sys/vm/vm_pageout.c

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