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 "opt_kdtrace.h"
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/eventhandler.h>
  84 #include <sys/lock.h>
  85 #include <sys/mutex.h>
  86 #include <sys/proc.h>
  87 #include <sys/kthread.h>
  88 #include <sys/ktr.h>
  89 #include <sys/mount.h>
  90 #include <sys/racct.h>
  91 #include <sys/resourcevar.h>
  92 #include <sys/sched.h>
  93 #include <sys/sdt.h>
  94 #include <sys/signalvar.h>
  95 #include <sys/smp.h>
  96 #include <sys/time.h>
  97 #include <sys/vnode.h>
  98 #include <sys/vmmeter.h>
  99 #include <sys/rwlock.h>
 100 #include <sys/sx.h>
 101 #include <sys/sysctl.h>
 102
 103 #include <vm/vm.h>
 104 #include <vm/vm_param.h>
 105 #include <vm/vm_object.h>
 106 #include <vm/vm_page.h>
 107 #include <vm/vm_map.h>
 108 #include <vm/vm_pageout.h>
 109 #include <vm/vm_pager.h>
 110 #include <vm/vm_phys.h>
 111 #include <vm/swap_pager.h>
 112 #include <vm/vm_extern.h>
 113 #include <vm/uma.h>
 114
 115 /*
 116  * System initialization
 117  */
 118
 119 /* the kernel process "vm_pageout"*/
 120 static void vm_pageout(void);
 121 static void vm_pageout_init(void);
 122 static int vm_pageout_clean(vm_page_t m);
 123 static int vm_pageout_cluster(vm_page_t m);
 124 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
 125 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
 126
 127 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
 128     NULL);
 129
 130 struct proc *pageproc;
 131
 132 static struct kproc_desc page_kp = {
 133         "pagedaemon",
 134         vm_pageout,
 135         &pageproc
 136 };
 137 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
 138     &page_kp);
 139
 140 SDT_PROVIDER_DEFINE(vm);
 141 SDT_PROBE_DEFINE(vm, , , vm__lowmem_cache);
 142 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
 143
 144 #if !defined(NO_SWAPPING)
 145 /* the kernel process "vm_daemon"*/
 146 static void vm_daemon(void);
 147 static struct   proc *vmproc;
 148
 149 static struct kproc_desc vm_kp = {
 150         "vmdaemon",
 151         vm_daemon,
 152         &vmproc
 153 };
 154 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
 155 #endif
 156
 157
 158 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
 159 int vm_pageout_deficit;         /* Estimated number of pages deficit */
 160 int vm_pageout_wakeup_thresh;
 161
 162 #if !defined(NO_SWAPPING)
 163 static int vm_pageout_req_swapout;      /* XXX */
 164 static int vm_daemon_needed;
 165 static struct mtx vm_daemon_mtx;
 166 /* Allow for use by vm_pageout before vm_daemon is initialized. */
 167 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 168 #endif
 169 static int vm_max_launder = 32;
 170 static int vm_pageout_update_period;
 171 static int defer_swap_pageouts;
 172 static int disable_swap_pageouts;
 173 static int lowmem_period = 10;
 174 static time_t lowmem_uptime;
 175
 176 #if defined(NO_SWAPPING)
 177 static int vm_swap_enabled = 0;
 178 static int vm_swap_idle_enabled = 0;
 179 #else
 180 static int vm_swap_enabled = 1;
 181 static int vm_swap_idle_enabled = 0;
 182 #endif
 183
 184 static int vm_panic_on_oom = 0;
 185
 186 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
 187         CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
 188         "panic on out of memory instead of killing the largest process");
 189
 190 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
 191         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
 192         "free page threshold for waking up the pageout daemon");
 193
 194 SYSCTL_INT(_vm, OID_AUTO, max_launder,
 195         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
 196
 197 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
 198         CTLFLAG_RW, &vm_pageout_update_period, 0,
 199         "Maximum active LRU update period");
 200
 201 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
 202         "Low memory callback period");
 203
 204 #if defined(NO_SWAPPING)
 205 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 206         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
 207 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 208         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 209 #else
 210 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 211         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
 212 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 213         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 214 #endif
 215
 216 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
 217         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
 218
 219 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
 220         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
 221
 222 static int pageout_lock_miss;
 223 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 224         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 225
 226 #define VM_PAGEOUT_PAGE_COUNT 16
 227 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
 228
 229 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
 230 SYSCTL_INT(_vm, OID_AUTO, max_wired,
 231         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
 232
 233 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
 234 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
 235     vm_paddr_t);
 236 #if !defined(NO_SWAPPING)
 237 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
 238 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
 239 static void vm_req_vmdaemon(int req);
 240 #endif
 241 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 242
 243 /*
 244  * Initialize a dummy page for marking the caller's place in the specified
 245  * paging queue.  In principle, this function only needs to set the flag
 246  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
 247  * to one as safety precautions.
 248  */
 249 static void
 250 vm_pageout_init_marker(vm_page_t marker, u_short queue)
 251 {
 252
 253         bzero(marker, sizeof(*marker));
 254         marker->flags = PG_MARKER;
 255         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
 256         marker->queue = queue;
 257         marker->hold_count = 1;
 258 }
 259
 260 /*
 261  * vm_pageout_fallback_object_lock:
 262  *
 263  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
 264  * known to have failed and page queue must be either PQ_ACTIVE or
 265  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
 266  * while locking the vm object.  Use marker page to detect page queue
 267  * changes and maintain notion of next page on page queue.  Return
 268  * TRUE if no changes were detected, FALSE otherwise.  vm object is
 269  * locked on return.
 270  *
 271  * This function depends on both the lock portion of struct vm_object
 272  * and normal struct vm_page being type stable.
 273  */
 274 static boolean_t
 275 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
 276 {
 277         struct vm_page marker;
 278         struct vm_pagequeue *pq;
 279         boolean_t unchanged;
 280         u_short queue;
 281         vm_object_t object;
 282
 283         queue = m->queue;
 284         vm_pageout_init_marker(&marker, queue);
 285         pq = vm_page_pagequeue(m);
 286         object = m->object;
 287
 288         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 289         vm_pagequeue_unlock(pq);
 290         vm_page_unlock(m);
 291         VM_OBJECT_WLOCK(object);
 292         vm_page_lock(m);
 293         vm_pagequeue_lock(pq);
 294
 295         /* Page queue might have changed. */
 296         *next = TAILQ_NEXT(&marker, plinks.q);
 297         unchanged = (m->queue == queue &&
 298                      m->object == object &&
 299                      &marker == TAILQ_NEXT(m, plinks.q));
 300         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 301         return (unchanged);
 302 }
 303
 304 /*
 305  * Lock the page while holding the page queue lock.  Use marker page
 306  * to detect page queue changes and maintain notion of next page on
 307  * page queue.  Return TRUE if no changes were detected, FALSE
 308  * otherwise.  The page is locked on return. The page queue lock might
 309  * be dropped and reacquired.
 310  *
 311  * This function depends on normal struct vm_page being type stable.
 312  */
 313 static boolean_t
 314 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
 315 {
 316         struct vm_page marker;
 317         struct vm_pagequeue *pq;
 318         boolean_t unchanged;
 319         u_short queue;
 320
 321         vm_page_lock_assert(m, MA_NOTOWNED);
 322         if (vm_page_trylock(m))
 323                 return (TRUE);
 324
 325         queue = m->queue;
 326         vm_pageout_init_marker(&marker, queue);
 327         pq = vm_page_pagequeue(m);
 328
 329         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 330         vm_pagequeue_unlock(pq);
 331         vm_page_lock(m);
 332         vm_pagequeue_lock(pq);
 333
 334         /* Page queue might have changed. */
 335         *next = TAILQ_NEXT(&marker, plinks.q);
 336         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
 337         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 338         return (unchanged);
 339 }
 340
 341 /*
 342  * vm_pageout_clean:
 343  *
 344  * Clean the page and remove it from the laundry.
 345  *
 346  * We set the busy bit to cause potential page faults on this page to
 347  * block.  Note the careful timing, however, the busy bit isn't set till
 348  * late and we cannot do anything that will mess with the page.
 349  */
 350 static int
 351 vm_pageout_cluster(vm_page_t m)
 352 {
 353         vm_object_t object;
 354         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
 355         int pageout_count;
 356         int ib, is, page_base;
 357         vm_pindex_t pindex = m->pindex;
 358
 359         vm_page_lock_assert(m, MA_OWNED);
 360         object = m->object;
 361         VM_OBJECT_ASSERT_WLOCKED(object);
 362
 363         /*
 364          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
 365          * with the new swapper, but we could have serious problems paging
 366          * out other object types if there is insufficient memory.
 367          *
 368          * Unfortunately, checking free memory here is far too late, so the
 369          * check has been moved up a procedural level.
 370          */
 371
 372         /*
 373          * Can't clean the page if it's busy or held.
 374          */
 375         vm_page_assert_unbusied(m);
 376         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
 377         vm_page_unlock(m);
 378
 379         mc[vm_pageout_page_count] = pb = ps = m;
 380         pageout_count = 1;
 381         page_base = vm_pageout_page_count;
 382         ib = 1;
 383         is = 1;
 384
 385         /*
 386          * Scan object for clusterable pages.
 387          *
 388          * We can cluster ONLY if: ->> the page is NOT
 389          * clean, wired, busy, held, or mapped into a
 390          * buffer, and one of the following:
 391          * 1) The page is inactive, or a seldom used
 392          *    active page.
 393          * -or-
 394          * 2) we force the issue.
 395          *
 396          * During heavy mmap/modification loads the pageout
 397          * daemon can really fragment the underlying file
 398          * due to flushing pages out of order and not trying
 399          * align the clusters (which leave sporatic out-of-order
 400          * holes).  To solve this problem we do the reverse scan
 401          * first and attempt to align our cluster, then do a
 402          * forward scan if room remains.
 403          */
 404 more:
 405         while (ib && pageout_count < vm_pageout_page_count) {
 406                 vm_page_t p;
 407
 408                 if (ib > pindex) {
 409                         ib = 0;
 410                         break;
 411                 }
 412
 413                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
 414                         ib = 0;
 415                         break;
 416                 }
 417                 vm_page_test_dirty(p);
 418                 if (p->dirty == 0) {
 419                         ib = 0;
 420                         break;
 421                 }
 422                 vm_page_lock(p);
 423                 if (p->queue != PQ_INACTIVE ||
 424                     p->hold_count != 0) {       /* may be undergoing I/O */
 425                         vm_page_unlock(p);
 426                         ib = 0;
 427                         break;
 428                 }
 429                 vm_page_unlock(p);
 430                 mc[--page_base] = pb = p;
 431                 ++pageout_count;
 432                 ++ib;
 433                 /*
 434                  * alignment boundry, stop here and switch directions.  Do
 435                  * not clear ib.
 436                  */
 437                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 438                         break;
 439         }
 440
 441         while (pageout_count < vm_pageout_page_count &&
 442             pindex + is < object->size) {
 443                 vm_page_t p;
 444
 445                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
 446                         break;
 447                 vm_page_test_dirty(p);
 448                 if (p->dirty == 0)
 449                         break;
 450                 vm_page_lock(p);
 451                 if (p->queue != PQ_INACTIVE ||
 452                     p->hold_count != 0) {       /* may be undergoing I/O */
 453                         vm_page_unlock(p);
 454                         break;
 455                 }
 456                 vm_page_unlock(p);
 457                 mc[page_base + pageout_count] = ps = p;
 458                 ++pageout_count;
 459                 ++is;
 460         }
 461
 462         /*
 463          * If we exhausted our forward scan, continue with the reverse scan
 464          * when possible, even past a page boundry.  This catches boundry
 465          * conditions.
 466          */
 467         if (ib && pageout_count < vm_pageout_page_count)
 468                 goto more;
 469
 470         /*
 471          * we allow reads during pageouts...
 472          */
 473         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
 474             NULL));
 475 }
 476
 477 /*
 478  * vm_pageout_flush() - launder the given pages
 479  *
 480  *      The given pages are laundered.  Note that we setup for the start of
 481  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
 482  *      reference count all in here rather then in the parent.  If we want
 483  *      the parent to do more sophisticated things we may have to change
 484  *      the ordering.
 485  *
 486  *      Returned runlen is the count of pages between mreq and first
 487  *      page after mreq with status VM_PAGER_AGAIN.
 488  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
 489  *      for any page in runlen set.
 490  */
 491 int
 492 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
 493     boolean_t *eio)
 494 {
 495         vm_object_t object = mc[0]->object;
 496         int pageout_status[count];
 497         int numpagedout = 0;
 498         int i, runlen;
 499
 500         VM_OBJECT_ASSERT_WLOCKED(object);
 501
 502         /*
 503          * Initiate I/O.  Bump the vm_page_t->busy counter and
 504          * mark the pages read-only.
 505          *
 506          * We do not have to fixup the clean/dirty bits here... we can
 507          * allow the pager to do it after the I/O completes.
 508          *
 509          * NOTE! mc[i]->dirty may be partial or fragmented due to an
 510          * edge case with file fragments.
 511          */
 512         for (i = 0; i < count; i++) {
 513                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
 514                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
 515                         mc[i], i, count));
 516                 vm_page_sbusy(mc[i]);
 517                 pmap_remove_write(mc[i]);
 518         }
 519         vm_object_pip_add(object, count);
 520
 521         vm_pager_put_pages(object, mc, count, flags, pageout_status);
 522
 523         runlen = count - mreq;
 524         if (eio != NULL)
 525                 *eio = FALSE;
 526         for (i = 0; i < count; i++) {
 527                 vm_page_t mt = mc[i];
 528
 529                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
 530                     !pmap_page_is_write_mapped(mt),
 531                     ("vm_pageout_flush: page %p is not write protected", mt));
 532                 switch (pageout_status[i]) {
 533                 case VM_PAGER_OK:
 534                 case VM_PAGER_PEND:
 535                         numpagedout++;
 536                         break;
 537                 case VM_PAGER_BAD:
 538                         /*
 539                          * Page outside of range of object. Right now we
 540                          * essentially lose the changes by pretending it
 541                          * worked.
 542                          */
 543                         vm_page_undirty(mt);
 544                         break;
 545                 case VM_PAGER_ERROR:
 546                 case VM_PAGER_FAIL:
 547                         /*
 548                          * If page couldn't be paged out, then reactivate the
 549                          * page so it doesn't clog the inactive list.  (We
 550                          * will try paging out it again later).
 551                          */
 552                         vm_page_lock(mt);
 553                         vm_page_activate(mt);
 554                         vm_page_unlock(mt);
 555                         if (eio != NULL && i >= mreq && i - mreq < runlen)
 556                                 *eio = TRUE;
 557                         break;
 558                 case VM_PAGER_AGAIN:
 559                         if (i >= mreq && i - mreq < runlen)
 560                                 runlen = i - mreq;
 561                         break;
 562                 }
 563
 564                 /*
 565                  * If the operation is still going, leave the page busy to
 566                  * block all other accesses. Also, leave the paging in
 567                  * progress indicator set so that we don't attempt an object
 568                  * collapse.
 569                  */
 570                 if (pageout_status[i] != VM_PAGER_PEND) {
 571                         vm_object_pip_wakeup(object);
 572                         vm_page_sunbusy(mt);
 573                 }
 574         }
 575         if (prunlen != NULL)
 576                 *prunlen = runlen;
 577         return (numpagedout);
 578 }
 579
 580 static boolean_t
 581 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
 582     vm_paddr_t high)
 583 {
 584         struct mount *mp;
 585         struct vnode *vp;
 586         vm_object_t object;
 587         vm_paddr_t pa;
 588         vm_page_t m, m_tmp, next;
 589         int lockmode;
 590
 591         vm_pagequeue_lock(pq);
 592         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
 593                 if ((m->flags & PG_MARKER) != 0)
 594                         continue;
 595                 pa = VM_PAGE_TO_PHYS(m);
 596                 if (pa < low || pa + PAGE_SIZE > high)
 597                         continue;
 598                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
 599                         vm_page_unlock(m);
 600                         continue;
 601                 }
 602                 object = m->object;
 603                 if ((!VM_OBJECT_TRYWLOCK(object) &&
 604                     (!vm_pageout_fallback_object_lock(m, &next) ||
 605                     m->hold_count != 0)) || vm_page_busied(m)) {
 606                         vm_page_unlock(m);
 607                         VM_OBJECT_WUNLOCK(object);
 608                         continue;
 609                 }
 610                 vm_page_test_dirty(m);
 611                 if (m->dirty == 0 && object->ref_count != 0)
 612                         pmap_remove_all(m);
 613                 if (m->dirty != 0) {
 614                         vm_page_unlock(m);
 615                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
 616                                 VM_OBJECT_WUNLOCK(object);
 617                                 continue;
 618                         }
 619                         if (object->type == OBJT_VNODE) {
 620                                 vm_pagequeue_unlock(pq);
 621                                 vp = object->handle;
 622                                 vm_object_reference_locked(object);
 623                                 VM_OBJECT_WUNLOCK(object);
 624                                 (void)vn_start_write(vp, &mp, V_WAIT);
 625                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 626                                     LK_SHARED : LK_EXCLUSIVE;
 627                                 vn_lock(vp, lockmode | LK_RETRY);
 628                                 VM_OBJECT_WLOCK(object);
 629                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
 630                                 VM_OBJECT_WUNLOCK(object);
 631                                 VOP_UNLOCK(vp, 0);
 632                                 vm_object_deallocate(object);
 633                                 vn_finished_write(mp);
 634                                 return (TRUE);
 635                         } else if (object->type == OBJT_SWAP ||
 636                             object->type == OBJT_DEFAULT) {
 637                                 vm_pagequeue_unlock(pq);
 638                                 m_tmp = m;
 639                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
 640                                     0, NULL, NULL);
 641                                 VM_OBJECT_WUNLOCK(object);
 642                                 return (TRUE);
 643                         }
 644                 } else {
 645                         /*
 646                          * Dequeue here to prevent lock recursion in
 647                          * vm_page_cache().
 648                          */
 649                         vm_page_dequeue_locked(m);
 650                         vm_page_cache(m);
 651                         vm_page_unlock(m);
 652                 }
 653                 VM_OBJECT_WUNLOCK(object);
 654         }
 655         vm_pagequeue_unlock(pq);
 656         return (FALSE);
 657 }
 658
 659 /*
 660  * Increase the number of cached pages.  The specified value, "tries",
 661  * determines which categories of pages are cached:
 662  *
 663  *  0: All clean, inactive pages within the specified physical address range
 664  *     are cached.  Will not sleep.
 665  *  1: The vm_lowmem handlers are called.  All inactive pages within
 666  *     the specified physical address range are cached.  May sleep.
 667  *  2: The vm_lowmem handlers are called.  All inactive and active pages
 668  *     within the specified physical address range are cached.  May sleep.
 669  */
 670 void
 671 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
 672 {
 673         int actl, actmax, inactl, inactmax, dom, initial_dom;
 674         static int start_dom = 0;
 675
 676         if (tries > 0) {
 677                 /*
 678                  * Decrease registered cache sizes.  The vm_lowmem handlers
 679                  * may acquire locks and/or sleep, so they can only be invoked
 680                  * when "tries" is greater than zero.
 681                  */
 682                 SDT_PROBE0(vm, , , vm__lowmem_cache);
 683                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 684
 685                 /*
 686                  * We do this explicitly after the caches have been drained
 687                  * above.
 688                  */
 689                 uma_reclaim();
 690         }
 691
 692         /*
 693          * Make the next scan start on the next domain.
 694          */
 695         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
 696
 697         inactl = 0;
 698         inactmax = vm_cnt.v_inactive_count;
 699         actl = 0;
 700         actmax = tries < 2 ? 0 : vm_cnt.v_active_count;
 701         dom = initial_dom;
 702
 703         /*
 704          * Scan domains in round-robin order, first inactive queues,
 705          * then active.  Since domain usually owns large physically
 706          * contiguous chunk of memory, it makes sense to completely
 707          * exhaust one domain before switching to next, while growing
 708          * the pool of contiguous physical pages.
 709          *
 710          * Do not even start launder a domain which cannot contain
 711          * the specified address range, as indicated by segments
 712          * constituting the domain.
 713          */
 714 again:
 715         if (inactl < inactmax) {
 716                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 717                     low, high) &&
 718                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
 719                     tries, low, high)) {
 720                         inactl++;
 721                         goto again;
 722                 }
 723                 if (++dom == vm_ndomains)
 724                         dom = 0;
 725                 if (dom != initial_dom)
 726                         goto again;
 727         }
 728         if (actl < actmax) {
 729                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 730                     low, high) &&
 731                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
 732                       tries, low, high)) {
 733                         actl++;
 734                         goto again;
 735                 }
 736                 if (++dom == vm_ndomains)
 737                         dom = 0;
 738                 if (dom != initial_dom)
 739                         goto again;
 740         }
 741 }
 742
 743 #if !defined(NO_SWAPPING)
 744 /*
 745  *      vm_pageout_object_deactivate_pages
 746  *
 747  *      Deactivate enough pages to satisfy the inactive target
 748  *      requirements.
 749  *
 750  *      The object and map must be locked.
 751  */
 752 static void
 753 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 754     long desired)
 755 {
 756         vm_object_t backing_object, object;
 757         vm_page_t p;
 758         int act_delta, remove_mode;
 759
 760         VM_OBJECT_ASSERT_LOCKED(first_object);
 761         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 762                 return;
 763         for (object = first_object;; object = backing_object) {
 764                 if (pmap_resident_count(pmap) <= desired)
 765                         goto unlock_return;
 766                 VM_OBJECT_ASSERT_LOCKED(object);
 767                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 768                     object->paging_in_progress != 0)
 769                         goto unlock_return;
 770
 771                 remove_mode = 0;
 772                 if (object->shadow_count > 1)
 773                         remove_mode = 1;
 774                 /*
 775                  * Scan the object's entire memory queue.
 776                  */
 777                 TAILQ_FOREACH(p, &object->memq, listq) {
 778                         if (pmap_resident_count(pmap) <= desired)
 779                                 goto unlock_return;
 780                         if (vm_page_busied(p))
 781                                 continue;
 782                         PCPU_INC(cnt.v_pdpages);
 783                         vm_page_lock(p);
 784                         if (p->wire_count != 0 || p->hold_count != 0 ||
 785                             !pmap_page_exists_quick(pmap, p)) {
 786                                 vm_page_unlock(p);
 787                                 continue;
 788                         }
 789                         act_delta = pmap_ts_referenced(p);
 790                         if ((p->aflags & PGA_REFERENCED) != 0) {
 791                                 if (act_delta == 0)
 792                                         act_delta = 1;
 793                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 794                         }
 795                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
 796                                 vm_page_activate(p);
 797                                 p->act_count += act_delta;
 798                         } else if (p->queue == PQ_ACTIVE) {
 799                                 if (act_delta == 0) {
 800                                         p->act_count -= min(p->act_count,
 801                                             ACT_DECLINE);
 802                                         if (!remove_mode && p->act_count == 0) {
 803                                                 pmap_remove_all(p);
 804                                                 vm_page_deactivate(p);
 805                                         } else
 806                                                 vm_page_requeue(p);
 807                                 } else {
 808                                         vm_page_activate(p);
 809                                         if (p->act_count < ACT_MAX -
 810                                             ACT_ADVANCE)
 811                                                 p->act_count += ACT_ADVANCE;
 812                                         vm_page_requeue(p);
 813                                 }
 814                         } else if (p->queue == PQ_INACTIVE)
 815                                 pmap_remove_all(p);
 816                         vm_page_unlock(p);
 817                 }
 818                 if ((backing_object = object->backing_object) == NULL)
 819                         goto unlock_return;
 820                 VM_OBJECT_RLOCK(backing_object);
 821                 if (object != first_object)
 822                         VM_OBJECT_RUNLOCK(object);
 823         }
 824 unlock_return:
 825         if (object != first_object)
 826                 VM_OBJECT_RUNLOCK(object);
 827 }
 828
 829 /*
 830  * deactivate some number of pages in a map, try to do it fairly, but
 831  * that is really hard to do.
 832  */
 833 static void
 834 vm_pageout_map_deactivate_pages(map, desired)
 835         vm_map_t map;
 836         long desired;
 837 {
 838         vm_map_entry_t tmpe;
 839         vm_object_t obj, bigobj;
 840         int nothingwired;
 841
 842         if (!vm_map_trylock(map))
 843                 return;
 844
 845         bigobj = NULL;
 846         nothingwired = TRUE;
 847
 848         /*
 849          * first, search out the biggest object, and try to free pages from
 850          * that.
 851          */
 852         tmpe = map->header.next;
 853         while (tmpe != &map->header) {
 854                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 855                         obj = tmpe->object.vm_object;
 856                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 857                                 if (obj->shadow_count <= 1 &&
 858                                     (bigobj == NULL ||
 859                                      bigobj->resident_page_count < obj->resident_page_count)) {
 860                                         if (bigobj != NULL)
 861                                                 VM_OBJECT_RUNLOCK(bigobj);
 862                                         bigobj = obj;
 863                                 } else
 864                                         VM_OBJECT_RUNLOCK(obj);
 865                         }
 866                 }
 867                 if (tmpe->wired_count > 0)
 868                         nothingwired = FALSE;
 869                 tmpe = tmpe->next;
 870         }
 871
 872         if (bigobj != NULL) {
 873                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
 874                 VM_OBJECT_RUNLOCK(bigobj);
 875         }
 876         /*
 877          * Next, hunt around for other pages to deactivate.  We actually
 878          * do this search sort of wrong -- .text first is not the best idea.
 879          */
 880         tmpe = map->header.next;
 881         while (tmpe != &map->header) {
 882                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 883                         break;
 884                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 885                         obj = tmpe->object.vm_object;
 886                         if (obj != NULL) {
 887                                 VM_OBJECT_RLOCK(obj);
 888                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
 889                                 VM_OBJECT_RUNLOCK(obj);
 890                         }
 891                 }
 892                 tmpe = tmpe->next;
 893         }
 894
 895         /*
 896          * Remove all mappings if a process is swapped out, this will free page
 897          * table pages.
 898          */
 899         if (desired == 0 && nothingwired) {
 900                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 901                     vm_map_max(map));
 902         }
 903
 904         vm_map_unlock(map);
 905 }
 906 #endif          /* !defined(NO_SWAPPING) */
 907
 908 /*
 909  * Attempt to acquire all of the necessary locks to launder a page and
 910  * then call through the clustering layer to PUTPAGES.  Wait a short
 911  * time for a vnode lock.
 912  *
 913  * Requires the page and object lock on entry, releases both before return.
 914  * Returns 0 on success and an errno otherwise.
 915  */
 916 static int
 917 vm_pageout_clean(vm_page_t m)
 918 {
 919         struct vnode *vp;
 920         struct mount *mp;
 921         vm_object_t object;
 922         vm_pindex_t pindex;
 923         int error, lockmode;
 924
 925         vm_page_assert_locked(m);
 926         object = m->object;
 927         VM_OBJECT_ASSERT_WLOCKED(object);
 928         error = 0;
 929         vp = NULL;
 930         mp = NULL;
 931
 932         /*
 933          * The object is already known NOT to be dead.   It
 934          * is possible for the vget() to block the whole
 935          * pageout daemon, but the new low-memory handling
 936          * code should prevent it.
 937          *
 938          * We can't wait forever for the vnode lock, we might
 939          * deadlock due to a vn_read() getting stuck in
 940          * vm_wait while holding this vnode.  We skip the
 941          * vnode if we can't get it in a reasonable amount
 942          * of time.
 943          */
 944         if (object->type == OBJT_VNODE) {
 945                 vm_page_unlock(m);
 946                 vp = object->handle;
 947                 if (vp->v_type == VREG &&
 948                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 949                         mp = NULL;
 950                         error = EDEADLK;
 951                         goto unlock_all;
 952                 }
 953                 KASSERT(mp != NULL,
 954                     ("vp %p with NULL v_mount", vp));
 955                 vm_object_reference_locked(object);
 956                 pindex = m->pindex;
 957                 VM_OBJECT_WUNLOCK(object);
 958                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 959                     LK_SHARED : LK_EXCLUSIVE;
 960                 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
 961                         vp = NULL;
 962                         error = EDEADLK;
 963                         goto unlock_mp;
 964                 }
 965                 VM_OBJECT_WLOCK(object);
 966                 vm_page_lock(m);
 967                 /*
 968                  * While the object and page were unlocked, the page
 969                  * may have been:
 970                  * (1) moved to a different queue,
 971                  * (2) reallocated to a different object,
 972                  * (3) reallocated to a different offset, or
 973                  * (4) cleaned.
 974                  */
 975                 if (m->queue != PQ_INACTIVE || m->object != object ||
 976                     m->pindex != pindex || m->dirty == 0) {
 977                         vm_page_unlock(m);
 978                         error = ENXIO;
 979                         goto unlock_all;
 980                 }
 981
 982                 /*
 983                  * The page may have been busied or held while the object
 984                  * and page locks were released.
 985                  */
 986                 if (vm_page_busied(m) || m->hold_count != 0) {
 987                         vm_page_unlock(m);
 988                         error = EBUSY;
 989                         goto unlock_all;
 990                 }
 991         }
 992
 993         /*
 994          * If a page is dirty, then it is either being washed
 995          * (but not yet cleaned) or it is still in the
 996          * laundry.  If it is still in the laundry, then we
 997          * start the cleaning operation.
 998          */
 999         if (vm_pageout_cluster(m) == 0)
1000                 error = EIO;
1001
1002 unlock_all:
1003         VM_OBJECT_WUNLOCK(object);
1004
1005 unlock_mp:
1006         vm_page_lock_assert(m, MA_NOTOWNED);
1007         if (mp != NULL) {
1008                 if (vp != NULL)
1009                         vput(vp);
1010                 vm_object_deallocate(object);
1011                 vn_finished_write(mp);
1012         }
1013
1014         return (error);
1015 }
1016
1017 /*
1018  *      vm_pageout_scan does the dirty work for the pageout daemon.
1019  *
1020  *      pass 0 - Update active LRU/deactivate pages
1021  *      pass 1 - Move inactive to cache or free
1022  *      pass 2 - Launder dirty pages
1023  */
1024 static void
1025 vm_pageout_scan(struct vm_domain *vmd, int pass)
1026 {
1027         vm_page_t m, next;
1028         struct vm_pagequeue *pq;
1029         vm_object_t object;
1030         long min_scan;
1031         int act_delta, addl_page_shortage, deficit, error, maxlaunder, maxscan;
1032         int page_shortage, scan_tick, scanned, vnodes_skipped;
1033         boolean_t pageout_ok, queues_locked;
1034
1035         /*
1036          * If we need to reclaim memory ask kernel caches to return
1037          * some.  We rate limit to avoid thrashing.
1038          */
1039         if (vmd == &vm_dom[0] && pass > 0 &&
1040             (time_uptime - lowmem_uptime) >= lowmem_period) {
1041                 /*
1042                  * Decrease registered cache sizes.
1043                  */
1044                 SDT_PROBE0(vm, , , vm__lowmem_scan);
1045                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
1046                 /*
1047                  * We do this explicitly after the caches have been
1048                  * drained above.
1049                  */
1050                 uma_reclaim();
1051                 lowmem_uptime = time_uptime;
1052         }
1053
1054         /*
1055          * The addl_page_shortage is the number of temporarily
1056          * stuck pages in the inactive queue.  In other words, the
1057          * number of pages from the inactive count that should be
1058          * discounted in setting the target for the active queue scan.
1059          */
1060         addl_page_shortage = 0;
1061
1062         /*
1063          * Calculate the number of pages we want to either free or move
1064          * to the cache.
1065          */
1066         if (pass > 0) {
1067                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
1068                 page_shortage = vm_paging_target() + deficit;
1069         } else
1070                 page_shortage = deficit = 0;
1071
1072         /*
1073          * maxlaunder limits the number of dirty pages we flush per scan.
1074          * For most systems a smaller value (16 or 32) is more robust under
1075          * extreme memory and disk pressure because any unnecessary writes
1076          * to disk can result in extreme performance degredation.  However,
1077          * systems with excessive dirty pages (especially when MAP_NOSYNC is
1078          * used) will die horribly with limited laundering.  If the pageout
1079          * daemon cannot clean enough pages in the first pass, we let it go
1080          * all out in succeeding passes.
1081          */
1082         if ((maxlaunder = vm_max_launder) <= 1)
1083                 maxlaunder = 1;
1084         if (pass > 1)
1085                 maxlaunder = 10000;
1086
1087         vnodes_skipped = 0;
1088
1089         /*
1090          * Start scanning the inactive queue for pages we can move to the
1091          * cache or free.  The scan will stop when the target is reached or
1092          * we have scanned the entire inactive queue.  Note that m->act_count
1093          * is not used to form decisions for the inactive queue, only for the
1094          * active queue.
1095          */
1096         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
1097         maxscan = pq->pq_cnt;
1098         vm_pagequeue_lock(pq);
1099         queues_locked = TRUE;
1100         for (m = TAILQ_FIRST(&pq->pq_pl);
1101              m != NULL && maxscan-- > 0 && page_shortage > 0;
1102              m = next) {
1103                 vm_pagequeue_assert_locked(pq);
1104                 KASSERT(queues_locked, ("unlocked queues"));
1105                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
1106
1107                 PCPU_INC(cnt.v_pdpages);
1108                 next = TAILQ_NEXT(m, plinks.q);
1109
1110                 /*
1111                  * skip marker pages
1112                  */
1113                 if (m->flags & PG_MARKER)
1114                         continue;
1115
1116                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1117                     ("Fictitious page %p cannot be in inactive queue", m));
1118                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1119                     ("Unmanaged page %p cannot be in inactive queue", m));
1120
1121                 /*
1122                  * The page or object lock acquisitions fail if the
1123                  * page was removed from the queue or moved to a
1124                  * different position within the queue.  In either
1125                  * case, addl_page_shortage should not be incremented.
1126                  */
1127                 if (!vm_pageout_page_lock(m, &next))
1128                         goto unlock_page;
1129                 else if (m->hold_count != 0) {
1130                         /*
1131                          * Held pages are essentially stuck in the
1132                          * queue.  So, they ought to be discounted
1133                          * from the inactive count.  See the
1134                          * calculation of the page_shortage for the
1135                          * loop over the active queue below.
1136                          */
1137                         addl_page_shortage++;
1138                         goto unlock_page;
1139                 }
1140                 object = m->object;
1141                 if (!VM_OBJECT_TRYWLOCK(object)) {
1142                         if (!vm_pageout_fallback_object_lock(m, &next))
1143                                 goto unlock_object;
1144                         else if (m->hold_count != 0) {
1145                                 addl_page_shortage++;
1146                                 goto unlock_object;
1147                         }
1148                 }
1149                 if (vm_page_busied(m)) {
1150                         /*
1151                          * Don't mess with busy pages.  Leave them at
1152                          * the front of the queue.  Most likely, they
1153                          * are being paged out and will leave the
1154                          * queue shortly after the scan finishes.  So,
1155                          * they ought to be discounted from the
1156                          * inactive count.
1157                          */
1158                         addl_page_shortage++;
1159 unlock_object:
1160                         VM_OBJECT_WUNLOCK(object);
1161 unlock_page:
1162                         vm_page_unlock(m);
1163                         continue;
1164                 }
1165                 KASSERT(m->hold_count == 0, ("Held page %p", m));
1166
1167                 /*
1168                  * We unlock the inactive page queue, invalidating the
1169                  * 'next' pointer.  Use our marker to remember our
1170                  * place.
1171                  */
1172                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
1173                 vm_pagequeue_unlock(pq);
1174                 queues_locked = FALSE;
1175
1176                 /*
1177                  * Invalid pages cannot appear on a queue.  If
1178                  * vm_pageout_fallback_object_lock() allowed a window
1179                  * where the page could be invalidated, it should
1180                  * detect this.
1181                  */
1182                 KASSERT(m->valid != 0, ("Invalid page %p on inact queue", m));
1183
1184                 /*
1185                  * If the page has been referenced and the object is not dead,
1186                  * reactivate or requeue the page depending on whether the
1187                  * object is mapped.
1188                  */
1189                 if ((m->aflags & PGA_REFERENCED) != 0) {
1190                         vm_page_aflag_clear(m, PGA_REFERENCED);
1191                         act_delta = 1;
1192                 } else
1193                         act_delta = 0;
1194                 if (object->ref_count != 0) {
1195                         act_delta += pmap_ts_referenced(m);
1196                 } else {
1197                         KASSERT(!pmap_page_is_mapped(m),
1198                             ("vm_pageout_scan: page %p is mapped", m));
1199                 }
1200                 if (act_delta != 0) {
1201                         if (object->ref_count != 0) {
1202                                 vm_page_activate(m);
1203
1204                                 /*
1205                                  * Increase the activation count if the page
1206                                  * was referenced while in the inactive queue.
1207                                  * This makes it less likely that the page will
1208                                  * be returned prematurely to the inactive
1209                                  * queue.
1210                                  */
1211                                 m->act_count += act_delta + ACT_ADVANCE;
1212                                 goto drop_page;
1213                         } else if ((object->flags & OBJ_DEAD) == 0)
1214                                 goto requeue_page;
1215                 }
1216
1217                 /*
1218                  * If the page appears to be clean at the machine-independent
1219                  * layer, then remove all of its mappings from the pmap in
1220                  * anticipation of placing it onto the cache queue.  If,
1221                  * however, any of the page's mappings allow write access,
1222                  * then the page may still be modified until the last of those
1223                  * mappings are removed.
1224                  */
1225                 if (object->ref_count != 0) {
1226                         vm_page_test_dirty(m);
1227                         if (m->dirty == 0)
1228                                 pmap_remove_all(m);
1229                 }
1230
1231                 if (m->dirty == 0) {
1232                         /*
1233                          * Clean pages can be freed.
1234                          */
1235                         vm_page_free(m);
1236                         PCPU_INC(cnt.v_dfree);
1237                         --page_shortage;
1238                 } else if ((object->flags & OBJ_DEAD) != 0) {
1239                         /*
1240                          * Leave dirty pages from dead objects at the front of
1241                          * the queue.  They are being paged out and freed by
1242                          * the thread that destroyed the object.  They will
1243                          * leave the queue shortly after the scan finishes, so
1244                          * they should be discounted from the inactive count.
1245                          */
1246                         addl_page_shortage++;
1247                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
1248                         /*
1249                          * Dirty pages need to be paged out, but flushing
1250                          * a page is extremely expensive versus freeing
1251                          * a clean page.  Rather then artificially limiting
1252                          * the number of pages we can flush, we instead give
1253                          * dirty pages extra priority on the inactive queue
1254                          * by forcing them to be cycled through the queue
1255                          * twice before being flushed, after which the
1256                          * (now clean) page will cycle through once more
1257                          * before being freed.  This significantly extends
1258                          * the thrash point for a heavily loaded machine.
1259                          */
1260                         m->flags |= PG_WINATCFLS;
1261 requeue_page:
1262                         vm_pagequeue_lock(pq);
1263                         queues_locked = TRUE;
1264                         vm_page_requeue_locked(m);
1265                 } else if (maxlaunder > 0) {
1266                         /*
1267                          * We always want to try to flush some dirty pages if
1268                          * we encounter them, to keep the system stable.
1269                          * Normally this number is small, but under extreme
1270                          * pressure where there are insufficient clean pages
1271                          * on the inactive queue, we may have to go all out.
1272                          */
1273
1274                         if (object->type != OBJT_SWAP &&
1275                             object->type != OBJT_DEFAULT)
1276                                 pageout_ok = TRUE;
1277                         else if (disable_swap_pageouts)
1278                                 pageout_ok = FALSE;
1279                         else if (defer_swap_pageouts)
1280                                 pageout_ok = vm_page_count_min();
1281                         else
1282                                 pageout_ok = TRUE;
1283                         if (!pageout_ok)
1284                                 goto requeue_page;
1285                         error = vm_pageout_clean(m);
1286                         /*
1287                          * Decrement page_shortage on success to account for
1288                          * the (future) cleaned page.  Otherwise we could wind
1289                          * up laundering or cleaning too many pages.
1290                          */
1291                         if (error == 0) {
1292                                 page_shortage--;
1293                                 maxlaunder--;
1294                         } else if (error == EDEADLK) {
1295                                 pageout_lock_miss++;
1296                                 vnodes_skipped++;
1297                         } else if (error == EBUSY) {
1298                                 addl_page_shortage++;
1299                         }
1300                         vm_page_lock_assert(m, MA_NOTOWNED);
1301                         goto relock_queues;
1302                 }
1303 drop_page:
1304                 vm_page_unlock(m);
1305                 VM_OBJECT_WUNLOCK(object);
1306 relock_queues:
1307                 if (!queues_locked) {
1308                         vm_pagequeue_lock(pq);
1309                         queues_locked = TRUE;
1310                 }
1311                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
1312                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
1313         }
1314         vm_pagequeue_unlock(pq);
1315
1316 #if !defined(NO_SWAPPING)
1317         /*
1318          * Wakeup the swapout daemon if we didn't cache or free the targeted
1319          * number of pages.
1320          */
1321         if (vm_swap_enabled && page_shortage > 0)
1322                 vm_req_vmdaemon(VM_SWAP_NORMAL);
1323 #endif
1324
1325         /*
1326          * Wakeup the sync daemon if we skipped a vnode in a writeable object
1327          * and we didn't cache or free enough pages.
1328          */
1329         if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target -
1330             vm_cnt.v_free_min)
1331                 (void)speedup_syncer();
1332
1333         /*
1334          * Compute the number of pages we want to try to move from the
1335          * active queue to the inactive queue.
1336          */
1337         page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count +
1338             vm_paging_target() + deficit + addl_page_shortage;
1339
1340         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1341         vm_pagequeue_lock(pq);
1342         maxscan = pq->pq_cnt;
1343
1344         /*
1345          * If we're just idle polling attempt to visit every
1346          * active page within 'update_period' seconds.
1347          */
1348         scan_tick = ticks;
1349         if (vm_pageout_update_period != 0) {
1350                 min_scan = pq->pq_cnt;
1351                 min_scan *= scan_tick - vmd->vmd_last_active_scan;
1352                 min_scan /= hz * vm_pageout_update_period;
1353         } else
1354                 min_scan = 0;
1355         if (min_scan > 0 || (page_shortage > 0 && maxscan > 0))
1356                 vmd->vmd_last_active_scan = scan_tick;
1357
1358         /*
1359          * Scan the active queue for pages that can be deactivated.  Update
1360          * the per-page activity counter and use it to identify deactivation
1361          * candidates.
1362          */
1363         for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned <
1364             min_scan || (page_shortage > 0 && scanned < maxscan)); m = next,
1365             scanned++) {
1366
1367                 KASSERT(m->queue == PQ_ACTIVE,
1368                     ("vm_pageout_scan: page %p isn't active", m));
1369
1370                 next = TAILQ_NEXT(m, plinks.q);
1371                 if ((m->flags & PG_MARKER) != 0)
1372                         continue;
1373                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1374                     ("Fictitious page %p cannot be in active queue", m));
1375                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1376                     ("Unmanaged page %p cannot be in active queue", m));
1377                 if (!vm_pageout_page_lock(m, &next)) {
1378                         vm_page_unlock(m);
1379                         continue;
1380                 }
1381
1382                 /*
1383                  * The count for pagedaemon pages is done after checking the
1384                  * page for eligibility...
1385                  */
1386                 PCPU_INC(cnt.v_pdpages);
1387
1388                 /*
1389                  * Check to see "how much" the page has been used.
1390                  */
1391                 if ((m->aflags & PGA_REFERENCED) != 0) {
1392                         vm_page_aflag_clear(m, PGA_REFERENCED);
1393                         act_delta = 1;
1394                 } else
1395                         act_delta = 0;
1396
1397                 /*
1398                  * Unlocked object ref count check.  Two races are possible.
1399                  * 1) The ref was transitioning to zero and we saw non-zero,
1400                  *    the pmap bits will be checked unnecessarily.
1401                  * 2) The ref was transitioning to one and we saw zero.
1402                  *    The page lock prevents a new reference to this page so
1403                  *    we need not check the reference bits.
1404                  */
1405                 if (m->object->ref_count != 0)
1406                         act_delta += pmap_ts_referenced(m);
1407
1408                 /*
1409                  * Advance or decay the act_count based on recent usage.
1410                  */
1411                 if (act_delta != 0) {
1412                         m->act_count += ACT_ADVANCE + act_delta;
1413                         if (m->act_count > ACT_MAX)
1414                                 m->act_count = ACT_MAX;
1415                 } else
1416                         m->act_count -= min(m->act_count, ACT_DECLINE);
1417
1418                 /*
1419                  * Move this page to the tail of the active or inactive
1420                  * queue depending on usage.
1421                  */
1422                 if (m->act_count == 0) {
1423                         /* Dequeue to avoid later lock recursion. */
1424                         vm_page_dequeue_locked(m);
1425                         vm_page_deactivate(m);
1426                         page_shortage--;
1427                 } else
1428                         vm_page_requeue_locked(m);
1429                 vm_page_unlock(m);
1430         }
1431         vm_pagequeue_unlock(pq);
1432 #if !defined(NO_SWAPPING)
1433         /*
1434          * Idle process swapout -- run once per second.
1435          */
1436         if (vm_swap_idle_enabled) {
1437                 static long lsec;
1438                 if (time_second != lsec) {
1439                         vm_req_vmdaemon(VM_SWAP_IDLE);
1440                         lsec = time_second;
1441                 }
1442         }
1443 #endif
1444
1445         /*
1446          * If we are critically low on one of RAM or swap and low on
1447          * the other, kill the largest process.  However, we avoid
1448          * doing this on the first pass in order to give ourselves a
1449          * chance to flush out dirty vnode-backed pages and to allow
1450          * active pages to be moved to the inactive queue and reclaimed.
1451          */
1452         vm_pageout_mightbe_oom(vmd, pass);
1453 }
1454
1455 static int vm_pageout_oom_vote;
1456
1457 /*
1458  * The pagedaemon threads randlomly select one to perform the
1459  * OOM.  Trying to kill processes before all pagedaemons
1460  * failed to reach free target is premature.
1461  */
1462 static void
1463 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
1464 {
1465         int old_vote;
1466
1467         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
1468             (swap_pager_full && vm_paging_target() > 0))) {
1469                 if (vmd->vmd_oom) {
1470                         vmd->vmd_oom = FALSE;
1471                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1472                 }
1473                 return;
1474         }
1475
1476         if (vmd->vmd_oom)
1477                 return;
1478
1479         vmd->vmd_oom = TRUE;
1480         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1481         if (old_vote != vm_ndomains - 1)
1482                 return;
1483
1484         /*
1485          * The current pagedaemon thread is the last in the quorum to
1486          * start OOM.  Initiate the selection and signaling of the
1487          * victim.
1488          */
1489         vm_pageout_oom(VM_OOM_MEM);
1490
1491         /*
1492          * After one round of OOM terror, recall our vote.  On the
1493          * next pass, current pagedaemon would vote again if the low
1494          * memory condition is still there, due to vmd_oom being
1495          * false.
1496          */
1497         vmd->vmd_oom = FALSE;
1498         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1499 }
1500
1501 void
1502 vm_pageout_oom(int shortage)
1503 {
1504         struct proc *p, *bigproc;
1505         vm_offset_t size, bigsize;
1506         struct thread *td;
1507         struct vmspace *vm;
1508
1509         /*
1510          * We keep the process bigproc locked once we find it to keep anyone
1511          * from messing with it; however, there is a possibility of
1512          * deadlock if process B is bigproc and one of it's child processes
1513          * attempts to propagate a signal to B while we are waiting for A's
1514          * lock while walking this list.  To avoid this, we don't block on
1515          * the process lock but just skip a process if it is already locked.
1516          */
1517         bigproc = NULL;
1518         bigsize = 0;
1519         sx_slock(&allproc_lock);
1520         FOREACH_PROC_IN_SYSTEM(p) {
1521                 int breakout;
1522
1523                 PROC_LOCK(p);
1524
1525                 /*
1526                  * If this is a system, protected or killed process, skip it.
1527                  */
1528                 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1529                     P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1530                     p->p_pid == 1 || P_KILLED(p) ||
1531                     (p->p_pid < 48 && swap_pager_avail != 0)) {
1532                         PROC_UNLOCK(p);
1533                         continue;
1534                 }
1535                 /*
1536                  * If the process is in a non-running type state,
1537                  * don't touch it.  Check all the threads individually.
1538                  */
1539                 breakout = 0;
1540                 FOREACH_THREAD_IN_PROC(p, td) {
1541                         thread_lock(td);
1542                         if (!TD_ON_RUNQ(td) &&
1543                             !TD_IS_RUNNING(td) &&
1544                             !TD_IS_SLEEPING(td) &&
1545                             !TD_IS_SUSPENDED(td)) {
1546                                 thread_unlock(td);
1547                                 breakout = 1;
1548                                 break;
1549                         }
1550                         thread_unlock(td);
1551                 }
1552                 if (breakout) {
1553                         PROC_UNLOCK(p);
1554                         continue;
1555                 }
1556                 /*
1557                  * get the process size
1558                  */
1559                 vm = vmspace_acquire_ref(p);
1560                 if (vm == NULL) {
1561                         PROC_UNLOCK(p);
1562                         continue;
1563                 }
1564                 _PHOLD(p);
1565                 if (!vm_map_trylock_read(&vm->vm_map)) {
1566                         _PRELE(p);
1567                         PROC_UNLOCK(p);
1568                         vmspace_free(vm);
1569                         continue;
1570                 }
1571                 PROC_UNLOCK(p);
1572                 size = vmspace_swap_count(vm);
1573                 vm_map_unlock_read(&vm->vm_map);
1574                 if (shortage == VM_OOM_MEM)
1575                         size += vmspace_resident_count(vm);
1576                 vmspace_free(vm);
1577                 /*
1578                  * if the this process is bigger than the biggest one
1579                  * remember it.
1580                  */
1581                 if (size > bigsize) {
1582                         if (bigproc != NULL)
1583                                 PRELE(bigproc);
1584                         bigproc = p;
1585                         bigsize = size;
1586                 } else {
1587                         PRELE(p);
1588                 }
1589         }
1590         sx_sunlock(&allproc_lock);
1591         if (bigproc != NULL) {
1592                 if (vm_panic_on_oom != 0)
1593                         panic("out of swap space");
1594                 PROC_LOCK(bigproc);
1595                 killproc(bigproc, "out of swap space");
1596                 sched_nice(bigproc, PRIO_MIN);
1597                 _PRELE(bigproc);
1598                 PROC_UNLOCK(bigproc);
1599                 wakeup(&vm_cnt.v_free_count);
1600         }
1601 }
1602
1603 static void
1604 vm_pageout_worker(void *arg)
1605 {
1606         struct vm_domain *domain;
1607         int domidx;
1608
1609         domidx = (uintptr_t)arg;
1610         domain = &vm_dom[domidx];
1611
1612         /*
1613          * XXXKIB It could be useful to bind pageout daemon threads to
1614          * the cores belonging to the domain, from which vm_page_array
1615          * is allocated.
1616          */
1617
1618         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
1619         domain->vmd_last_active_scan = ticks;
1620         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
1621
1622         /*
1623          * The pageout daemon worker is never done, so loop forever.
1624          */
1625         while (TRUE) {
1626                 /*
1627                  * If we have enough free memory, wakeup waiters.  Do
1628                  * not clear vm_pages_needed until we reach our target,
1629                  * otherwise we may be woken up over and over again and
1630                  * waste a lot of cpu.
1631                  */
1632                 mtx_lock(&vm_page_queue_free_mtx);
1633                 if (vm_pages_needed && !vm_page_count_min()) {
1634                         if (!vm_paging_needed())
1635                                 vm_pages_needed = 0;
1636                         wakeup(&vm_cnt.v_free_count);
1637                 }
1638                 if (vm_pages_needed) {
1639                         /*
1640                          * We're still not done.  Either vm_pages_needed was
1641                          * set by another thread during the previous scan
1642                          * (typically, this happens during a level 0 scan) or
1643                          * vm_pages_needed was already set and the scan failed
1644                          * to free enough pages.  If we haven't yet performed
1645                          * a level >= 2 scan (unlimited dirty cleaning), then
1646                          * upgrade the level and scan again now.  Otherwise,
1647                          * sleep a bit and try again later.  While sleeping,
1648                          * vm_pages_needed can be cleared.
1649                          */
1650                         if (domain->vmd_pass > 1)
1651                                 msleep(&vm_pages_needed,
1652                                     &vm_page_queue_free_mtx, PVM, "psleep",
1653                                     hz / 2);
1654                 } else {
1655                         /*
1656                          * Good enough, sleep until required to refresh
1657                          * stats.
1658                          */
1659                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
1660                             PVM, "psleep", hz);
1661                 }
1662                 if (vm_pages_needed) {
1663                         vm_cnt.v_pdwakeups++;
1664                         domain->vmd_pass++;
1665                 } else
1666                         domain->vmd_pass = 0;
1667                 mtx_unlock(&vm_page_queue_free_mtx);
1668                 vm_pageout_scan(domain, domain->vmd_pass);
1669         }
1670 }
1671
1672 /*
1673  *      vm_pageout_init initialises basic pageout daemon settings.
1674  */
1675 static void
1676 vm_pageout_init(void)
1677 {
1678         /*
1679          * Initialize some paging parameters.
1680          */
1681         vm_cnt.v_interrupt_free_min = 2;
1682         if (vm_cnt.v_page_count < 2000)
1683                 vm_pageout_page_count = 8;
1684
1685         /*
1686          * v_free_reserved needs to include enough for the largest
1687          * swap pager structures plus enough for any pv_entry structs
1688          * when paging.
1689          */
1690         if (vm_cnt.v_page_count > 1024)
1691                 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
1692         else
1693                 vm_cnt.v_free_min = 4;
1694         vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1695             vm_cnt.v_interrupt_free_min;
1696         vm_cnt.v_free_reserved = vm_pageout_page_count +
1697             vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
1698         vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
1699         vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
1700         vm_cnt.v_free_min += vm_cnt.v_free_reserved;
1701         vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
1702         vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
1703         if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
1704                 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
1705
1706         /*
1707          * Set the default wakeup threshold to be 10% above the minimum
1708          * page limit.  This keeps the steady state out of shortfall.
1709          */
1710         vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
1711
1712         /*
1713          * Set interval in seconds for active scan.  We want to visit each
1714          * page at least once every ten minutes.  This is to prevent worst
1715          * case paging behaviors with stale active LRU.
1716          */
1717         if (vm_pageout_update_period == 0)
1718                 vm_pageout_update_period = 600;
1719
1720         /* XXX does not really belong here */
1721         if (vm_page_max_wired == 0)
1722                 vm_page_max_wired = vm_cnt.v_free_count / 3;
1723 }
1724
1725 /*
1726  *     vm_pageout is the high level pageout daemon.
1727  */
1728 static void
1729 vm_pageout(void)
1730 {
1731         int error;
1732 #if MAXMEMDOM > 1
1733         int i;
1734 #endif
1735
1736         swap_pager_swap_init();
1737 #if MAXMEMDOM > 1
1738         for (i = 1; i < vm_ndomains; i++) {
1739                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
1740                     curproc, NULL, 0, 0, "dom%d", i);
1741                 if (error != 0) {
1742                         panic("starting pageout for domain %d, error %d\n",
1743                             i, error);
1744                 }
1745         }
1746 #endif
1747         error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
1748             0, 0, "uma");
1749         if (error != 0)
1750                 panic("starting uma_reclaim helper, error %d\n", error);
1751         vm_pageout_worker((void *)(uintptr_t)0);
1752 }
1753
1754 /*
1755  * Unless the free page queue lock is held by the caller, this function
1756  * should be regarded as advisory.  Specifically, the caller should
1757  * not msleep() on &vm_cnt.v_free_count following this function unless
1758  * the free page queue lock is held until the msleep() is performed.
1759  */
1760 void
1761 pagedaemon_wakeup(void)
1762 {
1763
1764         if (!vm_pages_needed && curthread->td_proc != pageproc) {
1765                 vm_pages_needed = 1;
1766                 wakeup(&vm_pages_needed);
1767         }
1768 }
1769
1770 #if !defined(NO_SWAPPING)
1771 static void
1772 vm_req_vmdaemon(int req)
1773 {
1774         static int lastrun = 0;
1775
1776         mtx_lock(&vm_daemon_mtx);
1777         vm_pageout_req_swapout |= req;
1778         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1779                 wakeup(&vm_daemon_needed);
1780                 lastrun = ticks;
1781         }
1782         mtx_unlock(&vm_daemon_mtx);
1783 }
1784
1785 static void
1786 vm_daemon(void)
1787 {
1788         struct rlimit rsslim;
1789         struct proc *p;
1790         struct thread *td;
1791         struct vmspace *vm;
1792         int breakout, swapout_flags, tryagain, attempts;
1793 #ifdef RACCT
1794         uint64_t rsize, ravailable;
1795 #endif
1796
1797         while (TRUE) {
1798                 mtx_lock(&vm_daemon_mtx);
1799                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
1800 #ifdef RACCT
1801                     racct_enable ? hz : 0
1802 #else
1803                     0
1804 #endif
1805                 );
1806                 swapout_flags = vm_pageout_req_swapout;
1807                 vm_pageout_req_swapout = 0;
1808                 mtx_unlock(&vm_daemon_mtx);
1809                 if (swapout_flags)
1810                         swapout_procs(swapout_flags);
1811
1812                 /*
1813                  * scan the processes for exceeding their rlimits or if
1814                  * process is swapped out -- deactivate pages
1815                  */
1816                 tryagain = 0;
1817                 attempts = 0;
1818 again:
1819                 attempts++;
1820                 sx_slock(&allproc_lock);
1821                 FOREACH_PROC_IN_SYSTEM(p) {
1822                         vm_pindex_t limit, size;
1823
1824                         /*
1825                          * if this is a system process or if we have already
1826                          * looked at this process, skip it.
1827                          */
1828                         PROC_LOCK(p);
1829                         if (p->p_state != PRS_NORMAL ||
1830                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1831                                 PROC_UNLOCK(p);
1832                                 continue;
1833                         }
1834                         /*
1835                          * if the process is in a non-running type state,
1836                          * don't touch it.
1837                          */
1838                         breakout = 0;
1839                         FOREACH_THREAD_IN_PROC(p, td) {
1840                                 thread_lock(td);
1841                                 if (!TD_ON_RUNQ(td) &&
1842                                     !TD_IS_RUNNING(td) &&
1843                                     !TD_IS_SLEEPING(td) &&
1844                                     !TD_IS_SUSPENDED(td)) {
1845                                         thread_unlock(td);
1846                                         breakout = 1;
1847                                         break;
1848                                 }
1849                                 thread_unlock(td);
1850                         }
1851                         if (breakout) {
1852                                 PROC_UNLOCK(p);
1853                                 continue;
1854                         }
1855                         /*
1856                          * get a limit
1857                          */
1858                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
1859                         limit = OFF_TO_IDX(
1860                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
1861
1862                         /*
1863                          * let processes that are swapped out really be
1864                          * swapped out set the limit to nothing (will force a
1865                          * swap-out.)
1866                          */
1867                         if ((p->p_flag & P_INMEM) == 0)
1868                                 limit = 0;      /* XXX */
1869                         vm = vmspace_acquire_ref(p);
1870                         PROC_UNLOCK(p);
1871                         if (vm == NULL)
1872                                 continue;
1873
1874                         size = vmspace_resident_count(vm);
1875                         if (size >= limit) {
1876                                 vm_pageout_map_deactivate_pages(
1877                                     &vm->vm_map, limit);
1878                         }
1879 #ifdef RACCT
1880                         if (racct_enable) {
1881                                 rsize = IDX_TO_OFF(size);
1882                                 PROC_LOCK(p);
1883                                 racct_set(p, RACCT_RSS, rsize);
1884                                 ravailable = racct_get_available(p, RACCT_RSS);
1885                                 PROC_UNLOCK(p);
1886                                 if (rsize > ravailable) {
1887                                         /*
1888                                          * Don't be overly aggressive; this
1889                                          * might be an innocent process,
1890                                          * and the limit could've been exceeded
1891                                          * by some memory hog.  Don't try
1892                                          * to deactivate more than 1/4th
1893                                          * of process' resident set size.
1894                                          */
1895                                         if (attempts <= 8) {
1896                                                 if (ravailable < rsize -
1897                                                     (rsize / 4)) {
1898                                                         ravailable = rsize -
1899                                                             (rsize / 4);
1900                                                 }
1901                                         }
1902                                         vm_pageout_map_deactivate_pages(
1903                                             &vm->vm_map,
1904                                             OFF_TO_IDX(ravailable));
1905                                         /* Update RSS usage after paging out. */
1906                                         size = vmspace_resident_count(vm);
1907                                         rsize = IDX_TO_OFF(size);
1908                                         PROC_LOCK(p);
1909                                         racct_set(p, RACCT_RSS, rsize);
1910                                         PROC_UNLOCK(p);
1911                                         if (rsize > ravailable)
1912                                                 tryagain = 1;
1913                                 }
1914                         }
1915 #endif
1916                         vmspace_free(vm);
1917                 }
1918                 sx_sunlock(&allproc_lock);
1919                 if (tryagain != 0 && attempts <= 10)
1920                         goto again;
1921         }
1922 }
1923 #endif                  /* !defined(NO_SWAPPING) */