1 /* 2 * (MPSAFE) 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 * 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 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91 39 * 40 * 41 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 42 * All rights reserved. 43 * 44 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 45 * 46 * Permission to use, copy, modify and distribute this software and 47 * its documentation is hereby granted, provided that both the copyright 48 * notice and this permission notice appear in all copies of the 49 * software, derivative works or modified versions, and any portions 50 * thereof, and that both notices appear in supporting documentation. 51 * 52 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 53 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 54 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 55 * 56 * Carnegie Mellon requests users of this software to return to 57 * 58 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 59 * School of Computer Science 60 * Carnegie Mellon University 61 * Pittsburgh PA 15213-3890 62 * 63 * any improvements or extensions that they make and grant Carnegie the 64 * rights to redistribute these changes. 65 * 66 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $ 67 */ 68 69 /* 70 * The proverbial page-out daemon. 71 */ 72 73 #include "opt_vm.h" 74 #include <sys/param.h> 75 #include <sys/systm.h> 76 #include <sys/kernel.h> 77 #include <sys/proc.h> 78 #include <sys/kthread.h> 79 #include <sys/resourcevar.h> 80 #include <sys/signalvar.h> 81 #include <sys/vnode.h> 82 #include <sys/vmmeter.h> 83 #include <sys/sysctl.h> 84 85 #include <vm/vm.h> 86 #include <vm/vm_param.h> 87 #include <sys/lock.h> 88 #include <vm/vm_object.h> 89 #include <vm/vm_page.h> 90 #include <vm/vm_map.h> 91 #include <vm/vm_pageout.h> 92 #include <vm/vm_pager.h> 93 #include <vm/swap_pager.h> 94 #include <vm/vm_extern.h> 95 96 #include <sys/thread2.h> 97 #include <vm/vm_page2.h> 98 99 /* 100 * System initialization 101 */ 102 103 /* the kernel process "vm_pageout"*/ 104 static int vm_pageout_clean (vm_page_t); 105 static int vm_pageout_scan (int pass); 106 static int vm_pageout_free_page_calc (vm_size_t count); 107 struct thread *pagethread; 108 109 #if !defined(NO_SWAPPING) 110 /* the kernel process "vm_daemon"*/ 111 static void vm_daemon (void); 112 static struct thread *vmthread; 113 114 static struct kproc_desc vm_kp = { 115 "vmdaemon", 116 vm_daemon, 117 &vmthread 118 }; 119 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp) 120 #endif 121 122 123 int vm_pages_needed=0; /* Event on which pageout daemon sleeps */ 124 int vm_pageout_deficit=0; /* Estimated number of pages deficit */ 125 int vm_pageout_pages_needed=0; /* flag saying that the pageout daemon needs pages */ 126 127 #if !defined(NO_SWAPPING) 128 static int vm_pageout_req_swapout; /* XXX */ 129 static int vm_daemon_needed; 130 #endif 131 static int vm_max_launder = 32; 132 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0; 133 static int vm_pageout_full_stats_interval = 0; 134 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0; 135 static int defer_swap_pageouts=0; 136 static int disable_swap_pageouts=0; 137 138 #if defined(NO_SWAPPING) 139 static int vm_swap_enabled=0; 140 static int vm_swap_idle_enabled=0; 141 #else 142 static int vm_swap_enabled=1; 143 static int vm_swap_idle_enabled=0; 144 #endif 145 146 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm, 147 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt"); 148 149 SYSCTL_INT(_vm, OID_AUTO, max_launder, 150 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout"); 151 152 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max, 153 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length"); 154 155 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval, 156 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan"); 157 158 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval, 159 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan"); 160 161 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max, 162 CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented"); 163 164 #if defined(NO_SWAPPING) 165 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 166 CTLFLAG_RD, &vm_swap_enabled, 0, ""); 167 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 168 CTLFLAG_RD, &vm_swap_idle_enabled, 0, ""); 169 #else 170 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 171 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 172 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 173 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 174 #endif 175 176 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts, 177 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem"); 178 179 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 180 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 181 182 static int pageout_lock_miss; 183 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 184 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 185 186 int vm_load; 187 SYSCTL_INT(_vm, OID_AUTO, vm_load, 188 CTLFLAG_RD, &vm_load, 0, "load on the VM system"); 189 int vm_load_enable = 1; 190 SYSCTL_INT(_vm, OID_AUTO, vm_load_enable, 191 CTLFLAG_RW, &vm_load_enable, 0, "enable vm_load rate limiting"); 192 #ifdef INVARIANTS 193 int vm_load_debug; 194 SYSCTL_INT(_vm, OID_AUTO, vm_load_debug, 195 CTLFLAG_RW, &vm_load_debug, 0, "debug vm_load"); 196 #endif 197 198 #define VM_PAGEOUT_PAGE_COUNT 16 199 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 200 201 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 202 203 #if !defined(NO_SWAPPING) 204 typedef void freeer_fcn_t (vm_map_t, vm_object_t, vm_pindex_t, int); 205 static void vm_pageout_map_deactivate_pages (vm_map_t, vm_pindex_t); 206 static freeer_fcn_t vm_pageout_object_deactivate_pages; 207 static void vm_req_vmdaemon (void); 208 #endif 209 static void vm_pageout_page_stats(void); 210 211 /* 212 * Update vm_load to slow down faulting processes. 213 * 214 * SMP races ok. 215 * No requirements. 216 */ 217 void 218 vm_fault_ratecheck(void) 219 { 220 if (vm_pages_needed) { 221 if (vm_load < 1000) 222 ++vm_load; 223 } else { 224 if (vm_load > 0) 225 --vm_load; 226 } 227 } 228 229 /* 230 * vm_pageout_clean: 231 * 232 * Clean the page and remove it from the laundry. The page must not be 233 * busy on-call. 234 * 235 * We set the busy bit to cause potential page faults on this page to 236 * block. Note the careful timing, however, the busy bit isn't set till 237 * late and we cannot do anything that will mess with the page. 238 * 239 * The caller must hold vm_token. 240 */ 241 static int 242 vm_pageout_clean(vm_page_t m) 243 { 244 vm_object_t object; 245 vm_page_t mc[2*vm_pageout_page_count]; 246 int pageout_count; 247 int ib, is, page_base; 248 vm_pindex_t pindex = m->pindex; 249 250 object = m->object; 251 252 /* 253 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP 254 * with the new swapper, but we could have serious problems paging 255 * out other object types if there is insufficient memory. 256 * 257 * Unfortunately, checking free memory here is far too late, so the 258 * check has been moved up a procedural level. 259 */ 260 261 /* 262 * Don't mess with the page if it's busy, held, or special 263 */ 264 if ((m->hold_count != 0) || 265 ((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) { 266 return 0; 267 } 268 269 mc[vm_pageout_page_count] = m; 270 pageout_count = 1; 271 page_base = vm_pageout_page_count; 272 ib = 1; 273 is = 1; 274 275 /* 276 * Scan object for clusterable pages. 277 * 278 * We can cluster ONLY if: ->> the page is NOT 279 * clean, wired, busy, held, or mapped into a 280 * buffer, and one of the following: 281 * 1) The page is inactive, or a seldom used 282 * active page. 283 * -or- 284 * 2) we force the issue. 285 * 286 * During heavy mmap/modification loads the pageout 287 * daemon can really fragment the underlying file 288 * due to flushing pages out of order and not trying 289 * align the clusters (which leave sporatic out-of-order 290 * holes). To solve this problem we do the reverse scan 291 * first and attempt to align our cluster, then do a 292 * forward scan if room remains. 293 */ 294 295 vm_object_hold(object); 296 more: 297 while (ib && pageout_count < vm_pageout_page_count) { 298 vm_page_t p; 299 300 if (ib > pindex) { 301 ib = 0; 302 break; 303 } 304 305 if ((p = vm_page_lookup(object, pindex - ib)) == NULL) { 306 ib = 0; 307 break; 308 } 309 if (((p->queue - p->pc) == PQ_CACHE) || 310 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) { 311 ib = 0; 312 break; 313 } 314 vm_page_test_dirty(p); 315 if ((p->dirty & p->valid) == 0 || 316 p->queue != PQ_INACTIVE || 317 p->wire_count != 0 || /* may be held by buf cache */ 318 p->hold_count != 0) { /* may be undergoing I/O */ 319 ib = 0; 320 break; 321 } 322 mc[--page_base] = p; 323 ++pageout_count; 324 ++ib; 325 /* 326 * alignment boundry, stop here and switch directions. Do 327 * not clear ib. 328 */ 329 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 330 break; 331 } 332 333 while (pageout_count < vm_pageout_page_count && 334 pindex + is < object->size) { 335 vm_page_t p; 336 337 if ((p = vm_page_lookup(object, pindex + is)) == NULL) 338 break; 339 if (((p->queue - p->pc) == PQ_CACHE) || 340 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) { 341 break; 342 } 343 vm_page_test_dirty(p); 344 if ((p->dirty & p->valid) == 0 || 345 p->queue != PQ_INACTIVE || 346 p->wire_count != 0 || /* may be held by buf cache */ 347 p->hold_count != 0) { /* may be undergoing I/O */ 348 break; 349 } 350 mc[page_base + pageout_count] = p; 351 ++pageout_count; 352 ++is; 353 } 354 355 /* 356 * If we exhausted our forward scan, continue with the reverse scan 357 * when possible, even past a page boundry. This catches boundry 358 * conditions. 359 */ 360 if (ib && pageout_count < vm_pageout_page_count) 361 goto more; 362 363 vm_object_drop(object); 364 365 /* 366 * we allow reads during pageouts... 367 */ 368 return vm_pageout_flush(&mc[page_base], pageout_count, 0); 369 } 370 371 /* 372 * vm_pageout_flush() - launder the given pages 373 * 374 * The given pages are laundered. Note that we setup for the start of 375 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 376 * reference count all in here rather then in the parent. If we want 377 * the parent to do more sophisticated things we may have to change 378 * the ordering. 379 * 380 * The caller must hold vm_token. 381 */ 382 int 383 vm_pageout_flush(vm_page_t *mc, int count, int flags) 384 { 385 vm_object_t object; 386 int pageout_status[count]; 387 int numpagedout = 0; 388 int i; 389 390 ASSERT_LWKT_TOKEN_HELD(&vm_token); 391 392 /* 393 * Initiate I/O. Bump the vm_page_t->busy counter. 394 */ 395 for (i = 0; i < count; i++) { 396 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, ("vm_pageout_flush page %p index %d/%d: partially invalid page", mc[i], i, count)); 397 vm_page_io_start(mc[i]); 398 } 399 400 /* 401 * We must make the pages read-only. This will also force the 402 * modified bit in the related pmaps to be cleared. The pager 403 * cannot clear the bit for us since the I/O completion code 404 * typically runs from an interrupt. The act of making the page 405 * read-only handles the case for us. 406 */ 407 for (i = 0; i < count; i++) { 408 vm_page_protect(mc[i], VM_PROT_READ); 409 } 410 411 object = mc[0]->object; 412 vm_object_pip_add(object, count); 413 414 vm_pager_put_pages(object, mc, count, 415 (flags | ((object == &kernel_object) ? VM_PAGER_PUT_SYNC : 0)), 416 pageout_status); 417 418 for (i = 0; i < count; i++) { 419 vm_page_t mt = mc[i]; 420 421 switch (pageout_status[i]) { 422 case VM_PAGER_OK: 423 numpagedout++; 424 break; 425 case VM_PAGER_PEND: 426 numpagedout++; 427 break; 428 case VM_PAGER_BAD: 429 /* 430 * Page outside of range of object. Right now we 431 * essentially lose the changes by pretending it 432 * worked. 433 */ 434 pmap_clear_modify(mt); 435 vm_page_undirty(mt); 436 break; 437 case VM_PAGER_ERROR: 438 case VM_PAGER_FAIL: 439 /* 440 * A page typically cannot be paged out when we 441 * have run out of swap. We leave the page 442 * marked inactive and will try to page it out 443 * again later. 444 * 445 * Starvation of the active page list is used to 446 * determine when the system is massively memory 447 * starved. 448 */ 449 break; 450 case VM_PAGER_AGAIN: 451 break; 452 } 453 454 /* 455 * If the operation is still going, leave the page busy to 456 * block all other accesses. Also, leave the paging in 457 * progress indicator set so that we don't attempt an object 458 * collapse. 459 * 460 * For any pages which have completed synchronously, 461 * deactivate the page if we are under a severe deficit. 462 * Do not try to enter them into the cache, though, they 463 * might still be read-heavy. 464 */ 465 if (pageout_status[i] != VM_PAGER_PEND) { 466 if (vm_page_count_severe()) 467 vm_page_deactivate(mt); 468 #if 0 469 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt)) 470 vm_page_protect(mt, VM_PROT_READ); 471 #endif 472 vm_page_io_finish(mt); 473 vm_object_pip_wakeup(object); 474 } 475 } 476 return numpagedout; 477 } 478 479 #if !defined(NO_SWAPPING) 480 /* 481 * vm_pageout_object_deactivate_pages 482 * 483 * deactivate enough pages to satisfy the inactive target 484 * requirements or if vm_page_proc_limit is set, then 485 * deactivate all of the pages in the object and its 486 * backing_objects. 487 * 488 * The map must be locked. 489 * The caller must hold vm_token. 490 * The caller must hold the vm_object. 491 */ 492 static int vm_pageout_object_deactivate_pages_callback(vm_page_t, void *); 493 494 static void 495 vm_pageout_object_deactivate_pages(vm_map_t map, vm_object_t object, 496 vm_pindex_t desired, int map_remove_only) 497 { 498 struct rb_vm_page_scan_info info; 499 vm_object_t tmp; 500 int remove_mode; 501 502 while (object) { 503 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 504 return; 505 506 vm_object_hold(object); 507 508 if (object->type == OBJT_DEVICE || object->type == OBJT_PHYS) { 509 vm_object_drop(object); 510 return; 511 } 512 if (object->paging_in_progress) { 513 vm_object_drop(object); 514 return; 515 } 516 517 remove_mode = map_remove_only; 518 if (object->shadow_count > 1) 519 remove_mode = 1; 520 521 /* 522 * scan the objects entire memory queue. spl protection is 523 * required to avoid an interrupt unbusy/free race against 524 * our busy check. 525 */ 526 crit_enter(); 527 info.limit = remove_mode; 528 info.map = map; 529 info.desired = desired; 530 vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL, 531 vm_pageout_object_deactivate_pages_callback, 532 &info 533 ); 534 crit_exit(); 535 tmp = object->backing_object; 536 vm_object_drop(object); 537 object = tmp; 538 } 539 } 540 541 /* 542 * The caller must hold vm_token. 543 * The caller must hold the vm_object. 544 */ 545 static int 546 vm_pageout_object_deactivate_pages_callback(vm_page_t p, void *data) 547 { 548 struct rb_vm_page_scan_info *info = data; 549 int actcount; 550 551 if (pmap_resident_count(vm_map_pmap(info->map)) <= info->desired) { 552 return(-1); 553 } 554 mycpu->gd_cnt.v_pdpages++; 555 if (p->wire_count != 0 || p->hold_count != 0 || p->busy != 0 || 556 (p->flags & (PG_BUSY|PG_UNMANAGED)) || 557 !pmap_page_exists_quick(vm_map_pmap(info->map), p)) { 558 return(0); 559 } 560 561 actcount = pmap_ts_referenced(p); 562 if (actcount) { 563 vm_page_flag_set(p, PG_REFERENCED); 564 } else if (p->flags & PG_REFERENCED) { 565 actcount = 1; 566 } 567 568 if ((p->queue != PQ_ACTIVE) && 569 (p->flags & PG_REFERENCED)) { 570 vm_page_activate(p); 571 p->act_count += actcount; 572 vm_page_flag_clear(p, PG_REFERENCED); 573 } else if (p->queue == PQ_ACTIVE) { 574 if ((p->flags & PG_REFERENCED) == 0) { 575 p->act_count -= min(p->act_count, ACT_DECLINE); 576 if (!info->limit && (vm_pageout_algorithm || (p->act_count == 0))) { 577 vm_page_busy(p); 578 vm_page_protect(p, VM_PROT_NONE); 579 vm_page_deactivate(p); 580 vm_page_wakeup(p); 581 } else { 582 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 583 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 584 } 585 } else { 586 vm_page_activate(p); 587 vm_page_flag_clear(p, PG_REFERENCED); 588 if (p->act_count < (ACT_MAX - ACT_ADVANCE)) 589 p->act_count += ACT_ADVANCE; 590 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 591 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 592 } 593 } else if (p->queue == PQ_INACTIVE) { 594 vm_page_busy(p); 595 vm_page_protect(p, VM_PROT_NONE); 596 vm_page_wakeup(p); 597 } 598 return(0); 599 } 600 601 /* 602 * Deactivate some number of pages in a map, try to do it fairly, but 603 * that is really hard to do. 604 * 605 * The caller must hold vm_token. 606 */ 607 static void 608 vm_pageout_map_deactivate_pages(vm_map_t map, vm_pindex_t desired) 609 { 610 vm_map_entry_t tmpe; 611 vm_object_t obj, bigobj; 612 int nothingwired; 613 614 if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT)) { 615 return; 616 } 617 618 bigobj = NULL; 619 nothingwired = TRUE; 620 621 /* 622 * first, search out the biggest object, and try to free pages from 623 * that. 624 */ 625 tmpe = map->header.next; 626 while (tmpe != &map->header) { 627 switch(tmpe->maptype) { 628 case VM_MAPTYPE_NORMAL: 629 case VM_MAPTYPE_VPAGETABLE: 630 obj = tmpe->object.vm_object; 631 if ((obj != NULL) && (obj->shadow_count <= 1) && 632 ((bigobj == NULL) || 633 (bigobj->resident_page_count < obj->resident_page_count))) { 634 bigobj = obj; 635 } 636 break; 637 default: 638 break; 639 } 640 if (tmpe->wired_count > 0) 641 nothingwired = FALSE; 642 tmpe = tmpe->next; 643 } 644 645 if (bigobj) 646 vm_pageout_object_deactivate_pages(map, bigobj, desired, 0); 647 648 /* 649 * Next, hunt around for other pages to deactivate. We actually 650 * do this search sort of wrong -- .text first is not the best idea. 651 */ 652 tmpe = map->header.next; 653 while (tmpe != &map->header) { 654 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 655 break; 656 switch(tmpe->maptype) { 657 case VM_MAPTYPE_NORMAL: 658 case VM_MAPTYPE_VPAGETABLE: 659 obj = tmpe->object.vm_object; 660 if (obj) 661 vm_pageout_object_deactivate_pages(map, obj, desired, 0); 662 break; 663 default: 664 break; 665 } 666 tmpe = tmpe->next; 667 }; 668 669 /* 670 * Remove all mappings if a process is swapped out, this will free page 671 * table pages. 672 */ 673 if (desired == 0 && nothingwired) 674 pmap_remove(vm_map_pmap(map), 675 VM_MIN_USER_ADDRESS, VM_MAX_USER_ADDRESS); 676 vm_map_unlock(map); 677 } 678 #endif 679 680 /* 681 * Don't try to be fancy - being fancy can lead to vnode deadlocks. We 682 * only do it for OBJT_DEFAULT and OBJT_SWAP objects which we know can 683 * be trivially freed. 684 * 685 * The caller must hold vm_token. 686 * 687 * WARNING: vm_object_reference() can block. 688 */ 689 static void 690 vm_pageout_page_free(vm_page_t m) 691 { 692 vm_object_t object = m->object; 693 int type = object->type; 694 695 vm_page_busy(m); 696 if (type == OBJT_SWAP || type == OBJT_DEFAULT) 697 vm_object_reference(object); 698 vm_page_protect(m, VM_PROT_NONE); 699 vm_page_free(m); 700 if (type == OBJT_SWAP || type == OBJT_DEFAULT) 701 vm_object_deallocate(object); 702 } 703 704 /* 705 * vm_pageout_scan does the dirty work for the pageout daemon. 706 */ 707 struct vm_pageout_scan_info { 708 struct proc *bigproc; 709 vm_offset_t bigsize; 710 }; 711 712 static int vm_pageout_scan_callback(struct proc *p, void *data); 713 714 /* 715 * The caller must hold vm_token. 716 */ 717 static int 718 vm_pageout_scan(int pass) 719 { 720 struct vm_pageout_scan_info info; 721 vm_page_t m, next; 722 struct vm_page marker; 723 struct vnode *vpfailed; /* warning, allowed to be stale */ 724 int maxscan, pcount; 725 int recycle_count; 726 int inactive_shortage, active_shortage; 727 int inactive_original_shortage; 728 vm_object_t object; 729 int actcount; 730 int vnodes_skipped = 0; 731 int maxlaunder; 732 733 /* 734 * Do whatever cleanup that the pmap code can. 735 */ 736 pmap_collect(); 737 738 /* 739 * Calculate our target for the number of free+cache pages we 740 * want to get to. This is higher then the number that causes 741 * allocations to stall (severe) in order to provide hysteresis, 742 * and if we don't make it all the way but get to the minimum 743 * we're happy. 744 */ 745 inactive_shortage = vm_paging_target() + vm_pageout_deficit; 746 inactive_original_shortage = inactive_shortage; 747 vm_pageout_deficit = 0; 748 749 /* 750 * Initialize our marker 751 */ 752 bzero(&marker, sizeof(marker)); 753 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER; 754 marker.queue = PQ_INACTIVE; 755 marker.wire_count = 1; 756 757 /* 758 * Start scanning the inactive queue for pages we can move to the 759 * cache or free. The scan will stop when the target is reached or 760 * we have scanned the entire inactive queue. Note that m->act_count 761 * is not used to form decisions for the inactive queue, only for the 762 * active queue. 763 * 764 * maxlaunder limits the number of dirty pages we flush per scan. 765 * For most systems a smaller value (16 or 32) is more robust under 766 * extreme memory and disk pressure because any unnecessary writes 767 * to disk can result in extreme performance degredation. However, 768 * systems with excessive dirty pages (especially when MAP_NOSYNC is 769 * used) will die horribly with limited laundering. If the pageout 770 * daemon cannot clean enough pages in the first pass, we let it go 771 * all out in succeeding passes. 772 */ 773 if ((maxlaunder = vm_max_launder) <= 1) 774 maxlaunder = 1; 775 if (pass) 776 maxlaunder = 10000; 777 778 /* 779 * We will generally be in a critical section throughout the 780 * scan, but we can release it temporarily when we are sitting on a 781 * non-busy page without fear. this is required to prevent an 782 * interrupt from unbusying or freeing a page prior to our busy 783 * check, leaving us on the wrong queue or checking the wrong 784 * page. 785 */ 786 crit_enter(); 787 rescan0: 788 vpfailed = NULL; 789 maxscan = vmstats.v_inactive_count; 790 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl); 791 m != NULL && maxscan-- > 0 && inactive_shortage > 0; 792 m = next 793 ) { 794 mycpu->gd_cnt.v_pdpages++; 795 796 /* 797 * Give interrupts a chance 798 */ 799 crit_exit(); 800 crit_enter(); 801 802 /* 803 * It's easier for some of the conditions below to just loop 804 * and catch queue changes here rather then check everywhere 805 * else. 806 */ 807 if (m->queue != PQ_INACTIVE) 808 goto rescan0; 809 next = TAILQ_NEXT(m, pageq); 810 811 /* 812 * skip marker pages 813 */ 814 if (m->flags & PG_MARKER) 815 continue; 816 817 /* 818 * A held page may be undergoing I/O, so skip it. 819 */ 820 if (m->hold_count) { 821 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 822 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 823 ++vm_swapcache_inactive_heuristic; 824 continue; 825 } 826 827 /* 828 * Dont mess with busy pages, keep in the front of the 829 * queue, most likely are being paged out. 830 */ 831 if (m->busy || (m->flags & PG_BUSY)) { 832 continue; 833 } 834 835 if (m->object->ref_count == 0) { 836 /* 837 * If the object is not being used, we ignore previous 838 * references. 839 */ 840 vm_page_flag_clear(m, PG_REFERENCED); 841 pmap_clear_reference(m); 842 843 } else if (((m->flags & PG_REFERENCED) == 0) && 844 (actcount = pmap_ts_referenced(m))) { 845 /* 846 * Otherwise, if the page has been referenced while 847 * in the inactive queue, we bump the "activation 848 * count" upwards, making it less likely that the 849 * page will be added back to the inactive queue 850 * prematurely again. Here we check the page tables 851 * (or emulated bits, if any), given the upper level 852 * VM system not knowing anything about existing 853 * references. 854 */ 855 vm_page_activate(m); 856 m->act_count += (actcount + ACT_ADVANCE); 857 continue; 858 } 859 860 /* 861 * If the upper level VM system knows about any page 862 * references, we activate the page. We also set the 863 * "activation count" higher than normal so that we will less 864 * likely place pages back onto the inactive queue again. 865 */ 866 if ((m->flags & PG_REFERENCED) != 0) { 867 vm_page_flag_clear(m, PG_REFERENCED); 868 actcount = pmap_ts_referenced(m); 869 vm_page_activate(m); 870 m->act_count += (actcount + ACT_ADVANCE + 1); 871 continue; 872 } 873 874 /* 875 * If the upper level VM system doesn't know anything about 876 * the page being dirty, we have to check for it again. As 877 * far as the VM code knows, any partially dirty pages are 878 * fully dirty. 879 * 880 * Pages marked PG_WRITEABLE may be mapped into the user 881 * address space of a process running on another cpu. A 882 * user process (without holding the MP lock) running on 883 * another cpu may be able to touch the page while we are 884 * trying to remove it. vm_page_cache() will handle this 885 * case for us. 886 */ 887 if (m->dirty == 0) { 888 vm_page_test_dirty(m); 889 } else { 890 vm_page_dirty(m); 891 } 892 893 if (m->valid == 0) { 894 /* 895 * Invalid pages can be easily freed 896 */ 897 vm_pageout_page_free(m); 898 mycpu->gd_cnt.v_dfree++; 899 --inactive_shortage; 900 } else if (m->dirty == 0) { 901 /* 902 * Clean pages can be placed onto the cache queue. 903 * This effectively frees them. 904 */ 905 vm_page_busy(m); 906 vm_page_cache(m); 907 --inactive_shortage; 908 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) { 909 /* 910 * Dirty pages need to be paged out, but flushing 911 * a page is extremely expensive verses freeing 912 * a clean page. Rather then artificially limiting 913 * the number of pages we can flush, we instead give 914 * dirty pages extra priority on the inactive queue 915 * by forcing them to be cycled through the queue 916 * twice before being flushed, after which the 917 * (now clean) page will cycle through once more 918 * before being freed. This significantly extends 919 * the thrash point for a heavily loaded machine. 920 */ 921 vm_page_flag_set(m, PG_WINATCFLS); 922 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 923 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 924 ++vm_swapcache_inactive_heuristic; 925 } else if (maxlaunder > 0) { 926 /* 927 * We always want to try to flush some dirty pages if 928 * we encounter them, to keep the system stable. 929 * Normally this number is small, but under extreme 930 * pressure where there are insufficient clean pages 931 * on the inactive queue, we may have to go all out. 932 */ 933 int swap_pageouts_ok; 934 struct vnode *vp = NULL; 935 936 object = m->object; 937 938 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) { 939 swap_pageouts_ok = 1; 940 } else { 941 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts); 942 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts && 943 vm_page_count_min(0)); 944 945 } 946 947 /* 948 * We don't bother paging objects that are "dead". 949 * Those objects are in a "rundown" state. 950 */ 951 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) { 952 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 953 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 954 ++vm_swapcache_inactive_heuristic; 955 continue; 956 } 957 958 /* 959 * The object is already known NOT to be dead. It 960 * is possible for the vget() to block the whole 961 * pageout daemon, but the new low-memory handling 962 * code should prevent it. 963 * 964 * The previous code skipped locked vnodes and, worse, 965 * reordered pages in the queue. This results in 966 * completely non-deterministic operation because, 967 * quite often, a vm_fault has initiated an I/O and 968 * is holding a locked vnode at just the point where 969 * the pageout daemon is woken up. 970 * 971 * We can't wait forever for the vnode lock, we might 972 * deadlock due to a vn_read() getting stuck in 973 * vm_wait while holding this vnode. We skip the 974 * vnode if we can't get it in a reasonable amount 975 * of time. 976 * 977 * vpfailed is used to (try to) avoid the case where 978 * a large number of pages are associated with a 979 * locked vnode, which could cause the pageout daemon 980 * to stall for an excessive amount of time. 981 */ 982 if (object->type == OBJT_VNODE) { 983 int flags; 984 985 vp = object->handle; 986 flags = LK_EXCLUSIVE | LK_NOOBJ; 987 if (vp == vpfailed) 988 flags |= LK_NOWAIT; 989 else 990 flags |= LK_TIMELOCK; 991 if (vget(vp, flags) != 0) { 992 vpfailed = vp; 993 ++pageout_lock_miss; 994 if (object->flags & OBJ_MIGHTBEDIRTY) 995 vnodes_skipped++; 996 continue; 997 } 998 999 /* 1000 * The page might have been moved to another 1001 * queue during potential blocking in vget() 1002 * above. The page might have been freed and 1003 * reused for another vnode. The object might 1004 * have been reused for another vnode. 1005 */ 1006 if (m->queue != PQ_INACTIVE || 1007 m->object != object || 1008 object->handle != vp) { 1009 if (object->flags & OBJ_MIGHTBEDIRTY) 1010 vnodes_skipped++; 1011 vput(vp); 1012 continue; 1013 } 1014 1015 /* 1016 * The page may have been busied during the 1017 * blocking in vput(); We don't move the 1018 * page back onto the end of the queue so that 1019 * statistics are more correct if we don't. 1020 */ 1021 if (m->busy || (m->flags & PG_BUSY)) { 1022 vput(vp); 1023 continue; 1024 } 1025 1026 /* 1027 * If the page has become held it might 1028 * be undergoing I/O, so skip it 1029 */ 1030 if (m->hold_count) { 1031 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 1032 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 1033 ++vm_swapcache_inactive_heuristic; 1034 if (object->flags & OBJ_MIGHTBEDIRTY) 1035 vnodes_skipped++; 1036 vput(vp); 1037 continue; 1038 } 1039 } 1040 1041 /* 1042 * If a page is dirty, then it is either being washed 1043 * (but not yet cleaned) or it is still in the 1044 * laundry. If it is still in the laundry, then we 1045 * start the cleaning operation. 1046 * 1047 * This operation may cluster, invalidating the 'next' 1048 * pointer. To prevent an inordinate number of 1049 * restarts we use our marker to remember our place. 1050 * 1051 * decrement inactive_shortage on success to account 1052 * for the (future) cleaned page. Otherwise we 1053 * could wind up laundering or cleaning too many 1054 * pages. 1055 */ 1056 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq); 1057 if (vm_pageout_clean(m) != 0) { 1058 --inactive_shortage; 1059 --maxlaunder; 1060 } 1061 next = TAILQ_NEXT(&marker, pageq); 1062 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq); 1063 if (vp != NULL) 1064 vput(vp); 1065 } 1066 } 1067 1068 /* 1069 * We want to move pages from the active queue to the inactive 1070 * queue to get the inactive queue to the inactive target. If 1071 * we still have a page shortage from above we try to directly free 1072 * clean pages instead of moving them. 1073 * 1074 * If we do still have a shortage we keep track of the number of 1075 * pages we free or cache (recycle_count) as a measure of thrashing 1076 * between the active and inactive queues. 1077 * 1078 * If we were able to completely satisfy the free+cache targets 1079 * from the inactive pool we limit the number of pages we move 1080 * from the active pool to the inactive pool to 2x the pages we 1081 * had removed from the inactive pool (with a minimum of 1/5 the 1082 * inactive target). If we were not able to completely satisfy 1083 * the free+cache targets we go for the whole target aggressively. 1084 * 1085 * NOTE: Both variables can end up negative. 1086 * NOTE: We are still in a critical section. 1087 */ 1088 active_shortage = vmstats.v_inactive_target - vmstats.v_inactive_count; 1089 if (inactive_original_shortage < vmstats.v_inactive_target / 10) 1090 inactive_original_shortage = vmstats.v_inactive_target / 10; 1091 if (inactive_shortage <= 0 && 1092 active_shortage > inactive_original_shortage * 2) { 1093 active_shortage = inactive_original_shortage * 2; 1094 } 1095 1096 pcount = vmstats.v_active_count; 1097 recycle_count = 0; 1098 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); 1099 1100 while ((m != NULL) && (pcount-- > 0) && 1101 (inactive_shortage > 0 || active_shortage > 0) 1102 ) { 1103 /* 1104 * Give interrupts a chance. 1105 */ 1106 crit_exit(); 1107 crit_enter(); 1108 1109 /* 1110 * If the page was ripped out from under us, just stop. 1111 */ 1112 if (m->queue != PQ_ACTIVE) 1113 break; 1114 next = TAILQ_NEXT(m, pageq); 1115 1116 /* 1117 * Don't deactivate pages that are busy. 1118 */ 1119 if ((m->busy != 0) || 1120 (m->flags & PG_BUSY) || 1121 (m->hold_count != 0)) { 1122 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1123 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1124 m = next; 1125 continue; 1126 } 1127 1128 /* 1129 * The count for pagedaemon pages is done after checking the 1130 * page for eligibility... 1131 */ 1132 mycpu->gd_cnt.v_pdpages++; 1133 1134 /* 1135 * Check to see "how much" the page has been used and clear 1136 * the tracking access bits. If the object has no references 1137 * don't bother paying the expense. 1138 */ 1139 actcount = 0; 1140 if (m->object->ref_count != 0) { 1141 if (m->flags & PG_REFERENCED) 1142 ++actcount; 1143 actcount += pmap_ts_referenced(m); 1144 if (actcount) { 1145 m->act_count += ACT_ADVANCE + actcount; 1146 if (m->act_count > ACT_MAX) 1147 m->act_count = ACT_MAX; 1148 } 1149 } 1150 vm_page_flag_clear(m, PG_REFERENCED); 1151 1152 /* 1153 * actcount is only valid if the object ref_count is non-zero. 1154 */ 1155 if (actcount && m->object->ref_count != 0) { 1156 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1157 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1158 } else { 1159 m->act_count -= min(m->act_count, ACT_DECLINE); 1160 if (vm_pageout_algorithm || 1161 m->object->ref_count == 0 || 1162 m->act_count < pass + 1 1163 ) { 1164 /* 1165 * Deactivate the page. If we had a 1166 * shortage from our inactive scan try to 1167 * free (cache) the page instead. 1168 * 1169 * Don't just blindly cache the page if 1170 * we do not have a shortage from the 1171 * inactive scan, that could lead to 1172 * gigabytes being moved. 1173 */ 1174 --active_shortage; 1175 if (inactive_shortage > 0 || 1176 m->object->ref_count == 0) { 1177 if (inactive_shortage > 0) 1178 ++recycle_count; 1179 vm_page_busy(m); 1180 vm_page_protect(m, VM_PROT_NONE); 1181 if (m->dirty == 0 && 1182 inactive_shortage > 0) { 1183 --inactive_shortage; 1184 vm_page_cache(m); 1185 } else { 1186 vm_page_deactivate(m); 1187 vm_page_wakeup(m); 1188 } 1189 } else { 1190 vm_page_deactivate(m); 1191 } 1192 } else { 1193 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1194 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1195 } 1196 } 1197 m = next; 1198 } 1199 1200 /* 1201 * The number of actually free pages can drop down to v_free_reserved, 1202 * we try to build the free count back above v_free_min. Note that 1203 * vm_paging_needed() also returns TRUE if v_free_count is not at 1204 * least v_free_min so that is the minimum we must build the free 1205 * count to. 1206 * 1207 * We use a slightly higher target to improve hysteresis, 1208 * ((v_free_target + v_free_min) / 2). Since v_free_target 1209 * is usually the same as v_cache_min this maintains about 1210 * half the pages in the free queue as are in the cache queue, 1211 * providing pretty good pipelining for pageout operation. 1212 * 1213 * The system operator can manipulate vm.v_cache_min and 1214 * vm.v_free_target to tune the pageout demon. Be sure 1215 * to keep vm.v_free_min < vm.v_free_target. 1216 * 1217 * Note that the original paging target is to get at least 1218 * (free_min + cache_min) into (free + cache). The slightly 1219 * higher target will shift additional pages from cache to free 1220 * without effecting the original paging target in order to 1221 * maintain better hysteresis and not have the free count always 1222 * be dead-on v_free_min. 1223 * 1224 * NOTE: we are still in a critical section. 1225 * 1226 * Pages moved from PQ_CACHE to totally free are not counted in the 1227 * pages_freed counter. 1228 */ 1229 while (vmstats.v_free_count < 1230 (vmstats.v_free_min + vmstats.v_free_target) / 2) { 1231 /* 1232 * 1233 */ 1234 static int cache_rover = 0; 1235 m = vm_page_list_find(PQ_CACHE, cache_rover, FALSE); 1236 if (m == NULL) 1237 break; 1238 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || 1239 m->busy || 1240 m->hold_count || 1241 m->wire_count) { 1242 #ifdef INVARIANTS 1243 kprintf("Warning: busy page %p found in cache\n", m); 1244 #endif 1245 vm_page_deactivate(m); 1246 continue; 1247 } 1248 KKASSERT((m->flags & PG_MAPPED) == 0); 1249 KKASSERT(m->dirty == 0); 1250 cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK; 1251 vm_pageout_page_free(m); 1252 mycpu->gd_cnt.v_dfree++; 1253 } 1254 1255 crit_exit(); 1256 1257 #if !defined(NO_SWAPPING) 1258 /* 1259 * Idle process swapout -- run once per second. 1260 */ 1261 if (vm_swap_idle_enabled) { 1262 static long lsec; 1263 if (time_second != lsec) { 1264 vm_pageout_req_swapout |= VM_SWAP_IDLE; 1265 vm_req_vmdaemon(); 1266 lsec = time_second; 1267 } 1268 } 1269 #endif 1270 1271 /* 1272 * If we didn't get enough free pages, and we have skipped a vnode 1273 * in a writeable object, wakeup the sync daemon. And kick swapout 1274 * if we did not get enough free pages. 1275 */ 1276 if (vm_paging_target() > 0) { 1277 if (vnodes_skipped && vm_page_count_min(0)) 1278 speedup_syncer(); 1279 #if !defined(NO_SWAPPING) 1280 if (vm_swap_enabled && vm_page_count_target()) { 1281 vm_req_vmdaemon(); 1282 vm_pageout_req_swapout |= VM_SWAP_NORMAL; 1283 } 1284 #endif 1285 } 1286 1287 /* 1288 * Handle catastrophic conditions. Under good conditions we should 1289 * be at the target, well beyond our minimum. If we could not even 1290 * reach our minimum the system is under heavy stress. 1291 * 1292 * Determine whether we have run out of memory. This occurs when 1293 * swap_pager_full is TRUE and the only pages left in the page 1294 * queues are dirty. We will still likely have page shortages. 1295 * 1296 * - swap_pager_full is set if insufficient swap was 1297 * available to satisfy a requested pageout. 1298 * 1299 * - the inactive queue is bloated (4 x size of active queue), 1300 * meaning it is unable to get rid of dirty pages and. 1301 * 1302 * - vm_page_count_min() without counting pages recycled from the 1303 * active queue (recycle_count) means we could not recover 1304 * enough pages to meet bare minimum needs. This test only 1305 * works if the inactive queue is bloated. 1306 * 1307 * - due to a positive inactive_shortage we shifted the remaining 1308 * dirty pages from the active queue to the inactive queue 1309 * trying to find clean ones to free. 1310 */ 1311 if (swap_pager_full && vm_page_count_min(recycle_count)) 1312 kprintf("Warning: system low on memory+swap!\n"); 1313 if (swap_pager_full && vm_page_count_min(recycle_count) && 1314 vmstats.v_inactive_count > vmstats.v_active_count * 4 && 1315 inactive_shortage > 0) { 1316 /* 1317 * Kill something. 1318 */ 1319 info.bigproc = NULL; 1320 info.bigsize = 0; 1321 allproc_scan(vm_pageout_scan_callback, &info); 1322 if (info.bigproc != NULL) { 1323 killproc(info.bigproc, "out of swap space"); 1324 info.bigproc->p_nice = PRIO_MIN; 1325 info.bigproc->p_usched->resetpriority( 1326 FIRST_LWP_IN_PROC(info.bigproc)); 1327 wakeup(&vmstats.v_free_count); 1328 PRELE(info.bigproc); 1329 } 1330 } 1331 return(inactive_shortage); 1332 } 1333 1334 /* 1335 * The caller must hold vm_token and proc_token. 1336 */ 1337 static int 1338 vm_pageout_scan_callback(struct proc *p, void *data) 1339 { 1340 struct vm_pageout_scan_info *info = data; 1341 vm_offset_t size; 1342 1343 /* 1344 * Never kill system processes or init. If we have configured swap 1345 * then try to avoid killing low-numbered pids. 1346 */ 1347 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) || 1348 ((p->p_pid < 48) && (vm_swap_size != 0))) { 1349 return (0); 1350 } 1351 1352 /* 1353 * if the process is in a non-running type state, 1354 * don't touch it. 1355 */ 1356 if (p->p_stat != SACTIVE && p->p_stat != SSTOP) 1357 return (0); 1358 1359 /* 1360 * Get the approximate process size. Note that anonymous pages 1361 * with backing swap will be counted twice, but there should not 1362 * be too many such pages due to the stress the VM system is 1363 * under at this point. 1364 */ 1365 size = vmspace_anonymous_count(p->p_vmspace) + 1366 vmspace_swap_count(p->p_vmspace); 1367 1368 /* 1369 * If the this process is bigger than the biggest one 1370 * remember it. 1371 */ 1372 if (info->bigsize < size) { 1373 if (info->bigproc) 1374 PRELE(info->bigproc); 1375 PHOLD(p); 1376 info->bigproc = p; 1377 info->bigsize = size; 1378 } 1379 return(0); 1380 } 1381 1382 /* 1383 * This routine tries to maintain the pseudo LRU active queue, 1384 * so that during long periods of time where there is no paging, 1385 * that some statistic accumulation still occurs. This code 1386 * helps the situation where paging just starts to occur. 1387 * 1388 * The caller must hold vm_token. 1389 */ 1390 static void 1391 vm_pageout_page_stats(void) 1392 { 1393 vm_page_t m,next; 1394 int pcount,tpcount; /* Number of pages to check */ 1395 static int fullintervalcount = 0; 1396 int page_shortage; 1397 1398 page_shortage = 1399 (vmstats.v_inactive_target + vmstats.v_cache_max + vmstats.v_free_min) - 1400 (vmstats.v_free_count + vmstats.v_inactive_count + vmstats.v_cache_count); 1401 1402 if (page_shortage <= 0) 1403 return; 1404 1405 crit_enter(); 1406 1407 pcount = vmstats.v_active_count; 1408 fullintervalcount += vm_pageout_stats_interval; 1409 if (fullintervalcount < vm_pageout_full_stats_interval) { 1410 tpcount = (vm_pageout_stats_max * vmstats.v_active_count) / vmstats.v_page_count; 1411 if (pcount > tpcount) 1412 pcount = tpcount; 1413 } else { 1414 fullintervalcount = 0; 1415 } 1416 1417 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); 1418 while ((m != NULL) && (pcount-- > 0)) { 1419 int actcount; 1420 1421 if (m->queue != PQ_ACTIVE) { 1422 break; 1423 } 1424 1425 next = TAILQ_NEXT(m, pageq); 1426 /* 1427 * Don't deactivate pages that are busy. 1428 */ 1429 if ((m->busy != 0) || 1430 (m->flags & PG_BUSY) || 1431 (m->hold_count != 0)) { 1432 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1433 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1434 m = next; 1435 continue; 1436 } 1437 1438 actcount = 0; 1439 if (m->flags & PG_REFERENCED) { 1440 vm_page_flag_clear(m, PG_REFERENCED); 1441 actcount += 1; 1442 } 1443 1444 actcount += pmap_ts_referenced(m); 1445 if (actcount) { 1446 m->act_count += ACT_ADVANCE + actcount; 1447 if (m->act_count > ACT_MAX) 1448 m->act_count = ACT_MAX; 1449 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1450 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1451 } else { 1452 if (m->act_count == 0) { 1453 /* 1454 * We turn off page access, so that we have 1455 * more accurate RSS stats. We don't do this 1456 * in the normal page deactivation when the 1457 * system is loaded VM wise, because the 1458 * cost of the large number of page protect 1459 * operations would be higher than the value 1460 * of doing the operation. 1461 */ 1462 vm_page_busy(m); 1463 vm_page_protect(m, VM_PROT_NONE); 1464 vm_page_deactivate(m); 1465 vm_page_wakeup(m); 1466 } else { 1467 m->act_count -= min(m->act_count, ACT_DECLINE); 1468 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1469 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1470 } 1471 } 1472 1473 m = next; 1474 } 1475 crit_exit(); 1476 } 1477 1478 /* 1479 * The caller must hold vm_token. 1480 */ 1481 static int 1482 vm_pageout_free_page_calc(vm_size_t count) 1483 { 1484 if (count < vmstats.v_page_count) 1485 return 0; 1486 /* 1487 * free_reserved needs to include enough for the largest swap pager 1488 * structures plus enough for any pv_entry structs when paging. 1489 */ 1490 if (vmstats.v_page_count > 1024) 1491 vmstats.v_free_min = 4 + (vmstats.v_page_count - 1024) / 200; 1492 else 1493 vmstats.v_free_min = 4; 1494 vmstats.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 1495 vmstats.v_interrupt_free_min; 1496 vmstats.v_free_reserved = vm_pageout_page_count + 1497 vmstats.v_pageout_free_min + (count / 768) + PQ_L2_SIZE; 1498 vmstats.v_free_severe = vmstats.v_free_min / 2; 1499 vmstats.v_free_min += vmstats.v_free_reserved; 1500 vmstats.v_free_severe += vmstats.v_free_reserved; 1501 return 1; 1502 } 1503 1504 1505 /* 1506 * vm_pageout is the high level pageout daemon. 1507 * 1508 * No requirements. 1509 */ 1510 static void 1511 vm_pageout_thread(void) 1512 { 1513 int pass; 1514 int inactive_shortage; 1515 1516 /* 1517 * Permanently hold vm_token. 1518 */ 1519 lwkt_gettoken(&vm_token); 1520 1521 /* 1522 * Initialize some paging parameters. 1523 */ 1524 curthread->td_flags |= TDF_SYSTHREAD; 1525 1526 vmstats.v_interrupt_free_min = 2; 1527 if (vmstats.v_page_count < 2000) 1528 vm_pageout_page_count = 8; 1529 1530 vm_pageout_free_page_calc(vmstats.v_page_count); 1531 1532 /* 1533 * v_free_target and v_cache_min control pageout hysteresis. Note 1534 * that these are more a measure of the VM cache queue hysteresis 1535 * then the VM free queue. Specifically, v_free_target is the 1536 * high water mark (free+cache pages). 1537 * 1538 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the 1539 * low water mark, while v_free_min is the stop. v_cache_min must 1540 * be big enough to handle memory needs while the pageout daemon 1541 * is signalled and run to free more pages. 1542 */ 1543 if (vmstats.v_free_count > 6144) 1544 vmstats.v_free_target = 4 * vmstats.v_free_min + vmstats.v_free_reserved; 1545 else 1546 vmstats.v_free_target = 2 * vmstats.v_free_min + vmstats.v_free_reserved; 1547 1548 /* 1549 * NOTE: With the new buffer cache b_act_count we want the default 1550 * inactive target to be a percentage of available memory. 1551 * 1552 * The inactive target essentially determines the minimum 1553 * number of 'temporary' pages capable of caching one-time-use 1554 * files when the VM system is otherwise full of pages 1555 * belonging to multi-time-use files or active program data. 1556 * 1557 * NOTE: The inactive target is aggressively persued only if the 1558 * inactive queue becomes too small. If the inactive queue 1559 * is large enough to satisfy page movement to free+cache 1560 * then it is repopulated more slowly from the active queue. 1561 * This allows a general inactive_target default to be set. 1562 * 1563 * There is an issue here for processes which sit mostly idle 1564 * 'overnight', such as sshd, tcsh, and X. Any movement from 1565 * the active queue will eventually cause such pages to 1566 * recycle eventually causing a lot of paging in the morning. 1567 * To reduce the incidence of this pages cycled out of the 1568 * buffer cache are moved directly to the inactive queue if 1569 * they were only used once or twice. 1570 * 1571 * The vfs.vm_cycle_point sysctl can be used to adjust this. 1572 * Increasing the value (up to 64) increases the number of 1573 * buffer recyclements which go directly to the inactive queue. 1574 */ 1575 if (vmstats.v_free_count > 2048) { 1576 vmstats.v_cache_min = vmstats.v_free_target; 1577 vmstats.v_cache_max = 2 * vmstats.v_cache_min; 1578 } else { 1579 vmstats.v_cache_min = 0; 1580 vmstats.v_cache_max = 0; 1581 } 1582 vmstats.v_inactive_target = vmstats.v_free_count / 4; 1583 1584 /* XXX does not really belong here */ 1585 if (vm_page_max_wired == 0) 1586 vm_page_max_wired = vmstats.v_free_count / 3; 1587 1588 if (vm_pageout_stats_max == 0) 1589 vm_pageout_stats_max = vmstats.v_free_target; 1590 1591 /* 1592 * Set interval in seconds for stats scan. 1593 */ 1594 if (vm_pageout_stats_interval == 0) 1595 vm_pageout_stats_interval = 5; 1596 if (vm_pageout_full_stats_interval == 0) 1597 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4; 1598 1599 1600 /* 1601 * Set maximum free per pass 1602 */ 1603 if (vm_pageout_stats_free_max == 0) 1604 vm_pageout_stats_free_max = 5; 1605 1606 swap_pager_swap_init(); 1607 pass = 0; 1608 1609 /* 1610 * The pageout daemon is never done, so loop forever. 1611 */ 1612 while (TRUE) { 1613 int error; 1614 1615 /* 1616 * Wait for an action request. If we timeout check to 1617 * see if paging is needed (in case the normal wakeup 1618 * code raced us). 1619 */ 1620 if (vm_pages_needed == 0) { 1621 error = tsleep(&vm_pages_needed, 1622 0, "psleep", 1623 vm_pageout_stats_interval * hz); 1624 if (error && 1625 vm_paging_needed() == 0 && 1626 vm_pages_needed == 0) { 1627 vm_pageout_page_stats(); 1628 continue; 1629 } 1630 vm_pages_needed = 1; 1631 } 1632 1633 mycpu->gd_cnt.v_pdwakeups++; 1634 1635 /* 1636 * Scan for pageout. Try to avoid thrashing the system 1637 * with activity. 1638 */ 1639 inactive_shortage = vm_pageout_scan(pass); 1640 if (inactive_shortage > 0) { 1641 ++pass; 1642 if (swap_pager_full) { 1643 /* 1644 * Running out of memory, catastrophic back-off 1645 * to one-second intervals. 1646 */ 1647 tsleep(&vm_pages_needed, 0, "pdelay", hz); 1648 } else if (pass < 10 && vm_pages_needed > 1) { 1649 /* 1650 * Normal operation, additional processes 1651 * have already kicked us. Retry immediately. 1652 */ 1653 } else if (pass < 10) { 1654 /* 1655 * Normal operation, fewer processes. Delay 1656 * a bit but allow wakeups. 1657 */ 1658 vm_pages_needed = 0; 1659 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10); 1660 vm_pages_needed = 1; 1661 } else { 1662 /* 1663 * We've taken too many passes, forced delay. 1664 */ 1665 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10); 1666 } 1667 } else { 1668 /* 1669 * Interlocked wakeup of waiters (non-optional) 1670 */ 1671 pass = 0; 1672 if (vm_pages_needed && !vm_page_count_min(0)) { 1673 wakeup(&vmstats.v_free_count); 1674 vm_pages_needed = 0; 1675 } 1676 } 1677 } 1678 } 1679 1680 static struct kproc_desc page_kp = { 1681 "pagedaemon", 1682 vm_pageout_thread, 1683 &pagethread 1684 }; 1685 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp) 1686 1687 1688 /* 1689 * Called after allocating a page out of the cache or free queue 1690 * to possibly wake the pagedaemon up to replentish our supply. 1691 * 1692 * We try to generate some hysteresis by waking the pagedaemon up 1693 * when our free+cache pages go below the free_min+cache_min level. 1694 * The pagedaemon tries to get the count back up to at least the 1695 * minimum, and through to the target level if possible. 1696 * 1697 * If the pagedaemon is already active bump vm_pages_needed as a hint 1698 * that there are even more requests pending. 1699 * 1700 * SMP races ok? 1701 * No requirements. 1702 */ 1703 void 1704 pagedaemon_wakeup(void) 1705 { 1706 if (vm_paging_needed() && curthread != pagethread) { 1707 if (vm_pages_needed == 0) { 1708 vm_pages_needed = 1; /* SMP race ok */ 1709 wakeup(&vm_pages_needed); 1710 } else if (vm_page_count_min(0)) { 1711 ++vm_pages_needed; /* SMP race ok */ 1712 } 1713 } 1714 } 1715 1716 #if !defined(NO_SWAPPING) 1717 1718 /* 1719 * SMP races ok? 1720 * No requirements. 1721 */ 1722 static void 1723 vm_req_vmdaemon(void) 1724 { 1725 static int lastrun = 0; 1726 1727 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 1728 wakeup(&vm_daemon_needed); 1729 lastrun = ticks; 1730 } 1731 } 1732 1733 static int vm_daemon_callback(struct proc *p, void *data __unused); 1734 1735 /* 1736 * No requirements. 1737 */ 1738 static void 1739 vm_daemon(void) 1740 { 1741 /* 1742 * Permanently hold vm_token. 1743 */ 1744 lwkt_gettoken(&vm_token); 1745 1746 while (TRUE) { 1747 tsleep(&vm_daemon_needed, 0, "psleep", 0); 1748 if (vm_pageout_req_swapout) { 1749 swapout_procs(vm_pageout_req_swapout); 1750 vm_pageout_req_swapout = 0; 1751 } 1752 /* 1753 * scan the processes for exceeding their rlimits or if 1754 * process is swapped out -- deactivate pages 1755 */ 1756 allproc_scan(vm_daemon_callback, NULL); 1757 } 1758 } 1759 1760 /* 1761 * Caller must hold vm_token and proc_token. 1762 */ 1763 static int 1764 vm_daemon_callback(struct proc *p, void *data __unused) 1765 { 1766 vm_pindex_t limit, size; 1767 1768 /* 1769 * if this is a system process or if we have already 1770 * looked at this process, skip it. 1771 */ 1772 if (p->p_flag & (P_SYSTEM | P_WEXIT)) 1773 return (0); 1774 1775 /* 1776 * if the process is in a non-running type state, 1777 * don't touch it. 1778 */ 1779 if (p->p_stat != SACTIVE && p->p_stat != SSTOP) 1780 return (0); 1781 1782 /* 1783 * get a limit 1784 */ 1785 limit = OFF_TO_IDX(qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur, 1786 p->p_rlimit[RLIMIT_RSS].rlim_max)); 1787 1788 /* 1789 * let processes that are swapped out really be 1790 * swapped out. Set the limit to nothing to get as 1791 * many pages out to swap as possible. 1792 */ 1793 if (p->p_flag & P_SWAPPEDOUT) 1794 limit = 0; 1795 1796 size = vmspace_resident_count(p->p_vmspace); 1797 if (limit >= 0 && size >= limit) { 1798 vm_pageout_map_deactivate_pages( 1799 &p->p_vmspace->vm_map, limit); 1800 } 1801 return (0); 1802 } 1803 1804 #endif 1805