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sys/vm/vm_pageout.c
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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: releng/11.0/sys/vm/vm_pageout.c 303939 2016-08-10 20:31:10Z alc $"); 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 void 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 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 queues 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 * vm_pageout_clean: 359 * 360 * Clean the page and remove it from the laundry. 361 * 362 * We set the busy bit to cause potential page faults on this page to 363 * block. Note the careful timing, however, the busy bit isn't set till 364 * late and we cannot do anything that will mess with the page. 365 */ 366 static int 367 vm_pageout_cluster(vm_page_t m) 368 { 369 vm_object_t object; 370 vm_page_t mc[2*vm_pageout_page_count], pb, ps; 371 int pageout_count; 372 int ib, is, page_base; 373 vm_pindex_t pindex = m->pindex; 374 375 vm_page_lock_assert(m, MA_OWNED); 376 object = m->object; 377 VM_OBJECT_ASSERT_WLOCKED(object); 378 379 /* 380 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP 381 * with the new swapper, but we could have serious problems paging 382 * out other object types if there is insufficient memory. 383 * 384 * Unfortunately, checking free memory here is far too late, so the 385 * check has been moved up a procedural level. 386 */ 387 388 /* 389 * Can't clean the page if it's busy or held. 390 */ 391 vm_page_assert_unbusied(m); 392 KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m)); 393 vm_page_unlock(m); 394 395 mc[vm_pageout_page_count] = pb = ps = m; 396 pageout_count = 1; 397 page_base = vm_pageout_page_count; 398 ib = 1; 399 is = 1; 400 401 /* 402 * Scan object for clusterable pages. 403 * 404 * We can cluster ONLY if: ->> the page is NOT 405 * clean, wired, busy, held, or mapped into a 406 * buffer, and one of the following: 407 * 1) The page is inactive, or a seldom used 408 * active page. 409 * -or- 410 * 2) we force the issue. 411 * 412 * During heavy mmap/modification loads the pageout 413 * daemon can really fragment the underlying file 414 * due to flushing pages out of order and not trying 415 * align the clusters (which leave sporatic out-of-order 416 * holes). To solve this problem we do the reverse scan 417 * first and attempt to align our cluster, then do a 418 * forward scan if room remains. 419 */ 420 more: 421 while (ib && pageout_count < vm_pageout_page_count) { 422 vm_page_t p; 423 424 if (ib > pindex) { 425 ib = 0; 426 break; 427 } 428 429 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) { 430 ib = 0; 431 break; 432 } 433 vm_page_test_dirty(p); 434 if (p->dirty == 0) { 435 ib = 0; 436 break; 437 } 438 vm_page_lock(p); 439 if (p->queue != PQ_INACTIVE || 440 p->hold_count != 0) { /* may be undergoing I/O */ 441 vm_page_unlock(p); 442 ib = 0; 443 break; 444 } 445 vm_page_unlock(p); 446 mc[--page_base] = pb = p; 447 ++pageout_count; 448 ++ib; 449 /* 450 * alignment boundary, stop here and switch directions. Do 451 * not clear ib. 452 */ 453 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 454 break; 455 } 456 457 while (pageout_count < vm_pageout_page_count && 458 pindex + is < object->size) { 459 vm_page_t p; 460 461 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p)) 462 break; 463 vm_page_test_dirty(p); 464 if (p->dirty == 0) 465 break; 466 vm_page_lock(p); 467 if (p->queue != PQ_INACTIVE || 468 p->hold_count != 0) { /* may be undergoing I/O */ 469 vm_page_unlock(p); 470 break; 471 } 472 vm_page_unlock(p); 473 mc[page_base + pageout_count] = ps = p; 474 ++pageout_count; 475 ++is; 476 } 477 478 /* 479 * If we exhausted our forward scan, continue with the reverse scan 480 * when possible, even past a page boundary. This catches boundary 481 * conditions. 482 */ 483 if (ib && pageout_count < vm_pageout_page_count) 484 goto more; 485 486 /* 487 * we allow reads during pageouts... 488 */ 489 return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL, 490 NULL)); 491 } 492 493 /* 494 * vm_pageout_flush() - launder the given pages 495 * 496 * The given pages are laundered. Note that we setup for the start of 497 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 498 * reference count all in here rather then in the parent. If we want 499 * the parent to do more sophisticated things we may have to change 500 * the ordering. 501 * 502 * Returned runlen is the count of pages between mreq and first 503 * page after mreq with status VM_PAGER_AGAIN. 504 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL 505 * for any page in runlen set. 506 */ 507 int 508 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen, 509 boolean_t *eio) 510 { 511 vm_object_t object = mc[0]->object; 512 int pageout_status[count]; 513 int numpagedout = 0; 514 int i, runlen; 515 516 VM_OBJECT_ASSERT_WLOCKED(object); 517 518 /* 519 * Initiate I/O. Bump the vm_page_t->busy counter and 520 * mark the pages read-only. 521 * 522 * We do not have to fixup the clean/dirty bits here... we can 523 * allow the pager to do it after the I/O completes. 524 * 525 * NOTE! mc[i]->dirty may be partial or fragmented due to an 526 * edge case with file fragments. 527 */ 528 for (i = 0; i < count; i++) { 529 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, 530 ("vm_pageout_flush: partially invalid page %p index %d/%d", 531 mc[i], i, count)); 532 vm_page_sbusy(mc[i]); 533 pmap_remove_write(mc[i]); 534 } 535 vm_object_pip_add(object, count); 536 537 vm_pager_put_pages(object, mc, count, flags, pageout_status); 538 539 runlen = count - mreq; 540 if (eio != NULL) 541 *eio = FALSE; 542 for (i = 0; i < count; i++) { 543 vm_page_t mt = mc[i]; 544 545 KASSERT(pageout_status[i] == VM_PAGER_PEND || 546 !pmap_page_is_write_mapped(mt), 547 ("vm_pageout_flush: page %p is not write protected", mt)); 548 switch (pageout_status[i]) { 549 case VM_PAGER_OK: 550 case VM_PAGER_PEND: 551 numpagedout++; 552 break; 553 case VM_PAGER_BAD: 554 /* 555 * Page outside of range of object. Right now we 556 * essentially lose the changes by pretending it 557 * worked. 558 */ 559 vm_page_undirty(mt); 560 break; 561 case VM_PAGER_ERROR: 562 case VM_PAGER_FAIL: 563 /* 564 * If page couldn't be paged out, then reactivate the 565 * page so it doesn't clog the inactive list. (We 566 * will try paging out it again later). 567 */ 568 vm_page_lock(mt); 569 vm_page_activate(mt); 570 vm_page_unlock(mt); 571 if (eio != NULL && i >= mreq && i - mreq < runlen) 572 *eio = TRUE; 573 break; 574 case VM_PAGER_AGAIN: 575 if (i >= mreq && i - mreq < runlen) 576 runlen = i - mreq; 577 break; 578 } 579 580 /* 581 * If the operation is still going, leave the page busy to 582 * block all other accesses. Also, leave the paging in 583 * progress indicator set so that we don't attempt an object 584 * collapse. 585 */ 586 if (pageout_status[i] != VM_PAGER_PEND) { 587 vm_object_pip_wakeup(object); 588 vm_page_sunbusy(mt); 589 } 590 } 591 if (prunlen != NULL) 592 *prunlen = runlen; 593 return (numpagedout); 594 } 595 596 #if !defined(NO_SWAPPING) 597 /* 598 * vm_pageout_object_deactivate_pages 599 * 600 * Deactivate enough pages to satisfy the inactive target 601 * requirements. 602 * 603 * The object and map must be locked. 604 */ 605 static void 606 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 607 long desired) 608 { 609 vm_object_t backing_object, object; 610 vm_page_t p; 611 int act_delta, remove_mode; 612 613 VM_OBJECT_ASSERT_LOCKED(first_object); 614 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 615 return; 616 for (object = first_object;; object = backing_object) { 617 if (pmap_resident_count(pmap) <= desired) 618 goto unlock_return; 619 VM_OBJECT_ASSERT_LOCKED(object); 620 if ((object->flags & OBJ_UNMANAGED) != 0 || 621 object->paging_in_progress != 0) 622 goto unlock_return; 623 624 remove_mode = 0; 625 if (object->shadow_count > 1) 626 remove_mode = 1; 627 /* 628 * Scan the object's entire memory queue. 629 */ 630 TAILQ_FOREACH(p, &object->memq, listq) { 631 if (pmap_resident_count(pmap) <= desired) 632 goto unlock_return; 633 if (vm_page_busied(p)) 634 continue; 635 PCPU_INC(cnt.v_pdpages); 636 vm_page_lock(p); 637 if (p->wire_count != 0 || p->hold_count != 0 || 638 !pmap_page_exists_quick(pmap, p)) { 639 vm_page_unlock(p); 640 continue; 641 } 642 act_delta = pmap_ts_referenced(p); 643 if ((p->aflags & PGA_REFERENCED) != 0) { 644 if (act_delta == 0) 645 act_delta = 1; 646 vm_page_aflag_clear(p, PGA_REFERENCED); 647 } 648 if (p->queue != PQ_ACTIVE && act_delta != 0) { 649 vm_page_activate(p); 650 p->act_count += act_delta; 651 } else if (p->queue == PQ_ACTIVE) { 652 if (act_delta == 0) { 653 p->act_count -= min(p->act_count, 654 ACT_DECLINE); 655 if (!remove_mode && p->act_count == 0) { 656 pmap_remove_all(p); 657 vm_page_deactivate(p); 658 } else 659 vm_page_requeue(p); 660 } else { 661 vm_page_activate(p); 662 if (p->act_count < ACT_MAX - 663 ACT_ADVANCE) 664 p->act_count += ACT_ADVANCE; 665 vm_page_requeue(p); 666 } 667 } else if (p->queue == PQ_INACTIVE) 668 pmap_remove_all(p); 669 vm_page_unlock(p); 670 } 671 if ((backing_object = object->backing_object) == NULL) 672 goto unlock_return; 673 VM_OBJECT_RLOCK(backing_object); 674 if (object != first_object) 675 VM_OBJECT_RUNLOCK(object); 676 } 677 unlock_return: 678 if (object != first_object) 679 VM_OBJECT_RUNLOCK(object); 680 } 681 682 /* 683 * deactivate some number of pages in a map, try to do it fairly, but 684 * that is really hard to do. 685 */ 686 static void 687 vm_pageout_map_deactivate_pages(map, desired) 688 vm_map_t map; 689 long desired; 690 { 691 vm_map_entry_t tmpe; 692 vm_object_t obj, bigobj; 693 int nothingwired; 694 695 if (!vm_map_trylock(map)) 696 return; 697 698 bigobj = NULL; 699 nothingwired = TRUE; 700 701 /* 702 * first, search out the biggest object, and try to free pages from 703 * that. 704 */ 705 tmpe = map->header.next; 706 while (tmpe != &map->header) { 707 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 708 obj = tmpe->object.vm_object; 709 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 710 if (obj->shadow_count <= 1 && 711 (bigobj == NULL || 712 bigobj->resident_page_count < obj->resident_page_count)) { 713 if (bigobj != NULL) 714 VM_OBJECT_RUNLOCK(bigobj); 715 bigobj = obj; 716 } else 717 VM_OBJECT_RUNLOCK(obj); 718 } 719 } 720 if (tmpe->wired_count > 0) 721 nothingwired = FALSE; 722 tmpe = tmpe->next; 723 } 724 725 if (bigobj != NULL) { 726 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired); 727 VM_OBJECT_RUNLOCK(bigobj); 728 } 729 /* 730 * Next, hunt around for other pages to deactivate. We actually 731 * do this search sort of wrong -- .text first is not the best idea. 732 */ 733 tmpe = map->header.next; 734 while (tmpe != &map->header) { 735 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 736 break; 737 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 738 obj = tmpe->object.vm_object; 739 if (obj != NULL) { 740 VM_OBJECT_RLOCK(obj); 741 vm_pageout_object_deactivate_pages(map->pmap, obj, desired); 742 VM_OBJECT_RUNLOCK(obj); 743 } 744 } 745 tmpe = tmpe->next; 746 } 747 748 /* 749 * Remove all mappings if a process is swapped out, this will free page 750 * table pages. 751 */ 752 if (desired == 0 && nothingwired) { 753 pmap_remove(vm_map_pmap(map), vm_map_min(map), 754 vm_map_max(map)); 755 } 756 757 vm_map_unlock(map); 758 } 759 #endif /* !defined(NO_SWAPPING) */ 760 761 /* 762 * Attempt to acquire all of the necessary locks to launder a page and 763 * then call through the clustering layer to PUTPAGES. Wait a short 764 * time for a vnode lock. 765 * 766 * Requires the page and object lock on entry, releases both before return. 767 * Returns 0 on success and an errno otherwise. 768 */ 769 static int 770 vm_pageout_clean(vm_page_t m) 771 { 772 struct vnode *vp; 773 struct mount *mp; 774 vm_object_t object; 775 vm_pindex_t pindex; 776 int error, lockmode; 777 778 vm_page_assert_locked(m); 779 object = m->object; 780 VM_OBJECT_ASSERT_WLOCKED(object); 781 error = 0; 782 vp = NULL; 783 mp = NULL; 784 785 /* 786 * The object is already known NOT to be dead. It 787 * is possible for the vget() to block the whole 788 * pageout daemon, but the new low-memory handling 789 * code should prevent it. 790 * 791 * We can't wait forever for the vnode lock, we might 792 * deadlock due to a vn_read() getting stuck in 793 * vm_wait while holding this vnode. We skip the 794 * vnode if we can't get it in a reasonable amount 795 * of time. 796 */ 797 if (object->type == OBJT_VNODE) { 798 vm_page_unlock(m); 799 vp = object->handle; 800 if (vp->v_type == VREG && 801 vn_start_write(vp, &mp, V_NOWAIT) != 0) { 802 mp = NULL; 803 error = EDEADLK; 804 goto unlock_all; 805 } 806 KASSERT(mp != NULL, 807 ("vp %p with NULL v_mount", vp)); 808 vm_object_reference_locked(object); 809 pindex = m->pindex; 810 VM_OBJECT_WUNLOCK(object); 811 lockmode = MNT_SHARED_WRITES(vp->v_mount) ? 812 LK_SHARED : LK_EXCLUSIVE; 813 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) { 814 vp = NULL; 815 error = EDEADLK; 816 goto unlock_mp; 817 } 818 VM_OBJECT_WLOCK(object); 819 vm_page_lock(m); 820 /* 821 * While the object and page were unlocked, the page 822 * may have been: 823 * (1) moved to a different queue, 824 * (2) reallocated to a different object, 825 * (3) reallocated to a different offset, or 826 * (4) cleaned. 827 */ 828 if (m->queue != PQ_INACTIVE || m->object != object || 829 m->pindex != pindex || m->dirty == 0) { 830 vm_page_unlock(m); 831 error = ENXIO; 832 goto unlock_all; 833 } 834 835 /* 836 * The page may have been busied or held while the object 837 * and page locks were released. 838 */ 839 if (vm_page_busied(m) || m->hold_count != 0) { 840 vm_page_unlock(m); 841 error = EBUSY; 842 goto unlock_all; 843 } 844 } 845 846 /* 847 * If a page is dirty, then it is either being washed 848 * (but not yet cleaned) or it is still in the 849 * laundry. If it is still in the laundry, then we 850 * start the cleaning operation. 851 */ 852 if (vm_pageout_cluster(m) == 0) 853 error = EIO; 854 855 unlock_all: 856 VM_OBJECT_WUNLOCK(object); 857 858 unlock_mp: 859 vm_page_lock_assert(m, MA_NOTOWNED); 860 if (mp != NULL) { 861 if (vp != NULL) 862 vput(vp); 863 vm_object_deallocate(object); 864 vn_finished_write(mp); 865 } 866 867 return (error); 868 } 869 870 /* 871 * vm_pageout_scan does the dirty work for the pageout daemon. 872 * 873 * pass 0 - Update active LRU/deactivate pages 874 * pass 1 - Free inactive pages 875 * pass 2 - Launder dirty pages 876 */ 877 static void 878 vm_pageout_scan(struct vm_domain *vmd, int pass) 879 { 880 vm_page_t m, next; 881 struct vm_pagequeue *pq; 882 vm_object_t object; 883 long min_scan; 884 int act_delta, addl_page_shortage, deficit, error, maxlaunder, maxscan; 885 int page_shortage, scan_tick, scanned, starting_page_shortage; 886 int vnodes_skipped; 887 boolean_t pageout_ok, queues_locked; 888 889 /* 890 * If we need to reclaim memory ask kernel caches to return 891 * some. We rate limit to avoid thrashing. 892 */ 893 if (vmd == &vm_dom[0] && pass > 0 && 894 (time_uptime - lowmem_uptime) >= lowmem_period) { 895 /* 896 * Decrease registered cache sizes. 897 */ 898 SDT_PROBE0(vm, , , vm__lowmem_scan); 899 EVENTHANDLER_INVOKE(vm_lowmem, 0); 900 /* 901 * We do this explicitly after the caches have been 902 * drained above. 903 */ 904 uma_reclaim(); 905 lowmem_uptime = time_uptime; 906 } 907 908 /* 909 * The addl_page_shortage is the number of temporarily 910 * stuck pages in the inactive queue. In other words, the 911 * number of pages from the inactive count that should be 912 * discounted in setting the target for the active queue scan. 913 */ 914 addl_page_shortage = 0; 915 916 /* 917 * Calculate the number of pages that we want to free. 918 */ 919 if (pass > 0) { 920 deficit = atomic_readandclear_int(&vm_pageout_deficit); 921 page_shortage = vm_paging_target() + deficit; 922 } else 923 page_shortage = deficit = 0; 924 starting_page_shortage = page_shortage; 925 926 /* 927 * maxlaunder limits the number of dirty pages we flush per scan. 928 * For most systems a smaller value (16 or 32) is more robust under 929 * extreme memory and disk pressure because any unnecessary writes 930 * to disk can result in extreme performance degredation. However, 931 * systems with excessive dirty pages (especially when MAP_NOSYNC is 932 * used) will die horribly with limited laundering. If the pageout 933 * daemon cannot clean enough pages in the first pass, we let it go 934 * all out in succeeding passes. 935 */ 936 if ((maxlaunder = vm_max_launder) <= 1) 937 maxlaunder = 1; 938 if (pass > 1) 939 maxlaunder = 10000; 940 941 vnodes_skipped = 0; 942 943 /* 944 * Start scanning the inactive queue for pages that we can free. The 945 * scan will stop when we reach the target or we have scanned the 946 * entire queue. (Note that m->act_count is not used to make 947 * decisions for the inactive queue, only for the active queue.) 948 */ 949 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 950 maxscan = pq->pq_cnt; 951 vm_pagequeue_lock(pq); 952 queues_locked = TRUE; 953 for (m = TAILQ_FIRST(&pq->pq_pl); 954 m != NULL && maxscan-- > 0 && page_shortage > 0; 955 m = next) { 956 vm_pagequeue_assert_locked(pq); 957 KASSERT(queues_locked, ("unlocked queues")); 958 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m)); 959 960 PCPU_INC(cnt.v_pdpages); 961 next = TAILQ_NEXT(m, plinks.q); 962 963 /* 964 * skip marker pages 965 */ 966 if (m->flags & PG_MARKER) 967 continue; 968 969 KASSERT((m->flags & PG_FICTITIOUS) == 0, 970 ("Fictitious page %p cannot be in inactive queue", m)); 971 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 972 ("Unmanaged page %p cannot be in inactive queue", m)); 973 974 /* 975 * The page or object lock acquisitions fail if the 976 * page was removed from the queue or moved to a 977 * different position within the queue. In either 978 * case, addl_page_shortage should not be incremented. 979 */ 980 if (!vm_pageout_page_lock(m, &next)) 981 goto unlock_page; 982 else if (m->hold_count != 0) { 983 /* 984 * Held pages are essentially stuck in the 985 * queue. So, they ought to be discounted 986 * from the inactive count. See the 987 * calculation of the page_shortage for the 988 * loop over the active queue below. 989 */ 990 addl_page_shortage++; 991 goto unlock_page; 992 } 993 object = m->object; 994 if (!VM_OBJECT_TRYWLOCK(object)) { 995 if (!vm_pageout_fallback_object_lock(m, &next)) 996 goto unlock_object; 997 else if (m->hold_count != 0) { 998 addl_page_shortage++; 999 goto unlock_object; 1000 } 1001 } 1002 if (vm_page_busied(m)) { 1003 /* 1004 * Don't mess with busy pages. Leave them at 1005 * the front of the queue. Most likely, they 1006 * are being paged out and will leave the 1007 * queue shortly after the scan finishes. So, 1008 * they ought to be discounted from the 1009 * inactive count. 1010 */ 1011 addl_page_shortage++; 1012 unlock_object: 1013 VM_OBJECT_WUNLOCK(object); 1014 unlock_page: 1015 vm_page_unlock(m); 1016 continue; 1017 } 1018 KASSERT(m->hold_count == 0, ("Held page %p", m)); 1019 1020 /* 1021 * We unlock the inactive page queue, invalidating the 1022 * 'next' pointer. Use our marker to remember our 1023 * place. 1024 */ 1025 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q); 1026 vm_pagequeue_unlock(pq); 1027 queues_locked = FALSE; 1028 1029 /* 1030 * Invalid pages can be easily freed. They cannot be 1031 * mapped, vm_page_free() asserts this. 1032 */ 1033 if (m->valid == 0) 1034 goto free_page; 1035 1036 /* 1037 * If the page has been referenced and the object is not dead, 1038 * reactivate or requeue the page depending on whether the 1039 * object is mapped. 1040 */ 1041 if ((m->aflags & PGA_REFERENCED) != 0) { 1042 vm_page_aflag_clear(m, PGA_REFERENCED); 1043 act_delta = 1; 1044 } else 1045 act_delta = 0; 1046 if (object->ref_count != 0) { 1047 act_delta += pmap_ts_referenced(m); 1048 } else { 1049 KASSERT(!pmap_page_is_mapped(m), 1050 ("vm_pageout_scan: page %p is mapped", m)); 1051 } 1052 if (act_delta != 0) { 1053 if (object->ref_count != 0) { 1054 vm_page_activate(m); 1055 1056 /* 1057 * Increase the activation count if the page 1058 * was referenced while in the inactive queue. 1059 * This makes it less likely that the page will 1060 * be returned prematurely to the inactive 1061 * queue. 1062 */ 1063 m->act_count += act_delta + ACT_ADVANCE; 1064 goto drop_page; 1065 } else if ((object->flags & OBJ_DEAD) == 0) 1066 goto requeue_page; 1067 } 1068 1069 /* 1070 * If the page appears to be clean at the machine-independent 1071 * layer, then remove all of its mappings from the pmap in 1072 * anticipation of freeing it. If, however, any of the page's 1073 * mappings allow write access, then the page may still be 1074 * modified until the last of those mappings are removed. 1075 */ 1076 if (object->ref_count != 0) { 1077 vm_page_test_dirty(m); 1078 if (m->dirty == 0) 1079 pmap_remove_all(m); 1080 } 1081 1082 if (m->dirty == 0) { 1083 /* 1084 * Clean pages can be freed. 1085 */ 1086 free_page: 1087 vm_page_free(m); 1088 PCPU_INC(cnt.v_dfree); 1089 --page_shortage; 1090 } else if ((object->flags & OBJ_DEAD) != 0) { 1091 /* 1092 * Leave dirty pages from dead objects at the front of 1093 * the queue. They are being paged out and freed by 1094 * the thread that destroyed the object. They will 1095 * leave the queue shortly after the scan finishes, so 1096 * they should be discounted from the inactive count. 1097 */ 1098 addl_page_shortage++; 1099 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) { 1100 /* 1101 * Dirty pages need to be paged out, but flushing 1102 * a page is extremely expensive versus freeing 1103 * a clean page. Rather then artificially limiting 1104 * the number of pages we can flush, we instead give 1105 * dirty pages extra priority on the inactive queue 1106 * by forcing them to be cycled through the queue 1107 * twice before being flushed, after which the 1108 * (now clean) page will cycle through once more 1109 * before being freed. This significantly extends 1110 * the thrash point for a heavily loaded machine. 1111 */ 1112 m->flags |= PG_WINATCFLS; 1113 requeue_page: 1114 vm_pagequeue_lock(pq); 1115 queues_locked = TRUE; 1116 vm_page_requeue_locked(m); 1117 } else if (maxlaunder > 0) { 1118 /* 1119 * We always want to try to flush some dirty pages if 1120 * we encounter them, to keep the system stable. 1121 * Normally this number is small, but under extreme 1122 * pressure where there are insufficient clean pages 1123 * on the inactive queue, we may have to go all out. 1124 */ 1125 1126 if (object->type != OBJT_SWAP && 1127 object->type != OBJT_DEFAULT) 1128 pageout_ok = TRUE; 1129 else if (disable_swap_pageouts) 1130 pageout_ok = FALSE; 1131 else if (defer_swap_pageouts) 1132 pageout_ok = vm_page_count_min(); 1133 else 1134 pageout_ok = TRUE; 1135 if (!pageout_ok) 1136 goto requeue_page; 1137 error = vm_pageout_clean(m); 1138 /* 1139 * Decrement page_shortage on success to account for 1140 * the (future) cleaned page. Otherwise we could wind 1141 * up laundering or cleaning too many pages. 1142 */ 1143 if (error == 0) { 1144 page_shortage--; 1145 maxlaunder--; 1146 } else if (error == EDEADLK) { 1147 pageout_lock_miss++; 1148 vnodes_skipped++; 1149 } else if (error == EBUSY) { 1150 addl_page_shortage++; 1151 } 1152 vm_page_lock_assert(m, MA_NOTOWNED); 1153 goto relock_queues; 1154 } 1155 drop_page: 1156 vm_page_unlock(m); 1157 VM_OBJECT_WUNLOCK(object); 1158 relock_queues: 1159 if (!queues_locked) { 1160 vm_pagequeue_lock(pq); 1161 queues_locked = TRUE; 1162 } 1163 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q); 1164 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q); 1165 } 1166 vm_pagequeue_unlock(pq); 1167 1168 #if !defined(NO_SWAPPING) 1169 /* 1170 * Wakeup the swapout daemon if we didn't free the targeted number of 1171 * pages. 1172 */ 1173 if (vm_swap_enabled && page_shortage > 0) 1174 vm_req_vmdaemon(VM_SWAP_NORMAL); 1175 #endif 1176 1177 /* 1178 * Wakeup the sync daemon if we skipped a vnode in a writeable object 1179 * and we didn't free enough pages. 1180 */ 1181 if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target - 1182 vm_cnt.v_free_min) 1183 (void)speedup_syncer(); 1184 1185 /* 1186 * If the inactive queue scan fails repeatedly to meet its 1187 * target, kill the largest process. 1188 */ 1189 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1190 1191 /* 1192 * Compute the number of pages we want to try to move from the 1193 * active queue to the inactive queue. 1194 */ 1195 page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count + 1196 vm_paging_target() + deficit + addl_page_shortage; 1197 1198 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1199 vm_pagequeue_lock(pq); 1200 maxscan = pq->pq_cnt; 1201 1202 /* 1203 * If we're just idle polling attempt to visit every 1204 * active page within 'update_period' seconds. 1205 */ 1206 scan_tick = ticks; 1207 if (vm_pageout_update_period != 0) { 1208 min_scan = pq->pq_cnt; 1209 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1210 min_scan /= hz * vm_pageout_update_period; 1211 } else 1212 min_scan = 0; 1213 if (min_scan > 0 || (page_shortage > 0 && maxscan > 0)) 1214 vmd->vmd_last_active_scan = scan_tick; 1215 1216 /* 1217 * Scan the active queue for pages that can be deactivated. Update 1218 * the per-page activity counter and use it to identify deactivation 1219 * candidates. 1220 */ 1221 for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned < 1222 min_scan || (page_shortage > 0 && scanned < maxscan)); m = next, 1223 scanned++) { 1224 1225 KASSERT(m->queue == PQ_ACTIVE, 1226 ("vm_pageout_scan: page %p isn't active", m)); 1227 1228 next = TAILQ_NEXT(m, plinks.q); 1229 if ((m->flags & PG_MARKER) != 0) 1230 continue; 1231 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1232 ("Fictitious page %p cannot be in active queue", m)); 1233 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1234 ("Unmanaged page %p cannot be in active queue", m)); 1235 if (!vm_pageout_page_lock(m, &next)) { 1236 vm_page_unlock(m); 1237 continue; 1238 } 1239 1240 /* 1241 * The count for pagedaemon pages is done after checking the 1242 * page for eligibility... 1243 */ 1244 PCPU_INC(cnt.v_pdpages); 1245 1246 /* 1247 * Check to see "how much" the page has been used. 1248 */ 1249 if ((m->aflags & PGA_REFERENCED) != 0) { 1250 vm_page_aflag_clear(m, PGA_REFERENCED); 1251 act_delta = 1; 1252 } else 1253 act_delta = 0; 1254 1255 /* 1256 * Unlocked object ref count check. Two races are possible. 1257 * 1) The ref was transitioning to zero and we saw non-zero, 1258 * the pmap bits will be checked unnecessarily. 1259 * 2) The ref was transitioning to one and we saw zero. 1260 * The page lock prevents a new reference to this page so 1261 * we need not check the reference bits. 1262 */ 1263 if (m->object->ref_count != 0) 1264 act_delta += pmap_ts_referenced(m); 1265 1266 /* 1267 * Advance or decay the act_count based on recent usage. 1268 */ 1269 if (act_delta != 0) { 1270 m->act_count += ACT_ADVANCE + act_delta; 1271 if (m->act_count > ACT_MAX) 1272 m->act_count = ACT_MAX; 1273 } else 1274 m->act_count -= min(m->act_count, ACT_DECLINE); 1275 1276 /* 1277 * Move this page to the tail of the active or inactive 1278 * queue depending on usage. 1279 */ 1280 if (m->act_count == 0) { 1281 /* Dequeue to avoid later lock recursion. */ 1282 vm_page_dequeue_locked(m); 1283 vm_page_deactivate(m); 1284 page_shortage--; 1285 } else 1286 vm_page_requeue_locked(m); 1287 vm_page_unlock(m); 1288 } 1289 vm_pagequeue_unlock(pq); 1290 #if !defined(NO_SWAPPING) 1291 /* 1292 * Idle process swapout -- run once per second. 1293 */ 1294 if (vm_swap_idle_enabled) { 1295 static long lsec; 1296 if (time_second != lsec) { 1297 vm_req_vmdaemon(VM_SWAP_IDLE); 1298 lsec = time_second; 1299 } 1300 } 1301 #endif 1302 } 1303 1304 static int vm_pageout_oom_vote; 1305 1306 /* 1307 * The pagedaemon threads randlomly select one to perform the 1308 * OOM. Trying to kill processes before all pagedaemons 1309 * failed to reach free target is premature. 1310 */ 1311 static void 1312 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1313 int starting_page_shortage) 1314 { 1315 int old_vote; 1316 1317 if (starting_page_shortage <= 0 || starting_page_shortage != 1318 page_shortage) 1319 vmd->vmd_oom_seq = 0; 1320 else 1321 vmd->vmd_oom_seq++; 1322 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1323 if (vmd->vmd_oom) { 1324 vmd->vmd_oom = FALSE; 1325 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1326 } 1327 return; 1328 } 1329 1330 /* 1331 * Do not follow the call sequence until OOM condition is 1332 * cleared. 1333 */ 1334 vmd->vmd_oom_seq = 0; 1335 1336 if (vmd->vmd_oom) 1337 return; 1338 1339 vmd->vmd_oom = TRUE; 1340 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1341 if (old_vote != vm_ndomains - 1) 1342 return; 1343 1344 /* 1345 * The current pagedaemon thread is the last in the quorum to 1346 * start OOM. Initiate the selection and signaling of the 1347 * victim. 1348 */ 1349 vm_pageout_oom(VM_OOM_MEM); 1350 1351 /* 1352 * After one round of OOM terror, recall our vote. On the 1353 * next pass, current pagedaemon would vote again if the low 1354 * memory condition is still there, due to vmd_oom being 1355 * false. 1356 */ 1357 vmd->vmd_oom = FALSE; 1358 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1359 } 1360 1361 /* 1362 * The OOM killer is the page daemon's action of last resort when 1363 * memory allocation requests have been stalled for a prolonged period 1364 * of time because it cannot reclaim memory. This function computes 1365 * the approximate number of physical pages that could be reclaimed if 1366 * the specified address space is destroyed. 1367 * 1368 * Private, anonymous memory owned by the address space is the 1369 * principal resource that we expect to recover after an OOM kill. 1370 * Since the physical pages mapped by the address space's COW entries 1371 * are typically shared pages, they are unlikely to be released and so 1372 * they are not counted. 1373 * 1374 * To get to the point where the page daemon runs the OOM killer, its 1375 * efforts to write-back vnode-backed pages may have stalled. This 1376 * could be caused by a memory allocation deadlock in the write path 1377 * that might be resolved by an OOM kill. Therefore, physical pages 1378 * belonging to vnode-backed objects are counted, because they might 1379 * be freed without being written out first if the address space holds 1380 * the last reference to an unlinked vnode. 1381 * 1382 * Similarly, physical pages belonging to OBJT_PHYS objects are 1383 * counted because the address space might hold the last reference to 1384 * the object. 1385 */ 1386 static long 1387 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1388 { 1389 vm_map_t map; 1390 vm_map_entry_t entry; 1391 vm_object_t obj; 1392 long res; 1393 1394 map = &vmspace->vm_map; 1395 KASSERT(!map->system_map, ("system map")); 1396 sx_assert(&map->lock, SA_LOCKED); 1397 res = 0; 1398 for (entry = map->header.next; entry != &map->header; 1399 entry = entry->next) { 1400 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1401 continue; 1402 obj = entry->object.vm_object; 1403 if (obj == NULL) 1404 continue; 1405 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1406 obj->ref_count != 1) 1407 continue; 1408 switch (obj->type) { 1409 case OBJT_DEFAULT: 1410 case OBJT_SWAP: 1411 case OBJT_PHYS: 1412 case OBJT_VNODE: 1413 res += obj->resident_page_count; 1414 break; 1415 } 1416 } 1417 return (res); 1418 } 1419 1420 void 1421 vm_pageout_oom(int shortage) 1422 { 1423 struct proc *p, *bigproc; 1424 vm_offset_t size, bigsize; 1425 struct thread *td; 1426 struct vmspace *vm; 1427 1428 /* 1429 * We keep the process bigproc locked once we find it to keep anyone 1430 * from messing with it; however, there is a possibility of 1431 * deadlock if process B is bigproc and one of it's child processes 1432 * attempts to propagate a signal to B while we are waiting for A's 1433 * lock while walking this list. To avoid this, we don't block on 1434 * the process lock but just skip a process if it is already locked. 1435 */ 1436 bigproc = NULL; 1437 bigsize = 0; 1438 sx_slock(&allproc_lock); 1439 FOREACH_PROC_IN_SYSTEM(p) { 1440 int breakout; 1441 1442 PROC_LOCK(p); 1443 1444 /* 1445 * If this is a system, protected or killed process, skip it. 1446 */ 1447 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1448 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1449 p->p_pid == 1 || P_KILLED(p) || 1450 (p->p_pid < 48 && swap_pager_avail != 0)) { 1451 PROC_UNLOCK(p); 1452 continue; 1453 } 1454 /* 1455 * If the process is in a non-running type state, 1456 * don't touch it. Check all the threads individually. 1457 */ 1458 breakout = 0; 1459 FOREACH_THREAD_IN_PROC(p, td) { 1460 thread_lock(td); 1461 if (!TD_ON_RUNQ(td) && 1462 !TD_IS_RUNNING(td) && 1463 !TD_IS_SLEEPING(td) && 1464 !TD_IS_SUSPENDED(td) && 1465 !TD_IS_SWAPPED(td)) { 1466 thread_unlock(td); 1467 breakout = 1; 1468 break; 1469 } 1470 thread_unlock(td); 1471 } 1472 if (breakout) { 1473 PROC_UNLOCK(p); 1474 continue; 1475 } 1476 /* 1477 * get the process size 1478 */ 1479 vm = vmspace_acquire_ref(p); 1480 if (vm == NULL) { 1481 PROC_UNLOCK(p); 1482 continue; 1483 } 1484 _PHOLD_LITE(p); 1485 PROC_UNLOCK(p); 1486 sx_sunlock(&allproc_lock); 1487 if (!vm_map_trylock_read(&vm->vm_map)) { 1488 vmspace_free(vm); 1489 sx_slock(&allproc_lock); 1490 PRELE(p); 1491 continue; 1492 } 1493 size = vmspace_swap_count(vm); 1494 if (shortage == VM_OOM_MEM) 1495 size += vm_pageout_oom_pagecount(vm); 1496 vm_map_unlock_read(&vm->vm_map); 1497 vmspace_free(vm); 1498 sx_slock(&allproc_lock); 1499 1500 /* 1501 * If this process is bigger than the biggest one, 1502 * remember it. 1503 */ 1504 if (size > bigsize) { 1505 if (bigproc != NULL) 1506 PRELE(bigproc); 1507 bigproc = p; 1508 bigsize = size; 1509 } else { 1510 PRELE(p); 1511 } 1512 } 1513 sx_sunlock(&allproc_lock); 1514 if (bigproc != NULL) { 1515 if (vm_panic_on_oom != 0) 1516 panic("out of swap space"); 1517 PROC_LOCK(bigproc); 1518 killproc(bigproc, "out of swap space"); 1519 sched_nice(bigproc, PRIO_MIN); 1520 _PRELE(bigproc); 1521 PROC_UNLOCK(bigproc); 1522 wakeup(&vm_cnt.v_free_count); 1523 } 1524 } 1525 1526 static void 1527 vm_pageout_worker(void *arg) 1528 { 1529 struct vm_domain *domain; 1530 int domidx; 1531 1532 domidx = (uintptr_t)arg; 1533 domain = &vm_dom[domidx]; 1534 1535 /* 1536 * XXXKIB It could be useful to bind pageout daemon threads to 1537 * the cores belonging to the domain, from which vm_page_array 1538 * is allocated. 1539 */ 1540 1541 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1542 domain->vmd_last_active_scan = ticks; 1543 vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE); 1544 vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE); 1545 TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl, 1546 &domain->vmd_inacthead, plinks.q); 1547 1548 /* 1549 * The pageout daemon worker is never done, so loop forever. 1550 */ 1551 while (TRUE) { 1552 mtx_lock(&vm_page_queue_free_mtx); 1553 1554 /* 1555 * Generally, after a level >= 1 scan, if there are enough 1556 * free pages to wakeup the waiters, then they are already 1557 * awake. A call to vm_page_free() during the scan awakened 1558 * them. However, in the following case, this wakeup serves 1559 * to bound the amount of time that a thread might wait. 1560 * Suppose a thread's call to vm_page_alloc() fails, but 1561 * before that thread calls VM_WAIT, enough pages are freed by 1562 * other threads to alleviate the free page shortage. The 1563 * thread will, nonetheless, wait until another page is freed 1564 * or this wakeup is performed. 1565 */ 1566 if (vm_pages_needed && !vm_page_count_min()) { 1567 vm_pages_needed = false; 1568 wakeup(&vm_cnt.v_free_count); 1569 } 1570 1571 /* 1572 * Do not clear vm_pageout_wanted until we reach our target. 1573 * Otherwise, we may be awakened over and over again, wasting 1574 * CPU time. 1575 */ 1576 if (vm_pageout_wanted && !vm_paging_needed()) 1577 vm_pageout_wanted = false; 1578 1579 /* 1580 * Might the page daemon receive a wakeup call? 1581 */ 1582 if (vm_pageout_wanted) { 1583 /* 1584 * No. Either vm_pageout_wanted was set by another 1585 * thread during the previous scan, which must have 1586 * been a level 0 scan, or vm_pageout_wanted was 1587 * already set and the scan failed to free enough 1588 * pages. If we haven't yet performed a level >= 2 1589 * scan (unlimited dirty cleaning), then upgrade the 1590 * level and scan again now. Otherwise, sleep a bit 1591 * and try again later. 1592 */ 1593 mtx_unlock(&vm_page_queue_free_mtx); 1594 if (domain->vmd_pass > 1) 1595 pause("psleep", hz / 2); 1596 domain->vmd_pass++; 1597 } else { 1598 /* 1599 * Yes. Sleep until pages need to be reclaimed or 1600 * have their reference stats updated. 1601 */ 1602 if (mtx_sleep(&vm_pageout_wanted, 1603 &vm_page_queue_free_mtx, PDROP | PVM, "psleep", 1604 hz) == 0) { 1605 PCPU_INC(cnt.v_pdwakeups); 1606 domain->vmd_pass = 1; 1607 } else 1608 domain->vmd_pass = 0; 1609 } 1610 1611 vm_pageout_scan(domain, domain->vmd_pass); 1612 } 1613 } 1614 1615 /* 1616 * vm_pageout_init initialises basic pageout daemon settings. 1617 */ 1618 static void 1619 vm_pageout_init(void) 1620 { 1621 /* 1622 * Initialize some paging parameters. 1623 */ 1624 vm_cnt.v_interrupt_free_min = 2; 1625 if (vm_cnt.v_page_count < 2000) 1626 vm_pageout_page_count = 8; 1627 1628 /* 1629 * v_free_reserved needs to include enough for the largest 1630 * swap pager structures plus enough for any pv_entry structs 1631 * when paging. 1632 */ 1633 if (vm_cnt.v_page_count > 1024) 1634 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200; 1635 else 1636 vm_cnt.v_free_min = 4; 1637 vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 1638 vm_cnt.v_interrupt_free_min; 1639 vm_cnt.v_free_reserved = vm_pageout_page_count + 1640 vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768); 1641 vm_cnt.v_free_severe = vm_cnt.v_free_min / 2; 1642 vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved; 1643 vm_cnt.v_free_min += vm_cnt.v_free_reserved; 1644 vm_cnt.v_free_severe += vm_cnt.v_free_reserved; 1645 vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2; 1646 if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3) 1647 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3; 1648 1649 /* 1650 * Set the default wakeup threshold to be 10% above the minimum 1651 * page limit. This keeps the steady state out of shortfall. 1652 */ 1653 vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11; 1654 1655 /* 1656 * Set interval in seconds for active scan. We want to visit each 1657 * page at least once every ten minutes. This is to prevent worst 1658 * case paging behaviors with stale active LRU. 1659 */ 1660 if (vm_pageout_update_period == 0) 1661 vm_pageout_update_period = 600; 1662 1663 /* XXX does not really belong here */ 1664 if (vm_page_max_wired == 0) 1665 vm_page_max_wired = vm_cnt.v_free_count / 3; 1666 } 1667 1668 /* 1669 * vm_pageout is the high level pageout daemon. 1670 */ 1671 static void 1672 vm_pageout(void) 1673 { 1674 int error; 1675 #ifdef VM_NUMA_ALLOC 1676 int i; 1677 #endif 1678 1679 swap_pager_swap_init(); 1680 #ifdef VM_NUMA_ALLOC 1681 for (i = 1; i < vm_ndomains; i++) { 1682 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i, 1683 curproc, NULL, 0, 0, "dom%d", i); 1684 if (error != 0) { 1685 panic("starting pageout for domain %d, error %d\n", 1686 i, error); 1687 } 1688 } 1689 #endif 1690 error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL, 1691 0, 0, "uma"); 1692 if (error != 0) 1693 panic("starting uma_reclaim helper, error %d\n", error); 1694 vm_pageout_worker((void *)(uintptr_t)0); 1695 } 1696 1697 /* 1698 * Unless the free page queue lock is held by the caller, this function 1699 * should be regarded as advisory. Specifically, the caller should 1700 * not msleep() on &vm_cnt.v_free_count following this function unless 1701 * the free page queue lock is held until the msleep() is performed. 1702 */ 1703 void 1704 pagedaemon_wakeup(void) 1705 { 1706 1707 if (!vm_pageout_wanted && curthread->td_proc != pageproc) { 1708 vm_pageout_wanted = true; 1709 wakeup(&vm_pageout_wanted); 1710 } 1711 } 1712 1713 #if !defined(NO_SWAPPING) 1714 static void 1715 vm_req_vmdaemon(int req) 1716 { 1717 static int lastrun = 0; 1718 1719 mtx_lock(&vm_daemon_mtx); 1720 vm_pageout_req_swapout |= req; 1721 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 1722 wakeup(&vm_daemon_needed); 1723 lastrun = ticks; 1724 } 1725 mtx_unlock(&vm_daemon_mtx); 1726 } 1727 1728 static void 1729 vm_daemon(void) 1730 { 1731 struct rlimit rsslim; 1732 struct proc *p; 1733 struct thread *td; 1734 struct vmspace *vm; 1735 int breakout, swapout_flags, tryagain, attempts; 1736 #ifdef RACCT 1737 uint64_t rsize, ravailable; 1738 #endif 1739 1740 while (TRUE) { 1741 mtx_lock(&vm_daemon_mtx); 1742 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 1743 #ifdef RACCT 1744 racct_enable ? hz : 0 1745 #else 1746 0 1747 #endif 1748 ); 1749 swapout_flags = vm_pageout_req_swapout; 1750 vm_pageout_req_swapout = 0; 1751 mtx_unlock(&vm_daemon_mtx); 1752 if (swapout_flags) 1753 swapout_procs(swapout_flags); 1754 1755 /* 1756 * scan the processes for exceeding their rlimits or if 1757 * process is swapped out -- deactivate pages 1758 */ 1759 tryagain = 0; 1760 attempts = 0; 1761 again: 1762 attempts++; 1763 sx_slock(&allproc_lock); 1764 FOREACH_PROC_IN_SYSTEM(p) { 1765 vm_pindex_t limit, size; 1766 1767 /* 1768 * if this is a system process or if we have already 1769 * looked at this process, skip it. 1770 */ 1771 PROC_LOCK(p); 1772 if (p->p_state != PRS_NORMAL || 1773 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 1774 PROC_UNLOCK(p); 1775 continue; 1776 } 1777 /* 1778 * if the process is in a non-running type state, 1779 * don't touch it. 1780 */ 1781 breakout = 0; 1782 FOREACH_THREAD_IN_PROC(p, td) { 1783 thread_lock(td); 1784 if (!TD_ON_RUNQ(td) && 1785 !TD_IS_RUNNING(td) && 1786 !TD_IS_SLEEPING(td) && 1787 !TD_IS_SUSPENDED(td)) { 1788 thread_unlock(td); 1789 breakout = 1; 1790 break; 1791 } 1792 thread_unlock(td); 1793 } 1794 if (breakout) { 1795 PROC_UNLOCK(p); 1796 continue; 1797 } 1798 /* 1799 * get a limit 1800 */ 1801 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 1802 limit = OFF_TO_IDX( 1803 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 1804 1805 /* 1806 * let processes that are swapped out really be 1807 * swapped out set the limit to nothing (will force a 1808 * swap-out.) 1809 */ 1810 if ((p->p_flag & P_INMEM) == 0) 1811 limit = 0; /* XXX */ 1812 vm = vmspace_acquire_ref(p); 1813 _PHOLD_LITE(p); 1814 PROC_UNLOCK(p); 1815 if (vm == NULL) { 1816 PRELE(p); 1817 continue; 1818 } 1819 sx_sunlock(&allproc_lock); 1820 1821 size = vmspace_resident_count(vm); 1822 if (size >= limit) { 1823 vm_pageout_map_deactivate_pages( 1824 &vm->vm_map, limit); 1825 } 1826 #ifdef RACCT 1827 if (racct_enable) { 1828 rsize = IDX_TO_OFF(size); 1829 PROC_LOCK(p); 1830 racct_set(p, RACCT_RSS, rsize); 1831 ravailable = racct_get_available(p, RACCT_RSS); 1832 PROC_UNLOCK(p); 1833 if (rsize > ravailable) { 1834 /* 1835 * Don't be overly aggressive; this 1836 * might be an innocent process, 1837 * and the limit could've been exceeded 1838 * by some memory hog. Don't try 1839 * to deactivate more than 1/4th 1840 * of process' resident set size. 1841 */ 1842 if (attempts <= 8) { 1843 if (ravailable < rsize - 1844 (rsize / 4)) { 1845 ravailable = rsize - 1846 (rsize / 4); 1847 } 1848 } 1849 vm_pageout_map_deactivate_pages( 1850 &vm->vm_map, 1851 OFF_TO_IDX(ravailable)); 1852 /* Update RSS usage after paging out. */ 1853 size = vmspace_resident_count(vm); 1854 rsize = IDX_TO_OFF(size); 1855 PROC_LOCK(p); 1856 racct_set(p, RACCT_RSS, rsize); 1857 PROC_UNLOCK(p); 1858 if (rsize > ravailable) 1859 tryagain = 1; 1860 } 1861 } 1862 #endif 1863 vmspace_free(vm); 1864 sx_slock(&allproc_lock); 1865 PRELE(p); 1866 } 1867 sx_sunlock(&allproc_lock); 1868 if (tryagain != 0 && attempts <= 10) 1869 goto again; 1870 } 1871 } 1872 #endif /* !defined(NO_SWAPPING) */
Cache object: 399114ffe9597c1fc4855a64c286b544
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