sys/vm/vm_pageout.c

   1 /*-
   2  * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
   3  *
   4  * Copyright (c) 1991 Regents of the University of California.
   5  * All rights reserved.
   6  * Copyright (c) 1994 John S. Dyson
   7  * All rights reserved.
   8  * Copyright (c) 1994 David Greenman
   9  * All rights reserved.
  10  * Copyright (c) 2005 Yahoo! Technologies Norway AS
  11  * All rights reserved.
  12  *
  13  * This code is derived from software contributed to Berkeley by
  14  * The Mach Operating System project at Carnegie-Mellon University.
  15  *
  16  * Redistribution and use in source and binary forms, with or without
  17  * modification, are permitted provided that the following conditions
  18  * are met:
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  * 3. All advertising materials mentioning features or use of this software
  25  *    must display the following acknowledgement:
  26  *      This product includes software developed by the University of
  27  *      California, Berkeley and its contributors.
  28  * 4. Neither the name of the University nor the names of its contributors
  29  *    may be used to endorse or promote products derived from this software
  30  *    without specific prior written permission.
  31  *
  32  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  33  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  34  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  35  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  36  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  37  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  38  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  39  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  40  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  41  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  42  * SUCH DAMAGE.
  43  *
  44  *      from: @(#)vm_pageout.c  7.4 (Berkeley) 5/7/91
  45  *
  46  *
  47  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  48  * All rights reserved.
  49  *
  50  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  51  *
  52  * Permission to use, copy, modify and distribute this software and
  53  * its documentation is hereby granted, provided that both the copyright
  54  * notice and this permission notice appear in all copies of the
  55  * software, derivative works or modified versions, and any portions
  56  * thereof, and that both notices appear in supporting documentation.
  57  *
  58  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  59  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  60  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  61  *
  62  * Carnegie Mellon requests users of this software to return to
  63  *
  64  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  65  *  School of Computer Science
  66  *  Carnegie Mellon University
  67  *  Pittsburgh PA 15213-3890
  68  *
  69  * any improvements or extensions that they make and grant Carnegie the
  70  * rights to redistribute these changes.
  71  */
  72
  73 /*
  74  *      The proverbial page-out daemon.
  75  */
  76
  77 #include <sys/cdefs.h>
  78 __FBSDID("$FreeBSD$");
  79
  80 #include "opt_vm.h"
  81
  82 #include <sys/param.h>
  83 #include <sys/systm.h>
  84 #include <sys/kernel.h>
  85 #include <sys/eventhandler.h>
  86 #include <sys/lock.h>
  87 #include <sys/mutex.h>
  88 #include <sys/proc.h>
  89 #include <sys/kthread.h>
  90 #include <sys/ktr.h>
  91 #include <sys/mount.h>
  92 #include <sys/racct.h>
  93 #include <sys/resourcevar.h>
  94 #include <sys/sched.h>
  95 #include <sys/sdt.h>
  96 #include <sys/signalvar.h>
  97 #include <sys/smp.h>
  98 #include <sys/time.h>
  99 #include <sys/vnode.h>
 100 #include <sys/vmmeter.h>
 101 #include <sys/rwlock.h>
 102 #include <sys/sx.h>
 103 #include <sys/sysctl.h>
 104
 105 #include <vm/vm.h>
 106 #include <vm/vm_param.h>
 107 #include <vm/vm_object.h>
 108 #include <vm/vm_page.h>
 109 #include <vm/vm_map.h>
 110 #include <vm/vm_pageout.h>
 111 #include <vm/vm_pager.h>
 112 #include <vm/vm_phys.h>
 113 #include <vm/swap_pager.h>
 114 #include <vm/vm_extern.h>
 115 #include <vm/uma.h>
 116
 117 /*
 118  * System initialization
 119  */
 120
 121 /* the kernel process "vm_pageout"*/
 122 static void vm_pageout(void);
 123 static void vm_pageout_init(void);
 124 static int vm_pageout_clean(vm_page_t m, int *numpagedout);
 125 static int vm_pageout_cluster(vm_page_t m);
 126 static bool vm_pageout_scan(struct vm_domain *vmd, int pass);
 127 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
 128     int starting_page_shortage);
 129
 130 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
 131     NULL);
 132
 133 struct proc *pageproc;
 134
 135 static struct kproc_desc page_kp = {
 136         "pagedaemon",
 137         vm_pageout,
 138         &pageproc
 139 };
 140 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
 141     &page_kp);
 142
 143 SDT_PROVIDER_DEFINE(vm);
 144 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
 145
 146 /* Pagedaemon activity rates, in subdivisions of one second. */
 147 #define VM_LAUNDER_RATE         10
 148 #define VM_INACT_SCAN_RATE      2
 149
 150 int vm_pageout_deficit;         /* Estimated number of pages deficit */
 151 u_int vm_pageout_wakeup_thresh;
 152 static int vm_pageout_oom_seq = 12;
 153 bool vm_pageout_wanted;         /* Event on which pageout daemon sleeps */
 154 bool vm_pages_needed;           /* Are threads waiting for free pages? */
 155
 156 /* Pending request for dirty page laundering. */
 157 static enum {
 158         VM_LAUNDRY_IDLE,
 159         VM_LAUNDRY_BACKGROUND,
 160         VM_LAUNDRY_SHORTFALL
 161 } vm_laundry_request = VM_LAUNDRY_IDLE;
 162
 163 static int vm_pageout_update_period;
 164 static int disable_swap_pageouts;
 165 static int lowmem_period = 10;
 166 static time_t lowmem_uptime;
 167 static int swapdev_enabled;
 168
 169 static int vm_panic_on_oom = 0;
 170
 171 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
 172         CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
 173         "panic on out of memory instead of killing the largest process");
 174
 175 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
 176         CTLFLAG_RWTUN, &vm_pageout_wakeup_thresh, 0,
 177         "free page threshold for waking up the pageout daemon");
 178
 179 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
 180         CTLFLAG_RWTUN, &vm_pageout_update_period, 0,
 181         "Maximum active LRU update period");
 182
 183 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RWTUN, &lowmem_period, 0,
 184         "Low memory callback period");
 185
 186 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
 187         CTLFLAG_RWTUN, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
 188
 189 static int pageout_lock_miss;
 190 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 191         CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 192
 193 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq,
 194         CTLFLAG_RWTUN, &vm_pageout_oom_seq, 0,
 195         "back-to-back calls to oom detector to start OOM");
 196
 197 static int act_scan_laundry_weight = 3;
 198 SYSCTL_INT(_vm, OID_AUTO, act_scan_laundry_weight, CTLFLAG_RWTUN,
 199     &act_scan_laundry_weight, 0,
 200     "weight given to clean vs. dirty pages in active queue scans");
 201
 202 static u_int vm_background_launder_target;
 203 SYSCTL_UINT(_vm, OID_AUTO, background_launder_target, CTLFLAG_RWTUN,
 204     &vm_background_launder_target, 0,
 205     "background laundering target, in pages");
 206
 207 static u_int vm_background_launder_rate = 4096;
 208 SYSCTL_UINT(_vm, OID_AUTO, background_launder_rate, CTLFLAG_RWTUN,
 209     &vm_background_launder_rate, 0,
 210     "background laundering rate, in kilobytes per second");
 211
 212 static u_int vm_background_launder_max = 20 * 1024;
 213 SYSCTL_UINT(_vm, OID_AUTO, background_launder_max, CTLFLAG_RWTUN,
 214     &vm_background_launder_max, 0, "background laundering cap, in kilobytes");
 215
 216 int vm_pageout_page_count = 32;
 217
 218 int vm_page_max_wired;          /* XXX max # of wired pages system-wide */
 219 SYSCTL_INT(_vm, OID_AUTO, max_wired,
 220         CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
 221
 222 static u_int isqrt(u_int num);
 223 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
 224 static int vm_pageout_launder(struct vm_domain *vmd, int launder,
 225     bool in_shortfall);
 226 static void vm_pageout_laundry_worker(void *arg);
 227 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 228
 229 /*
 230  * Initialize a dummy page for marking the caller's place in the specified
 231  * paging queue.  In principle, this function only needs to set the flag
 232  * PG_MARKER.  Nonetheless, it write busies and initializes the hold count
 233  * to one as safety precautions.
 234  */
 235 static void
 236 vm_pageout_init_marker(vm_page_t marker, u_short queue)
 237 {
 238
 239         bzero(marker, sizeof(*marker));
 240         marker->flags = PG_MARKER;
 241         marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
 242         marker->queue = queue;
 243         marker->hold_count = 1;
 244 }
 245
 246 /*
 247  * vm_pageout_fallback_object_lock:
 248  *
 249  * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
 250  * known to have failed and page queue must be either PQ_ACTIVE or
 251  * PQ_INACTIVE.  To avoid lock order violation, unlock the page queue
 252  * while locking the vm object.  Use marker page to detect page queue
 253  * changes and maintain notion of next page on page queue.  Return
 254  * TRUE if no changes were detected, FALSE otherwise.  vm object is
 255  * locked on return.
 256  *
 257  * This function depends on both the lock portion of struct vm_object
 258  * and normal struct vm_page being type stable.
 259  */
 260 static boolean_t
 261 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
 262 {
 263         struct vm_page marker;
 264         struct vm_pagequeue *pq;
 265         boolean_t unchanged;
 266         u_short queue;
 267         vm_object_t object;
 268
 269         queue = m->queue;
 270         vm_pageout_init_marker(&marker, queue);
 271         pq = vm_page_pagequeue(m);
 272         object = m->object;
 273
 274         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 275         vm_pagequeue_unlock(pq);
 276         vm_page_unlock(m);
 277         VM_OBJECT_WLOCK(object);
 278         vm_page_lock(m);
 279         vm_pagequeue_lock(pq);
 280
 281         /*
 282          * The page's object might have changed, and/or the page might
 283          * have moved from its original position in the queue.  If the
 284          * page's object has changed, then the caller should abandon
 285          * processing the page because the wrong object lock was
 286          * acquired.  Use the marker's plinks.q, not the page's, to
 287          * determine if the page has been moved.  The state of the
 288          * page's plinks.q can be indeterminate; whereas, the marker's
 289          * plinks.q must be valid.
 290          */
 291         *next = TAILQ_NEXT(&marker, plinks.q);
 292         unchanged = m->object == object &&
 293             m == TAILQ_PREV(&marker, pglist, plinks.q);
 294         KASSERT(!unchanged || m->queue == queue,
 295             ("page %p queue %d %d", m, queue, m->queue));
 296         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 297         return (unchanged);
 298 }
 299
 300 /*
 301  * Lock the page while holding the page queue lock.  Use marker page
 302  * to detect page queue changes and maintain notion of next page on
 303  * page queue.  Return TRUE if no changes were detected, FALSE
 304  * otherwise.  The page is locked on return. The page queue lock might
 305  * be dropped and reacquired.
 306  *
 307  * This function depends on normal struct vm_page being type stable.
 308  */
 309 static boolean_t
 310 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
 311 {
 312         struct vm_page marker;
 313         struct vm_pagequeue *pq;
 314         boolean_t unchanged;
 315         u_short queue;
 316
 317         vm_page_lock_assert(m, MA_NOTOWNED);
 318         if (vm_page_trylock(m))
 319                 return (TRUE);
 320
 321         queue = m->queue;
 322         vm_pageout_init_marker(&marker, queue);
 323         pq = vm_page_pagequeue(m);
 324
 325         TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
 326         vm_pagequeue_unlock(pq);
 327         vm_page_lock(m);
 328         vm_pagequeue_lock(pq);
 329
 330         /* Page queue might have changed. */
 331         *next = TAILQ_NEXT(&marker, plinks.q);
 332         unchanged = m == TAILQ_PREV(&marker, pglist, plinks.q);
 333         KASSERT(!unchanged || m->queue == queue,
 334             ("page %p queue %d %d", m, queue, m->queue));
 335         TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
 336         return (unchanged);
 337 }
 338
 339 /*
 340  * Scan for pages at adjacent offsets within the given page's object that are
 341  * eligible for laundering, form a cluster of these pages and the given page,
 342  * and launder that cluster.
 343  */
 344 static int
 345 vm_pageout_cluster(vm_page_t m)
 346 {
 347         vm_object_t object;
 348         vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps;
 349         vm_pindex_t pindex;
 350         int ib, is, page_base, pageout_count;
 351
 352         vm_page_assert_locked(m);
 353         object = m->object;
 354         VM_OBJECT_ASSERT_WLOCKED(object);
 355         pindex = m->pindex;
 356
 357         /*
 358          * We can't clean the page if it is busy or held.
 359          */
 360         vm_page_assert_unbusied(m);
 361         KASSERT(m->hold_count == 0, ("page %p is held", m));
 362
 363         pmap_remove_write(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          * We can cluster only if the page is not clean, busy, or held, and
 374          * the page is in the laundry queue.
 375          *
 376          * During heavy mmap/modification loads the pageout
 377          * daemon can really fragment the underlying file
 378          * due to flushing pages out of order and not trying to
 379          * align the clusters (which leaves sporadic out-of-order
 380          * holes).  To solve this problem we do the reverse scan
 381          * first and attempt to align our cluster, then do a
 382          * forward scan if room remains.
 383          */
 384 more:
 385         while (ib != 0 && pageout_count < vm_pageout_page_count) {
 386                 if (ib > pindex) {
 387                         ib = 0;
 388                         break;
 389                 }
 390                 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
 391                         ib = 0;
 392                         break;
 393                 }
 394                 vm_page_test_dirty(p);
 395                 if (p->dirty == 0) {
 396                         ib = 0;
 397                         break;
 398                 }
 399                 vm_page_lock(p);
 400                 if (!vm_page_in_laundry(p) ||
 401                     p->hold_count != 0) {       /* may be undergoing I/O */
 402                         vm_page_unlock(p);
 403                         ib = 0;
 404                         break;
 405                 }
 406                 pmap_remove_write(p);
 407                 vm_page_unlock(p);
 408                 mc[--page_base] = pb = p;
 409                 ++pageout_count;
 410                 ++ib;
 411
 412                 /*
 413                  * We are at an alignment boundary.  Stop here, and switch
 414                  * directions.  Do not clear ib.
 415                  */
 416                 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 417                         break;
 418         }
 419         while (pageout_count < vm_pageout_page_count &&
 420             pindex + is < object->size) {
 421                 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
 422                         break;
 423                 vm_page_test_dirty(p);
 424                 if (p->dirty == 0)
 425                         break;
 426                 vm_page_lock(p);
 427                 if (!vm_page_in_laundry(p) ||
 428                     p->hold_count != 0) {       /* may be undergoing I/O */
 429                         vm_page_unlock(p);
 430                         break;
 431                 }
 432                 pmap_remove_write(p);
 433                 vm_page_unlock(p);
 434                 mc[page_base + pageout_count] = ps = p;
 435                 ++pageout_count;
 436                 ++is;
 437         }
 438
 439         /*
 440          * If we exhausted our forward scan, continue with the reverse scan
 441          * when possible, even past an alignment boundary.  This catches
 442          * boundary conditions.
 443          */
 444         if (ib != 0 && pageout_count < vm_pageout_page_count)
 445                 goto more;
 446
 447         return (vm_pageout_flush(&mc[page_base], pageout_count,
 448             VM_PAGER_PUT_NOREUSE, 0, NULL, NULL));
 449 }
 450
 451 /*
 452  * vm_pageout_flush() - launder the given pages
 453  *
 454  *      The given pages are laundered.  Note that we setup for the start of
 455  *      I/O ( i.e. busy the page ), mark it read-only, and bump the object
 456  *      reference count all in here rather then in the parent.  If we want
 457  *      the parent to do more sophisticated things we may have to change
 458  *      the ordering.
 459  *
 460  *      Returned runlen is the count of pages between mreq and first
 461  *      page after mreq with status VM_PAGER_AGAIN.
 462  *      *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
 463  *      for any page in runlen set.
 464  */
 465 int
 466 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
 467     boolean_t *eio)
 468 {
 469         vm_object_t object = mc[0]->object;
 470         int pageout_status[count];
 471         int numpagedout = 0;
 472         int i, runlen;
 473
 474         VM_OBJECT_ASSERT_WLOCKED(object);
 475
 476         /*
 477          * Initiate I/O.  Mark the pages busy and verify that they're valid
 478          * and read-only.
 479          *
 480          * We do not have to fixup the clean/dirty bits here... we can
 481          * allow the pager to do it after the I/O completes.
 482          *
 483          * NOTE! mc[i]->dirty may be partial or fragmented due to an
 484          * edge case with file fragments.
 485          */
 486         for (i = 0; i < count; i++) {
 487                 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
 488                     ("vm_pageout_flush: partially invalid page %p index %d/%d",
 489                         mc[i], i, count));
 490                 KASSERT((mc[i]->aflags & PGA_WRITEABLE) == 0,
 491                     ("vm_pageout_flush: writeable page %p", mc[i]));
 492                 vm_page_sbusy(mc[i]);
 493         }
 494         vm_object_pip_add(object, count);
 495
 496         vm_pager_put_pages(object, mc, count, flags, pageout_status);
 497
 498         runlen = count - mreq;
 499         if (eio != NULL)
 500                 *eio = FALSE;
 501         for (i = 0; i < count; i++) {
 502                 vm_page_t mt = mc[i];
 503
 504                 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
 505                     !pmap_page_is_write_mapped(mt),
 506                     ("vm_pageout_flush: page %p is not write protected", mt));
 507                 switch (pageout_status[i]) {
 508                 case VM_PAGER_OK:
 509                         vm_page_lock(mt);
 510                         if (vm_page_in_laundry(mt))
 511                                 vm_page_deactivate_noreuse(mt);
 512                         vm_page_unlock(mt);
 513                         /* FALLTHROUGH */
 514                 case VM_PAGER_PEND:
 515                         numpagedout++;
 516                         break;
 517                 case VM_PAGER_BAD:
 518                         /*
 519                          * The page is outside the object's range.  We pretend
 520                          * that the page out worked and clean the page, so the
 521                          * changes will be lost if the page is reclaimed by
 522                          * the page daemon.
 523                          */
 524                         vm_page_undirty(mt);
 525                         vm_page_lock(mt);
 526                         if (vm_page_in_laundry(mt))
 527                                 vm_page_deactivate_noreuse(mt);
 528                         vm_page_unlock(mt);
 529                         break;
 530                 case VM_PAGER_ERROR:
 531                 case VM_PAGER_FAIL:
 532                         /*
 533                          * If the page couldn't be paged out to swap because the
 534                          * pager wasn't able to find space, place the page in
 535                          * the PQ_UNSWAPPABLE holding queue.  This is an
 536                          * optimization that prevents the page daemon from
 537                          * wasting CPU cycles on pages that cannot be reclaimed
 538                          * becase no swap device is configured.
 539                          *
 540                          * Otherwise, reactivate the page so that it doesn't
 541                          * clog the laundry and inactive queues.  (We will try
 542                          * paging it out again later.)
 543                          */
 544                         vm_page_lock(mt);
 545                         if (object->type == OBJT_SWAP &&
 546                             pageout_status[i] == VM_PAGER_FAIL) {
 547                                 vm_page_unswappable(mt);
 548                                 numpagedout++;
 549                         } else
 550                                 vm_page_activate(mt);
 551                         vm_page_unlock(mt);
 552                         if (eio != NULL && i >= mreq && i - mreq < runlen)
 553                                 *eio = TRUE;
 554                         break;
 555                 case VM_PAGER_AGAIN:
 556                         if (i >= mreq && i - mreq < runlen)
 557                                 runlen = i - mreq;
 558                         break;
 559                 }
 560
 561                 /*
 562                  * If the operation is still going, leave the page busy to
 563                  * block all other accesses. Also, leave the paging in
 564                  * progress indicator set so that we don't attempt an object
 565                  * collapse.
 566                  */
 567                 if (pageout_status[i] != VM_PAGER_PEND) {
 568                         vm_object_pip_wakeup(object);
 569                         vm_page_sunbusy(mt);
 570                 }
 571         }
 572         if (prunlen != NULL)
 573                 *prunlen = runlen;
 574         return (numpagedout);
 575 }
 576
 577 static void
 578 vm_pageout_swapon(void *arg __unused, struct swdevt *sp __unused)
 579 {
 580
 581         atomic_store_rel_int(&swapdev_enabled, 1);
 582 }
 583
 584 static void
 585 vm_pageout_swapoff(void *arg __unused, struct swdevt *sp __unused)
 586 {
 587
 588         if (swap_pager_nswapdev() == 1)
 589                 atomic_store_rel_int(&swapdev_enabled, 0);
 590 }
 591
 592 /*
 593  * Attempt to acquire all of the necessary locks to launder a page and
 594  * then call through the clustering layer to PUTPAGES.  Wait a short
 595  * time for a vnode lock.
 596  *
 597  * Requires the page and object lock on entry, releases both before return.
 598  * Returns 0 on success and an errno otherwise.
 599  */
 600 static int
 601 vm_pageout_clean(vm_page_t m, int *numpagedout)
 602 {
 603         struct vnode *vp;
 604         struct mount *mp;
 605         vm_object_t object;
 606         vm_pindex_t pindex;
 607         int error, lockmode;
 608
 609         vm_page_assert_locked(m);
 610         object = m->object;
 611         VM_OBJECT_ASSERT_WLOCKED(object);
 612         error = 0;
 613         vp = NULL;
 614         mp = NULL;
 615
 616         /*
 617          * The object is already known NOT to be dead.   It
 618          * is possible for the vget() to block the whole
 619          * pageout daemon, but the new low-memory handling
 620          * code should prevent it.
 621          *
 622          * We can't wait forever for the vnode lock, we might
 623          * deadlock due to a vn_read() getting stuck in
 624          * vm_wait while holding this vnode.  We skip the
 625          * vnode if we can't get it in a reasonable amount
 626          * of time.
 627          */
 628         if (object->type == OBJT_VNODE) {
 629                 vm_page_unlock(m);
 630                 vp = object->handle;
 631                 if (vp->v_type == VREG &&
 632                     vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 633                         mp = NULL;
 634                         error = EDEADLK;
 635                         goto unlock_all;
 636                 }
 637                 KASSERT(mp != NULL,
 638                     ("vp %p with NULL v_mount", vp));
 639                 vm_object_reference_locked(object);
 640                 pindex = m->pindex;
 641                 VM_OBJECT_WUNLOCK(object);
 642                 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
 643                     LK_SHARED : LK_EXCLUSIVE;
 644                 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
 645                         vp = NULL;
 646                         error = EDEADLK;
 647                         goto unlock_mp;
 648                 }
 649                 VM_OBJECT_WLOCK(object);
 650
 651                 /*
 652                  * Ensure that the object and vnode were not disassociated
 653                  * while locks were dropped.
 654                  */
 655                 if (vp->v_object != object) {
 656                         error = ENOENT;
 657                         goto unlock_all;
 658                 }
 659                 vm_page_lock(m);
 660
 661                 /*
 662                  * While the object and page were unlocked, the page
 663                  * may have been:
 664                  * (1) moved to a different queue,
 665                  * (2) reallocated to a different object,
 666                  * (3) reallocated to a different offset, or
 667                  * (4) cleaned.
 668                  */
 669                 if (!vm_page_in_laundry(m) || m->object != object ||
 670                     m->pindex != pindex || m->dirty == 0) {
 671                         vm_page_unlock(m);
 672                         error = ENXIO;
 673                         goto unlock_all;
 674                 }
 675
 676                 /*
 677                  * The page may have been busied or held while the object
 678                  * and page locks were released.
 679                  */
 680                 if (vm_page_busied(m) || m->hold_count != 0) {
 681                         vm_page_unlock(m);
 682                         error = EBUSY;
 683                         goto unlock_all;
 684                 }
 685         }
 686
 687         /*
 688          * If a page is dirty, then it is either being washed
 689          * (but not yet cleaned) or it is still in the
 690          * laundry.  If it is still in the laundry, then we
 691          * start the cleaning operation.
 692          */
 693         if ((*numpagedout = vm_pageout_cluster(m)) == 0)
 694                 error = EIO;
 695
 696 unlock_all:
 697         VM_OBJECT_WUNLOCK(object);
 698
 699 unlock_mp:
 700         vm_page_lock_assert(m, MA_NOTOWNED);
 701         if (mp != NULL) {
 702                 if (vp != NULL)
 703                         vput(vp);
 704                 vm_object_deallocate(object);
 705                 vn_finished_write(mp);
 706         }
 707
 708         return (error);
 709 }
 710
 711 /*
 712  * Attempt to launder the specified number of pages.
 713  *
 714  * Returns the number of pages successfully laundered.
 715  */
 716 static int
 717 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall)
 718 {
 719         struct vm_pagequeue *pq;
 720         vm_object_t object;
 721         vm_page_t m, next;
 722         int act_delta, error, maxscan, numpagedout, starting_target;
 723         int vnodes_skipped;
 724         bool pageout_ok, queue_locked;
 725
 726         starting_target = launder;
 727         vnodes_skipped = 0;
 728
 729         /*
 730          * Scan the laundry queues for pages eligible to be laundered.  We stop
 731          * once the target number of dirty pages have been laundered, or once
 732          * we've reached the end of the queue.  A single iteration of this loop
 733          * may cause more than one page to be laundered because of clustering.
 734          *
 735          * maxscan ensures that we don't re-examine requeued pages.  Any
 736          * additional pages written as part of a cluster are subtracted from
 737          * maxscan since they must be taken from the laundry queue.
 738          *
 739          * As an optimization, we avoid laundering from PQ_UNSWAPPABLE when no
 740          * swap devices are configured.
 741          */
 742         if (atomic_load_acq_int(&swapdev_enabled))
 743                 pq = &vmd->vmd_pagequeues[PQ_UNSWAPPABLE];
 744         else
 745                 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
 746
 747 scan:
 748         vm_pagequeue_lock(pq);
 749         maxscan = pq->pq_cnt;
 750         queue_locked = true;
 751         for (m = TAILQ_FIRST(&pq->pq_pl);
 752             m != NULL && maxscan-- > 0 && launder > 0;
 753             m = next) {
 754                 vm_pagequeue_assert_locked(pq);
 755                 KASSERT(queue_locked, ("unlocked laundry queue"));
 756                 KASSERT(vm_page_in_laundry(m),
 757                     ("page %p has an inconsistent queue", m));
 758                 next = TAILQ_NEXT(m, plinks.q);
 759                 if ((m->flags & PG_MARKER) != 0)
 760                         continue;
 761                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 762                     ("PG_FICTITIOUS page %p cannot be in laundry queue", m));
 763                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 764                     ("VPO_UNMANAGED page %p cannot be in laundry queue", m));
 765                 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
 766                         vm_page_unlock(m);
 767                         continue;
 768                 }
 769                 object = m->object;
 770                 if ((!VM_OBJECT_TRYWLOCK(object) &&
 771                     (!vm_pageout_fallback_object_lock(m, &next) ||
 772                     m->hold_count != 0)) || vm_page_busied(m)) {
 773                         VM_OBJECT_WUNLOCK(object);
 774                         vm_page_unlock(m);
 775                         continue;
 776                 }
 777
 778                 /*
 779                  * Unlock the laundry queue, invalidating the 'next' pointer.
 780                  * Use a marker to remember our place in the laundry queue.
 781                  */
 782                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_laundry_marker,
 783                     plinks.q);
 784                 vm_pagequeue_unlock(pq);
 785                 queue_locked = false;
 786
 787                 /*
 788                  * Invalid pages can be easily freed.  They cannot be
 789                  * mapped; vm_page_free() asserts this.
 790                  */
 791                 if (m->valid == 0)
 792                         goto free_page;
 793
 794                 /*
 795                  * If the page has been referenced and the object is not dead,
 796                  * reactivate or requeue the page depending on whether the
 797                  * object is mapped.
 798                  */
 799                 if ((m->aflags & PGA_REFERENCED) != 0) {
 800                         vm_page_aflag_clear(m, PGA_REFERENCED);
 801                         act_delta = 1;
 802                 } else
 803                         act_delta = 0;
 804                 if (object->ref_count != 0)
 805                         act_delta += pmap_ts_referenced(m);
 806                 else {
 807                         KASSERT(!pmap_page_is_mapped(m),
 808                             ("page %p is mapped", m));
 809                 }
 810                 if (act_delta != 0) {
 811                         if (object->ref_count != 0) {
 812                                 VM_CNT_INC(v_reactivated);
 813                                 vm_page_activate(m);
 814
 815                                 /*
 816                                  * Increase the activation count if the page
 817                                  * was referenced while in the laundry queue.
 818                                  * This makes it less likely that the page will
 819                                  * be returned prematurely to the inactive
 820                                  * queue.
 821                                  */
 822                                 m->act_count += act_delta + ACT_ADVANCE;
 823
 824                                 /*
 825                                  * If this was a background laundering, count
 826                                  * activated pages towards our target.  The
 827                                  * purpose of background laundering is to ensure
 828                                  * that pages are eventually cycled through the
 829                                  * laundry queue, and an activation is a valid
 830                                  * way out.
 831                                  */
 832                                 if (!in_shortfall)
 833                                         launder--;
 834                                 goto drop_page;
 835                         } else if ((object->flags & OBJ_DEAD) == 0)
 836                                 goto requeue_page;
 837                 }
 838
 839                 /*
 840                  * If the page appears to be clean at the machine-independent
 841                  * layer, then remove all of its mappings from the pmap in
 842                  * anticipation of freeing it.  If, however, any of the page's
 843                  * mappings allow write access, then the page may still be
 844                  * modified until the last of those mappings are removed.
 845                  */
 846                 if (object->ref_count != 0) {
 847                         vm_page_test_dirty(m);
 848                         if (m->dirty == 0)
 849                                 pmap_remove_all(m);
 850                 }
 851
 852                 /*
 853                  * Clean pages are freed, and dirty pages are paged out unless
 854                  * they belong to a dead object.  Requeueing dirty pages from
 855                  * dead objects is pointless, as they are being paged out and
 856                  * freed by the thread that destroyed the object.
 857                  */
 858                 if (m->dirty == 0) {
 859 free_page:
 860                         vm_page_free(m);
 861                         VM_CNT_INC(v_dfree);
 862                 } else if ((object->flags & OBJ_DEAD) == 0) {
 863                         if (object->type != OBJT_SWAP &&
 864                             object->type != OBJT_DEFAULT)
 865                                 pageout_ok = true;
 866                         else if (disable_swap_pageouts)
 867                                 pageout_ok = false;
 868                         else
 869                                 pageout_ok = true;
 870                         if (!pageout_ok) {
 871 requeue_page:
 872                                 vm_pagequeue_lock(pq);
 873                                 queue_locked = true;
 874                                 vm_page_requeue_locked(m);
 875                                 goto drop_page;
 876                         }
 877
 878                         /*
 879                          * Form a cluster with adjacent, dirty pages from the
 880                          * same object, and page out that entire cluster.
 881                          *
 882                          * The adjacent, dirty pages must also be in the
 883                          * laundry.  However, their mappings are not checked
 884                          * for new references.  Consequently, a recently
 885                          * referenced page may be paged out.  However, that
 886                          * page will not be prematurely reclaimed.  After page
 887                          * out, the page will be placed in the inactive queue,
 888                          * where any new references will be detected and the
 889                          * page reactivated.
 890                          */
 891                         error = vm_pageout_clean(m, &numpagedout);
 892                         if (error == 0) {
 893                                 launder -= numpagedout;
 894                                 maxscan -= numpagedout - 1;
 895                         } else if (error == EDEADLK) {
 896                                 pageout_lock_miss++;
 897                                 vnodes_skipped++;
 898                         }
 899                         goto relock_queue;
 900                 }
 901 drop_page:
 902                 vm_page_unlock(m);
 903                 VM_OBJECT_WUNLOCK(object);
 904 relock_queue:
 905                 if (!queue_locked) {
 906                         vm_pagequeue_lock(pq);
 907                         queue_locked = true;
 908                 }
 909                 next = TAILQ_NEXT(&vmd->vmd_laundry_marker, plinks.q);
 910                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_laundry_marker, plinks.q);
 911         }
 912         vm_pagequeue_unlock(pq);
 913
 914         if (launder > 0 && pq == &vmd->vmd_pagequeues[PQ_UNSWAPPABLE]) {
 915                 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
 916                 goto scan;
 917         }
 918
 919         /*
 920          * Wakeup the sync daemon if we skipped a vnode in a writeable object
 921          * and we didn't launder enough pages.
 922          */
 923         if (vnodes_skipped > 0 && launder > 0)
 924                 (void)speedup_syncer();
 925
 926         return (starting_target - launder);
 927 }
 928
 929 /*
 930  * Compute the integer square root.
 931  */
 932 static u_int
 933 isqrt(u_int num)
 934 {
 935         u_int bit, root, tmp;
 936
 937         bit = 1u << ((NBBY * sizeof(u_int)) - 2);
 938         while (bit > num)
 939                 bit >>= 2;
 940         root = 0;
 941         while (bit != 0) {
 942                 tmp = root + bit;
 943                 root >>= 1;
 944                 if (num >= tmp) {
 945                         num -= tmp;
 946                         root += bit;
 947                 }
 948                 bit >>= 2;
 949         }
 950         return (root);
 951 }
 952
 953 /*
 954  * Perform the work of the laundry thread: periodically wake up and determine
 955  * whether any pages need to be laundered.  If so, determine the number of pages
 956  * that need to be laundered, and launder them.
 957  */
 958 static void
 959 vm_pageout_laundry_worker(void *arg)
 960 {
 961         struct vm_domain *domain;
 962         struct vm_pagequeue *pq;
 963         uint64_t nclean, ndirty;
 964         u_int last_launder, wakeups;
 965         int domidx, last_target, launder, shortfall, shortfall_cycle, target;
 966         bool in_shortfall;
 967
 968         domidx = (uintptr_t)arg;
 969         domain = &vm_dom[domidx];
 970         pq = &domain->vmd_pagequeues[PQ_LAUNDRY];
 971         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
 972         vm_pageout_init_marker(&domain->vmd_laundry_marker, PQ_LAUNDRY);
 973
 974         shortfall = 0;
 975         in_shortfall = false;
 976         shortfall_cycle = 0;
 977         target = 0;
 978         last_launder = 0;
 979
 980         /*
 981          * Calls to these handlers are serialized by the swap syscall lock.
 982          */
 983         (void)EVENTHANDLER_REGISTER(swapon, vm_pageout_swapon, domain,
 984             EVENTHANDLER_PRI_ANY);
 985         (void)EVENTHANDLER_REGISTER(swapoff, vm_pageout_swapoff, domain,
 986             EVENTHANDLER_PRI_ANY);
 987
 988         /*
 989          * The pageout laundry worker is never done, so loop forever.
 990          */
 991         for (;;) {
 992                 KASSERT(target >= 0, ("negative target %d", target));
 993                 KASSERT(shortfall_cycle >= 0,
 994                     ("negative cycle %d", shortfall_cycle));
 995                 launder = 0;
 996                 wakeups = VM_CNT_FETCH(v_pdwakeups);
 997
 998                 /*
 999                  * First determine whether we need to launder pages to meet a
1000                  * shortage of free pages.
1001                  */
1002                 if (shortfall > 0) {
1003                         in_shortfall = true;
1004                         shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE;
1005                         target = shortfall;
1006                 } else if (!in_shortfall)
1007                         goto trybackground;
1008                 else if (shortfall_cycle == 0 || vm_laundry_target() <= 0) {
1009                         /*
1010                          * We recently entered shortfall and began laundering
1011                          * pages.  If we have completed that laundering run
1012                          * (and we are no longer in shortfall) or we have met
1013                          * our laundry target through other activity, then we
1014                          * can stop laundering pages.
1015                          */
1016                         in_shortfall = false;
1017                         target = 0;
1018                         goto trybackground;
1019                 }
1020                 last_launder = wakeups;
1021                 launder = target / shortfall_cycle--;
1022                 goto dolaundry;
1023
1024                 /*
1025                  * There's no immediate need to launder any pages; see if we
1026                  * meet the conditions to perform background laundering:
1027                  *
1028                  * 1. The ratio of dirty to clean inactive pages exceeds the
1029                  *    background laundering threshold and the pagedaemon has
1030                  *    been woken up to reclaim pages since our last
1031                  *    laundering, or
1032                  * 2. we haven't yet reached the target of the current
1033                  *    background laundering run.
1034                  *
1035                  * The background laundering threshold is not a constant.
1036                  * Instead, it is a slowly growing function of the number of
1037                  * page daemon wakeups since the last laundering.  Thus, as the
1038                  * ratio of dirty to clean inactive pages grows, the amount of
1039                  * memory pressure required to trigger laundering decreases.
1040                  */
1041 trybackground:
1042                 nclean = vm_cnt.v_inactive_count + vm_cnt.v_free_count;
1043                 ndirty = vm_cnt.v_laundry_count;
1044                 if (target == 0 && wakeups != last_launder &&
1045                     ndirty * isqrt(wakeups - last_launder) >= nclean) {
1046                         target = vm_background_launder_target;
1047                 }
1048
1049                 /*
1050                  * We have a non-zero background laundering target.  If we've
1051                  * laundered up to our maximum without observing a page daemon
1052                  * wakeup, just stop.  This is a safety belt that ensures we
1053                  * don't launder an excessive amount if memory pressure is low
1054                  * and the ratio of dirty to clean pages is large.  Otherwise,
1055                  * proceed at the background laundering rate.
1056                  */
1057                 if (target > 0) {
1058                         if (wakeups != last_launder) {
1059                                 last_launder = wakeups;
1060                                 last_target = target;
1061                         } else if (last_target - target >=
1062                             vm_background_launder_max * PAGE_SIZE / 1024) {
1063                                 target = 0;
1064                         }
1065                         launder = vm_background_launder_rate * PAGE_SIZE / 1024;
1066                         launder /= VM_LAUNDER_RATE;
1067                         if (launder > target)
1068                                 launder = target;
1069                 }
1070
1071 dolaundry:
1072                 if (launder > 0) {
1073                         /*
1074                          * Because of I/O clustering, the number of laundered
1075                          * pages could exceed "target" by the maximum size of
1076                          * a cluster minus one.
1077                          */
1078                         target -= min(vm_pageout_launder(domain, launder,
1079                             in_shortfall), target);
1080                         pause("laundp", hz / VM_LAUNDER_RATE);
1081                 }
1082
1083                 /*
1084                  * If we're not currently laundering pages and the page daemon
1085                  * hasn't posted a new request, sleep until the page daemon
1086                  * kicks us.
1087                  */
1088                 vm_pagequeue_lock(pq);
1089                 if (target == 0 && vm_laundry_request == VM_LAUNDRY_IDLE)
1090                         (void)mtx_sleep(&vm_laundry_request,
1091                             vm_pagequeue_lockptr(pq), PVM, "launds", 0);
1092
1093                 /*
1094                  * If the pagedaemon has indicated that it's in shortfall, start
1095                  * a shortfall laundering unless we're already in the middle of
1096                  * one.  This may preempt a background laundering.
1097                  */
1098                 if (vm_laundry_request == VM_LAUNDRY_SHORTFALL &&
1099                     (!in_shortfall || shortfall_cycle == 0)) {
1100                         shortfall = vm_laundry_target() + vm_pageout_deficit;
1101                         target = 0;
1102                 } else
1103                         shortfall = 0;
1104
1105                 if (target == 0)
1106                         vm_laundry_request = VM_LAUNDRY_IDLE;
1107                 vm_pagequeue_unlock(pq);
1108         }
1109 }
1110
1111 /*
1112  *      vm_pageout_scan does the dirty work for the pageout daemon.
1113  *
1114  *      pass == 0: Update active LRU/deactivate pages
1115  *      pass >= 1: Free inactive pages
1116  *
1117  * Returns true if pass was zero or enough pages were freed by the inactive
1118  * queue scan to meet the target.
1119  */
1120 static bool
1121 vm_pageout_scan(struct vm_domain *vmd, int pass)
1122 {
1123         vm_page_t m, next;
1124         struct vm_pagequeue *pq;
1125         vm_object_t object;
1126         long min_scan;
1127         int act_delta, addl_page_shortage, deficit, inactq_shortage, maxscan;
1128         int page_shortage, scan_tick, scanned, starting_page_shortage;
1129         boolean_t queue_locked;
1130
1131         /*
1132          * If we need to reclaim memory ask kernel caches to return
1133          * some.  We rate limit to avoid thrashing.
1134          */
1135         if (vmd == &vm_dom[0] && pass > 0 &&
1136             (time_uptime - lowmem_uptime) >= lowmem_period) {
1137                 /*
1138                  * Decrease registered cache sizes.
1139                  */
1140                 SDT_PROBE0(vm, , , vm__lowmem_scan);
1141                 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES);
1142                 /*
1143                  * We do this explicitly after the caches have been
1144                  * drained above.
1145                  */
1146                 uma_reclaim();
1147                 lowmem_uptime = time_uptime;
1148         }
1149
1150         /*
1151          * The addl_page_shortage is the number of temporarily
1152          * stuck pages in the inactive queue.  In other words, the
1153          * number of pages from the inactive count that should be
1154          * discounted in setting the target for the active queue scan.
1155          */
1156         addl_page_shortage = 0;
1157
1158         /*
1159          * Calculate the number of pages that we want to free.  This number
1160          * can be negative if many pages are freed between the wakeup call to
1161          * the page daemon and this calculation.
1162          */
1163         if (pass > 0) {
1164                 deficit = atomic_readandclear_int(&vm_pageout_deficit);
1165                 page_shortage = vm_paging_target() + deficit;
1166         } else
1167                 page_shortage = deficit = 0;
1168         starting_page_shortage = page_shortage;
1169
1170         /*
1171          * Start scanning the inactive queue for pages that we can free.  The
1172          * scan will stop when we reach the target or we have scanned the
1173          * entire queue.  (Note that m->act_count is not used to make
1174          * decisions for the inactive queue, only for the active queue.)
1175          */
1176         pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
1177         maxscan = pq->pq_cnt;
1178         vm_pagequeue_lock(pq);
1179         queue_locked = TRUE;
1180         for (m = TAILQ_FIRST(&pq->pq_pl);
1181              m != NULL && maxscan-- > 0 && page_shortage > 0;
1182              m = next) {
1183                 vm_pagequeue_assert_locked(pq);
1184                 KASSERT(queue_locked, ("unlocked inactive queue"));
1185                 KASSERT(vm_page_inactive(m), ("Inactive queue %p", m));
1186
1187                 VM_CNT_INC(v_pdpages);
1188                 next = TAILQ_NEXT(m, plinks.q);
1189
1190                 /*
1191                  * skip marker pages
1192                  */
1193                 if (m->flags & PG_MARKER)
1194                         continue;
1195
1196                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1197                     ("Fictitious page %p cannot be in inactive queue", m));
1198                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1199                     ("Unmanaged page %p cannot be in inactive queue", m));
1200
1201                 /*
1202                  * The page or object lock acquisitions fail if the
1203                  * page was removed from the queue or moved to a
1204                  * different position within the queue.  In either
1205                  * case, addl_page_shortage should not be incremented.
1206                  */
1207                 if (!vm_pageout_page_lock(m, &next))
1208                         goto unlock_page;
1209                 else if (m->hold_count != 0) {
1210                         /*
1211                          * Held pages are essentially stuck in the
1212                          * queue.  So, they ought to be discounted
1213                          * from the inactive count.  See the
1214                          * calculation of inactq_shortage before the
1215                          * loop over the active queue below.
1216                          */
1217                         addl_page_shortage++;
1218                         goto unlock_page;
1219                 }
1220                 object = m->object;
1221                 if (!VM_OBJECT_TRYWLOCK(object)) {
1222                         if (!vm_pageout_fallback_object_lock(m, &next))
1223                                 goto unlock_object;
1224                         else if (m->hold_count != 0) {
1225                                 addl_page_shortage++;
1226                                 goto unlock_object;
1227                         }
1228                 }
1229                 if (vm_page_busied(m)) {
1230                         /*
1231                          * Don't mess with busy pages.  Leave them at
1232                          * the front of the queue.  Most likely, they
1233                          * are being paged out and will leave the
1234                          * queue shortly after the scan finishes.  So,
1235                          * they ought to be discounted from the
1236                          * inactive count.
1237                          */
1238                         addl_page_shortage++;
1239 unlock_object:
1240                         VM_OBJECT_WUNLOCK(object);
1241 unlock_page:
1242                         vm_page_unlock(m);
1243                         continue;
1244                 }
1245                 KASSERT(m->hold_count == 0, ("Held page %p", m));
1246
1247                 /*
1248                  * Dequeue the inactive page and unlock the inactive page
1249                  * queue, invalidating the 'next' pointer.  Dequeueing the
1250                  * page here avoids a later reacquisition (and release) of
1251                  * the inactive page queue lock when vm_page_activate(),
1252                  * vm_page_free(), or vm_page_launder() is called.  Use a
1253                  * marker to remember our place in the inactive queue.
1254                  */
1255                 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
1256                 vm_page_dequeue_locked(m);
1257                 vm_pagequeue_unlock(pq);
1258                 queue_locked = FALSE;
1259
1260                 /*
1261                  * Invalid pages can be easily freed. They cannot be
1262                  * mapped, vm_page_free() asserts this.
1263                  */
1264                 if (m->valid == 0)
1265                         goto free_page;
1266
1267                 /*
1268                  * If the page has been referenced and the object is not dead,
1269                  * reactivate or requeue the page depending on whether the
1270                  * object is mapped.
1271                  */
1272                 if ((m->aflags & PGA_REFERENCED) != 0) {
1273                         vm_page_aflag_clear(m, PGA_REFERENCED);
1274                         act_delta = 1;
1275                 } else
1276                         act_delta = 0;
1277                 if (object->ref_count != 0) {
1278                         act_delta += pmap_ts_referenced(m);
1279                 } else {
1280                         KASSERT(!pmap_page_is_mapped(m),
1281                             ("vm_pageout_scan: page %p is mapped", m));
1282                 }
1283                 if (act_delta != 0) {
1284                         if (object->ref_count != 0) {
1285                                 VM_CNT_INC(v_reactivated);
1286                                 vm_page_activate(m);
1287
1288                                 /*
1289                                  * Increase the activation count if the page
1290                                  * was referenced while in the inactive queue.
1291                                  * This makes it less likely that the page will
1292                                  * be returned prematurely to the inactive
1293                                  * queue.
1294                                  */
1295                                 m->act_count += act_delta + ACT_ADVANCE;
1296                                 goto drop_page;
1297                         } else if ((object->flags & OBJ_DEAD) == 0) {
1298                                 vm_pagequeue_lock(pq);
1299                                 queue_locked = TRUE;
1300                                 m->queue = PQ_INACTIVE;
1301                                 TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
1302                                 vm_pagequeue_cnt_inc(pq);
1303                                 goto drop_page;
1304                         }
1305                 }
1306
1307                 /*
1308                  * If the page appears to be clean at the machine-independent
1309                  * layer, then remove all of its mappings from the pmap in
1310                  * anticipation of freeing it.  If, however, any of the page's
1311                  * mappings allow write access, then the page may still be
1312                  * modified until the last of those mappings are removed.
1313                  */
1314                 if (object->ref_count != 0) {
1315                         vm_page_test_dirty(m);
1316                         if (m->dirty == 0)
1317                                 pmap_remove_all(m);
1318                 }
1319
1320                 /*
1321                  * Clean pages can be freed, but dirty pages must be sent back
1322                  * to the laundry, unless they belong to a dead object.
1323                  * Requeueing dirty pages from dead objects is pointless, as
1324                  * they are being paged out and freed by the thread that
1325                  * destroyed the object.
1326                  */
1327                 if (m->dirty == 0) {
1328 free_page:
1329                         vm_page_free(m);
1330                         VM_CNT_INC(v_dfree);
1331                         --page_shortage;
1332                 } else if ((object->flags & OBJ_DEAD) == 0)
1333                         vm_page_launder(m);
1334 drop_page:
1335                 vm_page_unlock(m);
1336                 VM_OBJECT_WUNLOCK(object);
1337                 if (!queue_locked) {
1338                         vm_pagequeue_lock(pq);
1339                         queue_locked = TRUE;
1340                 }
1341                 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
1342                 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
1343         }
1344         vm_pagequeue_unlock(pq);
1345
1346         /*
1347          * Wake up the laundry thread so that it can perform any needed
1348          * laundering.  If we didn't meet our target, we're in shortfall and
1349          * need to launder more aggressively.  If PQ_LAUNDRY is empty and no
1350          * swap devices are configured, the laundry thread has no work to do, so
1351          * don't bother waking it up.
1352          */
1353         if (vm_laundry_request == VM_LAUNDRY_IDLE &&
1354             starting_page_shortage > 0) {
1355                 pq = &vm_dom[0].vmd_pagequeues[PQ_LAUNDRY];
1356                 vm_pagequeue_lock(pq);
1357                 if (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled)) {
1358                         if (page_shortage > 0) {
1359                                 vm_laundry_request = VM_LAUNDRY_SHORTFALL;
1360                                 VM_CNT_INC(v_pdshortfalls);
1361                         } else if (vm_laundry_request != VM_LAUNDRY_SHORTFALL)
1362                                 vm_laundry_request = VM_LAUNDRY_BACKGROUND;
1363                         wakeup(&vm_laundry_request);
1364                 }
1365                 vm_pagequeue_unlock(pq);
1366         }
1367
1368         /*
1369          * Wakeup the swapout daemon if we didn't free the targeted number of
1370          * pages.
1371          */
1372         if (page_shortage > 0)
1373                 vm_swapout_run();
1374
1375         /*
1376          * If the inactive queue scan fails repeatedly to meet its
1377          * target, kill the largest process.
1378          */
1379         vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage);
1380
1381         /*
1382          * Compute the number of pages we want to try to move from the
1383          * active queue to either the inactive or laundry queue.
1384          *
1385          * When scanning active pages, we make clean pages count more heavily
1386          * towards the page shortage than dirty pages.  This is because dirty
1387          * pages must be laundered before they can be reused and thus have less
1388          * utility when attempting to quickly alleviate a shortage.  However,
1389          * this weighting also causes the scan to deactivate dirty pages more
1390          * more aggressively, improving the effectiveness of clustering and
1391          * ensuring that they can eventually be reused.
1392          */
1393         inactq_shortage = vm_cnt.v_inactive_target - (vm_cnt.v_inactive_count +
1394             vm_cnt.v_laundry_count / act_scan_laundry_weight) +
1395             vm_paging_target() + deficit + addl_page_shortage;
1396         page_shortage *= act_scan_laundry_weight;
1397
1398         pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1399         vm_pagequeue_lock(pq);
1400         maxscan = pq->pq_cnt;
1401
1402         /*
1403          * If we're just idle polling attempt to visit every
1404          * active page within 'update_period' seconds.
1405          */
1406         scan_tick = ticks;
1407         if (vm_pageout_update_period != 0) {
1408                 min_scan = pq->pq_cnt;
1409                 min_scan *= scan_tick - vmd->vmd_last_active_scan;
1410                 min_scan /= hz * vm_pageout_update_period;
1411         } else
1412                 min_scan = 0;
1413         if (min_scan > 0 || (inactq_shortage > 0 && maxscan > 0))
1414                 vmd->vmd_last_active_scan = scan_tick;
1415
1416         /*
1417          * Scan the active queue for pages that can be deactivated.  Update
1418          * the per-page activity counter and use it to identify deactivation
1419          * candidates.  Held pages may be deactivated.
1420          */
1421         for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned <
1422             min_scan || (inactq_shortage > 0 && scanned < maxscan)); m = next,
1423             scanned++) {
1424                 KASSERT(m->queue == PQ_ACTIVE,
1425                     ("vm_pageout_scan: page %p isn't active", m));
1426                 next = TAILQ_NEXT(m, plinks.q);
1427                 if ((m->flags & PG_MARKER) != 0)
1428                         continue;
1429                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1430                     ("Fictitious page %p cannot be in active queue", m));
1431                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1432                     ("Unmanaged page %p cannot be in active queue", m));
1433                 if (!vm_pageout_page_lock(m, &next)) {
1434                         vm_page_unlock(m);
1435                         continue;
1436                 }
1437
1438                 /*
1439                  * The count for page daemon pages is updated after checking
1440                  * the page for eligibility.
1441                  */
1442                 VM_CNT_INC(v_pdpages);
1443
1444                 /*
1445                  * Check to see "how much" the page has been used.
1446                  */
1447                 if ((m->aflags & PGA_REFERENCED) != 0) {
1448                         vm_page_aflag_clear(m, PGA_REFERENCED);
1449                         act_delta = 1;
1450                 } else
1451                         act_delta = 0;
1452
1453                 /*
1454                  * Perform an unsynchronized object ref count check.  While
1455                  * the page lock ensures that the page is not reallocated to
1456                  * another object, in particular, one with unmanaged mappings
1457                  * that cannot support pmap_ts_referenced(), two races are,
1458                  * nonetheless, possible:
1459                  * 1) The count was transitioning to zero, but we saw a non-
1460                  *    zero value.  pmap_ts_referenced() will return zero
1461                  *    because the page is not mapped.
1462                  * 2) The count was transitioning to one, but we saw zero.
1463                  *    This race delays the detection of a new reference.  At
1464                  *    worst, we will deactivate and reactivate the page.
1465                  */
1466                 if (m->object->ref_count != 0)
1467                         act_delta += pmap_ts_referenced(m);
1468
1469                 /*
1470                  * Advance or decay the act_count based on recent usage.
1471                  */
1472                 if (act_delta != 0) {
1473                         m->act_count += ACT_ADVANCE + act_delta;
1474                         if (m->act_count > ACT_MAX)
1475                                 m->act_count = ACT_MAX;
1476                 } else
1477                         m->act_count -= min(m->act_count, ACT_DECLINE);
1478
1479                 /*
1480                  * Move this page to the tail of the active, inactive or laundry
1481                  * queue depending on usage.
1482                  */
1483                 if (m->act_count == 0) {
1484                         /* Dequeue to avoid later lock recursion. */
1485                         vm_page_dequeue_locked(m);
1486
1487                         /*
1488                          * When not short for inactive pages, let dirty pages go
1489                          * through the inactive queue before moving to the
1490                          * laundry queues.  This gives them some extra time to
1491                          * be reactivated, potentially avoiding an expensive
1492                          * pageout.  During a page shortage, the inactive queue
1493                          * is necessarily small, so we may move dirty pages
1494                          * directly to the laundry queue.
1495                          */
1496                         if (inactq_shortage <= 0)
1497                                 vm_page_deactivate(m);
1498                         else {
1499                                 /*
1500                                  * Calling vm_page_test_dirty() here would
1501                                  * require acquisition of the object's write
1502                                  * lock.  However, during a page shortage,
1503                                  * directing dirty pages into the laundry
1504                                  * queue is only an optimization and not a
1505                                  * requirement.  Therefore, we simply rely on
1506                                  * the opportunistic updates to the page's
1507                                  * dirty field by the pmap.
1508                                  */
1509                                 if (m->dirty == 0) {
1510                                         vm_page_deactivate(m);
1511                                         inactq_shortage -=
1512                                             act_scan_laundry_weight;
1513                                 } else {
1514                                         vm_page_launder(m);
1515                                         inactq_shortage--;
1516                                 }
1517                         }
1518                 } else
1519                         vm_page_requeue_locked(m);
1520                 vm_page_unlock(m);
1521         }
1522         vm_pagequeue_unlock(pq);
1523         if (pass > 0)
1524                 vm_swapout_run_idle();
1525         return (page_shortage <= 0);
1526 }
1527
1528 static int vm_pageout_oom_vote;
1529
1530 /*
1531  * The pagedaemon threads randlomly select one to perform the
1532  * OOM.  Trying to kill processes before all pagedaemons
1533  * failed to reach free target is premature.
1534  */
1535 static void
1536 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
1537     int starting_page_shortage)
1538 {
1539         int old_vote;
1540
1541         if (starting_page_shortage <= 0 || starting_page_shortage !=
1542             page_shortage)
1543                 vmd->vmd_oom_seq = 0;
1544         else
1545                 vmd->vmd_oom_seq++;
1546         if (vmd->vmd_oom_seq < vm_pageout_oom_seq) {
1547                 if (vmd->vmd_oom) {
1548                         vmd->vmd_oom = FALSE;
1549                         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1550                 }
1551                 return;
1552         }
1553
1554         /*
1555          * Do not follow the call sequence until OOM condition is
1556          * cleared.
1557          */
1558         vmd->vmd_oom_seq = 0;
1559
1560         if (vmd->vmd_oom)
1561                 return;
1562
1563         vmd->vmd_oom = TRUE;
1564         old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1565         if (old_vote != vm_ndomains - 1)
1566                 return;
1567
1568         /*
1569          * The current pagedaemon thread is the last in the quorum to
1570          * start OOM.  Initiate the selection and signaling of the
1571          * victim.
1572          */
1573         vm_pageout_oom(VM_OOM_MEM);
1574
1575         /*
1576          * After one round of OOM terror, recall our vote.  On the
1577          * next pass, current pagedaemon would vote again if the low
1578          * memory condition is still there, due to vmd_oom being
1579          * false.
1580          */
1581         vmd->vmd_oom = FALSE;
1582         atomic_subtract_int(&vm_pageout_oom_vote, 1);
1583 }
1584
1585 /*
1586  * The OOM killer is the page daemon's action of last resort when
1587  * memory allocation requests have been stalled for a prolonged period
1588  * of time because it cannot reclaim memory.  This function computes
1589  * the approximate number of physical pages that could be reclaimed if
1590  * the specified address space is destroyed.
1591  *
1592  * Private, anonymous memory owned by the address space is the
1593  * principal resource that we expect to recover after an OOM kill.
1594  * Since the physical pages mapped by the address space's COW entries
1595  * are typically shared pages, they are unlikely to be released and so
1596  * they are not counted.
1597  *
1598  * To get to the point where the page daemon runs the OOM killer, its
1599  * efforts to write-back vnode-backed pages may have stalled.  This
1600  * could be caused by a memory allocation deadlock in the write path
1601  * that might be resolved by an OOM kill.  Therefore, physical pages
1602  * belonging to vnode-backed objects are counted, because they might
1603  * be freed without being written out first if the address space holds
1604  * the last reference to an unlinked vnode.
1605  *
1606  * Similarly, physical pages belonging to OBJT_PHYS objects are
1607  * counted because the address space might hold the last reference to
1608  * the object.
1609  */
1610 static long
1611 vm_pageout_oom_pagecount(struct vmspace *vmspace)
1612 {
1613         vm_map_t map;
1614         vm_map_entry_t entry;
1615         vm_object_t obj;
1616         long res;
1617
1618         map = &vmspace->vm_map;
1619         KASSERT(!map->system_map, ("system map"));
1620         sx_assert(&map->lock, SA_LOCKED);
1621         res = 0;
1622         for (entry = map->header.next; entry != &map->header;
1623             entry = entry->next) {
1624                 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
1625                         continue;
1626                 obj = entry->object.vm_object;
1627                 if (obj == NULL)
1628                         continue;
1629                 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 &&
1630                     obj->ref_count != 1)
1631                         continue;
1632                 switch (obj->type) {
1633                 case OBJT_DEFAULT:
1634                 case OBJT_SWAP:
1635                 case OBJT_PHYS:
1636                 case OBJT_VNODE:
1637                         res += obj->resident_page_count;
1638                         break;
1639                 }
1640         }
1641         return (res);
1642 }
1643
1644 void
1645 vm_pageout_oom(int shortage)
1646 {
1647         struct proc *p, *bigproc;
1648         vm_offset_t size, bigsize;
1649         struct thread *td;
1650         struct vmspace *vm;
1651         bool breakout;
1652
1653         /*
1654          * We keep the process bigproc locked once we find it to keep anyone
1655          * from messing with it; however, there is a possibility of
1656          * deadlock if process B is bigproc and one of its child processes
1657          * attempts to propagate a signal to B while we are waiting for A's
1658          * lock while walking this list.  To avoid this, we don't block on
1659          * the process lock but just skip a process if it is already locked.
1660          */
1661         bigproc = NULL;
1662         bigsize = 0;
1663         sx_slock(&allproc_lock);
1664         FOREACH_PROC_IN_SYSTEM(p) {
1665                 PROC_LOCK(p);
1666
1667                 /*
1668                  * If this is a system, protected or killed process, skip it.
1669                  */
1670                 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1671                     P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1672                     p->p_pid == 1 || P_KILLED(p) ||
1673                     (p->p_pid < 48 && swap_pager_avail != 0)) {
1674                         PROC_UNLOCK(p);
1675                         continue;
1676                 }
1677                 /*
1678                  * If the process is in a non-running type state,
1679                  * don't touch it.  Check all the threads individually.
1680                  */
1681                 breakout = false;
1682                 FOREACH_THREAD_IN_PROC(p, td) {
1683                         thread_lock(td);
1684                         if (!TD_ON_RUNQ(td) &&
1685                             !TD_IS_RUNNING(td) &&
1686                             !TD_IS_SLEEPING(td) &&
1687                             !TD_IS_SUSPENDED(td) &&
1688                             !TD_IS_SWAPPED(td)) {
1689                                 thread_unlock(td);
1690                                 breakout = true;
1691                                 break;
1692                         }
1693                         thread_unlock(td);
1694                 }
1695                 if (breakout) {
1696                         PROC_UNLOCK(p);
1697                         continue;
1698                 }
1699                 /*
1700                  * get the process size
1701                  */
1702                 vm = vmspace_acquire_ref(p);
1703                 if (vm == NULL) {
1704                         PROC_UNLOCK(p);
1705                         continue;
1706                 }
1707                 _PHOLD_LITE(p);
1708                 PROC_UNLOCK(p);
1709                 sx_sunlock(&allproc_lock);
1710                 if (!vm_map_trylock_read(&vm->vm_map)) {
1711                         vmspace_free(vm);
1712                         sx_slock(&allproc_lock);
1713                         PRELE(p);
1714                         continue;
1715                 }
1716                 size = vmspace_swap_count(vm);
1717                 if (shortage == VM_OOM_MEM)
1718                         size += vm_pageout_oom_pagecount(vm);
1719                 vm_map_unlock_read(&vm->vm_map);
1720                 vmspace_free(vm);
1721                 sx_slock(&allproc_lock);
1722
1723                 /*
1724                  * If this process is bigger than the biggest one,
1725                  * remember it.
1726                  */
1727                 if (size > bigsize) {
1728                         if (bigproc != NULL)
1729                                 PRELE(bigproc);
1730                         bigproc = p;
1731                         bigsize = size;
1732                 } else {
1733                         PRELE(p);
1734                 }
1735         }
1736         sx_sunlock(&allproc_lock);
1737         if (bigproc != NULL) {
1738                 if (vm_panic_on_oom != 0)
1739                         panic("out of swap space");
1740                 PROC_LOCK(bigproc);
1741                 killproc(bigproc, "out of swap space");
1742                 sched_nice(bigproc, PRIO_MIN);
1743                 _PRELE(bigproc);
1744                 PROC_UNLOCK(bigproc);
1745                 wakeup(&vm_cnt.v_free_count);
1746         }
1747 }
1748
1749 static void
1750 vm_pageout_worker(void *arg)
1751 {
1752         struct vm_domain *domain;
1753         int domidx, pass;
1754         bool target_met;
1755
1756         domidx = (uintptr_t)arg;
1757         domain = &vm_dom[domidx];
1758         pass = 0;
1759         target_met = true;
1760
1761         /*
1762          * XXXKIB It could be useful to bind pageout daemon threads to
1763          * the cores belonging to the domain, from which vm_page_array
1764          * is allocated.
1765          */
1766
1767         KASSERT(domain->vmd_segs != 0, ("domain without segments"));
1768         domain->vmd_last_active_scan = ticks;
1769         vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
1770         vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE);
1771         TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl,
1772             &domain->vmd_inacthead, plinks.q);
1773
1774         /*
1775          * The pageout daemon worker is never done, so loop forever.
1776          */
1777         while (TRUE) {
1778                 mtx_lock(&vm_page_queue_free_mtx);
1779
1780                 /*
1781                  * Generally, after a level >= 1 scan, if there are enough
1782                  * free pages to wakeup the waiters, then they are already
1783                  * awake.  A call to vm_page_free() during the scan awakened
1784                  * them.  However, in the following case, this wakeup serves
1785                  * to bound the amount of time that a thread might wait.
1786                  * Suppose a thread's call to vm_page_alloc() fails, but
1787                  * before that thread calls VM_WAIT, enough pages are freed by
1788                  * other threads to alleviate the free page shortage.  The
1789                  * thread will, nonetheless, wait until another page is freed
1790                  * or this wakeup is performed.
1791                  */
1792                 if (vm_pages_needed && !vm_page_count_min()) {
1793                         vm_pages_needed = false;
1794                         wakeup(&vm_cnt.v_free_count);
1795                 }
1796
1797                 /*
1798                  * Do not clear vm_pageout_wanted until we reach our free page
1799                  * target.  Otherwise, we may be awakened over and over again,
1800                  * wasting CPU time.
1801                  */
1802                 if (vm_pageout_wanted && target_met)
1803                         vm_pageout_wanted = false;
1804
1805                 /*
1806                  * Might the page daemon receive a wakeup call?
1807                  */
1808                 if (vm_pageout_wanted) {
1809                         /*
1810                          * No.  Either vm_pageout_wanted was set by another
1811                          * thread during the previous scan, which must have
1812                          * been a level 0 scan, or vm_pageout_wanted was
1813                          * already set and the scan failed to free enough
1814                          * pages.  If we haven't yet performed a level >= 1
1815                          * (page reclamation) scan, then increase the level
1816                          * and scan again now.  Otherwise, sleep a bit and
1817                          * try again later.
1818                          */
1819                         mtx_unlock(&vm_page_queue_free_mtx);
1820                         if (pass >= 1)
1821                                 pause("psleep", hz / VM_INACT_SCAN_RATE);
1822                         pass++;
1823                 } else {
1824                         /*
1825                          * Yes.  Sleep until pages need to be reclaimed or
1826                          * have their reference stats updated.
1827                          */
1828                         if (mtx_sleep(&vm_pageout_wanted,
1829                             &vm_page_queue_free_mtx, PDROP | PVM, "psleep",
1830                             hz) == 0) {
1831                                 VM_CNT_INC(v_pdwakeups);
1832                                 pass = 1;
1833                         } else
1834                                 pass = 0;
1835                 }
1836
1837                 target_met = vm_pageout_scan(domain, pass);
1838         }
1839 }
1840
1841 /*
1842  *      vm_pageout_init initialises basic pageout daemon settings.
1843  */
1844 static void
1845 vm_pageout_init(void)
1846 {
1847         /*
1848          * Initialize some paging parameters.
1849          */
1850         vm_cnt.v_interrupt_free_min = 2;
1851         if (vm_cnt.v_page_count < 2000)
1852                 vm_pageout_page_count = 8;
1853
1854         /*
1855          * v_free_reserved needs to include enough for the largest
1856          * swap pager structures plus enough for any pv_entry structs
1857          * when paging.
1858          */
1859         if (vm_cnt.v_page_count > 1024)
1860                 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
1861         else
1862                 vm_cnt.v_free_min = 4;
1863         vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1864             vm_cnt.v_interrupt_free_min;
1865         vm_cnt.v_free_reserved = vm_pageout_page_count +
1866             vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
1867         vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
1868         vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
1869         vm_cnt.v_free_min += vm_cnt.v_free_reserved;
1870         vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
1871         vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
1872         if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
1873                 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
1874
1875         /*
1876          * Set the default wakeup threshold to be 10% above the minimum
1877          * page limit.  This keeps the steady state out of shortfall.
1878          */
1879         vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
1880
1881         /*
1882          * Set interval in seconds for active scan.  We want to visit each
1883          * page at least once every ten minutes.  This is to prevent worst
1884          * case paging behaviors with stale active LRU.
1885          */
1886         if (vm_pageout_update_period == 0)
1887                 vm_pageout_update_period = 600;
1888
1889         /* XXX does not really belong here */
1890         if (vm_page_max_wired == 0)
1891                 vm_page_max_wired = vm_cnt.v_free_count / 3;
1892
1893         /*
1894          * Target amount of memory to move out of the laundry queue during a
1895          * background laundering.  This is proportional to the amount of system
1896          * memory.
1897          */
1898         vm_background_launder_target = (vm_cnt.v_free_target -
1899             vm_cnt.v_free_min) / 10;
1900 }
1901
1902 /*
1903  *     vm_pageout is the high level pageout daemon.
1904  */
1905 static void
1906 vm_pageout(void)
1907 {
1908         int error;
1909 #ifdef VM_NUMA_ALLOC
1910         int i;
1911 #endif
1912
1913         swap_pager_swap_init();
1914         error = kthread_add(vm_pageout_laundry_worker, NULL, curproc, NULL,
1915             0, 0, "laundry: dom0");
1916         if (error != 0)
1917                 panic("starting laundry for domain 0, error %d", error);
1918 #ifdef VM_NUMA_ALLOC
1919         for (i = 1; i < vm_ndomains; i++) {
1920                 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
1921                     curproc, NULL, 0, 0, "dom%d", i);
1922                 if (error != 0) {
1923                         panic("starting pageout for domain %d, error %d\n",
1924                             i, error);
1925                 }
1926         }
1927 #endif
1928         error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
1929             0, 0, "uma");
1930         if (error != 0)
1931                 panic("starting uma_reclaim helper, error %d\n", error);
1932         vm_pageout_worker((void *)(uintptr_t)0);
1933 }
1934
1935 /*
1936  * Unless the free page queue lock is held by the caller, this function
1937  * should be regarded as advisory.  Specifically, the caller should
1938  * not msleep() on &vm_cnt.v_free_count following this function unless
1939  * the free page queue lock is held until the msleep() is performed.
1940  */
1941 void
1942 pagedaemon_wakeup(void)
1943 {
1944
1945         if (!vm_pageout_wanted && curthread->td_proc != pageproc) {
1946                 vm_pageout_wanted = true;
1947                 wakeup(&vm_pageout_wanted);
1948         }
1949 }