1 /*- 2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU) 3 * 4 * Copyright (c) 1991 Regents of the University of California. 5 * All rights reserved. 6 * Copyright (c) 1994 John S. Dyson 7 * All rights reserved. 8 * Copyright (c) 1994 David Greenman 9 * All rights reserved. 10 * Copyright (c) 2005 Yahoo! Technologies Norway AS 11 * All rights reserved. 12 * 13 * This code is derived from software contributed to Berkeley by 14 * The Mach Operating System project at Carnegie-Mellon University. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 3. All advertising materials mentioning features or use of this software 25 * must display the following acknowledgement: 26 * This product includes software developed by the University of 27 * California, Berkeley and its contributors. 28 * 4. Neither the name of the University nor the names of its contributors 29 * may be used to endorse or promote products derived from this software 30 * without specific prior written permission. 31 * 32 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 35 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 42 * SUCH DAMAGE. 43 * 44 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91 45 * 46 * 47 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 48 * All rights reserved. 49 * 50 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 51 * 52 * Permission to use, copy, modify and distribute this software and 53 * its documentation is hereby granted, provided that both the copyright 54 * notice and this permission notice appear in all copies of the 55 * software, derivative works or modified versions, and any portions 56 * thereof, and that both notices appear in supporting documentation. 57 * 58 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 59 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 60 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 61 * 62 * Carnegie Mellon requests users of this software to return to 63 * 64 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 65 * School of Computer Science 66 * Carnegie Mellon University 67 * Pittsburgh PA 15213-3890 68 * 69 * any improvements or extensions that they make and grant Carnegie the 70 * rights to redistribute these changes. 71 */ 72 73 /* 74 * The proverbial page-out daemon. 75 */ 76 77 #include <sys/cdefs.h> 78 __FBSDID("$FreeBSD$"); 79 80 #include "opt_vm.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/eventhandler.h> 86 #include <sys/lock.h> 87 #include <sys/mutex.h> 88 #include <sys/proc.h> 89 #include <sys/kthread.h> 90 #include <sys/ktr.h> 91 #include <sys/mount.h> 92 #include <sys/racct.h> 93 #include <sys/resourcevar.h> 94 #include <sys/sched.h> 95 #include <sys/sdt.h> 96 #include <sys/signalvar.h> 97 #include <sys/smp.h> 98 #include <sys/time.h> 99 #include <sys/vnode.h> 100 #include <sys/vmmeter.h> 101 #include <sys/rwlock.h> 102 #include <sys/sx.h> 103 #include <sys/sysctl.h> 104 105 #include <vm/vm.h> 106 #include <vm/vm_param.h> 107 #include <vm/vm_object.h> 108 #include <vm/vm_page.h> 109 #include <vm/vm_map.h> 110 #include <vm/vm_pageout.h> 111 #include <vm/vm_pager.h> 112 #include <vm/vm_phys.h> 113 #include <vm/vm_pagequeue.h> 114 #include <vm/swap_pager.h> 115 #include <vm/vm_extern.h> 116 #include <vm/uma.h> 117 118 /* 119 * System initialization 120 */ 121 122 /* the kernel process "vm_pageout"*/ 123 static void vm_pageout(void); 124 static void vm_pageout_init(void); 125 static int vm_pageout_clean(vm_page_t m, int *numpagedout); 126 static int vm_pageout_cluster(vm_page_t m); 127 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 128 int starting_page_shortage); 129 130 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init, 131 NULL); 132 133 struct proc *pageproc; 134 135 static struct kproc_desc page_kp = { 136 "pagedaemon", 137 vm_pageout, 138 &pageproc 139 }; 140 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, 141 &page_kp); 142 143 SDT_PROVIDER_DEFINE(vm); 144 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan); 145 146 /* Pagedaemon activity rates, in subdivisions of one second. */ 147 #define VM_LAUNDER_RATE 10 148 #define VM_INACT_SCAN_RATE 10 149 150 static int vm_pageout_oom_seq = 12; 151 152 static int vm_pageout_update_period; 153 static int disable_swap_pageouts; 154 static int lowmem_period = 10; 155 static int swapdev_enabled; 156 157 static int vm_panic_on_oom = 0; 158 159 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom, 160 CTLFLAG_RWTUN, &vm_panic_on_oom, 0, 161 "Panic on the given number of out-of-memory errors instead of killing the largest process"); 162 163 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period, 164 CTLFLAG_RWTUN, &vm_pageout_update_period, 0, 165 "Maximum active LRU update period"); 166 167 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RWTUN, &lowmem_period, 0, 168 "Low memory callback period"); 169 170 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 171 CTLFLAG_RWTUN, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 172 173 static int pageout_lock_miss; 174 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 175 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 176 177 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq, 178 CTLFLAG_RWTUN, &vm_pageout_oom_seq, 0, 179 "back-to-back calls to oom detector to start OOM"); 180 181 static int act_scan_laundry_weight = 3; 182 SYSCTL_INT(_vm, OID_AUTO, act_scan_laundry_weight, CTLFLAG_RWTUN, 183 &act_scan_laundry_weight, 0, 184 "weight given to clean vs. dirty pages in active queue scans"); 185 186 static u_int vm_background_launder_rate = 4096; 187 SYSCTL_UINT(_vm, OID_AUTO, background_launder_rate, CTLFLAG_RWTUN, 188 &vm_background_launder_rate, 0, 189 "background laundering rate, in kilobytes per second"); 190 191 static u_int vm_background_launder_max = 20 * 1024; 192 SYSCTL_UINT(_vm, OID_AUTO, background_launder_max, CTLFLAG_RWTUN, 193 &vm_background_launder_max, 0, "background laundering cap, in kilobytes"); 194 195 int vm_pageout_page_count = 32; 196 197 u_long vm_page_max_user_wired; 198 SYSCTL_ULONG(_vm, OID_AUTO, max_user_wired, CTLFLAG_RW, 199 &vm_page_max_user_wired, 0, 200 "system-wide limit to user-wired page count"); 201 202 static u_int isqrt(u_int num); 203 static int vm_pageout_launder(struct vm_domain *vmd, int launder, 204 bool in_shortfall); 205 static void vm_pageout_laundry_worker(void *arg); 206 207 struct scan_state { 208 struct vm_batchqueue bq; 209 struct vm_pagequeue *pq; 210 vm_page_t marker; 211 int maxscan; 212 int scanned; 213 }; 214 215 static void 216 vm_pageout_init_scan(struct scan_state *ss, struct vm_pagequeue *pq, 217 vm_page_t marker, vm_page_t after, int maxscan) 218 { 219 220 vm_pagequeue_assert_locked(pq); 221 KASSERT((marker->a.flags & PGA_ENQUEUED) == 0, 222 ("marker %p already enqueued", marker)); 223 224 if (after == NULL) 225 TAILQ_INSERT_HEAD(&pq->pq_pl, marker, plinks.q); 226 else 227 TAILQ_INSERT_AFTER(&pq->pq_pl, after, marker, plinks.q); 228 vm_page_aflag_set(marker, PGA_ENQUEUED); 229 230 vm_batchqueue_init(&ss->bq); 231 ss->pq = pq; 232 ss->marker = marker; 233 ss->maxscan = maxscan; 234 ss->scanned = 0; 235 vm_pagequeue_unlock(pq); 236 } 237 238 static void 239 vm_pageout_end_scan(struct scan_state *ss) 240 { 241 struct vm_pagequeue *pq; 242 243 pq = ss->pq; 244 vm_pagequeue_assert_locked(pq); 245 KASSERT((ss->marker->a.flags & PGA_ENQUEUED) != 0, 246 ("marker %p not enqueued", ss->marker)); 247 248 TAILQ_REMOVE(&pq->pq_pl, ss->marker, plinks.q); 249 vm_page_aflag_clear(ss->marker, PGA_ENQUEUED); 250 pq->pq_pdpages += ss->scanned; 251 } 252 253 /* 254 * Add a small number of queued pages to a batch queue for later processing 255 * without the corresponding queue lock held. The caller must have enqueued a 256 * marker page at the desired start point for the scan. Pages will be 257 * physically dequeued if the caller so requests. Otherwise, the returned 258 * batch may contain marker pages, and it is up to the caller to handle them. 259 * 260 * When processing the batch queue, vm_page_queue() must be used to 261 * determine whether the page has been logically dequeued by another thread. 262 * Once this check is performed, the page lock guarantees that the page will 263 * not be disassociated from the queue. 264 */ 265 static __always_inline void 266 vm_pageout_collect_batch(struct scan_state *ss, const bool dequeue) 267 { 268 struct vm_pagequeue *pq; 269 vm_page_t m, marker, n; 270 271 marker = ss->marker; 272 pq = ss->pq; 273 274 KASSERT((marker->a.flags & PGA_ENQUEUED) != 0, 275 ("marker %p not enqueued", ss->marker)); 276 277 vm_pagequeue_lock(pq); 278 for (m = TAILQ_NEXT(marker, plinks.q); m != NULL && 279 ss->scanned < ss->maxscan && ss->bq.bq_cnt < VM_BATCHQUEUE_SIZE; 280 m = n, ss->scanned++) { 281 n = TAILQ_NEXT(m, plinks.q); 282 if ((m->flags & PG_MARKER) == 0) { 283 KASSERT((m->a.flags & PGA_ENQUEUED) != 0, 284 ("page %p not enqueued", m)); 285 KASSERT((m->flags & PG_FICTITIOUS) == 0, 286 ("Fictitious page %p cannot be in page queue", m)); 287 KASSERT((m->oflags & VPO_UNMANAGED) == 0, 288 ("Unmanaged page %p cannot be in page queue", m)); 289 } else if (dequeue) 290 continue; 291 292 (void)vm_batchqueue_insert(&ss->bq, m); 293 if (dequeue) { 294 TAILQ_REMOVE(&pq->pq_pl, m, plinks.q); 295 vm_page_aflag_clear(m, PGA_ENQUEUED); 296 } 297 } 298 TAILQ_REMOVE(&pq->pq_pl, marker, plinks.q); 299 if (__predict_true(m != NULL)) 300 TAILQ_INSERT_BEFORE(m, marker, plinks.q); 301 else 302 TAILQ_INSERT_TAIL(&pq->pq_pl, marker, plinks.q); 303 if (dequeue) 304 vm_pagequeue_cnt_add(pq, -ss->bq.bq_cnt); 305 vm_pagequeue_unlock(pq); 306 } 307 308 /* 309 * Return the next page to be scanned, or NULL if the scan is complete. 310 */ 311 static __always_inline vm_page_t 312 vm_pageout_next(struct scan_state *ss, const bool dequeue) 313 { 314 315 if (ss->bq.bq_cnt == 0) 316 vm_pageout_collect_batch(ss, dequeue); 317 return (vm_batchqueue_pop(&ss->bq)); 318 } 319 320 /* 321 * Determine whether processing of a page should be deferred and ensure that any 322 * outstanding queue operations are processed. 323 */ 324 static __always_inline bool 325 vm_pageout_defer(vm_page_t m, const uint8_t queue, const bool enqueued) 326 { 327 vm_page_astate_t as; 328 329 as = vm_page_astate_load(m); 330 if (__predict_false(as.queue != queue || 331 ((as.flags & PGA_ENQUEUED) != 0) != enqueued)) 332 return (true); 333 if ((as.flags & PGA_QUEUE_OP_MASK) != 0) { 334 vm_page_pqbatch_submit(m, queue); 335 return (true); 336 } 337 return (false); 338 } 339 340 /* 341 * Scan for pages at adjacent offsets within the given page's object that are 342 * eligible for laundering, form a cluster of these pages and the given page, 343 * and launder that cluster. 344 */ 345 static int 346 vm_pageout_cluster(vm_page_t m) 347 { 348 vm_object_t object; 349 vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps; 350 vm_pindex_t pindex; 351 int ib, is, page_base, pageout_count; 352 353 object = m->object; 354 VM_OBJECT_ASSERT_WLOCKED(object); 355 pindex = m->pindex; 356 357 vm_page_assert_xbusied(m); 358 359 mc[vm_pageout_page_count] = pb = ps = m; 360 pageout_count = 1; 361 page_base = vm_pageout_page_count; 362 ib = 1; 363 is = 1; 364 365 /* 366 * We can cluster only if the page is not clean, busy, or held, and 367 * the page is in the laundry queue. 368 * 369 * During heavy mmap/modification loads the pageout 370 * daemon can really fragment the underlying file 371 * due to flushing pages out of order and not trying to 372 * align the clusters (which leaves sporadic out-of-order 373 * holes). To solve this problem we do the reverse scan 374 * first and attempt to align our cluster, then do a 375 * forward scan if room remains. 376 */ 377 more: 378 while (ib != 0 && pageout_count < vm_pageout_page_count) { 379 if (ib > pindex) { 380 ib = 0; 381 break; 382 } 383 if ((p = vm_page_prev(pb)) == NULL || 384 vm_page_tryxbusy(p) == 0) { 385 ib = 0; 386 break; 387 } 388 if (vm_page_wired(p)) { 389 ib = 0; 390 vm_page_xunbusy(p); 391 break; 392 } 393 vm_page_test_dirty(p); 394 if (p->dirty == 0) { 395 ib = 0; 396 vm_page_xunbusy(p); 397 break; 398 } 399 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) { 400 vm_page_xunbusy(p); 401 ib = 0; 402 break; 403 } 404 mc[--page_base] = pb = p; 405 ++pageout_count; 406 ++ib; 407 408 /* 409 * We are at an alignment boundary. Stop here, and switch 410 * directions. Do not clear ib. 411 */ 412 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 413 break; 414 } 415 while (pageout_count < vm_pageout_page_count && 416 pindex + is < object->size) { 417 if ((p = vm_page_next(ps)) == NULL || 418 vm_page_tryxbusy(p) == 0) 419 break; 420 if (vm_page_wired(p)) { 421 vm_page_xunbusy(p); 422 break; 423 } 424 vm_page_test_dirty(p); 425 if (p->dirty == 0) { 426 vm_page_xunbusy(p); 427 break; 428 } 429 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) { 430 vm_page_xunbusy(p); 431 break; 432 } 433 mc[page_base + pageout_count] = ps = p; 434 ++pageout_count; 435 ++is; 436 } 437 438 /* 439 * If we exhausted our forward scan, continue with the reverse scan 440 * when possible, even past an alignment boundary. This catches 441 * boundary conditions. 442 */ 443 if (ib != 0 && pageout_count < vm_pageout_page_count) 444 goto more; 445 446 return (vm_pageout_flush(&mc[page_base], pageout_count, 447 VM_PAGER_PUT_NOREUSE, 0, NULL, NULL)); 448 } 449 450 /* 451 * vm_pageout_flush() - launder the given pages 452 * 453 * The given pages are laundered. Note that we setup for the start of 454 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 455 * reference count all in here rather then in the parent. If we want 456 * the parent to do more sophisticated things we may have to change 457 * the ordering. 458 * 459 * Returned runlen is the count of pages between mreq and first 460 * page after mreq with status VM_PAGER_AGAIN. 461 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL 462 * for any page in runlen set. 463 */ 464 int 465 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen, 466 boolean_t *eio) 467 { 468 vm_object_t object = mc[0]->object; 469 int pageout_status[count]; 470 int numpagedout = 0; 471 int i, runlen; 472 473 VM_OBJECT_ASSERT_WLOCKED(object); 474 475 /* 476 * Initiate I/O. Mark the pages shared busy and verify that they're 477 * valid and read-only. 478 * 479 * We do not have to fixup the clean/dirty bits here... we can 480 * allow the pager to do it after the I/O completes. 481 * 482 * NOTE! mc[i]->dirty may be partial or fragmented due to an 483 * edge case with file fragments. 484 */ 485 for (i = 0; i < count; i++) { 486 KASSERT(vm_page_all_valid(mc[i]), 487 ("vm_pageout_flush: partially invalid page %p index %d/%d", 488 mc[i], i, count)); 489 KASSERT((mc[i]->a.flags & PGA_WRITEABLE) == 0, 490 ("vm_pageout_flush: writeable page %p", mc[i])); 491 vm_page_busy_downgrade(mc[i]); 492 } 493 vm_object_pip_add(object, count); 494 495 vm_pager_put_pages(object, mc, count, flags, pageout_status); 496 497 runlen = count - mreq; 498 if (eio != NULL) 499 *eio = FALSE; 500 for (i = 0; i < count; i++) { 501 vm_page_t mt = mc[i]; 502 503 KASSERT(pageout_status[i] == VM_PAGER_PEND || 504 !pmap_page_is_write_mapped(mt), 505 ("vm_pageout_flush: page %p is not write protected", mt)); 506 switch (pageout_status[i]) { 507 case VM_PAGER_OK: 508 /* 509 * The page may have moved since laundering started, in 510 * which case it should be left alone. 511 */ 512 if (vm_page_in_laundry(mt)) 513 vm_page_deactivate_noreuse(mt); 514 /* FALLTHROUGH */ 515 case VM_PAGER_PEND: 516 numpagedout++; 517 break; 518 case VM_PAGER_BAD: 519 /* 520 * The page is outside the object's range. We pretend 521 * that the page out worked and clean the page, so the 522 * changes will be lost if the page is reclaimed by 523 * the page daemon. 524 */ 525 vm_page_undirty(mt); 526 if (vm_page_in_laundry(mt)) 527 vm_page_deactivate_noreuse(mt); 528 break; 529 case VM_PAGER_ERROR: 530 case VM_PAGER_FAIL: 531 /* 532 * If the page couldn't be paged out to swap because the 533 * pager wasn't able to find space, place the page in 534 * the PQ_UNSWAPPABLE holding queue. This is an 535 * optimization that prevents the page daemon from 536 * wasting CPU cycles on pages that cannot be reclaimed 537 * becase no swap device is configured. 538 * 539 * Otherwise, reactivate the page so that it doesn't 540 * clog the laundry and inactive queues. (We will try 541 * paging it out again later.) 542 */ 543 if (object->type == OBJT_SWAP && 544 pageout_status[i] == VM_PAGER_FAIL) { 545 vm_page_unswappable(mt); 546 numpagedout++; 547 } else 548 vm_page_activate(mt); 549 if (eio != NULL && i >= mreq && i - mreq < runlen) 550 *eio = TRUE; 551 break; 552 case VM_PAGER_AGAIN: 553 if (i >= mreq && i - mreq < runlen) 554 runlen = i - mreq; 555 break; 556 } 557 558 /* 559 * If the operation is still going, leave the page busy to 560 * block all other accesses. Also, leave the paging in 561 * progress indicator set so that we don't attempt an object 562 * collapse. 563 */ 564 if (pageout_status[i] != VM_PAGER_PEND) { 565 vm_object_pip_wakeup(object); 566 vm_page_sunbusy(mt); 567 } 568 } 569 if (prunlen != NULL) 570 *prunlen = runlen; 571 return (numpagedout); 572 } 573 574 static void 575 vm_pageout_swapon(void *arg __unused, struct swdevt *sp __unused) 576 { 577 578 atomic_store_rel_int(&swapdev_enabled, 1); 579 } 580 581 static void 582 vm_pageout_swapoff(void *arg __unused, struct swdevt *sp __unused) 583 { 584 585 if (swap_pager_nswapdev() == 1) 586 atomic_store_rel_int(&swapdev_enabled, 0); 587 } 588 589 /* 590 * Attempt to acquire all of the necessary locks to launder a page and 591 * then call through the clustering layer to PUTPAGES. Wait a short 592 * time for a vnode lock. 593 * 594 * Requires the page and object lock on entry, releases both before return. 595 * Returns 0 on success and an errno otherwise. 596 */ 597 static int 598 vm_pageout_clean(vm_page_t m, int *numpagedout) 599 { 600 struct vnode *vp; 601 struct mount *mp; 602 vm_object_t object; 603 vm_pindex_t pindex; 604 int error, lockmode; 605 606 object = m->object; 607 VM_OBJECT_ASSERT_WLOCKED(object); 608 error = 0; 609 vp = NULL; 610 mp = NULL; 611 612 /* 613 * The object is already known NOT to be dead. It 614 * is possible for the vget() to block the whole 615 * pageout daemon, but the new low-memory handling 616 * code should prevent it. 617 * 618 * We can't wait forever for the vnode lock, we might 619 * deadlock due to a vn_read() getting stuck in 620 * vm_wait while holding this vnode. We skip the 621 * vnode if we can't get it in a reasonable amount 622 * of time. 623 */ 624 if (object->type == OBJT_VNODE) { 625 vm_page_xunbusy(m); 626 vp = object->handle; 627 if (vp->v_type == VREG && 628 vn_start_write(vp, &mp, V_NOWAIT) != 0) { 629 mp = NULL; 630 error = EDEADLK; 631 goto unlock_all; 632 } 633 KASSERT(mp != NULL, 634 ("vp %p with NULL v_mount", vp)); 635 vm_object_reference_locked(object); 636 pindex = m->pindex; 637 VM_OBJECT_WUNLOCK(object); 638 lockmode = MNT_SHARED_WRITES(vp->v_mount) ? 639 LK_SHARED : LK_EXCLUSIVE; 640 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) { 641 vp = NULL; 642 error = EDEADLK; 643 goto unlock_mp; 644 } 645 VM_OBJECT_WLOCK(object); 646 647 /* 648 * Ensure that the object and vnode were not disassociated 649 * while locks were dropped. 650 */ 651 if (vp->v_object != object) { 652 error = ENOENT; 653 goto unlock_all; 654 } 655 656 /* 657 * While the object was unlocked, the page may have been: 658 * (1) moved to a different queue, 659 * (2) reallocated to a different object, 660 * (3) reallocated to a different offset, or 661 * (4) cleaned. 662 */ 663 if (!vm_page_in_laundry(m) || m->object != object || 664 m->pindex != pindex || m->dirty == 0) { 665 error = ENXIO; 666 goto unlock_all; 667 } 668 669 /* 670 * The page may have been busied while the object lock was 671 * released. 672 */ 673 if (vm_page_tryxbusy(m) == 0) { 674 error = EBUSY; 675 goto unlock_all; 676 } 677 } 678 679 /* 680 * Remove all writeable mappings, failing if the page is wired. 681 */ 682 if (!vm_page_try_remove_write(m)) { 683 vm_page_xunbusy(m); 684 error = EBUSY; 685 goto unlock_all; 686 } 687 688 /* 689 * If a page is dirty, then it is either being washed 690 * (but not yet cleaned) or it is still in the 691 * laundry. If it is still in the laundry, then we 692 * start the cleaning operation. 693 */ 694 if ((*numpagedout = vm_pageout_cluster(m)) == 0) 695 error = EIO; 696 697 unlock_all: 698 VM_OBJECT_WUNLOCK(object); 699 700 unlock_mp: 701 if (mp != NULL) { 702 if (vp != NULL) 703 vput(vp); 704 vm_object_deallocate(object); 705 vn_finished_write(mp); 706 } 707 708 return (error); 709 } 710 711 /* 712 * Attempt to launder the specified number of pages. 713 * 714 * Returns the number of pages successfully laundered. 715 */ 716 static int 717 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall) 718 { 719 struct scan_state ss; 720 struct vm_pagequeue *pq; 721 vm_object_t object; 722 vm_page_t m, marker; 723 vm_page_astate_t new, old; 724 int act_delta, error, numpagedout, queue, refs, starting_target; 725 int vnodes_skipped; 726 bool pageout_ok; 727 728 object = NULL; 729 starting_target = launder; 730 vnodes_skipped = 0; 731 732 /* 733 * Scan the laundry queues for pages eligible to be laundered. We stop 734 * once the target number of dirty pages have been laundered, or once 735 * we've reached the end of the queue. A single iteration of this loop 736 * may cause more than one page to be laundered because of clustering. 737 * 738 * As an optimization, we avoid laundering from PQ_UNSWAPPABLE when no 739 * swap devices are configured. 740 */ 741 if (atomic_load_acq_int(&swapdev_enabled)) 742 queue = PQ_UNSWAPPABLE; 743 else 744 queue = PQ_LAUNDRY; 745 746 scan: 747 marker = &vmd->vmd_markers[queue]; 748 pq = &vmd->vmd_pagequeues[queue]; 749 vm_pagequeue_lock(pq); 750 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt); 751 while (launder > 0 && (m = vm_pageout_next(&ss, false)) != NULL) { 752 if (__predict_false((m->flags & PG_MARKER) != 0)) 753 continue; 754 755 /* 756 * Don't touch a page that was removed from the queue after the 757 * page queue lock was released. Otherwise, ensure that any 758 * pending queue operations, such as dequeues for wired pages, 759 * are handled. 760 */ 761 if (vm_pageout_defer(m, queue, true)) 762 continue; 763 764 /* 765 * Lock the page's object. 766 */ 767 if (object == NULL || object != m->object) { 768 if (object != NULL) 769 VM_OBJECT_WUNLOCK(object); 770 object = atomic_load_ptr(&m->object); 771 if (__predict_false(object == NULL)) 772 /* The page is being freed by another thread. */ 773 continue; 774 775 /* Depends on type-stability. */ 776 VM_OBJECT_WLOCK(object); 777 if (__predict_false(m->object != object)) { 778 VM_OBJECT_WUNLOCK(object); 779 object = NULL; 780 continue; 781 } 782 } 783 784 if (vm_page_tryxbusy(m) == 0) 785 continue; 786 787 /* 788 * Check for wirings now that we hold the object lock and have 789 * exclusively busied the page. If the page is mapped, it may 790 * still be wired by pmap lookups. The call to 791 * vm_page_try_remove_all() below atomically checks for such 792 * wirings and removes mappings. If the page is unmapped, the 793 * wire count is guaranteed not to increase after this check. 794 */ 795 if (__predict_false(vm_page_wired(m))) 796 goto skip_page; 797 798 /* 799 * Invalid pages can be easily freed. They cannot be 800 * mapped; vm_page_free() asserts this. 801 */ 802 if (vm_page_none_valid(m)) 803 goto free_page; 804 805 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0; 806 807 for (old = vm_page_astate_load(m);;) { 808 /* 809 * Check to see if the page has been removed from the 810 * queue since the first such check. Leave it alone if 811 * so, discarding any references collected by 812 * pmap_ts_referenced(). 813 */ 814 if (__predict_false(_vm_page_queue(old) == PQ_NONE)) 815 goto skip_page; 816 817 new = old; 818 act_delta = refs; 819 if ((old.flags & PGA_REFERENCED) != 0) { 820 new.flags &= ~PGA_REFERENCED; 821 act_delta++; 822 } 823 if (act_delta == 0) { 824 ; 825 } else if (object->ref_count != 0) { 826 /* 827 * Increase the activation count if the page was 828 * referenced while in the laundry queue. This 829 * makes it less likely that the page will be 830 * returned prematurely to the laundry queue. 831 */ 832 new.act_count += ACT_ADVANCE + 833 act_delta; 834 if (new.act_count > ACT_MAX) 835 new.act_count = ACT_MAX; 836 837 new.flags &= ~PGA_QUEUE_OP_MASK; 838 new.flags |= PGA_REQUEUE; 839 new.queue = PQ_ACTIVE; 840 if (!vm_page_pqstate_commit(m, &old, new)) 841 continue; 842 843 /* 844 * If this was a background laundering, count 845 * activated pages towards our target. The 846 * purpose of background laundering is to ensure 847 * that pages are eventually cycled through the 848 * laundry queue, and an activation is a valid 849 * way out. 850 */ 851 if (!in_shortfall) 852 launder--; 853 VM_CNT_INC(v_reactivated); 854 goto skip_page; 855 } else if ((object->flags & OBJ_DEAD) == 0) { 856 new.flags |= PGA_REQUEUE; 857 if (!vm_page_pqstate_commit(m, &old, new)) 858 continue; 859 goto skip_page; 860 } 861 break; 862 } 863 864 /* 865 * If the page appears to be clean at the machine-independent 866 * layer, then remove all of its mappings from the pmap in 867 * anticipation of freeing it. If, however, any of the page's 868 * mappings allow write access, then the page may still be 869 * modified until the last of those mappings are removed. 870 */ 871 if (object->ref_count != 0) { 872 vm_page_test_dirty(m); 873 if (m->dirty == 0 && !vm_page_try_remove_all(m)) 874 goto skip_page; 875 } 876 877 /* 878 * Clean pages are freed, and dirty pages are paged out unless 879 * they belong to a dead object. Requeueing dirty pages from 880 * dead objects is pointless, as they are being paged out and 881 * freed by the thread that destroyed the object. 882 */ 883 if (m->dirty == 0) { 884 free_page: 885 /* 886 * Now we are guaranteed that no other threads are 887 * manipulating the page, check for a last-second 888 * reference. 889 */ 890 if (vm_pageout_defer(m, queue, true)) 891 goto skip_page; 892 vm_page_free(m); 893 VM_CNT_INC(v_dfree); 894 } else if ((object->flags & OBJ_DEAD) == 0) { 895 if (object->type != OBJT_SWAP && 896 object->type != OBJT_DEFAULT) 897 pageout_ok = true; 898 else if (disable_swap_pageouts) 899 pageout_ok = false; 900 else 901 pageout_ok = true; 902 if (!pageout_ok) { 903 vm_page_launder(m); 904 goto skip_page; 905 } 906 907 /* 908 * Form a cluster with adjacent, dirty pages from the 909 * same object, and page out that entire cluster. 910 * 911 * The adjacent, dirty pages must also be in the 912 * laundry. However, their mappings are not checked 913 * for new references. Consequently, a recently 914 * referenced page may be paged out. However, that 915 * page will not be prematurely reclaimed. After page 916 * out, the page will be placed in the inactive queue, 917 * where any new references will be detected and the 918 * page reactivated. 919 */ 920 error = vm_pageout_clean(m, &numpagedout); 921 if (error == 0) { 922 launder -= numpagedout; 923 ss.scanned += numpagedout; 924 } else if (error == EDEADLK) { 925 pageout_lock_miss++; 926 vnodes_skipped++; 927 } 928 object = NULL; 929 } else { 930 skip_page: 931 vm_page_xunbusy(m); 932 } 933 } 934 if (object != NULL) { 935 VM_OBJECT_WUNLOCK(object); 936 object = NULL; 937 } 938 vm_pagequeue_lock(pq); 939 vm_pageout_end_scan(&ss); 940 vm_pagequeue_unlock(pq); 941 942 if (launder > 0 && queue == PQ_UNSWAPPABLE) { 943 queue = PQ_LAUNDRY; 944 goto scan; 945 } 946 947 /* 948 * Wakeup the sync daemon if we skipped a vnode in a writeable object 949 * and we didn't launder enough pages. 950 */ 951 if (vnodes_skipped > 0 && launder > 0) 952 (void)speedup_syncer(); 953 954 return (starting_target - launder); 955 } 956 957 /* 958 * Compute the integer square root. 959 */ 960 static u_int 961 isqrt(u_int num) 962 { 963 u_int bit, root, tmp; 964 965 bit = num != 0 ? (1u << ((fls(num) - 1) & ~1)) : 0; 966 root = 0; 967 while (bit != 0) { 968 tmp = root + bit; 969 root >>= 1; 970 if (num >= tmp) { 971 num -= tmp; 972 root += bit; 973 } 974 bit >>= 2; 975 } 976 return (root); 977 } 978 979 /* 980 * Perform the work of the laundry thread: periodically wake up and determine 981 * whether any pages need to be laundered. If so, determine the number of pages 982 * that need to be laundered, and launder them. 983 */ 984 static void 985 vm_pageout_laundry_worker(void *arg) 986 { 987 struct vm_domain *vmd; 988 struct vm_pagequeue *pq; 989 uint64_t nclean, ndirty, nfreed; 990 int domain, last_target, launder, shortfall, shortfall_cycle, target; 991 bool in_shortfall; 992 993 domain = (uintptr_t)arg; 994 vmd = VM_DOMAIN(domain); 995 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY]; 996 KASSERT(vmd->vmd_segs != 0, ("domain without segments")); 997 998 shortfall = 0; 999 in_shortfall = false; 1000 shortfall_cycle = 0; 1001 last_target = target = 0; 1002 nfreed = 0; 1003 1004 /* 1005 * Calls to these handlers are serialized by the swap syscall lock. 1006 */ 1007 (void)EVENTHANDLER_REGISTER(swapon, vm_pageout_swapon, vmd, 1008 EVENTHANDLER_PRI_ANY); 1009 (void)EVENTHANDLER_REGISTER(swapoff, vm_pageout_swapoff, vmd, 1010 EVENTHANDLER_PRI_ANY); 1011 1012 /* 1013 * The pageout laundry worker is never done, so loop forever. 1014 */ 1015 for (;;) { 1016 KASSERT(target >= 0, ("negative target %d", target)); 1017 KASSERT(shortfall_cycle >= 0, 1018 ("negative cycle %d", shortfall_cycle)); 1019 launder = 0; 1020 1021 /* 1022 * First determine whether we need to launder pages to meet a 1023 * shortage of free pages. 1024 */ 1025 if (shortfall > 0) { 1026 in_shortfall = true; 1027 shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE; 1028 target = shortfall; 1029 } else if (!in_shortfall) 1030 goto trybackground; 1031 else if (shortfall_cycle == 0 || vm_laundry_target(vmd) <= 0) { 1032 /* 1033 * We recently entered shortfall and began laundering 1034 * pages. If we have completed that laundering run 1035 * (and we are no longer in shortfall) or we have met 1036 * our laundry target through other activity, then we 1037 * can stop laundering pages. 1038 */ 1039 in_shortfall = false; 1040 target = 0; 1041 goto trybackground; 1042 } 1043 launder = target / shortfall_cycle--; 1044 goto dolaundry; 1045 1046 /* 1047 * There's no immediate need to launder any pages; see if we 1048 * meet the conditions to perform background laundering: 1049 * 1050 * 1. The ratio of dirty to clean inactive pages exceeds the 1051 * background laundering threshold, or 1052 * 2. we haven't yet reached the target of the current 1053 * background laundering run. 1054 * 1055 * The background laundering threshold is not a constant. 1056 * Instead, it is a slowly growing function of the number of 1057 * clean pages freed by the page daemon since the last 1058 * background laundering. Thus, as the ratio of dirty to 1059 * clean inactive pages grows, the amount of memory pressure 1060 * required to trigger laundering decreases. We ensure 1061 * that the threshold is non-zero after an inactive queue 1062 * scan, even if that scan failed to free a single clean page. 1063 */ 1064 trybackground: 1065 nclean = vmd->vmd_free_count + 1066 vmd->vmd_pagequeues[PQ_INACTIVE].pq_cnt; 1067 ndirty = vmd->vmd_pagequeues[PQ_LAUNDRY].pq_cnt; 1068 if (target == 0 && ndirty * isqrt(howmany(nfreed + 1, 1069 vmd->vmd_free_target - vmd->vmd_free_min)) >= nclean) { 1070 target = vmd->vmd_background_launder_target; 1071 } 1072 1073 /* 1074 * We have a non-zero background laundering target. If we've 1075 * laundered up to our maximum without observing a page daemon 1076 * request, just stop. This is a safety belt that ensures we 1077 * don't launder an excessive amount if memory pressure is low 1078 * and the ratio of dirty to clean pages is large. Otherwise, 1079 * proceed at the background laundering rate. 1080 */ 1081 if (target > 0) { 1082 if (nfreed > 0) { 1083 nfreed = 0; 1084 last_target = target; 1085 } else if (last_target - target >= 1086 vm_background_launder_max * PAGE_SIZE / 1024) { 1087 target = 0; 1088 } 1089 launder = vm_background_launder_rate * PAGE_SIZE / 1024; 1090 launder /= VM_LAUNDER_RATE; 1091 if (launder > target) 1092 launder = target; 1093 } 1094 1095 dolaundry: 1096 if (launder > 0) { 1097 /* 1098 * Because of I/O clustering, the number of laundered 1099 * pages could exceed "target" by the maximum size of 1100 * a cluster minus one. 1101 */ 1102 target -= min(vm_pageout_launder(vmd, launder, 1103 in_shortfall), target); 1104 pause("laundp", hz / VM_LAUNDER_RATE); 1105 } 1106 1107 /* 1108 * If we're not currently laundering pages and the page daemon 1109 * hasn't posted a new request, sleep until the page daemon 1110 * kicks us. 1111 */ 1112 vm_pagequeue_lock(pq); 1113 if (target == 0 && vmd->vmd_laundry_request == VM_LAUNDRY_IDLE) 1114 (void)mtx_sleep(&vmd->vmd_laundry_request, 1115 vm_pagequeue_lockptr(pq), PVM, "launds", 0); 1116 1117 /* 1118 * If the pagedaemon has indicated that it's in shortfall, start 1119 * a shortfall laundering unless we're already in the middle of 1120 * one. This may preempt a background laundering. 1121 */ 1122 if (vmd->vmd_laundry_request == VM_LAUNDRY_SHORTFALL && 1123 (!in_shortfall || shortfall_cycle == 0)) { 1124 shortfall = vm_laundry_target(vmd) + 1125 vmd->vmd_pageout_deficit; 1126 target = 0; 1127 } else 1128 shortfall = 0; 1129 1130 if (target == 0) 1131 vmd->vmd_laundry_request = VM_LAUNDRY_IDLE; 1132 nfreed += vmd->vmd_clean_pages_freed; 1133 vmd->vmd_clean_pages_freed = 0; 1134 vm_pagequeue_unlock(pq); 1135 } 1136 } 1137 1138 /* 1139 * Compute the number of pages we want to try to move from the 1140 * active queue to either the inactive or laundry queue. 1141 * 1142 * When scanning active pages during a shortage, we make clean pages 1143 * count more heavily towards the page shortage than dirty pages. 1144 * This is because dirty pages must be laundered before they can be 1145 * reused and thus have less utility when attempting to quickly 1146 * alleviate a free page shortage. However, this weighting also 1147 * causes the scan to deactivate dirty pages more aggressively, 1148 * improving the effectiveness of clustering. 1149 */ 1150 static int 1151 vm_pageout_active_target(struct vm_domain *vmd) 1152 { 1153 int shortage; 1154 1155 shortage = vmd->vmd_inactive_target + vm_paging_target(vmd) - 1156 (vmd->vmd_pagequeues[PQ_INACTIVE].pq_cnt + 1157 vmd->vmd_pagequeues[PQ_LAUNDRY].pq_cnt / act_scan_laundry_weight); 1158 shortage *= act_scan_laundry_weight; 1159 return (shortage); 1160 } 1161 1162 /* 1163 * Scan the active queue. If there is no shortage of inactive pages, scan a 1164 * small portion of the queue in order to maintain quasi-LRU. 1165 */ 1166 static void 1167 vm_pageout_scan_active(struct vm_domain *vmd, int page_shortage) 1168 { 1169 struct scan_state ss; 1170 vm_object_t object; 1171 vm_page_t m, marker; 1172 struct vm_pagequeue *pq; 1173 vm_page_astate_t old, new; 1174 long min_scan; 1175 int act_delta, max_scan, ps_delta, refs, scan_tick; 1176 uint8_t nqueue; 1177 1178 marker = &vmd->vmd_markers[PQ_ACTIVE]; 1179 pq = &vmd->vmd_pagequeues[PQ_ACTIVE]; 1180 vm_pagequeue_lock(pq); 1181 1182 /* 1183 * If we're just idle polling attempt to visit every 1184 * active page within 'update_period' seconds. 1185 */ 1186 scan_tick = ticks; 1187 if (vm_pageout_update_period != 0) { 1188 min_scan = pq->pq_cnt; 1189 min_scan *= scan_tick - vmd->vmd_last_active_scan; 1190 min_scan /= hz * vm_pageout_update_period; 1191 } else 1192 min_scan = 0; 1193 if (min_scan > 0 || (page_shortage > 0 && pq->pq_cnt > 0)) 1194 vmd->vmd_last_active_scan = scan_tick; 1195 1196 /* 1197 * Scan the active queue for pages that can be deactivated. Update 1198 * the per-page activity counter and use it to identify deactivation 1199 * candidates. Held pages may be deactivated. 1200 * 1201 * To avoid requeuing each page that remains in the active queue, we 1202 * implement the CLOCK algorithm. To keep the implementation of the 1203 * enqueue operation consistent for all page queues, we use two hands, 1204 * represented by marker pages. Scans begin at the first hand, which 1205 * precedes the second hand in the queue. When the two hands meet, 1206 * they are moved back to the head and tail of the queue, respectively, 1207 * and scanning resumes. 1208 */ 1209 max_scan = page_shortage > 0 ? pq->pq_cnt : min_scan; 1210 act_scan: 1211 vm_pageout_init_scan(&ss, pq, marker, &vmd->vmd_clock[0], max_scan); 1212 while ((m = vm_pageout_next(&ss, false)) != NULL) { 1213 if (__predict_false(m == &vmd->vmd_clock[1])) { 1214 vm_pagequeue_lock(pq); 1215 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[0], plinks.q); 1216 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[1], plinks.q); 1217 TAILQ_INSERT_HEAD(&pq->pq_pl, &vmd->vmd_clock[0], 1218 plinks.q); 1219 TAILQ_INSERT_TAIL(&pq->pq_pl, &vmd->vmd_clock[1], 1220 plinks.q); 1221 max_scan -= ss.scanned; 1222 vm_pageout_end_scan(&ss); 1223 goto act_scan; 1224 } 1225 if (__predict_false((m->flags & PG_MARKER) != 0)) 1226 continue; 1227 1228 /* 1229 * Don't touch a page that was removed from the queue after the 1230 * page queue lock was released. Otherwise, ensure that any 1231 * pending queue operations, such as dequeues for wired pages, 1232 * are handled. 1233 */ 1234 if (vm_pageout_defer(m, PQ_ACTIVE, true)) 1235 continue; 1236 1237 /* 1238 * A page's object pointer may be set to NULL before 1239 * the object lock is acquired. 1240 */ 1241 object = atomic_load_ptr(&m->object); 1242 if (__predict_false(object == NULL)) 1243 /* 1244 * The page has been removed from its object. 1245 */ 1246 continue; 1247 1248 /* Deferred free of swap space. */ 1249 if ((m->a.flags & PGA_SWAP_FREE) != 0 && 1250 VM_OBJECT_TRYWLOCK(object)) { 1251 if (m->object == object) 1252 vm_pager_page_unswapped(m); 1253 VM_OBJECT_WUNLOCK(object); 1254 } 1255 1256 /* 1257 * Check to see "how much" the page has been used. 1258 * 1259 * Test PGA_REFERENCED after calling pmap_ts_referenced() so 1260 * that a reference from a concurrently destroyed mapping is 1261 * observed here and now. 1262 * 1263 * Perform an unsynchronized object ref count check. While 1264 * the page lock ensures that the page is not reallocated to 1265 * another object, in particular, one with unmanaged mappings 1266 * that cannot support pmap_ts_referenced(), two races are, 1267 * nonetheless, possible: 1268 * 1) The count was transitioning to zero, but we saw a non- 1269 * zero value. pmap_ts_referenced() will return zero 1270 * because the page is not mapped. 1271 * 2) The count was transitioning to one, but we saw zero. 1272 * This race delays the detection of a new reference. At 1273 * worst, we will deactivate and reactivate the page. 1274 */ 1275 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0; 1276 1277 old = vm_page_astate_load(m); 1278 do { 1279 /* 1280 * Check to see if the page has been removed from the 1281 * queue since the first such check. Leave it alone if 1282 * so, discarding any references collected by 1283 * pmap_ts_referenced(). 1284 */ 1285 if (__predict_false(_vm_page_queue(old) == PQ_NONE)) 1286 break; 1287 1288 /* 1289 * Advance or decay the act_count based on recent usage. 1290 */ 1291 new = old; 1292 act_delta = refs; 1293 if ((old.flags & PGA_REFERENCED) != 0) { 1294 new.flags &= ~PGA_REFERENCED; 1295 act_delta++; 1296 } 1297 if (act_delta != 0) { 1298 new.act_count += ACT_ADVANCE + act_delta; 1299 if (new.act_count > ACT_MAX) 1300 new.act_count = ACT_MAX; 1301 } else { 1302 new.act_count -= min(new.act_count, 1303 ACT_DECLINE); 1304 } 1305 1306 if (new.act_count > 0) { 1307 /* 1308 * Adjust the activation count and keep the page 1309 * in the active queue. The count might be left 1310 * unchanged if it is saturated. The page may 1311 * have been moved to a different queue since we 1312 * started the scan, in which case we move it 1313 * back. 1314 */ 1315 ps_delta = 0; 1316 if (old.queue != PQ_ACTIVE) { 1317 new.flags &= ~PGA_QUEUE_OP_MASK; 1318 new.flags |= PGA_REQUEUE; 1319 new.queue = PQ_ACTIVE; 1320 } 1321 } else { 1322 /* 1323 * When not short for inactive pages, let dirty 1324 * pages go through the inactive queue before 1325 * moving to the laundry queue. This gives them 1326 * some extra time to be reactivated, 1327 * potentially avoiding an expensive pageout. 1328 * However, during a page shortage, the inactive 1329 * queue is necessarily small, and so dirty 1330 * pages would only spend a trivial amount of 1331 * time in the inactive queue. Therefore, we 1332 * might as well place them directly in the 1333 * laundry queue to reduce queuing overhead. 1334 * 1335 * Calling vm_page_test_dirty() here would 1336 * require acquisition of the object's write 1337 * lock. However, during a page shortage, 1338 * directing dirty pages into the laundry queue 1339 * is only an optimization and not a 1340 * requirement. Therefore, we simply rely on 1341 * the opportunistic updates to the page's dirty 1342 * field by the pmap. 1343 */ 1344 if (page_shortage <= 0) { 1345 nqueue = PQ_INACTIVE; 1346 ps_delta = 0; 1347 } else if (m->dirty == 0) { 1348 nqueue = PQ_INACTIVE; 1349 ps_delta = act_scan_laundry_weight; 1350 } else { 1351 nqueue = PQ_LAUNDRY; 1352 ps_delta = 1; 1353 } 1354 1355 new.flags &= ~PGA_QUEUE_OP_MASK; 1356 new.flags |= PGA_REQUEUE; 1357 new.queue = nqueue; 1358 } 1359 } while (!vm_page_pqstate_commit(m, &old, new)); 1360 1361 page_shortage -= ps_delta; 1362 } 1363 vm_pagequeue_lock(pq); 1364 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[0], plinks.q); 1365 TAILQ_INSERT_AFTER(&pq->pq_pl, marker, &vmd->vmd_clock[0], plinks.q); 1366 vm_pageout_end_scan(&ss); 1367 vm_pagequeue_unlock(pq); 1368 } 1369 1370 static int 1371 vm_pageout_reinsert_inactive_page(struct vm_pagequeue *pq, vm_page_t marker, 1372 vm_page_t m) 1373 { 1374 vm_page_astate_t as; 1375 1376 vm_pagequeue_assert_locked(pq); 1377 1378 as = vm_page_astate_load(m); 1379 if (as.queue != PQ_INACTIVE || (as.flags & PGA_ENQUEUED) != 0) 1380 return (0); 1381 vm_page_aflag_set(m, PGA_ENQUEUED); 1382 TAILQ_INSERT_BEFORE(marker, m, plinks.q); 1383 return (1); 1384 } 1385 1386 /* 1387 * Re-add stuck pages to the inactive queue. We will examine them again 1388 * during the next scan. If the queue state of a page has changed since 1389 * it was physically removed from the page queue in 1390 * vm_pageout_collect_batch(), don't do anything with that page. 1391 */ 1392 static void 1393 vm_pageout_reinsert_inactive(struct scan_state *ss, struct vm_batchqueue *bq, 1394 vm_page_t m) 1395 { 1396 struct vm_pagequeue *pq; 1397 vm_page_t marker; 1398 int delta; 1399 1400 delta = 0; 1401 marker = ss->marker; 1402 pq = ss->pq; 1403 1404 if (m != NULL) { 1405 if (vm_batchqueue_insert(bq, m)) 1406 return; 1407 vm_pagequeue_lock(pq); 1408 delta += vm_pageout_reinsert_inactive_page(pq, marker, m); 1409 } else 1410 vm_pagequeue_lock(pq); 1411 while ((m = vm_batchqueue_pop(bq)) != NULL) 1412 delta += vm_pageout_reinsert_inactive_page(pq, marker, m); 1413 vm_pagequeue_cnt_add(pq, delta); 1414 vm_pagequeue_unlock(pq); 1415 vm_batchqueue_init(bq); 1416 } 1417 1418 /* 1419 * Attempt to reclaim the requested number of pages from the inactive queue. 1420 * Returns true if the shortage was addressed. 1421 */ 1422 static int 1423 vm_pageout_scan_inactive(struct vm_domain *vmd, int shortage, 1424 int *addl_shortage) 1425 { 1426 struct scan_state ss; 1427 struct vm_batchqueue rq; 1428 vm_page_t m, marker; 1429 struct vm_pagequeue *pq; 1430 vm_object_t object; 1431 vm_page_astate_t old, new; 1432 int act_delta, addl_page_shortage, deficit, page_shortage, refs; 1433 int starting_page_shortage; 1434 1435 /* 1436 * The addl_page_shortage is an estimate of the number of temporarily 1437 * stuck pages in the inactive queue. In other words, the 1438 * number of pages from the inactive count that should be 1439 * discounted in setting the target for the active queue scan. 1440 */ 1441 addl_page_shortage = 0; 1442 1443 /* 1444 * vmd_pageout_deficit counts the number of pages requested in 1445 * allocations that failed because of a free page shortage. We assume 1446 * that the allocations will be reattempted and thus include the deficit 1447 * in our scan target. 1448 */ 1449 deficit = atomic_readandclear_int(&vmd->vmd_pageout_deficit); 1450 starting_page_shortage = page_shortage = shortage + deficit; 1451 1452 object = NULL; 1453 vm_batchqueue_init(&rq); 1454 1455 /* 1456 * Start scanning the inactive queue for pages that we can free. The 1457 * scan will stop when we reach the target or we have scanned the 1458 * entire queue. (Note that m->a.act_count is not used to make 1459 * decisions for the inactive queue, only for the active queue.) 1460 */ 1461 marker = &vmd->vmd_markers[PQ_INACTIVE]; 1462 pq = &vmd->vmd_pagequeues[PQ_INACTIVE]; 1463 vm_pagequeue_lock(pq); 1464 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt); 1465 while (page_shortage > 0 && (m = vm_pageout_next(&ss, true)) != NULL) { 1466 KASSERT((m->flags & PG_MARKER) == 0, 1467 ("marker page %p was dequeued", m)); 1468 1469 /* 1470 * Don't touch a page that was removed from the queue after the 1471 * page queue lock was released. Otherwise, ensure that any 1472 * pending queue operations, such as dequeues for wired pages, 1473 * are handled. 1474 */ 1475 if (vm_pageout_defer(m, PQ_INACTIVE, false)) 1476 continue; 1477 1478 /* 1479 * Lock the page's object. 1480 */ 1481 if (object == NULL || object != m->object) { 1482 if (object != NULL) 1483 VM_OBJECT_WUNLOCK(object); 1484 object = atomic_load_ptr(&m->object); 1485 if (__predict_false(object == NULL)) 1486 /* The page is being freed by another thread. */ 1487 continue; 1488 1489 /* Depends on type-stability. */ 1490 VM_OBJECT_WLOCK(object); 1491 if (__predict_false(m->object != object)) { 1492 VM_OBJECT_WUNLOCK(object); 1493 object = NULL; 1494 goto reinsert; 1495 } 1496 } 1497 1498 if (vm_page_tryxbusy(m) == 0) { 1499 /* 1500 * Don't mess with busy pages. Leave them at 1501 * the front of the queue. Most likely, they 1502 * are being paged out and will leave the 1503 * queue shortly after the scan finishes. So, 1504 * they ought to be discounted from the 1505 * inactive count. 1506 */ 1507 addl_page_shortage++; 1508 goto reinsert; 1509 } 1510 1511 /* Deferred free of swap space. */ 1512 if ((m->a.flags & PGA_SWAP_FREE) != 0) 1513 vm_pager_page_unswapped(m); 1514 1515 /* 1516 * Check for wirings now that we hold the object lock and have 1517 * exclusively busied the page. If the page is mapped, it may 1518 * still be wired by pmap lookups. The call to 1519 * vm_page_try_remove_all() below atomically checks for such 1520 * wirings and removes mappings. If the page is unmapped, the 1521 * wire count is guaranteed not to increase after this check. 1522 */ 1523 if (__predict_false(vm_page_wired(m))) 1524 goto skip_page; 1525 1526 /* 1527 * Invalid pages can be easily freed. They cannot be 1528 * mapped, vm_page_free() asserts this. 1529 */ 1530 if (vm_page_none_valid(m)) 1531 goto free_page; 1532 1533 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0; 1534 1535 for (old = vm_page_astate_load(m);;) { 1536 /* 1537 * Check to see if the page has been removed from the 1538 * queue since the first such check. Leave it alone if 1539 * so, discarding any references collected by 1540 * pmap_ts_referenced(). 1541 */ 1542 if (__predict_false(_vm_page_queue(old) == PQ_NONE)) 1543 goto skip_page; 1544 1545 new = old; 1546 act_delta = refs; 1547 if ((old.flags & PGA_REFERENCED) != 0) { 1548 new.flags &= ~PGA_REFERENCED; 1549 act_delta++; 1550 } 1551 if (act_delta == 0) { 1552 ; 1553 } else if (object->ref_count != 0) { 1554 /* 1555 * Increase the activation count if the 1556 * page was referenced while in the 1557 * inactive queue. This makes it less 1558 * likely that the page will be returned 1559 * prematurely to the inactive queue. 1560 */ 1561 new.act_count += ACT_ADVANCE + 1562 act_delta; 1563 if (new.act_count > ACT_MAX) 1564 new.act_count = ACT_MAX; 1565 1566 new.flags &= ~PGA_QUEUE_OP_MASK; 1567 new.flags |= PGA_REQUEUE; 1568 new.queue = PQ_ACTIVE; 1569 if (!vm_page_pqstate_commit(m, &old, new)) 1570 continue; 1571 1572 VM_CNT_INC(v_reactivated); 1573 goto skip_page; 1574 } else if ((object->flags & OBJ_DEAD) == 0) { 1575 new.queue = PQ_INACTIVE; 1576 new.flags |= PGA_REQUEUE; 1577 if (!vm_page_pqstate_commit(m, &old, new)) 1578 continue; 1579 goto skip_page; 1580 } 1581 break; 1582 } 1583 1584 /* 1585 * If the page appears to be clean at the machine-independent 1586 * layer, then remove all of its mappings from the pmap in 1587 * anticipation of freeing it. If, however, any of the page's 1588 * mappings allow write access, then the page may still be 1589 * modified until the last of those mappings are removed. 1590 */ 1591 if (object->ref_count != 0) { 1592 vm_page_test_dirty(m); 1593 if (m->dirty == 0 && !vm_page_try_remove_all(m)) 1594 goto skip_page; 1595 } 1596 1597 /* 1598 * Clean pages can be freed, but dirty pages must be sent back 1599 * to the laundry, unless they belong to a dead object. 1600 * Requeueing dirty pages from dead objects is pointless, as 1601 * they are being paged out and freed by the thread that 1602 * destroyed the object. 1603 */ 1604 if (m->dirty == 0) { 1605 free_page: 1606 /* 1607 * Now we are guaranteed that no other threads are 1608 * manipulating the page, check for a last-second 1609 * reference that would save it from doom. 1610 */ 1611 if (vm_pageout_defer(m, PQ_INACTIVE, false)) 1612 goto skip_page; 1613 1614 /* 1615 * Because we dequeued the page and have already checked 1616 * for pending dequeue and enqueue requests, we can 1617 * safely disassociate the page from the inactive queue 1618 * without holding the queue lock. 1619 */ 1620 m->a.queue = PQ_NONE; 1621 vm_page_free(m); 1622 page_shortage--; 1623 continue; 1624 } 1625 if ((object->flags & OBJ_DEAD) == 0) 1626 vm_page_launder(m); 1627 skip_page: 1628 vm_page_xunbusy(m); 1629 continue; 1630 reinsert: 1631 vm_pageout_reinsert_inactive(&ss, &rq, m); 1632 } 1633 if (object != NULL) 1634 VM_OBJECT_WUNLOCK(object); 1635 vm_pageout_reinsert_inactive(&ss, &rq, NULL); 1636 vm_pageout_reinsert_inactive(&ss, &ss.bq, NULL); 1637 vm_pagequeue_lock(pq); 1638 vm_pageout_end_scan(&ss); 1639 vm_pagequeue_unlock(pq); 1640 1641 VM_CNT_ADD(v_dfree, starting_page_shortage - page_shortage); 1642 1643 /* 1644 * Wake up the laundry thread so that it can perform any needed 1645 * laundering. If we didn't meet our target, we're in shortfall and 1646 * need to launder more aggressively. If PQ_LAUNDRY is empty and no 1647 * swap devices are configured, the laundry thread has no work to do, so 1648 * don't bother waking it up. 1649 * 1650 * The laundry thread uses the number of inactive queue scans elapsed 1651 * since the last laundering to determine whether to launder again, so 1652 * keep count. 1653 */ 1654 if (starting_page_shortage > 0) { 1655 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY]; 1656 vm_pagequeue_lock(pq); 1657 if (vmd->vmd_laundry_request == VM_LAUNDRY_IDLE && 1658 (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled))) { 1659 if (page_shortage > 0) { 1660 vmd->vmd_laundry_request = VM_LAUNDRY_SHORTFALL; 1661 VM_CNT_INC(v_pdshortfalls); 1662 } else if (vmd->vmd_laundry_request != 1663 VM_LAUNDRY_SHORTFALL) 1664 vmd->vmd_laundry_request = 1665 VM_LAUNDRY_BACKGROUND; 1666 wakeup(&vmd->vmd_laundry_request); 1667 } 1668 vmd->vmd_clean_pages_freed += 1669 starting_page_shortage - page_shortage; 1670 vm_pagequeue_unlock(pq); 1671 } 1672 1673 /* 1674 * Wakeup the swapout daemon if we didn't free the targeted number of 1675 * pages. 1676 */ 1677 if (page_shortage > 0) 1678 vm_swapout_run(); 1679 1680 /* 1681 * If the inactive queue scan fails repeatedly to meet its 1682 * target, kill the largest process. 1683 */ 1684 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage); 1685 1686 /* 1687 * Reclaim pages by swapping out idle processes, if configured to do so. 1688 */ 1689 vm_swapout_run_idle(); 1690 1691 /* 1692 * See the description of addl_page_shortage above. 1693 */ 1694 *addl_shortage = addl_page_shortage + deficit; 1695 1696 return (page_shortage <= 0); 1697 } 1698 1699 static int vm_pageout_oom_vote; 1700 1701 /* 1702 * The pagedaemon threads randlomly select one to perform the 1703 * OOM. Trying to kill processes before all pagedaemons 1704 * failed to reach free target is premature. 1705 */ 1706 static void 1707 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage, 1708 int starting_page_shortage) 1709 { 1710 int old_vote; 1711 1712 if (starting_page_shortage <= 0 || starting_page_shortage != 1713 page_shortage) 1714 vmd->vmd_oom_seq = 0; 1715 else 1716 vmd->vmd_oom_seq++; 1717 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) { 1718 if (vmd->vmd_oom) { 1719 vmd->vmd_oom = FALSE; 1720 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1721 } 1722 return; 1723 } 1724 1725 /* 1726 * Do not follow the call sequence until OOM condition is 1727 * cleared. 1728 */ 1729 vmd->vmd_oom_seq = 0; 1730 1731 if (vmd->vmd_oom) 1732 return; 1733 1734 vmd->vmd_oom = TRUE; 1735 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1); 1736 if (old_vote != vm_ndomains - 1) 1737 return; 1738 1739 /* 1740 * The current pagedaemon thread is the last in the quorum to 1741 * start OOM. Initiate the selection and signaling of the 1742 * victim. 1743 */ 1744 vm_pageout_oom(VM_OOM_MEM); 1745 1746 /* 1747 * After one round of OOM terror, recall our vote. On the 1748 * next pass, current pagedaemon would vote again if the low 1749 * memory condition is still there, due to vmd_oom being 1750 * false. 1751 */ 1752 vmd->vmd_oom = FALSE; 1753 atomic_subtract_int(&vm_pageout_oom_vote, 1); 1754 } 1755 1756 /* 1757 * The OOM killer is the page daemon's action of last resort when 1758 * memory allocation requests have been stalled for a prolonged period 1759 * of time because it cannot reclaim memory. This function computes 1760 * the approximate number of physical pages that could be reclaimed if 1761 * the specified address space is destroyed. 1762 * 1763 * Private, anonymous memory owned by the address space is the 1764 * principal resource that we expect to recover after an OOM kill. 1765 * Since the physical pages mapped by the address space's COW entries 1766 * are typically shared pages, they are unlikely to be released and so 1767 * they are not counted. 1768 * 1769 * To get to the point where the page daemon runs the OOM killer, its 1770 * efforts to write-back vnode-backed pages may have stalled. This 1771 * could be caused by a memory allocation deadlock in the write path 1772 * that might be resolved by an OOM kill. Therefore, physical pages 1773 * belonging to vnode-backed objects are counted, because they might 1774 * be freed without being written out first if the address space holds 1775 * the last reference to an unlinked vnode. 1776 * 1777 * Similarly, physical pages belonging to OBJT_PHYS objects are 1778 * counted because the address space might hold the last reference to 1779 * the object. 1780 */ 1781 static long 1782 vm_pageout_oom_pagecount(struct vmspace *vmspace) 1783 { 1784 vm_map_t map; 1785 vm_map_entry_t entry; 1786 vm_object_t obj; 1787 long res; 1788 1789 map = &vmspace->vm_map; 1790 KASSERT(!map->system_map, ("system map")); 1791 sx_assert(&map->lock, SA_LOCKED); 1792 res = 0; 1793 VM_MAP_ENTRY_FOREACH(entry, map) { 1794 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) 1795 continue; 1796 obj = entry->object.vm_object; 1797 if (obj == NULL) 1798 continue; 1799 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 && 1800 obj->ref_count != 1) 1801 continue; 1802 switch (obj->type) { 1803 case OBJT_DEFAULT: 1804 case OBJT_SWAP: 1805 case OBJT_PHYS: 1806 case OBJT_VNODE: 1807 res += obj->resident_page_count; 1808 break; 1809 } 1810 } 1811 return (res); 1812 } 1813 1814 static int vm_oom_ratelim_last; 1815 static int vm_oom_pf_secs = 10; 1816 SYSCTL_INT(_vm, OID_AUTO, oom_pf_secs, CTLFLAG_RWTUN, &vm_oom_pf_secs, 0, 1817 ""); 1818 static struct mtx vm_oom_ratelim_mtx; 1819 1820 void 1821 vm_pageout_oom(int shortage) 1822 { 1823 struct proc *p, *bigproc; 1824 vm_offset_t size, bigsize; 1825 struct thread *td; 1826 struct vmspace *vm; 1827 int now; 1828 bool breakout; 1829 1830 /* 1831 * For OOM requests originating from vm_fault(), there is a high 1832 * chance that a single large process faults simultaneously in 1833 * several threads. Also, on an active system running many 1834 * processes of middle-size, like buildworld, all of them 1835 * could fault almost simultaneously as well. 1836 * 1837 * To avoid killing too many processes, rate-limit OOMs 1838 * initiated by vm_fault() time-outs on the waits for free 1839 * pages. 1840 */ 1841 mtx_lock(&vm_oom_ratelim_mtx); 1842 now = ticks; 1843 if (shortage == VM_OOM_MEM_PF && 1844 (u_int)(now - vm_oom_ratelim_last) < hz * vm_oom_pf_secs) { 1845 mtx_unlock(&vm_oom_ratelim_mtx); 1846 return; 1847 } 1848 vm_oom_ratelim_last = now; 1849 mtx_unlock(&vm_oom_ratelim_mtx); 1850 1851 /* 1852 * We keep the process bigproc locked once we find it to keep anyone 1853 * from messing with it; however, there is a possibility of 1854 * deadlock if process B is bigproc and one of its child processes 1855 * attempts to propagate a signal to B while we are waiting for A's 1856 * lock while walking this list. To avoid this, we don't block on 1857 * the process lock but just skip a process if it is already locked. 1858 */ 1859 bigproc = NULL; 1860 bigsize = 0; 1861 sx_slock(&allproc_lock); 1862 FOREACH_PROC_IN_SYSTEM(p) { 1863 PROC_LOCK(p); 1864 1865 /* 1866 * If this is a system, protected or killed process, skip it. 1867 */ 1868 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | 1869 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || 1870 p->p_pid == 1 || P_KILLED(p) || 1871 (p->p_pid < 48 && swap_pager_avail != 0)) { 1872 PROC_UNLOCK(p); 1873 continue; 1874 } 1875 /* 1876 * If the process is in a non-running type state, 1877 * don't touch it. Check all the threads individually. 1878 */ 1879 breakout = false; 1880 FOREACH_THREAD_IN_PROC(p, td) { 1881 thread_lock(td); 1882 if (!TD_ON_RUNQ(td) && 1883 !TD_IS_RUNNING(td) && 1884 !TD_IS_SLEEPING(td) && 1885 !TD_IS_SUSPENDED(td) && 1886 !TD_IS_SWAPPED(td)) { 1887 thread_unlock(td); 1888 breakout = true; 1889 break; 1890 } 1891 thread_unlock(td); 1892 } 1893 if (breakout) { 1894 PROC_UNLOCK(p); 1895 continue; 1896 } 1897 /* 1898 * get the process size 1899 */ 1900 vm = vmspace_acquire_ref(p); 1901 if (vm == NULL) { 1902 PROC_UNLOCK(p); 1903 continue; 1904 } 1905 _PHOLD_LITE(p); 1906 PROC_UNLOCK(p); 1907 sx_sunlock(&allproc_lock); 1908 if (!vm_map_trylock_read(&vm->vm_map)) { 1909 vmspace_free(vm); 1910 sx_slock(&allproc_lock); 1911 PRELE(p); 1912 continue; 1913 } 1914 size = vmspace_swap_count(vm); 1915 if (shortage == VM_OOM_MEM || shortage == VM_OOM_MEM_PF) 1916 size += vm_pageout_oom_pagecount(vm); 1917 vm_map_unlock_read(&vm->vm_map); 1918 vmspace_free(vm); 1919 sx_slock(&allproc_lock); 1920 1921 /* 1922 * If this process is bigger than the biggest one, 1923 * remember it. 1924 */ 1925 if (size > bigsize) { 1926 if (bigproc != NULL) 1927 PRELE(bigproc); 1928 bigproc = p; 1929 bigsize = size; 1930 } else { 1931 PRELE(p); 1932 } 1933 } 1934 sx_sunlock(&allproc_lock); 1935 if (bigproc != NULL) { 1936 if (vm_panic_on_oom != 0 && --vm_panic_on_oom == 0) 1937 panic("out of swap space"); 1938 PROC_LOCK(bigproc); 1939 killproc(bigproc, "out of swap space"); 1940 sched_nice(bigproc, PRIO_MIN); 1941 _PRELE(bigproc); 1942 PROC_UNLOCK(bigproc); 1943 } 1944 } 1945 1946 /* 1947 * Signal a free page shortage to subsystems that have registered an event 1948 * handler. Reclaim memory from UMA in the event of a severe shortage. 1949 * Return true if the free page count should be re-evaluated. 1950 */ 1951 static bool 1952 vm_pageout_lowmem(void) 1953 { 1954 static int lowmem_ticks = 0; 1955 int last; 1956 bool ret; 1957 1958 ret = false; 1959 1960 last = atomic_load_int(&lowmem_ticks); 1961 while ((u_int)(ticks - last) / hz >= lowmem_period) { 1962 if (atomic_fcmpset_int(&lowmem_ticks, &last, ticks) == 0) 1963 continue; 1964 1965 /* 1966 * Decrease registered cache sizes. 1967 */ 1968 SDT_PROBE0(vm, , , vm__lowmem_scan); 1969 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES); 1970 1971 /* 1972 * We do this explicitly after the caches have been 1973 * drained above. 1974 */ 1975 uma_reclaim(UMA_RECLAIM_TRIM); 1976 ret = true; 1977 break; 1978 } 1979 1980 /* 1981 * Kick off an asynchronous reclaim of cached memory if one of the 1982 * page daemons is failing to keep up with demand. Use the "severe" 1983 * threshold instead of "min" to ensure that we do not blow away the 1984 * caches if a subset of the NUMA domains are depleted by kernel memory 1985 * allocations; the domainset iterators automatically skip domains 1986 * below the "min" threshold on the first pass. 1987 * 1988 * UMA reclaim worker has its own rate-limiting mechanism, so don't 1989 * worry about kicking it too often. 1990 */ 1991 if (vm_page_count_severe()) 1992 uma_reclaim_wakeup(); 1993 1994 return (ret); 1995 } 1996 1997 static void 1998 vm_pageout_worker(void *arg) 1999 { 2000 struct vm_domain *vmd; 2001 u_int ofree; 2002 int addl_shortage, domain, shortage; 2003 bool target_met; 2004 2005 domain = (uintptr_t)arg; 2006 vmd = VM_DOMAIN(domain); 2007 shortage = 0; 2008 target_met = true; 2009 2010 /* 2011 * XXXKIB It could be useful to bind pageout daemon threads to 2012 * the cores belonging to the domain, from which vm_page_array 2013 * is allocated. 2014 */ 2015 2016 KASSERT(vmd->vmd_segs != 0, ("domain without segments")); 2017 vmd->vmd_last_active_scan = ticks; 2018 2019 /* 2020 * The pageout daemon worker is never done, so loop forever. 2021 */ 2022 while (TRUE) { 2023 vm_domain_pageout_lock(vmd); 2024 2025 /* 2026 * We need to clear wanted before we check the limits. This 2027 * prevents races with wakers who will check wanted after they 2028 * reach the limit. 2029 */ 2030 atomic_store_int(&vmd->vmd_pageout_wanted, 0); 2031 2032 /* 2033 * Might the page daemon need to run again? 2034 */ 2035 if (vm_paging_needed(vmd, vmd->vmd_free_count)) { 2036 /* 2037 * Yes. If the scan failed to produce enough free 2038 * pages, sleep uninterruptibly for some time in the 2039 * hope that the laundry thread will clean some pages. 2040 */ 2041 vm_domain_pageout_unlock(vmd); 2042 if (!target_met) 2043 pause("pwait", hz / VM_INACT_SCAN_RATE); 2044 } else { 2045 /* 2046 * No, sleep until the next wakeup or until pages 2047 * need to have their reference stats updated. 2048 */ 2049 if (mtx_sleep(&vmd->vmd_pageout_wanted, 2050 vm_domain_pageout_lockptr(vmd), PDROP | PVM, 2051 "psleep", hz / VM_INACT_SCAN_RATE) == 0) 2052 VM_CNT_INC(v_pdwakeups); 2053 } 2054 2055 /* Prevent spurious wakeups by ensuring that wanted is set. */ 2056 atomic_store_int(&vmd->vmd_pageout_wanted, 1); 2057 2058 /* 2059 * Use the controller to calculate how many pages to free in 2060 * this interval, and scan the inactive queue. If the lowmem 2061 * handlers appear to have freed up some pages, subtract the 2062 * difference from the inactive queue scan target. 2063 */ 2064 shortage = pidctrl_daemon(&vmd->vmd_pid, vmd->vmd_free_count); 2065 if (shortage > 0) { 2066 ofree = vmd->vmd_free_count; 2067 if (vm_pageout_lowmem() && vmd->vmd_free_count > ofree) 2068 shortage -= min(vmd->vmd_free_count - ofree, 2069 (u_int)shortage); 2070 target_met = vm_pageout_scan_inactive(vmd, shortage, 2071 &addl_shortage); 2072 } else 2073 addl_shortage = 0; 2074 2075 /* 2076 * Scan the active queue. A positive value for shortage 2077 * indicates that we must aggressively deactivate pages to avoid 2078 * a shortfall. 2079 */ 2080 shortage = vm_pageout_active_target(vmd) + addl_shortage; 2081 vm_pageout_scan_active(vmd, shortage); 2082 } 2083 } 2084 2085 /* 2086 * Initialize basic pageout daemon settings. See the comment above the 2087 * definition of vm_domain for some explanation of how these thresholds are 2088 * used. 2089 */ 2090 static void 2091 vm_pageout_init_domain(int domain) 2092 { 2093 struct vm_domain *vmd; 2094 struct sysctl_oid *oid; 2095 2096 vmd = VM_DOMAIN(domain); 2097 vmd->vmd_interrupt_free_min = 2; 2098 2099 /* 2100 * v_free_reserved needs to include enough for the largest 2101 * swap pager structures plus enough for any pv_entry structs 2102 * when paging. 2103 */ 2104 vmd->vmd_pageout_free_min = 2 * MAXBSIZE / PAGE_SIZE + 2105 vmd->vmd_interrupt_free_min; 2106 vmd->vmd_free_reserved = vm_pageout_page_count + 2107 vmd->vmd_pageout_free_min + vmd->vmd_page_count / 768; 2108 vmd->vmd_free_min = vmd->vmd_page_count / 200; 2109 vmd->vmd_free_severe = vmd->vmd_free_min / 2; 2110 vmd->vmd_free_target = 4 * vmd->vmd_free_min + vmd->vmd_free_reserved; 2111 vmd->vmd_free_min += vmd->vmd_free_reserved; 2112 vmd->vmd_free_severe += vmd->vmd_free_reserved; 2113 vmd->vmd_inactive_target = (3 * vmd->vmd_free_target) / 2; 2114 if (vmd->vmd_inactive_target > vmd->vmd_free_count / 3) 2115 vmd->vmd_inactive_target = vmd->vmd_free_count / 3; 2116 2117 /* 2118 * Set the default wakeup threshold to be 10% below the paging 2119 * target. This keeps the steady state out of shortfall. 2120 */ 2121 vmd->vmd_pageout_wakeup_thresh = (vmd->vmd_free_target / 10) * 9; 2122 2123 /* 2124 * Target amount of memory to move out of the laundry queue during a 2125 * background laundering. This is proportional to the amount of system 2126 * memory. 2127 */ 2128 vmd->vmd_background_launder_target = (vmd->vmd_free_target - 2129 vmd->vmd_free_min) / 10; 2130 2131 /* Initialize the pageout daemon pid controller. */ 2132 pidctrl_init(&vmd->vmd_pid, hz / VM_INACT_SCAN_RATE, 2133 vmd->vmd_free_target, PIDCTRL_BOUND, 2134 PIDCTRL_KPD, PIDCTRL_KID, PIDCTRL_KDD); 2135 oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(vmd->vmd_oid), OID_AUTO, 2136 "pidctrl", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, ""); 2137 pidctrl_init_sysctl(&vmd->vmd_pid, SYSCTL_CHILDREN(oid)); 2138 } 2139 2140 static void 2141 vm_pageout_init(void) 2142 { 2143 u_int freecount; 2144 int i; 2145 2146 /* 2147 * Initialize some paging parameters. 2148 */ 2149 if (vm_cnt.v_page_count < 2000) 2150 vm_pageout_page_count = 8; 2151 2152 freecount = 0; 2153 for (i = 0; i < vm_ndomains; i++) { 2154 struct vm_domain *vmd; 2155 2156 vm_pageout_init_domain(i); 2157 vmd = VM_DOMAIN(i); 2158 vm_cnt.v_free_reserved += vmd->vmd_free_reserved; 2159 vm_cnt.v_free_target += vmd->vmd_free_target; 2160 vm_cnt.v_free_min += vmd->vmd_free_min; 2161 vm_cnt.v_inactive_target += vmd->vmd_inactive_target; 2162 vm_cnt.v_pageout_free_min += vmd->vmd_pageout_free_min; 2163 vm_cnt.v_interrupt_free_min += vmd->vmd_interrupt_free_min; 2164 vm_cnt.v_free_severe += vmd->vmd_free_severe; 2165 freecount += vmd->vmd_free_count; 2166 } 2167 2168 /* 2169 * Set interval in seconds for active scan. We want to visit each 2170 * page at least once every ten minutes. This is to prevent worst 2171 * case paging behaviors with stale active LRU. 2172 */ 2173 if (vm_pageout_update_period == 0) 2174 vm_pageout_update_period = 600; 2175 2176 if (vm_page_max_user_wired == 0) 2177 vm_page_max_user_wired = freecount / 3; 2178 } 2179 2180 /* 2181 * vm_pageout is the high level pageout daemon. 2182 */ 2183 static void 2184 vm_pageout(void) 2185 { 2186 struct proc *p; 2187 struct thread *td; 2188 int error, first, i; 2189 2190 p = curproc; 2191 td = curthread; 2192 2193 mtx_init(&vm_oom_ratelim_mtx, "vmoomr", NULL, MTX_DEF); 2194 swap_pager_swap_init(); 2195 for (first = -1, i = 0; i < vm_ndomains; i++) { 2196 if (VM_DOMAIN_EMPTY(i)) { 2197 if (bootverbose) 2198 printf("domain %d empty; skipping pageout\n", 2199 i); 2200 continue; 2201 } 2202 if (first == -1) 2203 first = i; 2204 else { 2205 error = kthread_add(vm_pageout_worker, 2206 (void *)(uintptr_t)i, p, NULL, 0, 0, "dom%d", i); 2207 if (error != 0) 2208 panic("starting pageout for domain %d: %d\n", 2209 i, error); 2210 } 2211 error = kthread_add(vm_pageout_laundry_worker, 2212 (void *)(uintptr_t)i, p, NULL, 0, 0, "laundry: dom%d", i); 2213 if (error != 0) 2214 panic("starting laundry for domain %d: %d", i, error); 2215 } 2216 error = kthread_add(uma_reclaim_worker, NULL, p, NULL, 0, 0, "uma"); 2217 if (error != 0) 2218 panic("starting uma_reclaim helper, error %d\n", error); 2219 2220 snprintf(td->td_name, sizeof(td->td_name), "dom%d", first); 2221 vm_pageout_worker((void *)(uintptr_t)first); 2222 } 2223 2224 /* 2225 * Perform an advisory wakeup of the page daemon. 2226 */ 2227 void 2228 pagedaemon_wakeup(int domain) 2229 { 2230 struct vm_domain *vmd; 2231 2232 vmd = VM_DOMAIN(domain); 2233 vm_domain_pageout_assert_unlocked(vmd); 2234 if (curproc == pageproc) 2235 return; 2236 2237 if (atomic_fetchadd_int(&vmd->vmd_pageout_wanted, 1) == 0) { 2238 vm_domain_pageout_lock(vmd); 2239 atomic_store_int(&vmd->vmd_pageout_wanted, 1); 2240 wakeup(&vmd->vmd_pageout_wanted); 2241 vm_domain_pageout_unlock(vmd); 2242 } 2243 } 2244