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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/11.1/sys/vm/vm_pageout.c 320693 2017-07-05 19:24:53Z markj $"); 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, int *numpagedout); 123 static int vm_pageout_cluster(vm_page_t m); 124 static bool vm_pageout_scan(struct vm_domain *vmd, int pass); 125 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 126 int starting_page_shortage); 127 128 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init, 129 NULL); 130 131 struct proc *pageproc; 132 133 static struct kproc_desc page_kp = { 134 "pagedaemon", 135 vm_pageout, 136 &pageproc 137 }; 138 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, 139 &page_kp); 140 141 SDT_PROVIDER_DEFINE(vm); 142 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan); 143 144 #if !defined(NO_SWAPPING) 145 /* the kernel process "vm_daemon"*/ 146 static void vm_daemon(void); 147 static struct proc *vmproc; 148 149 static struct kproc_desc vm_kp = { 150 "vmdaemon", 151 vm_daemon, 152 &vmproc 153 }; 154 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); 155 #endif 156 157 /* Pagedaemon activity rates, in subdivisions of one second. */ 158 #define VM_LAUNDER_RATE 10 159 #define VM_INACT_SCAN_RATE 2 160 161 int vm_pageout_deficit; /* Estimated number of pages deficit */ 162 u_int vm_pageout_wakeup_thresh; 163 static int vm_pageout_oom_seq = 12; 164 bool vm_pageout_wanted; /* Event on which pageout daemon sleeps */ 165 bool vm_pages_needed; /* Are threads waiting for free pages? */ 166 167 /* Pending request for dirty page laundering. */ 168 static enum { 169 VM_LAUNDRY_IDLE, 170 VM_LAUNDRY_BACKGROUND, 171 VM_LAUNDRY_SHORTFALL 172 } vm_laundry_request = VM_LAUNDRY_IDLE; 173 174 #if !defined(NO_SWAPPING) 175 static int vm_pageout_req_swapout; /* XXX */ 176 static int vm_daemon_needed; 177 static struct mtx vm_daemon_mtx; 178 /* Allow for use by vm_pageout before vm_daemon is initialized. */ 179 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); 180 #endif 181 static int vm_pageout_update_period; 182 static int disable_swap_pageouts; 183 static int lowmem_period = 10; 184 static time_t lowmem_uptime; 185 186 #if defined(NO_SWAPPING) 187 static int vm_swap_enabled = 0; 188 static int vm_swap_idle_enabled = 0; 189 #else 190 static int vm_swap_enabled = 1; 191 static int vm_swap_idle_enabled = 0; 192 #endif 193 194 static int vm_panic_on_oom = 0; 195 196 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom, 197 CTLFLAG_RWTUN, &vm_panic_on_oom, 0, 198 "panic on out of memory instead of killing the largest process"); 199 200 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh, 201 CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0, 202 "free page threshold for waking up the pageout daemon"); 203 204 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period, 205 CTLFLAG_RW, &vm_pageout_update_period, 0, 206 "Maximum active LRU update period"); 207 208 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0, 209 "Low memory callback period"); 210 211 #if defined(NO_SWAPPING) 212 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 213 CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout"); 214 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 215 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 216 #else 217 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 218 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 219 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 220 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 221 #endif 222 223 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 224 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 225 226 static int pageout_lock_miss; 227 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 228 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 229 230 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq, 231 CTLFLAG_RW, &vm_pageout_oom_seq, 0, 232 "back-to-back calls to oom detector to start OOM"); 233 234 static int act_scan_laundry_weight = 3; 235 SYSCTL_INT(_vm, OID_AUTO, act_scan_laundry_weight, CTLFLAG_RW, 236 &act_scan_laundry_weight, 0, 237 "weight given to clean vs. dirty pages in active queue scans"); 238 239 static u_int vm_background_launder_target; 240 SYSCTL_UINT(_vm, OID_AUTO, background_launder_target, CTLFLAG_RW, 241 &vm_background_launder_target, 0, 242 "background laundering target, in pages"); 243 244 static u_int vm_background_launder_rate = 4096; 245 SYSCTL_UINT(_vm, OID_AUTO, background_launder_rate, CTLFLAG_RW, 246 &vm_background_launder_rate, 0, 247 "background laundering rate, in kilobytes per second"); 248 249 static u_int vm_background_launder_max = 20 * 1024; 250 SYSCTL_UINT(_vm, OID_AUTO, background_launder_max, CTLFLAG_RW, 251 &vm_background_launder_max, 0, "background laundering cap, in kilobytes"); 252 253 #define VM_PAGEOUT_PAGE_COUNT 16 254 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 255 256 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 257 SYSCTL_INT(_vm, OID_AUTO, max_wired, 258 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count"); 259 260 static u_int isqrt(u_int num); 261 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *); 262 static int vm_pageout_launder(struct vm_domain *vmd, int launder, 263 bool in_shortfall); 264 static void vm_pageout_laundry_worker(void *arg); 265 #if !defined(NO_SWAPPING) 266 static void vm_pageout_map_deactivate_pages(vm_map_t, long); 267 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long); 268 static void vm_req_vmdaemon(int req); 269 #endif 270 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *); 271 272 /* 273 * Initialize a dummy page for marking the caller's place in the specified 274 * paging queue. In principle, this function only needs to set the flag 275 * PG_MARKER. Nonetheless, it write busies and initializes the hold count 276 * to one as safety precautions. 277 */ 278 static void 279 vm_pageout_init_marker(vm_page_t marker, u_short queue) 280 { 281 282 bzero(marker, sizeof(*marker)); 283 marker->flags = PG_MARKER; 284 marker->busy_lock = VPB_SINGLE_EXCLUSIVER; 285 marker->queue = queue; 286 marker->hold_count = 1; 287 } 288 289 /* 290 * vm_pageout_fallback_object_lock: 291 * 292 * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is 293 * known to have failed and page queue must be either PQ_ACTIVE or 294 * PQ_INACTIVE. To avoid lock order violation, unlock the page queue 295 * while locking the vm object. Use marker page to detect page queue 296 * changes and maintain notion of next page on page queue. Return 297 * TRUE if no changes were detected, FALSE otherwise. vm object is 298 * locked on return. 299 * 300 * This function depends on both the lock portion of struct vm_object 301 * and normal struct vm_page being type stable. 302 */ 303 static boolean_t 304 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next) 305 { 306 struct vm_page marker; 307 struct vm_pagequeue *pq; 308 boolean_t unchanged; 309 u_short queue; 310 vm_object_t object; 311 312 queue = m->queue; 313 vm_pageout_init_marker(&marker, queue); 314 pq = vm_page_pagequeue(m); 315 object = m->object; 316 317 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 318 vm_pagequeue_unlock(pq); 319 vm_page_unlock(m); 320 VM_OBJECT_WLOCK(object); 321 vm_page_lock(m); 322 vm_pagequeue_lock(pq); 323 324 /* 325 * The page's object might have changed, and/or the page might 326 * have moved from its original position in the queue. If the 327 * page's object has changed, then the caller should abandon 328 * processing the page because the wrong object lock was 329 * acquired. Use the marker's plinks.q, not the page's, to 330 * determine if the page has been moved. The state of the 331 * page's plinks.q can be indeterminate; whereas, the marker's 332 * plinks.q must be valid. 333 */ 334 *next = TAILQ_NEXT(&marker, plinks.q); 335 unchanged = m->object == object && 336 m == TAILQ_PREV(&marker, pglist, plinks.q); 337 KASSERT(!unchanged || m->queue == queue, 338 ("page %p queue %d %d", m, queue, m->queue)); 339 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 340 return (unchanged); 341 } 342 343 /* 344 * Lock the page while holding the page queue lock. Use marker page 345 * to detect page queue changes and maintain notion of next page on 346 * page queue. Return TRUE if no changes were detected, FALSE 347 * otherwise. The page is locked on return. The page queue lock might 348 * be dropped and reacquired. 349 * 350 * This function depends on normal struct vm_page being type stable. 351 */ 352 static boolean_t 353 vm_pageout_page_lock(vm_page_t m, vm_page_t *next) 354 { 355 struct vm_page marker; 356 struct vm_pagequeue *pq; 357 boolean_t unchanged; 358 u_short queue; 359 360 vm_page_lock_assert(m, MA_NOTOWNED); 361 if (vm_page_trylock(m)) 362 return (TRUE); 363 364 queue = m->queue; 365 vm_pageout_init_marker(&marker, queue); 366 pq = vm_page_pagequeue(m); 367 368 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 369 vm_pagequeue_unlock(pq); 370 vm_page_lock(m); 371 vm_pagequeue_lock(pq); 372 373 /* Page queue might have changed. */ 374 *next = TAILQ_NEXT(&marker, plinks.q); 375 unchanged = m == TAILQ_PREV(&marker, pglist, plinks.q); 376 KASSERT(!unchanged || m->queue == queue, 377 ("page %p queue %d %d", m, queue, m->queue)); 378 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 379 return (unchanged); 380 } 381 382 /* 383 * Scan for pages at adjacent offsets within the given page's object that are 384 * eligible for laundering, form a cluster of these pages and the given page, 385 * and launder that cluster. 386 */ 387 static int 388 vm_pageout_cluster(vm_page_t m) 389 { 390 vm_object_t object; 391 vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps; 392 vm_pindex_t pindex; 393 int ib, is, page_base, pageout_count; 394 395 vm_page_assert_locked(m); 396 object = m->object; 397 VM_OBJECT_ASSERT_WLOCKED(object); 398 pindex = m->pindex; 399 400 /* 401 * We can't clean the page if it is busy or held. 402 */ 403 vm_page_assert_unbusied(m); 404 KASSERT(m->hold_count == 0, ("page %p is held", m)); 405 vm_page_unlock(m); 406 407 mc[vm_pageout_page_count] = pb = ps = m; 408 pageout_count = 1; 409 page_base = vm_pageout_page_count; 410 ib = 1; 411 is = 1; 412 413 /* 414 * We can cluster only if the page is not clean, busy, or held, and 415 * the page is in the laundry queue. 416 * 417 * During heavy mmap/modification loads the pageout 418 * daemon can really fragment the underlying file 419 * due to flushing pages out of order and not trying to 420 * align the clusters (which leaves sporadic out-of-order 421 * holes). To solve this problem we do the reverse scan 422 * first and attempt to align our cluster, then do a 423 * forward scan if room remains. 424 */ 425 more: 426 while (ib != 0 && pageout_count < vm_pageout_page_count) { 427 if (ib > pindex) { 428 ib = 0; 429 break; 430 } 431 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) { 432 ib = 0; 433 break; 434 } 435 vm_page_test_dirty(p); 436 if (p->dirty == 0) { 437 ib = 0; 438 break; 439 } 440 vm_page_lock(p); 441 if (!vm_page_in_laundry(p) || 442 p->hold_count != 0) { /* may be undergoing I/O */ 443 vm_page_unlock(p); 444 ib = 0; 445 break; 446 } 447 vm_page_unlock(p); 448 mc[--page_base] = pb = p; 449 ++pageout_count; 450 ++ib; 451 452 /* 453 * We are at an alignment boundary. Stop here, and switch 454 * directions. Do not clear ib. 455 */ 456 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 457 break; 458 } 459 while (pageout_count < vm_pageout_page_count && 460 pindex + is < object->size) { 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 (!vm_page_in_laundry(p) || 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 an alignment boundary. This catches 481 * boundary conditions. 482 */ 483 if (ib != 0 && pageout_count < vm_pageout_page_count) 484 goto more; 485 486 return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL, 487 NULL)); 488 } 489 490 /* 491 * vm_pageout_flush() - launder the given pages 492 * 493 * The given pages are laundered. Note that we setup for the start of 494 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 495 * reference count all in here rather then in the parent. If we want 496 * the parent to do more sophisticated things we may have to change 497 * the ordering. 498 * 499 * Returned runlen is the count of pages between mreq and first 500 * page after mreq with status VM_PAGER_AGAIN. 501 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL 502 * for any page in runlen set. 503 */ 504 int 505 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen, 506 boolean_t *eio) 507 { 508 vm_object_t object = mc[0]->object; 509 int pageout_status[count]; 510 int numpagedout = 0; 511 int i, runlen; 512 513 VM_OBJECT_ASSERT_WLOCKED(object); 514 515 /* 516 * Initiate I/O. Bump the vm_page_t->busy counter and 517 * mark the pages read-only. 518 * 519 * We do not have to fixup the clean/dirty bits here... we can 520 * allow the pager to do it after the I/O completes. 521 * 522 * NOTE! mc[i]->dirty may be partial or fragmented due to an 523 * edge case with file fragments. 524 */ 525 for (i = 0; i < count; i++) { 526 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, 527 ("vm_pageout_flush: partially invalid page %p index %d/%d", 528 mc[i], i, count)); 529 vm_page_sbusy(mc[i]); 530 pmap_remove_write(mc[i]); 531 } 532 vm_object_pip_add(object, count); 533 534 vm_pager_put_pages(object, mc, count, flags, pageout_status); 535 536 runlen = count - mreq; 537 if (eio != NULL) 538 *eio = FALSE; 539 for (i = 0; i < count; i++) { 540 vm_page_t mt = mc[i]; 541 542 KASSERT(pageout_status[i] == VM_PAGER_PEND || 543 !pmap_page_is_write_mapped(mt), 544 ("vm_pageout_flush: page %p is not write protected", mt)); 545 switch (pageout_status[i]) { 546 case VM_PAGER_OK: 547 vm_page_lock(mt); 548 if (vm_page_in_laundry(mt)) 549 vm_page_deactivate_noreuse(mt); 550 vm_page_unlock(mt); 551 /* FALLTHROUGH */ 552 case VM_PAGER_PEND: 553 numpagedout++; 554 break; 555 case VM_PAGER_BAD: 556 /* 557 * The page is outside the object's range. We pretend 558 * that the page out worked and clean the page, so the 559 * changes will be lost if the page is reclaimed by 560 * the page daemon. 561 */ 562 vm_page_undirty(mt); 563 vm_page_lock(mt); 564 if (vm_page_in_laundry(mt)) 565 vm_page_deactivate_noreuse(mt); 566 vm_page_unlock(mt); 567 break; 568 case VM_PAGER_ERROR: 569 case VM_PAGER_FAIL: 570 /* 571 * If the page couldn't be paged out, then reactivate 572 * it so that it doesn't clog the laundry and inactive 573 * queues. (We will try paging it out again later). 574 */ 575 vm_page_lock(mt); 576 vm_page_activate(mt); 577 vm_page_unlock(mt); 578 if (eio != NULL && i >= mreq && i - mreq < runlen) 579 *eio = TRUE; 580 break; 581 case VM_PAGER_AGAIN: 582 if (i >= mreq && i - mreq < runlen) 583 runlen = i - mreq; 584 break; 585 } 586 587 /* 588 * If the operation is still going, leave the page busy to 589 * block all other accesses. Also, leave the paging in 590 * progress indicator set so that we don't attempt an object 591 * collapse. 592 */ 593 if (pageout_status[i] != VM_PAGER_PEND) { 594 vm_object_pip_wakeup(object); 595 vm_page_sunbusy(mt); 596 } 597 } 598 if (prunlen != NULL) 599 *prunlen = runlen; 600 return (numpagedout); 601 } 602 603 #if !defined(NO_SWAPPING) 604 /* 605 * vm_pageout_object_deactivate_pages 606 * 607 * Deactivate enough pages to satisfy the inactive target 608 * requirements. 609 * 610 * The object and map must be locked. 611 */ 612 static void 613 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 614 long desired) 615 { 616 vm_object_t backing_object, object; 617 vm_page_t p; 618 int act_delta, remove_mode; 619 620 VM_OBJECT_ASSERT_LOCKED(first_object); 621 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 622 return; 623 for (object = first_object;; object = backing_object) { 624 if (pmap_resident_count(pmap) <= desired) 625 goto unlock_return; 626 VM_OBJECT_ASSERT_LOCKED(object); 627 if ((object->flags & OBJ_UNMANAGED) != 0 || 628 object->paging_in_progress != 0) 629 goto unlock_return; 630 631 remove_mode = 0; 632 if (object->shadow_count > 1) 633 remove_mode = 1; 634 /* 635 * Scan the object's entire memory queue. 636 */ 637 TAILQ_FOREACH(p, &object->memq, listq) { 638 if (pmap_resident_count(pmap) <= desired) 639 goto unlock_return; 640 if (vm_page_busied(p)) 641 continue; 642 PCPU_INC(cnt.v_pdpages); 643 vm_page_lock(p); 644 if (p->wire_count != 0 || p->hold_count != 0 || 645 !pmap_page_exists_quick(pmap, p)) { 646 vm_page_unlock(p); 647 continue; 648 } 649 act_delta = pmap_ts_referenced(p); 650 if ((p->aflags & PGA_REFERENCED) != 0) { 651 if (act_delta == 0) 652 act_delta = 1; 653 vm_page_aflag_clear(p, PGA_REFERENCED); 654 } 655 if (!vm_page_active(p) && act_delta != 0) { 656 vm_page_activate(p); 657 p->act_count += act_delta; 658 } else if (vm_page_active(p)) { 659 if (act_delta == 0) { 660 p->act_count -= min(p->act_count, 661 ACT_DECLINE); 662 if (!remove_mode && p->act_count == 0) { 663 pmap_remove_all(p); 664 vm_page_deactivate(p); 665 } else 666 vm_page_requeue(p); 667 } else { 668 vm_page_activate(p); 669 if (p->act_count < ACT_MAX - 670 ACT_ADVANCE) 671 p->act_count += ACT_ADVANCE; 672 vm_page_requeue(p); 673 } 674 } else if (vm_page_inactive(p)) 675 pmap_remove_all(p); 676 vm_page_unlock(p); 677 } 678 if ((backing_object = object->backing_object) == NULL) 679 goto unlock_return; 680 VM_OBJECT_RLOCK(backing_object); 681 if (object != first_object) 682 VM_OBJECT_RUNLOCK(object); 683 } 684 unlock_return: 685 if (object != first_object) 686 VM_OBJECT_RUNLOCK(object); 687 } 688 689 /* 690 * deactivate some number of pages in a map, try to do it fairly, but 691 * that is really hard to do. 692 */ 693 static void 694 vm_pageout_map_deactivate_pages(map, desired) 695 vm_map_t map; 696 long desired; 697 { 698 vm_map_entry_t tmpe; 699 vm_object_t obj, bigobj; 700 int nothingwired; 701 702 if (!vm_map_trylock(map)) 703 return; 704 705 bigobj = NULL; 706 nothingwired = TRUE; 707 708 /* 709 * first, search out the biggest object, and try to free pages from 710 * that. 711 */ 712 tmpe = map->header.next; 713 while (tmpe != &map->header) { 714 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 715 obj = tmpe->object.vm_object; 716 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 717 if (obj->shadow_count <= 1 && 718 (bigobj == NULL || 719 bigobj->resident_page_count < obj->resident_page_count)) { 720 if (bigobj != NULL) 721 VM_OBJECT_RUNLOCK(bigobj); 722 bigobj = obj; 723 } else 724 VM_OBJECT_RUNLOCK(obj); 725 } 726 } 727 if (tmpe->wired_count > 0) 728 nothingwired = FALSE; 729 tmpe = tmpe->next; 730 } 731 732 if (bigobj != NULL) { 733 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired); 734 VM_OBJECT_RUNLOCK(bigobj); 735 } 736 /* 737 * Next, hunt around for other pages to deactivate. We actually 738 * do this search sort of wrong -- .text first is not the best idea. 739 */ 740 tmpe = map->header.next; 741 while (tmpe != &map->header) { 742 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 743 break; 744 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 745 obj = tmpe->object.vm_object; 746 if (obj != NULL) { 747 VM_OBJECT_RLOCK(obj); 748 vm_pageout_object_deactivate_pages(map->pmap, obj, desired); 749 VM_OBJECT_RUNLOCK(obj); 750 } 751 } 752 tmpe = tmpe->next; 753 } 754 755 /* 756 * Remove all mappings if a process is swapped out, this will free page 757 * table pages. 758 */ 759 if (desired == 0 && nothingwired) { 760 pmap_remove(vm_map_pmap(map), vm_map_min(map), 761 vm_map_max(map)); 762 } 763 764 vm_map_unlock(map); 765 } 766 #endif /* !defined(NO_SWAPPING) */ 767 768 /* 769 * Attempt to acquire all of the necessary locks to launder a page and 770 * then call through the clustering layer to PUTPAGES. Wait a short 771 * time for a vnode lock. 772 * 773 * Requires the page and object lock on entry, releases both before return. 774 * Returns 0 on success and an errno otherwise. 775 */ 776 static int 777 vm_pageout_clean(vm_page_t m, int *numpagedout) 778 { 779 struct vnode *vp; 780 struct mount *mp; 781 vm_object_t object; 782 vm_pindex_t pindex; 783 int error, lockmode; 784 785 vm_page_assert_locked(m); 786 object = m->object; 787 VM_OBJECT_ASSERT_WLOCKED(object); 788 error = 0; 789 vp = NULL; 790 mp = NULL; 791 792 /* 793 * The object is already known NOT to be dead. It 794 * is possible for the vget() to block the whole 795 * pageout daemon, but the new low-memory handling 796 * code should prevent it. 797 * 798 * We can't wait forever for the vnode lock, we might 799 * deadlock due to a vn_read() getting stuck in 800 * vm_wait while holding this vnode. We skip the 801 * vnode if we can't get it in a reasonable amount 802 * of time. 803 */ 804 if (object->type == OBJT_VNODE) { 805 vm_page_unlock(m); 806 vp = object->handle; 807 if (vp->v_type == VREG && 808 vn_start_write(vp, &mp, V_NOWAIT) != 0) { 809 mp = NULL; 810 error = EDEADLK; 811 goto unlock_all; 812 } 813 KASSERT(mp != NULL, 814 ("vp %p with NULL v_mount", vp)); 815 vm_object_reference_locked(object); 816 pindex = m->pindex; 817 VM_OBJECT_WUNLOCK(object); 818 lockmode = MNT_SHARED_WRITES(vp->v_mount) ? 819 LK_SHARED : LK_EXCLUSIVE; 820 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) { 821 vp = NULL; 822 error = EDEADLK; 823 goto unlock_mp; 824 } 825 VM_OBJECT_WLOCK(object); 826 vm_page_lock(m); 827 /* 828 * While the object and page were unlocked, the page 829 * may have been: 830 * (1) moved to a different queue, 831 * (2) reallocated to a different object, 832 * (3) reallocated to a different offset, or 833 * (4) cleaned. 834 */ 835 if (!vm_page_in_laundry(m) || m->object != object || 836 m->pindex != pindex || m->dirty == 0) { 837 vm_page_unlock(m); 838 error = ENXIO; 839 goto unlock_all; 840 } 841 842 /* 843 * The page may have been busied or held while the object 844 * and page locks were released. 845 */ 846 if (vm_page_busied(m) || m->hold_count != 0) { 847 vm_page_unlock(m); 848 error = EBUSY; 849 goto unlock_all; 850 } 851 } 852 853 /* 854 * If a page is dirty, then it is either being washed 855 * (but not yet cleaned) or it is still in the 856 * laundry. If it is still in the laundry, then we 857 * start the cleaning operation. 858 */ 859 if ((*numpagedout = vm_pageout_cluster(m)) == 0) 860 error = EIO; 861 862 unlock_all: 863 VM_OBJECT_WUNLOCK(object); 864 865 unlock_mp: 866 vm_page_lock_assert(m, MA_NOTOWNED); 867 if (mp != NULL) { 868 if (vp != NULL) 869 vput(vp); 870 vm_object_deallocate(object); 871 vn_finished_write(mp); 872 } 873 874 return (error); 875 } 876 877 /* 878 * Attempt to launder the specified number of pages. 879 * 880 * Returns the number of pages successfully laundered. 881 */ 882 static int 883 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall) 884 { 885 struct vm_pagequeue *pq; 886 vm_object_t object; 887 vm_page_t m, next; 888 int act_delta, error, maxscan, numpagedout, starting_target; 889 int vnodes_skipped; 890 bool pageout_ok, queue_locked; 891 892 starting_target = launder; 893 vnodes_skipped = 0; 894 895 /* 896 * Scan the laundry queue for pages eligible to be laundered. We stop 897 * once the target number of dirty pages have been laundered, or once 898 * we've reached the end of the queue. A single iteration of this loop 899 * may cause more than one page to be laundered because of clustering. 900 * 901 * maxscan ensures that we don't re-examine requeued pages. Any 902 * additional pages written as part of a cluster are subtracted from 903 * maxscan since they must be taken from the laundry queue. 904 */ 905 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY]; 906 maxscan = pq->pq_cnt; 907 908 vm_pagequeue_lock(pq); 909 queue_locked = true; 910 for (m = TAILQ_FIRST(&pq->pq_pl); 911 m != NULL && maxscan-- > 0 && launder > 0; 912 m = next) { 913 vm_pagequeue_assert_locked(pq); 914 KASSERT(queue_locked, ("unlocked laundry queue")); 915 KASSERT(vm_page_in_laundry(m), 916 ("page %p has an inconsistent queue", m)); 917 next = TAILQ_NEXT(m, plinks.q); 918 if ((m->flags & PG_MARKER) != 0) 919 continue; 920 KASSERT((m->flags & PG_FICTITIOUS) == 0, 921 ("PG_FICTITIOUS page %p cannot be in laundry queue", m)); 922 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 923 ("VPO_UNMANAGED page %p cannot be in laundry queue", m)); 924 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) { 925 vm_page_unlock(m); 926 continue; 927 } 928 object = m->object; 929 if ((!VM_OBJECT_TRYWLOCK(object) && 930 (!vm_pageout_fallback_object_lock(m, &next) || 931 m->hold_count != 0)) || vm_page_busied(m)) { 932 VM_OBJECT_WUNLOCK(object); 933 vm_page_unlock(m); 934 continue; 935 } 936 937 /* 938 * Unlock the laundry queue, invalidating the 'next' pointer. 939 * Use a marker to remember our place in the laundry queue. 940 */ 941 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_laundry_marker, 942 plinks.q); 943 vm_pagequeue_unlock(pq); 944 queue_locked = false; 945 946 /* 947 * Invalid pages can be easily freed. They cannot be 948 * mapped; vm_page_free() asserts this. 949 */ 950 if (m->valid == 0) 951 goto free_page; 952 953 /* 954 * If the page has been referenced and the object is not dead, 955 * reactivate or requeue the page depending on whether the 956 * object is mapped. 957 */ 958 if ((m->aflags & PGA_REFERENCED) != 0) { 959 vm_page_aflag_clear(m, PGA_REFERENCED); 960 act_delta = 1; 961 } else 962 act_delta = 0; 963 if (object->ref_count != 0) 964 act_delta += pmap_ts_referenced(m); 965 else { 966 KASSERT(!pmap_page_is_mapped(m), 967 ("page %p is mapped", m)); 968 } 969 if (act_delta != 0) { 970 if (object->ref_count != 0) { 971 PCPU_INC(cnt.v_reactivated); 972 vm_page_activate(m); 973 974 /* 975 * Increase the activation count if the page 976 * was referenced while in the laundry queue. 977 * This makes it less likely that the page will 978 * be returned prematurely to the inactive 979 * queue. 980 */ 981 m->act_count += act_delta + ACT_ADVANCE; 982 983 /* 984 * If this was a background laundering, count 985 * activated pages towards our target. The 986 * purpose of background laundering is to ensure 987 * that pages are eventually cycled through the 988 * laundry queue, and an activation is a valid 989 * way out. 990 */ 991 if (!in_shortfall) 992 launder--; 993 goto drop_page; 994 } else if ((object->flags & OBJ_DEAD) == 0) 995 goto requeue_page; 996 } 997 998 /* 999 * If the page appears to be clean at the machine-independent 1000 * layer, then remove all of its mappings from the pmap in 1001 * anticipation of freeing it. If, however, any of the page's 1002 * mappings allow write access, then the page may still be 1003 * modified until the last of those mappings are removed. 1004 */ 1005 if (object->ref_count != 0) { 1006 vm_page_test_dirty(m); 1007 if (m->dirty == 0) 1008 pmap_remove_all(m); 1009 } 1010 1011 /* 1012 * Clean pages are freed, and dirty pages are paged out unless 1013 * they belong to a dead object. Requeueing dirty pages from 1014 * dead objects is pointless, as they are being paged out and 1015 * freed by the thread that destroyed the object. 1016 */ 1017 if (m->dirty == 0) { 1018 free_page: 1019 vm_page_free(m); 1020 PCPU_INC(cnt.v_dfree); 1021 } else if ((object->flags & OBJ_DEAD) == 0) { 1022 if (object->type != OBJT_SWAP && 1023 object->type != OBJT_DEFAULT) 1024 pageout_ok = true; 1025 else if (disable_swap_pageouts) 1026 pageout_ok = false; 1027 else 1028 pageout_ok = true; 1029 if (!pageout_ok) { 1030 requeue_page: 1031 vm_pagequeue_lock(pq); 1032 queue_locked = true; 1033 vm_page_requeue_locked(m); 1034 goto drop_page; 1035 } 1036 1037 /* 1038 * Form a cluster with adjacent, dirty pages from the 1039 * same object, and page out that entire cluster. 1040 * 1041 * The adjacent, dirty pages must also be in the 1042 * laundry. However, their mappings are not checked 1043 * for new references. Consequently, a recently 1044 * referenced page may be paged out. However, that 1045 * page will not be prematurely reclaimed. After page 1046 * out, the page will be placed in the inactive queue, 1047 * where any new references will be detected and the 1048 * page reactivated. 1049 */ 1050 error = vm_pageout_clean(m, &numpagedout); 1051 if (error == 0) { 1052 launder -= numpagedout; 1053 maxscan -= numpagedout - 1; 1054 } else if (error == EDEADLK) { 1055 pageout_lock_miss++; 1056 vnodes_skipped++; 1057 } 1058 goto relock_queue; 1059 } 1060 drop_page: 1061 vm_page_unlock(m); 1062 VM_OBJECT_WUNLOCK(object); 1063 relock_queue: 1064 if (!queue_locked) { 1065 vm_pagequeue_lock(pq); 1066 queue_locked = true; 1067 } 1068 next = TAILQ_NEXT(&vmd->vmd_laundry_marker, plinks.q); 1069 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_laundry_marker, plinks.q); 1070 } 1071 vm_pagequeue_unlock(pq); 1072 1073 /* 1074 * Wakeup the sync daemon if we skipped a vnode in a writeable object 1075 * and we didn't launder enough pages. 1076 */ 1077 if (vnodes_skipped > 0 && launder > 0) 1078 (void)speedup_syncer(); 1079 1080 return (starting_target - launder); 1081 } 1082 1083 /* 1084 * Compute the integer square root. 1085 */ 1086 static u_int 1087 isqrt(u_int num) 1088 { 1089 u_int bit, root, tmp; 1090 1091 bit = 1u << ((NBBY * sizeof(u_int)) - 2); 1092 while (bit > num) 1093 bit >>= 2; 1094 root = 0; 1095 while (bit != 0) { 1096 tmp = root + bit; 1097 root >>= 1; 1098 if (num >= tmp) { 1099 num -= tmp; 1100 root += bit; 1101 } 1102 bit >>= 2; 1103 } 1104 return (root); 1105 } 1106 1107 /* 1108 * Perform the work of the laundry thread: periodically wake up and determine 1109 * whether any pages need to be laundered. If so, determine the number of pages 1110 * that need to be laundered, and launder them. 1111 */ 1112 static void 1113 vm_pageout_laundry_worker(void *arg) 1114 { 1115 struct vm_domain *domain; 1116 struct vm_pagequeue *pq; 1117 uint64_t nclean, ndirty; 1118 u_int last_launder, wakeups; 1119 int domidx, last_target, launder, shortfall, shortfall_cycle, target; 1120 bool in_shortfall; 1121 1122 domidx = (uintptr_t)arg; 1123 domain = &vm_dom[domidx]; 1124 pq = &domain->vmd_pagequeues[PQ_LAUNDRY]; 1125 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1126 vm_pageout_init_marker(&domain->vmd_laundry_marker, PQ_LAUNDRY); 1127 1128 shortfall = 0; 1129 in_shortfall = false; 1130 shortfall_cycle = 0; 1131 target = 0; 1132 last_launder = 0; 1133 1134 /* 1135 * The pageout laundry worker is never done, so loop forever. 1136 */ 1137 for (;;) { 1138 KASSERT(target >= 0, ("negative target %d", target)); 1139 KASSERT(shortfall_cycle >= 0, 1140 ("negative cycle %d", shortfall_cycle)); 1141 launder = 0; 1142 wakeups = VM_METER_PCPU_CNT(v_pdwakeups); 1143 1144 /* 1145 * First determine whether we need to launder pages to meet a 1146 * shortage of free pages. 1147 */ 1148 if (shortfall > 0) { 1149 in_shortfall = true; 1150 shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE; 1151 target = shortfall; 1152 } else if (!in_shortfall) 1153 goto trybackground; 1154 else if (shortfall_cycle == 0 || vm_laundry_target() <= 0) { 1155 /* 1156 * We recently entered shortfall and began laundering 1157 * pages. If we have completed that laundering run 1158 * (and we are no longer in shortfall) or we have met 1159 * our laundry target through other activity, then we 1160 * can stop laundering pages. 1161 */ 1162 in_shortfall = false; 1163 target = 0; 1164 goto trybackground; 1165 } 1166 last_launder = wakeups; 1167 launder = target / shortfall_cycle--; 1168 goto dolaundry; 1169 1170 /* 1171 * There's no immediate need to launder any pages; see if we 1172 * meet the conditions to perform background laundering: 1173 * 1174 * 1. The ratio of dirty to clean inactive pages exceeds the 1175 * background laundering threshold and the pagedaemon has 1176 * been woken up to reclaim pages since our last 1177 * laundering, or 1178 * 2. we haven't yet reached the target of the current 1179 * background laundering run. 1180 * 1181 * The background laundering threshold is not a constant. 1182 * Instead, it is a slowly growing function of the number of 1183 * page daemon wakeups since the last laundering. Thus, as the 1184 * ratio of dirty to clean inactive pages grows, the amount of 1185 * memory pressure required to trigger laundering decreases. 1186 */ 1187 trybackground: 1188 nclean = vm_cnt.v_inactive_count + vm_cnt.v_free_count; 1189 ndirty = vm_cnt.v_laundry_count; 1190 if (target == 0 && wakeups != last_launder && 1191 ndirty * isqrt(wakeups - last_launder) >= nclean) { 1192 target = vm_background_launder_target; 1193 } 1194 1195 /* 1196 * We have a non-zero background laundering target. If we've 1197 * laundered up to our maximum without observing a page daemon 1198 * wakeup, just stop. This is a safety belt that ensures we 1199 * don't launder an excessive amount if memory pressure is low 1200 * and the ratio of dirty to clean pages is large. Otherwise, 1201 * proceed at the background laundering rate. 1202 */ 1203 if (target > 0) { 1204 if (wakeups != last_launder) { 1205 last_launder = wakeups; 1206 last_target = target; 1207 } else if (last_target - target >= 1208 vm_background_launder_max * PAGE_SIZE / 1024) { 1209 target = 0; 1210 } 1211 launder = vm_background_launder_rate * PAGE_SIZE / 1024; 1212 launder /= VM_LAUNDER_RATE; 1213 if (launder > target) 1214 launder = target; 1215 } 1216 1217 dolaundry: 1218 if (launder > 0) { 1219 /* 1220 * Because of I/O clustering, the number of laundered 1221 * pages could exceed "target" by the maximum size of 1222 * a cluster minus one. 1223 */ 1224 target -= min(vm_pageout_launder(domain, launder, 1225 in_shortfall), target); 1226 pause("laundp", hz / VM_LAUNDER_RATE); 1227 } 1228 1229 /* 1230 * If we're not currently laundering pages and the page daemon 1231 * hasn't posted a new request, sleep until the page daemon 1232 * kicks us. 1233 */ 1234 vm_pagequeue_lock(pq); 1235 if (target == 0 && vm_laundry_request == VM_LAUNDRY_IDLE) 1236 (void)mtx_sleep(&vm_laundry_request, 1237 vm_pagequeue_lockptr(pq), PVM, "launds", 0); 1238 1239 /* 1240 * If the pagedaemon has indicated that it's in shortfall, start 1241 * a shortfall laundering unless we're already in the middle of 1242 * one. This may preempt a background laundering. 1243 */ 1244 if (vm_laundry_request == VM_LAUNDRY_SHORTFALL && 1245 (!in_shortfall || shortfall_cycle == 0)) { 1246 shortfall = vm_laundry_target() + vm_pageout_deficit; 1247 target = 0; 1248 } else 1249 shortfall = 0; 1250 1251 if (target == 0) 1252 vm_laundry_request = VM_LAUNDRY_IDLE; 1253 vm_pagequeue_unlock(pq); 1254 } 1255 } 1256 1257 /* 1258 * vm_pageout_scan does the dirty work for the pageout daemon. 1259 * 1260 * pass == 0: Update active LRU/deactivate pages 1261 * pass >= 1: Free inactive pages 1262 * 1263 * Returns true if pass was zero or enough pages were freed by the inactive 1264 * queue scan to meet the target. 1265 */ 1266 static bool 1267 vm_pageout_scan(struct vm_domain *vmd, int pass) 1268 { 1269 vm_page_t m, next; 1270 struct vm_pagequeue *pq; 1271 vm_object_t object; 1272 long min_scan; 1273 int act_delta, addl_page_shortage, deficit, inactq_shortage, maxscan; 1274 int page_shortage, scan_tick, scanned, starting_page_shortage; 1275 boolean_t queue_locked; 1276 1277 /* 1278 * If we need to reclaim memory ask kernel caches to return 1279 * some. We rate limit to avoid thrashing. 1280 */ 1281 if (vmd == &vm_dom[0] && pass > 0 && 1282 (time_uptime - lowmem_uptime) >= lowmem_period) { 1283 /* 1284 * Decrease registered cache sizes. 1285 */ 1286 SDT_PROBE0(vm, , , vm__lowmem_scan); 1287 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES); 1288 /* 1289 * We do this explicitly after the caches have been 1290 * drained above. 1291 */ 1292 uma_reclaim(); 1293 lowmem_uptime = time_uptime; 1294 } 1295 1296 /* 1297 * The addl_page_shortage is the number of temporarily 1298 * stuck pages in the inactive queue. In other words, the 1299 * number of pages from the inactive count that should be 1300 * discounted in setting the target for the active queue scan. 1301 */ 1302 addl_page_shortage = 0; 1303 1304 /* 1305 * Calculate the number of pages that we want to free. This number 1306 * can be negative if many pages are freed between the wakeup call to 1307 * the page daemon and this calculation. 1308 */ 1309 if (pass > 0) { 1310 deficit = atomic_readandclear_int(&vm_pageout_deficit); 1311 page_shortage = vm_paging_target() + deficit; 1312 } else 1313 page_shortage = deficit = 0; 1314 starting_page_shortage = page_shortage; 1315 1316 /* 1317 * Start scanning the inactive queue for pages that we can free. The 1318 * scan will stop when we reach the target or we have scanned the 1319 * entire queue. (Note that m->act_count is not used to make 1320 * decisions for the inactive queue, only for the active queue.) 1321 */ 1322 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 1323 maxscan = pq->pq_cnt; 1324 vm_pagequeue_lock(pq); 1325 queue_locked = TRUE; 1326 for (m = TAILQ_FIRST(&pq->pq_pl); 1327 m != NULL && maxscan-- > 0 && page_shortage > 0; 1328 m = next) { 1329 vm_pagequeue_assert_locked(pq); 1330 KASSERT(queue_locked, ("unlocked inactive queue")); 1331 KASSERT(vm_page_inactive(m), ("Inactive queue %p", m)); 1332 1333 PCPU_INC(cnt.v_pdpages); 1334 next = TAILQ_NEXT(m, plinks.q); 1335 1336 /* 1337 * skip marker pages 1338 */ 1339 if (m->flags & PG_MARKER) 1340 continue; 1341 1342 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1343 ("Fictitious page %p cannot be in inactive queue", m)); 1344 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1345 ("Unmanaged page %p cannot be in inactive queue", m)); 1346 1347 /* 1348 * The page or object lock acquisitions fail if the 1349 * page was removed from the queue or moved to a 1350 * different position within the queue. In either 1351 * case, addl_page_shortage should not be incremented. 1352 */ 1353 if (!vm_pageout_page_lock(m, &next)) 1354 goto unlock_page; 1355 else if (m->hold_count != 0) { 1356 /* 1357 * Held pages are essentially stuck in the 1358 * queue. So, they ought to be discounted 1359 * from the inactive count. See the 1360 * calculation of inactq_shortage before the 1361 * loop over the active queue below. 1362 */ 1363 addl_page_shortage++; 1364 goto unlock_page; 1365 } 1366 object = m->object; 1367 if (!VM_OBJECT_TRYWLOCK(object)) { 1368 if (!vm_pageout_fallback_object_lock(m, &next)) 1369 goto unlock_object; 1370 else if (m->hold_count != 0) { 1371 addl_page_shortage++; 1372 goto unlock_object; 1373 } 1374 } 1375 if (vm_page_busied(m)) { 1376 /* 1377 * Don't mess with busy pages. Leave them at 1378 * the front of the queue. Most likely, they 1379 * are being paged out and will leave the 1380 * queue shortly after the scan finishes. So, 1381 * they ought to be discounted from the 1382 * inactive count. 1383 */ 1384 addl_page_shortage++; 1385 unlock_object: 1386 VM_OBJECT_WUNLOCK(object); 1387 unlock_page: 1388 vm_page_unlock(m); 1389 continue; 1390 } 1391 KASSERT(m->hold_count == 0, ("Held page %p", m)); 1392 1393 /* 1394 * Dequeue the inactive page and unlock the inactive page 1395 * queue, invalidating the 'next' pointer. Dequeueing the 1396 * page here avoids a later reacquisition (and release) of 1397 * the inactive page queue lock when vm_page_activate(), 1398 * vm_page_free(), or vm_page_launder() is called. Use a 1399 * marker to remember our place in the inactive queue. 1400 */ 1401 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q); 1402 vm_page_dequeue_locked(m); 1403 vm_pagequeue_unlock(pq); 1404 queue_locked = FALSE; 1405 1406 /* 1407 * Invalid pages can be easily freed. They cannot be 1408 * mapped, vm_page_free() asserts this. 1409 */ 1410 if (m->valid == 0) 1411 goto free_page; 1412 1413 /* 1414 * If the page has been referenced and the object is not dead, 1415 * reactivate or requeue the page depending on whether the 1416 * object is mapped. 1417 */ 1418 if ((m->aflags & PGA_REFERENCED) != 0) { 1419 vm_page_aflag_clear(m, PGA_REFERENCED); 1420 act_delta = 1; 1421 } else 1422 act_delta = 0; 1423 if (object->ref_count != 0) { 1424 act_delta += pmap_ts_referenced(m); 1425 } else { 1426 KASSERT(!pmap_page_is_mapped(m), 1427 ("vm_pageout_scan: page %p is mapped", m)); 1428 } 1429 if (act_delta != 0) { 1430 if (object->ref_count != 0) { 1431 PCPU_INC(cnt.v_reactivated); 1432 vm_page_activate(m); 1433 1434 /* 1435 * Increase the activation count if the page 1436 * was referenced while in the inactive queue. 1437 * This makes it less likely that the page will 1438 * be returned prematurely to the inactive 1439 * queue. 1440 */ 1441 m->act_count += act_delta + ACT_ADVANCE; 1442 goto drop_page; 1443 } else if ((object->flags & OBJ_DEAD) == 0) { 1444 vm_pagequeue_lock(pq); 1445 queue_locked = TRUE; 1446 m->queue = PQ_INACTIVE; 1447 TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q); 1448 vm_pagequeue_cnt_inc(pq); 1449 goto drop_page; 1450 } 1451 } 1452 1453 /* 1454 * If the page appears to be clean at the machine-independent 1455 * layer, then remove all of its mappings from the pmap in 1456 * anticipation of freeing it. If, however, any of the page's 1457 * mappings allow write access, then the page may still be 1458 * modified until the last of those mappings are removed. 1459 */ 1460 if (object->ref_count != 0) { 1461 vm_page_test_dirty(m); 1462 if (m->dirty == 0) 1463 pmap_remove_all(m); 1464 } 1465 1466 /* 1467 * Clean pages can be freed, but dirty pages must be sent back 1468 * to the laundry, unless they belong to a dead object. 1469 * Requeueing dirty pages from dead objects is pointless, as 1470 * they are being paged out and freed by the thread that 1471 * destroyed the object. 1472 */ 1473 if (m->dirty == 0) { 1474 free_page: 1475 vm_page_free(m); 1476 PCPU_INC(cnt.v_dfree); 1477 --page_shortage; 1478 } else if ((object->flags & OBJ_DEAD) == 0) 1479 vm_page_launder(m); 1480 drop_page: 1481 vm_page_unlock(m); 1482 VM_OBJECT_WUNLOCK(object); 1483 if (!queue_locked) { 1484 vm_pagequeue_lock(pq); 1485 queue_locked = TRUE; 1486 } 1487 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q); 1488 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q); 1489 } 1490 vm_pagequeue_unlock(pq); 1491 1492 /* 1493 * Wake up the laundry thread so that it can perform any needed 1494 * laundering. If we didn't meet our target, we're in shortfall and 1495 * need to launder more aggressively. 1496 */ 1497 if (vm_laundry_request == VM_LAUNDRY_IDLE && 1498 starting_page_shortage > 0) { 1499 pq = &vm_dom[0].vmd_pagequeues[PQ_LAUNDRY]; 1500 vm_pagequeue_lock(pq); 1501 if (page_shortage > 0) { 1502 vm_laundry_request = VM_LAUNDRY_SHORTFALL; 1503 PCPU_INC(cnt.v_pdshortfalls); 1504 } else if (vm_laundry_request != VM_LAUNDRY_SHORTFALL) 1505 vm_laundry_request = VM_LAUNDRY_BACKGROUND; 1506 wakeup(&vm_laundry_request); 1507 vm_pagequeue_unlock(pq); 1508 } 1509 1510 #if !defined(NO_SWAPPING) 1511 /* 1512 * Wakeup the swapout daemon if we didn't free the targeted number of 1513 * pages. 1514 */ 1515 if (vm_swap_enabled && page_shortage > 0) 1516 vm_req_vmdaemon(VM_SWAP_NORMAL); 1517 #endif 1518 1519 /* 1520 * If the inactive queue scan fails repeatedly to meet its 1521 * target, kill the largest process. 1522 */ 1523 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1524 1525 /* 1526 * Compute the number of pages we want to try to move from the 1527 * active queue to either the inactive or laundry queue. 1528 * 1529 * When scanning active pages, we make clean pages count more heavily 1530 * towards the page shortage than dirty pages. This is because dirty 1531 * pages must be laundered before they can be reused and thus have less 1532 * utility when attempting to quickly alleviate a shortage. However, 1533 * this weighting also causes the scan to deactivate dirty pages more 1534 * more aggressively, improving the effectiveness of clustering and 1535 * ensuring that they can eventually be reused. 1536 */ 1537 inactq_shortage = vm_cnt.v_inactive_target - (vm_cnt.v_inactive_count + 1538 vm_cnt.v_laundry_count / act_scan_laundry_weight) + 1539 vm_paging_target() + deficit + addl_page_shortage; 1540 page_shortage *= act_scan_laundry_weight; 1541 1542 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1543 vm_pagequeue_lock(pq); 1544 maxscan = pq->pq_cnt; 1545 1546 /* 1547 * If we're just idle polling attempt to visit every 1548 * active page within 'update_period' seconds. 1549 */ 1550 scan_tick = ticks; 1551 if (vm_pageout_update_period != 0) { 1552 min_scan = pq->pq_cnt; 1553 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1554 min_scan /= hz * vm_pageout_update_period; 1555 } else 1556 min_scan = 0; 1557 if (min_scan > 0 || (inactq_shortage > 0 && maxscan > 0)) 1558 vmd->vmd_last_active_scan = scan_tick; 1559 1560 /* 1561 * Scan the active queue for pages that can be deactivated. Update 1562 * the per-page activity counter and use it to identify deactivation 1563 * candidates. Held pages may be deactivated. 1564 */ 1565 for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned < 1566 min_scan || (inactq_shortage > 0 && scanned < maxscan)); m = next, 1567 scanned++) { 1568 KASSERT(m->queue == PQ_ACTIVE, 1569 ("vm_pageout_scan: page %p isn't active", m)); 1570 next = TAILQ_NEXT(m, plinks.q); 1571 if ((m->flags & PG_MARKER) != 0) 1572 continue; 1573 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1574 ("Fictitious page %p cannot be in active queue", m)); 1575 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1576 ("Unmanaged page %p cannot be in active queue", m)); 1577 if (!vm_pageout_page_lock(m, &next)) { 1578 vm_page_unlock(m); 1579 continue; 1580 } 1581 1582 /* 1583 * The count for page daemon pages is updated after checking 1584 * the page for eligibility. 1585 */ 1586 PCPU_INC(cnt.v_pdpages); 1587 1588 /* 1589 * Check to see "how much" the page has been used. 1590 */ 1591 if ((m->aflags & PGA_REFERENCED) != 0) { 1592 vm_page_aflag_clear(m, PGA_REFERENCED); 1593 act_delta = 1; 1594 } else 1595 act_delta = 0; 1596 1597 /* 1598 * Perform an unsynchronized object ref count check. While 1599 * the page lock ensures that the page is not reallocated to 1600 * another object, in particular, one with unmanaged mappings 1601 * that cannot support pmap_ts_referenced(), two races are, 1602 * nonetheless, possible: 1603 * 1) The count was transitioning to zero, but we saw a non- 1604 * zero value. pmap_ts_referenced() will return zero 1605 * because the page is not mapped. 1606 * 2) The count was transitioning to one, but we saw zero. 1607 * This race delays the detection of a new reference. At 1608 * worst, we will deactivate and reactivate the page. 1609 */ 1610 if (m->object->ref_count != 0) 1611 act_delta += pmap_ts_referenced(m); 1612 1613 /* 1614 * Advance or decay the act_count based on recent usage. 1615 */ 1616 if (act_delta != 0) { 1617 m->act_count += ACT_ADVANCE + act_delta; 1618 if (m->act_count > ACT_MAX) 1619 m->act_count = ACT_MAX; 1620 } else 1621 m->act_count -= min(m->act_count, ACT_DECLINE); 1622 1623 /* 1624 * Move this page to the tail of the active, inactive or laundry 1625 * queue depending on usage. 1626 */ 1627 if (m->act_count == 0) { 1628 /* Dequeue to avoid later lock recursion. */ 1629 vm_page_dequeue_locked(m); 1630 1631 /* 1632 * When not short for inactive pages, let dirty pages go 1633 * through the inactive queue before moving to the 1634 * laundry queues. This gives them some extra time to 1635 * be reactivated, potentially avoiding an expensive 1636 * pageout. During a page shortage, the inactive queue 1637 * is necessarily small, so we may move dirty pages 1638 * directly to the laundry queue. 1639 */ 1640 if (inactq_shortage <= 0) 1641 vm_page_deactivate(m); 1642 else { 1643 /* 1644 * Calling vm_page_test_dirty() here would 1645 * require acquisition of the object's write 1646 * lock. However, during a page shortage, 1647 * directing dirty pages into the laundry 1648 * queue is only an optimization and not a 1649 * requirement. Therefore, we simply rely on 1650 * the opportunistic updates to the page's 1651 * dirty field by the pmap. 1652 */ 1653 if (m->dirty == 0) { 1654 vm_page_deactivate(m); 1655 inactq_shortage -= 1656 act_scan_laundry_weight; 1657 } else { 1658 vm_page_launder(m); 1659 inactq_shortage--; 1660 } 1661 } 1662 } else 1663 vm_page_requeue_locked(m); 1664 vm_page_unlock(m); 1665 } 1666 vm_pagequeue_unlock(pq); 1667 #if !defined(NO_SWAPPING) 1668 /* 1669 * Idle process swapout -- run once per second. 1670 */ 1671 if (vm_swap_idle_enabled) { 1672 static long lsec; 1673 if (time_second != lsec) { 1674 vm_req_vmdaemon(VM_SWAP_IDLE); 1675 lsec = time_second; 1676 } 1677 } 1678 #endif 1679 return (page_shortage <= 0); 1680 } 1681 1682 static int vm_pageout_oom_vote; 1683 1684 /* 1685 * The pagedaemon threads randlomly select one to perform the 1686 * OOM. Trying to kill processes before all pagedaemons 1687 * failed to reach free target is premature. 1688 */ 1689 static void 1690 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1691 int starting_page_shortage) 1692 { 1693 int old_vote; 1694 1695 if (starting_page_shortage <= 0 || starting_page_shortage != 1696 page_shortage) 1697 vmd->vmd_oom_seq = 0; 1698 else 1699 vmd->vmd_oom_seq++; 1700 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1701 if (vmd->vmd_oom) { 1702 vmd->vmd_oom = FALSE; 1703 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1704 } 1705 return; 1706 } 1707 1708 /* 1709 * Do not follow the call sequence until OOM condition is 1710 * cleared. 1711 */ 1712 vmd->vmd_oom_seq = 0; 1713 1714 if (vmd->vmd_oom) 1715 return; 1716 1717 vmd->vmd_oom = TRUE; 1718 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1719 if (old_vote != vm_ndomains - 1) 1720 return; 1721 1722 /* 1723 * The current pagedaemon thread is the last in the quorum to 1724 * start OOM. Initiate the selection and signaling of the 1725 * victim. 1726 */ 1727 vm_pageout_oom(VM_OOM_MEM); 1728 1729 /* 1730 * After one round of OOM terror, recall our vote. On the 1731 * next pass, current pagedaemon would vote again if the low 1732 * memory condition is still there, due to vmd_oom being 1733 * false. 1734 */ 1735 vmd->vmd_oom = FALSE; 1736 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1737 } 1738 1739 /* 1740 * The OOM killer is the page daemon's action of last resort when 1741 * memory allocation requests have been stalled for a prolonged period 1742 * of time because it cannot reclaim memory. This function computes 1743 * the approximate number of physical pages that could be reclaimed if 1744 * the specified address space is destroyed. 1745 * 1746 * Private, anonymous memory owned by the address space is the 1747 * principal resource that we expect to recover after an OOM kill. 1748 * Since the physical pages mapped by the address space's COW entries 1749 * are typically shared pages, they are unlikely to be released and so 1750 * they are not counted. 1751 * 1752 * To get to the point where the page daemon runs the OOM killer, its 1753 * efforts to write-back vnode-backed pages may have stalled. This 1754 * could be caused by a memory allocation deadlock in the write path 1755 * that might be resolved by an OOM kill. Therefore, physical pages 1756 * belonging to vnode-backed objects are counted, because they might 1757 * be freed without being written out first if the address space holds 1758 * the last reference to an unlinked vnode. 1759 * 1760 * Similarly, physical pages belonging to OBJT_PHYS objects are 1761 * counted because the address space might hold the last reference to 1762 * the object. 1763 */ 1764 static long 1765 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1766 { 1767 vm_map_t map; 1768 vm_map_entry_t entry; 1769 vm_object_t obj; 1770 long res; 1771 1772 map = &vmspace->vm_map; 1773 KASSERT(!map->system_map, ("system map")); 1774 sx_assert(&map->lock, SA_LOCKED); 1775 res = 0; 1776 for (entry = map->header.next; entry != &map->header; 1777 entry = entry->next) { 1778 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1779 continue; 1780 obj = entry->object.vm_object; 1781 if (obj == NULL) 1782 continue; 1783 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1784 obj->ref_count != 1) 1785 continue; 1786 switch (obj->type) { 1787 case OBJT_DEFAULT: 1788 case OBJT_SWAP: 1789 case OBJT_PHYS: 1790 case OBJT_VNODE: 1791 res += obj->resident_page_count; 1792 break; 1793 } 1794 } 1795 return (res); 1796 } 1797 1798 void 1799 vm_pageout_oom(int shortage) 1800 { 1801 struct proc *p, *bigproc; 1802 vm_offset_t size, bigsize; 1803 struct thread *td; 1804 struct vmspace *vm; 1805 1806 /* 1807 * We keep the process bigproc locked once we find it to keep anyone 1808 * from messing with it; however, there is a possibility of 1809 * deadlock if process B is bigproc and one of it's child processes 1810 * attempts to propagate a signal to B while we are waiting for A's 1811 * lock while walking this list. To avoid this, we don't block on 1812 * the process lock but just skip a process if it is already locked. 1813 */ 1814 bigproc = NULL; 1815 bigsize = 0; 1816 sx_slock(&allproc_lock); 1817 FOREACH_PROC_IN_SYSTEM(p) { 1818 int breakout; 1819 1820 PROC_LOCK(p); 1821 1822 /* 1823 * If this is a system, protected or killed process, skip it. 1824 */ 1825 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1826 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1827 p->p_pid == 1 || P_KILLED(p) || 1828 (p->p_pid < 48 && swap_pager_avail != 0)) { 1829 PROC_UNLOCK(p); 1830 continue; 1831 } 1832 /* 1833 * If the process is in a non-running type state, 1834 * don't touch it. Check all the threads individually. 1835 */ 1836 breakout = 0; 1837 FOREACH_THREAD_IN_PROC(p, td) { 1838 thread_lock(td); 1839 if (!TD_ON_RUNQ(td) && 1840 !TD_IS_RUNNING(td) && 1841 !TD_IS_SLEEPING(td) && 1842 !TD_IS_SUSPENDED(td) && 1843 !TD_IS_SWAPPED(td)) { 1844 thread_unlock(td); 1845 breakout = 1; 1846 break; 1847 } 1848 thread_unlock(td); 1849 } 1850 if (breakout) { 1851 PROC_UNLOCK(p); 1852 continue; 1853 } 1854 /* 1855 * get the process size 1856 */ 1857 vm = vmspace_acquire_ref(p); 1858 if (vm == NULL) { 1859 PROC_UNLOCK(p); 1860 continue; 1861 } 1862 _PHOLD_LITE(p); 1863 PROC_UNLOCK(p); 1864 sx_sunlock(&allproc_lock); 1865 if (!vm_map_trylock_read(&vm->vm_map)) { 1866 vmspace_free(vm); 1867 sx_slock(&allproc_lock); 1868 PRELE(p); 1869 continue; 1870 } 1871 size = vmspace_swap_count(vm); 1872 if (shortage == VM_OOM_MEM) 1873 size += vm_pageout_oom_pagecount(vm); 1874 vm_map_unlock_read(&vm->vm_map); 1875 vmspace_free(vm); 1876 sx_slock(&allproc_lock); 1877 1878 /* 1879 * If this process is bigger than the biggest one, 1880 * remember it. 1881 */ 1882 if (size > bigsize) { 1883 if (bigproc != NULL) 1884 PRELE(bigproc); 1885 bigproc = p; 1886 bigsize = size; 1887 } else { 1888 PRELE(p); 1889 } 1890 } 1891 sx_sunlock(&allproc_lock); 1892 if (bigproc != NULL) { 1893 if (vm_panic_on_oom != 0) 1894 panic("out of swap space"); 1895 PROC_LOCK(bigproc); 1896 killproc(bigproc, "out of swap space"); 1897 sched_nice(bigproc, PRIO_MIN); 1898 _PRELE(bigproc); 1899 PROC_UNLOCK(bigproc); 1900 wakeup(&vm_cnt.v_free_count); 1901 } 1902 } 1903 1904 static void 1905 vm_pageout_worker(void *arg) 1906 { 1907 struct vm_domain *domain; 1908 int domidx, pass; 1909 bool target_met; 1910 1911 domidx = (uintptr_t)arg; 1912 domain = &vm_dom[domidx]; 1913 pass = 0; 1914 target_met = true; 1915 1916 /* 1917 * XXXKIB It could be useful to bind pageout daemon threads to 1918 * the cores belonging to the domain, from which vm_page_array 1919 * is allocated. 1920 */ 1921 1922 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1923 domain->vmd_last_active_scan = ticks; 1924 vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE); 1925 vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE); 1926 TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl, 1927 &domain->vmd_inacthead, plinks.q); 1928 1929 /* 1930 * The pageout daemon worker is never done, so loop forever. 1931 */ 1932 while (TRUE) { 1933 mtx_lock(&vm_page_queue_free_mtx); 1934 1935 /* 1936 * Generally, after a level >= 1 scan, if there are enough 1937 * free pages to wakeup the waiters, then they are already 1938 * awake. A call to vm_page_free() during the scan awakened 1939 * them. However, in the following case, this wakeup serves 1940 * to bound the amount of time that a thread might wait. 1941 * Suppose a thread's call to vm_page_alloc() fails, but 1942 * before that thread calls VM_WAIT, enough pages are freed by 1943 * other threads to alleviate the free page shortage. The 1944 * thread will, nonetheless, wait until another page is freed 1945 * or this wakeup is performed. 1946 */ 1947 if (vm_pages_needed && !vm_page_count_min()) { 1948 vm_pages_needed = false; 1949 wakeup(&vm_cnt.v_free_count); 1950 } 1951 1952 /* 1953 * Do not clear vm_pageout_wanted until we reach our free page 1954 * target. Otherwise, we may be awakened over and over again, 1955 * wasting CPU time. 1956 */ 1957 if (vm_pageout_wanted && target_met) 1958 vm_pageout_wanted = false; 1959 1960 /* 1961 * Might the page daemon receive a wakeup call? 1962 */ 1963 if (vm_pageout_wanted) { 1964 /* 1965 * No. Either vm_pageout_wanted was set by another 1966 * thread during the previous scan, which must have 1967 * been a level 0 scan, or vm_pageout_wanted was 1968 * already set and the scan failed to free enough 1969 * pages. If we haven't yet performed a level >= 1 1970 * (page reclamation) scan, then increase the level 1971 * and scan again now. Otherwise, sleep a bit and 1972 * try again later. 1973 */ 1974 mtx_unlock(&vm_page_queue_free_mtx); 1975 if (pass >= 1) 1976 pause("psleep", hz / VM_INACT_SCAN_RATE); 1977 pass++; 1978 } else { 1979 /* 1980 * Yes. Sleep until pages need to be reclaimed or 1981 * have their reference stats updated. 1982 */ 1983 if (mtx_sleep(&vm_pageout_wanted, 1984 &vm_page_queue_free_mtx, PDROP | PVM, "psleep", 1985 hz) == 0) { 1986 PCPU_INC(cnt.v_pdwakeups); 1987 pass = 1; 1988 } else 1989 pass = 0; 1990 } 1991 1992 target_met = vm_pageout_scan(domain, pass); 1993 } 1994 } 1995 1996 /* 1997 * vm_pageout_init initialises basic pageout daemon settings. 1998 */ 1999 static void 2000 vm_pageout_init(void) 2001 { 2002 /* 2003 * Initialize some paging parameters. 2004 */ 2005 vm_cnt.v_interrupt_free_min = 2; 2006 if (vm_cnt.v_page_count < 2000) 2007 vm_pageout_page_count = 8; 2008 2009 /* 2010 * v_free_reserved needs to include enough for the largest 2011 * swap pager structures plus enough for any pv_entry structs 2012 * when paging. 2013 */ 2014 if (vm_cnt.v_page_count > 1024) 2015 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200; 2016 else 2017 vm_cnt.v_free_min = 4; 2018 vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 2019 vm_cnt.v_interrupt_free_min; 2020 vm_cnt.v_free_reserved = vm_pageout_page_count + 2021 vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768); 2022 vm_cnt.v_free_severe = vm_cnt.v_free_min / 2; 2023 vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved; 2024 vm_cnt.v_free_min += vm_cnt.v_free_reserved; 2025 vm_cnt.v_free_severe += vm_cnt.v_free_reserved; 2026 vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2; 2027 if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3) 2028 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3; 2029 2030 /* 2031 * Set the default wakeup threshold to be 10% above the minimum 2032 * page limit. This keeps the steady state out of shortfall. 2033 */ 2034 vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11; 2035 2036 /* 2037 * Set interval in seconds for active scan. We want to visit each 2038 * page at least once every ten minutes. This is to prevent worst 2039 * case paging behaviors with stale active LRU. 2040 */ 2041 if (vm_pageout_update_period == 0) 2042 vm_pageout_update_period = 600; 2043 2044 /* XXX does not really belong here */ 2045 if (vm_page_max_wired == 0) 2046 vm_page_max_wired = vm_cnt.v_free_count / 3; 2047 2048 /* 2049 * Target amount of memory to move out of the laundry queue during a 2050 * background laundering. This is proportional to the amount of system 2051 * memory. 2052 */ 2053 vm_background_launder_target = (vm_cnt.v_free_target - 2054 vm_cnt.v_free_min) / 10; 2055 } 2056 2057 /* 2058 * vm_pageout is the high level pageout daemon. 2059 */ 2060 static void 2061 vm_pageout(void) 2062 { 2063 int error; 2064 #ifdef VM_NUMA_ALLOC 2065 int i; 2066 #endif 2067 2068 swap_pager_swap_init(); 2069 error = kthread_add(vm_pageout_laundry_worker, NULL, curproc, NULL, 2070 0, 0, "laundry: dom0"); 2071 if (error != 0) 2072 panic("starting laundry for domain 0, error %d", error); 2073 #ifdef VM_NUMA_ALLOC 2074 for (i = 1; i < vm_ndomains; i++) { 2075 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i, 2076 curproc, NULL, 0, 0, "dom%d", i); 2077 if (error != 0) { 2078 panic("starting pageout for domain %d, error %d\n", 2079 i, error); 2080 } 2081 } 2082 #endif 2083 error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL, 2084 0, 0, "uma"); 2085 if (error != 0) 2086 panic("starting uma_reclaim helper, error %d\n", error); 2087 vm_pageout_worker((void *)(uintptr_t)0); 2088 } 2089 2090 /* 2091 * Unless the free page queue lock is held by the caller, this function 2092 * should be regarded as advisory. Specifically, the caller should 2093 * not msleep() on &vm_cnt.v_free_count following this function unless 2094 * the free page queue lock is held until the msleep() is performed. 2095 */ 2096 void 2097 pagedaemon_wakeup(void) 2098 { 2099 2100 if (!vm_pageout_wanted && curthread->td_proc != pageproc) { 2101 vm_pageout_wanted = true; 2102 wakeup(&vm_pageout_wanted); 2103 } 2104 } 2105 2106 #if !defined(NO_SWAPPING) 2107 static void 2108 vm_req_vmdaemon(int req) 2109 { 2110 static int lastrun = 0; 2111 2112 mtx_lock(&vm_daemon_mtx); 2113 vm_pageout_req_swapout |= req; 2114 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 2115 wakeup(&vm_daemon_needed); 2116 lastrun = ticks; 2117 } 2118 mtx_unlock(&vm_daemon_mtx); 2119 } 2120 2121 static void 2122 vm_daemon(void) 2123 { 2124 struct rlimit rsslim; 2125 struct proc *p; 2126 struct thread *td; 2127 struct vmspace *vm; 2128 int breakout, swapout_flags, tryagain, attempts; 2129 #ifdef RACCT 2130 uint64_t rsize, ravailable; 2131 #endif 2132 2133 while (TRUE) { 2134 mtx_lock(&vm_daemon_mtx); 2135 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 2136 #ifdef RACCT 2137 racct_enable ? hz : 0 2138 #else 2139 0 2140 #endif 2141 ); 2142 swapout_flags = vm_pageout_req_swapout; 2143 vm_pageout_req_swapout = 0; 2144 mtx_unlock(&vm_daemon_mtx); 2145 if (swapout_flags) 2146 swapout_procs(swapout_flags); 2147 2148 /* 2149 * scan the processes for exceeding their rlimits or if 2150 * process is swapped out -- deactivate pages 2151 */ 2152 tryagain = 0; 2153 attempts = 0; 2154 again: 2155 attempts++; 2156 sx_slock(&allproc_lock); 2157 FOREACH_PROC_IN_SYSTEM(p) { 2158 vm_pindex_t limit, size; 2159 2160 /* 2161 * if this is a system process or if we have already 2162 * looked at this process, skip it. 2163 */ 2164 PROC_LOCK(p); 2165 if (p->p_state != PRS_NORMAL || 2166 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 2167 PROC_UNLOCK(p); 2168 continue; 2169 } 2170 /* 2171 * if the process is in a non-running type state, 2172 * don't touch it. 2173 */ 2174 breakout = 0; 2175 FOREACH_THREAD_IN_PROC(p, td) { 2176 thread_lock(td); 2177 if (!TD_ON_RUNQ(td) && 2178 !TD_IS_RUNNING(td) && 2179 !TD_IS_SLEEPING(td) && 2180 !TD_IS_SUSPENDED(td)) { 2181 thread_unlock(td); 2182 breakout = 1; 2183 break; 2184 } 2185 thread_unlock(td); 2186 } 2187 if (breakout) { 2188 PROC_UNLOCK(p); 2189 continue; 2190 } 2191 /* 2192 * get a limit 2193 */ 2194 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 2195 limit = OFF_TO_IDX( 2196 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 2197 2198 /* 2199 * let processes that are swapped out really be 2200 * swapped out set the limit to nothing (will force a 2201 * swap-out.) 2202 */ 2203 if ((p->p_flag & P_INMEM) == 0) 2204 limit = 0; /* XXX */ 2205 vm = vmspace_acquire_ref(p); 2206 _PHOLD_LITE(p); 2207 PROC_UNLOCK(p); 2208 if (vm == NULL) { 2209 PRELE(p); 2210 continue; 2211 } 2212 sx_sunlock(&allproc_lock); 2213 2214 size = vmspace_resident_count(vm); 2215 if (size >= limit) { 2216 vm_pageout_map_deactivate_pages( 2217 &vm->vm_map, limit); 2218 size = vmspace_resident_count(vm); 2219 } 2220 #ifdef RACCT 2221 if (racct_enable) { 2222 rsize = IDX_TO_OFF(size); 2223 PROC_LOCK(p); 2224 if (p->p_state == PRS_NORMAL) 2225 racct_set(p, RACCT_RSS, rsize); 2226 ravailable = racct_get_available(p, RACCT_RSS); 2227 PROC_UNLOCK(p); 2228 if (rsize > ravailable) { 2229 /* 2230 * Don't be overly aggressive; this 2231 * might be an innocent process, 2232 * and the limit could've been exceeded 2233 * by some memory hog. Don't try 2234 * to deactivate more than 1/4th 2235 * of process' resident set size. 2236 */ 2237 if (attempts <= 8) { 2238 if (ravailable < rsize - 2239 (rsize / 4)) { 2240 ravailable = rsize - 2241 (rsize / 4); 2242 } 2243 } 2244 vm_pageout_map_deactivate_pages( 2245 &vm->vm_map, 2246 OFF_TO_IDX(ravailable)); 2247 /* Update RSS usage after paging out. */ 2248 size = vmspace_resident_count(vm); 2249 rsize = IDX_TO_OFF(size); 2250 PROC_LOCK(p); 2251 if (p->p_state == PRS_NORMAL) 2252 racct_set(p, RACCT_RSS, rsize); 2253 PROC_UNLOCK(p); 2254 if (rsize > ravailable) 2255 tryagain = 1; 2256 } 2257 } 2258 #endif 2259 vmspace_free(vm); 2260 sx_slock(&allproc_lock); 2261 PRELE(p); 2262 } 2263 sx_sunlock(&allproc_lock); 2264 if (tryagain != 0 && attempts <= 10) 2265 goto again; 2266 } 2267 } 2268 #endif /* !defined(NO_SWAPPING) */
Cache object: 27fa028620520cff773d63119c7a4e0d
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