1 /* 2 * Copyright (c) 1991 Regents of the University of California. 3 * All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * The Mach Operating System project at Carnegie-Mellon University. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91 41 * 42 * 43 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 44 * All rights reserved. 45 * 46 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 47 * 48 * Permission to use, copy, modify and distribute this software and 49 * its documentation is hereby granted, provided that both the copyright 50 * notice and this permission notice appear in all copies of the 51 * software, derivative works or modified versions, and any portions 52 * thereof, and that both notices appear in supporting documentation. 53 * 54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 57 * 58 * Carnegie Mellon requests users of this software to return to 59 * 60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 61 * School of Computer Science 62 * Carnegie Mellon University 63 * Pittsburgh PA 15213-3890 64 * 65 * any improvements or extensions that they make and grant Carnegie the 66 * rights to redistribute these changes. 67 * 68 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $ 69 * $DragonFly: src/sys/vm/vm_pageout.c,v 1.36 2008/07/01 02:02:56 dillon Exp $ 70 */ 71 72 /* 73 * The proverbial page-out daemon. 74 */ 75 76 #include "opt_vm.h" 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/proc.h> 81 #include <sys/kthread.h> 82 #include <sys/resourcevar.h> 83 #include <sys/signalvar.h> 84 #include <sys/vnode.h> 85 #include <sys/vmmeter.h> 86 #include <sys/sysctl.h> 87 88 #include <vm/vm.h> 89 #include <vm/vm_param.h> 90 #include <sys/lock.h> 91 #include <vm/vm_object.h> 92 #include <vm/vm_page.h> 93 #include <vm/vm_map.h> 94 #include <vm/vm_pageout.h> 95 #include <vm/vm_pager.h> 96 #include <vm/swap_pager.h> 97 #include <vm/vm_extern.h> 98 99 #include <sys/thread2.h> 100 #include <vm/vm_page2.h> 101 102 /* 103 * System initialization 104 */ 105 106 /* the kernel process "vm_pageout"*/ 107 static void vm_pageout (void); 108 static int vm_pageout_clean (vm_page_t); 109 static int vm_pageout_scan (int pass); 110 static int vm_pageout_free_page_calc (vm_size_t count); 111 struct thread *pagethread; 112 113 static struct kproc_desc page_kp = { 114 "pagedaemon", 115 vm_pageout, 116 &pagethread 117 }; 118 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp) 119 120 #if !defined(NO_SWAPPING) 121 /* the kernel process "vm_daemon"*/ 122 static void vm_daemon (void); 123 static struct thread *vmthread; 124 125 static struct kproc_desc vm_kp = { 126 "vmdaemon", 127 vm_daemon, 128 &vmthread 129 }; 130 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp) 131 #endif 132 133 134 int vm_pages_needed=0; /* Event on which pageout daemon sleeps */ 135 int vm_pageout_deficit=0; /* Estimated number of pages deficit */ 136 int vm_pageout_pages_needed=0; /* flag saying that the pageout daemon needs pages */ 137 138 #if !defined(NO_SWAPPING) 139 static int vm_pageout_req_swapout; /* XXX */ 140 static int vm_daemon_needed; 141 #endif 142 static int vm_max_launder = 32; 143 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0; 144 static int vm_pageout_full_stats_interval = 0; 145 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0; 146 static int defer_swap_pageouts=0; 147 static int disable_swap_pageouts=0; 148 149 #if defined(NO_SWAPPING) 150 static int vm_swap_enabled=0; 151 static int vm_swap_idle_enabled=0; 152 #else 153 static int vm_swap_enabled=1; 154 static int vm_swap_idle_enabled=0; 155 #endif 156 157 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm, 158 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt"); 159 160 SYSCTL_INT(_vm, OID_AUTO, max_launder, 161 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout"); 162 163 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max, 164 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length"); 165 166 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval, 167 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan"); 168 169 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval, 170 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan"); 171 172 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max, 173 CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented"); 174 175 #if defined(NO_SWAPPING) 176 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 177 CTLFLAG_RD, &vm_swap_enabled, 0, ""); 178 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 179 CTLFLAG_RD, &vm_swap_idle_enabled, 0, ""); 180 #else 181 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, 182 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); 183 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, 184 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); 185 #endif 186 187 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts, 188 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem"); 189 190 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, 191 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); 192 193 static int pageout_lock_miss; 194 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, 195 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); 196 197 int vm_load; 198 SYSCTL_INT(_vm, OID_AUTO, vm_load, 199 CTLFLAG_RD, &vm_load, 0, "load on the VM system"); 200 int vm_load_enable = 1; 201 SYSCTL_INT(_vm, OID_AUTO, vm_load_enable, 202 CTLFLAG_RW, &vm_load_enable, 0, "enable vm_load rate limiting"); 203 #ifdef INVARIANTS 204 int vm_load_debug; 205 SYSCTL_INT(_vm, OID_AUTO, vm_load_debug, 206 CTLFLAG_RW, &vm_load_debug, 0, "debug vm_load"); 207 #endif 208 209 #define VM_PAGEOUT_PAGE_COUNT 16 210 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; 211 212 int vm_page_max_wired; /* XXX max # of wired pages system-wide */ 213 214 #if !defined(NO_SWAPPING) 215 typedef void freeer_fcn_t (vm_map_t, vm_object_t, vm_pindex_t, int); 216 static void vm_pageout_map_deactivate_pages (vm_map_t, vm_pindex_t); 217 static freeer_fcn_t vm_pageout_object_deactivate_pages; 218 static void vm_req_vmdaemon (void); 219 #endif 220 static void vm_pageout_page_stats(void); 221 222 /* 223 * Update vm_load to slow down faulting processes. 224 */ 225 void 226 vm_fault_ratecheck(void) 227 { 228 if (vm_pages_needed) { 229 if (vm_load < 1000) 230 ++vm_load; 231 } else { 232 if (vm_load > 0) 233 --vm_load; 234 } 235 } 236 237 /* 238 * vm_pageout_clean: 239 * 240 * Clean the page and remove it from the laundry. The page must not be 241 * busy on-call. 242 * 243 * We set the busy bit to cause potential page faults on this page to 244 * block. Note the careful timing, however, the busy bit isn't set till 245 * late and we cannot do anything that will mess with the page. 246 */ 247 248 static int 249 vm_pageout_clean(vm_page_t m) 250 { 251 vm_object_t object; 252 vm_page_t mc[2*vm_pageout_page_count]; 253 int pageout_count; 254 int ib, is, page_base; 255 vm_pindex_t pindex = m->pindex; 256 257 object = m->object; 258 259 /* 260 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP 261 * with the new swapper, but we could have serious problems paging 262 * out other object types if there is insufficient memory. 263 * 264 * Unfortunately, checking free memory here is far too late, so the 265 * check has been moved up a procedural level. 266 */ 267 268 /* 269 * Don't mess with the page if it's busy, held, or special 270 */ 271 if ((m->hold_count != 0) || 272 ((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) { 273 return 0; 274 } 275 276 mc[vm_pageout_page_count] = m; 277 pageout_count = 1; 278 page_base = vm_pageout_page_count; 279 ib = 1; 280 is = 1; 281 282 /* 283 * Scan object for clusterable pages. 284 * 285 * We can cluster ONLY if: ->> the page is NOT 286 * clean, wired, busy, held, or mapped into a 287 * buffer, and one of the following: 288 * 1) The page is inactive, or a seldom used 289 * active page. 290 * -or- 291 * 2) we force the issue. 292 * 293 * During heavy mmap/modification loads the pageout 294 * daemon can really fragment the underlying file 295 * due to flushing pages out of order and not trying 296 * align the clusters (which leave sporatic out-of-order 297 * holes). To solve this problem we do the reverse scan 298 * first and attempt to align our cluster, then do a 299 * forward scan if room remains. 300 */ 301 302 more: 303 while (ib && pageout_count < vm_pageout_page_count) { 304 vm_page_t p; 305 306 if (ib > pindex) { 307 ib = 0; 308 break; 309 } 310 311 if ((p = vm_page_lookup(object, pindex - ib)) == NULL) { 312 ib = 0; 313 break; 314 } 315 if (((p->queue - p->pc) == PQ_CACHE) || 316 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) { 317 ib = 0; 318 break; 319 } 320 vm_page_test_dirty(p); 321 if ((p->dirty & p->valid) == 0 || 322 p->queue != PQ_INACTIVE || 323 p->wire_count != 0 || /* may be held by buf cache */ 324 p->hold_count != 0) { /* may be undergoing I/O */ 325 ib = 0; 326 break; 327 } 328 mc[--page_base] = p; 329 ++pageout_count; 330 ++ib; 331 /* 332 * alignment boundry, stop here and switch directions. Do 333 * not clear ib. 334 */ 335 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) 336 break; 337 } 338 339 while (pageout_count < vm_pageout_page_count && 340 pindex + is < object->size) { 341 vm_page_t p; 342 343 if ((p = vm_page_lookup(object, pindex + is)) == NULL) 344 break; 345 if (((p->queue - p->pc) == PQ_CACHE) || 346 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) { 347 break; 348 } 349 vm_page_test_dirty(p); 350 if ((p->dirty & p->valid) == 0 || 351 p->queue != PQ_INACTIVE || 352 p->wire_count != 0 || /* may be held by buf cache */ 353 p->hold_count != 0) { /* may be undergoing I/O */ 354 break; 355 } 356 mc[page_base + pageout_count] = p; 357 ++pageout_count; 358 ++is; 359 } 360 361 /* 362 * If we exhausted our forward scan, continue with the reverse scan 363 * when possible, even past a page boundry. This catches boundry 364 * conditions. 365 */ 366 if (ib && pageout_count < vm_pageout_page_count) 367 goto more; 368 369 /* 370 * we allow reads during pageouts... 371 */ 372 return vm_pageout_flush(&mc[page_base], pageout_count, 0); 373 } 374 375 /* 376 * vm_pageout_flush() - launder the given pages 377 * 378 * The given pages are laundered. Note that we setup for the start of 379 * I/O ( i.e. busy the page ), mark it read-only, and bump the object 380 * reference count all in here rather then in the parent. If we want 381 * the parent to do more sophisticated things we may have to change 382 * the ordering. 383 */ 384 int 385 vm_pageout_flush(vm_page_t *mc, int count, int flags) 386 { 387 vm_object_t object; 388 int pageout_status[count]; 389 int numpagedout = 0; 390 int i; 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 vm_object_pip_wakeup(object); 467 vm_page_io_finish(mt); 468 if (vm_page_count_severe()) 469 vm_page_deactivate(mt); 470 #if 0 471 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt)) 472 vm_page_protect(mt, VM_PROT_READ); 473 #endif 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 object and map must be locked. 489 */ 490 static int vm_pageout_object_deactivate_pages_callback(vm_page_t, void *); 491 492 static void 493 vm_pageout_object_deactivate_pages(vm_map_t map, vm_object_t object, 494 vm_pindex_t desired, int map_remove_only) 495 { 496 struct rb_vm_page_scan_info info; 497 int remove_mode; 498 499 if (object->type == OBJT_DEVICE || object->type == OBJT_PHYS) 500 return; 501 502 while (object) { 503 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 504 return; 505 if (object->paging_in_progress) 506 return; 507 508 remove_mode = map_remove_only; 509 if (object->shadow_count > 1) 510 remove_mode = 1; 511 512 /* 513 * scan the objects entire memory queue. spl protection is 514 * required to avoid an interrupt unbusy/free race against 515 * our busy check. 516 */ 517 crit_enter(); 518 info.limit = remove_mode; 519 info.map = map; 520 info.desired = desired; 521 vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL, 522 vm_pageout_object_deactivate_pages_callback, 523 &info 524 ); 525 crit_exit(); 526 object = object->backing_object; 527 } 528 } 529 530 static int 531 vm_pageout_object_deactivate_pages_callback(vm_page_t p, void *data) 532 { 533 struct rb_vm_page_scan_info *info = data; 534 int actcount; 535 536 if (pmap_resident_count(vm_map_pmap(info->map)) <= info->desired) { 537 return(-1); 538 } 539 mycpu->gd_cnt.v_pdpages++; 540 if (p->wire_count != 0 || p->hold_count != 0 || p->busy != 0 || 541 (p->flags & (PG_BUSY|PG_UNMANAGED)) || 542 !pmap_page_exists_quick(vm_map_pmap(info->map), p)) { 543 return(0); 544 } 545 546 actcount = pmap_ts_referenced(p); 547 if (actcount) { 548 vm_page_flag_set(p, PG_REFERENCED); 549 } else if (p->flags & PG_REFERENCED) { 550 actcount = 1; 551 } 552 553 if ((p->queue != PQ_ACTIVE) && 554 (p->flags & PG_REFERENCED)) { 555 vm_page_activate(p); 556 p->act_count += actcount; 557 vm_page_flag_clear(p, PG_REFERENCED); 558 } else if (p->queue == PQ_ACTIVE) { 559 if ((p->flags & PG_REFERENCED) == 0) { 560 p->act_count -= min(p->act_count, ACT_DECLINE); 561 if (!info->limit && (vm_pageout_algorithm || (p->act_count == 0))) { 562 vm_page_busy(p); 563 vm_page_protect(p, VM_PROT_NONE); 564 vm_page_wakeup(p); 565 vm_page_deactivate(p); 566 } else { 567 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 568 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 569 } 570 } else { 571 vm_page_activate(p); 572 vm_page_flag_clear(p, PG_REFERENCED); 573 if (p->act_count < (ACT_MAX - ACT_ADVANCE)) 574 p->act_count += ACT_ADVANCE; 575 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 576 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq); 577 } 578 } else if (p->queue == PQ_INACTIVE) { 579 vm_page_busy(p); 580 vm_page_protect(p, VM_PROT_NONE); 581 vm_page_wakeup(p); 582 } 583 return(0); 584 } 585 586 /* 587 * deactivate some number of pages in a map, try to do it fairly, but 588 * that is really hard to do. 589 */ 590 static void 591 vm_pageout_map_deactivate_pages(vm_map_t map, vm_pindex_t desired) 592 { 593 vm_map_entry_t tmpe; 594 vm_object_t obj, bigobj; 595 int nothingwired; 596 597 if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT)) { 598 return; 599 } 600 601 bigobj = NULL; 602 nothingwired = TRUE; 603 604 /* 605 * first, search out the biggest object, and try to free pages from 606 * that. 607 */ 608 tmpe = map->header.next; 609 while (tmpe != &map->header) { 610 switch(tmpe->maptype) { 611 case VM_MAPTYPE_NORMAL: 612 case VM_MAPTYPE_VPAGETABLE: 613 obj = tmpe->object.vm_object; 614 if ((obj != NULL) && (obj->shadow_count <= 1) && 615 ((bigobj == NULL) || 616 (bigobj->resident_page_count < obj->resident_page_count))) { 617 bigobj = obj; 618 } 619 break; 620 default: 621 break; 622 } 623 if (tmpe->wired_count > 0) 624 nothingwired = FALSE; 625 tmpe = tmpe->next; 626 } 627 628 if (bigobj) 629 vm_pageout_object_deactivate_pages(map, bigobj, desired, 0); 630 631 /* 632 * Next, hunt around for other pages to deactivate. We actually 633 * do this search sort of wrong -- .text first is not the best idea. 634 */ 635 tmpe = map->header.next; 636 while (tmpe != &map->header) { 637 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 638 break; 639 switch(tmpe->maptype) { 640 case VM_MAPTYPE_NORMAL: 641 case VM_MAPTYPE_VPAGETABLE: 642 obj = tmpe->object.vm_object; 643 if (obj) 644 vm_pageout_object_deactivate_pages(map, obj, desired, 0); 645 break; 646 default: 647 break; 648 } 649 tmpe = tmpe->next; 650 }; 651 652 /* 653 * Remove all mappings if a process is swapped out, this will free page 654 * table pages. 655 */ 656 if (desired == 0 && nothingwired) 657 pmap_remove(vm_map_pmap(map), 658 VM_MIN_USER_ADDRESS, VM_MAX_USER_ADDRESS); 659 vm_map_unlock(map); 660 } 661 #endif 662 663 /* 664 * Don't try to be fancy - being fancy can lead to vnode deadlocks. We 665 * only do it for OBJT_DEFAULT and OBJT_SWAP objects which we know can 666 * be trivially freed. 667 */ 668 void 669 vm_pageout_page_free(vm_page_t m) 670 { 671 vm_object_t object = m->object; 672 int type = object->type; 673 674 if (type == OBJT_SWAP || type == OBJT_DEFAULT) 675 vm_object_reference(object); 676 vm_page_busy(m); 677 vm_page_protect(m, VM_PROT_NONE); 678 vm_page_free(m); 679 if (type == OBJT_SWAP || type == OBJT_DEFAULT) 680 vm_object_deallocate(object); 681 } 682 683 /* 684 * vm_pageout_scan does the dirty work for the pageout daemon. 685 */ 686 struct vm_pageout_scan_info { 687 struct proc *bigproc; 688 vm_offset_t bigsize; 689 }; 690 691 static int vm_pageout_scan_callback(struct proc *p, void *data); 692 693 static int 694 vm_pageout_scan(int pass) 695 { 696 struct vm_pageout_scan_info info; 697 vm_page_t m, next; 698 struct vm_page marker; 699 struct vnode *vpfailed; /* warning, allowed to be stale */ 700 int maxscan, pcount; 701 int recycle_count; 702 int inactive_shortage, active_shortage; 703 int inactive_original_shortage; 704 vm_object_t object; 705 int actcount; 706 int vnodes_skipped = 0; 707 int maxlaunder; 708 709 /* 710 * Do whatever cleanup that the pmap code can. 711 */ 712 pmap_collect(); 713 714 /* 715 * Calculate our target for the number of free+cache pages we 716 * want to get to. This is higher then the number that causes 717 * allocations to stall (severe) in order to provide hysteresis, 718 * and if we don't make it all the way but get to the minimum 719 * we're happy. 720 */ 721 inactive_shortage = vm_paging_target() + vm_pageout_deficit; 722 inactive_original_shortage = inactive_shortage; 723 vm_pageout_deficit = 0; 724 725 /* 726 * Initialize our marker 727 */ 728 bzero(&marker, sizeof(marker)); 729 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER; 730 marker.queue = PQ_INACTIVE; 731 marker.wire_count = 1; 732 733 /* 734 * Start scanning the inactive queue for pages we can move to the 735 * cache or free. The scan will stop when the target is reached or 736 * we have scanned the entire inactive queue. Note that m->act_count 737 * is not used to form decisions for the inactive queue, only for the 738 * active queue. 739 * 740 * maxlaunder limits the number of dirty pages we flush per scan. 741 * For most systems a smaller value (16 or 32) is more robust under 742 * extreme memory and disk pressure because any unnecessary writes 743 * to disk can result in extreme performance degredation. However, 744 * systems with excessive dirty pages (especially when MAP_NOSYNC is 745 * used) will die horribly with limited laundering. If the pageout 746 * daemon cannot clean enough pages in the first pass, we let it go 747 * all out in succeeding passes. 748 */ 749 if ((maxlaunder = vm_max_launder) <= 1) 750 maxlaunder = 1; 751 if (pass) 752 maxlaunder = 10000; 753 754 /* 755 * We will generally be in a critical section throughout the 756 * scan, but we can release it temporarily when we are sitting on a 757 * non-busy page without fear. this is required to prevent an 758 * interrupt from unbusying or freeing a page prior to our busy 759 * check, leaving us on the wrong queue or checking the wrong 760 * page. 761 */ 762 crit_enter(); 763 rescan0: 764 vpfailed = NULL; 765 maxscan = vmstats.v_inactive_count; 766 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl); 767 m != NULL && maxscan-- > 0 && inactive_shortage > 0; 768 m = next 769 ) { 770 mycpu->gd_cnt.v_pdpages++; 771 772 /* 773 * Give interrupts a chance 774 */ 775 crit_exit(); 776 crit_enter(); 777 778 /* 779 * It's easier for some of the conditions below to just loop 780 * and catch queue changes here rather then check everywhere 781 * else. 782 */ 783 if (m->queue != PQ_INACTIVE) 784 goto rescan0; 785 next = TAILQ_NEXT(m, pageq); 786 787 /* 788 * skip marker pages 789 */ 790 if (m->flags & PG_MARKER) 791 continue; 792 793 /* 794 * A held page may be undergoing I/O, so skip it. 795 */ 796 if (m->hold_count) { 797 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 798 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 799 ++vm_swapcache_inactive_heuristic; 800 continue; 801 } 802 803 /* 804 * Dont mess with busy pages, keep in the front of the 805 * queue, most likely are being paged out. 806 */ 807 if (m->busy || (m->flags & PG_BUSY)) { 808 continue; 809 } 810 811 if (m->object->ref_count == 0) { 812 /* 813 * If the object is not being used, we ignore previous 814 * references. 815 */ 816 vm_page_flag_clear(m, PG_REFERENCED); 817 pmap_clear_reference(m); 818 819 } else if (((m->flags & PG_REFERENCED) == 0) && 820 (actcount = pmap_ts_referenced(m))) { 821 /* 822 * Otherwise, if the page has been referenced while 823 * in the inactive queue, we bump the "activation 824 * count" upwards, making it less likely that the 825 * page will be added back to the inactive queue 826 * prematurely again. Here we check the page tables 827 * (or emulated bits, if any), given the upper level 828 * VM system not knowing anything about existing 829 * references. 830 */ 831 vm_page_activate(m); 832 m->act_count += (actcount + ACT_ADVANCE); 833 continue; 834 } 835 836 /* 837 * If the upper level VM system knows about any page 838 * references, we activate the page. We also set the 839 * "activation count" higher than normal so that we will less 840 * likely place pages back onto the inactive queue again. 841 */ 842 if ((m->flags & PG_REFERENCED) != 0) { 843 vm_page_flag_clear(m, PG_REFERENCED); 844 actcount = pmap_ts_referenced(m); 845 vm_page_activate(m); 846 m->act_count += (actcount + ACT_ADVANCE + 1); 847 continue; 848 } 849 850 /* 851 * If the upper level VM system doesn't know anything about 852 * the page being dirty, we have to check for it again. As 853 * far as the VM code knows, any partially dirty pages are 854 * fully dirty. 855 * 856 * Pages marked PG_WRITEABLE may be mapped into the user 857 * address space of a process running on another cpu. A 858 * user process (without holding the MP lock) running on 859 * another cpu may be able to touch the page while we are 860 * trying to remove it. vm_page_cache() will handle this 861 * case for us. 862 */ 863 if (m->dirty == 0) { 864 vm_page_test_dirty(m); 865 } else { 866 vm_page_dirty(m); 867 } 868 869 if (m->valid == 0) { 870 /* 871 * Invalid pages can be easily freed 872 */ 873 vm_pageout_page_free(m); 874 mycpu->gd_cnt.v_dfree++; 875 --inactive_shortage; 876 } else if (m->dirty == 0) { 877 /* 878 * Clean pages can be placed onto the cache queue. 879 * This effectively frees them. 880 */ 881 vm_page_cache(m); 882 --inactive_shortage; 883 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) { 884 /* 885 * Dirty pages need to be paged out, but flushing 886 * a page is extremely expensive verses freeing 887 * a clean page. Rather then artificially limiting 888 * the number of pages we can flush, we instead give 889 * dirty pages extra priority on the inactive queue 890 * by forcing them to be cycled through the queue 891 * twice before being flushed, after which the 892 * (now clean) page will cycle through once more 893 * before being freed. This significantly extends 894 * the thrash point for a heavily loaded machine. 895 */ 896 vm_page_flag_set(m, PG_WINATCFLS); 897 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 898 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 899 ++vm_swapcache_inactive_heuristic; 900 } else if (maxlaunder > 0) { 901 /* 902 * We always want to try to flush some dirty pages if 903 * we encounter them, to keep the system stable. 904 * Normally this number is small, but under extreme 905 * pressure where there are insufficient clean pages 906 * on the inactive queue, we may have to go all out. 907 */ 908 int swap_pageouts_ok; 909 struct vnode *vp = NULL; 910 911 object = m->object; 912 913 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) { 914 swap_pageouts_ok = 1; 915 } else { 916 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts); 917 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts && 918 vm_page_count_min(0)); 919 920 } 921 922 /* 923 * We don't bother paging objects that are "dead". 924 * Those objects are in a "rundown" state. 925 */ 926 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) { 927 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 928 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 929 ++vm_swapcache_inactive_heuristic; 930 continue; 931 } 932 933 /* 934 * The object is already known NOT to be dead. It 935 * is possible for the vget() to block the whole 936 * pageout daemon, but the new low-memory handling 937 * code should prevent it. 938 * 939 * The previous code skipped locked vnodes and, worse, 940 * reordered pages in the queue. This results in 941 * completely non-deterministic operation because, 942 * quite often, a vm_fault has initiated an I/O and 943 * is holding a locked vnode at just the point where 944 * the pageout daemon is woken up. 945 * 946 * We can't wait forever for the vnode lock, we might 947 * deadlock due to a vn_read() getting stuck in 948 * vm_wait while holding this vnode. We skip the 949 * vnode if we can't get it in a reasonable amount 950 * of time. 951 * 952 * vpfailed is used to (try to) avoid the case where 953 * a large number of pages are associated with a 954 * locked vnode, which could cause the pageout daemon 955 * to stall for an excessive amount of time. 956 */ 957 if (object->type == OBJT_VNODE) { 958 int flags; 959 960 vp = object->handle; 961 flags = LK_EXCLUSIVE | LK_NOOBJ; 962 if (vp == vpfailed) 963 flags |= LK_NOWAIT; 964 else 965 flags |= LK_TIMELOCK; 966 if (vget(vp, flags) != 0) { 967 vpfailed = vp; 968 ++pageout_lock_miss; 969 if (object->flags & OBJ_MIGHTBEDIRTY) 970 vnodes_skipped++; 971 continue; 972 } 973 974 /* 975 * The page might have been moved to another 976 * queue during potential blocking in vget() 977 * above. The page might have been freed and 978 * reused for another vnode. The object might 979 * have been reused for another vnode. 980 */ 981 if (m->queue != PQ_INACTIVE || 982 m->object != object || 983 object->handle != vp) { 984 if (object->flags & OBJ_MIGHTBEDIRTY) 985 vnodes_skipped++; 986 vput(vp); 987 continue; 988 } 989 990 /* 991 * The page may have been busied during the 992 * blocking in vput(); We don't move the 993 * page back onto the end of the queue so that 994 * statistics are more correct if we don't. 995 */ 996 if (m->busy || (m->flags & PG_BUSY)) { 997 vput(vp); 998 continue; 999 } 1000 1001 /* 1002 * If the page has become held it might 1003 * be undergoing I/O, so skip it 1004 */ 1005 if (m->hold_count) { 1006 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 1007 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); 1008 ++vm_swapcache_inactive_heuristic; 1009 if (object->flags & OBJ_MIGHTBEDIRTY) 1010 vnodes_skipped++; 1011 vput(vp); 1012 continue; 1013 } 1014 } 1015 1016 /* 1017 * If a page is dirty, then it is either being washed 1018 * (but not yet cleaned) or it is still in the 1019 * laundry. If it is still in the laundry, then we 1020 * start the cleaning operation. 1021 * 1022 * This operation may cluster, invalidating the 'next' 1023 * pointer. To prevent an inordinate number of 1024 * restarts we use our marker to remember our place. 1025 * 1026 * decrement inactive_shortage on success to account 1027 * for the (future) cleaned page. Otherwise we 1028 * could wind up laundering or cleaning too many 1029 * pages. 1030 */ 1031 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq); 1032 if (vm_pageout_clean(m) != 0) { 1033 --inactive_shortage; 1034 --maxlaunder; 1035 } 1036 next = TAILQ_NEXT(&marker, pageq); 1037 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq); 1038 if (vp != NULL) 1039 vput(vp); 1040 } 1041 } 1042 1043 /* 1044 * We want to move pages from the active queue to the inactive 1045 * queue to get the inactive queue to the inactive target. If 1046 * we still have a page shortage from above we try to directly free 1047 * clean pages instead of moving them. 1048 * 1049 * If we do still have a shortage we keep track of the number of 1050 * pages we free or cache (recycle_count) as a measure of thrashing 1051 * between the active and inactive queues. 1052 * 1053 * If we were able to completely satisfy the free+cache targets 1054 * from the inactive pool we limit the number of pages we move 1055 * from the active pool to the inactive pool to 2x the pages we 1056 * had removed from the inactive pool (with a minimum of 1/5 the 1057 * inactive target). If we were not able to completely satisfy 1058 * the free+cache targets we go for the whole target aggressively. 1059 * 1060 * NOTE: Both variables can end up negative. 1061 * NOTE: We are still in a critical section. 1062 */ 1063 active_shortage = vmstats.v_inactive_target - vmstats.v_inactive_count; 1064 if (inactive_original_shortage < vmstats.v_inactive_target / 10) 1065 inactive_original_shortage = vmstats.v_inactive_target / 10; 1066 if (inactive_shortage <= 0 && 1067 active_shortage > inactive_original_shortage * 2) { 1068 active_shortage = inactive_original_shortage * 2; 1069 } 1070 1071 pcount = vmstats.v_active_count; 1072 recycle_count = 0; 1073 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); 1074 1075 while ((m != NULL) && (pcount-- > 0) && 1076 (inactive_shortage > 0 || active_shortage > 0) 1077 ) { 1078 /* 1079 * Give interrupts a chance. 1080 */ 1081 crit_exit(); 1082 crit_enter(); 1083 1084 /* 1085 * If the page was ripped out from under us, just stop. 1086 */ 1087 if (m->queue != PQ_ACTIVE) 1088 break; 1089 next = TAILQ_NEXT(m, pageq); 1090 1091 /* 1092 * Don't deactivate pages that are busy. 1093 */ 1094 if ((m->busy != 0) || 1095 (m->flags & PG_BUSY) || 1096 (m->hold_count != 0)) { 1097 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1098 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1099 m = next; 1100 continue; 1101 } 1102 1103 /* 1104 * The count for pagedaemon pages is done after checking the 1105 * page for eligibility... 1106 */ 1107 mycpu->gd_cnt.v_pdpages++; 1108 1109 /* 1110 * Check to see "how much" the page has been used and clear 1111 * the tracking access bits. If the object has no references 1112 * don't bother paying the expense. 1113 */ 1114 actcount = 0; 1115 if (m->object->ref_count != 0) { 1116 if (m->flags & PG_REFERENCED) 1117 ++actcount; 1118 actcount += pmap_ts_referenced(m); 1119 if (actcount) { 1120 m->act_count += ACT_ADVANCE + actcount; 1121 if (m->act_count > ACT_MAX) 1122 m->act_count = ACT_MAX; 1123 } 1124 } 1125 vm_page_flag_clear(m, PG_REFERENCED); 1126 1127 /* 1128 * actcount is only valid if the object ref_count is non-zero. 1129 */ 1130 if (actcount && m->object->ref_count != 0) { 1131 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1132 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1133 } else { 1134 m->act_count -= min(m->act_count, ACT_DECLINE); 1135 if (vm_pageout_algorithm || 1136 m->object->ref_count == 0 || 1137 m->act_count < pass + 1 1138 ) { 1139 /* 1140 * Deactivate the page. If we had a 1141 * shortage from our inactive scan try to 1142 * free (cache) the page instead. 1143 * 1144 * Don't just blindly cache the page if 1145 * we do not have a shortage from the 1146 * inactive scan, that could lead to 1147 * gigabytes being moved. 1148 */ 1149 --active_shortage; 1150 if (inactive_shortage > 0 || 1151 m->object->ref_count == 0) { 1152 if (inactive_shortage > 0) 1153 ++recycle_count; 1154 vm_page_busy(m); 1155 vm_page_protect(m, VM_PROT_NONE); 1156 vm_page_wakeup(m); 1157 if (m->dirty == 0 && 1158 inactive_shortage > 0) { 1159 --inactive_shortage; 1160 vm_page_cache(m); 1161 } else { 1162 vm_page_deactivate(m); 1163 } 1164 } else { 1165 vm_page_deactivate(m); 1166 } 1167 } else { 1168 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1169 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1170 } 1171 } 1172 m = next; 1173 } 1174 1175 /* 1176 * We try to maintain some *really* free pages, this allows interrupt 1177 * code to be guaranteed space. Since both cache and free queues 1178 * are considered basically 'free', moving pages from cache to free 1179 * does not effect other calculations. 1180 * 1181 * NOTE: we are still in a critical section. 1182 * 1183 * Pages moved from PQ_CACHE to totally free are not counted in the 1184 * pages_freed counter. 1185 */ 1186 while (vmstats.v_free_count < vmstats.v_free_reserved) { 1187 static int cache_rover = 0; 1188 m = vm_page_list_find(PQ_CACHE, cache_rover, FALSE); 1189 if (m == NULL) 1190 break; 1191 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || 1192 m->busy || 1193 m->hold_count || 1194 m->wire_count) { 1195 #ifdef INVARIANTS 1196 kprintf("Warning: busy page %p found in cache\n", m); 1197 #endif 1198 vm_page_deactivate(m); 1199 continue; 1200 } 1201 KKASSERT((m->flags & PG_MAPPED) == 0); 1202 KKASSERT(m->dirty == 0); 1203 cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK; 1204 vm_pageout_page_free(m); 1205 mycpu->gd_cnt.v_dfree++; 1206 } 1207 1208 crit_exit(); 1209 1210 #if !defined(NO_SWAPPING) 1211 /* 1212 * Idle process swapout -- run once per second. 1213 */ 1214 if (vm_swap_idle_enabled) { 1215 static long lsec; 1216 if (time_second != lsec) { 1217 vm_pageout_req_swapout |= VM_SWAP_IDLE; 1218 vm_req_vmdaemon(); 1219 lsec = time_second; 1220 } 1221 } 1222 #endif 1223 1224 /* 1225 * If we didn't get enough free pages, and we have skipped a vnode 1226 * in a writeable object, wakeup the sync daemon. And kick swapout 1227 * if we did not get enough free pages. 1228 */ 1229 if (vm_paging_target() > 0) { 1230 if (vnodes_skipped && vm_page_count_min(0)) 1231 speedup_syncer(); 1232 #if !defined(NO_SWAPPING) 1233 if (vm_swap_enabled && vm_page_count_target()) { 1234 vm_req_vmdaemon(); 1235 vm_pageout_req_swapout |= VM_SWAP_NORMAL; 1236 } 1237 #endif 1238 } 1239 1240 /* 1241 * Handle catastrophic conditions. Under good conditions we should 1242 * be at the target, well beyond our minimum. If we could not even 1243 * reach our minimum the system is under heavy stress. 1244 * 1245 * Determine whether we have run out of memory. This occurs when 1246 * swap_pager_full is TRUE and the only pages left in the page 1247 * queues are dirty. We will still likely have page shortages. 1248 * 1249 * - swap_pager_full is set if insufficient swap was 1250 * available to satisfy a requested pageout. 1251 * 1252 * - the inactive queue is bloated (4 x size of active queue), 1253 * meaning it is unable to get rid of dirty pages and. 1254 * 1255 * - vm_page_count_min() without counting pages recycled from the 1256 * active queue (recycle_count) means we could not recover 1257 * enough pages to meet bare minimum needs. This test only 1258 * works if the inactive queue is bloated. 1259 * 1260 * - due to a positive inactive_shortage we shifted the remaining 1261 * dirty pages from the active queue to the inactive queue 1262 * trying to find clean ones to free. 1263 */ 1264 if (swap_pager_full && vm_page_count_min(recycle_count)) 1265 kprintf("Warning: system low on memory+swap!\n"); 1266 if (swap_pager_full && vm_page_count_min(recycle_count) && 1267 vmstats.v_inactive_count > vmstats.v_active_count * 4 && 1268 inactive_shortage > 0) { 1269 /* 1270 * Kill something. 1271 */ 1272 info.bigproc = NULL; 1273 info.bigsize = 0; 1274 allproc_scan(vm_pageout_scan_callback, &info); 1275 if (info.bigproc != NULL) { 1276 killproc(info.bigproc, "out of swap space"); 1277 info.bigproc->p_nice = PRIO_MIN; 1278 info.bigproc->p_usched->resetpriority( 1279 FIRST_LWP_IN_PROC(info.bigproc)); 1280 wakeup(&vmstats.v_free_count); 1281 PRELE(info.bigproc); 1282 } 1283 } 1284 return(inactive_shortage); 1285 } 1286 1287 static int 1288 vm_pageout_scan_callback(struct proc *p, void *data) 1289 { 1290 struct vm_pageout_scan_info *info = data; 1291 vm_offset_t size; 1292 1293 /* 1294 * Never kill system processes or init. If we have configured swap 1295 * then try to avoid killing low-numbered pids. 1296 */ 1297 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) || 1298 ((p->p_pid < 48) && (vm_swap_size != 0))) { 1299 return (0); 1300 } 1301 1302 /* 1303 * if the process is in a non-running type state, 1304 * don't touch it. 1305 */ 1306 if (p->p_stat != SACTIVE && p->p_stat != SSTOP) 1307 return (0); 1308 1309 /* 1310 * Get the approximate process size. Note that anonymous pages 1311 * with backing swap will be counted twice, but there should not 1312 * be too many such pages due to the stress the VM system is 1313 * under at this point. 1314 */ 1315 size = vmspace_anonymous_count(p->p_vmspace) + 1316 vmspace_swap_count(p->p_vmspace); 1317 1318 /* 1319 * If the this process is bigger than the biggest one 1320 * remember it. 1321 */ 1322 if (info->bigsize < size) { 1323 if (info->bigproc) 1324 PRELE(info->bigproc); 1325 PHOLD(p); 1326 info->bigproc = p; 1327 info->bigsize = size; 1328 } 1329 return(0); 1330 } 1331 1332 /* 1333 * This routine tries to maintain the pseudo LRU active queue, 1334 * so that during long periods of time where there is no paging, 1335 * that some statistic accumulation still occurs. This code 1336 * helps the situation where paging just starts to occur. 1337 */ 1338 static void 1339 vm_pageout_page_stats(void) 1340 { 1341 vm_page_t m,next; 1342 int pcount,tpcount; /* Number of pages to check */ 1343 static int fullintervalcount = 0; 1344 int page_shortage; 1345 1346 page_shortage = 1347 (vmstats.v_inactive_target + vmstats.v_cache_max + vmstats.v_free_min) - 1348 (vmstats.v_free_count + vmstats.v_inactive_count + vmstats.v_cache_count); 1349 1350 if (page_shortage <= 0) 1351 return; 1352 1353 crit_enter(); 1354 1355 pcount = vmstats.v_active_count; 1356 fullintervalcount += vm_pageout_stats_interval; 1357 if (fullintervalcount < vm_pageout_full_stats_interval) { 1358 tpcount = (vm_pageout_stats_max * vmstats.v_active_count) / vmstats.v_page_count; 1359 if (pcount > tpcount) 1360 pcount = tpcount; 1361 } else { 1362 fullintervalcount = 0; 1363 } 1364 1365 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); 1366 while ((m != NULL) && (pcount-- > 0)) { 1367 int actcount; 1368 1369 if (m->queue != PQ_ACTIVE) { 1370 break; 1371 } 1372 1373 next = TAILQ_NEXT(m, pageq); 1374 /* 1375 * Don't deactivate pages that are busy. 1376 */ 1377 if ((m->busy != 0) || 1378 (m->flags & PG_BUSY) || 1379 (m->hold_count != 0)) { 1380 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1381 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1382 m = next; 1383 continue; 1384 } 1385 1386 actcount = 0; 1387 if (m->flags & PG_REFERENCED) { 1388 vm_page_flag_clear(m, PG_REFERENCED); 1389 actcount += 1; 1390 } 1391 1392 actcount += pmap_ts_referenced(m); 1393 if (actcount) { 1394 m->act_count += ACT_ADVANCE + actcount; 1395 if (m->act_count > ACT_MAX) 1396 m->act_count = ACT_MAX; 1397 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1398 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1399 } else { 1400 if (m->act_count == 0) { 1401 /* 1402 * We turn off page access, so that we have 1403 * more accurate RSS stats. We don't do this 1404 * in the normal page deactivation when the 1405 * system is loaded VM wise, because the 1406 * cost of the large number of page protect 1407 * operations would be higher than the value 1408 * of doing the operation. 1409 */ 1410 vm_page_busy(m); 1411 vm_page_protect(m, VM_PROT_NONE); 1412 vm_page_wakeup(m); 1413 vm_page_deactivate(m); 1414 } else { 1415 m->act_count -= min(m->act_count, ACT_DECLINE); 1416 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1417 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq); 1418 } 1419 } 1420 1421 m = next; 1422 } 1423 crit_exit(); 1424 } 1425 1426 static int 1427 vm_pageout_free_page_calc(vm_size_t count) 1428 { 1429 if (count < vmstats.v_page_count) 1430 return 0; 1431 /* 1432 * free_reserved needs to include enough for the largest swap pager 1433 * structures plus enough for any pv_entry structs when paging. 1434 */ 1435 if (vmstats.v_page_count > 1024) 1436 vmstats.v_free_min = 4 + (vmstats.v_page_count - 1024) / 200; 1437 else 1438 vmstats.v_free_min = 4; 1439 vmstats.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + 1440 vmstats.v_interrupt_free_min; 1441 vmstats.v_free_reserved = vm_pageout_page_count + 1442 vmstats.v_pageout_free_min + (count / 768) + PQ_L2_SIZE; 1443 vmstats.v_free_severe = vmstats.v_free_min / 2; 1444 vmstats.v_free_min += vmstats.v_free_reserved; 1445 vmstats.v_free_severe += vmstats.v_free_reserved; 1446 return 1; 1447 } 1448 1449 1450 /* 1451 * vm_pageout is the high level pageout daemon. 1452 */ 1453 static void 1454 vm_pageout(void) 1455 { 1456 int pass; 1457 int inactive_shortage; 1458 1459 /* 1460 * Initialize some paging parameters. 1461 */ 1462 curthread->td_flags |= TDF_SYSTHREAD; 1463 1464 vmstats.v_interrupt_free_min = 2; 1465 if (vmstats.v_page_count < 2000) 1466 vm_pageout_page_count = 8; 1467 1468 vm_pageout_free_page_calc(vmstats.v_page_count); 1469 1470 /* 1471 * v_free_target and v_cache_min control pageout hysteresis. Note 1472 * that these are more a measure of the VM cache queue hysteresis 1473 * then the VM free queue. Specifically, v_free_target is the 1474 * high water mark (free+cache pages). 1475 * 1476 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the 1477 * low water mark, while v_free_min is the stop. v_cache_min must 1478 * be big enough to handle memory needs while the pageout daemon 1479 * is signalled and run to free more pages. 1480 */ 1481 if (vmstats.v_free_count > 6144) 1482 vmstats.v_free_target = 4 * vmstats.v_free_min + vmstats.v_free_reserved; 1483 else 1484 vmstats.v_free_target = 2 * vmstats.v_free_min + vmstats.v_free_reserved; 1485 1486 /* 1487 * NOTE: With the new buffer cache b_act_count we want the default 1488 * inactive target to be a percentage of available memory. 1489 * 1490 * The inactive target essentially determines the minimum 1491 * number of 'temporary' pages capable of caching one-time-use 1492 * files when the VM system is otherwise full of pages 1493 * belonging to multi-time-use files or active program data. 1494 * 1495 * NOTE: The inactive target is aggressively persued only if the 1496 * inactive queue becomes too small. If the inactive queue 1497 * is large enough to satisfy page movement to free+cache 1498 * then it is repopulated more slowly from the active queue. 1499 * This allows a general inactive_target default to be set. 1500 * 1501 * There is an issue here for processes which sit mostly idle 1502 * 'overnight', such as sshd, tcsh, and X. Any movement from 1503 * the active queue will eventually cause such pages to 1504 * recycle eventually causing a lot of paging in the morning. 1505 * To reduce the incidence of this pages cycled out of the 1506 * buffer cache are moved directly to the inactive queue if 1507 * they were only used once or twice. 1508 * 1509 * The vfs.vm_cycle_point sysctl can be used to adjust this. 1510 * Increasing the value (up to 64) increases the number of 1511 * buffer recyclements which go directly to the inactive queue. 1512 */ 1513 if (vmstats.v_free_count > 2048) { 1514 vmstats.v_cache_min = vmstats.v_free_target; 1515 vmstats.v_cache_max = 2 * vmstats.v_cache_min; 1516 } else { 1517 vmstats.v_cache_min = 0; 1518 vmstats.v_cache_max = 0; 1519 } 1520 vmstats.v_inactive_target = vmstats.v_free_count / 4; 1521 1522 /* XXX does not really belong here */ 1523 if (vm_page_max_wired == 0) 1524 vm_page_max_wired = vmstats.v_free_count / 3; 1525 1526 if (vm_pageout_stats_max == 0) 1527 vm_pageout_stats_max = vmstats.v_free_target; 1528 1529 /* 1530 * Set interval in seconds for stats scan. 1531 */ 1532 if (vm_pageout_stats_interval == 0) 1533 vm_pageout_stats_interval = 5; 1534 if (vm_pageout_full_stats_interval == 0) 1535 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4; 1536 1537 1538 /* 1539 * Set maximum free per pass 1540 */ 1541 if (vm_pageout_stats_free_max == 0) 1542 vm_pageout_stats_free_max = 5; 1543 1544 swap_pager_swap_init(); 1545 pass = 0; 1546 1547 /* 1548 * The pageout daemon is never done, so loop forever. 1549 */ 1550 while (TRUE) { 1551 int error; 1552 1553 /* 1554 * Wait for an action request 1555 */ 1556 crit_enter(); 1557 if (vm_pages_needed == 0) { 1558 error = tsleep(&vm_pages_needed, 1559 0, "psleep", 1560 vm_pageout_stats_interval * hz); 1561 if (error && vm_pages_needed == 0) { 1562 vm_pageout_page_stats(); 1563 continue; 1564 } 1565 vm_pages_needed = 1; 1566 } 1567 crit_exit(); 1568 1569 /* 1570 * If we have enough free memory, wakeup waiters. 1571 * (This is optional here) 1572 */ 1573 crit_enter(); 1574 if (!vm_page_count_min(0)) 1575 wakeup(&vmstats.v_free_count); 1576 mycpu->gd_cnt.v_pdwakeups++; 1577 crit_exit(); 1578 1579 /* 1580 * Scan for pageout. Try to avoid thrashing the system 1581 * with activity. 1582 */ 1583 inactive_shortage = vm_pageout_scan(pass); 1584 if (inactive_shortage > 0) { 1585 ++pass; 1586 if (swap_pager_full) { 1587 /* 1588 * Running out of memory, catastrophic back-off 1589 * to one-second intervals. 1590 */ 1591 tsleep(&vm_pages_needed, 0, "pdelay", hz); 1592 } else if (pass < 10 && vm_pages_needed > 1) { 1593 /* 1594 * Normal operation, additional processes 1595 * have already kicked us. Retry immediately. 1596 */ 1597 } else if (pass < 10) { 1598 /* 1599 * Normal operation, fewer processes. Delay 1600 * a bit but allow wakeups. 1601 */ 1602 vm_pages_needed = 0; 1603 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10); 1604 vm_pages_needed = 1; 1605 } else { 1606 /* 1607 * We've taken too many passes, forced delay. 1608 */ 1609 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10); 1610 } 1611 } else { 1612 /* 1613 * Interlocked wakeup of waiters (non-optional) 1614 */ 1615 pass = 0; 1616 if (vm_pages_needed && !vm_page_count_min(0)) { 1617 wakeup(&vmstats.v_free_count); 1618 vm_pages_needed = 0; 1619 } 1620 } 1621 } 1622 } 1623 1624 /* 1625 * Called after allocating a page out of the cache or free queue 1626 * to possibly wake the pagedaemon up to replentish our supply. 1627 * 1628 * We try to generate some hysteresis by waking the pagedaemon up 1629 * when our free+cache pages go below the severe level. The pagedaemon 1630 * tries to get the count back up to at least the minimum, and through 1631 * to the target level if possible. 1632 * 1633 * If the pagedaemon is already active bump vm_pages_needed as a hint 1634 * that there are even more requests pending. 1635 */ 1636 void 1637 pagedaemon_wakeup(void) 1638 { 1639 if (vm_page_count_severe() && curthread != pagethread) { 1640 if (vm_pages_needed == 0) { 1641 vm_pages_needed = 1; 1642 wakeup(&vm_pages_needed); 1643 } else if (vm_page_count_min(0)) { 1644 ++vm_pages_needed; 1645 } 1646 } 1647 } 1648 1649 #if !defined(NO_SWAPPING) 1650 static void 1651 vm_req_vmdaemon(void) 1652 { 1653 static int lastrun = 0; 1654 1655 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 1656 wakeup(&vm_daemon_needed); 1657 lastrun = ticks; 1658 } 1659 } 1660 1661 static int vm_daemon_callback(struct proc *p, void *data __unused); 1662 1663 static void 1664 vm_daemon(void) 1665 { 1666 while (TRUE) { 1667 tsleep(&vm_daemon_needed, 0, "psleep", 0); 1668 if (vm_pageout_req_swapout) { 1669 swapout_procs(vm_pageout_req_swapout); 1670 vm_pageout_req_swapout = 0; 1671 } 1672 /* 1673 * scan the processes for exceeding their rlimits or if 1674 * process is swapped out -- deactivate pages 1675 */ 1676 allproc_scan(vm_daemon_callback, NULL); 1677 } 1678 } 1679 1680 static int 1681 vm_daemon_callback(struct proc *p, void *data __unused) 1682 { 1683 vm_pindex_t limit, size; 1684 1685 /* 1686 * if this is a system process or if we have already 1687 * looked at this process, skip it. 1688 */ 1689 if (p->p_flag & (P_SYSTEM | P_WEXIT)) 1690 return (0); 1691 1692 /* 1693 * if the process is in a non-running type state, 1694 * don't touch it. 1695 */ 1696 if (p->p_stat != SACTIVE && p->p_stat != SSTOP) 1697 return (0); 1698 1699 /* 1700 * get a limit 1701 */ 1702 limit = OFF_TO_IDX(qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur, 1703 p->p_rlimit[RLIMIT_RSS].rlim_max)); 1704 1705 /* 1706 * let processes that are swapped out really be 1707 * swapped out. Set the limit to nothing to get as 1708 * many pages out to swap as possible. 1709 */ 1710 if (p->p_flag & P_SWAPPEDOUT) 1711 limit = 0; 1712 1713 size = vmspace_resident_count(p->p_vmspace); 1714 if (limit >= 0 && size >= limit) { 1715 vm_pageout_map_deactivate_pages( 1716 &p->p_vmspace->vm_map, limit); 1717 } 1718 return (0); 1719 } 1720 1721 #endif 1722