sys/vm/vm_pageout.c

   1 /*-
   2  * Copyright (c) 1991 Regents of the University of California.
   3  * All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  * Copyright (c) 2005 Yahoo! Technologies Norway AS
   9  * All rights reserved.
  10  *
  11  * This code is derived from software contributed to Berkeley by
  12  * The Mach Operating System project at Carnegie-Mellon University.
  13  *
  14  * Redistribution and use in source and binary forms, with or without
  15  * modification, are permitted provided that the following conditions
  16  * are met:
  17  * 1. Redistributions of source code must retain the above copyright
  18  *    notice, this list of conditions and the following disclaimer.
  19  * 2. Redistributions in binary form must reproduce the above copyright
  20  *    notice, this list of conditions and the following disclaimer in the
  21  *    documentation and/or other materials provided with the distribution.
  22  * 3. All advertising materials mentioning features or use of this software
  23  *    must display the following acknowledgement:
  24  *      This product includes software developed by the University of
  25  *      California, Berkeley and its contributors.
  26  * 4. Neither the name of the University nor the names of its contributors
  27  *    may be used to endorse or promote products derived from this software
  28  *    without specific prior written permission.
  29  *
  30  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  31  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  32  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  33  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  34  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  35  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  36  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  38  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  39  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  40  * SUCH DAMAGE.
  41  *
  42  *      from: @(#)vm_pageout.c  7.4 (Berkeley) 5/7/91
  43  *
  44  *
  45  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  46  * All rights reserved.
  47  *
  48  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  49  *
  50  * Permission to use, copy, modify and distribute this software and
  51  * its documentation is hereby granted, provided that both the copyright
  52  * notice and this permission notice appear in all copies of the
  53  * software, derivative works or modified versions, and any portions
  54  * thereof, and that both notices appear in supporting documentation.
  55  *
  56  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  57  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  58  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  59  *
  60  * Carnegie Mellon requests users of this software to return to
  61  *
  62  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  63  *  School of Computer Science
  64  *  Carnegie Mellon University
  65  *  Pittsburgh PA 15213-3890
  66  *
  67  * any improvements or extensions that they make and grant Carnegie the
  68  * rights to redistribute these changes.
  69  */
  70
  71 /*
  72  *      The proverbial page-out daemon.
  73  */
  74
  75 #include <sys/cdefs.h>
  76 __FBSDID("$FreeBSD$");
  77
  78 #include "opt_vm.h"
  79 #include "opt_kdtrace.h"
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/eventhandler.h>
  84 #include <sys/lock.h>
  85 #include <sys/mutex.h>
  86 #include <sys/proc.h>
  87 #include <sys/kthread.h>
  88 #include <sys/ktr.h>
  89 #include <sys/mount.h>
  90 #include <sys/racct.h>
  91 #include <sys/resourcevar.h>
  92 #include <sys/sched.h>
  93 #include <sys/sdt.h>
  94 #include <sys/signalvar.h>
  95 #include <sys/smp.h>
  96 #include <sys/time.h>
  97 #include <sys/vnode.h>
  98 #include <sys/vmmeter.h>
  99 #include <sys/rwlock.h>
 100 #include <sys/sx.h>
 101 #include <sys/sysctl.h>
 102
 103 #include <vm/vm.h>
 104 #include <vm/vm_param.h>
 105 #include <vm/vm_object.h>
 106 #include <vm/vm_page.h>
 107 #include <vm/vm_map.h>
 108 #include <vm/vm_pageout.h>
 109 #include <vm/vm_pager.h>
 110 #include <vm/vm_phys.h>
 111 #include <vm/swap_pager.h>
 112 #include <vm/vm_extern.h>
 113 #include <vm/uma.h>
 114
 115 /*
 116  * System initialization
 117  */
 118
 119 /* the kernel process "vm_pageout"*/
 120 static void vm_pageout(void);
 121 static void vm_pageout_init(void);
 122 static int vm_pageout_clean(vm_page_t m);
 123 static int vm_pageout_cluster(vm_page_t m);
 124 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
 125 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
 126
 127 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
 128     NULL);
 129
 130 struct proc *pageproc;
 131
 132 static struct kproc_desc page_kp = {
 133         "pagedaemon",
 134         vm_pageout,
 135         &pageproc
 136 };
 137 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
 138     &page_kp);
 139
 140 SDT_PROVIDER_DEFINE(vm);
 141 SDT_PROBE_DEFINE(vm, , , vm__lowmem_cache);
 142 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
 143
 144 #if !defined(NO_SWAPPING)
 145 /* the kernel process "vm_daemon"*/
 146 static void vm_daemon(void);
 147 static struct   proc *vmproc;
 148
 149 static struct kproc_desc vm_kp = {
 150         "vmdaemon",
 151         vm_daemon,
 152         &vmproc
 153 };
 154 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
 155 #endif
 156
 157
 158 int vm_pages_needed;            /* Event on which pageout daemon sleeps */
 159 int vm_pageout_deficit;         /* Estimated number of pages deficit */
 160 int vm_pageout_pages_needed;    /* flag saying that the pageout daemon needs pages */
 161 int vm_pageout_wakeup_thresh;
 162
 163 #if !defined(NO_SWAPPING)
 164 static int vm_pageout_req_swapout;      /* XXX */
 165 static int vm_daemon_needed;
 166 static struct mtx vm_daemon_mtx;
 167 /* Allow for use by vm_pageout before vm_daemon is initialized. */
 168 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 169 #endif
 170 static int vm_max_launder = 32;
 171 static int vm_pageout_update_period;
 172 static int defer_swap_pageouts;
 173 static int disable_swap_pageouts;
 174 static int lowmem_period = 10;
 175 static time_t lowmem_uptime;
 176
 177 #if defined(NO_SWAPPING)
 178 static int vm_swap_enabled = 0;
 179 static int vm_swap_idle_enabled = 0;
 180 #else
 181 static int vm_swap_enabled = 1;
 182 static int vm_swap_idle_enabled = 0;
 183 #endif
 184
 185 static int vm_panic_on_oom = 0;
 186
 187 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
 188         CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
 189         "panic on out of memory instead of killing the largest process");
 190
 191 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
 192         CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
 193         "free page threshold for waking up the pageout daemon");
 194
 195 SYSCTL_INT(_vm, OID_AUTO, max_launder,
 196         CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
 197
 198 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
 199         CTLFLAG_RW, &vm_pageout_update_period, 0,
 200         "Maximum active LRU update period");
 201
 202 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
 203         "Low memory callback period");
 204
 205 #if defined(NO_SWAPPING)
 206 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 207         CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
 208 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 209         CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 210 #else
 211 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
 212         CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
 213 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
 214         CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
 215 #endif
 216
 217 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
 218         CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
 219
 220 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
 221         CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
 222
 223 static int pageout_lock_miss;
 224 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 225         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 226
 227 #define VM_PAGEOUT_PAGE_COUNT 16
 228 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
 229
 230 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
 231 SYSCTL_INT(_vm, OID_AUTO, max_wired,
 232         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
 233
 234 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
 235 static boolean_t vm_pageout_launder(struct vm_pagequeue *pq, int, vm_paddr_t,
 236     vm_paddr_t);
 237 #if !defined(NO_SWAPPING)
 238 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
 239 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
 240 static void vm_req_vmdaemon(int req);
 241 #endif
 242 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 243
 244 /*
 245  * Initialize a dummy page for marking the caller's place in the specified
 246  * paging queue.  In principle, this function only needs to set the flag
 247  * PG_MARKER.  Nonetheless, it wirte busies and initializes the hold count
 248  * to one as safety precautions.
 249  */
 250 static void
 251 vm_pageout_init_marker(vm_page_t marker, u_short queue)
 252 {
 253
 254         bzero(marker, sizeof(*marker));
 255         marker->flags = PG_MARKER;
 256         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
 257         marker->queue = queue;
 258         marker->hold_count = 1;
 259 }
 260
 261 /*
 262  * vm_pageout_fallback_object_lock:
 263  *
 264  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
 265  * known to have failed and page queue must be either PQ_ACTIVE or
 266  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queues
 267  * while locking the vm object.  Use marker page to detect page queue
 268  * changes and maintain notion of next page on page queue.  Return
 269  * TRUE if no changes were detected, FALSE otherwise.  vm object is
 270  * locked on return.
 271  *
 272  * This function depends on both the lock portion of struct vm_object
 273  * and normal struct vm_page being type stable.
 274  */
 275 static boolean_t
 276 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
 277 {
 278         struct vm_page marker;
 279         struct vm_pagequeue *pq;
 280         boolean_t unchanged;
 281         u_short queue;
 282         vm_object_t object;
 283
 284         queue = m->queue;
 285         vm_pageout_init_marker(&marker, queue);
 286         pq = vm_page_pagequeue(m);
 287         object = m->object;
 288
 289         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 290         vm_pagequeue_unlock(pq);
 291         vm_page_unlock(m);
 292         VM_OBJECT_WLOCK(object);
 293         vm_page_lock(m);
 294         vm_pagequeue_lock(pq);
 295
 296         /* Page queue might have changed. */
 297         *next = TAILQ_NEXT(&marker, plinks.q);
 298         unchanged = (m->queue == queue &&
 299                      m->object == object &&
 300                      &marker == TAILQ_NEXT(m, plinks.q));
 301         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 302         return (unchanged);
 303 }
 304
 305 /*
 306  * Lock the page while holding the page queue lock.  Use marker page
 307  * to detect page queue changes and maintain notion of next page on
 308  * page queue.  Return TRUE if no changes were detected, FALSE
 309  * otherwise.  The page is locked on return. The page queue lock might
 310  * be dropped and reacquired.
 311  *
 312  * This function depends on normal struct vm_page being type stable.
 313  */
 314 static boolean_t
 315 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
 316 {
 317         struct vm_page marker;
 318         struct vm_pagequeue *pq;
 319         boolean_t unchanged;
 320         u_short queue;
 321
 322         vm_page_lock_assert(m, MA_NOTOWNED);
 323         if (vm_page_trylock(m))
 324                 return (TRUE);
 325
 326         queue = m->queue;
 327         vm_pageout_init_marker(&marker, queue);
 328         pq = vm_page_pagequeue(m);
 329
 330         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 331         vm_pagequeue_unlock(pq);
 332         vm_page_lock(m);
 333         vm_pagequeue_lock(pq);
 334
 335         /* Page queue might have changed. */
 336         *next = TAILQ_NEXT(&marker, plinks.q);
 337         unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, plinks.q));
 338         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 339         return (unchanged);
 340 }
 341
 342 /*
 343  * vm_pageout_clean:
 344  *
 345  * Clean the page and remove it from the laundry.
 346  *
 347  * We set the busy bit to cause potential page faults on this page to
 348  * block.  Note the careful timing, however, the busy bit isn't set till
 349  * late and we cannot do anything that will mess with the page.
 350  */
 351 static int
 352 vm_pageout_cluster(vm_page_t m)
 353 {
 354         vm_object_t object;
 355         vm_page_t mc[2*vm_pageout_page_count], pb, ps;
 356         int pageout_count;
 357         int ib, is, page_base;
 358         vm_pindex_t pindex = m->pindex;
 359
 360         vm_page_lock_assert(m, MA_OWNED);
 361         object = m->object;
 362         VM_OBJECT_ASSERT_WLOCKED(object);
 363
 364         /*
 365          * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
 366          * with the new swapper, but we could have serious problems paging
 367          * out other object types if there is insufficient memory.
 368          *
 369          * Unfortunately, checking free memory here is far too late, so the
 370          * check has been moved up a procedural level.
 371          */
 372
 373         /*
 374          * Can't clean the page if it's busy or held.
 375          */
 376         vm_page_assert_unbusied(m);
 377         KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
 378         vm_page_unlock(m);
 379
 380         mc[vm_pageout_page_count] = pb = ps = m;
 381         pageout_count = 1;
 382         page_base = vm_pageout_page_count;
 383         ib = 1;
 384         is = 1;
 385
 386         /*
 387          * Scan object for clusterable pages.
 388          *
 389          * We can cluster ONLY if: ->> the page is NOT
 390          * clean, wired, busy, held, or mapped into a
 391          * buffer, and one of the following:
 392          * 1) The page is inactive, or a seldom used
 393          *    active page.
 394          * -or-
 395          * 2) we force the issue.
 396          *
 397          * During heavy mmap/modification loads the pageout
 398          * daemon can really fragment the underlying file
 399          * due to flushing pages out of order and not trying
 400          * align the clusters (which leave sporatic out-of-order
 401          * holes).  To solve this problem we do the reverse scan
 402          * first and attempt to align our cluster, then do a
 403          * forward scan if room remains.
 404          */
 405 more:
 406         while (ib && pageout_count < vm_pageout_page_count) {
 407                 vm_page_t p;
 408
 409                 if (ib > pindex) {
 410                         ib = 0;
 411                         break;
 412                 }
 413
 414                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
 415                         ib = 0;
 416                         break;
 417                 }
 418                 vm_page_test_dirty(p);
 419                 if (p->dirty == 0) {
 420                         ib = 0;
 421                         break;
 422                 }
 423                 vm_page_lock(p);
 424                 if (p->queue != PQ_INACTIVE ||
 425                     p->hold_count != 0) {       /* may be undergoing I/O */
 426                         vm_page_unlock(p);
 427                         ib = 0;
 428                         break;
 429                 }
 430                 vm_page_unlock(p);
 431                 mc[--page_base] = pb = p;
 432                 ++pageout_count;
 433                 ++ib;
 434                 /*
 435                  * alignment boundry, stop here and switch directions.  Do
 436                  * not clear ib.
 437                  */
 438                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 439                         break;
 440         }
 441
 442         while (pageout_count < vm_pageout_page_count &&
 443             pindex + is < object->size) {
 444                 vm_page_t p;
 445
 446                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
 447                         break;
 448                 vm_page_test_dirty(p);
 449                 if (p->dirty == 0)
 450                         break;
 451                 vm_page_lock(p);
 452                 if (p->queue != PQ_INACTIVE ||
 453                     p->hold_count != 0) {       /* may be undergoing I/O */
 454                         vm_page_unlock(p);
 455                         break;
 456                 }
 457                 vm_page_unlock(p);
 458                 mc[page_base + pageout_count] = ps = p;
 459                 ++pageout_count;
 460                 ++is;
 461         }
 462
 463         /*
 464          * If we exhausted our forward scan, continue with the reverse scan
 465          * when possible, even past a page boundry.  This catches boundry
 466          * conditions.
 467          */
 468         if (ib && pageout_count < vm_pageout_page_count)
 469                 goto more;
 470
 471         /*
 472          * we allow reads during pageouts...
 473          */
 474         return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
 475             NULL));
 476 }
 477
 478 /*
 479  * vm_pageout_flush() - launder the given pages
 480  *
 481  *      The given pages are laundered.  Note that we setup for the start of
 482  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
 483  *      reference count all in here rather then in the parent.  If we want
 484  *      the parent to do more sophisticated things we may have to change
 485  *      the ordering.
 486  *
 487  *      Returned runlen is the count of pages between mreq and first
 488  *      page after mreq with status VM_PAGER_AGAIN.
 489  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
 490  *      for any page in runlen set.
 491  */
 492 int
 493 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
 494     boolean_t *eio)
 495 {
 496         vm_object_t object = mc[0]->object;
 497         int pageout_status[count];
 498         int numpagedout = 0;
 499         int i, runlen;
 500
 501         VM_OBJECT_ASSERT_WLOCKED(object);
 502
 503         /*
 504          * Initiate I/O.  Bump the vm_page_t->busy counter and
 505          * mark the pages read-only.
 506          *
 507          * We do not have to fixup the clean/dirty bits here... we can
 508          * allow the pager to do it after the I/O completes.
 509          *
 510          * NOTE! mc[i]->dirty may be partial or fragmented due to an
 511          * edge case with file fragments.
 512          */
 513         for (i = 0; i < count; i++) {
 514                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
 515                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
 516                         mc[i], i, count));
 517                 vm_page_sbusy(mc[i]);
 518                 pmap_remove_write(mc[i]);
 519         }
 520         vm_object_pip_add(object, count);
 521
 522         vm_pager_put_pages(object, mc, count, flags, pageout_status);
 523
 524         runlen = count - mreq;
 525         if (eio != NULL)
 526                 *eio = FALSE;
 527         for (i = 0; i < count; i++) {
 528                 vm_page_t mt = mc[i];
 529
 530                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
 531                     !pmap_page_is_write_mapped(mt),
 532                     ("vm_pageout_flush: page %p is not write protected", mt));
 533                 switch (pageout_status[i]) {
 534                 case VM_PAGER_OK:
 535                 case VM_PAGER_PEND:
 536                         numpagedout++;
 537                         break;
 538                 case VM_PAGER_BAD:
 539                         /*
 540                          * Page outside of range of object. Right now we
 541                          * essentially lose the changes by pretending it
 542                          * worked.
 543                          */
 544                         vm_page_undirty(mt);
 545                         break;
 546                 case VM_PAGER_ERROR:
 547                 case VM_PAGER_FAIL:
 548                         /*
 549                          * If page couldn't be paged out, then reactivate the
 550                          * page so it doesn't clog the inactive list.  (We
 551                          * will try paging out it again later).
 552                          */
 553                         vm_page_lock(mt);
 554                         vm_page_activate(mt);
 555                         vm_page_unlock(mt);
 556                         if (eio != NULL && i >= mreq && i - mreq < runlen)
 557                                 *eio = TRUE;
 558                         break;
 559                 case VM_PAGER_AGAIN:
 560                         if (i >= mreq && i - mreq < runlen)
 561                                 runlen = i - mreq;
 562                         break;
 563                 }
 564
 565                 /*
 566                  * If the operation is still going, leave the page busy to
 567                  * block all other accesses. Also, leave the paging in
 568                  * progress indicator set so that we don't attempt an object
 569                  * collapse.
 570                  */
 571                 if (pageout_status[i] != VM_PAGER_PEND) {
 572                         vm_object_pip_wakeup(object);
 573                         vm_page_sunbusy(mt);
 574                 }
 575         }
 576         if (prunlen != NULL)
 577                 *prunlen = runlen;
 578         return (numpagedout);
 579 }
 580
 581 static boolean_t
 582 vm_pageout_launder(struct vm_pagequeue *pq, int tries, vm_paddr_t low,
 583     vm_paddr_t high)
 584 {
 585         struct mount *mp;
 586         struct vnode *vp;
 587         vm_object_t object;
 588         vm_paddr_t pa;
 589         vm_page_t m, m_tmp, next;
 590         int lockmode;
 591
 592         vm_pagequeue_lock(pq);
 593         TAILQ_FOREACH_SAFE(m, &pq->pq_pl, plinks.q, next) {
 594                 if ((m->flags & PG_MARKER) != 0)
 595                         continue;
 596                 pa = VM_PAGE_TO_PHYS(m);
 597                 if (pa < low || pa + PAGE_SIZE > high)
 598                         continue;
 599                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
 600                         vm_page_unlock(m);
 601                         continue;
 602                 }
 603                 object = m->object;
 604                 if ((!VM_OBJECT_TRYWLOCK(object) &&
 605                     (!vm_pageout_fallback_object_lock(m, &next) ||
 606                     m->hold_count != 0)) || vm_page_busied(m)) {
 607                         vm_page_unlock(m);
 608                         VM_OBJECT_WUNLOCK(object);
 609                         continue;
 610                 }
 611                 vm_page_test_dirty(m);
 612                 if (m->dirty == 0 && object->ref_count != 0)
 613                         pmap_remove_all(m);
 614                 if (m->dirty != 0) {
 615                         vm_page_unlock(m);
 616                         if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
 617                                 VM_OBJECT_WUNLOCK(object);
 618                                 continue;
 619                         }
 620                         if (object->type == OBJT_VNODE) {
 621                                 vm_pagequeue_unlock(pq);
 622                                 vp = object->handle;
 623                                 vm_object_reference_locked(object);
 624                                 VM_OBJECT_WUNLOCK(object);
 625                                 (void)vn_start_write(vp, &mp, V_WAIT);
 626                                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 627                                     LK_SHARED : LK_EXCLUSIVE;
 628                                 vn_lock(vp, lockmode | LK_RETRY);
 629                                 VM_OBJECT_WLOCK(object);
 630                                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
 631                                 VM_OBJECT_WUNLOCK(object);
 632                                 VOP_UNLOCK(vp, 0);
 633                                 vm_object_deallocate(object);
 634                                 vn_finished_write(mp);
 635                                 return (TRUE);
 636                         } else if (object->type == OBJT_SWAP ||
 637                             object->type == OBJT_DEFAULT) {
 638                                 vm_pagequeue_unlock(pq);
 639                                 m_tmp = m;
 640                                 vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
 641                                     0, NULL, NULL);
 642                                 VM_OBJECT_WUNLOCK(object);
 643                                 return (TRUE);
 644                         }
 645                 } else {
 646                         /*
 647                          * Dequeue here to prevent lock recursion in
 648                          * vm_page_cache().
 649                          */
 650                         vm_page_dequeue_locked(m);
 651                         vm_page_cache(m);
 652                         vm_page_unlock(m);
 653                 }
 654                 VM_OBJECT_WUNLOCK(object);
 655         }
 656         vm_pagequeue_unlock(pq);
 657         return (FALSE);
 658 }
 659
 660 /*
 661  * Increase the number of cached pages.  The specified value, "tries",
 662  * determines which categories of pages are cached:
 663  *
 664  *  0: All clean, inactive pages within the specified physical address range
 665  *     are cached.  Will not sleep.
 666  *  1: The vm_lowmem handlers are called.  All inactive pages within
 667  *     the specified physical address range are cached.  May sleep.
 668  *  2: The vm_lowmem handlers are called.  All inactive and active pages
 669  *     within the specified physical address range are cached.  May sleep.
 670  */
 671 void
 672 vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
 673 {
 674         int actl, actmax, inactl, inactmax, dom, initial_dom;
 675         static int start_dom = 0;
 676
 677         if (tries > 0) {
 678                 /*
 679                  * Decrease registered cache sizes.  The vm_lowmem handlers
 680                  * may acquire locks and/or sleep, so they can only be invoked
 681                  * when "tries" is greater than zero.
 682                  */
 683                 SDT_PROBE0(vm, , , vm__lowmem_cache);
 684                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
 685
 686                 /*
 687                  * We do this explicitly after the caches have been drained
 688                  * above.
 689                  */
 690                 uma_reclaim();
 691         }
 692
 693         /*
 694          * Make the next scan start on the next domain.
 695          */
 696         initial_dom = atomic_fetchadd_int(&start_dom, 1) % vm_ndomains;
 697
 698         inactl = 0;
 699         inactmax = vm_cnt.v_inactive_count;
 700         actl = 0;
 701         actmax = tries < 2 ? 0 : vm_cnt.v_active_count;
 702         dom = initial_dom;
 703
 704         /*
 705          * Scan domains in round-robin order, first inactive queues,
 706          * then active.  Since domain usually owns large physically
 707          * contiguous chunk of memory, it makes sense to completely
 708          * exhaust one domain before switching to next, while growing
 709          * the pool of contiguous physical pages.
 710          *
 711          * Do not even start launder a domain which cannot contain
 712          * the specified address range, as indicated by segments
 713          * constituting the domain.
 714          */
 715 again:
 716         if (inactl < inactmax) {
 717                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 718                     low, high) &&
 719                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_INACTIVE],
 720                     tries, low, high)) {
 721                         inactl++;
 722                         goto again;
 723                 }
 724                 if (++dom == vm_ndomains)
 725                         dom = 0;
 726                 if (dom != initial_dom)
 727                         goto again;
 728         }
 729         if (actl < actmax) {
 730                 if (vm_phys_domain_intersects(vm_dom[dom].vmd_segs,
 731                     low, high) &&
 732                     vm_pageout_launder(&vm_dom[dom].vmd_pagequeues[PQ_ACTIVE],
 733                       tries, low, high)) {
 734                         actl++;
 735                         goto again;
 736                 }
 737                 if (++dom == vm_ndomains)
 738                         dom = 0;
 739                 if (dom != initial_dom)
 740                         goto again;
 741         }
 742 }
 743
 744 #if !defined(NO_SWAPPING)
 745 /*
 746  *      vm_pageout_object_deactivate_pages
 747  *
 748  *      Deactivate enough pages to satisfy the inactive target
 749  *      requirements.
 750  *
 751  *      The object and map must be locked.
 752  */
 753 static void
 754 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 755     long desired)
 756 {
 757         vm_object_t backing_object, object;
 758         vm_page_t p;
 759         int act_delta, remove_mode;
 760
 761         VM_OBJECT_ASSERT_LOCKED(first_object);
 762         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 763                 return;
 764         for (object = first_object;; object = backing_object) {
 765                 if (pmap_resident_count(pmap) <= desired)
 766                         goto unlock_return;
 767                 VM_OBJECT_ASSERT_LOCKED(object);
 768                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 769                     object->paging_in_progress != 0)
 770                         goto unlock_return;
 771
 772                 remove_mode = 0;
 773                 if (object->shadow_count > 1)
 774                         remove_mode = 1;
 775                 /*
 776                  * Scan the object's entire memory queue.
 777                  */
 778                 TAILQ_FOREACH(p, &object->memq, listq) {
 779                         if (pmap_resident_count(pmap) <= desired)
 780                                 goto unlock_return;
 781                         if (vm_page_busied(p))
 782                                 continue;
 783                         PCPU_INC(cnt.v_pdpages);
 784                         vm_page_lock(p);
 785                         if (p->wire_count != 0 || p->hold_count != 0 ||
 786                             !pmap_page_exists_quick(pmap, p)) {
 787                                 vm_page_unlock(p);
 788                                 continue;
 789                         }
 790                         act_delta = pmap_ts_referenced(p);
 791                         if ((p->aflags & PGA_REFERENCED) != 0) {
 792                                 if (act_delta == 0)
 793                                         act_delta = 1;
 794                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 795                         }
 796                         if (p->queue != PQ_ACTIVE && act_delta != 0) {
 797                                 vm_page_activate(p);
 798                                 p->act_count += act_delta;
 799                         } else if (p->queue == PQ_ACTIVE) {
 800                                 if (act_delta == 0) {
 801                                         p->act_count -= min(p->act_count,
 802                                             ACT_DECLINE);
 803                                         if (!remove_mode && p->act_count == 0) {
 804                                                 pmap_remove_all(p);
 805                                                 vm_page_deactivate(p);
 806                                         } else
 807                                                 vm_page_requeue(p);
 808                                 } else {
 809                                         vm_page_activate(p);
 810                                         if (p->act_count < ACT_MAX -
 811                                             ACT_ADVANCE)
 812                                                 p->act_count += ACT_ADVANCE;
 813                                         vm_page_requeue(p);
 814                                 }
 815                         } else if (p->queue == PQ_INACTIVE)
 816                                 pmap_remove_all(p);
 817                         vm_page_unlock(p);
 818                 }
 819                 if ((backing_object = object->backing_object) == NULL)
 820                         goto unlock_return;
 821                 VM_OBJECT_RLOCK(backing_object);
 822                 if (object != first_object)
 823                         VM_OBJECT_RUNLOCK(object);
 824         }
 825 unlock_return:
 826         if (object != first_object)
 827                 VM_OBJECT_RUNLOCK(object);
 828 }
 829
 830 /*
 831  * deactivate some number of pages in a map, try to do it fairly, but
 832  * that is really hard to do.
 833  */
 834 static void
 835 vm_pageout_map_deactivate_pages(map, desired)
 836         vm_map_t map;
 837         long desired;
 838 {
 839         vm_map_entry_t tmpe;
 840         vm_object_t obj, bigobj;
 841         int nothingwired;
 842
 843         if (!vm_map_trylock(map))
 844                 return;
 845
 846         bigobj = NULL;
 847         nothingwired = TRUE;
 848
 849         /*
 850          * first, search out the biggest object, and try to free pages from
 851          * that.
 852          */
 853         tmpe = map->header.next;
 854         while (tmpe != &map->header) {
 855                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 856                         obj = tmpe->object.vm_object;
 857                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 858                                 if (obj->shadow_count <= 1 &&
 859                                     (bigobj == NULL ||
 860                                      bigobj->resident_page_count < obj->resident_page_count)) {
 861                                         if (bigobj != NULL)
 862                                                 VM_OBJECT_RUNLOCK(bigobj);
 863                                         bigobj = obj;
 864                                 } else
 865                                         VM_OBJECT_RUNLOCK(obj);
 866                         }
 867                 }
 868                 if (tmpe->wired_count > 0)
 869                         nothingwired = FALSE;
 870                 tmpe = tmpe->next;
 871         }
 872
 873         if (bigobj != NULL) {
 874                 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
 875                 VM_OBJECT_RUNLOCK(bigobj);
 876         }
 877         /*
 878          * Next, hunt around for other pages to deactivate.  We actually
 879          * do this search sort of wrong -- .text first is not the best idea.
 880          */
 881         tmpe = map->header.next;
 882         while (tmpe != &map->header) {
 883                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 884                         break;
 885                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 886                         obj = tmpe->object.vm_object;
 887                         if (obj != NULL) {
 888                                 VM_OBJECT_RLOCK(obj);
 889                                 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
 890                                 VM_OBJECT_RUNLOCK(obj);
 891                         }
 892                 }
 893                 tmpe = tmpe->next;
 894         }
 895
 896         /*
 897          * Remove all mappings if a process is swapped out, this will free page
 898          * table pages.
 899          */
 900         if (desired == 0 && nothingwired) {
 901                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 902                     vm_map_max(map));
 903         }
 904
 905         vm_map_unlock(map);
 906 }
 907 #endif          /* !defined(NO_SWAPPING) */
 908
 909 /*
 910  * Attempt to acquire all of the necessary locks to launder a page and
 911  * then call through the clustering layer to PUTPAGES.  Wait a short
 912  * time for a vnode lock.
 913  *
 914  * Requires the page and object lock on entry, releases both before return.
 915  * Returns 0 on success and an errno otherwise.
 916  */
 917 static int
 918 vm_pageout_clean(vm_page_t m)
 919 {
 920         struct vnode *vp;
 921         struct mount *mp;
 922         vm_object_t object;
 923         vm_pindex_t pindex;
 924         int error, lockmode;
 925
 926         vm_page_assert_locked(m);
 927         object = m->object;
 928         VM_OBJECT_ASSERT_WLOCKED(object);
 929         error = 0;
 930         vp = NULL;
 931         mp = NULL;
 932
 933         /*
 934          * The object is already known NOT to be dead.   It
 935          * is possible for the vget() to block the whole
 936          * pageout daemon, but the new low-memory handling
 937          * code should prevent it.
 938          *
 939          * We can't wait forever for the vnode lock, we might
 940          * deadlock due to a vn_read() getting stuck in
 941          * vm_wait while holding this vnode.  We skip the
 942          * vnode if we can't get it in a reasonable amount
 943          * of time.
 944          */
 945         if (object->type == OBJT_VNODE) {
 946                 vm_page_unlock(m);
 947                 vp = object->handle;
 948                 if (vp->v_type == VREG &&
 949                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 950                         mp = NULL;
 951                         error = EDEADLK;
 952                         goto unlock_all;
 953                 }
 954                 KASSERT(mp != NULL,
 955                     ("vp %p with NULL v_mount", vp));
 956                 vm_object_reference_locked(object);
 957                 pindex = m->pindex;
 958                 VM_OBJECT_WUNLOCK(object);
 959                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 960                     LK_SHARED : LK_EXCLUSIVE;
 961                 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
 962                         vp = NULL;
 963                         error = EDEADLK;
 964                         goto unlock_mp;
 965                 }
 966                 VM_OBJECT_WLOCK(object);
 967                 vm_page_lock(m);
 968                 /*
 969                  * While the object and page were unlocked, the page
 970                  * may have been:
 971                  * (1) moved to a different queue,
 972                  * (2) reallocated to a different object,
 973                  * (3) reallocated to a different offset, or
 974                  * (4) cleaned.
 975                  */
 976                 if (m->queue != PQ_INACTIVE || m->object != object ||
 977                     m->pindex != pindex || m->dirty == 0) {
 978                         vm_page_unlock(m);
 979                         error = ENXIO;
 980                         goto unlock_all;
 981                 }
 982
 983                 /*
 984                  * The page may have been busied or held while the object
 985                  * and page locks were released.
 986                  */
 987                 if (vm_page_busied(m) || m->hold_count != 0) {
 988                         vm_page_unlock(m);
 989                         error = EBUSY;
 990                         goto unlock_all;
 991                 }
 992         }
 993
 994         /*
 995          * If a page is dirty, then it is either being washed
 996          * (but not yet cleaned) or it is still in the
 997          * laundry.  If it is still in the laundry, then we
 998          * start the cleaning operation.
 999          */
1000         if (vm_pageout_cluster(m) == 0)
1001                 error = EIO;
1002
1003 unlock_all:
1004         VM_OBJECT_WUNLOCK(object);
1005
1006 unlock_mp:
1007         vm_page_lock_assert(m, MA_NOTOWNED);
1008         if (mp != NULL) {
1009                 if (vp != NULL)
1010                         vput(vp);
1011                 vm_object_deallocate(object);
1012                 vn_finished_write(mp);
1013         }
1014
1015         return (error);
1016 }
1017
1018 /*
1019  *      vm_pageout_scan does the dirty work for the pageout daemon.
1020  *
1021  *      pass 0 - Update active LRU/deactivate pages
1022  *      pass 1 - Move inactive to cache or free
1023  *      pass 2 - Launder dirty pages
1024  */
1025 static void
1026 vm_pageout_scan(struct vm_domain *vmd, int pass)
1027 {
1028         vm_page_t m, next;
1029         struct vm_pagequeue *pq;
1030         vm_object_t object;
1031         long min_scan;
1032         int act_delta, addl_page_shortage, deficit, error, maxlaunder, maxscan;
1033         int page_shortage, scan_tick, scanned, vnodes_skipped;
1034         boolean_t pageout_ok, queues_locked;
1035
1036         /*
1037          * If we need to reclaim memory ask kernel caches to return
1038          * some.  We rate limit to avoid thrashing.
1039          */
1040         if (vmd == &vm_dom[0] && pass > 0 &&
1041             (time_uptime - lowmem_uptime) >= lowmem_period) {
1042                 /*
1043                  * Decrease registered cache sizes.
1044                  */
1045                 SDT_PROBE0(vm, , , vm__lowmem_scan);
1046                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
1047                 /*
1048                  * We do this explicitly after the caches have been
1049                  * drained above.
1050                  */
1051                 uma_reclaim();
1052                 lowmem_uptime = time_uptime;
1053         }
1054
1055         /*
1056          * The addl_page_shortage is the number of temporarily
1057          * stuck pages in the inactive queue.  In other words, the
1058          * number of pages from the inactive count that should be
1059          * discounted in setting the target for the active queue scan.
1060          */
1061         addl_page_shortage = 0;
1062
1063         /*
1064          * Calculate the number of pages we want to either free or move
1065          * to the cache.
1066          */
1067         if (pass > 0) {
1068                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
1069                 page_shortage = vm_paging_target() + deficit;
1070         } else
1071                 page_shortage = deficit = 0;
1072
1073         /*
1074          * maxlaunder limits the number of dirty pages we flush per scan.
1075          * For most systems a smaller value (16 or 32) is more robust under
1076          * extreme memory and disk pressure because any unnecessary writes
1077          * to disk can result in extreme performance degredation.  However,
1078          * systems with excessive dirty pages (especially when MAP_NOSYNC is
1079          * used) will die horribly with limited laundering.  If the pageout
1080          * daemon cannot clean enough pages in the first pass, we let it go
1081          * all out in succeeding passes.
1082          */
1083         if ((maxlaunder = vm_max_launder) <= 1)
1084                 maxlaunder = 1;
1085         if (pass > 1)
1086                 maxlaunder = 10000;
1087
1088         vnodes_skipped = 0;
1089
1090         /*
1091          * Start scanning the inactive queue for pages we can move to the
1092          * cache or free.  The scan will stop when the target is reached or
1093          * we have scanned the entire inactive queue.  Note that m->act_count
1094          * is not used to form decisions for the inactive queue, only for the
1095          * active queue.
1096          */
1097         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
1098         maxscan = pq->pq_cnt;
1099         vm_pagequeue_lock(pq);
1100         queues_locked = TRUE;
1101         for (m = TAILQ_FIRST(&pq->pq_pl);
1102              m != NULL && maxscan-- > 0 && page_shortage > 0;
1103              m = next) {
1104                 vm_pagequeue_assert_locked(pq);
1105                 KASSERT(queues_locked, ("unlocked queues"));
1106                 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
1107
1108                 PCPU_INC(cnt.v_pdpages);
1109                 next = TAILQ_NEXT(m, plinks.q);
1110
1111                 /*
1112                  * skip marker pages
1113                  */
1114                 if (m->flags & PG_MARKER)
1115                         continue;
1116
1117                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1118                     ("Fictitious page %p cannot be in inactive queue", m));
1119                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1120                     ("Unmanaged page %p cannot be in inactive queue", m));
1121
1122                 /*
1123                  * The page or object lock acquisitions fail if the
1124                  * page was removed from the queue or moved to a
1125                  * different position within the queue.  In either
1126                  * case, addl_page_shortage should not be incremented.
1127                  */
1128                 if (!vm_pageout_page_lock(m, &next))
1129                         goto unlock_page;
1130                 else if (m->hold_count != 0) {
1131                         /*
1132                          * Held pages are essentially stuck in the
1133                          * queue.  So, they ought to be discounted
1134                          * from the inactive count.  See the
1135                          * calculation of the page_shortage for the
1136                          * loop over the active queue below.
1137                          */
1138                         addl_page_shortage++;
1139                         goto unlock_page;
1140                 }
1141                 object = m->object;
1142                 if (!VM_OBJECT_TRYWLOCK(object)) {
1143                         if (!vm_pageout_fallback_object_lock(m, &next))
1144                                 goto unlock_object;
1145                         else if (m->hold_count != 0) {
1146                                 addl_page_shortage++;
1147                                 goto unlock_object;
1148                         }
1149                 }
1150                 if (vm_page_busied(m)) {
1151                         /*
1152                          * Don't mess with busy pages.  Leave them at
1153                          * the front of the queue.  Most likely, they
1154                          * are being paged out and will leave the
1155                          * queue shortly after the scan finishes.  So,
1156                          * they ought to be discounted from the
1157                          * inactive count.
1158                          */
1159                         addl_page_shortage++;
1160 unlock_object:
1161                         VM_OBJECT_WUNLOCK(object);
1162 unlock_page:
1163                         vm_page_unlock(m);
1164                         continue;
1165                 }
1166                 KASSERT(m->hold_count == 0, ("Held page %p", m));
1167
1168                 /*
1169                  * We unlock the inactive page queue, invalidating the
1170                  * 'next' pointer.  Use our marker to remember our
1171                  * place.
1172                  */
1173                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
1174                 vm_pagequeue_unlock(pq);
1175                 queues_locked = FALSE;
1176
1177                 /*
1178                  * Invalid pages can be easily freed. They cannot be
1179                  * mapped, vm_page_free() asserts this.
1180                  */
1181                 if (m->valid == 0) {
1182                         vm_page_free(m);
1183                         PCPU_INC(cnt.v_dfree);
1184                         --page_shortage;
1185                         goto drop_page;
1186                 }
1187
1188                 /*
1189                  * If the page has been referenced and the object is not dead,
1190                  * reactivate or requeue the page depending on whether the
1191                  * object is mapped.
1192                  */
1193                 if ((m->aflags & PGA_REFERENCED) != 0) {
1194                         vm_page_aflag_clear(m, PGA_REFERENCED);
1195                         act_delta = 1;
1196                 } else
1197                         act_delta = 0;
1198                 if (object->ref_count != 0) {
1199                         act_delta += pmap_ts_referenced(m);
1200                 } else {
1201                         KASSERT(!pmap_page_is_mapped(m),
1202                             ("vm_pageout_scan: page %p is mapped", m));
1203                 }
1204                 if (act_delta != 0) {
1205                         if (object->ref_count != 0) {
1206                                 vm_page_activate(m);
1207
1208                                 /*
1209                                  * Increase the activation count if the page
1210                                  * was referenced while in the inactive queue.
1211                                  * This makes it less likely that the page will
1212                                  * be returned prematurely to the inactive
1213                                  * queue.
1214                                  */
1215                                 m->act_count += act_delta + ACT_ADVANCE;
1216                                 goto drop_page;
1217                         } else if ((object->flags & OBJ_DEAD) == 0) {
1218                                 vm_pagequeue_lock(pq);
1219                                 queues_locked = TRUE;
1220                                 vm_page_requeue_locked(m);
1221                                 goto drop_page;
1222                         }
1223                 }
1224
1225                 /*
1226                  * If the page appears to be clean at the machine-independent
1227                  * layer, then remove all of its mappings from the pmap in
1228                  * anticipation of placing it onto the cache queue.  If,
1229                  * however, any of the page's mappings allow write access,
1230                  * then the page may still be modified until the last of those
1231                  * mappings are removed.
1232                  */
1233                 if (object->ref_count != 0) {
1234                         vm_page_test_dirty(m);
1235                         if (m->dirty == 0)
1236                                 pmap_remove_all(m);
1237                 }
1238
1239                 if (m->dirty == 0) {
1240                         /*
1241                          * Clean pages can be freed.
1242                          */
1243                         vm_page_free(m);
1244                         PCPU_INC(cnt.v_dfree);
1245                         --page_shortage;
1246                 } else if ((object->flags & OBJ_DEAD) != 0) {
1247                         /*
1248                          * Leave dirty pages from dead objects at the front of
1249                          * the queue.  They are being paged out and freed by
1250                          * the thread that destroyed the object.  They will
1251                          * leave the queue shortly after the scan finishes, so
1252                          * they should be discounted from the inactive count.
1253                          */
1254                         addl_page_shortage++;
1255                 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
1256                         /*
1257                          * Dirty pages need to be paged out, but flushing
1258                          * a page is extremely expensive versus freeing
1259                          * a clean page.  Rather then artificially limiting
1260                          * the number of pages we can flush, we instead give
1261                          * dirty pages extra priority on the inactive queue
1262                          * by forcing them to be cycled through the queue
1263                          * twice before being flushed, after which the
1264                          * (now clean) page will cycle through once more
1265                          * before being freed.  This significantly extends
1266                          * the thrash point for a heavily loaded machine.
1267                          */
1268                         m->flags |= PG_WINATCFLS;
1269                         vm_pagequeue_lock(pq);
1270                         queues_locked = TRUE;
1271                         vm_page_requeue_locked(m);
1272                 } else if (maxlaunder > 0) {
1273                         /*
1274                          * We always want to try to flush some dirty pages if
1275                          * we encounter them, to keep the system stable.
1276                          * Normally this number is small, but under extreme
1277                          * pressure where there are insufficient clean pages
1278                          * on the inactive queue, we may have to go all out.
1279                          */
1280
1281                         if (object->type != OBJT_SWAP &&
1282                             object->type != OBJT_DEFAULT)
1283                                 pageout_ok = TRUE;
1284                         else if (disable_swap_pageouts)
1285                                 pageout_ok = FALSE;
1286                         else if (defer_swap_pageouts)
1287                                 pageout_ok = vm_page_count_min();
1288                         else
1289                                 pageout_ok = TRUE;
1290                         if (!pageout_ok) {
1291                                 vm_pagequeue_lock(pq);
1292                                 queues_locked = TRUE;
1293                                 vm_page_requeue_locked(m);
1294                                 goto drop_page;
1295                         }
1296                         error = vm_pageout_clean(m);
1297                         /*
1298                          * Decrement page_shortage on success to account for
1299                          * the (future) cleaned page.  Otherwise we could wind
1300                          * up laundering or cleaning too many pages.
1301                          */
1302                         if (error == 0) {
1303                                 page_shortage--;
1304                                 maxlaunder--;
1305                         } else if (error == EDEADLK) {
1306                                 pageout_lock_miss++;
1307                                 vnodes_skipped++;
1308                         } else if (error == EBUSY) {
1309                                 addl_page_shortage++;
1310                         }
1311                         vm_page_lock_assert(m, MA_NOTOWNED);
1312                         goto relock_queues;
1313                 }
1314 drop_page:
1315                 vm_page_unlock(m);
1316                 VM_OBJECT_WUNLOCK(object);
1317 relock_queues:
1318                 if (!queues_locked) {
1319                         vm_pagequeue_lock(pq);
1320                         queues_locked = TRUE;
1321                 }
1322                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
1323                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
1324         }
1325         vm_pagequeue_unlock(pq);
1326
1327 #if !defined(NO_SWAPPING)
1328         /*
1329          * Wakeup the swapout daemon if we didn't cache or free the targeted
1330          * number of pages.
1331          */
1332         if (vm_swap_enabled && page_shortage > 0)
1333                 vm_req_vmdaemon(VM_SWAP_NORMAL);
1334 #endif
1335
1336         /*
1337          * Wakeup the sync daemon if we skipped a vnode in a writeable object
1338          * and we didn't cache or free enough pages.
1339          */
1340         if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target -
1341             vm_cnt.v_free_min)
1342                 (void)speedup_syncer();
1343
1344         /*
1345          * Compute the number of pages we want to try to move from the
1346          * active queue to the inactive queue.
1347          */
1348         page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count +
1349             vm_paging_target() + deficit + addl_page_shortage;
1350
1351         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1352         vm_pagequeue_lock(pq);
1353         maxscan = pq->pq_cnt;
1354
1355         /*
1356          * If we're just idle polling attempt to visit every
1357          * active page within 'update_period' seconds.
1358          */
1359         scan_tick = ticks;
1360         if (vm_pageout_update_period != 0) {
1361                 min_scan = pq->pq_cnt;
1362                 min_scan *= scan_tick - vmd->vmd_last_active_scan;
1363                 min_scan /= hz * vm_pageout_update_period;
1364         } else
1365                 min_scan = 0;
1366         if (min_scan > 0 || (page_shortage > 0 && maxscan > 0))
1367                 vmd->vmd_last_active_scan = scan_tick;
1368
1369         /*
1370          * Scan the active queue for pages that can be deactivated.  Update
1371          * the per-page activity counter and use it to identify deactivation
1372          * candidates.
1373          */
1374         for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned <
1375             min_scan || (page_shortage > 0 && scanned < maxscan)); m = next,
1376             scanned++) {
1377
1378                 KASSERT(m->queue == PQ_ACTIVE,
1379                     ("vm_pageout_scan: page %p isn't active", m));
1380
1381                 next = TAILQ_NEXT(m, plinks.q);
1382                 if ((m->flags & PG_MARKER) != 0)
1383                         continue;
1384                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1385                     ("Fictitious page %p cannot be in active queue", m));
1386                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1387                     ("Unmanaged page %p cannot be in active queue", m));
1388                 if (!vm_pageout_page_lock(m, &next)) {
1389                         vm_page_unlock(m);
1390                         continue;
1391                 }
1392
1393                 /*
1394                  * The count for pagedaemon pages is done after checking the
1395                  * page for eligibility...
1396                  */
1397                 PCPU_INC(cnt.v_pdpages);
1398
1399                 /*
1400                  * Check to see "how much" the page has been used.
1401                  */
1402                 if ((m->aflags & PGA_REFERENCED) != 0) {
1403                         vm_page_aflag_clear(m, PGA_REFERENCED);
1404                         act_delta = 1;
1405                 } else
1406                         act_delta = 0;
1407
1408                 /*
1409                  * Unlocked object ref count check.  Two races are possible.
1410                  * 1) The ref was transitioning to zero and we saw non-zero,
1411                  *    the pmap bits will be checked unnecessarily.
1412                  * 2) The ref was transitioning to one and we saw zero.
1413                  *    The page lock prevents a new reference to this page so
1414                  *    we need not check the reference bits.
1415                  */
1416                 if (m->object->ref_count != 0)
1417                         act_delta += pmap_ts_referenced(m);
1418
1419                 /*
1420                  * Advance or decay the act_count based on recent usage.
1421                  */
1422                 if (act_delta != 0) {
1423                         m->act_count += ACT_ADVANCE + act_delta;
1424                         if (m->act_count > ACT_MAX)
1425                                 m->act_count = ACT_MAX;
1426                 } else
1427                         m->act_count -= min(m->act_count, ACT_DECLINE);
1428
1429                 /*
1430                  * Move this page to the tail of the active or inactive
1431                  * queue depending on usage.
1432                  */
1433                 if (m->act_count == 0) {
1434                         /* Dequeue to avoid later lock recursion. */
1435                         vm_page_dequeue_locked(m);
1436                         vm_page_deactivate(m);
1437                         page_shortage--;
1438                 } else
1439                         vm_page_requeue_locked(m);
1440                 vm_page_unlock(m);
1441         }
1442         vm_pagequeue_unlock(pq);
1443 #if !defined(NO_SWAPPING)
1444         /*
1445          * Idle process swapout -- run once per second.
1446          */
1447         if (vm_swap_idle_enabled) {
1448                 static long lsec;
1449                 if (time_second != lsec) {
1450                         vm_req_vmdaemon(VM_SWAP_IDLE);
1451                         lsec = time_second;
1452                 }
1453         }
1454 #endif
1455
1456         /*
1457          * If we are critically low on one of RAM or swap and low on
1458          * the other, kill the largest process.  However, we avoid
1459          * doing this on the first pass in order to give ourselves a
1460          * chance to flush out dirty vnode-backed pages and to allow
1461          * active pages to be moved to the inactive queue and reclaimed.
1462          */
1463         vm_pageout_mightbe_oom(vmd, pass);
1464 }
1465
1466 static int vm_pageout_oom_vote;
1467
1468 /*
1469  * The pagedaemon threads randlomly select one to perform the
1470  * OOM.  Trying to kill processes before all pagedaemons
1471  * failed to reach free target is premature.
1472  */
1473 static void
1474 vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
1475 {
1476         int old_vote;
1477
1478         if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
1479             (swap_pager_full && vm_paging_target() > 0))) {
1480                 if (vmd->vmd_oom) {
1481                         vmd->vmd_oom = FALSE;
1482                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1483                 }
1484                 return;
1485         }
1486
1487         if (vmd->vmd_oom)
1488                 return;
1489
1490         vmd->vmd_oom = TRUE;
1491         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1492         if (old_vote != vm_ndomains - 1)
1493                 return;
1494
1495         /*
1496          * The current pagedaemon thread is the last in the quorum to
1497          * start OOM.  Initiate the selection and signaling of the
1498          * victim.
1499          */
1500         vm_pageout_oom(VM_OOM_MEM);
1501
1502         /*
1503          * After one round of OOM terror, recall our vote.  On the
1504          * next pass, current pagedaemon would vote again if the low
1505          * memory condition is still there, due to vmd_oom being
1506          * false.
1507          */
1508         vmd->vmd_oom = FALSE;
1509         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1510 }
1511
1512 void
1513 vm_pageout_oom(int shortage)
1514 {
1515         struct proc *p, *bigproc;
1516         vm_offset_t size, bigsize;
1517         struct thread *td;
1518         struct vmspace *vm;
1519
1520         /*
1521          * We keep the process bigproc locked once we find it to keep anyone
1522          * from messing with it; however, there is a possibility of
1523          * deadlock if process B is bigproc and one of it's child processes
1524          * attempts to propagate a signal to B while we are waiting for A's
1525          * lock while walking this list.  To avoid this, we don't block on
1526          * the process lock but just skip a process if it is already locked.
1527          */
1528         bigproc = NULL;
1529         bigsize = 0;
1530         sx_slock(&allproc_lock);
1531         FOREACH_PROC_IN_SYSTEM(p) {
1532                 int breakout;
1533
1534                 PROC_LOCK(p);
1535
1536                 /*
1537                  * If this is a system, protected or killed process, skip it.
1538                  */
1539                 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1540                     P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1541                     p->p_pid == 1 || P_KILLED(p) ||
1542                     (p->p_pid < 48 && swap_pager_avail != 0)) {
1543                         PROC_UNLOCK(p);
1544                         continue;
1545                 }
1546                 /*
1547                  * If the process is in a non-running type state,
1548                  * don't touch it.  Check all the threads individually.
1549                  */
1550                 breakout = 0;
1551                 FOREACH_THREAD_IN_PROC(p, td) {
1552                         thread_lock(td);
1553                         if (!TD_ON_RUNQ(td) &&
1554                             !TD_IS_RUNNING(td) &&
1555                             !TD_IS_SLEEPING(td) &&
1556                             !TD_IS_SUSPENDED(td)) {
1557                                 thread_unlock(td);
1558                                 breakout = 1;
1559                                 break;
1560                         }
1561                         thread_unlock(td);
1562                 }
1563                 if (breakout) {
1564                         PROC_UNLOCK(p);
1565                         continue;
1566                 }
1567                 /*
1568                  * get the process size
1569                  */
1570                 vm = vmspace_acquire_ref(p);
1571                 if (vm == NULL) {
1572                         PROC_UNLOCK(p);
1573                         continue;
1574                 }
1575                 _PHOLD(p);
1576                 if (!vm_map_trylock_read(&vm->vm_map)) {
1577                         _PRELE(p);
1578                         PROC_UNLOCK(p);
1579                         vmspace_free(vm);
1580                         continue;
1581                 }
1582                 PROC_UNLOCK(p);
1583                 size = vmspace_swap_count(vm);
1584                 vm_map_unlock_read(&vm->vm_map);
1585                 if (shortage == VM_OOM_MEM)
1586                         size += vmspace_resident_count(vm);
1587                 vmspace_free(vm);
1588                 /*
1589                  * if the this process is bigger than the biggest one
1590                  * remember it.
1591                  */
1592                 if (size > bigsize) {
1593                         if (bigproc != NULL)
1594                                 PRELE(bigproc);
1595                         bigproc = p;
1596                         bigsize = size;
1597                 } else {
1598                         PRELE(p);
1599                 }
1600         }
1601         sx_sunlock(&allproc_lock);
1602         if (bigproc != NULL) {
1603                 if (vm_panic_on_oom != 0)
1604                         panic("out of swap space");
1605                 PROC_LOCK(bigproc);
1606                 killproc(bigproc, "out of swap space");
1607                 sched_nice(bigproc, PRIO_MIN);
1608                 _PRELE(bigproc);
1609                 PROC_UNLOCK(bigproc);
1610                 wakeup(&vm_cnt.v_free_count);
1611         }
1612 }
1613
1614 static void
1615 vm_pageout_worker(void *arg)
1616 {
1617         struct vm_domain *domain;
1618         int domidx;
1619
1620         domidx = (uintptr_t)arg;
1621         domain = &vm_dom[domidx];
1622
1623         /*
1624          * XXXKIB It could be useful to bind pageout daemon threads to
1625          * the cores belonging to the domain, from which vm_page_array
1626          * is allocated.
1627          */
1628
1629         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
1630         domain->vmd_last_active_scan = ticks;
1631         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
1632
1633         /*
1634          * The pageout daemon worker is never done, so loop forever.
1635          */
1636         while (TRUE) {
1637                 /*
1638                  * If we have enough free memory, wakeup waiters.  Do
1639                  * not clear vm_pages_needed until we reach our target,
1640                  * otherwise we may be woken up over and over again and
1641                  * waste a lot of cpu.
1642                  */
1643                 mtx_lock(&vm_page_queue_free_mtx);
1644                 if (vm_pages_needed && !vm_page_count_min()) {
1645                         if (!vm_paging_needed())
1646                                 vm_pages_needed = 0;
1647                         wakeup(&vm_cnt.v_free_count);
1648                 }
1649                 if (vm_pages_needed) {
1650                         /*
1651                          * Still not done, take a second pass without waiting
1652                          * (unlimited dirty cleaning), otherwise sleep a bit
1653                          * and try again.
1654                          */
1655                         if (domain->vmd_pass > 1)
1656                                 msleep(&vm_pages_needed,
1657                                     &vm_page_queue_free_mtx, PVM, "psleep",
1658                                     hz / 2);
1659                 } else {
1660                         /*
1661                          * Good enough, sleep until required to refresh
1662                          * stats.
1663                          */
1664                         domain->vmd_pass = 0;
1665                         msleep(&vm_pages_needed, &vm_page_queue_free_mtx,
1666                             PVM, "psleep", hz);
1667
1668                 }
1669                 if (vm_pages_needed) {
1670                         vm_cnt.v_pdwakeups++;
1671                         domain->vmd_pass++;
1672                 }
1673                 mtx_unlock(&vm_page_queue_free_mtx);
1674                 vm_pageout_scan(domain, domain->vmd_pass);
1675         }
1676 }
1677
1678 /*
1679  *      vm_pageout_init initialises basic pageout daemon settings.
1680  */
1681 static void
1682 vm_pageout_init(void)
1683 {
1684         /*
1685          * Initialize some paging parameters.
1686          */
1687         vm_cnt.v_interrupt_free_min = 2;
1688         if (vm_cnt.v_page_count < 2000)
1689                 vm_pageout_page_count = 8;
1690
1691         /*
1692          * v_free_reserved needs to include enough for the largest
1693          * swap pager structures plus enough for any pv_entry structs
1694          * when paging.
1695          */
1696         if (vm_cnt.v_page_count > 1024)
1697                 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
1698         else
1699                 vm_cnt.v_free_min = 4;
1700         vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1701             vm_cnt.v_interrupt_free_min;
1702         vm_cnt.v_free_reserved = vm_pageout_page_count +
1703             vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
1704         vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
1705         vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
1706         vm_cnt.v_free_min += vm_cnt.v_free_reserved;
1707         vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
1708         vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
1709         if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
1710                 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
1711
1712         /*
1713          * Set the default wakeup threshold to be 10% above the minimum
1714          * page limit.  This keeps the steady state out of shortfall.
1715          */
1716         vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
1717
1718         /*
1719          * Set interval in seconds for active scan.  We want to visit each
1720          * page at least once every ten minutes.  This is to prevent worst
1721          * case paging behaviors with stale active LRU.
1722          */
1723         if (vm_pageout_update_period == 0)
1724                 vm_pageout_update_period = 600;
1725
1726         /* XXX does not really belong here */
1727         if (vm_page_max_wired == 0)
1728                 vm_page_max_wired = vm_cnt.v_free_count / 3;
1729 }
1730
1731 /*
1732  *     vm_pageout is the high level pageout daemon.
1733  */
1734 static void
1735 vm_pageout(void)
1736 {
1737         int error;
1738 #if MAXMEMDOM > 1
1739         int i;
1740 #endif
1741
1742         swap_pager_swap_init();
1743 #if MAXMEMDOM > 1
1744         for (i = 1; i < vm_ndomains; i++) {
1745                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
1746                     curproc, NULL, 0, 0, "dom%d", i);
1747                 if (error != 0) {
1748                         panic("starting pageout for domain %d, error %d\n",
1749                             i, error);
1750                 }
1751         }
1752 #endif
1753         error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
1754             0, 0, "uma");
1755         if (error != 0)
1756                 panic("starting uma_reclaim helper, error %d\n", error);
1757         vm_pageout_worker((void *)(uintptr_t)0);
1758 }
1759
1760 /*
1761  * Unless the free page queue lock is held by the caller, this function
1762  * should be regarded as advisory.  Specifically, the caller should
1763  * not msleep() on &vm_cnt.v_free_count following this function unless
1764  * the free page queue lock is held until the msleep() is performed.
1765  */
1766 void
1767 pagedaemon_wakeup(void)
1768 {
1769
1770         if (!vm_pages_needed && curthread->td_proc != pageproc) {
1771                 vm_pages_needed = 1;
1772                 wakeup(&vm_pages_needed);
1773         }
1774 }
1775
1776 #if !defined(NO_SWAPPING)
1777 static void
1778 vm_req_vmdaemon(int req)
1779 {
1780         static int lastrun = 0;
1781
1782         mtx_lock(&vm_daemon_mtx);
1783         vm_pageout_req_swapout |= req;
1784         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1785                 wakeup(&vm_daemon_needed);
1786                 lastrun = ticks;
1787         }
1788         mtx_unlock(&vm_daemon_mtx);
1789 }
1790
1791 static void
1792 vm_daemon(void)
1793 {
1794         struct rlimit rsslim;
1795         struct proc *p;
1796         struct thread *td;
1797         struct vmspace *vm;
1798         int breakout, swapout_flags, tryagain, attempts;
1799 #ifdef RACCT
1800         uint64_t rsize, ravailable;
1801 #endif
1802
1803         while (TRUE) {
1804                 mtx_lock(&vm_daemon_mtx);
1805                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
1806 #ifdef RACCT
1807                     racct_enable ? hz : 0
1808 #else
1809                     0
1810 #endif
1811                 );
1812                 swapout_flags = vm_pageout_req_swapout;
1813                 vm_pageout_req_swapout = 0;
1814                 mtx_unlock(&vm_daemon_mtx);
1815                 if (swapout_flags)
1816                         swapout_procs(swapout_flags);
1817
1818                 /*
1819                  * scan the processes for exceeding their rlimits or if
1820                  * process is swapped out -- deactivate pages
1821                  */
1822                 tryagain = 0;
1823                 attempts = 0;
1824 again:
1825                 attempts++;
1826                 sx_slock(&allproc_lock);
1827                 FOREACH_PROC_IN_SYSTEM(p) {
1828                         vm_pindex_t limit, size;
1829
1830                         /*
1831                          * if this is a system process or if we have already
1832                          * looked at this process, skip it.
1833                          */
1834                         PROC_LOCK(p);
1835                         if (p->p_state != PRS_NORMAL ||
1836                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1837                                 PROC_UNLOCK(p);
1838                                 continue;
1839                         }
1840                         /*
1841                          * if the process is in a non-running type state,
1842                          * don't touch it.
1843                          */
1844                         breakout = 0;
1845                         FOREACH_THREAD_IN_PROC(p, td) {
1846                                 thread_lock(td);
1847                                 if (!TD_ON_RUNQ(td) &&
1848                                     !TD_IS_RUNNING(td) &&
1849                                     !TD_IS_SLEEPING(td) &&
1850                                     !TD_IS_SUSPENDED(td)) {
1851                                         thread_unlock(td);
1852                                         breakout = 1;
1853                                         break;
1854                                 }
1855                                 thread_unlock(td);
1856                         }
1857                         if (breakout) {
1858                                 PROC_UNLOCK(p);
1859                                 continue;
1860                         }
1861                         /*
1862                          * get a limit
1863                          */
1864                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
1865                         limit = OFF_TO_IDX(
1866                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
1867
1868                         /*
1869                          * let processes that are swapped out really be
1870                          * swapped out set the limit to nothing (will force a
1871                          * swap-out.)
1872                          */
1873                         if ((p->p_flag & P_INMEM) == 0)
1874                                 limit = 0;      /* XXX */
1875                         vm = vmspace_acquire_ref(p);
1876                         PROC_UNLOCK(p);
1877                         if (vm == NULL)
1878                                 continue;
1879
1880                         size = vmspace_resident_count(vm);
1881                         if (size >= limit) {
1882                                 vm_pageout_map_deactivate_pages(
1883                                     &vm->vm_map, limit);
1884                         }
1885 #ifdef RACCT
1886                         if (racct_enable) {
1887                                 rsize = IDX_TO_OFF(size);
1888                                 PROC_LOCK(p);
1889                                 racct_set(p, RACCT_RSS, rsize);
1890                                 ravailable = racct_get_available(p, RACCT_RSS);
1891                                 PROC_UNLOCK(p);
1892                                 if (rsize > ravailable) {
1893                                         /*
1894                                          * Don't be overly aggressive; this
1895                                          * might be an innocent process,
1896                                          * and the limit could've been exceeded
1897                                          * by some memory hog.  Don't try
1898                                          * to deactivate more than 1/4th
1899                                          * of process' resident set size.
1900                                          */
1901                                         if (attempts <= 8) {
1902                                                 if (ravailable < rsize -
1903                                                     (rsize / 4)) {
1904                                                         ravailable = rsize -
1905                                                             (rsize / 4);
1906                                                 }
1907                                         }
1908                                         vm_pageout_map_deactivate_pages(
1909                                             &vm->vm_map,
1910                                             OFF_TO_IDX(ravailable));
1911                                         /* Update RSS usage after paging out. */
1912                                         size = vmspace_resident_count(vm);
1913                                         rsize = IDX_TO_OFF(size);
1914                                         PROC_LOCK(p);
1915                                         racct_set(p, RACCT_RSS, rsize);
1916                                         PROC_UNLOCK(p);
1917                                         if (rsize > ravailable)
1918                                                 tryagain = 1;
1919                                 }
1920                         }
1921 #endif
1922                         vmspace_free(vm);
1923                 }
1924                 sx_sunlock(&allproc_lock);
1925                 if (tryagain != 0 && attempts <= 10)
1926                         goto again;
1927         }
1928 }
1929 #endif                  /* !defined(NO_SWAPPING) */