer();
 1322 
 1323         /*
 1324          * Compute the number of pages we want to try to move from the
 1325          * active queue to the inactive queue.
 1326          */
 1327         page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count +
 1328             vm_paging_target() + deficit + addl_page_shortage;
 1329 
 1330         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
 1331         vm_pagequeue_lock(pq);
 1332         maxscan = pq->pq_cnt;
 1333 
 1334         /*
 1335          * If we're just idle polling attempt to visit every
 1336          * active page within 'update_period' seconds.
 1337          */
 1338         if (pass == 0 && vm_pageout_update_period != 0) {
 1339                 maxscan /= vm_pageout_update_period;
 1340                 page_shortage = maxscan;
 1341         }
 1342 
 1343         /*
 1344          * Scan the active queue for things we can deactivate. We nominally
 1345          * track the per-page activity counter and use it to locate
 1346          * deactivation candidates.
 1347          */
 1348         m = TAILQ_FIRST(&pq->pq_pl);
 1349         while (m != NULL && maxscan-- > 0 && page_shortage > 0) {
 1350 
 1351                 KASSERT(m->queue == PQ_ACTIVE,
 1352                     ("vm_pageout_scan: page %p isn't active", m));
 1353 
 1354                 next = TAILQ_NEXT(m, plinks.q);
 1355                 if ((m->flags & PG_MARKER) != 0) {
 1356                         m = next;
 1357                         continue;
 1358                 }
 1359                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 1360                     ("Fictitious page %p cannot be in active queue", m));
 1361                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 1362                     ("Unmanaged page %p cannot be in active queue", m));
 1363                 if (!vm_pageout_page_lock(m, &next)) {
 1364                         vm_page_unlock(m);
 1365                         m = next;
 1366                         continue;
 1367                 }
 1368 
 1369                 /*
 1370                  * The count for pagedaemon pages is done after checking the
 1371                  * page for eligibility...
 1372                  */
 1373                 PCPU_INC(cnt.v_pdpages);
 1374 
 1375                 /*
 1376                  * Check to see "how much" the page has been used.
 1377                  */
 1378                 if ((m->aflags & PGA_REFERENCED) != 0) {
 1379                         vm_page_aflag_clear(m, PGA_REFERENCED);
 1380                         act_delta = 1;
 1381                 } else
 1382                         act_delta = 0;
 1383 
 1384                 /*
 1385                  * Unlocked object ref count check.  Two races are possible.
 1386                  * 1) The ref was transitioning to zero and we saw non-zero,
 1387                  *    the pmap bits will be checked unnecessarily.
 1388                  * 2) The ref was transitioning to one and we saw zero. 
 1389                  *    The page lock prevents a new reference to this page so
 1390                  *    we need not check the reference bits.
 1391                  */
 1392                 if (m->object->ref_count != 0)
 1393                         act_delta += pmap_ts_referenced(m);
 1394 
 1395                 /*
 1396                  * Advance or decay the act_count based on recent usage.
 1397                  */
 1398                 if (act_delta != 0) {
 1399                         m->act_count += ACT_ADVANCE + act_delta;
 1400                         if (m->act_count > ACT_MAX)
 1401                                 m->act_count = ACT_MAX;
 1402                 } else
 1403                         m->act_count -= min(m->act_count, ACT_DECLINE);
 1404 
 1405                 /*
 1406                  * Move this page to the tail of the active or inactive
 1407                  * queue depending on usage.
 1408                  */
 1409                 if (m->act_count == 0) {
 1410                         /* Dequeue to avoid later lock recursion. */
 1411                         vm_page_dequeue_locked(m);
 1412                         vm_page_deactivate(m);
 1413                         page_shortage--;
 1414                 } else
 1415                         vm_page_requeue_locked(m);
 1416                 vm_page_unlock(m);
 1417                 m = next;
 1418         }
 1419         vm_pagequeue_unlock(pq);
 1420 #if !defined(NO_SWAPPING)
 1421         /*
 1422          * Idle process swapout -- run once per second.
 1423          */
 1424         if (vm_swap_idle_enabled) {
 1425                 static long lsec;
 1426                 if (time_second != lsec) {
 1427                         vm_req_vmdaemon(VM_SWAP_IDLE);
 1428                         lsec = time_second;
 1429                 }
 1430         }
 1431 #endif
 1432 
 1433         /*
 1434          * If we are critically low on one of RAM or swap and low on
 1435          * the other, kill the largest process.  However, we avoid
 1436          * doing this on the first pass in order to give ourselves a
 1437          * chance to flush out dirty vnode-backed pages and to allow
 1438          * active pages to be moved to the inactive queue and reclaimed.
 1439          */
 1440         vm_pageout_mightbe_oom(vmd, pass);
 1441 }
 1442 
 1443 static int vm_pageout_oom_vote;
 1444 
 1445 /*
 1446  * The pagedaemon threads randlomly select one to perform the
 1447  * OOM.  Trying to kill processes before all pagedaemons
 1448  * failed to reach free target is premature.
 1449  */
 1450 static void
 1451 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
 1452 {
 1453         int old_vote;
 1454 
 1455         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
 1456             (swap_pager_full && vm_paging_target() > 0))) {
 1457                 if (vmd->vmd_oom) {
 1458                         vmd->vmd_oom = FALSE;
 1459                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
 1460                 }
 1461                 return;
 1462         }
 1463 
 1464         if (vmd->vmd_oom)
 1465                 return;
 1466 
 1467         vmd->vmd_oom = TRUE;
 1468         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
 1469         if (old_vote != vm_ndomains - 1)
 1470                 return;
 1471 
 1472         /*
 1473          * The current pagedaemon thread is the last in the quorum to
 1474          * start OOM.  Initiate the selection and signaling of the
 1475          * victim.
 1476          */
 1477         vm_pageout_oom(VM_OOM_MEM);
 1478 
 1479         /*
 1480          * After one round of OOM terror, recall our vote.  On the
 1481          * next pass, current pagedaemon would vote again if the low
 1482          * memory condition is still there, due to vmd_oom being
 1483          * false.
 1484          */
 1485         vmd->vmd_oom = FALSE;
 1486         atomic_subtract_int(&vm_pageout_oom_vote, 1);
 1487 }
 1488 
 1489 void
 1490 vm_pageout_oom(int shortage)
 1491 {
 1492         struct proc *p, *bigproc;
 1493         vm_offset_t size, bigsize;
 1494         struct thread *td;
 1495         struct vmspace *vm;
 1496 
 1497         /*
 1498          * We keep the process bigproc locked once we find it to keep anyone
 1499          * from messing with it; however, there is a possibility of
 1500          * deadlock if process B is bigproc and one of it's child processes
 1501          * attempts to propagate a signal to B while we are waiting for A's
 1502          * lock while walking this list.  To avoid this, we don't block on
 1503          * the process lock but just skip a process if it is already locked.
 1504          */
 1505         bigproc = NULL;
 1506         bigsize = 0;
 1507         sx_slock(&allproc_lock);
 1508         FOREACH_PROC_IN_SYSTEM(p) {
 1509                 int breakout;
 1510 
 1511                 if (PROC_TRYLOCK(p) == 0)
 1512                         continue;
 1513                 /*
 1514                  * If this is a system, protected or killed process, skip it.
 1515                  */
 1516                 if (p->p_state != PRS_NORMAL ||
 1517                     (p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
 1518                     (p->p_pid == 1) || P_KILLED(p) ||
 1519                     ((p->p_pid < 48) && (swap_pager_avail != 0))) {
 1520                         PROC_UNLOCK(p);
 1521                         continue;
 1522                 }
 1523                 /*
 1524                  * If the process is in a non-running type state,
 1525                  * don't touch it.  Check all the threads individually.
 1526                  */
 1527                 breakout = 0;
 1528                 FOREACH_THREAD_IN_PROC(p, td) {
 1529                         thread_lock(td);
 1530                         if (!TD_ON_RUNQ(td) &&
 1531                             !TD_IS_RUNNING(td) &&
 1532                             !TD_IS_SLEEPING(td) &&
 1533                             !TD_IS_SUSPENDED(td)) {
 1534                                 thread_unlock(td);
 1535                                 breakout = 1;
 1536                                 break;
 1537                         }
 1538                         thread_unlock(td);
 1539                 }
 1540                 if (breakout) {
 1541                         PROC_UNLOCK(p);
 1542                         continue;
 1543                 }
 1544                 /*
 1545                  * get the process size
 1546                  */
 1547                 vm = vmspace_acquire_ref(p);
 1548                 if (vm == NULL) {
 1549                         PROC_UNLOCK(p);
 1550                         continue;
 1551                 }
 1552                 if (!vm_map_trylock_read(&vm->vm_map)) {
 1553                         vmspace_free(vm);
 1554                         PROC_UNLOCK(p);
 1555                         continue;
 1556                 }
 1557                 size = vmspace_swap_count(vm);
 1558                 vm_map_unlock_read(&vm->vm_map);
 1559                 if (shortage == VM_OOM_MEM)
 1560                         size += vmspace_resident_count(vm);
 1561                 vmspace_free(vm);
 1562                 /*
 1563                  * if the this process is bigger than the biggest one
 1564                  * remember it.
 1565                  */
 1566                 if (size > bigsize) {
 1567                         if (bigproc != NULL)
 1568                                 PROC_UNLOCK(bigproc);
 1569                         bigproc = p;
 1570                         bigsize = size;
 1571                 } else
 1572                         PROC_UNLOCK(p);
 1573         }
 1574         sx_sunlock(&allproc_lock);
 1575         if (bigproc != NULL) {
 1576                 killproc(bigproc, "out of swap space");
 1577                 sched_nice(bigproc, PRIO_MIN);
 1578                 PROC_UNLOCK(bigproc);
 1579                 wakeup(&vm_cnt.v_free_count);
 1580         }
 1581 }
 1582 
 1583 static void
 1584 vm_pageout_worker(void *arg)
 1585 {
 1586         struct vm_domain *domain;
 1587         int domidx;
 1588 
 1589         domidx = (uintptr_t)arg;
 1590         domain = &vm_dom[domidx];
 1591 
 1592         /*
 1593          * XXXKIB It could be useful to bind pageout daemon threads to
 1594          * the cores belonging to the domain, from which vm_page_array
 1595          * is allocated.
 1596          */
 1597 
 1598         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
 1599         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
 1600 
 1601         /*
 1602          * The pageout daemon worker is never done, so loop forever.
 1603          */
 1604         while (TRUE) {
 1605                 /*
 1606                  * If we have enough free memory, wakeup waiters.  Do
 1607                  * not clear vm_pages_needed until we reach our target,
 1608                  * otherwise we may be woken up over and over again and
 1609                  * waste a lot of cpu.
 1610                  */
 1611                 mtx_lock(&vm_page_queue_free_mtx);
 1612                 if (vm_pages_needed && !vm_page_count_min()) {
 1613                         if (!vm_paging_needed())
 1614                                 vm_pages_needed = 0;
 1615                         wakeup(&vm_cnt.v_free_count);
 1616                 }
 1617                 if (vm_pages_needed) {
 1618                         /*
 1619                          * Still not done, take a second pass without waiting
 1620                          * (unlimited dirty cleaning), otherwise sleep a bit
 1621                          * and try again.
 1622                          */
 1623                         if (domain->vmd_pass > 1)
 1624                                 msleep(&vm_pages_needed,
 1625                                     &vm_page_queue_free_mtx, PVM, "psleep",
 1626                                     hz / 2);
 1627                 } else {
 1628                         /*
 1629                          * Good enough, sleep until required to refresh
 1630                          * stats.
 1631                          */
 1632                         domain->vmd_pass = 0;
 1633                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
 1634                             PVM, "psleep", hz);
 1635 
 1636                 }
 1637                 if (vm_pages_needed) {
 1638                         vm_cnt.v_pdwakeups++;
 1639                         domain->vmd_pass++;
 1640                 }
 1641                 mtx_unlock(&vm_page_queue_free_mtx);
 1642                 vm_pageout_scan(domain, domain->vmd_pass);
 1643         }
 1644 }
 1645 
 1646 /*
 1647  *      vm_pageout_init initialises basic pageout daemon settings.
 1648  */
 1649 static void
 1650 vm_pageout_init(void)
 1651 {
 1652         /*
 1653          * Initialize some paging parameters.
 1654          */
 1655         vm_cnt.v_interrupt_free_min = 2;
 1656         if (vm_cnt.v_page_count < 2000)
 1657                 vm_pageout_page_count = 8;
 1658 
 1659         /*
 1660          * v_free_reserved needs to include enough for the largest
 1661          * swap pager structures plus enough for any pv_entry structs
 1662          * when paging. 
 1663          */
 1664         if (vm_cnt.v_page_count > 1024)
 1665                 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
 1666         else
 1667                 vm_cnt.v_free_min = 4;
 1668         vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
 1669             vm_cnt.v_interrupt_free_min;
 1670         vm_cnt.v_free_reserved = vm_pageout_page_count +
 1671             vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
 1672         vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
 1673         vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
 1674         vm_cnt.v_free_min += vm_cnt.v_free_reserved;
 1675         vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
 1676         vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
 1677         if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
 1678                 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
 1679 
 1680         /*
 1681          * Set the default wakeup threshold to be 10% above the minimum
 1682          * page limit.  This keeps the steady state out of shortfall.
 1683          */
 1684         vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
 1685 
 1686         /*
 1687          * Set interval in seconds for active scan.  We want to visit each
 1688          * page at least once every ten minutes.  This is to prevent worst
 1689          * case paging behaviors with stale active LRU.
 1690          */
 1691         if (vm_pageout_update_period == 0)
 1692                 vm_pageout_update_period = 600;
 1693 
 1694         /* XXX does not really belong here */
 1695         if (vm_page_max_wired == 0)
 1696                 vm_page_max_wired = vm_cnt.v_free_count / 3;
 1697 }
 1698 
 1699 /*
 1700  *     vm_pageout is the high level pageout daemon.
 1701  */
 1702 static void
 1703 vm_pageout(void)
 1704 {
 1705 #if MAXMEMDOM > 1
 1706         int error, i;
 1707 #endif
 1708 
 1709         swap_pager_swap_init();
 1710 #if MAXMEMDOM > 1
 1711         for (i = 1; i < vm_ndomains; i++) {
 1712                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
 1713                     curproc, NULL, 0, 0, "dom%d", i);
 1714                 if (error != 0) {
 1715                         panic("starting pageout for domain %d, error %d\n",
 1716                             i, error);
 1717                 }
 1718         }
 1719 #endif
 1720         vm_pageout_worker((void *)(uintptr_t)0);
 1721 }
 1722 
 1723 /*
 1724  * Unless the free page queue lock is held by the caller, this function
 1725  * should be regarded as advisory.  Specifically, the caller should
 1726  * not msleep() on &vm_cnt.v_free_count following this function unless
 1727  * the free page queue lock is held until the msleep() is performed.
 1728  */
 1729 void
 1730 pagedaemon_wakeup(void)
 1731 {
 1732 
 1733         if (!vm_pages_needed && curthread->td_proc != pageproc) {
 1734                 vm_pages_needed = 1;
 1735                 wakeup(&vm_pages_needed);
 1736         }
 1737 }
 1738 
 1739 #if !defined(NO_SWAPPING)
 1740 static void
 1741 vm_req_vmdaemon(int req)
 1742 {
 1743         static int lastrun = 0;
 1744 
 1745         mtx_lock(&vm_daemon_mtx);
 1746         vm_pageout_req_swapout |= req;
 1747         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 1748                 wakeup(&vm_daemon_needed);
 1749                 lastrun = ticks;
 1750         }
 1751         mtx_unlock(&vm_daemon_mtx);
 1752 }
 1753 
 1754 static void
 1755 vm_daemon(void)
 1756 {
 1757         struct rlimit rsslim;
 1758         struct proc *p;
 1759         struct thread *td;
 1760         struct vmspace *vm;
 1761         int breakout, swapout_flags, tryagain, attempts;
 1762 #ifdef RACCT
 1763         uint64_t rsize, ravailable;
 1764 #endif
 1765 
 1766         while (TRUE) {
 1767                 mtx_lock(&vm_daemon_mtx);
 1768 #ifdef RACCT
 1769                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
 1770 #else
 1771                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
 1772 #endif
 1773                 swapout_flags = vm_pageout_req_swapout;
 1774                 vm_pageout_req_swapout = 0;
 1775                 mtx_unlock(&vm_daemon_mtx);
 1776                 if (swapout_flags)
 1777                         swapout_procs(swapout_flags);
 1778 
 1779                 /*
 1780                  * scan the processes for exceeding their rlimits or if
 1781                  * process is swapped out -- deactivate pages
 1782                  */
 1783                 tryagain = 0;
 1784                 attempts = 0;
 1785 again:
 1786                 attempts++;
 1787                 sx_slock(&allproc_lock);
 1788                 FOREACH_PROC_IN_SYSTEM(p) {
 1789                         vm_pindex_t limit, size;
 1790 
 1791                         /*
 1792                          * if this is a system process or if we have already
 1793                          * looked at this process, skip it.
 1794                          */
 1795                         PROC_LOCK(p);
 1796                         if (p->p_state != PRS_NORMAL ||
 1797                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 1798                                 PROC_UNLOCK(p);
 1799                                 continue;
 1800                         }
 1801                         /*
 1802                          * if the process is in a non-running type state,
 1803                          * don't touch it.
 1804                          */
 1805                         breakout = 0;
 1806                         FOREACH_THREAD_IN_PROC(p, td) {
 1807                                 thread_lock(td);
 1808                                 if (!TD_ON_RUNQ(td) &&
 1809                                     !TD_IS_RUNNING(td) &&
 1810                                     !TD_IS_SLEEPING(td) &&
 1811                                     !TD_IS_SUSPENDED(td)) {
 1812                                         thread_unlock(td);
 1813                                         breakout = 1;
 1814                                         break;
 1815                                 }
 1816                                 thread_unlock(td);
 1817                         }
 1818                         if (breakout) {
 1819                                 PROC_UNLOCK(p);
 1820                                 continue;
 1821                         }
 1822                         /*
 1823                          * get a limit
 1824                          */
 1825                         lim_rlimit(p, RLIMIT_RSS, &rsslim);
 1826                         limit = OFF_TO_IDX(
 1827                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 1828 
 1829                         /*
 1830                          * let processes that are swapped out really be
 1831                          * swapped out set the limit to nothing (will force a
 1832                          * swap-out.)
 1833                          */
 1834                         if ((p->p_flag & P_INMEM) == 0)
 1835                                 limit = 0;      /* XXX */
 1836                         vm = vmspace_acquire_ref(p);
 1837                         PROC_UNLOCK(p);
 1838                         if (vm == NULL)
 1839                                 continue;
 1840 
 1841                         size = vmspace_resident_count(vm);
 1842                         if (size >= limit) {
 1843                                 vm_pageout_map_deactivate_pages(
 1844                                     &vm->vm_map, limit);
 1845                         }
 1846 #ifdef RACCT
 1847                         rsize = IDX_TO_OFF(size);
 1848                         PROC_LOCK(p);
 1849                         racct_set(p, RACCT_RSS, rsize);
 1850                         ravailable = racct_get_available(p, RACCT_RSS);
 1851                         PROC_UNLOCK(p);
 1852                         if (rsize > ravailable) {
 1853                                 /*
 1854                                  * Don't be overly aggressive; this might be
 1855                                  * an innocent process, and the limit could've
 1856                                  * been exceeded by some memory hog.  Don't
 1857                                  * try to deactivate more than 1/4th of process'
 1858                                  * resident set size.
 1859                                  */
 1860                                 if (attempts <= 8) {
 1861                                         if (ravailable < rsize - (rsize / 4))
 1862                                                 ravailable = rsize - (rsize / 4);
 1863                                 }
 1864                                 vm_pageout_map_deactivate_pages(
 1865                                     &vm->vm_map, OFF_TO_IDX(ravailable));
 1866                                 /* Update RSS usage after paging out. */
 1867                                 size = vmspace_resident_count(vm);
 1868                                 rsize = IDX_TO_OFF(size);
 1869                                 PROC_LOCK(p);
 1870                                 racct_set(p, RACCT_RSS, rsize);
 1871                                 PROC_UNLOCK(p);
 1872                                 if (rsize > ravailable)
 1873                                         tryagain = 1;
 1874                         }
 1875 #endif
 1876                         vmspace_free(vm);
 1877                 }
 1878                 sx_sunlock(&allproc_lock);
 1879                 if (tryagain != 0 && attempts <= 10)
 1880                         goto again;
 1881         }
 1882 }
 1883 #endif                  /* !defined(NO_SWAPPING) */

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