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, 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 static int swapdev_enabled; 186 187 #if defined(NO_SWAPPING) 188 static int vm_swap_enabled = 0; 189 static int vm_swap_idle_enabled = 0; 190 #else 191 static int vm_swap_enabled = 1; 192 static int vm_swap_idle_enabled = 0; 193 #endif 194 195 static int vm_panic_on_oom = 0; 196 197 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom, 198 CTLFLAG_RWTUN, &vm_panic_on_oom, 0, 199 "panic on out of memory instead of killing the largest process"); 200 201 SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh, 202 CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0, 203 "free page threshold for waking up the pageout daemon"); 204 205 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period, 206 CTLFLAG_RW, &vm_pageout_update_period, 0, 207 "Maximum active LRU update period"); 208 209 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0, 210 "Low memory callback period"); 211 212 #if defined(NO_SWAPPING) 213 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 214 CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout"); 215 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 216 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 217 #else 218 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 219 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 220 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 221 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 222 #endif 223 224 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 225 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 226 227 static int pageout_lock_miss; 228 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 229 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 230 231 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq, 232 CTLFLAG_RW, &vm_pageout_oom_seq, 0, 233 "back-to-back calls to oom detector to start OOM"); 234 235 static int act_scan_laundry_weight = 3; 236 SYSCTL_INT(_vm, OID_AUTO, act_scan_laundry_weight, CTLFLAG_RW, 237 &act_scan_laundry_weight, 0, 238 "weight given to clean vs. dirty pages in active queue scans"); 239 240 static u_int vm_background_launder_target; 241 SYSCTL_UINT(_vm, OID_AUTO, background_launder_target, CTLFLAG_RW, 242 &vm_background_launder_target, 0, 243 "background laundering target, in pages"); 244 245 static u_int vm_background_launder_rate = 4096; 246 SYSCTL_UINT(_vm, OID_AUTO, background_launder_rate, CTLFLAG_RW, 247 &vm_background_launder_rate, 0, 248 "background laundering rate, in kilobytes per second"); 249 250 static u_int vm_background_launder_max = 20 * 1024; 251 SYSCTL_UINT(_vm, OID_AUTO, background_launder_max, CTLFLAG_RW, 252 &vm_background_launder_max, 0, "background laundering cap, in kilobytes"); 253 254 #define VM_PAGEOUT_PAGE_COUNT 16 255 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 256 257 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 258 SYSCTL_INT(_vm, OID_AUTO, max_wired, 259 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count"); 260 261 static u_int isqrt(u_int num); 262 static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *); 263 static int vm_pageout_launder(struct vm_domain *vmd, int launder, 264 bool in_shortfall); 265 static void vm_pageout_laundry_worker(void *arg); 266 #if !defined(NO_SWAPPING) 267 static void vm_pageout_map_deactivate_pages(vm_map_t, long); 268 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long); 269 static void vm_req_vmdaemon(int req); 270 #endif 271 static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *); 272 273 /* 274 * Initialize a dummy page for marking the caller's place in the specified 275 * paging queue. In principle, this function only needs to set the flag 276 * PG_MARKER. Nonetheless, it write busies and initializes the hold count 277 * to one as safety precautions. 278 */ 279 static void 280 vm_pageout_init_marker(vm_page_t marker, u_short queue) 281 { 282 283 bzero(marker, sizeof(*marker)); 284 marker->flags = PG_MARKER; 285 marker->busy_lock = VPB_SINGLE_EXCLUSIVER; 286 marker->queue = queue; 287 marker->hold_count = 1; 288 } 289 290 /* 291 * vm_pageout_fallback_object_lock: 292 * 293 * Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is 294 * known to have failed and page queue must be either PQ_ACTIVE or 295 * PQ_INACTIVE. To avoid lock order violation, unlock the page queue 296 * while locking the vm object. Use marker page to detect page queue 297 * changes and maintain notion of next page on page queue. Return 298 * TRUE if no changes were detected, FALSE otherwise. vm object is 299 * locked on return. 300 * 301 * This function depends on both the lock portion of struct vm_object 302 * and normal struct vm_page being type stable. 303 */ 304 static boolean_t 305 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next) 306 { 307 struct vm_page marker; 308 struct vm_pagequeue *pq; 309 boolean_t unchanged; 310 u_short queue; 311 vm_object_t object; 312 313 queue = m->queue; 314 vm_pageout_init_marker(&marker, queue); 315 pq = vm_page_pagequeue(m); 316 object = m->object; 317 318 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 319 vm_pagequeue_unlock(pq); 320 vm_page_unlock(m); 321 VM_OBJECT_WLOCK(object); 322 vm_page_lock(m); 323 vm_pagequeue_lock(pq); 324 325 /* 326 * The page's object might have changed, and/or the page might 327 * have moved from its original position in the queue. If the 328 * page's object has changed, then the caller should abandon 329 * processing the page because the wrong object lock was 330 * acquired. Use the marker's plinks.q, not the page's, to 331 * determine if the page has been moved. The state of the 332 * page's plinks.q can be indeterminate; whereas, the marker's 333 * plinks.q must be valid. 334 */ 335 *next = TAILQ_NEXT(&marker, plinks.q); 336 unchanged = m->object == object && 337 m == TAILQ_PREV(&marker, pglist, plinks.q); 338 KASSERT(!unchanged || m->queue == queue, 339 ("page %p queue %d %d", m, queue, m->queue)); 340 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 341 return (unchanged); 342 } 343 344 /* 345 * Lock the page while holding the page queue lock. Use marker page 346 * to detect page queue changes and maintain notion of next page on 347 * page queue. Return TRUE if no changes were detected, FALSE 348 * otherwise. The page is locked on return. The page queue lock might 349 * be dropped and reacquired. 350 * 351 * This function depends on normal struct vm_page being type stable. 352 */ 353 static boolean_t 354 vm_pageout_page_lock(vm_page_t m, vm_page_t *next) 355 { 356 struct vm_page marker; 357 struct vm_pagequeue *pq; 358 boolean_t unchanged; 359 u_short queue; 360 361 vm_page_lock_assert(m, MA_NOTOWNED); 362 if (vm_page_trylock(m)) 363 return (TRUE); 364 365 queue = m->queue; 366 vm_pageout_init_marker(&marker, queue); 367 pq = vm_page_pagequeue(m); 368 369 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q); 370 vm_pagequeue_unlock(pq); 371 vm_page_lock(m); 372 vm_pagequeue_lock(pq); 373 374 /* Page queue might have changed. */ 375 *next = TAILQ_NEXT(&marker, plinks.q); 376 unchanged = m == TAILQ_PREV(&marker, pglist, plinks.q); 377 KASSERT(!unchanged || m->queue == queue, 378 ("page %p queue %d %d", m, queue, m->queue)); 379 TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q); 380 return (unchanged); 381 } 382 383 /* 384 * Scan for pages at adjacent offsets within the given page's object that are 385 * eligible for laundering, form a cluster of these pages and the given page, 386 * and launder that cluster. 387 */ 388 static int 389 vm_pageout_cluster(vm_page_t m) 390 { 391 vm_object_t object; 392 vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps; 393 vm_pindex_t pindex; 394 int ib, is, page_base, pageout_count; 395 396 vm_page_assert_locked(m); 397 object = m->object; 398 VM_OBJECT_ASSERT_WLOCKED(object); 399 pindex = m->pindex; 400 401 /* 402 * We can't clean the page if it is busy or held. 403 */ 404 vm_page_assert_unbusied(m); 405 KASSERT(m->hold_count == 0, ("page %p is held", m)); 406 vm_page_unlock(m); 407 408 mc[vm_pageout_page_count] = pb = ps = m; 409 pageout_count = 1; 410 page_base = vm_pageout_page_count; 411 ib = 1; 412 is = 1; 413 414 /* 415 * We can cluster only if the page is not clean, busy, or held, and 416 * the page is in the laundry queue. 417 * 418 * During heavy mmap/modification loads the pageout 419 * daemon can really fragment the underlying file 420 * due to flushing pages out of order and not trying to 421 * align the clusters (which leaves sporadic out-of-order 422 * holes). To solve this problem we do the reverse scan 423 * first and attempt to align our cluster, then do a 424 * forward scan if room remains. 425 */ 426 more: 427 while (ib != 0 && pageout_count < vm_pageout_page_count) { 428 if (ib > pindex) { 429 ib = 0; 430 break; 431 } 432 if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) { 433 ib = 0; 434 break; 435 } 436 vm_page_test_dirty(p); 437 if (p->dirty == 0) { 438 ib = 0; 439 break; 440 } 441 vm_page_lock(p); 442 if (!vm_page_in_laundry(p) || 443 p->hold_count != 0) { /* may be undergoing I/O */ 444 vm_page_unlock(p); 445 ib = 0; 446 break; 447 } 448 vm_page_unlock(p); 449 mc[--page_base] = pb = p; 450 ++pageout_count; 451 ++ib; 452 453 /* 454 * We are at an alignment boundary. Stop here, and switch 455 * directions. Do not clear ib. 456 */ 457 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 458 break; 459 } 460 while (pageout_count < vm_pageout_page_count && 461 pindex + is < object->size) { 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 (!vm_page_in_laundry(p) || 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 an alignment boundary. This catches 482 * boundary conditions. 483 */ 484 if (ib != 0 && pageout_count < vm_pageout_page_count) 485 goto more; 486 487 return (vm_pageout_flush(&mc[page_base], pageout_count, 488 VM_PAGER_PUT_NOREUSE, 0, NULL, NULL)); 489 } 490 491 /* 492 * vm_pageout_flush() - launder the given pages 493 * 494 * The given pages are laundered. Note that we setup for the start of 495 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 496 * reference count all in here rather then in the parent. If we want 497 * the parent to do more sophisticated things we may have to change 498 * the ordering. 499 * 500 * Returned runlen is the count of pages between mreq and first 501 * page after mreq with status VM_PAGER_AGAIN. 502 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL 503 * for any page in runlen set. 504 */ 505 int 506 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen, 507 boolean_t *eio) 508 { 509 vm_object_t object = mc[0]->object; 510 int pageout_status[count]; 511 int numpagedout = 0; 512 int i, runlen; 513 514 VM_OBJECT_ASSERT_WLOCKED(object); 515 516 /* 517 * Initiate I/O. Bump the vm_page_t->busy counter and 518 * mark the pages read-only. 519 * 520 * We do not have to fixup the clean/dirty bits here... we can 521 * allow the pager to do it after the I/O completes. 522 * 523 * NOTE! mc[i]->dirty may be partial or fragmented due to an 524 * edge case with file fragments. 525 */ 526 for (i = 0; i < count; i++) { 527 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, 528 ("vm_pageout_flush: partially invalid page %p index %d/%d", 529 mc[i], i, count)); 530 vm_page_sbusy(mc[i]); 531 pmap_remove_write(mc[i]); 532 } 533 vm_object_pip_add(object, count); 534 535 vm_pager_put_pages(object, mc, count, flags, pageout_status); 536 537 runlen = count - mreq; 538 if (eio != NULL) 539 *eio = FALSE; 540 for (i = 0; i < count; i++) { 541 vm_page_t mt = mc[i]; 542 543 KASSERT(pageout_status[i] == VM_PAGER_PEND || 544 !pmap_page_is_write_mapped(mt), 545 ("vm_pageout_flush: page %p is not write protected", mt)); 546 switch (pageout_status[i]) { 547 case VM_PAGER_OK: 548 vm_page_lock(mt); 549 if (vm_page_in_laundry(mt)) 550 vm_page_deactivate_noreuse(mt); 551 vm_page_unlock(mt); 552 /* FALLTHROUGH */ 553 case VM_PAGER_PEND: 554 numpagedout++; 555 break; 556 case VM_PAGER_BAD: 557 /* 558 * The page is outside the object's range. We pretend 559 * that the page out worked and clean the page, so the 560 * changes will be lost if the page is reclaimed by 561 * the page daemon. 562 */ 563 vm_page_undirty(mt); 564 vm_page_lock(mt); 565 if (vm_page_in_laundry(mt)) 566 vm_page_deactivate_noreuse(mt); 567 vm_page_unlock(mt); 568 break; 569 case VM_PAGER_ERROR: 570 case VM_PAGER_FAIL: 571 /* 572 * If the page couldn't be paged out to swap because the 573 * pager wasn't able to find space, place the page in 574 * the PQ_UNSWAPPABLE holding queue. This is an 575 * optimization that prevents the page daemon from 576 * wasting CPU cycles on pages that cannot be reclaimed 577 * becase no swap device is configured. 578 * 579 * Otherwise, reactivate the page so that it doesn't 580 * clog the laundry and inactive queues. (We will try 581 * paging it out again later.) 582 */ 583 vm_page_lock(mt); 584 if (object->type == OBJT_SWAP && 585 pageout_status[i] == VM_PAGER_FAIL) { 586 vm_page_unswappable(mt); 587 numpagedout++; 588 } else 589 vm_page_activate(mt); 590 vm_page_unlock(mt); 591 if (eio != NULL && i >= mreq && i - mreq < runlen) 592 *eio = TRUE; 593 break; 594 case VM_PAGER_AGAIN: 595 if (i >= mreq && i - mreq < runlen) 596 runlen = i - mreq; 597 break; 598 } 599 600 /* 601 * If the operation is still going, leave the page busy to 602 * block all other accesses. Also, leave the paging in 603 * progress indicator set so that we don't attempt an object 604 * collapse. 605 */ 606 if (pageout_status[i] != VM_PAGER_PEND) { 607 vm_object_pip_wakeup(object); 608 vm_page_sunbusy(mt); 609 } 610 } 611 if (prunlen != NULL) 612 *prunlen = runlen; 613 return (numpagedout); 614 } 615 616 static void 617 vm_pageout_swapon(void *arg __unused, struct swdevt *sp __unused) 618 { 619 620 atomic_store_rel_int(&swapdev_enabled, 1); 621 } 622 623 static void 624 vm_pageout_swapoff(void *arg __unused, struct swdevt *sp __unused) 625 { 626 627 if (swap_pager_nswapdev() == 1) 628 atomic_store_rel_int(&swapdev_enabled, 0); 629 } 630 631 #if !defined(NO_SWAPPING) 632 /* 633 * vm_pageout_object_deactivate_pages 634 * 635 * Deactivate enough pages to satisfy the inactive target 636 * requirements. 637 * 638 * The object and map must be locked. 639 */ 640 static void 641 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 642 long desired) 643 { 644 vm_object_t backing_object, object; 645 vm_page_t p; 646 int act_delta, remove_mode; 647 648 VM_OBJECT_ASSERT_LOCKED(first_object); 649 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 650 return; 651 for (object = first_object;; object = backing_object) { 652 if (pmap_resident_count(pmap) <= desired) 653 goto unlock_return; 654 VM_OBJECT_ASSERT_LOCKED(object); 655 if ((object->flags & OBJ_UNMANAGED) != 0 || 656 object->paging_in_progress != 0) 657 goto unlock_return; 658 659 remove_mode = 0; 660 if (object->shadow_count > 1) 661 remove_mode = 1; 662 /* 663 * Scan the object's entire memory queue. 664 */ 665 TAILQ_FOREACH(p, &object->memq, listq) { 666 if (pmap_resident_count(pmap) <= desired) 667 goto unlock_return; 668 if (vm_page_busied(p)) 669 continue; 670 PCPU_INC(cnt.v_pdpages); 671 vm_page_lock(p); 672 if (p->wire_count != 0 || p->hold_count != 0 || 673 !pmap_page_exists_quick(pmap, p)) { 674 vm_page_unlock(p); 675 continue; 676 } 677 act_delta = pmap_ts_referenced(p); 678 if ((p->aflags & PGA_REFERENCED) != 0) { 679 if (act_delta == 0) 680 act_delta = 1; 681 vm_page_aflag_clear(p, PGA_REFERENCED); 682 } 683 if (!vm_page_active(p) && act_delta != 0) { 684 vm_page_activate(p); 685 p->act_count += act_delta; 686 } else if (vm_page_active(p)) { 687 if (act_delta == 0) { 688 p->act_count -= min(p->act_count, 689 ACT_DECLINE); 690 if (!remove_mode && p->act_count == 0) { 691 pmap_remove_all(p); 692 vm_page_deactivate(p); 693 } else 694 vm_page_requeue(p); 695 } else { 696 vm_page_activate(p); 697 if (p->act_count < ACT_MAX - 698 ACT_ADVANCE) 699 p->act_count += ACT_ADVANCE; 700 vm_page_requeue(p); 701 } 702 } else if (vm_page_inactive(p)) 703 pmap_remove_all(p); 704 vm_page_unlock(p); 705 } 706 if ((backing_object = object->backing_object) == NULL) 707 goto unlock_return; 708 VM_OBJECT_RLOCK(backing_object); 709 if (object != first_object) 710 VM_OBJECT_RUNLOCK(object); 711 } 712 unlock_return: 713 if (object != first_object) 714 VM_OBJECT_RUNLOCK(object); 715 } 716 717 /* 718 * deactivate some number of pages in a map, try to do it fairly, but 719 * that is really hard to do. 720 */ 721 static void 722 vm_pageout_map_deactivate_pages(map, desired) 723 vm_map_t map; 724 long desired; 725 { 726 vm_map_entry_t tmpe; 727 vm_object_t obj, bigobj; 728 int nothingwired; 729 730 if (!vm_map_trylock(map)) 731 return; 732 733 bigobj = NULL; 734 nothingwired = TRUE; 735 736 /* 737 * first, search out the biggest object, and try to free pages from 738 * that. 739 */ 740 tmpe = map->header.next; 741 while (tmpe != &map->header) { 742 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 743 obj = tmpe->object.vm_object; 744 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 745 if (obj->shadow_count <= 1 && 746 (bigobj == NULL || 747 bigobj->resident_page_count < obj->resident_page_count)) { 748 if (bigobj != NULL) 749 VM_OBJECT_RUNLOCK(bigobj); 750 bigobj = obj; 751 } else 752 VM_OBJECT_RUNLOCK(obj); 753 } 754 } 755 if (tmpe->wired_count > 0) 756 nothingwired = FALSE; 757 tmpe = tmpe->next; 758 } 759 760 if (bigobj != NULL) { 761 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired); 762 VM_OBJECT_RUNLOCK(bigobj); 763 } 764 /* 765 * Next, hunt around for other pages to deactivate. We actually 766 * do this search sort of wrong -- .text first is not the best idea. 767 */ 768 tmpe = map->header.next; 769 while (tmpe != &map->header) { 770 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 771 break; 772 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 773 obj = tmpe->object.vm_object; 774 if (obj != NULL) { 775 VM_OBJECT_RLOCK(obj); 776 vm_pageout_object_deactivate_pages(map->pmap, obj, desired); 777 VM_OBJECT_RUNLOCK(obj); 778 } 779 } 780 tmpe = tmpe->next; 781 } 782 783 /* 784 * Remove all mappings if a process is swapped out, this will free page 785 * table pages. 786 */ 787 if (desired == 0 && nothingwired) { 788 pmap_remove(vm_map_pmap(map), vm_map_min(map), 789 vm_map_max(map)); 790 } 791 792 vm_map_unlock(map); 793 } 794 #endif /* !defined(NO_SWAPPING) */ 795 796 /* 797 * Attempt to acquire all of the necessary locks to launder a page and 798 * then call through the clustering layer to PUTPAGES. Wait a short 799 * time for a vnode lock. 800 * 801 * Requires the page and object lock on entry, releases both before return. 802 * Returns 0 on success and an errno otherwise. 803 */ 804 static int 805 vm_pageout_clean(vm_page_t m, int *numpagedout) 806 { 807 struct vnode *vp; 808 struct mount *mp; 809 vm_object_t object; 810 vm_pindex_t pindex; 811 int error, lockmode; 812 813 vm_page_assert_locked(m); 814 object = m->object; 815 VM_OBJECT_ASSERT_WLOCKED(object); 816 error = 0; 817 vp = NULL; 818 mp = NULL; 819 820 /* 821 * The object is already known NOT to be dead. It 822 * is possible for the vget() to block the whole 823 * pageout daemon, but the new low-memory handling 824 * code should prevent it. 825 * 826 * We can't wait forever for the vnode lock, we might 827 * deadlock due to a vn_read() getting stuck in 828 * vm_wait while holding this vnode. We skip the 829 * vnode if we can't get it in a reasonable amount 830 * of time. 831 */ 832 if (object->type == OBJT_VNODE) { 833 vm_page_unlock(m); 834 vp = object->handle; 835 if (vp->v_type == VREG && 836 vn_start_write(vp, &mp, V_NOWAIT) != 0) { 837 mp = NULL; 838 error = EDEADLK; 839 goto unlock_all; 840 } 841 KASSERT(mp != NULL, 842 ("vp %p with NULL v_mount", vp)); 843 vm_object_reference_locked(object); 844 pindex = m->pindex; 845 VM_OBJECT_WUNLOCK(object); 846 lockmode = MNT_SHARED_WRITES(vp->v_mount) ? 847 LK_SHARED : LK_EXCLUSIVE; 848 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) { 849 vp = NULL; 850 error = EDEADLK; 851 goto unlock_mp; 852 } 853 VM_OBJECT_WLOCK(object); 854 vm_page_lock(m); 855 /* 856 * While the object and page were unlocked, the page 857 * may have been: 858 * (1) moved to a different queue, 859 * (2) reallocated to a different object, 860 * (3) reallocated to a different offset, or 861 * (4) cleaned. 862 */ 863 if (!vm_page_in_laundry(m) || m->object != object || 864 m->pindex != pindex || m->dirty == 0) { 865 vm_page_unlock(m); 866 error = ENXIO; 867 goto unlock_all; 868 } 869 870 /* 871 * The page may have been busied or held while the object 872 * and page locks were released. 873 */ 874 if (vm_page_busied(m) || m->hold_count != 0) { 875 vm_page_unlock(m); 876 error = EBUSY; 877 goto unlock_all; 878 } 879 } 880 881 /* 882 * If a page is dirty, then it is either being washed 883 * (but not yet cleaned) or it is still in the 884 * laundry. If it is still in the laundry, then we 885 * start the cleaning operation. 886 */ 887 if ((*numpagedout = vm_pageout_cluster(m)) == 0) 888 error = EIO; 889 890 unlock_all: 891 VM_OBJECT_WUNLOCK(object); 892 893 unlock_mp: 894 vm_page_lock_assert(m, MA_NOTOWNED); 895 if (mp != NULL) { 896 if (vp != NULL) 897 vput(vp); 898 vm_object_deallocate(object); 899 vn_finished_write(mp); 900 } 901 902 return (error); 903 } 904 905 /* 906 * Attempt to launder the specified number of pages. 907 * 908 * Returns the number of pages successfully laundered. 909 */ 910 static int 911 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall) 912 { 913 struct vm_pagequeue *pq; 914 vm_object_t object; 915 vm_page_t m, next; 916 int act_delta, error, maxscan, numpagedout, starting_target; 917 int vnodes_skipped; 918 bool pageout_ok, queue_locked; 919 920 starting_target = launder; 921 vnodes_skipped = 0; 922 923 /* 924 * Scan the laundry queues for pages eligible to be laundered. We stop 925 * once the target number of dirty pages have been laundered, or once 926 * we've reached the end of the queue. A single iteration of this loop 927 * may cause more than one page to be laundered because of clustering. 928 * 929 * maxscan ensures that we don't re-examine requeued pages. Any 930 * additional pages written as part of a cluster are subtracted from 931 * maxscan since they must be taken from the laundry queue. 932 * 933 * As an optimization, we avoid laundering from PQ_UNSWAPPABLE when no 934 * swap devices are configured. 935 */ 936 if (atomic_load_acq_int(&swapdev_enabled)) 937 pq = &vmd->vmd_pagequeues[PQ_UNSWAPPABLE]; 938 else 939 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY]; 940 941 scan: 942 vm_pagequeue_lock(pq); 943 maxscan = pq->pq_cnt; 944 queue_locked = true; 945 for (m = TAILQ_FIRST(&pq->pq_pl); 946 m != NULL && maxscan-- > 0 && launder > 0; 947 m = next) { 948 vm_pagequeue_assert_locked(pq); 949 KASSERT(queue_locked, ("unlocked laundry queue")); 950 KASSERT(vm_page_in_laundry(m), 951 ("page %p has an inconsistent queue", m)); 952 next = TAILQ_NEXT(m, plinks.q); 953 if ((m->flags & PG_MARKER) != 0) 954 continue; 955 KASSERT((m->flags & PG_FICTITIOUS) == 0, 956 ("PG_FICTITIOUS page %p cannot be in laundry queue", m)); 957 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 958 ("VPO_UNMANAGED page %p cannot be in laundry queue", m)); 959 if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) { 960 vm_page_unlock(m); 961 continue; 962 } 963 object = m->object; 964 if ((!VM_OBJECT_TRYWLOCK(object) && 965 (!vm_pageout_fallback_object_lock(m, &next) || 966 m->hold_count != 0)) || vm_page_busied(m)) { 967 VM_OBJECT_WUNLOCK(object); 968 vm_page_unlock(m); 969 continue; 970 } 971 972 /* 973 * Unlock the laundry queue, invalidating the 'next' pointer. 974 * Use a marker to remember our place in the laundry queue. 975 */ 976 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_laundry_marker, 977 plinks.q); 978 vm_pagequeue_unlock(pq); 979 queue_locked = false; 980 981 /* 982 * Invalid pages can be easily freed. They cannot be 983 * mapped; vm_page_free() asserts this. 984 */ 985 if (m->valid == 0) 986 goto free_page; 987 988 /* 989 * If the page has been referenced and the object is not dead, 990 * reactivate or requeue the page depending on whether the 991 * object is mapped. 992 */ 993 if ((m->aflags & PGA_REFERENCED) != 0) { 994 vm_page_aflag_clear(m, PGA_REFERENCED); 995 act_delta = 1; 996 } else 997 act_delta = 0; 998 if (object->ref_count != 0) 999 act_delta += pmap_ts_referenced(m); 1000 else { 1001 KASSERT(!pmap_page_is_mapped(m), 1002 ("page %p is mapped", m)); 1003 } 1004 if (act_delta != 0) { 1005 if (object->ref_count != 0) { 1006 PCPU_INC(cnt.v_reactivated); 1007 vm_page_activate(m); 1008 1009 /* 1010 * Increase the activation count if the page 1011 * was referenced while in the laundry queue. 1012 * This makes it less likely that the page will 1013 * be returned prematurely to the inactive 1014 * queue. 1015 */ 1016 m->act_count += act_delta + ACT_ADVANCE; 1017 1018 /* 1019 * If this was a background laundering, count 1020 * activated pages towards our target. The 1021 * purpose of background laundering is to ensure 1022 * that pages are eventually cycled through the 1023 * laundry queue, and an activation is a valid 1024 * way out. 1025 */ 1026 if (!in_shortfall) 1027 launder--; 1028 goto drop_page; 1029 } else if ((object->flags & OBJ_DEAD) == 0) 1030 goto requeue_page; 1031 } 1032 1033 /* 1034 * If the page appears to be clean at the machine-independent 1035 * layer, then remove all of its mappings from the pmap in 1036 * anticipation of freeing it. If, however, any of the page's 1037 * mappings allow write access, then the page may still be 1038 * modified until the last of those mappings are removed. 1039 */ 1040 if (object->ref_count != 0) { 1041 vm_page_test_dirty(m); 1042 if (m->dirty == 0) 1043 pmap_remove_all(m); 1044 } 1045 1046 /* 1047 * Clean pages are freed, and dirty pages are paged out unless 1048 * they belong to a dead object. Requeueing dirty pages from 1049 * dead objects is pointless, as they are being paged out and 1050 * freed by the thread that destroyed the object. 1051 */ 1052 if (m->dirty == 0) { 1053 free_page: 1054 vm_page_free(m); 1055 PCPU_INC(cnt.v_dfree); 1056 } else if ((object->flags & OBJ_DEAD) == 0) { 1057 if (object->type != OBJT_SWAP && 1058 object->type != OBJT_DEFAULT) 1059 pageout_ok = true; 1060 else if (disable_swap_pageouts) 1061 pageout_ok = false; 1062 else 1063 pageout_ok = true; 1064 if (!pageout_ok) { 1065 requeue_page: 1066 vm_pagequeue_lock(pq); 1067 queue_locked = true; 1068 vm_page_requeue_locked(m); 1069 goto drop_page; 1070 } 1071 1072 /* 1073 * Form a cluster with adjacent, dirty pages from the 1074 * same object, and page out that entire cluster. 1075 * 1076 * The adjacent, dirty pages must also be in the 1077 * laundry. However, their mappings are not checked 1078 * for new references. Consequently, a recently 1079 * referenced page may be paged out. However, that 1080 * page will not be prematurely reclaimed. After page 1081 * out, the page will be placed in the inactive queue, 1082 * where any new references will be detected and the 1083 * page reactivated. 1084 */ 1085 error = vm_pageout_clean(m, &numpagedout); 1086 if (error == 0) { 1087 launder -= numpagedout; 1088 maxscan -= numpagedout - 1; 1089 } else if (error == EDEADLK) { 1090 pageout_lock_miss++; 1091 vnodes_skipped++; 1092 } 1093 goto relock_queue; 1094 } 1095 drop_page: 1096 vm_page_unlock(m); 1097 VM_OBJECT_WUNLOCK(object); 1098 relock_queue: 1099 if (!queue_locked) { 1100 vm_pagequeue_lock(pq); 1101 queue_locked = true; 1102 } 1103 next = TAILQ_NEXT(&vmd->vmd_laundry_marker, plinks.q); 1104 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_laundry_marker, plinks.q); 1105 } 1106 vm_pagequeue_unlock(pq); 1107 1108 if (launder > 0 && pq == &vmd->vmd_pagequeues[PQ_UNSWAPPABLE]) { 1109 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY]; 1110 goto scan; 1111 } 1112 1113 /* 1114 * Wakeup the sync daemon if we skipped a vnode in a writeable object 1115 * and we didn't launder enough pages. 1116 */ 1117 if (vnodes_skipped > 0 && launder > 0) 1118 (void)speedup_syncer(); 1119 1120 return (starting_target - launder); 1121 } 1122 1123 /* 1124 * Compute the integer square root. 1125 */ 1126 static u_int 1127 isqrt(u_int num) 1128 { 1129 u_int bit, root, tmp; 1130 1131 bit = 1u << ((NBBY * sizeof(u_int)) - 2); 1132 while (bit > num) 1133 bit >>= 2; 1134 root = 0; 1135 while (bit != 0) { 1136 tmp = root + bit; 1137 root >>= 1; 1138 if (num >= tmp) { 1139 num -= tmp; 1140 root += bit; 1141 } 1142 bit >>= 2; 1143 } 1144 return (root); 1145 } 1146 1147 /* 1148 * Perform the work of the laundry thread: periodically wake up and determine 1149 * whether any pages need to be laundered. If so, determine the number of pages 1150 * that need to be laundered, and launder them. 1151 */ 1152 static void 1153 vm_pageout_laundry_worker(void *arg) 1154 { 1155 struct vm_domain *domain; 1156 struct vm_pagequeue *pq; 1157 uint64_t nclean, ndirty; 1158 u_int last_launder, wakeups; 1159 int domidx, last_target, launder, shortfall, shortfall_cycle, target; 1160 bool in_shortfall; 1161 1162 domidx = (uintptr_t)arg; 1163 domain = &vm_dom[domidx]; 1164 pq = &domain->vmd_pagequeues[PQ_LAUNDRY]; 1165 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1166 vm_pageout_init_marker(&domain->vmd_laundry_marker, PQ_LAUNDRY); 1167 1168 shortfall = 0; 1169 in_shortfall = false; 1170 shortfall_cycle = 0; 1171 target = 0; 1172 last_launder = 0; 1173 1174 /* 1175 * Calls to these handlers are serialized by the swap syscall lock. 1176 */ 1177 (void)EVENTHANDLER_REGISTER(swapon, vm_pageout_swapon, domain, 1178 EVENTHANDLER_PRI_ANY); 1179 (void)EVENTHANDLER_REGISTER(swapoff, vm_pageout_swapoff, domain, 1180 EVENTHANDLER_PRI_ANY); 1181 1182 /* 1183 * The pageout laundry worker is never done, so loop forever. 1184 */ 1185 for (;;) { 1186 KASSERT(target >= 0, ("negative target %d", target)); 1187 KASSERT(shortfall_cycle >= 0, 1188 ("negative cycle %d", shortfall_cycle)); 1189 launder = 0; 1190 wakeups = VM_METER_PCPU_CNT(v_pdwakeups); 1191 1192 /* 1193 * First determine whether we need to launder pages to meet a 1194 * shortage of free pages. 1195 */ 1196 if (shortfall > 0) { 1197 in_shortfall = true; 1198 shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE; 1199 target = shortfall; 1200 } else if (!in_shortfall) 1201 goto trybackground; 1202 else if (shortfall_cycle == 0 || vm_laundry_target() <= 0) { 1203 /* 1204 * We recently entered shortfall and began laundering 1205 * pages. If we have completed that laundering run 1206 * (and we are no longer in shortfall) or we have met 1207 * our laundry target through other activity, then we 1208 * can stop laundering pages. 1209 */ 1210 in_shortfall = false; 1211 target = 0; 1212 goto trybackground; 1213 } 1214 last_launder = wakeups; 1215 launder = target / shortfall_cycle--; 1216 goto dolaundry; 1217 1218 /* 1219 * There's no immediate need to launder any pages; see if we 1220 * meet the conditions to perform background laundering: 1221 * 1222 * 1. The ratio of dirty to clean inactive pages exceeds the 1223 * background laundering threshold and the pagedaemon has 1224 * been woken up to reclaim pages since our last 1225 * laundering, or 1226 * 2. we haven't yet reached the target of the current 1227 * background laundering run. 1228 * 1229 * The background laundering threshold is not a constant. 1230 * Instead, it is a slowly growing function of the number of 1231 * page daemon wakeups since the last laundering. Thus, as the 1232 * ratio of dirty to clean inactive pages grows, the amount of 1233 * memory pressure required to trigger laundering decreases. 1234 */ 1235 trybackground: 1236 nclean = vm_cnt.v_inactive_count + vm_cnt.v_free_count; 1237 ndirty = vm_cnt.v_laundry_count; 1238 if (target == 0 && wakeups != last_launder && 1239 ndirty * isqrt(wakeups - last_launder) >= nclean) { 1240 target = vm_background_launder_target; 1241 } 1242 1243 /* 1244 * We have a non-zero background laundering target. If we've 1245 * laundered up to our maximum without observing a page daemon 1246 * wakeup, just stop. This is a safety belt that ensures we 1247 * don't launder an excessive amount if memory pressure is low 1248 * and the ratio of dirty to clean pages is large. Otherwise, 1249 * proceed at the background laundering rate. 1250 */ 1251 if (target > 0) { 1252 if (wakeups != last_launder) { 1253 last_launder = wakeups; 1254 last_target = target; 1255 } else if (last_target - target >= 1256 vm_background_launder_max * PAGE_SIZE / 1024) { 1257 target = 0; 1258 } 1259 launder = vm_background_launder_rate * PAGE_SIZE / 1024; 1260 launder /= VM_LAUNDER_RATE; 1261 if (launder > target) 1262 launder = target; 1263 } 1264 1265 dolaundry: 1266 if (launder > 0) { 1267 /* 1268 * Because of I/O clustering, the number of laundered 1269 * pages could exceed "target" by the maximum size of 1270 * a cluster minus one. 1271 */ 1272 target -= min(vm_pageout_launder(domain, launder, 1273 in_shortfall), target); 1274 pause("laundp", hz / VM_LAUNDER_RATE); 1275 } 1276 1277 /* 1278 * If we're not currently laundering pages and the page daemon 1279 * hasn't posted a new request, sleep until the page daemon 1280 * kicks us. 1281 */ 1282 vm_pagequeue_lock(pq); 1283 if (target == 0 && vm_laundry_request == VM_LAUNDRY_IDLE) 1284 (void)mtx_sleep(&vm_laundry_request, 1285 vm_pagequeue_lockptr(pq), PVM, "launds", 0); 1286 1287 /* 1288 * If the pagedaemon has indicated that it's in shortfall, start 1289 * a shortfall laundering unless we're already in the middle of 1290 * one. This may preempt a background laundering. 1291 */ 1292 if (vm_laundry_request == VM_LAUNDRY_SHORTFALL && 1293 (!in_shortfall || shortfall_cycle == 0)) { 1294 shortfall = vm_laundry_target() + vm_pageout_deficit; 1295 target = 0; 1296 } else 1297 shortfall = 0; 1298 1299 if (target == 0) 1300 vm_laundry_request = VM_LAUNDRY_IDLE; 1301 vm_pagequeue_unlock(pq); 1302 } 1303 } 1304 1305 /* 1306 * vm_pageout_scan does the dirty work for the pageout daemon. 1307 * 1308 * pass == 0: Update active LRU/deactivate pages 1309 * pass >= 1: Free inactive pages 1310 * 1311 * Returns true if pass was zero or enough pages were freed by the inactive 1312 * queue scan to meet the target. 1313 */ 1314 static bool 1315 vm_pageout_scan(struct vm_domain *vmd, int pass) 1316 { 1317 vm_page_t m, next; 1318 struct vm_pagequeue *pq; 1319 vm_object_t object; 1320 long min_scan; 1321 int act_delta, addl_page_shortage, deficit, inactq_shortage, maxscan; 1322 int page_shortage, scan_tick, scanned, starting_page_shortage; 1323 boolean_t queue_locked; 1324 1325 /* 1326 * If we need to reclaim memory ask kernel caches to return 1327 * some. We rate limit to avoid thrashing. 1328 */ 1329 if (vmd == &vm_dom[0] && pass > 0 && 1330 (time_uptime - lowmem_uptime) >= lowmem_period) { 1331 /* 1332 * Decrease registered cache sizes. 1333 */ 1334 SDT_PROBE0(vm, , , vm__lowmem_scan); 1335 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES); 1336 /* 1337 * We do this explicitly after the caches have been 1338 * drained above. 1339 */ 1340 uma_reclaim(); 1341 lowmem_uptime = time_uptime; 1342 } 1343 1344 /* 1345 * The addl_page_shortage is the number of temporarily 1346 * stuck pages in the inactive queue. In other words, the 1347 * number of pages from the inactive count that should be 1348 * discounted in setting the target for the active queue scan. 1349 */ 1350 addl_page_shortage = 0; 1351 1352 /* 1353 * Calculate the number of pages that we want to free. This number 1354 * can be negative if many pages are freed between the wakeup call to 1355 * the page daemon and this calculation. 1356 */ 1357 if (pass > 0) { 1358 deficit = atomic_readandclear_int(&vm_pageout_deficit); 1359 page_shortage = vm_paging_target() + deficit; 1360 } else 1361 page_shortage = deficit = 0; 1362 starting_page_shortage = page_shortage; 1363 1364 /* 1365 * Start scanning the inactive queue for pages that we can free. The 1366 * scan will stop when we reach the target or we have scanned the 1367 * entire queue. (Note that m->act_count is not used to make 1368 * decisions for the inactive queue, only for the active queue.) 1369 */ 1370 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 1371 maxscan = pq->pq_cnt; 1372 vm_pagequeue_lock(pq); 1373 queue_locked = TRUE; 1374 for (m = TAILQ_FIRST(&pq->pq_pl); 1375 m != NULL && maxscan-- > 0 && page_shortage > 0; 1376 m = next) { 1377 vm_pagequeue_assert_locked(pq); 1378 KASSERT(queue_locked, ("unlocked inactive queue")); 1379 KASSERT(vm_page_inactive(m), ("Inactive queue %p", m)); 1380 1381 PCPU_INC(cnt.v_pdpages); 1382 next = TAILQ_NEXT(m, plinks.q); 1383 1384 /* 1385 * skip marker pages 1386 */ 1387 if (m->flags & PG_MARKER) 1388 continue; 1389 1390 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1391 ("Fictitious page %p cannot be in inactive queue", m)); 1392 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1393 ("Unmanaged page %p cannot be in inactive queue", m)); 1394 1395 /* 1396 * The page or object lock acquisitions fail if the 1397 * page was removed from the queue or moved to a 1398 * different position within the queue. In either 1399 * case, addl_page_shortage should not be incremented. 1400 */ 1401 if (!vm_pageout_page_lock(m, &next)) 1402 goto unlock_page; 1403 else if (m->hold_count != 0) { 1404 /* 1405 * Held pages are essentially stuck in the 1406 * queue. So, they ought to be discounted 1407 * from the inactive count. See the 1408 * calculation of inactq_shortage before the 1409 * loop over the active queue below. 1410 */ 1411 addl_page_shortage++; 1412 goto unlock_page; 1413 } 1414 object = m->object; 1415 if (!VM_OBJECT_TRYWLOCK(object)) { 1416 if (!vm_pageout_fallback_object_lock(m, &next)) 1417 goto unlock_object; 1418 else if (m->hold_count != 0) { 1419 addl_page_shortage++; 1420 goto unlock_object; 1421 } 1422 } 1423 if (vm_page_busied(m)) { 1424 /* 1425 * Don't mess with busy pages. Leave them at 1426 * the front of the queue. Most likely, they 1427 * are being paged out and will leave the 1428 * queue shortly after the scan finishes. So, 1429 * they ought to be discounted from the 1430 * inactive count. 1431 */ 1432 addl_page_shortage++; 1433 unlock_object: 1434 VM_OBJECT_WUNLOCK(object); 1435 unlock_page: 1436 vm_page_unlock(m); 1437 continue; 1438 } 1439 KASSERT(m->hold_count == 0, ("Held page %p", m)); 1440 1441 /* 1442 * Dequeue the inactive page and unlock the inactive page 1443 * queue, invalidating the 'next' pointer. Dequeueing the 1444 * page here avoids a later reacquisition (and release) of 1445 * the inactive page queue lock when vm_page_activate(), 1446 * vm_page_free(), or vm_page_launder() is called. Use a 1447 * marker to remember our place in the inactive queue. 1448 */ 1449 TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q); 1450 vm_page_dequeue_locked(m); 1451 vm_pagequeue_unlock(pq); 1452 queue_locked = FALSE; 1453 1454 /* 1455 * Invalid pages can be easily freed. They cannot be 1456 * mapped, vm_page_free() asserts this. 1457 */ 1458 if (m->valid == 0) 1459 goto free_page; 1460 1461 /* 1462 * If the page has been referenced and the object is not dead, 1463 * reactivate or requeue the page depending on whether the 1464 * object is mapped. 1465 */ 1466 if ((m->aflags & PGA_REFERENCED) != 0) { 1467 vm_page_aflag_clear(m, PGA_REFERENCED); 1468 act_delta = 1; 1469 } else 1470 act_delta = 0; 1471 if (object->ref_count != 0) { 1472 act_delta += pmap_ts_referenced(m); 1473 } else { 1474 KASSERT(!pmap_page_is_mapped(m), 1475 ("vm_pageout_scan: page %p is mapped", m)); 1476 } 1477 if (act_delta != 0) { 1478 if (object->ref_count != 0) { 1479 PCPU_INC(cnt.v_reactivated); 1480 vm_page_activate(m); 1481 1482 /* 1483 * Increase the activation count if the page 1484 * was referenced while in the inactive queue. 1485 * This makes it less likely that the page will 1486 * be returned prematurely to the inactive 1487 * queue. 1488 */ 1489 m->act_count += act_delta + ACT_ADVANCE; 1490 goto drop_page; 1491 } else if ((object->flags & OBJ_DEAD) == 0) { 1492 vm_pagequeue_lock(pq); 1493 queue_locked = TRUE; 1494 m->queue = PQ_INACTIVE; 1495 TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q); 1496 vm_pagequeue_cnt_inc(pq); 1497 goto drop_page; 1498 } 1499 } 1500 1501 /* 1502 * If the page appears to be clean at the machine-independent 1503 * layer, then remove all of its mappings from the pmap in 1504 * anticipation of freeing it. If, however, any of the page's 1505 * mappings allow write access, then the page may still be 1506 * modified until the last of those mappings are removed. 1507 */ 1508 if (object->ref_count != 0) { 1509 vm_page_test_dirty(m); 1510 if (m->dirty == 0) 1511 pmap_remove_all(m); 1512 } 1513 1514 /* 1515 * Clean pages can be freed, but dirty pages must be sent back 1516 * to the laundry, unless they belong to a dead object. 1517 * Requeueing dirty pages from dead objects is pointless, as 1518 * they are being paged out and freed by the thread that 1519 * destroyed the object. 1520 */ 1521 if (m->dirty == 0) { 1522 free_page: 1523 vm_page_free(m); 1524 PCPU_INC(cnt.v_dfree); 1525 --page_shortage; 1526 } else if ((object->flags & OBJ_DEAD) == 0) 1527 vm_page_launder(m); 1528 drop_page: 1529 vm_page_unlock(m); 1530 VM_OBJECT_WUNLOCK(object); 1531 if (!queue_locked) { 1532 vm_pagequeue_lock(pq); 1533 queue_locked = TRUE; 1534 } 1535 next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q); 1536 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q); 1537 } 1538 vm_pagequeue_unlock(pq); 1539 1540 /* 1541 * Wake up the laundry thread so that it can perform any needed 1542 * laundering. If we didn't meet our target, we're in shortfall and 1543 * need to launder more aggressively. If PQ_LAUNDRY is empty and no 1544 * swap devices are configured, the laundry thread has no work to do, so 1545 * don't bother waking it up. 1546 */ 1547 if (vm_laundry_request == VM_LAUNDRY_IDLE && 1548 starting_page_shortage > 0) { 1549 pq = &vm_dom[0].vmd_pagequeues[PQ_LAUNDRY]; 1550 vm_pagequeue_lock(pq); 1551 if (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled)) { 1552 if (page_shortage > 0) { 1553 vm_laundry_request = VM_LAUNDRY_SHORTFALL; 1554 PCPU_INC(cnt.v_pdshortfalls); 1555 } else if (vm_laundry_request != VM_LAUNDRY_SHORTFALL) 1556 vm_laundry_request = VM_LAUNDRY_BACKGROUND; 1557 wakeup(&vm_laundry_request); 1558 } 1559 vm_pagequeue_unlock(pq); 1560 } 1561 1562 #if !defined(NO_SWAPPING) 1563 /* 1564 * Wakeup the swapout daemon if we didn't free the targeted number of 1565 * pages. 1566 */ 1567 if (vm_swap_enabled && page_shortage > 0) 1568 vm_req_vmdaemon(VM_SWAP_NORMAL); 1569 #endif 1570 1571 /* 1572 * If the inactive queue scan fails repeatedly to meet its 1573 * target, kill the largest process. 1574 */ 1575 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1576 1577 /* 1578 * Compute the number of pages we want to try to move from the 1579 * active queue to either the inactive or laundry queue. 1580 * 1581 * When scanning active pages, we make clean pages count more heavily 1582 * towards the page shortage than dirty pages. This is because dirty 1583 * pages must be laundered before they can be reused and thus have less 1584 * utility when attempting to quickly alleviate a shortage. However, 1585 * this weighting also causes the scan to deactivate dirty pages more 1586 * more aggressively, improving the effectiveness of clustering and 1587 * ensuring that they can eventually be reused. 1588 */ 1589 inactq_shortage = vm_cnt.v_inactive_target - (vm_cnt.v_inactive_count + 1590 vm_cnt.v_laundry_count / act_scan_laundry_weight) + 1591 vm_paging_target() + deficit + addl_page_shortage; 1592 page_shortage *= act_scan_laundry_weight; 1593 1594 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1595 vm_pagequeue_lock(pq); 1596 maxscan = pq->pq_cnt; 1597 1598 /* 1599 * If we're just idle polling attempt to visit every 1600 * active page within 'update_period' seconds. 1601 */ 1602 scan_tick = ticks; 1603 if (vm_pageout_update_period != 0) { 1604 min_scan = pq->pq_cnt; 1605 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1606 min_scan /= hz * vm_pageout_update_period; 1607 } else 1608 min_scan = 0; 1609 if (min_scan > 0 || (inactq_shortage > 0 && maxscan > 0)) 1610 vmd->vmd_last_active_scan = scan_tick; 1611 1612 /* 1613 * Scan the active queue for pages that can be deactivated. Update 1614 * the per-page activity counter and use it to identify deactivation 1615 * candidates. Held pages may be deactivated. 1616 */ 1617 for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned < 1618 min_scan || (inactq_shortage > 0 && scanned < maxscan)); m = next, 1619 scanned++) { 1620 KASSERT(m->queue == PQ_ACTIVE, 1621 ("vm_pageout_scan: page %p isn't active", m)); 1622 next = TAILQ_NEXT(m, plinks.q); 1623 if ((m->flags & PG_MARKER) != 0) 1624 continue; 1625 KASSERT((m->flags & PG_FICTITIOUS) == 0, 1626 ("Fictitious page %p cannot be in active queue", m)); 1627 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 1628 ("Unmanaged page %p cannot be in active queue", m)); 1629 if (!vm_pageout_page_lock(m, &next)) { 1630 vm_page_unlock(m); 1631 continue; 1632 } 1633 1634 /* 1635 * The count for page daemon pages is updated after checking 1636 * the page for eligibility. 1637 */ 1638 PCPU_INC(cnt.v_pdpages); 1639 1640 /* 1641 * Check to see "how much" the page has been used. 1642 */ 1643 if ((m->aflags & PGA_REFERENCED) != 0) { 1644 vm_page_aflag_clear(m, PGA_REFERENCED); 1645 act_delta = 1; 1646 } else 1647 act_delta = 0; 1648 1649 /* 1650 * Perform an unsynchronized object ref count check. While 1651 * the page lock ensures that the page is not reallocated to 1652 * another object, in particular, one with unmanaged mappings 1653 * that cannot support pmap_ts_referenced(), two races are, 1654 * nonetheless, possible: 1655 * 1) The count was transitioning to zero, but we saw a non- 1656 * zero value. pmap_ts_referenced() will return zero 1657 * because the page is not mapped. 1658 * 2) The count was transitioning to one, but we saw zero. 1659 * This race delays the detection of a new reference. At 1660 * worst, we will deactivate and reactivate the page. 1661 */ 1662 if (m->object->ref_count != 0) 1663 act_delta += pmap_ts_referenced(m); 1664 1665 /* 1666 * Advance or decay the act_count based on recent usage. 1667 */ 1668 if (act_delta != 0) { 1669 m->act_count += ACT_ADVANCE + act_delta; 1670 if (m->act_count > ACT_MAX) 1671 m->act_count = ACT_MAX; 1672 } else 1673 m->act_count -= min(m->act_count, ACT_DECLINE); 1674 1675 /* 1676 * Move this page to the tail of the active, inactive or laundry 1677 * queue depending on usage. 1678 */ 1679 if (m->act_count == 0) { 1680 /* Dequeue to avoid later lock recursion. */ 1681 vm_page_dequeue_locked(m); 1682 1683 /* 1684 * When not short for inactive pages, let dirty pages go 1685 * through the inactive queue before moving to the 1686 * laundry queues. This gives them some extra time to 1687 * be reactivated, potentially avoiding an expensive 1688 * pageout. During a page shortage, the inactive queue 1689 * is necessarily small, so we may move dirty pages 1690 * directly to the laundry queue. 1691 */ 1692 if (inactq_shortage <= 0) 1693 vm_page_deactivate(m); 1694 else { 1695 /* 1696 * Calling vm_page_test_dirty() here would 1697 * require acquisition of the object's write 1698 * lock. However, during a page shortage, 1699 * directing dirty pages into the laundry 1700 * queue is only an optimization and not a 1701 * requirement. Therefore, we simply rely on 1702 * the opportunistic updates to the page's 1703 * dirty field by the pmap. 1704 */ 1705 if (m->dirty == 0) { 1706 vm_page_deactivate(m); 1707 inactq_shortage -= 1708 act_scan_laundry_weight; 1709 } else { 1710 vm_page_launder(m); 1711 inactq_shortage--; 1712 } 1713 } 1714 } else 1715 vm_page_requeue_locked(m); 1716 vm_page_unlock(m); 1717 } 1718 vm_pagequeue_unlock(pq); 1719 #if !defined(NO_SWAPPING) 1720 /* 1721 * Idle process swapout -- run once per second when we are reclaiming 1722 * pages. 1723 */ 1724 if (vm_swap_idle_enabled && pass > 0) { 1725 static long lsec; 1726 if (time_second != lsec) { 1727 vm_req_vmdaemon(VM_SWAP_IDLE); 1728 lsec = time_second; 1729 } 1730 } 1731 #endif 1732 return (page_shortage <= 0); 1733 } 1734 1735 static int vm_pageout_oom_vote; 1736 1737 /* 1738 * The pagedaemon threads randlomly select one to perform the 1739 * OOM. Trying to kill processes before all pagedaemons 1740 * failed to reach free target is premature. 1741 */ 1742 static void 1743 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1744 int starting_page_shortage) 1745 { 1746 int old_vote; 1747 1748 if (starting_page_shortage <= 0 || starting_page_shortage != 1749 page_shortage) 1750 vmd->vmd_oom_seq = 0; 1751 else 1752 vmd->vmd_oom_seq++; 1753 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1754 if (vmd->vmd_oom) { 1755 vmd->vmd_oom = FALSE; 1756 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1757 } 1758 return; 1759 } 1760 1761 /* 1762 * Do not follow the call sequence until OOM condition is 1763 * cleared. 1764 */ 1765 vmd->vmd_oom_seq = 0; 1766 1767 if (vmd->vmd_oom) 1768 return; 1769 1770 vmd->vmd_oom = TRUE; 1771 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1772 if (old_vote != vm_ndomains - 1) 1773 return; 1774 1775 /* 1776 * The current pagedaemon thread is the last in the quorum to 1777 * start OOM. Initiate the selection and signaling of the 1778 * victim. 1779 */ 1780 vm_pageout_oom(VM_OOM_MEM); 1781 1782 /* 1783 * After one round of OOM terror, recall our vote. On the 1784 * next pass, current pagedaemon would vote again if the low 1785 * memory condition is still there, due to vmd_oom being 1786 * false. 1787 */ 1788 vmd->vmd_oom = FALSE; 1789 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1790 } 1791 1792 /* 1793 * The OOM killer is the page daemon's action of last resort when 1794 * memory allocation requests have been stalled for a prolonged period 1795 * of time because it cannot reclaim memory. This function computes 1796 * the approximate number of physical pages that could be reclaimed if 1797 * the specified address space is destroyed. 1798 * 1799 * Private, anonymous memory owned by the address space is the 1800 * principal resource that we expect to recover after an OOM kill. 1801 * Since the physical pages mapped by the address space's COW entries 1802 * are typically shared pages, they are unlikely to be released and so 1803 * they are not counted. 1804 * 1805 * To get to the point where the page daemon runs the OOM killer, its 1806 * efforts to write-back vnode-backed pages may have stalled. This 1807 * could be caused by a memory allocation deadlock in the write path 1808 * that might be resolved by an OOM kill. Therefore, physical pages 1809 * belonging to vnode-backed objects are counted, because they might 1810 * be freed without being written out first if the address space holds 1811 * the last reference to an unlinked vnode. 1812 * 1813 * Similarly, physical pages belonging to OBJT_PHYS objects are 1814 * counted because the address space might hold the last reference to 1815 * the object. 1816 */ 1817 static long 1818 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1819 { 1820 vm_map_t map; 1821 vm_map_entry_t entry; 1822 vm_object_t obj; 1823 long res; 1824 1825 map = &vmspace->vm_map; 1826 KASSERT(!map->system_map, ("system map")); 1827 sx_assert(&map->lock, SA_LOCKED); 1828 res = 0; 1829 for (entry = map->header.next; entry != &map->header; 1830 entry = entry->next) { 1831 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1832 continue; 1833 obj = entry->object.vm_object; 1834 if (obj == NULL) 1835 continue; 1836 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1837 obj->ref_count != 1) 1838 continue; 1839 switch (obj->type) { 1840 case OBJT_DEFAULT: 1841 case OBJT_SWAP: 1842 case OBJT_PHYS: 1843 case OBJT_VNODE: 1844 res += obj->resident_page_count; 1845 break; 1846 } 1847 } 1848 return (res); 1849 } 1850 1851 void 1852 vm_pageout_oom(int shortage) 1853 { 1854 struct proc *p, *bigproc; 1855 vm_offset_t size, bigsize; 1856 struct thread *td; 1857 struct vmspace *vm; 1858 1859 /* 1860 * We keep the process bigproc locked once we find it to keep anyone 1861 * from messing with it; however, there is a possibility of 1862 * deadlock if process B is bigproc and one of its child processes 1863 * attempts to propagate a signal to B while we are waiting for A's 1864 * lock while walking this list. To avoid this, we don't block on 1865 * the process lock but just skip a process if it is already locked. 1866 */ 1867 bigproc = NULL; 1868 bigsize = 0; 1869 sx_slock(&allproc_lock); 1870 FOREACH_PROC_IN_SYSTEM(p) { 1871 int breakout; 1872 1873 PROC_LOCK(p); 1874 1875 /* 1876 * If this is a system, protected or killed process, skip it. 1877 */ 1878 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1879 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1880 p->p_pid == 1 || P_KILLED(p) || 1881 (p->p_pid < 48 && swap_pager_avail != 0)) { 1882 PROC_UNLOCK(p); 1883 continue; 1884 } 1885 /* 1886 * If the process is in a non-running type state, 1887 * don't touch it. Check all the threads individually. 1888 */ 1889 breakout = 0; 1890 FOREACH_THREAD_IN_PROC(p, td) { 1891 thread_lock(td); 1892 if (!TD_ON_RUNQ(td) && 1893 !TD_IS_RUNNING(td) && 1894 !TD_IS_SLEEPING(td) && 1895 !TD_IS_SUSPENDED(td) && 1896 !TD_IS_SWAPPED(td)) { 1897 thread_unlock(td); 1898 breakout = 1; 1899 break; 1900 } 1901 thread_unlock(td); 1902 } 1903 if (breakout) { 1904 PROC_UNLOCK(p); 1905 continue; 1906 } 1907 /* 1908 * get the process size 1909 */ 1910 vm = vmspace_acquire_ref(p); 1911 if (vm == NULL) { 1912 PROC_UNLOCK(p); 1913 continue; 1914 } 1915 _PHOLD_LITE(p); 1916 PROC_UNLOCK(p); 1917 sx_sunlock(&allproc_lock); 1918 if (!vm_map_trylock_read(&vm->vm_map)) { 1919 vmspace_free(vm); 1920 sx_slock(&allproc_lock); 1921 PRELE(p); 1922 continue; 1923 } 1924 size = vmspace_swap_count(vm); 1925 if (shortage == VM_OOM_MEM) 1926 size += vm_pageout_oom_pagecount(vm); 1927 vm_map_unlock_read(&vm->vm_map); 1928 vmspace_free(vm); 1929 sx_slock(&allproc_lock); 1930 1931 /* 1932 * If this process is bigger than the biggest one, 1933 * remember it. 1934 */ 1935 if (size > bigsize) { 1936 if (bigproc != NULL) 1937 PRELE(bigproc); 1938 bigproc = p; 1939 bigsize = size; 1940 } else { 1941 PRELE(p); 1942 } 1943 } 1944 sx_sunlock(&allproc_lock); 1945 if (bigproc != NULL) { 1946 if (vm_panic_on_oom != 0) 1947 panic("out of swap space"); 1948 PROC_LOCK(bigproc); 1949 killproc(bigproc, "out of swap space"); 1950 sched_nice(bigproc, PRIO_MIN); 1951 _PRELE(bigproc); 1952 PROC_UNLOCK(bigproc); 1953 wakeup(&vm_cnt.v_free_count); 1954 } 1955 } 1956 1957 static void 1958 vm_pageout_worker(void *arg) 1959 { 1960 struct vm_domain *domain; 1961 int domidx, pass; 1962 bool target_met; 1963 1964 domidx = (uintptr_t)arg; 1965 domain = &vm_dom[domidx]; 1966 pass = 0; 1967 target_met = true; 1968 1969 /* 1970 * XXXKIB It could be useful to bind pageout daemon threads to 1971 * the cores belonging to the domain, from which vm_page_array 1972 * is allocated. 1973 */ 1974 1975 KASSERT(domain->vmd_segs != 0, ("domain without segments")); 1976 domain->vmd_last_active_scan = ticks; 1977 vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE); 1978 vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE); 1979 TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl, 1980 &domain->vmd_inacthead, plinks.q); 1981 1982 /* 1983 * The pageout daemon worker is never done, so loop forever. 1984 */ 1985 while (TRUE) { 1986 mtx_lock(&vm_page_queue_free_mtx); 1987 1988 /* 1989 * Generally, after a level >= 1 scan, if there are enough 1990 * free pages to wakeup the waiters, then they are already 1991 * awake. A call to vm_page_free() during the scan awakened 1992 * them. However, in the following case, this wakeup serves 1993 * to bound the amount of time that a thread might wait. 1994 * Suppose a thread's call to vm_page_alloc() fails, but 1995 * before that thread calls VM_WAIT, enough pages are freed by 1996 * other threads to alleviate the free page shortage. The 1997 * thread will, nonetheless, wait until another page is freed 1998 * or this wakeup is performed. 1999 */ 2000 if (vm_pages_needed && !vm_page_count_min()) { 2001 vm_pages_needed = false; 2002 wakeup(&vm_cnt.v_free_count); 2003 } 2004 2005 /* 2006 * Do not clear vm_pageout_wanted until we reach our free page 2007 * target. Otherwise, we may be awakened over and over again, 2008 * wasting CPU time. 2009 */ 2010 if (vm_pageout_wanted && target_met) 2011 vm_pageout_wanted = false; 2012 2013 /* 2014 * Might the page daemon receive a wakeup call? 2015 */ 2016 if (vm_pageout_wanted) { 2017 /* 2018 * No. Either vm_pageout_wanted was set by another 2019 * thread during the previous scan, which must have 2020 * been a level 0 scan, or vm_pageout_wanted was 2021 * already set and the scan failed to free enough 2022 * pages. If we haven't yet performed a level >= 1 2023 * (page reclamation) scan, then increase the level 2024 * and scan again now. Otherwise, sleep a bit and 2025 * try again later. 2026 */ 2027 mtx_unlock(&vm_page_queue_free_mtx); 2028 if (pass >= 1) 2029 pause("psleep", hz / VM_INACT_SCAN_RATE); 2030 pass++; 2031 } else { 2032 /* 2033 * Yes. Sleep until pages need to be reclaimed or 2034 * have their reference stats updated. 2035 */ 2036 if (mtx_sleep(&vm_pageout_wanted, 2037 &vm_page_queue_free_mtx, PDROP | PVM, "psleep", 2038 hz) == 0) { 2039 PCPU_INC(cnt.v_pdwakeups); 2040 pass = 1; 2041 } else 2042 pass = 0; 2043 } 2044 2045 target_met = vm_pageout_scan(domain, pass); 2046 } 2047 } 2048 2049 /* 2050 * vm_pageout_init initialises basic pageout daemon settings. 2051 */ 2052 static void 2053 vm_pageout_init(void) 2054 { 2055 /* 2056 * Initialize some paging parameters. 2057 */ 2058 vm_cnt.v_interrupt_free_min = 2; 2059 if (vm_cnt.v_page_count < 2000) 2060 vm_pageout_page_count = 8; 2061 2062 /* 2063 * v_free_reserved needs to include enough for the largest 2064 * swap pager structures plus enough for any pv_entry structs 2065 * when paging. 2066 */ 2067 if (vm_cnt.v_page_count > 1024) 2068 vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200; 2069 else 2070 vm_cnt.v_free_min = 4; 2071 vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 2072 vm_cnt.v_interrupt_free_min; 2073 vm_cnt.v_free_reserved = vm_pageout_page_count + 2074 vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768); 2075 vm_cnt.v_free_severe = vm_cnt.v_free_min / 2; 2076 vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved; 2077 vm_cnt.v_free_min += vm_cnt.v_free_reserved; 2078 vm_cnt.v_free_severe += vm_cnt.v_free_reserved; 2079 vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2; 2080 if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3) 2081 vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3; 2082 2083 /* 2084 * Set the default wakeup threshold to be 10% above the minimum 2085 * page limit. This keeps the steady state out of shortfall. 2086 */ 2087 vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11; 2088 2089 /* 2090 * Set interval in seconds for active scan. We want to visit each 2091 * page at least once every ten minutes. This is to prevent worst 2092 * case paging behaviors with stale active LRU. 2093 */ 2094 if (vm_pageout_update_period == 0) 2095 vm_pageout_update_period = 600; 2096 2097 /* XXX does not really belong here */ 2098 if (vm_page_max_wired == 0) 2099 vm_page_max_wired = vm_cnt.v_free_count / 3; 2100 2101 /* 2102 * Target amount of memory to move out of the laundry queue during a 2103 * background laundering. This is proportional to the amount of system 2104 * memory. 2105 */ 2106 vm_background_launder_target = (vm_cnt.v_free_target - 2107 vm_cnt.v_free_min) / 10; 2108 } 2109 2110 /* 2111 * vm_pageout is the high level pageout daemon. 2112 */ 2113 static void 2114 vm_pageout(void) 2115 { 2116 int error; 2117 #ifdef VM_NUMA_ALLOC 2118 int i; 2119 #endif 2120 2121 swap_pager_swap_init(); 2122 error = kthread_add(vm_pageout_laundry_worker, NULL, curproc, NULL, 2123 0, 0, "laundry: dom0"); 2124 if (error != 0) 2125 panic("starting laundry for domain 0, error %d", error); 2126 #ifdef VM_NUMA_ALLOC 2127 for (i = 1; i < vm_ndomains; i++) { 2128 error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i, 2129 curproc, NULL, 0, 0, "dom%d", i); 2130 if (error != 0) { 2131 panic("starting pageout for domain %d, error %d\n", 2132 i, error); 2133 } 2134 } 2135 #endif 2136 error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL, 2137 0, 0, "uma"); 2138 if (error != 0) 2139 panic("starting uma_reclaim helper, error %d\n", error); 2140 vm_pageout_worker((void *)(uintptr_t)0); 2141 } 2142 2143 /* 2144 * Unless the free page queue lock is held by the caller, this function 2145 * should be regarded as advisory. Specifically, the caller should 2146 * not msleep() on &vm_cnt.v_free_count following this function unless 2147 * the free page queue lock is held until the msleep() is performed. 2148 */ 2149 void 2150 pagedaemon_wakeup(void) 2151 { 2152 2153 if (!vm_pageout_wanted && curthread->td_proc != pageproc) { 2154 vm_pageout_wanted = true; 2155 wakeup(&vm_pageout_wanted); 2156 } 2157 } 2158 2159 #if !defined(NO_SWAPPING) 2160 static void 2161 vm_req_vmdaemon(int req) 2162 { 2163 static int lastrun = 0; 2164 2165 mtx_lock(&vm_daemon_mtx); 2166 vm_pageout_req_swapout |= req; 2167 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 2168 wakeup(&vm_daemon_needed); 2169 lastrun = ticks; 2170 } 2171 mtx_unlock(&vm_daemon_mtx); 2172 } 2173 2174 static void 2175 vm_daemon(void) 2176 { 2177 struct rlimit rsslim; 2178 struct proc *p; 2179 struct thread *td; 2180 struct vmspace *vm; 2181 int breakout, swapout_flags, tryagain, attempts; 2182 #ifdef RACCT 2183 uint64_t rsize, ravailable; 2184 #endif 2185 2186 while (TRUE) { 2187 mtx_lock(&vm_daemon_mtx); 2188 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 2189 #ifdef RACCT 2190 racct_enable ? hz : 0 2191 #else 2192 0 2193 #endif 2194 ); 2195 swapout_flags = vm_pageout_req_swapout; 2196 vm_pageout_req_swapout = 0; 2197 mtx_unlock(&vm_daemon_mtx); 2198 if (swapout_flags) 2199 swapout_procs(swapout_flags); 2200 2201 /* 2202 * scan the processes for exceeding their rlimits or if 2203 * process is swapped out -- deactivate pages 2204 */ 2205 tryagain = 0; 2206 attempts = 0; 2207 again: 2208 attempts++; 2209 sx_slock(&allproc_lock); 2210 FOREACH_PROC_IN_SYSTEM(p) { 2211 vm_pindex_t limit, size; 2212 2213 /* 2214 * if this is a system process or if we have already 2215 * looked at this process, skip it. 2216 */ 2217 PROC_LOCK(p); 2218 if (p->p_state != PRS_NORMAL || 2219 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 2220 PROC_UNLOCK(p); 2221 continue; 2222 } 2223 /* 2224 * if the process is in a non-running type state, 2225 * don't touch it. 2226 */ 2227 breakout = 0; 2228 FOREACH_THREAD_IN_PROC(p, td) { 2229 thread_lock(td); 2230 if (!TD_ON_RUNQ(td) && 2231 !TD_IS_RUNNING(td) && 2232 !TD_IS_SLEEPING(td) && 2233 !TD_IS_SUSPENDED(td)) { 2234 thread_unlock(td); 2235 breakout = 1; 2236 break; 2237 } 2238 thread_unlock(td); 2239 } 2240 if (breakout) { 2241 PROC_UNLOCK(p); 2242 continue; 2243 } 2244 /* 2245 * get a limit 2246 */ 2247 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 2248 limit = OFF_TO_IDX( 2249 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 2250 2251 /* 2252 * let processes that are swapped out really be 2253 * swapped out set the limit to nothing (will force a 2254 * swap-out.) 2255 */ 2256 if ((p->p_flag & P_INMEM) == 0) 2257 limit = 0; /* XXX */ 2258 vm = vmspace_acquire_ref(p); 2259 _PHOLD_LITE(p); 2260 PROC_UNLOCK(p); 2261 if (vm == NULL) { 2262 PRELE(p); 2263 continue; 2264 } 2265 sx_sunlock(&allproc_lock); 2266 2267 size = vmspace_resident_count(vm); 2268 if (size >= limit) { 2269 vm_pageout_map_deactivate_pages( 2270 &vm->vm_map, limit); 2271 size = vmspace_resident_count(vm); 2272 } 2273 #ifdef RACCT 2274 if (racct_enable) { 2275 rsize = IDX_TO_OFF(size); 2276 PROC_LOCK(p); 2277 if (p->p_state == PRS_NORMAL) 2278 racct_set(p, RACCT_RSS, rsize); 2279 ravailable = racct_get_available(p, RACCT_RSS); 2280 PROC_UNLOCK(p); 2281 if (rsize > ravailable) { 2282 /* 2283 * Don't be overly aggressive; this 2284 * might be an innocent process, 2285 * and the limit could've been exceeded 2286 * by some memory hog. Don't try 2287 * to deactivate more than 1/4th 2288 * of process' resident set size. 2289 */ 2290 if (attempts <= 8) { 2291 if (ravailable < rsize - 2292 (rsize / 4)) { 2293 ravailable = rsize - 2294 (rsize / 4); 2295 } 2296 } 2297 vm_pageout_map_deactivate_pages( 2298 &vm->vm_map, 2299 OFF_TO_IDX(ravailable)); 2300 /* Update RSS usage after paging out. */ 2301 size = vmspace_resident_count(vm); 2302 rsize = IDX_TO_OFF(size); 2303 PROC_LOCK(p); 2304 if (p->p_state == PRS_NORMAL) 2305 racct_set(p, RACCT_RSS, rsize); 2306 PROC_UNLOCK(p); 2307 if (rsize > ravailable) 2308 tryagain = 1; 2309 } 2310 } 2311 #endif 2312 vmspace_free(vm); 2313 sx_slock(&allproc_lock); 2314 PRELE(p); 2315 } 2316 sx_sunlock(&allproc_lock); 2317 if (tryagain != 0 && attempts <= 10) 2318 goto again; 2319 } 2320 } 2321 #endif /* !defined(NO_SWAPPING) */ 2322