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