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 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_cache); 143 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan); 144 145 #if !defined(NO_SWAPPING) 146 /* the kernel process "vm_daemon"*/ 147 static void vm_daemon(void); 148 static struct proc *vmproc; 149 150 static struct kproc_desc vm_kp = { 151 "vmdaemon", 152 vm_daemon, 153 &vmproc 154 }; 155 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); 156 #endif 157 158 159 int vm_pageout_deficit; /* Estimated number of pages deficit */ 160 int vm_pageout_wakeup_thresh; 161 static int vm_pageout_oom_seq = 12; 162 bool vm_pageout_wanted; /* Event on which pageout daemon sleeps */ 163 bool vm_pages_needed; /* Are threads waiting for free pages? */ 164 165 #if !defined(NO_SWAPPING) 166 static int vm_pageout_req_swapout; /* XXX */ 167 static int vm_daemon_needed; 168 static struct mtx vm_daemon_mtx; 169 /* Allow for use by vm_pageout before vm_daemon is initialized. */ 170 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); 171 #endif 172 static int vm_max_launder = 32; 173 static int vm_pageout_update_period; 174 static int defer_swap_pageouts; 175 static int disable_swap_pageouts; 176 static int lowmem_period = 10; 177 static time_t lowmem_uptime; 178 179 #if defined(NO_SWAPPING) 180 static int vm_swap_enabled = 0; 181 static int vm_swap_idle_enabled = 0; 182 #else 183 static int vm_swap_enabled = 1; 184 static int vm_swap_idle_enabled = 0; 185 #endif 186 187 static int vm_panic_on_oom = 0; 188 189 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom, 190 CTLFLAG_RWTUN, &vm_panic_on_oom, 0, 191 "panic on out of memory instead of killing the largest process"); 192 193 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh, 194 CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0, 195 "free page threshold for waking up the pageout daemon"); 196 197 SYSCTL_INT(_vm, OID_AUTO, max_launder, 198 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout"); 199 200 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period, 201 CTLFLAG_RW, &vm_pageout_update_period, 0, 202 "Maximum active LRU update period"); 203 204 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0, 205 "Low memory callback period"); 206 207 #if defined(NO_SWAPPING) 208 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 209 CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout"); 210 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 211 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 212 #else 213 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 214 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 215 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 216 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 217 #endif 218 219 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts, 220 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem"); 221 222 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 223 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 224 225 static int pageout_lock_miss; 226 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 227 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 228 229 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq, 230 CTLFLAG_RW, &vm_pageout_oom_seq, 0, 231 "back-to-back calls to oom detector to start OOM"); 232 233 #define VM_PAGEOUT_PAGE_COUNT 16 234 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 235 236 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 237 SYSCTL_INT(_vm, OID_AUTO, max_wired, 238 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count"); 239 240 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *); 241 #if !defined(NO_SWAPPING) 242 static void vm_pageout_map_deactivate_pages(vm_map_t, long); 243 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long); 244 static void vm_req_vmdaemon(int req); 245 #endif 246 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *); 247 248 /* 249 * Initialize a dummy page for marking the caller's place in the specified 250 * paging queue. In principle, this function only needs to set the flag 251 * PG_MARKER. Nonetheless, it wirte busies and initializes the hold count 252 * to one as safety precautions. 253 */ 254 static void 255 vm_pageout_init_marker(vm_page_t marker, u_short queue) 256 { 257 258 bzero(marker, sizeof(*marker)); 259 marker->flags = PG_MARKER; 260 marker->busy_lock = VPB_SINGLE_EXCLUSIVER; 261 marker->queue = queue; 262 marker->hold_count = 1; 263 } 264 265 /* 266 * vm_pageout_fallback_object_lock: 267 * 268 * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is 269 * known to have failed and page queue must be either PQ_ACTIVE or 270 * PQ_INACTIVE. To avoid lock order violation, unlock the page queues 271 * while locking the vm object. Use marker page to detect page queue 272 * changes and maintain notion of next page on page queue. Return 273 * TRUE if no changes were detected, FALSE otherwise. vm object is 274 * locked on return. 275 * 276 * This function depends on both the lock portion of struct vm_object 277 * and normal struct vm_page being type stable. 278 */ 279 static boolean_t 280 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next) 281 { 282 struct vm_page marker; 283 struct vm_pagequeue *pq; 284 boolean_t unchanged; 285 u_short queue; 286 vm_object_t object; 287 288 queue = m->queue; 289 vm_pageout_init_marker(&marker, queue); 290 pq = vm_page_pagequeue(m); 291 object = m->object; 292 293 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 294 vm_pagequeue_unlock(pq); 295 vm_page_unlock(m); 296 VM_OBJECT_WLOCK(object); 297 vm_page_lock(m); 298 vm_pagequeue_lock(pq); 299 300 /* 301 * The page's object might have changed, and/or the page might 302 * have moved from its original position in the queue. If the 303 * page's object has changed, then the caller should abandon 304 * processing the page because the wrong object lock was 305 * acquired. Use the marker's plinks.q, not the page's, to 306 * determine if the page has been moved. The state of the 307 * page's plinks.q can be indeterminate; whereas, the marker's 308 * plinks.q must be valid. 309 */ 310 *next = TAILQ_NEXT(&marker, plinks.q); 311 unchanged = m->object == object && 312 m == TAILQ_PREV(&marker, pglist, plinks.q); 313 KASSERT(!unchanged || m->queue == queue, 314 ("page %p queue %d %d", m, queue, m->queue)); 315 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 316 return (unchanged); 317 } 318 319 /* 320 * Lock the page while holding the page queue lock. Use marker page 321 * to detect page queue changes and maintain notion of next page on 322 * page queue. Return TRUE if no changes were detected, FALSE 323 * otherwise. The page is locked on return. The page queue lock might 324 * be dropped and reacquired. 325 * 326 * This function depends on normal struct vm_page being type stable. 327 */ 328 static boolean_t 329 vm_pageout_page_lock(vm_page_t m, vm_page_t *next) 330 { 331 struct vm_page marker; 332 struct vm_pagequeue *pq; 333 boolean_t unchanged; 334 u_short queue; 335 336 vm_page_lock_assert(m, MA_NOTOWNED); 337 if (vm_page_trylock(m)) 338 return (TRUE); 339 340 queue = m->queue; 341 vm_pageout_init_marker(&marker, queue); 342 pq = vm_page_pagequeue(m); 343 344 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 345 vm_pagequeue_unlock(pq); 346 vm_page_lock(m); 347 vm_pagequeue_lock(pq); 348 349 /* Page queue might have changed. */ 350 *next = TAILQ_NEXT(&marker, plinks.q); 351 unchanged = m == TAILQ_PREV(&marker, pglist, plinks.q); 352 KASSERT(!unchanged || m->queue == queue, 353 ("page %p queue %d %d", m, queue, m->queue)); 354 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 355 return (unchanged); 356 } 357 358 /* 359 * vm_pageout_clean: 360 * 361 * Clean the page and remove it from the laundry. 362 * 363 * We set the busy bit to cause potential page faults on this page to 364 * block. Note the careful timing, however, the busy bit isn't set till 365 * late and we cannot do anything that will mess with the page. 366 */ 367 static int 368 vm_pageout_cluster(vm_page_t m) 369 { 370 vm_object_t object; 371 vm_page_t mc[2*vm_pageout_page_count], pb, ps; 372 int pageout_count; 373 int ib, is, page_base; 374 vm_pindex_t pindex = m->pindex; 375 376 vm_page_lock_assert(m, MA_OWNED); 377 object = m->object; 378 VM_OBJECT_ASSERT_WLOCKED(object); 379 380 /* 381 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP 382 * with the new swapper, but we could have serious problems paging 383 * out other object types if there is insufficient memory. 384 * 385 * Unfortunately, checking free memory here is far too late, so the 386 * check has been moved up a procedural level. 387 */ 388 389 /* 390 * Can't clean the page if it's busy or held. 391 */ 392 vm_page_assert_unbusied(m); 393 KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m)); 394 vm_page_unlock(m); 395 396 mc[vm_pageout_page_count] = pb = ps = m; 397 pageout_count = 1; 398 page_base = vm_pageout_page_count; 399 ib = 1; 400 is = 1; 401 402 /* 403 * Scan object for clusterable pages. 404 * 405 * We can cluster ONLY if: ->> the page is NOT 406 * clean, wired, busy, held, or mapped into a 407 * buffer, and one of the following: 408 * 1) The page is inactive, or a seldom used 409 * active page. 410 * -or- 411 * 2) we force the issue. 412 * 413 * During heavy mmap/modification loads the pageout 414 * daemon can really fragment the underlying file 415 * due to flushing pages out of order and not trying 416 * align the clusters (which leave sporatic out-of-order 417 * holes). To solve this problem we do the reverse scan 418 * first and attempt to align our cluster, then do a 419 * forward scan if room remains. 420 */ 421 more: 422 while (ib && pageout_count < vm_pageout_page_count) { 423 vm_page_t p; 424 425 if (ib > pindex) { 426 ib = 0; 427 break; 428 } 429 430 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) { 431 ib = 0; 432 break; 433 } 434 vm_page_test_dirty(p); 435 if (p->dirty == 0) { 436 ib = 0; 437 break; 438 } 439 vm_page_lock(p); 440 if (p->queue != PQ_INACTIVE || 441 p->hold_count != 0) { /* may be undergoing I/O */ 442 vm_page_unlock(p); 443 ib = 0; 444 break; 445 } 446 vm_page_unlock(p); 447 mc[--page_base] = pb = p; 448 ++pageout_count; 449 ++ib; 450 /* 451 * alignment boundary, stop here and switch directions. Do 452 * not clear ib. 453 */ 454 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 455 break; 456 } 457 458 while (pageout_count < vm_pageout_page_count && 459 pindex + is < object->size) { 460 vm_page_t p; 461 462 if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p)) 463 break; 464 vm_page_test_dirty(p); 465 if (p->dirty == 0) 466 break; 467 vm_page_lock(p); 468 if (p->queue != PQ_INACTIVE || 469 p->hold_count != 0) { /* may be undergoing I/O */ 470 vm_page_unlock(p); 471 break; 472 } 473 vm_page_unlock(p); 474 mc[page_base + pageout_count] = ps = p; 475 ++pageout_count; 476 ++is; 477 } 478 479 /* 480 * If we exhausted our forward scan, continue with the reverse scan 481 * when possible, even past a page boundary. This catches boundary 482 * conditions. 483 */ 484 if (ib && pageout_count < vm_pageout_page_count) 485 goto more; 486 487 /* 488 * we allow reads during pageouts... 489 */ 490 return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL, 491 NULL)); 492 } 493 494 /* 495 * vm_pageout_flush() - launder the given pages 496 * 497 * The given pages are laundered. Note that we setup for the start of 498 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 499 * reference count all in here rather then in the parent. If we want 500 * the parent to do more sophisticated things we may have to change 501 * the ordering. 502 * 503 * Returned runlen is the count of pages between mreq and first 504 * page after mreq with status VM_PAGER_AGAIN. 505 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL 506 * for any page in runlen set. 507 */ 508 int 509 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen, 510 boolean_t *eio) 511 { 512 vm_object_t object = mc[0]->object; 513 int pageout_status[count]; 514 int numpagedout = 0; 515 int i, runlen; 516 517 VM_OBJECT_ASSERT_WLOCKED(object); 518 519 /* 520 * Initiate I/O. Bump the vm_page_t->busy counter and 521 * mark the pages read-only. 522 * 523 * We do not have to fixup the clean/dirty bits here... we can 524 * allow the pager to do it after the I/O completes. 525 * 526 * NOTE! mc[i]->dirty may be partial or fragmented due to an 527 * edge case with file fragments. 528 */ 529 for (i = 0; i < count; i++) { 530 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, 531 ("vm_pageout_flush: partially invalid page %p index %d/%d", 532 mc[i], i, count)); 533 vm_page_sbusy(mc[i]); 534 pmap_remove_write(mc[i]); 535 } 536 vm_object_pip_add(object, count); 537 538 vm_pager_put_pages(object, mc, count, flags, pageout_status); 539 540 runlen = count - mreq; 541 if (eio != NULL) 542 *eio = FALSE; 543 for (i = 0; i < count; i++) { 544 vm_page_t mt = mc[i]; 545 546 KASSERT(pageout_status[i] == VM_PAGER_PEND || 547 !pmap_page_is_write_mapped(mt), 548 ("vm_pageout_flush: page %p is not write protected", mt)); 549 switch (pageout_status[i]) { 550 case VM_PAGER_OK: 551 case VM_PAGER_PEND: 552 numpagedout++; 553 break; 554 case VM_PAGER_BAD: 555 /* 556 * Page outside of range of object. Right now we 557 * essentially lose the changes by pretending it 558 * worked. 559 */ 560 vm_page_undirty(mt); 561 break; 562 case VM_PAGER_ERROR: 563 case VM_PAGER_FAIL: 564 /* 565 * If page couldn't be paged out, then reactivate the 566 * page so it doesn't clog the inactive list. (We 567 * will try paging out it again later). 568 */ 569 vm_page_lock(mt); 570 vm_page_activate(mt); 571 vm_page_unlock(mt); 572 if (eio != NULL && i >= mreq && i - mreq < runlen) 573 *eio = TRUE; 574 break; 575 case VM_PAGER_AGAIN: 576 if (i >= mreq && i - mreq < runlen) 577 runlen = i - mreq; 578 break; 579 } 580 581 /* 582 * If the operation is still going, leave the page busy to 583 * block all other accesses. Also, leave the paging in 584 * progress indicator set so that we don't attempt an object 585 * collapse. 586 */ 587 if (pageout_status[i] != VM_PAGER_PEND) { 588 vm_object_pip_wakeup(object); 589 vm_page_sunbusy(mt); 590 } 591 } 592 if (prunlen != NULL) 593 *prunlen = runlen; 594 return (numpagedout); 595 } 596 597 #if !defined(NO_SWAPPING) 598 /* 599 * vm_pageout_object_deactivate_pages 600 * 601 * Deactivate enough pages to satisfy the inactive target 602 * requirements. 603 * 604 * The object and map must be locked. 605 */ 606 static void 607 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 608 long desired) 609 { 610 vm_object_t backing_object, object; 611 vm_page_t p; 612 int act_delta, remove_mode; 613 614 VM_OBJECT_ASSERT_LOCKED(first_object); 615 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 616 return; 617 for (object = first_object;; object = backing_object) { 618 if (pmap_resident_count(pmap) <= desired) 619 goto unlock_return; 620 VM_OBJECT_ASSERT_LOCKED(object); 621 if ((object->flags & OBJ_UNMANAGED) != 0 || 622 object->paging_in_progress != 0) 623 goto unlock_return; 624 625 remove_mode = 0; 626 if (object->shadow_count > 1) 627 remove_mode = 1; 628 /* 629 * Scan the object's entire memory queue. 630 */ 631 TAILQ_FOREACH(p, &object->memq, listq) { 632 if (pmap_resident_count(pmap) <= desired) 633 goto unlock_return; 634 if (vm_page_busied(p)) 635 continue; 636 PCPU_INC(cnt.v_pdpages); 637 vm_page_lock(p); 638 if (p->wire_count != 0 || p->hold_count != 0 || 639 !pmap_page_exists_quick(pmap, p)) { 640 vm_page_unlock(p); 641 continue; 642 } 643 act_delta = pmap_ts_referenced(p); 644 if ((p->aflags & PGA_REFERENCED) != 0) { 645 if (act_delta == 0) 646 act_delta = 1; 647 vm_page_aflag_clear(p, PGA_REFERENCED); 648 } 649 if (p->queue != PQ_ACTIVE && act_delta != 0) { 650 vm_page_activate(p); 651 p->act_count += act_delta; 652 } else if (p->queue == PQ_ACTIVE) { 653 if (act_delta == 0) { 654 p->act_count -= min(p->act_count, 655 ACT_DECLINE); 656 if (!remove_mode && p->act_count == 0) { 657 pmap_remove_all(p); 658 vm_page_deactivate(p); 659 } else 660 vm_page_requeue(p); 661 } else { 662 vm_page_activate(p); 663 if (p->act_count < ACT_MAX - 664 ACT_ADVANCE) 665 p->act_count += ACT_ADVANCE; 666 vm_page_requeue(p); 667 } 668 } else if (p->queue == PQ_INACTIVE) 669 pmap_remove_all(p); 670 vm_page_unlock(p); 671 } 672 if ((backing_object = object->backing_object) == NULL) 673 goto unlock_return; 674 VM_OBJECT_RLOCK(backing_object); 675 if (object != first_object) 676 VM_OBJECT_RUNLOCK(object); 677 } 678 unlock_return: 679 if (object != first_object) 680 VM_OBJECT_RUNLOCK(object); 681 } 682 683 /* 684 * deactivate some number of pages in a map, try to do it fairly, but 685 * that is really hard to do. 686 */ 687 static void 688 vm_pageout_map_deactivate_pages(map, desired) 689 vm_map_t map; 690 long desired; 691 { 692 vm_map_entry_t tmpe; 693 vm_object_t obj, bigobj; 694 int nothingwired; 695 696 if (!vm_map_trylock(map)) 697 return; 698 699 bigobj = NULL; 700 nothingwired = TRUE; 701 702 /* 703 * first, search out the biggest object, and try to free pages from 704 * that. 705 */ 706 tmpe = map->header.next; 707 while (tmpe != &map->header) { 708 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 709 obj = tmpe->object.vm_object; 710 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 711 if (obj->shadow_count <= 1 && 712 (bigobj == NULL || 713 bigobj->resident_page_count < obj->resident_page_count)) { 714 if (bigobj != NULL) 715 VM_OBJECT_RUNLOCK(bigobj); 716 bigobj = obj; 717 } else 718 VM_OBJECT_RUNLOCK(obj); 719 } 720 } 721 if (tmpe->wired_count > 0) 722 nothingwired = FALSE; 723 tmpe = tmpe->next; 724 } 725 726 if (bigobj != NULL) { 727 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired); 728 VM_OBJECT_RUNLOCK(bigobj); 729 } 730 /* 731 * Next, hunt around for other pages to deactivate. We actually 732 * do this search sort of wrong -- .text first is not the best idea. 733 */ 734 tmpe = map->header.next; 735 while (tmpe != &map->header) { 736 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 737 break; 738 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 739 obj = tmpe->object.vm_object; 740 if (obj != NULL) { 741 VM_OBJECT_RLOCK(obj); 742 vm_pageout_object_deactivate_pages(map->pmap, obj, desired); 743 VM_OBJECT_RUNLOCK(obj); 744 } 745 } 746 tmpe = tmpe->next; 747 } 748 749 /* 750 * Remove all mappings if a process is swapped out, this will free page 751 * table pages. 752 */ 753 if (desired == 0 && nothingwired) { 754 pmap_remove(vm_map_pmap(map), vm_map_min(map), 755 vm_map_max(map)); 756 } 757 758 vm_map_unlock(map); 759 } 760 #endif /* !defined(NO_SWAPPING) */ 761 762 /* 763 * Attempt to acquire all of the necessary locks to launder a page and 764 * then call through the clustering layer to PUTPAGES. Wait a short 765 * time for a vnode lock. 766 * 767 * Requires the page and object lock on entry, releases both before return. 768 * Returns 0 on success and an errno otherwise. 769 */ 770 static int 771 vm_pageout_clean(vm_page_t m) 772 { 773 struct vnode *vp; 774 struct mount *mp; 775 vm_object_t object; 776 vm_pindex_t pindex; 777 int error, lockmode; 778 779 vm_page_assert_locked(m); 780 object = m->object; 781 VM_OBJECT_ASSERT_WLOCKED(object); 782 error = 0; 783 vp = NULL; 784 mp = NULL; 785 786 /* 787 * The object is already known NOT to be dead. It 788 * is possible for the vget() to block the whole 789 * pageout daemon, but the new low-memory handling 790 * code should prevent it. 791 * 792 * We can't wait forever for the vnode lock, we might 793 * deadlock due to a vn_read() getting stuck in 794 * vm_wait while holding this vnode. We skip the 795 * vnode if we can't get it in a reasonable amount 796 * of time. 797 */ 798 if (object->type == OBJT_VNODE) { 799 vm_page_unlock(m); 800 vp = object->handle; 801 if (vp->v_type == VREG && 802 vn_start_write(vp, &mp, V_NOWAIT) != 0) { 803 mp = NULL; 804 error = EDEADLK; 805 goto unlock_all; 806 } 807 KASSERT(mp != NULL, 808 ("vp %p with NULL v_mount", vp)); 809 vm_object_reference_locked(object); 810 pindex = m->pindex; 811 VM_OBJECT_WUNLOCK(object); 812 lockmode = MNT_SHARED_WRITES(vp->v_mount) ? 813 LK_SHARED : LK_EXCLUSIVE; 814 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) { 815 vp = NULL; 816 error = EDEADLK; 817 goto unlock_mp; 818 } 819 VM_OBJECT_WLOCK(object); 820 vm_page_lock(m); 821 /* 822 * While the object and page were unlocked, the page 823 * may have been: 824 * (1) moved to a different queue, 825 * (2) reallocated to a different object, 826 * (3) reallocated to a different offset, or 827 * (4) cleaned. 828 */ 829 if (m->queue != PQ_INACTIVE || m->object != object || 830 m->pindex != pindex || m->dirty == 0) { 831 vm_page_unlock(m); 832 error = ENXIO; 833 goto unlock_all; 834 } 835 836 /* 837 * The page may have been busied or held while the object 838 * and page locks were released. 839 */ 840 if (vm_page_busied(m) || m->hold_count != 0) { 841 vm_page_unlock(m); 842 error = EBUSY; 843 goto unlock_all; 844 } 845 } 846 847 /* 848 * If a page is dirty, then it is either being washed 849 * (but not yet cleaned) or it is still in the 850 * laundry. If it is still in the laundry, then we 851 * start the cleaning operation. 852 */ 853 if (vm_pageout_cluster(m) == 0) 854 error = EIO; 855 856 unlock_all: 857 VM_OBJECT_WUNLOCK(object); 858 859 unlock_mp: 860 vm_page_lock_assert(m, MA_NOTOWNED); 861 if (mp != NULL) { 862 if (vp != NULL) 863 vput(vp); 864 vm_object_deallocate(object); 865 vn_finished_write(mp); 866 } 867 868 return (error); 869 } 870 871 /* 872 * vm_pageout_scan does the dirty work for the pageout daemon. 873 * 874 * pass 0 - Update active LRU/deactivate pages 875 * pass 1 - Move inactive to cache or free 876 * pass 2 - Launder dirty pages 877 */ 878 static void 879 vm_pageout_scan(struct vm_domain *vmd, int pass) 880 { 881 vm_page_t m, next; 882 struct vm_pagequeue *pq; 883 vm_object_t object; 884 long min_scan; 885 int act_delta, addl_page_shortage, deficit, error, maxlaunder, maxscan; 886 int page_shortage, scan_tick, scanned, starting_page_shortage; 887 int vnodes_skipped; 888 boolean_t pageout_ok, queues_locked; 889 890 /* 891 * If we need to reclaim memory ask kernel caches to return 892 * some. We rate limit to avoid thrashing. 893 */ 894 if (vmd == &vm_dom[0] && pass > 0 && 895 (time_uptime - lowmem_uptime) >= lowmem_period) { 896 /* 897 * Decrease registered cache sizes. 898 */ 899 SDT_PROBE0(vm, , , vm__lowmem_scan); 900 EVENTHANDLER_INVOKE(vm_lowmem, 0); 901 /* 902 * We do this explicitly after the caches have been 903 * drained above. 904 */ 905 uma_reclaim(); 906 lowmem_uptime = time_uptime; 907 } 908 909 /* 910 * The addl_page_shortage is the number of temporarily 911 * stuck pages in the inactive queue. In other words, the 912 * number of pages from the inactive count that should be 913 * discounted in setting the target for the active queue scan. 914 */ 915 addl_page_shortage = 0; 916 917 /* 918 * Calculate the number of pages we want to either free or move 919 * to the cache. 920 */ 921 if (pass > 0) { 922 deficit = atomic_readandclear_int(&vm_pageout_deficit); 923 page_shortage = vm_paging_target() + deficit; 924 } else 925 page_shortage = deficit = 0; 926 starting_page_shortage = page_shortage; 927 928 /* 929 * maxlaunder limits the number of dirty pages we flush per scan. 930 * For most systems a smaller value (16 or 32) is more robust under 931 * extreme memory and disk pressure because any unnecessary writes 932 * to disk can result in extreme performance degredation. However, 933 * systems with excessive dirty pages (especially when MAP_NOSYNC is 934 * used) will die horribly with limited laundering. If the pageout 935 * daemon cannot clean enough pages in the first pass, we let it go 936 * all out in succeeding passes. 937 */ 938 if ((maxlaunder = vm_max_launder) <= 1) 939 maxlaunder = 1; 940 if (pass > 1) 941 maxlaunder = 10000; 942 943 vnodes_skipped = 0; 944 945 /* 946 * Start scanning the inactive queue for pages we can move to the 947 * cache or free. The scan will stop when the target is reached or 948 * we have scanned the entire inactive queue. Note that m->act_count 949 * is not used to form decisions for the inactive queue, only for the 950 * active queue. 951 */ 952 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 953 maxscan = pq->pq_cnt; 954 vm_pagequeue_lock(pq); 955 queues_locked = TRUE; 956 for (m = TAILQ_FIRST(&pq->pq_pl); 957 m != NULL && maxscan-- > 0 && page_shortage > 0; 958 m = next) { 959 vm_pagequeue_assert_locked(pq); 960 KASSERT(queues_locked, ("unlocked queues")); 961 KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m)); 962 963 PCPU_INC(cnt.v_pdpages); 964 next = TAILQ_NEXT(m, plinks.q); 965 966 /* 967 * skip marker pages 968 */ 969 if (m->flags & PG_MARKER) 970 continue; 971 972 KASSERT((m->flags & PG_FICTITIOUS) == 0, 973 ("Fictitious page %p cannot be in inactive queue", m)); 974 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 975 ("Unmanaged page %p cannot be in inactive queue", m)); 976 977 /* 978 * The page or object lock acquisitions fail if the 979 * page was removed from the queue or moved to a 980 * different position within the queue. In either 981 * case, addl_page_shortage should not be incremented. 982 */ 983 if (!vm_pageout_page_lock(m, &next)) 984 goto unlock_page; 985 else if (m->hold_count != 0) { 986 /* 987 * Held pages are essentially stuck in the 988 * queue. So, they ought to be discounted 989 * from the inactive count. See the 990 * calculation of the page_shortage for the 991 * loop over the active queue below. 992 */ 993 addl_page_shortage++; 994 goto unlock_page; 995 } 996 object = m->object; 997 if (!VM_OBJECT_TRYWLOCK(object)) { 998 if (!vm_pageout_fallback_object_lock(m, &next)) 999 goto unlock_object; 1000 else if (m->hold_count != 0) { 1001 addl_page_shortage++; 1002 goto unlock_object; 1003 } 1004 } 1005 if (vm_page_busied(m)) { 1006 /* 1007 * Don't mess with busy pages. Leave them at 1008 * the front of the queue. Most likely, they 1009 * are being paged out and will leave the 1010 * queue shortly after the scan finishes. So, 1011 * they ought to be discounted from the 1012 * inactive count. 1013 */ 1014 addl_page_shortage++; 1015 unlock_object: 1016 VM_OBJECT_WUNLOCK(object); 1017 unlock_page: 1018 vm_page_unlock(m); 1019 continue; 1020 } 1021 KASSERT(m->hold_count == 0, ("Held page %p", m)); 1022 1023 /* 1024 * We unlock the inactive page queue, invalidating the 1025 * 'next' pointer. Use our marker to remember our 1026 * place. 1027 */ 1028 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q); 1029 vm_pagequeue_unlock(pq); 1030 queues_locked = FALSE; 1031 1032 /* 1033 * Invalid pages can be easily freed. They cannot be 1034 * mapped, vm_page_free() asserts this. 1035 */ 1036 if (m->valid == 0) 1037 goto free_page; 1038 1039 /* 1040 * If the page has been referenced and the object is not dead, 1041 * reactivate or requeue the page depending on whether the 1042 * object is mapped. 1043 */ 1044 if ((m->aflags & PGA_REFERENCED) != 0) { 1045 vm_page_aflag_clear(m, PGA_REFERENCED); 1046 act_delta = 1; 1047 } else 1048 act_delta = 0; 1049 if (object->ref_count != 0) { 1050 act_delta += pmap_ts_referenced(m); 1051 } else { 1052 KASSERT(!pmap_page_is_mapped(m), 1053 ("vm_pageout_scan: page %p is mapped", m)); 1054 } 1055 if (act_delta != 0) { 1056 if (object->ref_count != 0) { 1057 vm_page_activate(m); 1058 1059 /* 1060 * Increase the activation count if the page 1061 * was referenced while in the inactive queue. 1062 * This makes it less likely that the page will 1063 * be returned prematurely to the inactive 1064 * queue. 1065 */ 1066 m->act_count += act_delta + ACT_ADVANCE; 1067 goto drop_page; 1068 } else if ((object->flags & OBJ_DEAD) == 0) 1069 goto requeue_page; 1070 } 1071 1072 /* 1073 * If the page appears to be clean at the machine-independent 1074 * layer, then remove all of its mappings from the pmap in 1075 * anticipation of placing it onto the cache queue. If, 1076 * however, any of the page's mappings allow write access, 1077 * then the page may still be modified until the last of those 1078 * mappings are removed. 1079 */ 1080 if (object->ref_count != 0) { 1081 vm_page_test_dirty(m); 1082 if (m->dirty == 0) 1083 pmap_remove_all(m); 1084 } 1085 1086 if (m->dirty == 0) { 1087 /* 1088 * Clean pages can be freed. 1089 */ 1090 free_page: 1091 vm_page_free(m); 1092 PCPU_INC(cnt.v_dfree); 1093 --page_shortage; 1094 } else if ((object->flags & OBJ_DEAD) != 0) { 1095 /* 1096 * Leave dirty pages from dead objects at the front of 1097 * the queue. They are being paged out and freed by 1098 * the thread that destroyed the object. They will 1099 * leave the queue shortly after the scan finishes, so 1100 * they should be discounted from the inactive count. 1101 */ 1102 addl_page_shortage++; 1103 } else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) { 1104 /* 1105 * Dirty pages need to be paged out, but flushing 1106 * a page is extremely expensive versus freeing 1107 * a clean page. Rather then artificially limiting 1108 * the number of pages we can flush, we instead give 1109 * dirty pages extra priority on the inactive queue 1110 * by forcing them to be cycled through the queue 1111 * twice before being flushed, after which the 1112 * (now clean) page will cycle through once more 1113 * before being freed. This significantly extends 1114 * the thrash point for a heavily loaded machine. 1115 */ 1116 m->flags |= PG_WINATCFLS; 1117 requeue_page: 1118 vm_pagequeue_lock(pq); 1119 queues_locked = TRUE; 1120 vm_page_requeue_locked(m); 1121 } else if (maxlaunder > 0) { 1122 /* 1123 * We always want to try to flush some dirty pages if 1124 * we encounter them, to keep the system stable. 1125 * Normally this number is small, but under extreme 1126 * pressure where there are insufficient clean pages 1127 * on the inactive queue, we may have to go all out. 1128 */ 1129 1130 if (object->type != OBJT_SWAP && 1131 object->type != OBJT_DEFAULT) 1132 pageout_ok = TRUE; 1133 else if (disable_swap_pageouts) 1134 pageout_ok = FALSE; 1135 else if (defer_swap_pageouts) 1136 pageout_ok = vm_page_count_min(); 1137 else 1138 pageout_ok = TRUE; 1139 if (!pageout_ok) 1140 goto requeue_page; 1141 error = vm_pageout_clean(m); 1142 /* 1143 * Decrement page_shortage on success to account for 1144 * the (future) cleaned page. Otherwise we could wind 1145 * up laundering or cleaning too many pages. 1146 */ 1147 if (error == 0) { 1148 page_shortage--; 1149 maxlaunder--; 1150 } else if (error == EDEADLK) { 1151 pageout_lock_miss++; 1152 vnodes_skipped++; 1153 } else if (error == EBUSY) { 1154 addl_page_shortage++; 1155 } 1156 vm_page_lock_assert(m, MA_NOTOWNED); 1157 goto relock_queues; 1158 } 1159 drop_page: 1160 vm_page_unlock(m); 1161 VM_OBJECT_WUNLOCK(object); 1162 relock_queues: 1163 if (!queues_locked) { 1164 vm_pagequeue_lock(pq); 1165 queues_locked = TRUE; 1166 } 1167 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q); 1168 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q); 1169 } 1170 vm_pagequeue_unlock(pq); 1171 1172 #if !defined(NO_SWAPPING) 1173 /* 1174 * Wakeup the swapout daemon if we didn't cache or free the targeted 1175 * number of pages. 1176 */ 1177 if (vm_swap_enabled && page_shortage > 0) 1178 vm_req_vmdaemon(VM_SWAP_NORMAL); 1179 #endif 1180 1181 /* 1182 * Wakeup the sync daemon if we skipped a vnode in a writeable object 1183 * and we didn't cache or free enough pages. 1184 */ 1185 if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target - 1186 vm_cnt.v_free_min) 1187 (void)speedup_syncer(); 1188 1189 /* 1190 * If the inactive queue scan fails repeatedly to meet its 1191 * target, kill the largest process. 1192 */ 1193 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1194 1195 /* 1196 * Compute the number of pages we want to try to move from the 1197 * active queue to the inactive queue. 1198 */ 1199 page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count + 1200 vm_paging_target() + deficit + addl_page_shortage; 1201 1202 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1203 vm_pagequeue_lock(pq); 1204 maxscan = pq->pq_cnt; 1205 1206 /* 1207 * If we're just idle polling attempt to visit every 1208 * active page within 'update_period' seconds. 1209 */ 1210 scan_tick = ticks; 1211 if (vm_pageout_update_period != 0) { 1212 min_scan = pq->pq_cnt; 1213 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1214 min_scan /= hz * vm_pageout_update_period; 1215 } else 1216 min_scan = 0; 1217 if (min_scan > 0 || (page_shortage > 0 && maxscan > 0)) 1218 vmd->vmd_last_active_scan = scan_tick; 1219 1220 /* 1221 * Scan the active queue for pages that can be deactivated. Update 1222 * the per-page activity counter and use it to identify deactivation 1223 * candidates. 1224 */ 1225 for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned < 1226 min_scan || (page_shortage > 0 && scanned < maxscan)); m = next, 1227 scanned++) { 1228 1229 KASSERT(m->queue == PQ_ACTIVE, 1230 ("vm_pageout_scan: page %p isn't active", m)); 1231 1232 next = TAILQ_NEXT(m, plinks.q); 1233 if ((m->flags & PG_MARKER) != 0) 1234 continue; 1235 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1236 ("Fictitious page %p cannot be in active queue", m)); 1237 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1238 ("Unmanaged page %p cannot be in active queue", m)); 1239 if (!vm_pageout_page_lock(m, &next)) { 1240 vm_page_unlock(m); 1241 continue; 1242 } 1243 1244 /* 1245 * The count for pagedaemon pages is done after checking the 1246 * page for eligibility... 1247 */ 1248 PCPU_INC(cnt.v_pdpages); 1249 1250 /* 1251 * Check to see "how much" the page has been used. 1252 */ 1253 if ((m->aflags & PGA_REFERENCED) != 0) { 1254 vm_page_aflag_clear(m, PGA_REFERENCED); 1255 act_delta = 1; 1256 } else 1257 act_delta = 0; 1258 1259 /* 1260 * Unlocked object ref count check. Two races are possible. 1261 * 1) The ref was transitioning to zero and we saw non-zero, 1262 * the pmap bits will be checked unnecessarily. 1263 * 2) The ref was transitioning to one and we saw zero. 1264 * The page lock prevents a new reference to this page so 1265 * we need not check the reference bits. 1266 */ 1267 if (m->object->ref_count != 0) 1268 act_delta += pmap_ts_referenced(m); 1269 1270 /* 1271 * Advance or decay the act_count based on recent usage. 1272 */ 1273 if (act_delta != 0) { 1274 m->act_count += ACT_ADVANCE + act_delta; 1275 if (m->act_count > ACT_MAX) 1276 m->act_count = ACT_MAX; 1277 } else 1278 m->act_count -= min(m->act_count, ACT_DECLINE); 1279 1280 /* 1281 * Move this page to the tail of the active or inactive 1282 * queue depending on usage. 1283 */ 1284 if (m->act_count == 0) { 1285 /* Dequeue to avoid later lock recursion. */ 1286 vm_page_dequeue_locked(m); 1287 vm_page_deactivate(m); 1288 page_shortage--; 1289 } else 1290 vm_page_requeue_locked(m); 1291 vm_page_unlock(m); 1292 } 1293 vm_pagequeue_unlock(pq); 1294 #if !defined(NO_SWAPPING) 1295 /* 1296 * Idle process swapout -- run once per second. 1297 */ 1298 if (vm_swap_idle_enabled) { 1299 static long lsec; 1300 if (time_second != lsec) { 1301 vm_req_vmdaemon(VM_SWAP_IDLE); 1302 lsec = time_second; 1303 } 1304 } 1305 #endif 1306 } 1307 1308 static int vm_pageout_oom_vote; 1309 1310 /* 1311 * The pagedaemon threads randlomly select one to perform the 1312 * OOM. Trying to kill processes before all pagedaemons 1313 * failed to reach free target is premature. 1314 */ 1315 static void 1316 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1317 int starting_page_shortage) 1318 { 1319 int old_vote; 1320 1321 if (starting_page_shortage <= 0 || starting_page_shortage != 1322 page_shortage) 1323 vmd->vmd_oom_seq = 0; 1324 else 1325 vmd->vmd_oom_seq++; 1326 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1327 if (vmd->vmd_oom) { 1328 vmd->vmd_oom = FALSE; 1329 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1330 } 1331 return; 1332 } 1333 1334 /* 1335 * Do not follow the call sequence until OOM condition is 1336 * cleared. 1337 */ 1338 vmd->vmd_oom_seq = 0; 1339 1340 if (vmd->vmd_oom) 1341 return; 1342 1343 vmd->vmd_oom = TRUE; 1344 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1345 if (old_vote != vm_ndomains - 1) 1346 return; 1347 1348 /* 1349 * The current pagedaemon thread is the last in the quorum to 1350 * start OOM. Initiate the selection and signaling of the 1351 * victim. 1352 */ 1353 vm_pageout_oom(VM_OOM_MEM); 1354 1355 /* 1356 * After one round of OOM terror, recall our vote. On the 1357 * next pass, current pagedaemon would vote again if the low 1358 * memory condition is still there, due to vmd_oom being 1359 * false. 1360 */ 1361 vmd->vmd_oom = FALSE; 1362 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1363 } 1364 1365 /* 1366 * The OOM killer is the page daemon's action of last resort when 1367 * memory allocation requests have been stalled for a prolonged period 1368 * of time because it cannot reclaim memory. This function computes 1369 * the approximate number of physical pages that could be reclaimed if 1370 * the specified address space is destroyed. 1371 * 1372 * Private, anonymous memory owned by the address space is the 1373 * principal resource that we expect to recover after an OOM kill. 1374 * Since the physical pages mapped by the address space's COW entries 1375 * are typically shared pages, they are unlikely to be released and so 1376 * they are not counted. 1377 * 1378 * To get to the point where the page daemon runs the OOM killer, its 1379 * efforts to write-back vnode-backed pages may have stalled. This 1380 * could be caused by a memory allocation deadlock in the write path 1381 * that might be resolved by an OOM kill. Therefore, physical pages 1382 * belonging to vnode-backed objects are counted, because they might 1383 * be freed without being written out first if the address space holds 1384 * the last reference to an unlinked vnode. 1385 * 1386 * Similarly, physical pages belonging to OBJT_PHYS objects are 1387 * counted because the address space might hold the last reference to 1388 * the object. 1389 */ 1390 static long 1391 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1392 { 1393 vm_map_t map; 1394 vm_map_entry_t entry; 1395 vm_object_t obj; 1396 long res; 1397 1398 map = &vmspace->vm_map; 1399 KASSERT(!map->system_map, ("system map")); 1400 sx_assert(&map->lock, SA_LOCKED); 1401 res = 0; 1402 for (entry = map->header.next; entry != &map->header; 1403 entry = entry->next) { 1404 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1405 continue; 1406 obj = entry->object.vm_object; 1407 if (obj == NULL) 1408 continue; 1409 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1410 obj->ref_count != 1) 1411 continue; 1412 switch (obj->type) { 1413 case OBJT_DEFAULT: 1414 case OBJT_SWAP: 1415 case OBJT_PHYS: 1416 case OBJT_VNODE: 1417 res += obj->resident_page_count; 1418 break; 1419 } 1420 } 1421 return (res); 1422 } 1423 1424 void 1425 vm_pageout_oom(int shortage) 1426 { 1427 struct proc *p, *bigproc; 1428 vm_offset_t size, bigsize; 1429 struct thread *td; 1430 struct vmspace *vm; 1431 1432 /* 1433 * We keep the process bigproc locked once we find it to keep anyone 1434 * from messing with it; however, there is a possibility of 1435 * deadlock if process B is bigproc and one of it's child processes 1436 * attempts to propagate a signal to B while we are waiting for A's 1437 * lock while walking this list. To avoid this, we don't block on 1438 * the process lock but just skip a process if it is already locked. 1439 */ 1440 bigproc = NULL; 1441 bigsize = 0; 1442 sx_slock(&allproc_lock); 1443 FOREACH_PROC_IN_SYSTEM(p) { 1444 int breakout; 1445 1446 PROC_LOCK(p); 1447 1448 /* 1449 * If this is a system, protected or killed process, skip it. 1450 */ 1451 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1452 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1453 p->p_pid == 1 || P_KILLED(p) || 1454 (p->p_pid < 48 && swap_pager_avail != 0)) { 1455 PROC_UNLOCK(p); 1456 continue; 1457 } 1458 /* 1459 * If the process is in a non-running type state, 1460 * don't touch it. Check all the threads individually. 1461 */ 1462 breakout = 0; 1463 FOREACH_THREAD_IN_PROC(p, td) { 1464 thread_lock(td); 1465 if (!TD_ON_RUNQ(td) && 1466 !TD_IS_RUNNING(td) && 1467 !TD_IS_SLEEPING(td) && 1468 !TD_IS_SUSPENDED(td) && 1469 !TD_IS_SWAPPED(td)) { 1470 thread_unlock(td); 1471 breakout = 1; 1472 break; 1473 } 1474 thread_unlock(td); 1475 } 1476 if (breakout) { 1477 PROC_UNLOCK(p); 1478 continue; 1479 } 1480 /* 1481 * get the process size 1482 */ 1483 vm = vmspace_acquire_ref(p); 1484 if (vm == NULL) { 1485 PROC_UNLOCK(p); 1486 continue; 1487 } 1488 _PHOLD_LITE(p); 1489 PROC_UNLOCK(p); 1490 sx_sunlock(&allproc_lock); 1491 if (!vm_map_trylock_read(&vm->vm_map)) { 1492 vmspace_free(vm); 1493 sx_slock(&allproc_lock); 1494 PRELE(p); 1495 continue; 1496 } 1497 size = vmspace_swap_count(vm); 1498 if (shortage == VM_OOM_MEM) 1499 size += vm_pageout_oom_pagecount(vm); 1500 vm_map_unlock_read(&vm->vm_map); 1501 vmspace_free(vm); 1502 sx_slock(&allproc_lock); 1503 1504 /* 1505 * If this process is bigger than the biggest one, 1506 * remember it. 1507 */ 1508 if (size > bigsize) { 1509 if (bigproc != NULL) 1510 PRELE(bigproc); 1511 bigproc = p; 1512 bigsize = size; 1513 } else { 1514 PRELE(p); 1515 } 1516 } 1517 sx_sunlock(&allproc_lock); 1518 if (bigproc != NULL) { 1519 if (vm_panic_on_oom != 0) 1520 panic("out of swap space"); 1521 PROC_LOCK(bigproc); 1522 killproc(bigproc, "out of swap space"); 1523 sched_nice(bigproc, PRIO_MIN); 1524 _PRELE(bigproc); 1525 PROC_UNLOCK(bigproc); 1526 wakeup(&vm_cnt.v_free_count); 1527 } 1528 } 1529 1530 static void 1531 vm_pageout_worker(void *arg) 1532 { 1533 struct vm_domain *domain; 1534 int domidx; 1535 1536 domidx = (uintptr_t)arg; 1537 domain = &vm_dom[domidx]; 1538 1539 /* 1540 * XXXKIB It could be useful to bind pageout daemon threads to 1541 * the cores belonging to the domain, from which vm_page_array 1542 * is allocated. 1543 */ 1544 1545 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1546 domain->vmd_last_active_scan = ticks; 1547 vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE); 1548 vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE); 1549 TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl, 1550 &domain->vmd_inacthead, plinks.q); 1551 1552 /* 1553 * The pageout daemon worker is never done, so loop forever. 1554 */ 1555 while (TRUE) { 1556 mtx_lock(&vm_page_queue_free_mtx); 1557 1558 /* 1559 * Generally, after a level >= 1 scan, if there are enough 1560 * free pages to wakeup the waiters, then they are already 1561 * awake. A call to vm_page_free() during the scan awakened 1562 * them. However, in the following case, this wakeup serves 1563 * to bound the amount of time that a thread might wait. 1564 * Suppose a thread's call to vm_page_alloc() fails, but 1565 * before that thread calls VM_WAIT, enough pages are freed by 1566 * other threads to alleviate the free page shortage. The 1567 * thread will, nonetheless, wait until another page is freed 1568 * or this wakeup is performed. 1569 */ 1570 if (vm_pages_needed && !vm_page_count_min()) { 1571 vm_pages_needed = false; 1572 wakeup(&vm_cnt.v_free_count); 1573 } 1574 1575 /* 1576 * Do not clear vm_pageout_wanted until we reach our target. 1577 * Otherwise, we may be awakened over and over again, wasting 1578 * CPU time. 1579 */ 1580 if (vm_pageout_wanted && !vm_paging_needed()) 1581 vm_pageout_wanted = false; 1582 1583 /* 1584 * Might the page daemon receive a wakeup call? 1585 */ 1586 if (vm_pageout_wanted) { 1587 /* 1588 * No. Either vm_pageout_wanted was set by another 1589 * thread during the previous scan, which must have 1590 * been a level 0 scan, or vm_pageout_wanted was 1591 * already set and the scan failed to free enough 1592 * pages. If we haven't yet performed a level >= 2 1593 * scan (unlimited dirty cleaning), then upgrade the 1594 * level and scan again now. Otherwise, sleep a bit 1595 * and try again later. 1596 */ 1597 mtx_unlock(&vm_page_queue_free_mtx); 1598 if (domain->vmd_pass > 1) 1599 pause("psleep", hz / 2); 1600 domain->vmd_pass++; 1601 } else { 1602 /* 1603 * Yes. Sleep until pages need to be reclaimed or 1604 * have their reference stats updated. 1605 */ 1606 if (mtx_sleep(&vm_pageout_wanted, 1607 &vm_page_queue_free_mtx, PDROP | PVM, "psleep", 1608 hz) == 0) { 1609 PCPU_INC(cnt.v_pdwakeups); 1610 domain->vmd_pass = 1; 1611 } else 1612 domain->vmd_pass = 0; 1613 } 1614 1615 vm_pageout_scan(domain, domain->vmd_pass); 1616 } 1617 } 1618 1619 /* 1620 * vm_pageout_init initialises basic pageout daemon settings. 1621 */ 1622 static void 1623 vm_pageout_init(void) 1624 { 1625 /* 1626 * Initialize some paging parameters. 1627 */ 1628 vm_cnt.v_interrupt_free_min = 2; 1629 if (vm_cnt.v_page_count < 2000) 1630 vm_pageout_page_count = 8; 1631 1632 /* 1633 * v_free_reserved needs to include enough for the largest 1634 * swap pager structures plus enough for any pv_entry structs 1635 * when paging. 1636 */ 1637 if (vm_cnt.v_page_count > 1024) 1638 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200; 1639 else 1640 vm_cnt.v_free_min = 4; 1641 vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 1642 vm_cnt.v_interrupt_free_min; 1643 vm_cnt.v_free_reserved = vm_pageout_page_count + 1644 vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768); 1645 vm_cnt.v_free_severe = vm_cnt.v_free_min / 2; 1646 vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved; 1647 vm_cnt.v_free_min += vm_cnt.v_free_reserved; 1648 vm_cnt.v_free_severe += vm_cnt.v_free_reserved; 1649 vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2; 1650 if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3) 1651 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3; 1652 1653 /* 1654 * Set the default wakeup threshold to be 10% above the minimum 1655 * page limit. This keeps the steady state out of shortfall. 1656 */ 1657 vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11; 1658 1659 /* 1660 * Set interval in seconds for active scan. We want to visit each 1661 * page at least once every ten minutes. This is to prevent worst 1662 * case paging behaviors with stale active LRU. 1663 */ 1664 if (vm_pageout_update_period == 0) 1665 vm_pageout_update_period = 600; 1666 1667 /* XXX does not really belong here */ 1668 if (vm_page_max_wired == 0) 1669 vm_page_max_wired = vm_cnt.v_free_count / 3; 1670 } 1671 1672 /* 1673 * vm_pageout is the high level pageout daemon. 1674 */ 1675 static void 1676 vm_pageout(void) 1677 { 1678 int error; 1679 #ifdef VM_NUMA_ALLOC 1680 int i; 1681 #endif 1682 1683 swap_pager_swap_init(); 1684 #ifdef VM_NUMA_ALLOC 1685 for (i = 1; i < vm_ndomains; i++) { 1686 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i, 1687 curproc, NULL, 0, 0, "dom%d", i); 1688 if (error != 0) { 1689 panic("starting pageout for domain %d, error %d\n", 1690 i, error); 1691 } 1692 } 1693 #endif 1694 error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL, 1695 0, 0, "uma"); 1696 if (error != 0) 1697 panic("starting uma_reclaim helper, error %d\n", error); 1698 vm_pageout_worker((void *)(uintptr_t)0); 1699 } 1700 1701 /* 1702 * Unless the free page queue lock is held by the caller, this function 1703 * should be regarded as advisory. Specifically, the caller should 1704 * not msleep() on &vm_cnt.v_free_count following this function unless 1705 * the free page queue lock is held until the msleep() is performed. 1706 */ 1707 void 1708 pagedaemon_wakeup(void) 1709 { 1710 1711 if (!vm_pageout_wanted && curthread->td_proc != pageproc) { 1712 vm_pageout_wanted = true; 1713 wakeup(&vm_pageout_wanted); 1714 } 1715 } 1716 1717 #if !defined(NO_SWAPPING) 1718 static void 1719 vm_req_vmdaemon(int req) 1720 { 1721 static int lastrun = 0; 1722 1723 mtx_lock(&vm_daemon_mtx); 1724 vm_pageout_req_swapout |= req; 1725 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 1726 wakeup(&vm_daemon_needed); 1727 lastrun = ticks; 1728 } 1729 mtx_unlock(&vm_daemon_mtx); 1730 } 1731 1732 static void 1733 vm_daemon(void) 1734 { 1735 struct rlimit rsslim; 1736 struct proc *p; 1737 struct thread *td; 1738 struct vmspace *vm; 1739 int breakout, swapout_flags, tryagain, attempts; 1740 #ifdef RACCT 1741 uint64_t rsize, ravailable; 1742 #endif 1743 1744 while (TRUE) { 1745 mtx_lock(&vm_daemon_mtx); 1746 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 1747 #ifdef RACCT 1748 racct_enable ? hz : 0 1749 #else 1750 0 1751 #endif 1752 ); 1753 swapout_flags = vm_pageout_req_swapout; 1754 vm_pageout_req_swapout = 0; 1755 mtx_unlock(&vm_daemon_mtx); 1756 if (swapout_flags) 1757 swapout_procs(swapout_flags); 1758 1759 /* 1760 * scan the processes for exceeding their rlimits or if 1761 * process is swapped out -- deactivate pages 1762 */ 1763 tryagain = 0; 1764 attempts = 0; 1765 again: 1766 attempts++; 1767 sx_slock(&allproc_lock); 1768 FOREACH_PROC_IN_SYSTEM(p) { 1769 vm_pindex_t limit, size; 1770 1771 /* 1772 * if this is a system process or if we have already 1773 * looked at this process, skip it. 1774 */ 1775 PROC_LOCK(p); 1776 if (p->p_state != PRS_NORMAL || 1777 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 1778 PROC_UNLOCK(p); 1779 continue; 1780 } 1781 /* 1782 * if the process is in a non-running type state, 1783 * don't touch it. 1784 */ 1785 breakout = 0; 1786 FOREACH_THREAD_IN_PROC(p, td) { 1787 thread_lock(td); 1788 if (!TD_ON_RUNQ(td) && 1789 !TD_IS_RUNNING(td) && 1790 !TD_IS_SLEEPING(td) && 1791 !TD_IS_SUSPENDED(td)) { 1792 thread_unlock(td); 1793 breakout = 1; 1794 break; 1795 } 1796 thread_unlock(td); 1797 } 1798 if (breakout) { 1799 PROC_UNLOCK(p); 1800 continue; 1801 } 1802 /* 1803 * get a limit 1804 */ 1805 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 1806 limit = OFF_TO_IDX( 1807 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 1808 1809 /* 1810 * let processes that are swapped out really be 1811 * swapped out set the limit to nothing (will force a 1812 * swap-out.) 1813 */ 1814 if ((p->p_flag & P_INMEM) == 0) 1815 limit = 0; /* XXX */ 1816 vm = vmspace_acquire_ref(p); 1817 _PHOLD_LITE(p); 1818 PROC_UNLOCK(p); 1819 if (vm == NULL) { 1820 PRELE(p); 1821 continue; 1822 } 1823 sx_sunlock(&allproc_lock); 1824 1825 size = vmspace_resident_count(vm); 1826 if (size >= limit) { 1827 vm_pageout_map_deactivate_pages( 1828 &vm->vm_map, limit); 1829 } 1830 #ifdef RACCT 1831 if (racct_enable) { 1832 rsize = IDX_TO_OFF(size); 1833 PROC_LOCK(p); 1834 racct_set(p, RACCT_RSS, rsize); 1835 ravailable = racct_get_available(p, RACCT_RSS); 1836 PROC_UNLOCK(p); 1837 if (rsize > ravailable) { 1838 /* 1839 * Don't be overly aggressive; this 1840 * might be an innocent process, 1841 * and the limit could've been exceeded 1842 * by some memory hog. Don't try 1843 * to deactivate more than 1/4th 1844 * of process' resident set size. 1845 */ 1846 if (attempts <= 8) { 1847 if (ravailable < rsize - 1848 (rsize / 4)) { 1849 ravailable = rsize - 1850 (rsize / 4); 1851 } 1852 } 1853 vm_pageout_map_deactivate_pages( 1854 &vm->vm_map, 1855 OFF_TO_IDX(ravailable)); 1856 /* Update RSS usage after paging out. */ 1857 size = vmspace_resident_count(vm); 1858 rsize = IDX_TO_OFF(size); 1859 PROC_LOCK(p); 1860 racct_set(p, RACCT_RSS, rsize); 1861 PROC_UNLOCK(p); 1862 if (rsize > ravailable) 1863 tryagain = 1; 1864 } 1865 } 1866 #endif 1867 vmspace_free(vm); 1868 sx_slock(&allproc_lock); 1869 PRELE(p); 1870 } 1871 sx_sunlock(&allproc_lock); 1872 if (tryagain != 0 && attempts <= 10) 1873 goto again; 1874 } 1875 } 1876 #endif /* !defined(NO_SWAPPING) */ 1877