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"*/ 120 static void vm_pageout(void); 121 static void vm_pageout_init(void); 122 static int vm_pageout_clean(vm_page_t m); 123 static int vm_pageout_cluster(vm_page_t m); 124 static bool vm_pageout_scan(struct vm_domain *vmd, int pass); 125 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 126 int starting_page_shortage); 127 128 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init, 129 NULL); 130 131 struct proc *pageproc; 132 133 static struct kproc_desc page_kp = { 134 "pagedaemon", 135 vm_pageout, 136 &pageproc 137 }; 138 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, 139 &page_kp); 140 141 SDT_PROVIDER_DEFINE(vm); 142 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan); 143 144 #if !defined(NO_SWAPPING) 145 /* the kernel process "vm_daemon"*/ 146 static void vm_daemon(void); 147 static struct proc *vmproc; 148 149 static struct kproc_desc vm_kp = { 150 "vmdaemon", 151 vm_daemon, 152 &vmproc 153 }; 154 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); 155 #endif 156 157 158 int vm_pageout_deficit; /* Estimated number of pages deficit */ 159 u_int vm_pageout_wakeup_thresh; 160 static int vm_pageout_oom_seq = 12; 161 bool vm_pageout_wanted; /* Event on which pageout daemon sleeps */ 162 bool vm_pages_needed; /* Are threads waiting for free pages? */ 163 164 #if !defined(NO_SWAPPING) 165 static int vm_pageout_req_swapout; /* XXX */ 166 static int vm_daemon_needed; 167 static struct mtx vm_daemon_mtx; 168 /* Allow for use by vm_pageout before vm_daemon is initialized. */ 169 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); 170 #endif 171 static int vm_max_launder = 32; 172 static int vm_pageout_update_period; 173 static int defer_swap_pageouts; 174 static int disable_swap_pageouts; 175 static int lowmem_period = 10; 176 static time_t lowmem_uptime; 177 178 #if defined(NO_SWAPPING) 179 static int vm_swap_enabled = 0; 180 static int vm_swap_idle_enabled = 0; 181 #else 182 static int vm_swap_enabled = 1; 183 static int vm_swap_idle_enabled = 0; 184 #endif 185 186 static int vm_panic_on_oom = 0; 187 188 SYSCTL_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"); 191 192 SYSCTL_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"); 195 196 SYSCTL_INT(_vm, OID_AUTO, max_launder, 197 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout"); 198 199 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period, 200 CTLFLAG_RW, &vm_pageout_update_period, 0, 201 "Maximum active LRU update period"); 202 203 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0, 204 "Low memory callback period"); 205 206 #if defined(NO_SWAPPING) 207 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 208 CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout"); 209 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 210 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 211 #else 212 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 213 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 214 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 215 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 216 #endif 217 218 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts, 219 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem"); 220 221 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 222 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 223 224 static int pageout_lock_miss; 225 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 226 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 227 228 SYSCTL_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 16 233 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 234 235 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 236 SYSCTL_INT(_vm, OID_AUTO, max_wired, 237 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count"); 238 239 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *); 240 #if !defined(NO_SWAPPING) 241 static void vm_pageout_map_deactivate_pages(vm_map_t, long); 242 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long); 243 static void vm_req_vmdaemon(int req); 244 #endif 245 static 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 */ 253 static void 254 vm_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 */ 278 static boolean_t 279 vm_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 */ 327 static boolean_t 328 vm_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 */ 362 static int 363 vm_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 */ 400 more: 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 */ 479 int 480 vm_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 */ 577 static void 578 vm_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 } 649 unlock_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 */ 658 static void 659 vm_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 */ 741 static int 742 vm_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; 826 827 unlock_all: 828 VM_OBJECT_WUNLOCK(object); 829 830 unlock_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 * 849 * Returns true if pass was zero or enough pages were freed by the inactive 850 * queue scan to meet the target. 851 */ 852 static bool 853 vm_pageout_scan(struct vm_domain *vmd, int pass) 854 { 855 vm_page_t m, next; 856 struct vm_pagequeue *pq; 857 vm_object_t object; 858 long min_scan; 859 int act_delta, addl_page_shortage, deficit, error, inactq_shortage; 860 int maxlaunder, maxscan, page_shortage, scan_tick, scanned; 861 int starting_page_shortage, vnodes_skipped; 862 boolean_t pageout_ok, queue_locked; 863 864 /* 865 * If we need to reclaim memory ask kernel caches to return 866 * some. We rate limit to avoid thrashing. 867 */ 868 if (vmd == &vm_dom[0] && pass > 0 && 869 (time_uptime - lowmem_uptime) >= lowmem_period) { 870 /* 871 * Decrease registered cache sizes. 872 */ 873 SDT_PROBE0(vm, , , vm__lowmem_scan); 874 EVENTHANDLER_INVOKE(vm_lowmem, 0); 875 /* 876 * We do this explicitly after the caches have been 877 * drained above. 878 */ 879 uma_reclaim(); 880 lowmem_uptime = time_uptime; 881 } 882 883 /* 884 * The addl_page_shortage is the number of temporarily 885 * stuck pages in the inactive queue. In other words, the 886 * number of pages from the inactive count that should be 887 * discounted in setting the target for the active queue scan. 888 */ 889 addl_page_shortage = 0; 890 891 /* 892 * Calculate the number of pages that we want to free. This number 893 * can be negative if many pages are freed between the wakeup call to 894 * the page daemon and this calculation. 895 */ 896 if (pass > 0) { 897 deficit = atomic_readandclear_int(&vm_pageout_deficit); 898 page_shortage = vm_paging_target() + deficit; 899 } else 900 page_shortage = deficit = 0; 901 starting_page_shortage = page_shortage; 902 903 /* 904 * maxlaunder limits the number of dirty pages we flush per scan. 905 * For most systems a smaller value (16 or 32) is more robust under 906 * extreme memory and disk pressure because any unnecessary writes 907 * to disk can result in extreme performance degredation. However, 908 * systems with excessive dirty pages (especially when MAP_NOSYNC is 909 * used) will die horribly with limited laundering. If the pageout 910 * daemon cannot clean enough pages in the first pass, we let it go 911 * all out in succeeding passes. 912 */ 913 if ((maxlaunder = vm_max_launder) <= 1) 914 maxlaunder = 1; 915 if (pass > 1) 916 maxlaunder = 10000; 917 918 vnodes_skipped = 0; 919 920 /* 921 * Start scanning the inactive queue for pages that we can free. The 922 * scan will stop when we reach the target or we have scanned the 923 * entire queue. (Note that m->act_count is not used to make 924 * decisions for the inactive queue, only for the active queue.) 925 */ 926 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 927 maxscan = pq->pq_cnt; 928 vm_pagequeue_lock(pq); 929 queue_locked = TRUE; 930 for (m = TAILQ_FIRST(&pq->pq_pl); 931 m != NULL && maxscan-- > 0 && page_shortage > 0; 932 m = next) { 933 vm_pagequeue_assert_locked(pq); 934 KASSERT(queue_locked, ("unlocked inactive queue")); 935 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m)); 936 937 PCPU_INC(cnt.v_pdpages); 938 next = TAILQ_NEXT(m, plinks.q); 939 940 /* 941 * skip marker pages 942 */ 943 if (m->flags & PG_MARKER) 944 continue; 945 946 KASSERT((m->flags & PG_FICTITIOUS) == 0, 947 ("Fictitious page %p cannot be in inactive queue", m)); 948 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 949 ("Unmanaged page %p cannot be in inactive queue", m)); 950 951 /* 952 * The page or object lock acquisitions fail if the 953 * page was removed from the queue or moved to a 954 * different position within the queue. In either 955 * case, addl_page_shortage should not be incremented. 956 */ 957 if (!vm_pageout_page_lock(m, &next)) 958 goto unlock_page; 959 else if (m->hold_count != 0) { 960 /* 961 * Held pages are essentially stuck in the 962 * queue. So, they ought to be discounted 963 * from the inactive count. See the 964 * calculation of inactq_shortage before the 965 * loop over the active queue below. 966 */ 967 addl_page_shortage++; 968 goto unlock_page; 969 } 970 object = m->object; 971 if (!VM_OBJECT_TRYWLOCK(object)) { 972 if (!vm_pageout_fallback_object_lock(m, &next)) 973 goto unlock_object; 974 else if (m->hold_count != 0) { 975 addl_page_shortage++; 976 goto unlock_object; 977 } 978 } 979 if (vm_page_busied(m)) { 980 /* 981 * Don't mess with busy pages. Leave them at 982 * the front of the queue. Most likely, they 983 * are being paged out and will leave the 984 * queue shortly after the scan finishes. So, 985 * they ought to be discounted from the 986 * inactive count. 987 */ 988 addl_page_shortage++; 989 unlock_object: 990 VM_OBJECT_WUNLOCK(object); 991 unlock_page: 992 vm_page_unlock(m); 993 continue; 994 } 995 KASSERT(m->hold_count == 0, ("Held page %p", m)); 996 997 /* 998 * We unlock the inactive page queue, invalidating the 999 * 'next' pointer. Use our marker to remember our 1000 * place. 1001 */ 1002 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q); 1003 vm_pagequeue_unlock(pq); 1004 queue_locked = FALSE; 1005 1006 /* 1007 * Invalid pages can be easily freed. They cannot be 1008 * mapped, vm_page_free() asserts this. 1009 */ 1010 if (m->valid == 0) 1011 goto free_page; 1012 1013 /* 1014 * If the page has been referenced and the object is not dead, 1015 * reactivate or requeue the page depending on whether the 1016 * object is mapped. 1017 */ 1018 if ((m->aflags & PGA_REFERENCED) != 0) { 1019 vm_page_aflag_clear(m, PGA_REFERENCED); 1020 act_delta = 1; 1021 } else 1022 act_delta = 0; 1023 if (object->ref_count != 0) { 1024 act_delta += pmap_ts_referenced(m); 1025 } else { 1026 KASSERT(!pmap_page_is_mapped(m), 1027 ("vm_pageout_scan: page %p is mapped", m)); 1028 } 1029 if (act_delta != 0) { 1030 if (object->ref_count != 0) { 1031 vm_page_activate(m); 1032 1033 /* 1034 * Increase the activation count if the page 1035 * was referenced while in the inactive queue. 1036 * This makes it less likely that the page will 1037 * be returned prematurely to the inactive 1038 * queue. 1039 */ 1040 m->act_count += act_delta + ACT_ADVANCE; 1041 goto drop_page; 1042 } else if ((object->flags & OBJ_DEAD) == 0) 1043 goto requeue_page; 1044 } 1045 1046 /* 1047 * If the page appears to be clean at the machine-independent 1048 * layer, then remove all of its mappings from the pmap in 1049 * anticipation of freeing it. If, however, any of the page's 1050 * mappings allow write access, then the page may still be 1051 * modified until the last of those mappings are removed. 1052 */ 1053 if (object->ref_count != 0) { 1054 vm_page_test_dirty(m); 1055 if (m->dirty == 0) 1056 pmap_remove_all(m); 1057 } 1058 1059 if (m->dirty == 0) { 1060 /* 1061 * Clean pages can be freed. 1062 */ 1063 free_page: 1064 vm_page_free(m); 1065 PCPU_INC(cnt.v_dfree); 1066 --page_shortage; 1067 } else if ((object->flags & OBJ_DEAD) != 0) { 1068 /* 1069 * Leave dirty pages from dead objects at the front of 1070 * the queue. They are being paged out and freed by 1071 * the thread that destroyed the object. They will 1072 * leave the queue shortly after the scan finishes, so 1073 * they should be discounted from the inactive count. 1074 */ 1075 addl_page_shortage++; 1076 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) { 1077 /* 1078 * Dirty pages need to be paged out, but flushing 1079 * a page is extremely expensive versus freeing 1080 * a clean page. Rather then artificially limiting 1081 * the number of pages we can flush, we instead give 1082 * dirty pages extra priority on the inactive queue 1083 * by forcing them to be cycled through the queue 1084 * twice before being flushed, after which the 1085 * (now clean) page will cycle through once more 1086 * before being freed. This significantly extends 1087 * the thrash point for a heavily loaded machine. 1088 */ 1089 m->flags |= PG_WINATCFLS; 1090 requeue_page: 1091 vm_pagequeue_lock(pq); 1092 queue_locked = TRUE; 1093 vm_page_requeue_locked(m); 1094 } else if (maxlaunder > 0) { 1095 /* 1096 * We always want to try to flush some dirty pages if 1097 * we encounter them, to keep the system stable. 1098 * Normally this number is small, but under extreme 1099 * pressure where there are insufficient clean pages 1100 * on the inactive queue, we may have to go all out. 1101 */ 1102 1103 if (object->type != OBJT_SWAP && 1104 object->type != OBJT_DEFAULT) 1105 pageout_ok = TRUE; 1106 else if (disable_swap_pageouts) 1107 pageout_ok = FALSE; 1108 else if (defer_swap_pageouts) 1109 pageout_ok = vm_page_count_min(); 1110 else 1111 pageout_ok = TRUE; 1112 if (!pageout_ok) 1113 goto requeue_page; 1114 error = vm_pageout_clean(m); 1115 /* 1116 * Decrement page_shortage on success to account for 1117 * the (future) cleaned page. Otherwise we could wind 1118 * up laundering or cleaning too many pages. 1119 */ 1120 if (error == 0) { 1121 page_shortage--; 1122 maxlaunder--; 1123 } else if (error == EDEADLK) { 1124 pageout_lock_miss++; 1125 vnodes_skipped++; 1126 } else if (error == EBUSY) { 1127 addl_page_shortage++; 1128 } 1129 vm_page_lock_assert(m, MA_NOTOWNED); 1130 goto relock_queue; 1131 } 1132 drop_page: 1133 vm_page_unlock(m); 1134 VM_OBJECT_WUNLOCK(object); 1135 relock_queue: 1136 if (!queue_locked) { 1137 vm_pagequeue_lock(pq); 1138 queue_locked = TRUE; 1139 } 1140 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q); 1141 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q); 1142 } 1143 vm_pagequeue_unlock(pq); 1144 1145 #if !defined(NO_SWAPPING) 1146 /* 1147 * Wakeup the swapout daemon if we didn't free the targeted number of 1148 * pages. 1149 */ 1150 if (vm_swap_enabled && page_shortage > 0) 1151 vm_req_vmdaemon(VM_SWAP_NORMAL); 1152 #endif 1153 1154 /* 1155 * Wakeup the sync daemon if we skipped a vnode in a writeable object 1156 * and we didn't free enough pages. 1157 */ 1158 if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target - 1159 vm_cnt.v_free_min) 1160 (void)speedup_syncer(); 1161 1162 /* 1163 * If the inactive queue scan fails repeatedly to meet its 1164 * target, kill the largest process. 1165 */ 1166 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1167 1168 /* 1169 * Compute the number of pages we want to try to move from the 1170 * active queue to the inactive queue. 1171 */ 1172 inactq_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count + 1173 vm_paging_target() + deficit + addl_page_shortage; 1174 1175 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1176 vm_pagequeue_lock(pq); 1177 maxscan = pq->pq_cnt; 1178 1179 /* 1180 * If we're just idle polling attempt to visit every 1181 * active page within 'update_period' seconds. 1182 */ 1183 scan_tick = ticks; 1184 if (vm_pageout_update_period != 0) { 1185 min_scan = pq->pq_cnt; 1186 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1187 min_scan /= hz * vm_pageout_update_period; 1188 } else 1189 min_scan = 0; 1190 if (min_scan > 0 || (inactq_shortage > 0 && maxscan > 0)) 1191 vmd->vmd_last_active_scan = scan_tick; 1192 1193 /* 1194 * Scan the active queue for pages that can be deactivated. Update 1195 * the per-page activity counter and use it to identify deactivation 1196 * candidates. Held pages may be deactivated. 1197 */ 1198 for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned < 1199 min_scan || (inactq_shortage > 0 && scanned < maxscan)); m = next, 1200 scanned++) { 1201 KASSERT(m->queue == PQ_ACTIVE, 1202 ("vm_pageout_scan: page %p isn't active", m)); 1203 next = TAILQ_NEXT(m, plinks.q); 1204 if ((m->flags & PG_MARKER) != 0) 1205 continue; 1206 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1207 ("Fictitious page %p cannot be in active queue", m)); 1208 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1209 ("Unmanaged page %p cannot be in active queue", m)); 1210 if (!vm_pageout_page_lock(m, &next)) { 1211 vm_page_unlock(m); 1212 continue; 1213 } 1214 1215 /* 1216 * The count for page daemon pages is updated after checking 1217 * the page for eligibility. 1218 */ 1219 PCPU_INC(cnt.v_pdpages); 1220 1221 /* 1222 * Check to see "how much" the page has been used. 1223 */ 1224 if ((m->aflags & PGA_REFERENCED) != 0) { 1225 vm_page_aflag_clear(m, PGA_REFERENCED); 1226 act_delta = 1; 1227 } else 1228 act_delta = 0; 1229 1230 /* 1231 * Perform an unsynchronized object ref count check. While 1232 * the page lock ensures that the page is not reallocated to 1233 * another object, in particular, one with unmanaged mappings 1234 * that cannot support pmap_ts_referenced(), two races are, 1235 * nonetheless, possible: 1236 * 1) The count was transitioning to zero, but we saw a non- 1237 * zero value. pmap_ts_referenced() will return zero 1238 * because the page is not mapped. 1239 * 2) The count was transitioning to one, but we saw zero. 1240 * This race delays the detection of a new reference. At 1241 * worst, we will deactivate and reactivate the page. 1242 */ 1243 if (m->object->ref_count != 0) 1244 act_delta += pmap_ts_referenced(m); 1245 1246 /* 1247 * Advance or decay the act_count based on recent usage. 1248 */ 1249 if (act_delta != 0) { 1250 m->act_count += ACT_ADVANCE + act_delta; 1251 if (m->act_count > ACT_MAX) 1252 m->act_count = ACT_MAX; 1253 } else 1254 m->act_count -= min(m->act_count, ACT_DECLINE); 1255 1256 /* 1257 * Move this page to the tail of the active or inactive 1258 * queue depending on usage. 1259 */ 1260 if (m->act_count == 0) { 1261 /* Dequeue to avoid later lock recursion. */ 1262 vm_page_dequeue_locked(m); 1263 vm_page_deactivate(m); 1264 inactq_shortage--; 1265 } else 1266 vm_page_requeue_locked(m); 1267 vm_page_unlock(m); 1268 } 1269 vm_pagequeue_unlock(pq); 1270 #if !defined(NO_SWAPPING) 1271 /* 1272 * Idle process swapout -- run once per second when we are reclaiming 1273 * pages. 1274 */ 1275 if (vm_swap_idle_enabled && pass > 0) { 1276 static long lsec; 1277 if (time_second != lsec) { 1278 vm_req_vmdaemon(VM_SWAP_IDLE); 1279 lsec = time_second; 1280 } 1281 } 1282 #endif 1283 return (page_shortage <= 0); 1284 } 1285 1286 static int vm_pageout_oom_vote; 1287 1288 /* 1289 * The pagedaemon threads randlomly select one to perform the 1290 * OOM. Trying to kill processes before all pagedaemons 1291 * failed to reach free target is premature. 1292 */ 1293 static void 1294 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1295 int starting_page_shortage) 1296 { 1297 int old_vote; 1298 1299 if (starting_page_shortage <= 0 || starting_page_shortage != 1300 page_shortage) 1301 vmd->vmd_oom_seq = 0; 1302 else 1303 vmd->vmd_oom_seq++; 1304 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1305 if (vmd->vmd_oom) { 1306 vmd->vmd_oom = FALSE; 1307 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1308 } 1309 return; 1310 } 1311 1312 /* 1313 * Do not follow the call sequence until OOM condition is 1314 * cleared. 1315 */ 1316 vmd->vmd_oom_seq = 0; 1317 1318 if (vmd->vmd_oom) 1319 return; 1320 1321 vmd->vmd_oom = TRUE; 1322 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1323 if (old_vote != vm_ndomains - 1) 1324 return; 1325 1326 /* 1327 * The current pagedaemon thread is the last in the quorum to 1328 * start OOM. Initiate the selection and signaling of the 1329 * victim. 1330 */ 1331 vm_pageout_oom(VM_OOM_MEM); 1332 1333 /* 1334 * After one round of OOM terror, recall our vote. On the 1335 * next pass, current pagedaemon would vote again if the low 1336 * memory condition is still there, due to vmd_oom being 1337 * false. 1338 */ 1339 vmd->vmd_oom = FALSE; 1340 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1341 } 1342 1343 /* 1344 * The OOM killer is the page daemon's action of last resort when 1345 * memory allocation requests have been stalled for a prolonged period 1346 * of time because it cannot reclaim memory. This function computes 1347 * the approximate number of physical pages that could be reclaimed if 1348 * the specified address space is destroyed. 1349 * 1350 * Private, anonymous memory owned by the address space is the 1351 * principal resource that we expect to recover after an OOM kill. 1352 * Since the physical pages mapped by the address space's COW entries 1353 * are typically shared pages, they are unlikely to be released and so 1354 * they are not counted. 1355 * 1356 * To get to the point where the page daemon runs the OOM killer, its 1357 * efforts to write-back vnode-backed pages may have stalled. This 1358 * could be caused by a memory allocation deadlock in the write path 1359 * that might be resolved by an OOM kill. Therefore, physical pages 1360 * belonging to vnode-backed objects are counted, because they might 1361 * be freed without being written out first if the address space holds 1362 * the last reference to an unlinked vnode. 1363 * 1364 * Similarly, physical pages belonging to OBJT_PHYS objects are 1365 * counted because the address space might hold the last reference to 1366 * the object. 1367 */ 1368 static long 1369 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1370 { 1371 vm_map_t map; 1372 vm_map_entry_t entry; 1373 vm_object_t obj; 1374 long res; 1375 1376 map = &vmspace->vm_map; 1377 KASSERT(!map->system_map, ("system map")); 1378 sx_assert(&map->lock, SA_LOCKED); 1379 res = 0; 1380 for (entry = map->header.next; entry != &map->header; 1381 entry = entry->next) { 1382 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1383 continue; 1384 obj = entry->object.vm_object; 1385 if (obj == NULL) 1386 continue; 1387 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1388 obj->ref_count != 1) 1389 continue; 1390 switch (obj->type) { 1391 case OBJT_DEFAULT: 1392 case OBJT_SWAP: 1393 case OBJT_PHYS: 1394 case OBJT_VNODE: 1395 res += obj->resident_page_count; 1396 break; 1397 } 1398 } 1399 return (res); 1400 } 1401 1402 void 1403 vm_pageout_oom(int shortage) 1404 { 1405 struct proc *p, *bigproc; 1406 vm_offset_t size, bigsize; 1407 struct thread *td; 1408 struct vmspace *vm; 1409 1410 /* 1411 * We keep the process bigproc locked once we find it to keep anyone 1412 * from messing with it; however, there is a possibility of 1413 * deadlock if process B is bigproc and one of it's child processes 1414 * attempts to propagate a signal to B while we are waiting for A's 1415 * lock while walking this list. To avoid this, we don't block on 1416 * the process lock but just skip a process if it is already locked. 1417 */ 1418 bigproc = NULL; 1419 bigsize = 0; 1420 sx_slock(&allproc_lock); 1421 FOREACH_PROC_IN_SYSTEM(p) { 1422 int breakout; 1423 1424 PROC_LOCK(p); 1425 1426 /* 1427 * If this is a system, protected or killed process, skip it. 1428 */ 1429 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1430 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1431 p->p_pid == 1 || P_KILLED(p) || 1432 (p->p_pid < 48 && swap_pager_avail != 0)) { 1433 PROC_UNLOCK(p); 1434 continue; 1435 } 1436 /* 1437 * If the process is in a non-running type state, 1438 * don't touch it. Check all the threads individually. 1439 */ 1440 breakout = 0; 1441 FOREACH_THREAD_IN_PROC(p, td) { 1442 thread_lock(td); 1443 if (!TD_ON_RUNQ(td) && 1444 !TD_IS_RUNNING(td) && 1445 !TD_IS_SLEEPING(td) && 1446 !TD_IS_SUSPENDED(td) && 1447 !TD_IS_SWAPPED(td)) { 1448 thread_unlock(td); 1449 breakout = 1; 1450 break; 1451 } 1452 thread_unlock(td); 1453 } 1454 if (breakout) { 1455 PROC_UNLOCK(p); 1456 continue; 1457 } 1458 /* 1459 * get the process size 1460 */ 1461 vm = vmspace_acquire_ref(p); 1462 if (vm == NULL) { 1463 PROC_UNLOCK(p); 1464 continue; 1465 } 1466 _PHOLD_LITE(p); 1467 PROC_UNLOCK(p); 1468 sx_sunlock(&allproc_lock); 1469 if (!vm_map_trylock_read(&vm->vm_map)) { 1470 vmspace_free(vm); 1471 sx_slock(&allproc_lock); 1472 PRELE(p); 1473 continue; 1474 } 1475 size = vmspace_swap_count(vm); 1476 if (shortage == VM_OOM_MEM) 1477 size += vm_pageout_oom_pagecount(vm); 1478 vm_map_unlock_read(&vm->vm_map); 1479 vmspace_free(vm); 1480 sx_slock(&allproc_lock); 1481 1482 /* 1483 * If this process is bigger than the biggest one, 1484 * remember it. 1485 */ 1486 if (size > bigsize) { 1487 if (bigproc != NULL) 1488 PRELE(bigproc); 1489 bigproc = p; 1490 bigsize = size; 1491 } else { 1492 PRELE(p); 1493 } 1494 } 1495 sx_sunlock(&allproc_lock); 1496 if (bigproc != NULL) { 1497 if (vm_panic_on_oom != 0) 1498 panic("out of swap space"); 1499 PROC_LOCK(bigproc); 1500 killproc(bigproc, "out of swap space"); 1501 sched_nice(bigproc, PRIO_MIN); 1502 _PRELE(bigproc); 1503 PROC_UNLOCK(bigproc); 1504 wakeup(&vm_cnt.v_free_count); 1505 } 1506 } 1507 1508 static void 1509 vm_pageout_worker(void *arg) 1510 { 1511 struct vm_domain *domain; 1512 int domidx, pass; 1513 bool target_met; 1514 1515 domidx = (uintptr_t)arg; 1516 domain = &vm_dom[domidx]; 1517 pass = 0; 1518 target_met = true; 1519 1520 /* 1521 * XXXKIB It could be useful to bind pageout daemon threads to 1522 * the cores belonging to the domain, from which vm_page_array 1523 * is allocated. 1524 */ 1525 1526 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1527 domain->vmd_last_active_scan = ticks; 1528 vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE); 1529 vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE); 1530 TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl, 1531 &domain->vmd_inacthead, plinks.q); 1532 1533 /* 1534 * The pageout daemon worker is never done, so loop forever. 1535 */ 1536 while (TRUE) { 1537 mtx_lock(&vm_page_queue_free_mtx); 1538 1539 /* 1540 * Generally, after a level >= 1 scan, if there are enough 1541 * free pages to wakeup the waiters, then they are already 1542 * awake. A call to vm_page_free() during the scan awakened 1543 * them. However, in the following case, this wakeup serves 1544 * to bound the amount of time that a thread might wait. 1545 * Suppose a thread's call to vm_page_alloc() fails, but 1546 * before that thread calls VM_WAIT, enough pages are freed by 1547 * other threads to alleviate the free page shortage. The 1548 * thread will, nonetheless, wait until another page is freed 1549 * or this wakeup is performed. 1550 */ 1551 if (vm_pages_needed && !vm_page_count_min()) { 1552 vm_pages_needed = false; 1553 wakeup(&vm_cnt.v_free_count); 1554 } 1555 1556 /* 1557 * Do not clear vm_pageout_wanted until we reach our free page 1558 * target. Otherwise, we may be awakened over and over again, 1559 * wasting CPU time. 1560 */ 1561 if (vm_pageout_wanted && target_met) 1562 vm_pageout_wanted = false; 1563 1564 /* 1565 * Might the page daemon receive a wakeup call? 1566 */ 1567 if (vm_pageout_wanted) { 1568 /* 1569 * No. Either vm_pageout_wanted was set by another 1570 * thread during the previous scan, which must have 1571 * been a level 0 scan, or vm_pageout_wanted was 1572 * already set and the scan failed to free enough 1573 * pages. If we haven't yet performed a level >= 2 1574 * scan (unlimited dirty cleaning), then upgrade the 1575 * level and scan again now. Otherwise, sleep a bit 1576 * and try again later. 1577 */ 1578 mtx_unlock(&vm_page_queue_free_mtx); 1579 if (pass > 1) 1580 pause("psleep", hz / 2); 1581 pass++; 1582 } else { 1583 /* 1584 * Yes. Sleep until pages need to be reclaimed or 1585 * have their reference stats updated. 1586 */ 1587 if (mtx_sleep(&vm_pageout_wanted, 1588 &vm_page_queue_free_mtx, PDROP | PVM, "psleep", 1589 hz) == 0) { 1590 PCPU_INC(cnt.v_pdwakeups); 1591 pass = 1; 1592 } else 1593 pass = 0; 1594 } 1595 1596 target_met = vm_pageout_scan(domain, pass); 1597 } 1598 } 1599 1600 /* 1601 * vm_pageout_init initialises basic pageout daemon settings. 1602 */ 1603 static void 1604 vm_pageout_init(void) 1605 { 1606 /* 1607 * Initialize some paging parameters. 1608 */ 1609 vm_cnt.v_interrupt_free_min = 2; 1610 if (vm_cnt.v_page_count < 2000) 1611 vm_pageout_page_count = 8; 1612 1613 /* 1614 * v_free_reserved needs to include enough for the largest 1615 * swap pager structures plus enough for any pv_entry structs 1616 * when paging. 1617 */ 1618 if (vm_cnt.v_page_count > 1024) 1619 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200; 1620 else 1621 vm_cnt.v_free_min = 4; 1622 vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 1623 vm_cnt.v_interrupt_free_min; 1624 vm_cnt.v_free_reserved = vm_pageout_page_count + 1625 vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768); 1626 vm_cnt.v_free_severe = vm_cnt.v_free_min / 2; 1627 vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved; 1628 vm_cnt.v_free_min += vm_cnt.v_free_reserved; 1629 vm_cnt.v_free_severe += vm_cnt.v_free_reserved; 1630 vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2; 1631 if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3) 1632 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3; 1633 1634 /* 1635 * Set the default wakeup threshold to be 10% above the minimum 1636 * page limit. This keeps the steady state out of shortfall. 1637 */ 1638 vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11; 1639 1640 /* 1641 * Set interval in seconds for active scan. We want to visit each 1642 * page at least once every ten minutes. This is to prevent worst 1643 * case paging behaviors with stale active LRU. 1644 */ 1645 if (vm_pageout_update_period == 0) 1646 vm_pageout_update_period = 600; 1647 1648 /* XXX does not really belong here */ 1649 if (vm_page_max_wired == 0) 1650 vm_page_max_wired = vm_cnt.v_free_count / 3; 1651 } 1652 1653 /* 1654 * vm_pageout is the high level pageout daemon. 1655 */ 1656 static void 1657 vm_pageout(void) 1658 { 1659 int error; 1660 #ifdef VM_NUMA_ALLOC 1661 int i; 1662 #endif 1663 1664 swap_pager_swap_init(); 1665 #ifdef VM_NUMA_ALLOC 1666 for (i = 1; i < vm_ndomains; i++) { 1667 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i, 1668 curproc, NULL, 0, 0, "dom%d", i); 1669 if (error != 0) { 1670 panic("starting pageout for domain %d, error %d\n", 1671 i, error); 1672 } 1673 } 1674 #endif 1675 error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL, 1676 0, 0, "uma"); 1677 if (error != 0) 1678 panic("starting uma_reclaim helper, error %d\n", error); 1679 vm_pageout_worker((void *)(uintptr_t)0); 1680 } 1681 1682 /* 1683 * Unless the free page queue lock is held by the caller, this function 1684 * should be regarded as advisory. Specifically, the caller should 1685 * not msleep() on &vm_cnt.v_free_count following this function unless 1686 * the free page queue lock is held until the msleep() is performed. 1687 */ 1688 void 1689 pagedaemon_wakeup(void) 1690 { 1691 1692 if (!vm_pageout_wanted && curthread->td_proc != pageproc) { 1693 vm_pageout_wanted = true; 1694 wakeup(&vm_pageout_wanted); 1695 } 1696 } 1697 1698 #if !defined(NO_SWAPPING) 1699 static void 1700 vm_req_vmdaemon(int req) 1701 { 1702 static int lastrun = 0; 1703 1704 mtx_lock(&vm_daemon_mtx); 1705 vm_pageout_req_swapout |= req; 1706 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 1707 wakeup(&vm_daemon_needed); 1708 lastrun = ticks; 1709 } 1710 mtx_unlock(&vm_daemon_mtx); 1711 } 1712 1713 static void 1714 vm_daemon(void) 1715 { 1716 struct rlimit rsslim; 1717 struct proc *p; 1718 struct thread *td; 1719 struct vmspace *vm; 1720 int breakout, swapout_flags, tryagain, attempts; 1721 #ifdef RACCT 1722 uint64_t rsize, ravailable; 1723 #endif 1724 1725 while (TRUE) { 1726 mtx_lock(&vm_daemon_mtx); 1727 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 1728 #ifdef RACCT 1729 racct_enable ? hz : 0 1730 #else 1731 0 1732 #endif 1733 ); 1734 swapout_flags = vm_pageout_req_swapout; 1735 vm_pageout_req_swapout = 0; 1736 mtx_unlock(&vm_daemon_mtx); 1737 if (swapout_flags) 1738 swapout_procs(swapout_flags); 1739 1740 /* 1741 * scan the processes for exceeding their rlimits or if 1742 * process is swapped out -- deactivate pages 1743 */ 1744 tryagain = 0; 1745 attempts = 0; 1746 again: 1747 attempts++; 1748 sx_slock(&allproc_lock); 1749 FOREACH_PROC_IN_SYSTEM(p) { 1750 vm_pindex_t limit, size; 1751 1752 /* 1753 * if this is a system process or if we have already 1754 * looked at this process, skip it. 1755 */ 1756 PROC_LOCK(p); 1757 if (p->p_state != PRS_NORMAL || 1758 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 1759 PROC_UNLOCK(p); 1760 continue; 1761 } 1762 /* 1763 * if the process is in a non-running type state, 1764 * don't touch it. 1765 */ 1766 breakout = 0; 1767 FOREACH_THREAD_IN_PROC(p, td) { 1768 thread_lock(td); 1769 if (!TD_ON_RUNQ(td) && 1770 !TD_IS_RUNNING(td) && 1771 !TD_IS_SLEEPING(td) && 1772 !TD_IS_SUSPENDED(td)) { 1773 thread_unlock(td); 1774 breakout = 1; 1775 break; 1776 } 1777 thread_unlock(td); 1778 } 1779 if (breakout) { 1780 PROC_UNLOCK(p); 1781 continue; 1782 } 1783 /* 1784 * get a limit 1785 */ 1786 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 1787 limit = OFF_TO_IDX( 1788 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 1789 1790 /* 1791 * let processes that are swapped out really be 1792 * swapped out set the limit to nothing (will force a 1793 * swap-out.) 1794 */ 1795 if ((p->p_flag & P_INMEM) == 0) 1796 limit = 0; /* XXX */ 1797 vm = vmspace_acquire_ref(p); 1798 _PHOLD_LITE(p); 1799 PROC_UNLOCK(p); 1800 if (vm == NULL) { 1801 PRELE(p); 1802 continue; 1803 } 1804 sx_sunlock(&allproc_lock); 1805 1806 size = vmspace_resident_count(vm); 1807 if (size >= limit) { 1808 vm_pageout_map_deactivate_pages( 1809 &vm->vm_map, limit); 1810 } 1811 #ifdef RACCT 1812 if (racct_enable) { 1813 rsize = IDX_TO_OFF(size); 1814 PROC_LOCK(p); 1815 racct_set(p, RACCT_RSS, rsize); 1816 ravailable = racct_get_available(p, RACCT_RSS); 1817 PROC_UNLOCK(p); 1818 if (rsize > ravailable) { 1819 /* 1820 * Don't be overly aggressive; this 1821 * might be an innocent process, 1822 * and the limit could've been exceeded 1823 * by some memory hog. Don't try 1824 * to deactivate more than 1/4th 1825 * of process' resident set size. 1826 */ 1827 if (attempts <= 8) { 1828 if (ravailable < rsize - 1829 (rsize / 4)) { 1830 ravailable = rsize - 1831 (rsize / 4); 1832 } 1833 } 1834 vm_pageout_map_deactivate_pages( 1835 &vm->vm_map, 1836 OFF_TO_IDX(ravailable)); 1837 /* Update RSS usage after paging out. */ 1838 size = vmspace_resident_count(vm); 1839 rsize = IDX_TO_OFF(size); 1840 PROC_LOCK(p); 1841 racct_set(p, RACCT_RSS, rsize); 1842 PROC_UNLOCK(p); 1843 if (rsize > ravailable) 1844 tryagain = 1; 1845 } 1846 } 1847 #endif 1848 vmspace_free(vm); 1849 sx_slock(&allproc_lock); 1850 PRELE(p); 1851 } 1852 sx_sunlock(&allproc_lock); 1853 if (tryagain != 0 && attempts <= 10) 1854 goto again; 1855 } 1856 } 1857 #endif /* !defined(NO_SWAPPING) */ 1858