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