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 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
 184         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
 185         "free page threshold for waking up the pageout daemon");
 186
 187 SYSCTL_INT(_vm, OID_AUTO, max_launder,
 188         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
 189
 190 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
 191         CTLFLAG_RW, &vm_pageout_update_period, 0,
 192         "Maximum active LRU update period");
 193
 194 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
 195         "Low memory callback period");
 196
 197 #if defined(NO_SWAPPING)
 198 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 199         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
 200 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 201         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 202 #else
 203 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 204         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
 205 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 206         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 207 #endif
 208
 209 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
 210         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
 211
 212 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
 213         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
 214
 215 static int pageout_lock_miss;
 216 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 217         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 218
 219 #define VM_PAGEOUT_PAGE_COUNT 16
 220 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
 221
 222 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
 223 SYSCTL_INT(_vm, OID_AUTO, max_wired,
 224         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
 225
 226 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
 227 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
 228     vm_paddr_t);
 229 #if !defined(NO_SWAPPING)
 230 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
 231 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
 232 static void vm_req_vmdaemon(int req);
 233 #endif
 234 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 235
 236 /*
 237  * Initialize a dummy page for marking the caller's place in the specified
 238  * paging queue.  In principle, this function only needs to set the flag
 239  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
 240  * to one as safety precautions.
 241  */
 242 static void
 243 vm_pageout_init_marker(vm_page_t marker, u_short queue)
 244 {
 245
 246         bzero(marker, sizeof(*marker));
 247         marker->flags = PG_MARKER;
 248         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
 249         marker->queue = queue;
 250         marker->hold_count = 1;
 251 }
 252
 253 /*
 254  * vm_pageout_fallback_object_lock:
 255  *
 256  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
 257  * known to have failed and page queue must be either PQ_ACTIVE or
 258  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
 259  * while locking the vm object.  Use marker page to detect page queue
 260  * changes and maintain notion of next page on page queue.  Return
 261  * TRUE if no changes were detected, FALSE otherwise.  vm object is
 262  * locked on return.
 263  *
 264  * This function depends on both the lock portion of struct vm_object
 265  * and normal struct vm_page being type stable.
 266  */
 267 static boolean_t
 268 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
 269 {
 270         struct vm_page marker;
 271         struct vm_pagequeue *pq;
 272         boolean_t unchanged;
 273         u_short queue;
 274         vm_object_t object;
 275
 276         queue = m->queue;
 277         vm_pageout_init_marker(&marker, queue);
 278         pq = vm_page_pagequeue(m);
 279         object = m->object;
 280
 281         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 282         vm_pagequeue_unlock(pq);
 283         vm_page_unlock(m);
 284         VM_OBJECT_WLOCK(object);
 285         vm_page_lock(m);
 286         vm_pagequeue_lock(pq);
 287
 288         /* Page queue might have changed. */
 289         *next = TAILQ_NEXT(&marker, plinks.q);
 290         unchanged = (m->queue == queue &&
 291                      m->object == object &&
 292                      &marker == TAILQ_NEXT(m, plinks.q));
 293         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 294         return (unchanged);
 295 }
 296
 297 /*
 298  * Lock the page while holding the page queue lock.  Use marker page
 299  * to detect page queue changes and maintain notion of next page on
 300  * page queue.  Return TRUE if no changes were detected, FALSE
 301  * otherwise.  The page is locked on return. The page queue lock might
 302  * be dropped and reacquired.
 303  *
 304  * This function depends on normal struct vm_page being type stable.
 305  */
 306 static boolean_t
 307 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
 308 {
 309         struct vm_page marker;
 310         struct vm_pagequeue *pq;
 311         boolean_t unchanged;
 312         u_short queue;
 313
 314         vm_page_lock_assert(m, MA_NOTOWNED);
 315         if (vm_page_trylock(m))
 316                 return (TRUE);
 317
 318         queue = m->queue;
 319         vm_pageout_init_marker(&marker, queue);
 320         pq = vm_page_pagequeue(m);
 321
 322         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 323         vm_pagequeue_unlock(pq);
 324         vm_page_lock(m);
 325         vm_pagequeue_lock(pq);
 326
 327         /* Page queue might have changed. */
 328         *next = TAILQ_NEXT(&marker, plinks.q);
 329         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
 330         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 331         return (unchanged);
 332 }
 333
 334 /*
 335  * vm_pageout_clean:
 336  *
 337  * Clean the page and remove it from the laundry.
 338  *
 339  * We set the busy bit to cause potential page faults on this page to
 340  * block.  Note the careful timing, however, the busy bit isn't set till
 341  * late and we cannot do anything that will mess with the page.
 342  */
 343 static int
 344 vm_pageout_clean(vm_page_t m)
 345 {
 346         vm_object_t object;
 347         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
 348         int pageout_count;
 349         int ib, is, page_base;
 350         vm_pindex_t pindex = m->pindex;
 351
 352         vm_page_lock_assert(m, MA_OWNED);
 353         object = m->object;
 354         VM_OBJECT_ASSERT_WLOCKED(object);
 355
 356         /*
 357          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
 358          * with the new swapper, but we could have serious problems paging
 359          * out other object types if there is insufficient memory.
 360          *
 361          * Unfortunately, checking free memory here is far too late, so the
 362          * check has been moved up a procedural level.
 363          */
 364
 365         /*
 366          * Can't clean the page if it's busy or held.
 367          */
 368         vm_page_assert_unbusied(m);
 369         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
 370         vm_page_unlock(m);
 371
 372         mc[vm_pageout_page_count] = pb = ps = m;
 373         pageout_count = 1;
 374         page_base = vm_pageout_page_count;
 375         ib = 1;
 376         is = 1;
 377
 378         /*
 379          * Scan object for clusterable pages.
 380          *
 381          * We can cluster ONLY if: ->> the page is NOT
 382          * clean, wired, busy, held, or mapped into a
 383          * buffer, and one of the following:
 384          * 1) The page is inactive, or a seldom used
 385          *    active page.
 386          * -or-
 387          * 2) we force the issue.
 388          *
 389          * During heavy mmap/modification loads the pageout
 390          * daemon can really fragment the underlying file
 391          * due to flushing pages out of order and not trying
 392          * align the clusters (which leave sporatic out-of-order
 393          * holes).  To solve this problem we do the reverse scan
 394          * first and attempt to align our cluster, then do a
 395          * forward scan if room remains.
 396          */
 397 more:
 398         while (ib && pageout_count < vm_pageout_page_count) {
 399                 vm_page_t p;
 400
 401                 if (ib > pindex) {
 402                         ib = 0;
 403                         break;
 404                 }
 405
 406                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
 407                         ib = 0;
 408                         break;
 409                 }
 410                 vm_page_lock(p);
 411                 vm_page_test_dirty(p);
 412                 if (p->dirty == 0 ||
 413                     p->queue != PQ_INACTIVE ||
 414                     p->hold_count != 0) {       /* may be undergoing I/O */
 415                         vm_page_unlock(p);
 416                         ib = 0;
 417                         break;
 418                 }
 419                 vm_page_unlock(p);
 420                 mc[--page_base] = pb = p;
 421                 ++pageout_count;
 422                 ++ib;
 423                 /*
 424                  * alignment boundry, stop here and switch directions.  Do
 425                  * not clear ib.
 426                  */
 427                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 428                         break;
 429         }
 430
 431         while (pageout_count < vm_pageout_page_count &&
 432             pindex + is < object->size) {
 433                 vm_page_t p;
 434
 435                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
 436                         break;
 437                 vm_page_lock(p);
 438                 vm_page_test_dirty(p);
 439                 if (p->dirty == 0 ||
 440                     p->queue != PQ_INACTIVE ||
 441                     p->hold_count != 0) {       /* may be undergoing I/O */
 442                         vm_page_unlock(p);
 443                         break;
 444                 }
 445                 vm_page_unlock(p);
 446                 mc[page_base + pageout_count] = ps = p;
 447                 ++pageout_count;
 448                 ++is;
 449         }
 450
 451         /*
 452          * If we exhausted our forward scan, continue with the reverse scan
 453          * when possible, even past a page boundry.  This catches boundry
 454          * conditions.
 455          */
 456         if (ib && pageout_count < vm_pageout_page_count)
 457                 goto more;
 458
 459         /*
 460          * we allow reads during pageouts...
 461          */
 462         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
 463             NULL));
 464 }
 465
 466 /*
 467  * vm_pageout_flush() - launder the given pages
 468  *
 469  *      The given pages are laundered.  Note that we setup for the start of
 470  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
 471  *      reference count all in here rather then in the parent.  If we want
 472  *      the parent to do more sophisticated things we may have to change
 473  *      the ordering.
 474  *
 475  *      Returned runlen is the count of pages between mreq and first
 476  *      page after mreq with status VM_PAGER_AGAIN.
 477  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
 478  *      for any page in runlen set.
 479  */
 480 int
 481 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
 482     boolean_t *eio)
 483 {
 484         vm_object_t object = mc[0]->object;
 485         int pageout_status[count];
 486         int numpagedout = 0;
 487         int i, runlen;
 488
 489         VM_OBJECT_ASSERT_WLOCKED(object);
 490
 491         /*
 492          * Initiate I/O.  Bump the vm_page_t->busy counter and
 493          * mark the pages read-only.
 494          *
 495          * We do not have to fixup the clean/dirty bits here... we can
 496          * allow the pager to do it after the I/O completes.
 497          *
 498          * NOTE! mc[i]->dirty may be partial or fragmented due to an
 499          * edge case with file fragments.
 500          */
 501         for (i = 0; i < count; i++) {
 502                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
 503                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
 504                         mc[i], i, count));
 505                 vm_page_sbusy(mc[i]);
 506                 pmap_remove_write(mc[i]);
 507         }
 508         vm_object_pip_add(object, count);
 509
 510         vm_pager_put_pages(object, mc, count, flags, pageout_status);
 511
 512         runlen = count - mreq;
 513         if (eio != NULL)
 514                 *eio = FALSE;
 515         for (i = 0; i < count; i++) {
 516                 vm_page_t mt = mc[i];
 517
 518                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
 519                     !pmap_page_is_write_mapped(mt),
 520                     ("vm_pageout_flush: page %p is not write protected", mt));
 521                 switch (pageout_status[i]) {
 522                 case VM_PAGER_OK:
 523                 case VM_PAGER_PEND:
 524                         numpagedout++;
 525                         break;
 526                 case VM_PAGER_BAD:
 527                         /*
 528                          * Page outside of range of object. Right now we
 529                          * essentially lose the changes by pretending it
 530                          * worked.
 531                          */
 532                         vm_page_undirty(mt);
 533                         break;
 534                 case VM_PAGER_ERROR:
 535                 case VM_PAGER_FAIL:
 536                         /*
 537                          * If page couldn't be paged out, then reactivate the
 538                          * page so it doesn't clog the inactive list.  (We
 539                          * will try paging out it again later).
 540                          */
 541                         vm_page_lock(mt);
 542                         vm_page_activate(mt);
 543                         vm_page_unlock(mt);
 544                         if (eio != NULL && i >= mreq && i - mreq < runlen)
 545                                 *eio = TRUE;
 546                         break;
 547                 case VM_PAGER_AGAIN:
 548                         if (i >= mreq && i - mreq < runlen)
 549                                 runlen = i - mreq;
 550                         break;
 551                 }
 552
 553                 /*
 554                  * If the operation is still going, leave the page busy to
 555                  * block all other accesses. Also, leave the paging in
 556                  * progress indicator set so that we don't attempt an object
 557                  * collapse.
 558                  */
 559                 if (pageout_status[i] != VM_PAGER_PEND) {
 560                         vm_object_pip_wakeup(object);
 561                         vm_page_sunbusy(mt);
 562                         if (vm_page_count_severe()) {
 563                                 vm_page_lock(mt);
 564                                 vm_page_try_to_cache(mt);
 565                                 vm_page_unlock(mt);
 566                         }
 567                 }
 568         }
 569         if (prunlen != NULL)
 570                 *prunlen = runlen;
 571         return (numpagedout);
 572 }
 573
 574 static boolean_t
 575 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
 576     vm_paddr_t high)
 577 {
 578         struct mount *mp;
 579         struct vnode *vp;
 580         vm_object_t object;
 581         vm_paddr_t pa;
 582         vm_page_t m, m_tmp, next;
 583         int lockmode;
 584
 585         vm_pagequeue_lock(pq);
 586         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
 587                 if ((m->flags & PG_MARKER) != 0)
 588                         continue;
 589                 pa = VM_PAGE_TO_PHYS(m);
 590                 if (pa < low || pa + PAGE_SIZE > high)
 591                         continue;
 592                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
 593                         vm_page_unlock(m);
 594                         continue;
 595                 }
 596                 object = m->object;
 597                 if ((!VM_OBJECT_TRYWLOCK(object) &&
 598                     (!vm_pageout_fallback_object_lock(m, &next) ||
 599                     m->hold_count != 0)) || vm_page_busied(m)) {
 600                         vm_page_unlock(m);
 601                         VM_OBJECT_WUNLOCK(object);
 602                         continue;
 603                 }
 604                 vm_page_test_dirty(m);
 605                 if (m->dirty == 0 && object->ref_count != 0)
 606                         pmap_remove_all(m);
 607                 if (m->dirty != 0) {
 608                         vm_page_unlock(m);
 609                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
 610                                 VM_OBJECT_WUNLOCK(object);
 611                                 continue;
 612                         }
 613                         if (object->type == OBJT_VNODE) {
 614                                 vm_pagequeue_unlock(pq);
 615                                 vp = object->handle;
 616                                 vm_object_reference_locked(object);
 617                                 VM_OBJECT_WUNLOCK(object);
 618                                 (void)vn_start_write(vp, &mp, V_WAIT);
 619                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 620                                     LK_SHARED : LK_EXCLUSIVE;
 621                                 vn_lock(vp, lockmode | LK_RETRY);
 622                                 VM_OBJECT_WLOCK(object);
 623                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
 624                                 VM_OBJECT_WUNLOCK(object);
 625                                 VOP_UNLOCK(vp, 0);
 626                                 vm_object_deallocate(object);
 627                                 vn_finished_write(mp);
 628                                 return (TRUE);
 629                         } else if (object->type == OBJT_SWAP ||
 630                             object->type == OBJT_DEFAULT) {
 631                                 vm_pagequeue_unlock(pq);
 632                                 m_tmp = m;
 633                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
 634                                     0, NULL, NULL);
 635                                 VM_OBJECT_WUNLOCK(object);
 636                                 return (TRUE);
 637                         }
 638                 } else {
 639                         /*
 640                          * Dequeue here to prevent lock recursion in
 641                          * vm_page_cache().
 642                          */
 643                         vm_page_dequeue_locked(m);
 644                         vm_page_cache(m);
 645                         vm_page_unlock(m);
 646                 }
 647                 VM_OBJECT_WUNLOCK(object);
 648         }
 649         vm_pagequeue_unlock(pq);
 650         return (FALSE);
 651 }
 652
 653 /*
 654  * Increase the number of cached pages.  The specified value, "tries",
 655  * determines which categories of pages are cached:
 656  *
 657  *  0: All clean, inactive pages within the specified physical address range
 658  *     are cached.  Will not sleep.
 659  *  1: The vm_lowmem handlers are called.  All inactive pages within
 660  *     the specified physical address range are cached.  May sleep.
 661  *  2: The vm_lowmem handlers are called.  All inactive and active pages
 662  *     within the specified physical address range are cached.  May sleep.
 663  */
 664 void
 665 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
 666 {
 667         int actl, actmax, inactl, inactmax, dom, initial_dom;
 668         static int start_dom = 0;
 669
 670         if (tries > 0) {
 671                 /*
 672                  * Decrease registered cache sizes.  The vm_lowmem handlers
 673                  * may acquire locks and/or sleep, so they can only be invoked
 674                  * when "tries" is greater than zero.
 675                  */
 676                 SDT_PROBE0(vm, , , vm__lowmem_cache);
 677                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 678
 679                 /*
 680                  * We do this explicitly after the caches have been drained
 681                  * above.
 682                  */
 683                 uma_reclaim();
 684         }
 685
 686         /*
 687          * Make the next scan start on the next domain.
 688          */
 689         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
 690
 691         inactl = 0;
 692         inactmax = cnt.v_inactive_count;
 693         actl = 0;
 694         actmax = tries < 2 ? 0 : cnt.v_active_count;
 695         dom = initial_dom;
 696
 697         /*
 698          * Scan domains in round-robin order, first inactive queues,
 699          * then active.  Since domain usually owns large physically
 700          * contiguous chunk of memory, it makes sense to completely
 701          * exhaust one domain before switching to next, while growing
 702          * the pool of contiguous physical pages.
 703          *
 704          * Do not even start launder a domain which cannot contain
 705          * the specified address range, as indicated by segments
 706          * constituting the domain.
 707          */
 708 again:
 709         if (inactl < inactmax) {
 710                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 711                     low, high) &&
 712                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
 713                     tries, low, high)) {
 714                         inactl++;
 715                         goto again;
 716                 }
 717                 if (++dom == vm_ndomains)
 718                         dom = 0;
 719                 if (dom != initial_dom)
 720                         goto again;
 721         }
 722         if (actl < actmax) {
 723                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 724                     low, high) &&
 725                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
 726                       tries, low, high)) {
 727                         actl++;
 728                         goto again;
 729                 }
 730                 if (++dom == vm_ndomains)
 731                         dom = 0;
 732                 if (dom != initial_dom)
 733                         goto again;
 734         }
 735 }
 736
 737 #if !defined(NO_SWAPPING)
 738 /*
 739  *      vm_pageout_object_deactivate_pages
 740  *
 741  *      Deactivate enough pages to satisfy the inactive target
 742  *      requirements.
 743  *
 744  *      The object and map must be locked.
 745  */
 746 static void
 747 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 748     long desired)
 749 {
 750         vm_object_t backing_object, object;
 751         vm_page_t p;
 752         int act_delta, remove_mode;
 753
 754         VM_OBJECT_ASSERT_LOCKED(first_object);
 755         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 756                 return;
 757         for (object = first_object;; object = backing_object) {
 758                 if (pmap_resident_count(pmap) <= desired)
 759                         goto unlock_return;
 760                 VM_OBJECT_ASSERT_LOCKED(object);
 761                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 762                     object->paging_in_progress != 0)
 763                         goto unlock_return;
 764
 765                 remove_mode = 0;
 766                 if (object->shadow_count > 1)
 767                         remove_mode = 1;
 768                 /*
 769                  * Scan the object's entire memory queue.
 770                  */
 771                 TAILQ_FOREACH(p, &object->memq, listq) {
 772                         if (pmap_resident_count(pmap) <= desired)
 773                                 goto unlock_return;
 774                         if (vm_page_busied(p))
 775                                 continue;
 776                         PCPU_INC(cnt.v_pdpages);
 777                         vm_page_lock(p);
 778                         if (p->wire_count != 0 || p->hold_count != 0 ||
 779                             !pmap_page_exists_quick(pmap, p)) {
 780                                 vm_page_unlock(p);
 781                                 continue;
 782                         }
 783                         act_delta = pmap_ts_referenced(p);
 784                         if ((p->aflags & PGA_REFERENCED) != 0) {
 785                                 if (act_delta == 0)
 786                                         act_delta = 1;
 787                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 788                         }
 789                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
 790                                 vm_page_activate(p);
 791                                 p->act_count += act_delta;
 792                         } else if (p->queue == PQ_ACTIVE) {
 793                                 if (act_delta == 0) {
 794                                         p->act_count -= min(p->act_count,
 795                                             ACT_DECLINE);
 796                                         if (!remove_mode && p->act_count == 0) {
 797                                                 pmap_remove_all(p);
 798                                                 vm_page_deactivate(p);
 799                                         } else
 800                                                 vm_page_requeue(p);
 801                                 } else {
 802                                         vm_page_activate(p);
 803                                         if (p->act_count < ACT_MAX -
 804                                             ACT_ADVANCE)
 805                                                 p->act_count += ACT_ADVANCE;
 806                                         vm_page_requeue(p);
 807                                 }
 808                         } else if (p->queue == PQ_INACTIVE)
 809                                 pmap_remove_all(p);
 810                         vm_page_unlock(p);
 811                 }
 812                 if ((backing_object = object->backing_object) == NULL)
 813                         goto unlock_return;
 814                 VM_OBJECT_RLOCK(backing_object);
 815                 if (object != first_object)
 816                         VM_OBJECT_RUNLOCK(object);
 817         }
 818 unlock_return:
 819         if (object != first_object)
 820                 VM_OBJECT_RUNLOCK(object);
 821 }
 822
 823 /*
 824  * deactivate some number of pages in a map, try to do it fairly, but
 825  * that is really hard to do.
 826  */
 827 static void
 828 vm_pageout_map_deactivate_pages(map, desired)
 829         vm_map_t map;
 830         long desired;
 831 {
 832         vm_map_entry_t tmpe;
 833         vm_object_t obj, bigobj;
 834         int nothingwired;
 835
 836         if (!vm_map_trylock(map))
 837                 return;
 838
 839         bigobj = NULL;
 840         nothingwired = TRUE;
 841
 842         /*
 843          * first, search out the biggest object, and try to free pages from
 844          * that.
 845          */
 846         tmpe = map->header.next;
 847         while (tmpe != &map->header) {
 848                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 849                         obj = tmpe->object.vm_object;
 850                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 851                                 if (obj->shadow_count <= 1 &&
 852                                     (bigobj == NULL ||
 853                                      bigobj->resident_page_count < obj->resident_page_count)) {
 854                                         if (bigobj != NULL)
 855                                                 VM_OBJECT_RUNLOCK(bigobj);
 856                                         bigobj = obj;
 857                                 } else
 858                                         VM_OBJECT_RUNLOCK(obj);
 859                         }
 860                 }
 861                 if (tmpe->wired_count > 0)
 862                         nothingwired = FALSE;
 863                 tmpe = tmpe->next;
 864         }
 865
 866         if (bigobj != NULL) {
 867                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
 868                 VM_OBJECT_RUNLOCK(bigobj);
 869         }
 870         /*
 871          * Next, hunt around for other pages to deactivate.  We actually
 872          * do this search sort of wrong -- .text first is not the best idea.
 873          */
 874         tmpe = map->header.next;
 875         while (tmpe != &map->header) {
 876                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 877                         break;
 878                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 879                         obj = tmpe->object.vm_object;
 880                         if (obj != NULL) {
 881                                 VM_OBJECT_RLOCK(obj);
 882                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
 883                                 VM_OBJECT_RUNLOCK(obj);
 884                         }
 885                 }
 886                 tmpe = tmpe->next;
 887         }
 888
 889 #ifdef __ia64__
 890         /*
 891          * Remove all non-wired, managed mappings if a process is swapped out.
 892          * This will free page table pages.
 893          */
 894         if (desired == 0)
 895                 pmap_remove_pages(map->pmap);
 896 #else
 897         /*
 898          * Remove all mappings if a process is swapped out, this will free page
 899          * table pages.
 900          */
 901         if (desired == 0 && nothingwired) {
 902                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 903                     vm_map_max(map));
 904         }
 905 #endif
 906
 907         vm_map_unlock(map);
 908 }
 909 #endif          /* !defined(NO_SWAPPING) */
 910
 911 /*
 912  *      vm_pageout_scan does the dirty work for the pageout daemon.
 913  *
 914  *      pass 0 - Update active LRU/deactivate pages
 915  *      pass 1 - Move inactive to cache or free
 916  *      pass 2 - Launder dirty pages
 917  */
 918 static void
 919 vm_pageout_scan(struct vm_domain *vmd, int pass)
 920 {
 921         vm_page_t m, next;
 922         struct vm_pagequeue *pq;
 923         vm_object_t object;
 924         int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
 925         int vnodes_skipped = 0;
 926         int maxlaunder;
 927         int lockmode;
 928         boolean_t queues_locked;
 929
 930         /*
 931          * If we need to reclaim memory ask kernel caches to return
 932          * some.  We rate limit to avoid thrashing.
 933          */
 934         if (vmd == &vm_dom[0] && pass > 0 &&
 935             (ticks - lowmem_ticks) / hz >= lowmem_period) {
 936                 /*
 937                  * Decrease registered cache sizes.
 938                  */
 939                 SDT_PROBE0(vm, , , vm__lowmem_scan);
 940                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 941                 /*
 942                  * We do this explicitly after the caches have been
 943                  * drained above.
 944                  */
 945                 uma_reclaim();
 946                 lowmem_ticks = ticks;
 947         }
 948
 949         /*
 950          * The addl_page_shortage is the number of temporarily
 951          * stuck pages in the inactive queue.  In other words, the
 952          * number of pages from the inactive count that should be
 953          * discounted in setting the target for the active queue scan.
 954          */
 955         addl_page_shortage = 0;
 956
 957         /*
 958          * Calculate the number of pages we want to either free or move
 959          * to the cache.
 960          */
 961         if (pass > 0) {
 962                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
 963                 page_shortage = vm_paging_target() + deficit;
 964         } else
 965                 page_shortage = deficit = 0;
 966
 967         /*
 968          * maxlaunder limits the number of dirty pages we flush per scan.
 969          * For most systems a smaller value (16 or 32) is more robust under
 970          * extreme memory and disk pressure because any unnecessary writes
 971          * to disk can result in extreme performance degredation.  However,
 972          * systems with excessive dirty pages (especially when MAP_NOSYNC is
 973          * used) will die horribly with limited laundering.  If the pageout
 974          * daemon cannot clean enough pages in the first pass, we let it go
 975          * all out in succeeding passes.
 976          */
 977         if ((maxlaunder = vm_max_launder) <= 1)
 978                 maxlaunder = 1;
 979         if (pass > 1)
 980                 maxlaunder = 10000;
 981
 982         /*
 983          * Start scanning the inactive queue for pages we can move to the
 984          * cache or free.  The scan will stop when the target is reached or
 985          * we have scanned the entire inactive queue.  Note that m->act_count
 986          * is not used to form decisions for the inactive queue, only for the
 987          * active queue.
 988          */
 989         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
 990         maxscan = pq->pq_cnt;
 991         vm_pagequeue_lock(pq);
 992         queues_locked = TRUE;
 993         for (m = TAILQ_FIRST(&pq->pq_pl);
 994              m != NULL && maxscan-- > 0 && page_shortage > 0;
 995              m = next) {
 996                 vm_pagequeue_assert_locked(pq);
 997                 KASSERT(queues_locked, ("unlocked queues"));
 998                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
 999
1000                 PCPU_INC(cnt.v_pdpages);
1001                 next = TAILQ_NEXT(m, plinks.q);
1002
1003                 /*
1004                  * skip marker pages
1005                  */
1006                 if (m->flags & PG_MARKER)
1007                         continue;
1008
1009                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1010                     ("Fictitious page %p cannot be in inactive queue", m));
1011                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1012                     ("Unmanaged page %p cannot be in inactive queue", m));
1013
1014                 /*
1015                  * The page or object lock acquisitions fail if the
1016                  * page was removed from the queue or moved to a
1017                  * different position within the queue.  In either
1018                  * case, addl_page_shortage should not be incremented.
1019                  */
1020                 if (!vm_pageout_page_lock(m, &next)) {
1021                         vm_page_unlock(m);
1022                         continue;
1023                 }
1024                 object = m->object;
1025                 if (!VM_OBJECT_TRYWLOCK(object) &&
1026                     !vm_pageout_fallback_object_lock(m, &next)) {
1027                         vm_page_unlock(m);
1028                         VM_OBJECT_WUNLOCK(object);
1029                         continue;
1030                 }
1031
1032                 /*
1033                  * Don't mess with busy pages, keep them at at the
1034                  * front of the queue, most likely they are being
1035                  * paged out.  Increment addl_page_shortage for busy
1036                  * pages, because they may leave the inactive queue
1037                  * shortly after page scan is finished.
1038                  */
1039                 if (vm_page_busied(m)) {
1040                         vm_page_unlock(m);
1041                         VM_OBJECT_WUNLOCK(object);
1042                         addl_page_shortage++;
1043                         continue;
1044                 }
1045
1046                 /*
1047                  * We unlock the inactive page queue, invalidating the
1048                  * 'next' pointer.  Use our marker to remember our
1049                  * place.
1050                  */
1051                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
1052                 vm_pagequeue_unlock(pq);
1053                 queues_locked = FALSE;
1054
1055                 /*
1056                  * We bump the activation count if the page has been
1057                  * referenced while in the inactive queue.  This makes
1058                  * it less likely that the page will be added back to the
1059                  * inactive queue prematurely again.  Here we check the
1060                  * page tables (or emulated bits, if any), given the upper
1061                  * level VM system not knowing anything about existing
1062                  * references.
1063                  */
1064                 act_delta = 0;
1065                 if ((m->aflags & PGA_REFERENCED) != 0) {
1066                         vm_page_aflag_clear(m, PGA_REFERENCED);
1067                         act_delta = 1;
1068                 }
1069                 if (object->ref_count != 0) {
1070                         act_delta += pmap_ts_referenced(m);
1071                 } else {
1072                         KASSERT(!pmap_page_is_mapped(m),
1073                             ("vm_pageout_scan: page %p is mapped", m));
1074                 }
1075
1076                 /*
1077                  * If the upper level VM system knows about any page
1078                  * references, we reactivate the page or requeue it.
1079                  */
1080                 if (act_delta != 0) {
1081                         if (object->ref_count) {
1082                                 vm_page_activate(m);
1083                                 m->act_count += act_delta + ACT_ADVANCE;
1084                         } else {
1085                                 vm_pagequeue_lock(pq);
1086                                 queues_locked = TRUE;
1087                                 vm_page_requeue_locked(m);
1088                         }
1089                         VM_OBJECT_WUNLOCK(object);
1090                         vm_page_unlock(m);
1091                         goto relock_queues;
1092                 }
1093
1094                 if (m->hold_count != 0) {
1095                         vm_page_unlock(m);
1096                         VM_OBJECT_WUNLOCK(object);
1097
1098                         /*
1099                          * Held pages are essentially stuck in the
1100                          * queue.  So, they ought to be discounted
1101                          * from the inactive count.  See the
1102                          * calculation of the page_shortage for the
1103                          * loop over the active queue below.
1104                          */
1105                         addl_page_shortage++;
1106                         goto relock_queues;
1107                 }
1108
1109                 /*
1110                  * If the page appears to be clean at the machine-independent
1111                  * layer, then remove all of its mappings from the pmap in
1112                  * anticipation of placing it onto the cache queue.  If,
1113                  * however, any of the page's mappings allow write access,
1114                  * then the page may still be modified until the last of those
1115                  * mappings are removed.
1116                  */
1117                 vm_page_test_dirty(m);
1118                 if (m->dirty == 0 && object->ref_count != 0)
1119                         pmap_remove_all(m);
1120
1121                 if (m->valid == 0) {
1122                         /*
1123                          * Invalid pages can be easily freed
1124                          */
1125                         vm_page_free(m);
1126                         PCPU_INC(cnt.v_dfree);
1127                         --page_shortage;
1128                 } else if (m->dirty == 0) {
1129                         /*
1130                          * Clean pages can be placed onto the cache queue.
1131                          * This effectively frees them.
1132                          */
1133                         vm_page_cache(m);
1134                         --page_shortage;
1135                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
1136                         /*
1137                          * Dirty pages need to be paged out, but flushing
1138                          * a page is extremely expensive verses freeing
1139                          * a clean page.  Rather then artificially limiting
1140                          * the number of pages we can flush, we instead give
1141                          * dirty pages extra priority on the inactive queue
1142                          * by forcing them to be cycled through the queue
1143                          * twice before being flushed, after which the
1144                          * (now clean) page will cycle through once more
1145                          * before being freed.  This significantly extends
1146                          * the thrash point for a heavily loaded machine.
1147                          */
1148                         m->flags |= PG_WINATCFLS;
1149                         vm_pagequeue_lock(pq);
1150                         queues_locked = TRUE;
1151                         vm_page_requeue_locked(m);
1152                 } else if (maxlaunder > 0) {
1153                         /*
1154                          * We always want to try to flush some dirty pages if
1155                          * we encounter them, to keep the system stable.
1156                          * Normally this number is small, but under extreme
1157                          * pressure where there are insufficient clean pages
1158                          * on the inactive queue, we may have to go all out.
1159                          */
1160                         int swap_pageouts_ok;
1161                         struct vnode *vp = NULL;
1162                         struct mount *mp = NULL;
1163
1164                         if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
1165                                 swap_pageouts_ok = 1;
1166                         } else {
1167                                 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
1168                                 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
1169                                 vm_page_count_min());
1170
1171                         }
1172
1173                         /*
1174                          * We don't bother paging objects that are "dead".
1175                          * Those objects are in a "rundown" state.
1176                          */
1177                         if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
1178                                 vm_pagequeue_lock(pq);
1179                                 vm_page_unlock(m);
1180                                 VM_OBJECT_WUNLOCK(object);
1181                                 queues_locked = TRUE;
1182                                 vm_page_requeue_locked(m);
1183                                 goto relock_queues;
1184                         }
1185
1186                         /*
1187                          * The object is already known NOT to be dead.   It
1188                          * is possible for the vget() to block the whole
1189                          * pageout daemon, but the new low-memory handling
1190                          * code should prevent it.
1191                          *
1192                          * The previous code skipped locked vnodes and, worse,
1193                          * reordered pages in the queue.  This results in
1194                          * completely non-deterministic operation and, on a
1195                          * busy system, can lead to extremely non-optimal
1196                          * pageouts.  For example, it can cause clean pages
1197                          * to be freed and dirty pages to be moved to the end
1198                          * of the queue.  Since dirty pages are also moved to
1199                          * the end of the queue once-cleaned, this gives
1200                          * way too large a weighting to defering the freeing
1201                          * of dirty pages.
1202                          *
1203                          * We can't wait forever for the vnode lock, we might
1204                          * deadlock due to a vn_read() getting stuck in
1205                          * vm_wait while holding this vnode.  We skip the
1206                          * vnode if we can't get it in a reasonable amount
1207                          * of time.
1208                          */
1209                         if (object->type == OBJT_VNODE) {
1210                                 vm_page_unlock(m);
1211                                 vp = object->handle;
1212                                 if (vp->v_type == VREG &&
1213                                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
1214                                         mp = NULL;
1215                                         ++pageout_lock_miss;
1216                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1217                                                 vnodes_skipped++;
1218                                         goto unlock_and_continue;
1219                                 }
1220                                 KASSERT(mp != NULL,
1221                                     ("vp %p with NULL v_mount", vp));
1222                                 vm_object_reference_locked(object);
1223                                 VM_OBJECT_WUNLOCK(object);
1224                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
1225                                     LK_SHARED : LK_EXCLUSIVE;
1226                                 if (vget(vp, lockmode | LK_TIMELOCK,
1227                                     curthread)) {
1228                                         VM_OBJECT_WLOCK(object);
1229                                         ++pageout_lock_miss;
1230                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1231                                                 vnodes_skipped++;
1232                                         vp = NULL;
1233                                         goto unlock_and_continue;
1234                                 }
1235                                 VM_OBJECT_WLOCK(object);
1236                                 vm_page_lock(m);
1237                                 vm_pagequeue_lock(pq);
1238                                 queues_locked = TRUE;
1239                                 /*
1240                                  * The page might have been moved to another
1241                                  * queue during potential blocking in vget()
1242                                  * above.  The page might have been freed and
1243                                  * reused for another vnode.
1244                                  */
1245                                 if (m->queue != PQ_INACTIVE ||
1246                                     m->object != object ||
1247                                     TAILQ_NEXT(m, plinks.q) != &vmd->vmd_marker) {
1248                                         vm_page_unlock(m);
1249                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1250                                                 vnodes_skipped++;
1251                                         goto unlock_and_continue;
1252                                 }
1253
1254                                 /*
1255                                  * The page may have been busied during the
1256                                  * blocking in vget().  We don't move the
1257                                  * page back onto the end of the queue so that
1258                                  * statistics are more correct if we don't.
1259                                  */
1260                                 if (vm_page_busied(m)) {
1261                                         vm_page_unlock(m);
1262                                         addl_page_shortage++;
1263                                         goto unlock_and_continue;
1264                                 }
1265
1266                                 /*
1267                                  * If the page has become held it might
1268                                  * be undergoing I/O, so skip it
1269                                  */
1270                                 if (m->hold_count != 0) {
1271                                         vm_page_unlock(m);
1272                                         addl_page_shortage++;
1273                                         if (object->flags & OBJ_MIGHTBEDIRTY)
1274                                                 vnodes_skipped++;
1275                                         goto unlock_and_continue;
1276                                 }
1277                                 vm_pagequeue_unlock(pq);
1278                                 queues_locked = FALSE;
1279                         }
1280
1281                         /*
1282                          * If a page is dirty, then it is either being washed
1283                          * (but not yet cleaned) or it is still in the
1284                          * laundry.  If it is still in the laundry, then we
1285                          * start the cleaning operation.
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 (vm_pageout_clean(m) != 0) {
1292                                 --page_shortage;
1293                                 --maxlaunder;
1294                         }
1295 unlock_and_continue:
1296                         vm_page_lock_assert(m, MA_NOTOWNED);
1297                         VM_OBJECT_WUNLOCK(object);
1298                         if (mp != NULL) {
1299                                 if (queues_locked) {
1300                                         vm_pagequeue_unlock(pq);
1301                                         queues_locked = FALSE;
1302                                 }
1303                                 if (vp != NULL)
1304                                         vput(vp);
1305                                 vm_object_deallocate(object);
1306                                 vn_finished_write(mp);
1307                         }
1308                         vm_page_lock_assert(m, MA_NOTOWNED);
1309                         goto relock_queues;
1310                 }
1311                 vm_page_unlock(m);
1312                 VM_OBJECT_WUNLOCK(object);
1313 relock_queues:
1314                 if (!queues_locked) {
1315                         vm_pagequeue_lock(pq);
1316                         queues_locked = TRUE;
1317                 }
1318                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
1319                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
1320         }
1321         vm_pagequeue_unlock(pq);
1322
1323 #if !defined(NO_SWAPPING)
1324         /*
1325          * Wakeup the swapout daemon if we didn't cache or free the targeted
1326          * number of pages.
1327          */
1328         if (vm_swap_enabled && page_shortage > 0)
1329                 vm_req_vmdaemon(VM_SWAP_NORMAL);
1330 #endif
1331
1332         /*
1333          * Wakeup the sync daemon if we skipped a vnode in a writeable object
1334          * and we didn't cache or free enough pages.
1335          */
1336         if (vnodes_skipped > 0 && page_shortage > cnt.v_free_target -
1337             cnt.v_free_min)
1338                 (void)speedup_syncer();
1339
1340         /*
1341          * Compute the number of pages we want to try to move from the
1342          * active queue to the inactive queue.
1343          */
1344         page_shortage = cnt.v_inactive_target - cnt.v_inactive_count +
1345             vm_paging_target() + deficit + addl_page_shortage;
1346
1347         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1348         vm_pagequeue_lock(pq);
1349         maxscan = pq->pq_cnt;
1350
1351         /*
1352          * If we're just idle polling attempt to visit every
1353          * active page within 'update_period' seconds.
1354          */
1355         if (pass == 0 && vm_pageout_update_period != 0) {
1356                 maxscan /= vm_pageout_update_period;
1357                 page_shortage = maxscan;
1358         }
1359
1360         /*
1361          * Scan the active queue for things we can deactivate. We nominally
1362          * track the per-page activity counter and use it to locate
1363          * deactivation candidates.
1364          */
1365         m = TAILQ_FIRST(&pq->pq_pl);
1366         while (m != NULL && maxscan-- > 0 && page_shortage > 0) {
1367
1368                 KASSERT(m->queue == PQ_ACTIVE,
1369                     ("vm_pageout_scan: page %p isn't active", m));
1370
1371                 next = TAILQ_NEXT(m, plinks.q);
1372                 if ((m->flags & PG_MARKER) != 0) {
1373                         m = next;
1374                         continue;
1375                 }
1376                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1377                     ("Fictitious page %p cannot be in active queue", m));
1378                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1379                     ("Unmanaged page %p cannot be in active queue", m));
1380                 if (!vm_pageout_page_lock(m, &next)) {
1381                         vm_page_unlock(m);
1382                         m = next;
1383                         continue;
1384                 }
1385
1386                 /*
1387                  * The count for pagedaemon pages is done after checking the
1388                  * page for eligibility...
1389                  */
1390                 PCPU_INC(cnt.v_pdpages);
1391
1392                 /*
1393                  * Check to see "how much" the page has been used.
1394                  */
1395                 act_delta = 0;
1396                 if (m->aflags & PGA_REFERENCED) {
1397                         vm_page_aflag_clear(m, PGA_REFERENCED);
1398                         act_delta += 1;
1399                 }
1400                 /*
1401                  * Unlocked object ref count check.  Two races are possible.
1402                  * 1) The ref was transitioning to zero and we saw non-zero,
1403                  *    the pmap bits will be checked unnecessarily.
1404                  * 2) The ref was transitioning to one and we saw zero.
1405                  *    The page lock prevents a new reference to this page so
1406                  *    we need not check the reference bits.
1407                  */
1408                 if (m->object->ref_count != 0)
1409                         act_delta += pmap_ts_referenced(m);
1410
1411                 /*
1412                  * Advance or decay the act_count based on recent usage.
1413                  */
1414                 if (act_delta) {
1415                         m->act_count += ACT_ADVANCE + act_delta;
1416                         if (m->act_count > ACT_MAX)
1417                                 m->act_count = ACT_MAX;
1418                 } else {
1419                         m->act_count -= min(m->act_count, ACT_DECLINE);
1420                         act_delta = m->act_count;
1421                 }
1422
1423                 /*
1424                  * Move this page to the tail of the active or inactive
1425                  * queue depending on usage.
1426                  */
1427                 if (act_delta == 0) {
1428                         /* Dequeue to avoid later lock recursion. */
1429                         vm_page_dequeue_locked(m);
1430                         vm_page_deactivate(m);
1431                         page_shortage--;
1432                 } else
1433                         vm_page_requeue_locked(m);
1434                 vm_page_unlock(m);
1435                 m = next;
1436         }
1437         vm_pagequeue_unlock(pq);
1438 #if !defined(NO_SWAPPING)
1439         /*
1440          * Idle process swapout -- run once per second.
1441          */
1442         if (vm_swap_idle_enabled) {
1443                 static long lsec;
1444                 if (time_second != lsec) {
1445                         vm_req_vmdaemon(VM_SWAP_IDLE);
1446                         lsec = time_second;
1447                 }
1448         }
1449 #endif
1450
1451         /*
1452          * If we are critically low on one of RAM or swap and low on
1453          * the other, kill the largest process.  However, we avoid
1454          * doing this on the first pass in order to give ourselves a
1455          * chance to flush out dirty vnode-backed pages and to allow
1456          * active pages to be moved to the inactive queue and reclaimed.
1457          */
1458         vm_pageout_mightbe_oom(vmd, pass);
1459 }
1460
1461 static int vm_pageout_oom_vote;
1462
1463 /*
1464  * The pagedaemon threads randlomly select one to perform the
1465  * OOM.  Trying to kill processes before all pagedaemons
1466  * failed to reach free target is premature.
1467  */
1468 static void
1469 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
1470 {
1471         int old_vote;
1472
1473         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
1474             (swap_pager_full && vm_paging_target() > 0))) {
1475                 if (vmd->vmd_oom) {
1476                         vmd->vmd_oom = FALSE;
1477                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1478                 }
1479                 return;
1480         }
1481
1482         if (vmd->vmd_oom)
1483                 return;
1484
1485         vmd->vmd_oom = TRUE;
1486         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1487         if (old_vote != vm_ndomains - 1)
1488                 return;
1489
1490         /*
1491          * The current pagedaemon thread is the last in the quorum to
1492          * start OOM.  Initiate the selection and signaling of the
1493          * victim.
1494          */
1495         vm_pageout_oom(VM_OOM_MEM);
1496
1497         /*
1498          * After one round of OOM terror, recall our vote.  On the
1499          * next pass, current pagedaemon would vote again if the low
1500          * memory condition is still there, due to vmd_oom being
1501          * false.
1502          */
1503         vmd->vmd_oom = FALSE;
1504         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1505 }
1506
1507 void
1508 vm_pageout_oom(int shortage)
1509 {
1510         struct proc *p, *bigproc;
1511         vm_offset_t size, bigsize;
1512         struct thread *td;
1513         struct vmspace *vm;
1514
1515         /*
1516          * We keep the process bigproc locked once we find it to keep anyone
1517          * from messing with it; however, there is a possibility of
1518          * deadlock if process B is bigproc and one of it's child processes
1519          * attempts to propagate a signal to B while we are waiting for A's
1520          * lock while walking this list.  To avoid this, we don't block on
1521          * the process lock but just skip a process if it is already locked.
1522          */
1523         bigproc = NULL;
1524         bigsize = 0;
1525         sx_slock(&allproc_lock);
1526         FOREACH_PROC_IN_SYSTEM(p) {
1527                 int breakout;
1528
1529                 PROC_LOCK(p);
1530
1531                 /*
1532                  * If this is a system, protected or killed process, skip it.
1533                  */
1534                 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1535                     P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1536                     p->p_pid == 1 || P_KILLED(p) ||
1537                     (p->p_pid < 48 && swap_pager_avail != 0)) {
1538                         PROC_UNLOCK(p);
1539                         continue;
1540                 }
1541                 /*
1542                  * If the process is in a non-running type state,
1543                  * don't touch it.  Check all the threads individually.
1544                  */
1545                 breakout = 0;
1546                 FOREACH_THREAD_IN_PROC(p, td) {
1547                         thread_lock(td);
1548                         if (!TD_ON_RUNQ(td) &&
1549                             !TD_IS_RUNNING(td) &&
1550                             !TD_IS_SLEEPING(td) &&
1551                             !TD_IS_SUSPENDED(td)) {
1552                                 thread_unlock(td);
1553                                 breakout = 1;
1554                                 break;
1555                         }
1556                         thread_unlock(td);
1557                 }
1558                 if (breakout) {
1559                         PROC_UNLOCK(p);
1560                         continue;
1561                 }
1562                 /*
1563                  * get the process size
1564                  */
1565                 vm = vmspace_acquire_ref(p);
1566                 if (vm == NULL) {
1567                         PROC_UNLOCK(p);
1568                         continue;
1569                 }
1570                 _PHOLD(p);
1571                 if (!vm_map_trylock_read(&vm->vm_map)) {
1572                         _PRELE(p);
1573                         PROC_UNLOCK(p);
1574                         vmspace_free(vm);
1575                         continue;
1576                 }
1577                 PROC_UNLOCK(p);
1578                 size = vmspace_swap_count(vm);
1579                 vm_map_unlock_read(&vm->vm_map);
1580                 if (shortage == VM_OOM_MEM)
1581                         size += vmspace_resident_count(vm);
1582                 vmspace_free(vm);
1583                 /*
1584                  * if the this process is bigger than the biggest one
1585                  * remember it.
1586                  */
1587                 if (size > bigsize) {
1588                         if (bigproc != NULL)
1589                                 PRELE(bigproc);
1590                         bigproc = p;
1591                         bigsize = size;
1592                 } else {
1593                         PRELE(p);
1594                 }
1595         }
1596         sx_sunlock(&allproc_lock);
1597         if (bigproc != NULL) {
1598                 PROC_LOCK(bigproc);
1599                 killproc(bigproc, "out of swap space");
1600                 sched_nice(bigproc, PRIO_MIN);
1601                 _PRELE(bigproc);
1602                 PROC_UNLOCK(bigproc);
1603                 wakeup(&cnt.v_free_count);
1604         }
1605 }
1606
1607 static void
1608 vm_pageout_worker(void *arg)
1609 {
1610         struct vm_domain *domain;
1611         int domidx;
1612
1613         domidx = (uintptr_t)arg;
1614         domain = &vm_dom[domidx];
1615
1616         /*
1617          * XXXKIB It could be useful to bind pageout daemon threads to
1618          * the cores belonging to the domain, from which vm_page_array
1619          * is allocated.
1620          */
1621
1622         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
1623         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
1624
1625         /*
1626          * The pageout daemon worker is never done, so loop forever.
1627          */
1628         while (TRUE) {
1629                 /*
1630                  * If we have enough free memory, wakeup waiters.  Do
1631                  * not clear vm_pages_needed until we reach our target,
1632                  * otherwise we may be woken up over and over again and
1633                  * waste a lot of cpu.
1634                  */
1635                 mtx_lock(&vm_page_queue_free_mtx);
1636                 if (vm_pages_needed && !vm_page_count_min()) {
1637                         if (!vm_paging_needed())
1638                                 vm_pages_needed = 0;
1639                         wakeup(&cnt.v_free_count);
1640                 }
1641                 if (vm_pages_needed) {
1642                         /*
1643                          * Still not done, take a second pass without waiting
1644                          * (unlimited dirty cleaning), otherwise sleep a bit
1645                          * and try again.
1646                          */
1647                         if (domain->vmd_pass > 1)
1648                                 msleep(&vm_pages_needed,
1649                                     &vm_page_queue_free_mtx, PVM, "psleep",
1650                                     hz / 2);
1651                 } else {
1652                         /*
1653                          * Good enough, sleep until required to refresh
1654                          * stats.
1655                          */
1656                         domain->vmd_pass = 0;
1657                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
1658                             PVM, "psleep", hz);
1659
1660                 }
1661                 if (vm_pages_needed) {
1662                         cnt.v_pdwakeups++;
1663                         domain->vmd_pass++;
1664                 }
1665                 mtx_unlock(&vm_page_queue_free_mtx);
1666                 vm_pageout_scan(domain, domain->vmd_pass);
1667         }
1668 }
1669
1670 /*
1671  *      vm_pageout_init initialises basic pageout daemon settings.
1672  */
1673 static void
1674 vm_pageout_init(void)
1675 {
1676         /*
1677          * Initialize some paging parameters.
1678          */
1679         cnt.v_interrupt_free_min = 2;
1680         if (cnt.v_page_count < 2000)
1681                 vm_pageout_page_count = 8;
1682
1683         /*
1684          * v_free_reserved needs to include enough for the largest
1685          * swap pager structures plus enough for any pv_entry structs
1686          * when paging.
1687          */
1688         if (cnt.v_page_count > 1024)
1689                 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1690         else
1691                 cnt.v_free_min = 4;
1692         cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1693             cnt.v_interrupt_free_min;
1694         cnt.v_free_reserved = vm_pageout_page_count +
1695             cnt.v_pageout_free_min + (cnt.v_page_count / 768);
1696         cnt.v_free_severe = cnt.v_free_min / 2;
1697         cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1698         cnt.v_free_min += cnt.v_free_reserved;
1699         cnt.v_free_severe += cnt.v_free_reserved;
1700         cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1701         if (cnt.v_inactive_target > cnt.v_free_count / 3)
1702                 cnt.v_inactive_target = cnt.v_free_count / 3;
1703
1704         /*
1705          * Set the default wakeup threshold to be 10% above the minimum
1706          * page limit.  This keeps the steady state out of shortfall.
1707          */
1708         vm_pageout_wakeup_thresh = (cnt.v_free_min / 10) * 11;
1709
1710         /*
1711          * Set interval in seconds for active scan.  We want to visit each
1712          * page at least once every ten minutes.  This is to prevent worst
1713          * case paging behaviors with stale active LRU.
1714          */
1715         if (vm_pageout_update_period == 0)
1716                 vm_pageout_update_period = 600;
1717
1718         /* XXX does not really belong here */
1719         if (vm_page_max_wired == 0)
1720                 vm_page_max_wired = cnt.v_free_count / 3;
1721 }
1722
1723 /*
1724  *     vm_pageout is the high level pageout daemon.
1725  */
1726 static void
1727 vm_pageout(void)
1728 {
1729         int error;
1730 #if MAXMEMDOM > 1
1731         int i;
1732 #endif
1733
1734         swap_pager_swap_init();
1735 #if MAXMEMDOM > 1
1736         for (i = 1; i < vm_ndomains; i++) {
1737                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
1738                     curproc, NULL, 0, 0, "dom%d", i);
1739                 if (error != 0) {
1740                         panic("starting pageout for domain %d, error %d\n",
1741                             i, error);
1742                 }
1743         }
1744 #endif
1745         error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
1746             0, 0, "uma");
1747         if (error != 0)
1748                 panic("starting uma_reclaim helper, error %d\n", error);
1749         vm_pageout_worker((void *)(uintptr_t)0);
1750 }
1751
1752 /*
1753  * Unless the free page queue lock is held by the caller, this function
1754  * should be regarded as advisory.  Specifically, the caller should
1755  * not msleep() on &cnt.v_free_count following this function unless
1756  * the free page queue lock is held until the msleep() is performed.
1757  */
1758 void
1759 pagedaemon_wakeup(void)
1760 {
1761
1762         if (!vm_pages_needed && curthread->td_proc != pageproc) {
1763                 vm_pages_needed = 1;
1764                 wakeup(&vm_pages_needed);
1765         }
1766 }
1767
1768 #if !defined(NO_SWAPPING)
1769 static void
1770 vm_req_vmdaemon(int req)
1771 {
1772         static int lastrun = 0;
1773
1774         mtx_lock(&vm_daemon_mtx);
1775         vm_pageout_req_swapout |= req;
1776         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1777                 wakeup(&vm_daemon_needed);
1778                 lastrun = ticks;
1779         }
1780         mtx_unlock(&vm_daemon_mtx);
1781 }
1782
1783 static void
1784 vm_daemon(void)
1785 {
1786         struct rlimit rsslim;
1787         struct proc *p;
1788         struct thread *td;
1789         struct vmspace *vm;
1790         int breakout, swapout_flags, tryagain, attempts;
1791 #ifdef RACCT
1792         uint64_t rsize, ravailable;
1793 #endif
1794
1795         while (TRUE) {
1796                 mtx_lock(&vm_daemon_mtx);
1797                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
1798 #ifdef RACCT
1799                     racct_enable ? hz : 0
1800 #else
1801                     0
1802 #endif
1803                 );
1804                 swapout_flags = vm_pageout_req_swapout;
1805                 vm_pageout_req_swapout = 0;
1806                 mtx_unlock(&vm_daemon_mtx);
1807                 if (swapout_flags)
1808                         swapout_procs(swapout_flags);
1809
1810                 /*
1811                  * scan the processes for exceeding their rlimits or if
1812                  * process is swapped out -- deactivate pages
1813                  */
1814                 tryagain = 0;
1815                 attempts = 0;
1816 again:
1817                 attempts++;
1818                 sx_slock(&allproc_lock);
1819                 FOREACH_PROC_IN_SYSTEM(p) {
1820                         vm_pindex_t limit, size;
1821
1822                         /*
1823                          * if this is a system process or if we have already
1824                          * looked at this process, skip it.
1825                          */
1826                         PROC_LOCK(p);
1827                         if (p->p_state != PRS_NORMAL ||
1828                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1829                                 PROC_UNLOCK(p);
1830                                 continue;
1831                         }
1832                         /*
1833                          * if the process is in a non-running type state,
1834                          * don't touch it.
1835                          */
1836                         breakout = 0;
1837                         FOREACH_THREAD_IN_PROC(p, td) {
1838                                 thread_lock(td);
1839                                 if (!TD_ON_RUNQ(td) &&
1840                                     !TD_IS_RUNNING(td) &&
1841                                     !TD_IS_SLEEPING(td) &&
1842                                     !TD_IS_SUSPENDED(td)) {
1843                                         thread_unlock(td);
1844                                         breakout = 1;
1845                                         break;
1846                                 }
1847                                 thread_unlock(td);
1848                         }
1849                         if (breakout) {
1850                                 PROC_UNLOCK(p);
1851                                 continue;
1852                         }
1853                         /*
1854                          * get a limit
1855                          */
1856                         lim_rlimit(p, RLIMIT_RSS, &rsslim);
1857                         limit = OFF_TO_IDX(
1858                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
1859
1860                         /*
1861                          * let processes that are swapped out really be
1862                          * swapped out set the limit to nothing (will force a
1863                          * swap-out.)
1864                          */
1865                         if ((p->p_flag & P_INMEM) == 0)
1866                                 limit = 0;      /* XXX */
1867                         vm = vmspace_acquire_ref(p);
1868                         PROC_UNLOCK(p);
1869                         if (vm == NULL)
1870                                 continue;
1871
1872                         size = vmspace_resident_count(vm);
1873                         if (size >= limit) {
1874                                 vm_pageout_map_deactivate_pages(
1875                                     &vm->vm_map, limit);
1876                         }
1877 #ifdef RACCT
1878                         if (racct_enable) {
1879                                 rsize = IDX_TO_OFF(size);
1880                                 PROC_LOCK(p);
1881                                 racct_set(p, RACCT_RSS, rsize);
1882                                 ravailable = racct_get_available(p, RACCT_RSS);
1883                                 PROC_UNLOCK(p);
1884                                 if (rsize > ravailable) {
1885                                         /*
1886                                          * Don't be overly aggressive; this
1887                                          * might be an innocent process,
1888                                          * and the limit could've been exceeded
1889                                          * by some memory hog.  Don't try
1890                                          * to deactivate more than 1/4th
1891                                          * of process' resident set size.
1892                                          */
1893                                         if (attempts <= 8) {
1894                                                 if (ravailable < rsize -
1895                                                     (rsize / 4)) {
1896                                                         ravailable = rsize -
1897                                                             (rsize / 4);
1898                                                 }
1899                                         }
1900                                         vm_pageout_map_deactivate_pages(
1901                                             &vm->vm_map,
1902                                             OFF_TO_IDX(ravailable));
1903                                         /* Update RSS usage after paging out. */
1904                                         size = vmspace_resident_count(vm);
1905                                         rsize = IDX_TO_OFF(size);
1906                                         PROC_LOCK(p);
1907                                         racct_set(p, RACCT_RSS, rsize);
1908                                         PROC_UNLOCK(p);
1909                                         if (rsize > ravailable)
1910                                                 tryagain = 1;
1911                                 }
1912                         }
1913 #endif
1914                         vmspace_free(vm);
1915                 }
1916                 sx_sunlock(&allproc_lock);
1917                 if (tryagain != 0 && attempts <= 10)
1918                         goto again;
1919         }
1920 }
1921 #endif                  /* !defined(NO_SWAPPING) */