sys/vm/vm_pageout.c

   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("$FreeBSD$");
  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 int vm_pageout_clean(vm_page_t);
 119 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
 120 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
 121
 122 struct proc *pageproc;
 123
 124 static struct kproc_desc page_kp = {
 125         "pagedaemon",
 126         vm_pageout,
 127         &pageproc
 128 };
 129 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start,
 130     &page_kp);
 131
 132 #if !defined(NO_SWAPPING)
 133 /* the kernel process "vm_daemon"*/
 134 static void vm_daemon(void);
 135 static struct   proc *vmproc;
 136
 137 static struct kproc_desc vm_kp = {
 138         "vmdaemon",
 139         vm_daemon,
 140         &vmproc
 141 };
 142 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
 143 #endif
 144
 145
 146 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
 147 int vm_pageout_deficit;         /* Estimated number of pages deficit */
 148 int vm_pageout_pages_needed;    /* flag saying that the pageout daemon needs pages */
 149 int vm_pageout_wakeup_thresh;
 150
 151 #if !defined(NO_SWAPPING)
 152 static int vm_pageout_req_swapout;      /* XXX */
 153 static int vm_daemon_needed;
 154 static struct mtx vm_daemon_mtx;
 155 /* Allow for use by vm_pageout before vm_daemon is initialized. */
 156 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 157 #endif
 158 static int vm_max_launder = 32;
 159 static int vm_pageout_update_period;
 160 static int defer_swap_pageouts;
 161 static int disable_swap_pageouts;
 162 static int lowmem_period = 10;
 163 static int lowmem_ticks;
 164
 165 #if defined(NO_SWAPPING)
 166 static int vm_swap_enabled = 0;
 167 static int vm_swap_idle_enabled = 0;
 168 #else
 169 static int vm_swap_enabled = 1;
 170 static int vm_swap_idle_enabled = 0;
 171 #endif
 172
 173 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
 174         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
 175         "free page threshold for waking up the pageout daemon");
 176
 177 SYSCTL_INT(_vm, OID_AUTO, max_launder,
 178         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
 179
 180 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
 181         CTLFLAG_RW, &vm_pageout_update_period, 0,
 182         "Maximum active LRU update period");
 183
 184 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
 185         "Low memory callback period");
 186
 187 #if defined(NO_SWAPPING)
 188 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 189         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
 190 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 191         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 192 #else
 193 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 194         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
 195 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 196         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 197 #endif
 198
 199 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
 200         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
 201
 202 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
 203         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
 204
 205 static int pageout_lock_miss;
 206 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 207         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 208
 209 #define VM_PAGEOUT_PAGE_COUNT 16
 210 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
 211
 212 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
 213 SYSCTL_INT(_vm, OID_AUTO, max_wired,
 214         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
 215
 216 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
 217 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
 218     vm_paddr_t);
 219 #if !defined(NO_SWAPPING)
 220 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
 221 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
 222 static void vm_req_vmdaemon(int req);
 223 #endif
 224 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 225
 226 /*
 227  * Initialize a dummy page for marking the caller's place in the specified
 228  * paging queue.  In principle, this function only needs to set the flag
 229  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
 230  * to one as safety precautions.
 231  */
 232 static void
 233 vm_pageout_init_marker(vm_page_t marker, u_short queue)
 234 {
 235
 236         bzero(marker, sizeof(*marker));
 237         marker->flags = PG_MARKER;
 238         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
 239         marker->queue = queue;
 240         marker->hold_count = 1;
 241 }
 242
 243 /*
 244  * vm_pageout_fallback_object_lock:
 245  *
 246  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
 247  * known to have failed and page queue must be either PQ_ACTIVE or
 248  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
 249  * while locking the vm object.  Use marker page to detect page queue
 250  * changes and maintain notion of next page on page queue.  Return
 251  * TRUE if no changes were detected, FALSE otherwise.  vm object is
 252  * locked on return.
 253  *
 254  * This function depends on both the lock portion of struct vm_object
 255  * and normal struct vm_page being type stable.
 256  */
 257 static boolean_t
 258 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
 259 {
 260         struct vm_page marker;
 261         struct vm_pagequeue *pq;
 262         boolean_t unchanged;
 263         u_short queue;
 264         vm_object_t object;
 265
 266         queue = m->queue;
 267         vm_pageout_init_marker(&marker, queue);
 268         pq = vm_page_pagequeue(m);
 269         object = m->object;
 270
 271         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 272         vm_pagequeue_unlock(pq);
 273         vm_page_unlock(m);
 274         VM_OBJECT_WLOCK(object);
 275         vm_page_lock(m);
 276         vm_pagequeue_lock(pq);
 277
 278         /* Page queue might have changed. */
 279         *next = TAILQ_NEXT(&marker, plinks.q);
 280         unchanged = (m->queue == queue &&
 281                      m->object == object &&
 282                      &marker == TAILQ_NEXT(m, plinks.q));
 283         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 284         return (unchanged);
 285 }
 286
 287 /*
 288  * Lock the page while holding the page queue lock.  Use marker page
 289  * to detect page queue changes and maintain notion of next page on
 290  * page queue.  Return TRUE if no changes were detected, FALSE
 291  * otherwise.  The page is locked on return. The page queue lock might
 292  * be dropped and reacquired.
 293  *
 294  * This function depends on normal struct vm_page being type stable.
 295  */
 296 static boolean_t
 297 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
 298 {
 299         struct vm_page marker;
 300         struct vm_pagequeue *pq;
 301         boolean_t unchanged;
 302         u_short queue;
 303
 304         vm_page_lock_assert(m, MA_NOTOWNED);
 305         if (vm_page_trylock(m))
 306                 return (TRUE);
 307
 308         queue = m->queue;
 309         vm_pageout_init_marker(&marker, queue);
 310         pq = vm_page_pagequeue(m);
 311
 312         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 313         vm_pagequeue_unlock(pq);
 314         vm_page_lock(m);
 315         vm_pagequeue_lock(pq);
 316
 317         /* Page queue might have changed. */
 318         *next = TAILQ_NEXT(&marker, plinks.q);
 319         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
 320         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 321         return (unchanged);
 322 }
 323
 324 /*
 325  * vm_pageout_clean:
 326  *
 327  * Clean the page and remove it from the laundry.
 328  *
 329  * We set the busy bit to cause potential page faults on this page to
 330  * block.  Note the careful timing, however, the busy bit isn't set till
 331  * late and we cannot do anything that will mess with the page.
 332  */
 333 static int
 334 vm_pageout_clean(vm_page_t m)
 335 {
 336         vm_object_t object;
 337         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
 338         int pageout_count;
 339         int ib, is, page_base;
 340         vm_pindex_t pindex = m->pindex;
 341
 342         vm_page_lock_assert(m, MA_OWNED);
 343         object = m->object;
 344         VM_OBJECT_ASSERT_WLOCKED(object);
 345
 346         /*
 347          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
 348          * with the new swapper, but we could have serious problems paging
 349          * out other object types if there is insufficient memory.
 350          *
 351          * Unfortunately, checking free memory here is far too late, so the
 352          * check has been moved up a procedural level.
 353          */
 354
 355         /*
 356          * Can't clean the page if it's busy or held.
 357          */
 358         vm_page_assert_unbusied(m);
 359         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
 360         vm_page_unlock(m);
 361
 362         mc[vm_pageout_page_count] = pb = ps = m;
 363         pageout_count = 1;
 364         page_base = vm_pageout_page_count;
 365         ib = 1;
 366         is = 1;
 367
 368         /*
 369          * Scan object for clusterable pages.
 370          *
 371          * We can cluster ONLY if: ->> the page is NOT
 372          * clean, wired, busy, held, or mapped into a
 373          * buffer, and one of the following:
 374          * 1) The page is inactive, or a seldom used
 375          *    active page.
 376          * -or-
 377          * 2) we force the issue.
 378          *
 379          * During heavy mmap/modification loads the pageout
 380          * daemon can really fragment the underlying file
 381          * due to flushing pages out of order and not trying
 382          * align the clusters (which leave sporatic out-of-order
 383          * holes).  To solve this problem we do the reverse scan
 384          * first and attempt to align our cluster, then do a
 385          * forward scan if room remains.
 386          */
 387 more:
 388         while (ib && pageout_count < vm_pageout_page_count) {
 389                 vm_page_t p;
 390
 391                 if (ib > pindex) {
 392                         ib = 0;
 393                         break;
 394                 }
 395
 396                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
 397                         ib = 0;
 398                         break;
 399                 }
 400                 vm_page_lock(p);
 401                 vm_page_test_dirty(p);
 402                 if (p->dirty == 0 ||
 403                     p->queue != PQ_INACTIVE ||
 404                     p->hold_count != 0) {       /* may be undergoing I/O */
 405                         vm_page_unlock(p);
 406                         ib = 0;
 407                         break;
 408                 }
 409                 vm_page_unlock(p);
 410                 mc[--page_base] = pb = p;
 411                 ++pageout_count;
 412                 ++ib;
 413                 /*
 414                  * alignment boundry, stop here and switch directions.  Do
 415                  * not clear ib.
 416                  */
 417                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 418                         break;
 419         }
 420
 421         while (pageout_count < vm_pageout_page_count &&
 422             pindex + is < object->size) {
 423                 vm_page_t p;
 424
 425                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
 426                         break;
 427                 vm_page_lock(p);
 428                 vm_page_test_dirty(p);
 429                 if (p->dirty == 0 ||
 430                     p->queue != PQ_INACTIVE ||
 431                     p->hold_count != 0) {       /* may be undergoing I/O */
 432                         vm_page_unlock(p);
 433                         break;
 434                 }
 435                 vm_page_unlock(p);
 436                 mc[page_base + pageout_count] = ps = p;
 437                 ++pageout_count;
 438                 ++is;
 439         }
 440
 441         /*
 442          * If we exhausted our forward scan, continue with the reverse scan
 443          * when possible, even past a page boundry.  This catches boundry
 444          * conditions.
 445          */
 446         if (ib && pageout_count < vm_pageout_page_count)
 447                 goto more;
 448
 449         /*
 450          * we allow reads during pageouts...
 451          */
 452         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
 453             NULL));
 454 }
 455
 456 /*
 457  * vm_pageout_flush() - launder the given pages
 458  *
 459  *      The given pages are laundered.  Note that we setup for the start of
 460  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
 461  *      reference count all in here rather then in the parent.  If we want
 462  *      the parent to do more sophisticated things we may have to change
 463  *      the ordering.
 464  *
 465  *      Returned runlen is the count of pages between mreq and first
 466  *      page after mreq with status VM_PAGER_AGAIN.
 467  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
 468  *      for any page in runlen set.
 469  */
 470 int
 471 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
 472     boolean_t *eio)
 473 {
 474         vm_object_t object = mc[0]->object;
 475         int pageout_status[count];
 476         int numpagedout = 0;
 477         int i, runlen;
 478
 479         VM_OBJECT_ASSERT_WLOCKED(object);
 480
 481         /*
 482          * Initiate I/O.  Bump the vm_page_t->busy counter and
 483          * mark the pages read-only.
 484          *
 485          * We do not have to fixup the clean/dirty bits here... we can
 486          * allow the pager to do it after the I/O completes.
 487          *
 488          * NOTE! mc[i]->dirty may be partial or fragmented due to an
 489          * edge case with file fragments.
 490          */
 491         for (i = 0; i < count; i++) {
 492                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
 493                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
 494                         mc[i], i, count));
 495                 vm_page_sbusy(mc[i]);
 496                 pmap_remove_write(mc[i]);
 497         }
 498         vm_object_pip_add(object, count);
 499
 500         vm_pager_put_pages(object, mc, count, flags, pageout_status);
 501
 502         runlen = count - mreq;
 503         if (eio != NULL)
 504                 *eio = FALSE;
 505         for (i = 0; i < count; i++) {
 506                 vm_page_t mt = mc[i];
 507
 508                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
 509                     !pmap_page_is_write_mapped(mt),
 510                     ("vm_pageout_flush: page %p is not write protected", mt));
 511                 switch (pageout_status[i]) {
 512                 case VM_PAGER_OK:
 513                 case VM_PAGER_PEND:
 514                         numpagedout++;
 515                         break;
 516                 case VM_PAGER_BAD:
 517                         /*
 518                          * Page outside of range of object. Right now we
 519                          * essentially lose the changes by pretending it
 520                          * worked.
 521                          */
 522                         vm_page_undirty(mt);
 523                         break;
 524                 case VM_PAGER_ERROR:
 525                 case VM_PAGER_FAIL:
 526                         /*
 527                          * If page couldn't be paged out, then reactivate the
 528                          * page so it doesn't clog the inactive list.  (We
 529                          * will try paging out it again later).
 530                          */
 531                         vm_page_lock(mt);
 532                         vm_page_activate(mt);
 533                         vm_page_unlock(mt);
 534                         if (eio != NULL && i >= mreq && i - mreq < runlen)
 535                                 *eio = TRUE;
 536                         break;
 537                 case VM_PAGER_AGAIN:
 538                         if (i >= mreq && i - mreq < runlen)
 539                                 runlen = i - mreq;
 540                         break;
 541                 }
 542
 543                 /*
 544                  * If the operation is still going, leave the page busy to
 545                  * block all other accesses. Also, leave the paging in
 546                  * progress indicator set so that we don't attempt an object
 547                  * collapse.
 548                  */
 549                 if (pageout_status[i] != VM_PAGER_PEND) {
 550                         vm_object_pip_wakeup(object);
 551                         vm_page_sunbusy(mt);
 552                         if (vm_page_count_severe()) {
 553                                 vm_page_lock(mt);
 554                                 vm_page_try_to_cache(mt);
 555                                 vm_page_unlock(mt);
 556                         }
 557                 }
 558         }
 559         if (prunlen != NULL)
 560                 *prunlen = runlen;
 561         return (numpagedout);
 562 }
 563
 564 static boolean_t
 565 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
 566     vm_paddr_t high)
 567 {
 568         struct mount *mp;
 569         struct vnode *vp;
 570         vm_object_t object;
 571         vm_paddr_t pa;
 572         vm_page_t m, m_tmp, next;
 573         int lockmode;
 574
 575         vm_pagequeue_lock(pq);
 576         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
 577                 if ((m->flags & PG_MARKER) != 0)
 578                         continue;
 579                 pa = VM_PAGE_TO_PHYS(m);
 580                 if (pa < low || pa + PAGE_SIZE > high)
 581                         continue;
 582                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
 583                         vm_page_unlock(m);
 584                         continue;
 585                 }
 586                 object = m->object;
 587                 if ((!VM_OBJECT_TRYWLOCK(object) &&
 588                     (!vm_pageout_fallback_object_lock(m, &next) ||
 589                     m->hold_count != 0)) || vm_page_busied(m)) {
 590                         vm_page_unlock(m);
 591                         VM_OBJECT_WUNLOCK(object);
 592                         continue;
 593                 }
 594                 vm_page_test_dirty(m);
 595                 if (m->dirty == 0 && object->ref_count != 0)
 596                         pmap_remove_all(m);
 597                 if (m->dirty != 0) {
 598                         vm_page_unlock(m);
 599                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
 600                                 VM_OBJECT_WUNLOCK(object);
 601                                 continue;
 602                         }
 603                         if (object->type == OBJT_VNODE) {
 604                                 vm_pagequeue_unlock(pq);
 605                                 vp = object->handle;
 606                                 vm_object_reference_locked(object);
 607                                 VM_OBJECT_WUNLOCK(object);
 608                                 (void)vn_start_write(vp, &mp, V_WAIT);
 609                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 610                                     LK_SHARED : LK_EXCLUSIVE;
 611                                 vn_lock(vp, lockmode | LK_RETRY);
 612                                 VM_OBJECT_WLOCK(object);
 613                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
 614                                 VM_OBJECT_WUNLOCK(object);
 615                                 VOP_UNLOCK(vp, 0);
 616                                 vm_object_deallocate(object);
 617                                 vn_finished_write(mp);
 618                                 return (TRUE);
 619                         } else if (object->type == OBJT_SWAP ||
 620                             object->type == OBJT_DEFAULT) {
 621                                 vm_pagequeue_unlock(pq);
 622                                 m_tmp = m;
 623                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
 624                                     0, NULL, NULL);
 625                                 VM_OBJECT_WUNLOCK(object);
 626                                 return (TRUE);
 627                         }
 628                 } else {
 629                         /*
 630                          * Dequeue here to prevent lock recursion in
 631                          * vm_page_cache().
 632                          */
 633                         vm_page_dequeue_locked(m);
 634                         vm_page_cache(m);
 635                         vm_page_unlock(m);
 636                 }
 637                 VM_OBJECT_WUNLOCK(object);
 638         }
 639         vm_pagequeue_unlock(pq);
 640         return (FALSE);
 641 }
 642
 643 /*
 644  * Increase the number of cached pages.  The specified value, "tries",
 645  * determines which categories of pages are cached:
 646  *
 647  *  0: All clean, inactive pages within the specified physical address range
 648  *     are cached.  Will not sleep.
 649  *  1: The vm_lowmem handlers are called.  All inactive pages within
 650  *     the specified physical address range are cached.  May sleep.
 651  *  2: The vm_lowmem handlers are called.  All inactive and active pages
 652  *     within the specified physical address range are cached.  May sleep.
 653  */
 654 void
 655 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
 656 {
 657         int actl, actmax, inactl, inactmax, dom, initial_dom;
 658         static int start_dom = 0;
 659
 660         if (tries > 0) {
 661                 /*
 662                  * Decrease registered cache sizes.  The vm_lowmem handlers
 663                  * may acquire locks and/or sleep, so they can only be invoked
 664                  * when "tries" is greater than zero.
 665                  */
 666                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 667
 668                 /*
 669                  * We do this explicitly after the caches have been drained
 670                  * above.
 671                  */
 672                 uma_reclaim();
 673         }
 674
 675         /*
 676          * Make the next scan start on the next domain.
 677          */
 678         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
 679
 680         inactl = 0;
 681         inactmax = cnt.v_inactive_count;
 682         actl = 0;
 683         actmax = tries < 2 ? 0 : cnt.v_active_count;
 684         dom = initial_dom;
 685
 686         /*
 687          * Scan domains in round-robin order, first inactive queues,
 688          * then active.  Since domain usually owns large physically
 689          * contiguous chunk of memory, it makes sense to completely
 690          * exhaust one domain before switching to next, while growing
 691          * the pool of contiguous physical pages.
 692          *
 693          * Do not even start launder a domain which cannot contain
 694          * the specified address range, as indicated by segments
 695          * constituting the domain.
 696          */
 697 again:
 698         if (inactl < inactmax) {
 699                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 700                     low, high) &&
 701                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
 702                     tries, low, high)) {
 703                         inactl++;
 704                         goto again;
 705                 }
 706                 if (++dom == vm_ndomains)
 707                         dom = 0;
 708                 if (dom != initial_dom)
 709                         goto again;
 710         }
 711         if (actl < actmax) {
 712                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 713                     low, high) &&
 714                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
 715                       tries, low, high)) {
 716                         actl++;
 717                         goto again;
 718                 }
 719                 if (++dom == vm_ndomains)
 720                         dom = 0;
 721                 if (dom != initial_dom)
 722                         goto again;
 723         }
 724 }
 725
 726 #if !defined(NO_SWAPPING)
 727 /*
 728  *      vm_pageout_object_deactivate_pages
 729  *
 730  *      Deactivate enough pages to satisfy the inactive target
 731  *      requirements.
 732  *
 733  *      The object and map must be locked.
 734  */
 735 static void
 736 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 737     long desired)
 738 {
 739         vm_object_t backing_object, object;
 740         vm_page_t p;
 741         int act_delta, remove_mode;
 742
 743         VM_OBJECT_ASSERT_LOCKED(first_object);
 744         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 745                 return;
 746         for (object = first_object;; object = backing_object) {
 747                 if (pmap_resident_count(pmap) <= desired)
 748                         goto unlock_return;
 749                 VM_OBJECT_ASSERT_LOCKED(object);
 750                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 751                     object->paging_in_progress != 0)
 752                         goto unlock_return;
 753
 754                 remove_mode = 0;
 755                 if (object->shadow_count > 1)
 756                         remove_mode = 1;
 757                 /*
 758                  * Scan the object's entire memory queue.
 759                  */
 760                 TAILQ_FOREACH(p, &object->memq, listq) {
 761                         if (pmap_resident_count(pmap) <= desired)
 762                                 goto unlock_return;
 763                         if (vm_page_busied(p))
 764                                 continue;
 765                         PCPU_INC(cnt.v_pdpages);
 766                         vm_page_lock(p);
 767                         if (p->wire_count != 0 || p->hold_count != 0 ||
 768                             !pmap_page_exists_quick(pmap, p)) {
 769                                 vm_page_unlock(p);
 770                                 continue;
 771                         }
 772                         act_delta = pmap_ts_referenced(p);
 773                         if ((p->aflags & PGA_REFERENCED) != 0) {
 774                                 if (act_delta == 0)
 775                                         act_delta = 1;
 776                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 777                         }
 778                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
 779                                 vm_page_activate(p);
 780                                 p->act_count += act_delta;
 781                         } else if (p->queue == PQ_ACTIVE) {
 782                                 if (act_delta == 0) {
 783                                         p->act_count -= min(p->act_count,
 784                                             ACT_DECLINE);
 785                                         if (!remove_mode && p->act_count == 0) {
 786                                                 pmap_remove_all(p);
 787                                                 vm_page_deactivate(p);
 788                                         } else
 789                                                 vm_page_requeue(p);
 790                                 } else {
 791                                         vm_page_activate(p);
 792                                         if (p->act_count < ACT_MAX -
 793                                             ACT_ADVANCE)
 794                                                 p->act_count += ACT_ADVANCE;
 795                                         vm_page_requeue(p);
 796                                 }
 797                         } else if (p->queue == PQ_INACTIVE)
 798                                 pmap_remove_all(p);
 799                         vm_page_unlock(p);
 800                 }
 801                 if ((backing_object = object->backing_object) == NULL)
 802                         goto unlock_return;
 803                 VM_OBJECT_RLOCK(backing_object);
 804                 if (object != first_object)
 805                         VM_OBJECT_RUNLOCK(object);
 806         }
 807 unlock_return:
 808         if (object != first_object)
 809                 VM_OBJECT_RUNLOCK(object);
 810 }
 811
 812 /*
 813  * deactivate some number of pages in a map, try to do it fairly, but
 814  * that is really hard to do.
 815  */
 816 static void
 817 vm_pageout_map_deactivate_pages(map, desired)
 818         vm_map_t map;
 819         long desired;
 820 {
 821         vm_map_entry_t tmpe;
 822         vm_object_t obj, bigobj;
 823         int nothingwired;
 824
 825         if (!vm_map_trylock(map))
 826                 return;
 827
 828         bigobj = NULL;
 829         nothingwired = TRUE;
 830
 831         /*
 832          * first, search out the biggest object, and try to free pages from
 833          * that.
 834          */
 835         tmpe = map->header.next;
 836         while (tmpe != &map->header) {
 837                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 838                         obj = tmpe->object.vm_object;
 839                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 840                                 if (obj->shadow_count <= 1 &&
 841                                     (bigobj == NULL ||
 842                                      bigobj->resident_page_count < obj->resident_page_count)) {
 843                                         if (bigobj != NULL)
 844                                                 VM_OBJECT_RUNLOCK(bigobj);
 845                                         bigobj = obj;
 846                                 } else
 847                                         VM_OBJECT_RUNLOCK(obj);
 848                         }
 849                 }
 850                 if (tmpe->wired_count > 0)
 851                         nothingwired = FALSE;
 852                 tmpe = tmpe->next;
 853         }
 854
 855         if (bigobj != NULL) {
 856                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
 857                 VM_OBJECT_RUNLOCK(bigobj);
 858         }
 859         /*
 860          * Next, hunt around for other pages to deactivate.  We actually
 861          * do this search sort of wrong -- .text first is not the best idea.
 862          */
 863         tmpe = map->header.next;
 864         while (tmpe != &map->header) {
 865                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 866                         break;
 867                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 868                         obj = tmpe->object.vm_object;
 869                         if (obj != NULL) {
 870                                 VM_OBJECT_RLOCK(obj);
 871                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
 872                                 VM_OBJECT_RUNLOCK(obj);
 873                         }
 874                 }
 875                 tmpe = tmpe->next;
 876         }
 877
 878 #ifdef __ia64__
 879         /*
 880          * Remove all non-wired, managed mappings if a process is swapped out.
 881          * This will free page table pages.
 882          */
 883         if (desired == 0)
 884                 pmap_remove_pages(map->pmap);
 885 #else
 886         /*
 887          * Remove all mappings if a process is swapped out, this will free page
 888          * table pages.
 889          */
 890         if (desired == 0 && nothingwired) {
 891                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 892                     vm_map_max(map));
 893         }
 894 #endif
 895
 896         vm_map_unlock(map);
 897 }
 898 #endif          /* !defined(NO_SWAPPING) */
 899
 900 /*
 901  *      vm_pageout_scan does the dirty work for the pageout daemon.
 902  *
 903  *      pass 0 - Update active LRU/deactivate pages
 904  *      pass 1 - Move inactive to cache or free
 905  *      pass 2 - Launder dirty pages
 906  */
 907 static void
 908 vm_pageout_scan(struct vm_domain *vmd, int pass)
 909 {
 910         vm_page_t m, next;
 911         struct vm_pagequeue *pq;
 912         vm_object_t object;
 913         int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
 914         int vnodes_skipped = 0;
 915         int maxlaunder;
 916         int lockmode;
 917         boolean_t queues_locked;
 918
 919         /*
 920          * If we need to reclaim memory ask kernel caches to return
 921          * some.  We rate limit to avoid thrashing.
 922          */
 923         if (vmd == &vm_dom[0] && pass > 0 &&
 924             (ticks - lowmem_ticks) / hz >= lowmem_period) {
 925                 /*
 926                  * Decrease registered cache sizes.
 927                  */
 928                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 929                 /*
 930                  * We do this explicitly after the caches have been
 931                  * drained above.
 932                  */
 933                 uma_reclaim();
 934                 lowmem_ticks = ticks;
 935         }
 936
 937         /*
 938          * The addl_page_shortage is the number of temporarily
 939          * stuck pages in the inactive queue.  In other words, the
 940          * number of pages from the inactive count that should be
 941          * discounted in setting the target for the active queue scan.
 942          */
 943         addl_page_shortage = 0;
 944
 945         /*
 946          * Calculate the number of pages we want to either free or move
 947          * to the cache.
 948          */
 949         if (pass > 0) {
 950                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
 951                 page_shortage = vm_paging_target() + deficit;
 952         } else
 953                 page_shortage = deficit = 0;
 954
 955         /*
 956          * maxlaunder limits the number of dirty pages we flush per scan.
 957          * For most systems a smaller value (16 or 32) is more robust under
 958          * extreme memory and disk pressure because any unnecessary writes
 959          * to disk can result in extreme performance degredation.  However,
 960          * systems with excessive dirty pages (especially when MAP_NOSYNC is
 961          * used) will die horribly with limited laundering.  If the pageout
 962          * daemon cannot clean enough pages in the first pass, we let it go
 963          * all out in succeeding passes.
 964          */
 965         if ((maxlaunder = vm_max_launder) <= 1)
 966                 maxlaunder = 1;
 967         if (pass > 1)
 968                 maxlaunder = 10000;
 969
 970         /*
 971          * Start scanning the inactive queue for pages we can move to the
 972          * cache or free.  The scan will stop when the target is reached or
 973          * we have scanned the entire inactive queue.  Note that m->act_count
 974          * is not used to form decisions for the inactive queue, only for the
 975          * active queue.
 976          */
 977         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
 978         maxscan = pq->pq_cnt;
 979         vm_pagequeue_lock(pq);
 980         queues_locked = TRUE;
 981         for (m = TAILQ_FIRST(&pq->pq_pl);
 982              m != NULL && maxscan-- > 0 && page_shortage > 0;
 983              m = next) {
 984                 vm_pagequeue_assert_locked(pq);
 985                 KASSERT(queues_locked, ("unlocked queues"));
 986                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
 987
 988                 PCPU_INC(cnt.v_pdpages);
 989                 next = TAILQ_NEXT(m, plinks.q);
 990
 991                 /*
 992                  * skip marker pages
 993                  */
 994                 if (m->flags & PG_MARKER)
 995                         continue;
 996
 997                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 998                     ("Fictitious page %p cannot be in inactive queue", m));
 999                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1000                     ("Unmanaged page %p cannot be in inactive queue", m));
1001
1002                 /*
1003                  * The page or object lock acquisitions fail if the
1004                  * page was removed from the queue or moved to a
1005                  * different position within the queue.  In either
1006                  * case, addl_page_shortage should not be incremented.
1007                  */
1008                 if (!vm_pageout_page_lock(m, &next)) {
1009                         vm_page_unlock(m);
1010                         continue;
1011                 }
1012                 object = m->object;
1013                 if (!VM_OBJECT_TRYWLOCK(object) &&
1014                     !vm_pageout_fallback_object_lock(m, &next)) {
1015                         vm_page_unlock(m);
1016                         VM_OBJECT_WUNLOCK(object);
1017                         continue;
1018                 }
1019
1020                 /*
1021                  * Don't mess with busy pages, keep them at at the
1022                  * front of the queue, most likely they are being
1023                  * paged out.  Increment addl_page_shortage for busy
1024                  * pages, because they may leave the inactive queue
1025                  * shortly after page scan is finished.
1026                  */
1027                 if (vm_page_busied(m)) {
1028                         vm_page_unlock(m);
1029                         VM_OBJECT_WUNLOCK(object);
1030                         addl_page_shortage++;
1031                         continue;
1032                 }
1033
1034                 /*
1035                  * We unlock the inactive page queue, invalidating the
1036                  * 'next' pointer.  Use our marker to remember our
1037                  * place.
1038                  */
1039                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
1040                 vm_pagequeue_unlock(pq);
1041                 queues_locked = FALSE;
1042
1043                 /*
1044                  * We bump the activation count if the page has been
1045                  * referenced while in the inactive queue.  This makes
1046                  * it less likely that the page will be added back to the
1047                  * inactive queue prematurely again.  Here we check the
1048                  * page tables (or emulated bits, if any), given the upper
1049                  * level VM system not knowing anything about existing
1050                  * references.
1051                  */
1052                 act_delta = 0;
1053                 if ((m->aflags & PGA_REFERENCED) != 0) {
1054                         vm_page_aflag_clear(m, PGA_REFERENCED);
1055                         act_delta = 1;
1056                 }
1057                 if (object->ref_count != 0) {
1058                         act_delta += pmap_ts_referenced(m);
1059                 } else {
1060                         KASSERT(!pmap_page_is_mapped(m),
1061                             ("vm_pageout_scan: page %p is mapped", m));
1062                 }
1063
1064                 /*
1065                  * If the upper level VM system knows about any page
1066                  * references, we reactivate the page or requeue it.
1067                  */
1068                 if (act_delta != 0) {
1069                         if (object->ref_count) {
1070                                 vm_page_activate(m);
1071                                 m->act_count += act_delta + ACT_ADVANCE;
1072                         } else {
1073                                 vm_pagequeue_lock(pq);
1074                                 queues_locked = TRUE;
1075                                 vm_page_requeue_locked(m);
1076                         }
1077                         VM_OBJECT_WUNLOCK(object);
1078                         vm_page_unlock(m);
1079                         goto relock_queues;
1080                 }
1081
1082                 if (m->hold_count != 0) {
1083                         vm_page_unlock(m);
1084                         VM_OBJECT_WUNLOCK(object);
1085
1086                         /*
1087                          * Held pages are essentially stuck in the
1088                          * queue.  So, they ought to be discounted
1089                          * from the inactive count.  See the
1090                          * calculation of the page_shortage for the
1091                          * loop over the active queue below.
1092                          */
1093                         addl_page_shortage++;
1094                         goto relock_queues;
1095                 }
1096
1097                 /*
1098                  * If the page appears to be clean at the machine-independent
1099                  * layer, then remove all of its mappings from the pmap in
1100                  * anticipation of placing it onto the cache queue.  If,
1101                  * however, any of the page's mappings allow write access,
1102                  * then the page may still be modified until the last of those
1103                  * mappings are removed.
1104                  */
1105                 vm_page_test_dirty(m);
1106                 if (m->dirty == 0 && object->ref_count != 0)
1107                         pmap_remove_all(m);
1108
1109                 if (m->valid == 0) {
1110                         /*
1111                          * Invalid pages can be easily freed
1112                          */
1113                         vm_page_free(m);
1114                         PCPU_INC(cnt.v_dfree);
1115                         --page_shortage;
1116                 } else if (m->dirty == 0) {
1117                         /*
1118                          * Clean pages can be placed onto the cache queue.
1119                          * This effectively frees them.
1120                          */
1121                         vm_page_cache(m);
1122                         --page_shortage;
1123                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
1124                         /*
1125                          * Dirty pages need to be paged out, but flushing
1126                          * a page is extremely expensive verses freeing
1127                          * a clean page.  Rather then artificially limiting
1128                          * the number of pages we can flush, we instead give
1129                          * dirty pages extra priority on the inactive queue
1130                          * by forcing them to be cycled through the queue
1131                          * twice before being flushed, after which the
1132                          * (now clean) page will cycle through once more
1133                          * before being freed.  This significantly extends
1134                          * the thrash point for a heavily loaded machine.
1135                          */
1136                         m->flags |= PG_WINATCFLS;
1137                         vm_pagequeue_lock(pq);
1138                         queues_locked = TRUE;
1139                         vm_page_requeue_locked(m);
1140                 } else if (maxlaunder > 0) {
1141                         /*
1142                          * We always want to try to flush some dirty pages if
1143                          * we encounter them, to keep the system stable.
1144                          * Normally this number is small, but under extreme
1145                          * pressure where there are insufficient clean pages
1146                          * on the inactive queue, we may have to go all out.
1147                          */
1148                         int swap_pageouts_ok;
1149                         struct vnode *vp = NULL;
1150                         struct mount *mp = NULL;
1151
1152                         if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
1153                                 swap_pageouts_ok = 1;
1154                         } else {
1155                                 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
1156                                 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
1157                                 vm_page_count_min());
1158
1159                         }
1160
1161                         /*
1162                          * We don't bother paging objects that are "dead".
1163                          * Those objects are in a "rundown" state.
1164                          */
1165                         if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
1166                                 vm_pagequeue_lock(pq);
1167                                 vm_page_unlock(m);
1168                                 VM_OBJECT_WUNLOCK(object);
1169                                 queues_locked = TRUE;
1170                                 vm_page_requeue_locked(m);
1171                                 goto relock_queues;
1172                         }
1173
1174                         /*
1175                          * The object is already known NOT to be dead.   It
1176                          * is possible for the vget() to block the whole
1177                          * pageout daemon, but the new low-memory handling
1178                          * code should prevent it.
1179                          *
1180                          * The previous code skipped locked vnodes and, worse,
1181                          * reordered pages in the queue.  This results in
1182                          * completely non-deterministic operation and, on a
1183                          * busy system, can lead to extremely non-optimal
1184                          * pageouts.  For example, it can cause clean pages
1185                          * to be freed and dirty pages to be moved to the end
1186                          * of the queue.  Since dirty pages are also moved to
1187                          * the end of the queue once-cleaned, this gives
1188                          * way too large a weighting to defering the freeing
1189                          * of dirty pages.
1190                          *
1191                          * We can't wait forever for the vnode lock, we might
1192                          * deadlock due to a vn_read() getting stuck in
1193                          * vm_wait while holding this vnode.  We skip the
1194                          * vnode if we can't get it in a reasonable amount
1195                          * of time.
1196                          */
1197                         if (object->type == OBJT_VNODE) {
1198                                 vm_page_unlock(m);
1199                                 vp = object->handle;
1200                                 if (vp->v_type == VREG &&
1201                                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
1202                                         mp = NULL;
1203                                         ++pageout_lock_miss;
1204                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1205                                                 vnodes_skipped++;
1206                                         goto unlock_and_continue;
1207                                 }
1208                                 KASSERT(mp != NULL,
1209                                     ("vp %p with NULL v_mount", vp));
1210                                 vm_object_reference_locked(object);
1211                                 VM_OBJECT_WUNLOCK(object);
1212                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
1213                                     LK_SHARED : LK_EXCLUSIVE;
1214                                 if (vget(vp, lockmode | LK_TIMELOCK,
1215                                     curthread)) {
1216                                         VM_OBJECT_WLOCK(object);
1217                                         ++pageout_lock_miss;
1218                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1219                                                 vnodes_skipped++;
1220                                         vp = NULL;
1221                                         goto unlock_and_continue;
1222                                 }
1223                                 VM_OBJECT_WLOCK(object);
1224                                 vm_page_lock(m);
1225                                 vm_pagequeue_lock(pq);
1226                                 queues_locked = TRUE;
1227                                 /*
1228                                  * The page might have been moved to another
1229                                  * queue during potential blocking in vget()
1230                                  * above.  The page might have been freed and
1231                                  * reused for another vnode.
1232                                  */
1233                                 if (m->queue != PQ_INACTIVE ||
1234                                     m->object != object ||
1235                                     TAILQ_NEXT(m, plinks.q) != &vmd->vmd_marker) {
1236                                         vm_page_unlock(m);
1237                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1238                                                 vnodes_skipped++;
1239                                         goto unlock_and_continue;
1240                                 }
1241
1242                                 /*
1243                                  * The page may have been busied during the
1244                                  * blocking in vget().  We don't move the
1245                                  * page back onto the end of the queue so that
1246                                  * statistics are more correct if we don't.
1247                                  */
1248                                 if (vm_page_busied(m)) {
1249                                         vm_page_unlock(m);
1250                                         addl_page_shortage++;
1251                                         goto unlock_and_continue;
1252                                 }
1253
1254                                 /*
1255                                  * If the page has become held it might
1256                                  * be undergoing I/O, so skip it
1257                                  */
1258                                 if (m->hold_count != 0) {
1259                                         vm_page_unlock(m);
1260                                         addl_page_shortage++;
1261                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1262                                                 vnodes_skipped++;
1263                                         goto unlock_and_continue;
1264                                 }
1265                                 vm_pagequeue_unlock(pq);
1266                                 queues_locked = FALSE;
1267                         }
1268
1269                         /*
1270                          * If a page is dirty, then it is either being washed
1271                          * (but not yet cleaned) or it is still in the
1272                          * laundry.  If it is still in the laundry, then we
1273                          * start the cleaning operation.
1274                          *
1275                          * decrement page_shortage on success to account for
1276                          * the (future) cleaned page.  Otherwise we could wind
1277                          * up laundering or cleaning too many pages.
1278                          */
1279                         if (vm_pageout_clean(m) != 0) {
1280                                 --page_shortage;
1281                                 --maxlaunder;
1282                         }
1283 unlock_and_continue:
1284                         vm_page_lock_assert(m, MA_NOTOWNED);
1285                         VM_OBJECT_WUNLOCK(object);
1286                         if (mp != NULL) {
1287                                 if (queues_locked) {
1288                                         vm_pagequeue_unlock(pq);
1289                                         queues_locked = FALSE;
1290                                 }
1291                                 if (vp != NULL)
1292                                         vput(vp);
1293                                 vm_object_deallocate(object);
1294                                 vn_finished_write(mp);
1295                         }
1296                         vm_page_lock_assert(m, MA_NOTOWNED);
1297                         goto relock_queues;
1298                 }
1299                 vm_page_unlock(m);
1300                 VM_OBJECT_WUNLOCK(object);
1301 relock_queues:
1302                 if (!queues_locked) {
1303                         vm_pagequeue_lock(pq);
1304                         queues_locked = TRUE;
1305                 }
1306                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
1307                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
1308         }
1309         vm_pagequeue_unlock(pq);
1310
1311 #if !defined(NO_SWAPPING)
1312         /*
1313          * Wakeup the swapout daemon if we didn't cache or free the targeted
1314          * number of pages.
1315          */
1316         if (vm_swap_enabled && page_shortage > 0)
1317                 vm_req_vmdaemon(VM_SWAP_NORMAL);
1318 #endif
1319
1320         /*
1321          * Wakeup the sync daemon if we skipped a vnode in a writeable object
1322          * and we didn't cache or free enough pages.
1323          */
1324         if (vnodes_skipped > 0 && page_shortage > cnt.v_free_target -
1325             cnt.v_free_min)
1326                 (void)speedup_syncer();
1327
1328         /*
1329          * Compute the number of pages we want to try to move from the
1330          * active queue to the inactive queue.
1331          */
1332         page_shortage = cnt.v_inactive_target - cnt.v_inactive_count +
1333             vm_paging_target() + deficit + addl_page_shortage;
1334
1335         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1336         vm_pagequeue_lock(pq);
1337         maxscan = pq->pq_cnt;
1338
1339         /*
1340          * If we're just idle polling attempt to visit every
1341          * active page within 'update_period' seconds.
1342          */
1343         if (pass == 0 && vm_pageout_update_period != 0) {
1344                 maxscan /= vm_pageout_update_period;
1345                 page_shortage = maxscan;
1346         }
1347
1348         /*
1349          * Scan the active queue for things we can deactivate. We nominally
1350          * track the per-page activity counter and use it to locate
1351          * deactivation candidates.
1352          */
1353         m = TAILQ_FIRST(&pq->pq_pl);
1354         while (m != NULL && maxscan-- > 0 && page_shortage > 0) {
1355
1356                 KASSERT(m->queue == PQ_ACTIVE,
1357                     ("vm_pageout_scan: page %p isn't active", m));
1358
1359                 next = TAILQ_NEXT(m, plinks.q);
1360                 if ((m->flags & PG_MARKER) != 0) {
1361                         m = next;
1362                         continue;
1363                 }
1364                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1365                     ("Fictitious page %p cannot be in active queue", m));
1366                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1367                     ("Unmanaged page %p cannot be in active queue", m));
1368                 if (!vm_pageout_page_lock(m, &next)) {
1369                         vm_page_unlock(m);
1370                         m = next;
1371                         continue;
1372                 }
1373
1374                 /*
1375                  * The count for pagedaemon pages is done after checking the
1376                  * page for eligibility...
1377                  */
1378                 PCPU_INC(cnt.v_pdpages);
1379
1380                 /*
1381                  * Check to see "how much" the page has been used.
1382                  */
1383                 act_delta = 0;
1384                 if (m->aflags & PGA_REFERENCED) {
1385                         vm_page_aflag_clear(m, PGA_REFERENCED);
1386                         act_delta += 1;
1387                 }
1388                 /*
1389                  * Unlocked object ref count check.  Two races are possible.
1390                  * 1) The ref was transitioning to zero and we saw non-zero,
1391                  *    the pmap bits will be checked unnecessarily.
1392                  * 2) The ref was transitioning to one and we saw zero.
1393                  *    The page lock prevents a new reference to this page so
1394                  *    we need not check the reference bits.
1395                  */
1396                 if (m->object->ref_count != 0)
1397                         act_delta += pmap_ts_referenced(m);
1398
1399                 /*
1400                  * Advance or decay the act_count based on recent usage.
1401                  */
1402                 if (act_delta) {
1403                         m->act_count += ACT_ADVANCE + act_delta;
1404                         if (m->act_count > ACT_MAX)
1405                                 m->act_count = ACT_MAX;
1406                 } else {
1407                         m->act_count -= min(m->act_count, ACT_DECLINE);
1408                         act_delta = m->act_count;
1409                 }
1410
1411                 /*
1412                  * Move this page to the tail of the active or inactive
1413                  * queue depending on usage.
1414                  */
1415                 if (act_delta == 0) {
1416                         /* Dequeue to avoid later lock recursion. */
1417                         vm_page_dequeue_locked(m);
1418                         vm_page_deactivate(m);
1419                         page_shortage--;
1420                 } else
1421                         vm_page_requeue_locked(m);
1422                 vm_page_unlock(m);
1423                 m = next;
1424         }
1425         vm_pagequeue_unlock(pq);
1426 #if !defined(NO_SWAPPING)
1427         /*
1428          * Idle process swapout -- run once per second.
1429          */
1430         if (vm_swap_idle_enabled) {
1431                 static long lsec;
1432                 if (time_second != lsec) {
1433                         vm_req_vmdaemon(VM_SWAP_IDLE);
1434                         lsec = time_second;
1435                 }
1436         }
1437 #endif
1438
1439         /*
1440          * If we are critically low on one of RAM or swap and low on
1441          * the other, kill the largest process.  However, we avoid
1442          * doing this on the first pass in order to give ourselves a
1443          * chance to flush out dirty vnode-backed pages and to allow
1444          * active pages to be moved to the inactive queue and reclaimed.
1445          */
1446         vm_pageout_mightbe_oom(vmd, pass);
1447 }
1448
1449 static int vm_pageout_oom_vote;
1450
1451 /*
1452  * The pagedaemon threads randlomly select one to perform the
1453  * OOM.  Trying to kill processes before all pagedaemons
1454  * failed to reach free target is premature.
1455  */
1456 static void
1457 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
1458 {
1459         int old_vote;
1460
1461         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
1462             (swap_pager_full && vm_paging_target() > 0))) {
1463                 if (vmd->vmd_oom) {
1464                         vmd->vmd_oom = FALSE;
1465                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1466                 }
1467                 return;
1468         }
1469
1470         if (vmd->vmd_oom)
1471                 return;
1472
1473         vmd->vmd_oom = TRUE;
1474         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1475         if (old_vote != vm_ndomains - 1)
1476                 return;
1477
1478         /*
1479          * The current pagedaemon thread is the last in the quorum to
1480          * start OOM.  Initiate the selection and signaling of the
1481          * victim.
1482          */
1483         vm_pageout_oom(VM_OOM_MEM);
1484
1485         /*
1486          * After one round of OOM terror, recall our vote.  On the
1487          * next pass, current pagedaemon would vote again if the low
1488          * memory condition is still there, due to vmd_oom being
1489          * false.
1490          */
1491         vmd->vmd_oom = FALSE;
1492         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1493 }
1494
1495 void
1496 vm_pageout_oom(int shortage)
1497 {
1498         struct proc *p, *bigproc;
1499         vm_offset_t size, bigsize;
1500         struct thread *td;
1501         struct vmspace *vm;
1502
1503         /*
1504          * We keep the process bigproc locked once we find it to keep anyone
1505          * from messing with it; however, there is a possibility of
1506          * deadlock if process B is bigproc and one of it's child processes
1507          * attempts to propagate a signal to B while we are waiting for A's
1508          * lock while walking this list.  To avoid this, we don't block on
1509          * the process lock but just skip a process if it is already locked.
1510          */
1511         bigproc = NULL;
1512         bigsize = 0;
1513         sx_slock(&allproc_lock);
1514         FOREACH_PROC_IN_SYSTEM(p) {
1515                 int breakout;
1516
1517                 if (PROC_TRYLOCK(p) == 0)
1518                         continue;
1519                 /*
1520                  * If this is a system, protected or killed process, skip it.
1521                  */
1522                 if (p->p_state != PRS_NORMAL ||
1523                     (p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
1524                     (p->p_pid == 1) || P_KILLED(p) ||
1525                     ((p->p_pid < 48) && (swap_pager_avail != 0))) {
1526                         PROC_UNLOCK(p);
1527                         continue;
1528                 }
1529                 /*
1530                  * If the process is in a non-running type state,
1531                  * don't touch it.  Check all the threads individually.
1532                  */
1533                 breakout = 0;
1534                 FOREACH_THREAD_IN_PROC(p, td) {
1535                         thread_lock(td);
1536                         if (!TD_ON_RUNQ(td) &&
1537                             !TD_IS_RUNNING(td) &&
1538                             !TD_IS_SLEEPING(td) &&
1539                             !TD_IS_SUSPENDED(td)) {
1540                                 thread_unlock(td);
1541                                 breakout = 1;
1542                                 break;
1543                         }
1544                         thread_unlock(td);
1545                 }
1546                 if (breakout) {
1547                         PROC_UNLOCK(p);
1548                         continue;
1549                 }
1550                 /*
1551                  * get the process size
1552                  */
1553                 vm = vmspace_acquire_ref(p);
1554                 if (vm == NULL) {
1555                         PROC_UNLOCK(p);
1556                         continue;
1557                 }
1558                 if (!vm_map_trylock_read(&vm->vm_map)) {
1559                         vmspace_free(vm);
1560                         PROC_UNLOCK(p);
1561                         continue;
1562                 }
1563                 size = vmspace_swap_count(vm);
1564                 vm_map_unlock_read(&vm->vm_map);
1565                 if (shortage == VM_OOM_MEM)
1566                         size += vmspace_resident_count(vm);
1567                 vmspace_free(vm);
1568                 /*
1569                  * if the this process is bigger than the biggest one
1570                  * remember it.
1571                  */
1572                 if (size > bigsize) {
1573                         if (bigproc != NULL)
1574                                 PROC_UNLOCK(bigproc);
1575                         bigproc = p;
1576                         bigsize = size;
1577                 } else
1578                         PROC_UNLOCK(p);
1579         }
1580         sx_sunlock(&allproc_lock);
1581         if (bigproc != NULL) {
1582                 killproc(bigproc, "out of swap space");
1583                 sched_nice(bigproc, PRIO_MIN);
1584                 PROC_UNLOCK(bigproc);
1585                 wakeup(&cnt.v_free_count);
1586         }
1587 }
1588
1589 static void
1590 vm_pageout_worker(void *arg)
1591 {
1592         struct vm_domain *domain;
1593         int domidx;
1594
1595         domidx = (uintptr_t)arg;
1596         domain = &vm_dom[domidx];
1597
1598         /*
1599          * XXXKIB It could be useful to bind pageout daemon threads to
1600          * the cores belonging to the domain, from which vm_page_array
1601          * is allocated.
1602          */
1603
1604         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
1605         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
1606
1607         /*
1608          * The pageout daemon worker is never done, so loop forever.
1609          */
1610         while (TRUE) {
1611                 /*
1612                  * If we have enough free memory, wakeup waiters.  Do
1613                  * not clear vm_pages_needed until we reach our target,
1614                  * otherwise we may be woken up over and over again and
1615                  * waste a lot of cpu.
1616                  */
1617                 mtx_lock(&vm_page_queue_free_mtx);
1618                 if (vm_pages_needed && !vm_page_count_min()) {
1619                         if (!vm_paging_needed())
1620                                 vm_pages_needed = 0;
1621                         wakeup(&cnt.v_free_count);
1622                 }
1623                 if (vm_pages_needed) {
1624                         /*
1625                          * Still not done, take a second pass without waiting
1626                          * (unlimited dirty cleaning), otherwise sleep a bit
1627                          * and try again.
1628                          */
1629                         if (domain->vmd_pass > 1)
1630                                 msleep(&vm_pages_needed,
1631                                     &vm_page_queue_free_mtx, PVM, "psleep",
1632                                     hz / 2);
1633                 } else {
1634                         /*
1635                          * Good enough, sleep until required to refresh
1636                          * stats.
1637                          */
1638                         domain->vmd_pass = 0;
1639                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
1640                             PVM, "psleep", hz);
1641
1642                 }
1643                 if (vm_pages_needed) {
1644                         cnt.v_pdwakeups++;
1645                         domain->vmd_pass++;
1646                 }
1647                 mtx_unlock(&vm_page_queue_free_mtx);
1648                 vm_pageout_scan(domain, domain->vmd_pass);
1649         }
1650 }
1651
1652 /*
1653  *      vm_pageout is the high level pageout daemon.
1654  */
1655 static void
1656 vm_pageout(void)
1657 {
1658 #if MAXMEMDOM > 1
1659         int error, i;
1660 #endif
1661
1662         /*
1663          * Initialize some paging parameters.
1664          */
1665         cnt.v_interrupt_free_min = 2;
1666         if (cnt.v_page_count < 2000)
1667                 vm_pageout_page_count = 8;
1668
1669         /*
1670          * v_free_reserved needs to include enough for the largest
1671          * swap pager structures plus enough for any pv_entry structs
1672          * when paging.
1673          */
1674         if (cnt.v_page_count > 1024)
1675                 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1676         else
1677                 cnt.v_free_min = 4;
1678         cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1679             cnt.v_interrupt_free_min;
1680         cnt.v_free_reserved = vm_pageout_page_count +
1681             cnt.v_pageout_free_min + (cnt.v_page_count / 768);
1682         cnt.v_free_severe = cnt.v_free_min / 2;
1683         cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1684         cnt.v_free_min += cnt.v_free_reserved;
1685         cnt.v_free_severe += cnt.v_free_reserved;
1686         cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1687         if (cnt.v_inactive_target > cnt.v_free_count / 3)
1688                 cnt.v_inactive_target = cnt.v_free_count / 3;
1689
1690         /*
1691          * Set the default wakeup threshold to be 10% above the minimum
1692          * page limit.  This keeps the steady state out of shortfall.
1693          */
1694         vm_pageout_wakeup_thresh = (cnt.v_free_min / 10) * 11;
1695
1696         /*
1697          * Set interval in seconds for active scan.  We want to visit each
1698          * page at least once every ten minutes.  This is to prevent worst
1699          * case paging behaviors with stale active LRU.
1700          */
1701         if (vm_pageout_update_period == 0)
1702                 vm_pageout_update_period = 600;
1703
1704         /* XXX does not really belong here */
1705         if (vm_page_max_wired == 0)
1706                 vm_page_max_wired = cnt.v_free_count / 3;
1707
1708         swap_pager_swap_init();
1709 #if MAXMEMDOM > 1
1710         for (i = 1; i < vm_ndomains; i++) {
1711                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
1712                     curproc, NULL, 0, 0, "dom%d", i);
1713                 if (error != 0) {
1714                         panic("starting pageout for domain %d, error %d\n",
1715                             i, error);
1716                 }
1717         }
1718 #endif
1719         vm_pageout_worker((void *)(uintptr_t)0);
1720 }
1721
1722 /*
1723  * Unless the free page queue lock is held by the caller, this function
1724  * should be regarded as advisory.  Specifically, the caller should
1725  * not msleep() on &cnt.v_free_count following this function unless
1726  * the free page queue lock is held until the msleep() is performed.
1727  */
1728 void
1729 pagedaemon_wakeup(void)
1730 {
1731
1732         if (!vm_pages_needed && curthread->td_proc != pageproc) {
1733                 vm_pages_needed = 1;
1734                 wakeup(&vm_pages_needed);
1735         }
1736 }
1737
1738 #if !defined(NO_SWAPPING)
1739 static void
1740 vm_req_vmdaemon(int req)
1741 {
1742         static int lastrun = 0;
1743
1744         mtx_lock(&vm_daemon_mtx);
1745         vm_pageout_req_swapout |= req;
1746         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1747                 wakeup(&vm_daemon_needed);
1748                 lastrun = ticks;
1749         }
1750         mtx_unlock(&vm_daemon_mtx);
1751 }
1752
1753 static void
1754 vm_daemon(void)
1755 {
1756         struct rlimit rsslim;
1757         struct proc *p;
1758         struct thread *td;
1759         struct vmspace *vm;
1760         int breakout, swapout_flags, tryagain, attempts;
1761 #ifdef RACCT
1762         uint64_t rsize, ravailable;
1763 #endif
1764
1765         while (TRUE) {
1766                 mtx_lock(&vm_daemon_mtx);
1767 #ifdef RACCT
1768                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
1769 #else
1770                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
1771 #endif
1772                 swapout_flags = vm_pageout_req_swapout;
1773                 vm_pageout_req_swapout = 0;
1774                 mtx_unlock(&vm_daemon_mtx);
1775                 if (swapout_flags)
1776                         swapout_procs(swapout_flags);
1777
1778                 /*
1779                  * scan the processes for exceeding their rlimits or if
1780                  * process is swapped out -- deactivate pages
1781                  */
1782                 tryagain = 0;
1783                 attempts = 0;
1784 again:
1785                 attempts++;
1786                 sx_slock(&allproc_lock);
1787                 FOREACH_PROC_IN_SYSTEM(p) {
1788                         vm_pindex_t limit, size;
1789
1790                         /*
1791                          * if this is a system process or if we have already
1792                          * looked at this process, skip it.
1793                          */
1794                         PROC_LOCK(p);
1795                         if (p->p_state != PRS_NORMAL ||
1796                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1797                                 PROC_UNLOCK(p);
1798                                 continue;
1799                         }
1800                         /*
1801                          * if the process is in a non-running type state,
1802                          * don't touch it.
1803                          */
1804                         breakout = 0;
1805                         FOREACH_THREAD_IN_PROC(p, td) {
1806                                 thread_lock(td);
1807                                 if (!TD_ON_RUNQ(td) &&
1808                                     !TD_IS_RUNNING(td) &&
1809                                     !TD_IS_SLEEPING(td) &&
1810                                     !TD_IS_SUSPENDED(td)) {
1811                                         thread_unlock(td);
1812                                         breakout = 1;
1813                                         break;
1814                                 }
1815                                 thread_unlock(td);
1816                         }
1817                         if (breakout) {
1818                                 PROC_UNLOCK(p);
1819                                 continue;
1820                         }
1821                         /*
1822                          * get a limit
1823                          */
1824                         lim_rlimit(p, RLIMIT_RSS, &rsslim);
1825                         limit = OFF_TO_IDX(
1826                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
1827
1828                         /*
1829                          * let processes that are swapped out really be
1830                          * swapped out set the limit to nothing (will force a
1831                          * swap-out.)
1832                          */
1833                         if ((p->p_flag & P_INMEM) == 0)
1834                                 limit = 0;      /* XXX */
1835                         vm = vmspace_acquire_ref(p);
1836                         PROC_UNLOCK(p);
1837                         if (vm == NULL)
1838                                 continue;
1839
1840                         size = vmspace_resident_count(vm);
1841                         if (size >= limit) {
1842                                 vm_pageout_map_deactivate_pages(
1843                                     &vm->vm_map, limit);
1844                         }
1845 #ifdef RACCT
1846                         rsize = IDX_TO_OFF(size);
1847                         PROC_LOCK(p);
1848                         racct_set(p, RACCT_RSS, rsize);
1849                         ravailable = racct_get_available(p, RACCT_RSS);
1850                         PROC_UNLOCK(p);
1851                         if (rsize > ravailable) {
1852                                 /*
1853                                  * Don't be overly aggressive; this might be
1854                                  * an innocent process, and the limit could've
1855                                  * been exceeded by some memory hog.  Don't
1856                                  * try to deactivate more than 1/4th of process'
1857                                  * resident set size.
1858                                  */
1859                                 if (attempts <= 8) {
1860                                         if (ravailable < rsize - (rsize / 4))
1861                                                 ravailable = rsize - (rsize / 4);
1862                                 }
1863                                 vm_pageout_map_deactivate_pages(
1864                                     &vm->vm_map, OFF_TO_IDX(ravailable));
1865                                 /* Update RSS usage after paging out. */
1866                                 size = vmspace_resident_count(vm);
1867                                 rsize = IDX_TO_OFF(size);
1868                                 PROC_LOCK(p);
1869                                 racct_set(p, RACCT_RSS, rsize);
1870                                 PROC_UNLOCK(p);
1871                                 if (rsize > ravailable)
1872                                         tryagain = 1;
1873                         }
1874 #endif
1875                         vmspace_free(vm);
1876                 }
1877                 sx_sunlock(&allproc_lock);
1878                 if (tryagain != 0 && attempts <= 10)
1879                         goto again;
1880         }
1881 }
1882 #endif                  /* !defined(NO_SWAPPING) */