1 /* 2 * linux/mm/vmscan.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, Stephen Tweedie. 7 * kswapd added: 7.1.96 sct 8 * Removed kswapd_ctl limits, and swap out as many pages as needed 9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 11 * Multiqueue VM started 5.8.00, Rik van Riel. 12 */ 13 14 #include <linux/mm.h> 15 #include <linux/module.h> 16 #include <linux/gfp.h> 17 #include <linux/kernel_stat.h> 18 #include <linux/swap.h> 19 #include <linux/pagemap.h> 20 #include <linux/init.h> 21 #include <linux/highmem.h> 22 #include <linux/vmstat.h> 23 #include <linux/file.h> 24 #include <linux/writeback.h> 25 #include <linux/blkdev.h> 26 #include <linux/buffer_head.h> /* for try_to_release_page(), 27 buffer_heads_over_limit */ 28 #include <linux/mm_inline.h> 29 #include <linux/pagevec.h> 30 #include <linux/backing-dev.h> 31 #include <linux/rmap.h> 32 #include <linux/topology.h> 33 #include <linux/cpu.h> 34 #include <linux/cpuset.h> 35 #include <linux/compaction.h> 36 #include <linux/notifier.h> 37 #include <linux/rwsem.h> 38 #include <linux/delay.h> 39 #include <linux/kthread.h> 40 #include <linux/freezer.h> 41 #include <linux/memcontrol.h> 42 #include <linux/delayacct.h> 43 #include <linux/sysctl.h> 44 #include <linux/oom.h> 45 #include <linux/prefetch.h> 46 47 #include <asm/tlbflush.h> 48 #include <asm/div64.h> 49 50 #include <linux/swapops.h> 51 52 #include "internal.h" 53 54 #define CREATE_TRACE_POINTS 55 #include <trace/events/vmscan.h> 56 57 /* 58 * reclaim_mode determines how the inactive list is shrunk 59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 60 * RECLAIM_MODE_ASYNC: Do not block 61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 63 * page from the LRU and reclaim all pages within a 64 * naturally aligned range 65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 66 * order-0 pages and then compact the zone 67 */ 68 typedef unsigned __bitwise__ reclaim_mode_t; 69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 74 75 struct scan_control { 76 /* Incremented by the number of inactive pages that were scanned */ 77 unsigned long nr_scanned; 78 79 /* Number of pages freed so far during a call to shrink_zones() */ 80 unsigned long nr_reclaimed; 81 82 /* How many pages shrink_list() should reclaim */ 83 unsigned long nr_to_reclaim; 84 85 unsigned long hibernation_mode; 86 87 /* This context's GFP mask */ 88 gfp_t gfp_mask; 89 90 int may_writepage; 91 92 /* Can mapped pages be reclaimed? */ 93 int may_unmap; 94 95 /* Can pages be swapped as part of reclaim? */ 96 int may_swap; 97 98 int swappiness; 99 100 int order; 101 102 /* 103 * Intend to reclaim enough continuous memory rather than reclaim 104 * enough amount of memory. i.e, mode for high order allocation. 105 */ 106 reclaim_mode_t reclaim_mode; 107 108 /* Which cgroup do we reclaim from */ 109 struct mem_cgroup *mem_cgroup; 110 111 /* 112 * Nodemask of nodes allowed by the caller. If NULL, all nodes 113 * are scanned. 114 */ 115 nodemask_t *nodemask; 116 }; 117 118 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 119 120 #ifdef ARCH_HAS_PREFETCH 121 #define prefetch_prev_lru_page(_page, _base, _field) \ 122 do { \ 123 if ((_page)->lru.prev != _base) { \ 124 struct page *prev; \ 125 \ 126 prev = lru_to_page(&(_page->lru)); \ 127 prefetch(&prev->_field); \ 128 } \ 129 } while (0) 130 #else 131 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 132 #endif 133 134 #ifdef ARCH_HAS_PREFETCHW 135 #define prefetchw_prev_lru_page(_page, _base, _field) \ 136 do { \ 137 if ((_page)->lru.prev != _base) { \ 138 struct page *prev; \ 139 \ 140 prev = lru_to_page(&(_page->lru)); \ 141 prefetchw(&prev->_field); \ 142 } \ 143 } while (0) 144 #else 145 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 146 #endif 147 148 /* 149 * From 0 .. 100. Higher means more swappy. 150 */ 151 int vm_swappiness = 60; 152 long vm_total_pages; /* The total number of pages which the VM controls */ 153 154 static LIST_HEAD(shrinker_list); 155 static DECLARE_RWSEM(shrinker_rwsem); 156 157 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 158 #define scanning_global_lru(sc) (!(sc)->mem_cgroup) 159 #else 160 #define scanning_global_lru(sc) (1) 161 #endif 162 163 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 164 struct scan_control *sc) 165 { 166 if (!scanning_global_lru(sc)) 167 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 168 169 return &zone->reclaim_stat; 170 } 171 172 static unsigned long zone_nr_lru_pages(struct zone *zone, 173 struct scan_control *sc, enum lru_list lru) 174 { 175 if (!scanning_global_lru(sc)) 176 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup, zone, lru); 177 178 return zone_page_state(zone, NR_LRU_BASE + lru); 179 } 180 181 182 /* 183 * Add a shrinker callback to be called from the vm 184 */ 185 void register_shrinker(struct shrinker *shrinker) 186 { 187 shrinker->nr = 0; 188 down_write(&shrinker_rwsem); 189 list_add_tail(&shrinker->list, &shrinker_list); 190 up_write(&shrinker_rwsem); 191 } 192 EXPORT_SYMBOL(register_shrinker); 193 194 /* 195 * Remove one 196 */ 197 void unregister_shrinker(struct shrinker *shrinker) 198 { 199 down_write(&shrinker_rwsem); 200 list_del(&shrinker->list); 201 up_write(&shrinker_rwsem); 202 } 203 EXPORT_SYMBOL(unregister_shrinker); 204 205 static inline int do_shrinker_shrink(struct shrinker *shrinker, 206 struct shrink_control *sc, 207 unsigned long nr_to_scan) 208 { 209 sc->nr_to_scan = nr_to_scan; 210 return (*shrinker->shrink)(shrinker, sc); 211 } 212 213 #define SHRINK_BATCH 128 214 /* 215 * Call the shrink functions to age shrinkable caches 216 * 217 * Here we assume it costs one seek to replace a lru page and that it also 218 * takes a seek to recreate a cache object. With this in mind we age equal 219 * percentages of the lru and ageable caches. This should balance the seeks 220 * generated by these structures. 221 * 222 * If the vm encountered mapped pages on the LRU it increase the pressure on 223 * slab to avoid swapping. 224 * 225 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 226 * 227 * `lru_pages' represents the number of on-LRU pages in all the zones which 228 * are eligible for the caller's allocation attempt. It is used for balancing 229 * slab reclaim versus page reclaim. 230 * 231 * Returns the number of slab objects which we shrunk. 232 */ 233 unsigned long shrink_slab(struct shrink_control *shrink, 234 unsigned long nr_pages_scanned, 235 unsigned long lru_pages) 236 { 237 struct shrinker *shrinker; 238 unsigned long ret = 0; 239 240 if (nr_pages_scanned == 0) 241 nr_pages_scanned = SWAP_CLUSTER_MAX; 242 243 if (!down_read_trylock(&shrinker_rwsem)) { 244 /* Assume we'll be able to shrink next time */ 245 ret = 1; 246 goto out; 247 } 248 249 list_for_each_entry(shrinker, &shrinker_list, list) { 250 unsigned long long delta; 251 unsigned long total_scan; 252 unsigned long max_pass; 253 int shrink_ret = 0; 254 long nr; 255 long new_nr; 256 long batch_size = shrinker->batch ? shrinker->batch 257 : SHRINK_BATCH; 258 259 /* 260 * copy the current shrinker scan count into a local variable 261 * and zero it so that other concurrent shrinker invocations 262 * don't also do this scanning work. 263 */ 264 do { 265 nr = shrinker->nr; 266 } while (cmpxchg(&shrinker->nr, nr, 0) != nr); 267 268 total_scan = nr; 269 max_pass = do_shrinker_shrink(shrinker, shrink, 0); 270 delta = (4 * nr_pages_scanned) / shrinker->seeks; 271 delta *= max_pass; 272 do_div(delta, lru_pages + 1); 273 total_scan += delta; 274 if (total_scan < 0) { 275 printk(KERN_ERR "shrink_slab: %pF negative objects to " 276 "delete nr=%ld\n", 277 shrinker->shrink, total_scan); 278 total_scan = max_pass; 279 } 280 281 /* 282 * We need to avoid excessive windup on filesystem shrinkers 283 * due to large numbers of GFP_NOFS allocations causing the 284 * shrinkers to return -1 all the time. This results in a large 285 * nr being built up so when a shrink that can do some work 286 * comes along it empties the entire cache due to nr >>> 287 * max_pass. This is bad for sustaining a working set in 288 * memory. 289 * 290 * Hence only allow the shrinker to scan the entire cache when 291 * a large delta change is calculated directly. 292 */ 293 if (delta < max_pass / 4) 294 total_scan = min(total_scan, max_pass / 2); 295 296 /* 297 * Avoid risking looping forever due to too large nr value: 298 * never try to free more than twice the estimate number of 299 * freeable entries. 300 */ 301 if (total_scan > max_pass * 2) 302 total_scan = max_pass * 2; 303 304 trace_mm_shrink_slab_start(shrinker, shrink, nr, 305 nr_pages_scanned, lru_pages, 306 max_pass, delta, total_scan); 307 308 while (total_scan >= batch_size) { 309 int nr_before; 310 311 nr_before = do_shrinker_shrink(shrinker, shrink, 0); 312 shrink_ret = do_shrinker_shrink(shrinker, shrink, 313 batch_size); 314 if (shrink_ret == -1) 315 break; 316 if (shrink_ret < nr_before) 317 ret += nr_before - shrink_ret; 318 count_vm_events(SLABS_SCANNED, batch_size); 319 total_scan -= batch_size; 320 321 cond_resched(); 322 } 323 324 /* 325 * move the unused scan count back into the shrinker in a 326 * manner that handles concurrent updates. If we exhausted the 327 * scan, there is no need to do an update. 328 */ 329 do { 330 nr = shrinker->nr; 331 new_nr = total_scan + nr; 332 if (total_scan <= 0) 333 break; 334 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr); 335 336 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); 337 } 338 up_read(&shrinker_rwsem); 339 out: 340 cond_resched(); 341 return ret; 342 } 343 344 static void set_reclaim_mode(int priority, struct scan_control *sc, 345 bool sync) 346 { 347 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 348 349 /* 350 * Initially assume we are entering either lumpy reclaim or 351 * reclaim/compaction.Depending on the order, we will either set the 352 * sync mode or just reclaim order-0 pages later. 353 */ 354 if (COMPACTION_BUILD) 355 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 356 else 357 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 358 359 /* 360 * Avoid using lumpy reclaim or reclaim/compaction if possible by 361 * restricting when its set to either costly allocations or when 362 * under memory pressure 363 */ 364 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 365 sc->reclaim_mode |= syncmode; 366 else if (sc->order && priority < DEF_PRIORITY - 2) 367 sc->reclaim_mode |= syncmode; 368 else 369 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 370 } 371 372 static void reset_reclaim_mode(struct scan_control *sc) 373 { 374 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 375 } 376 377 static inline int is_page_cache_freeable(struct page *page) 378 { 379 /* 380 * A freeable page cache page is referenced only by the caller 381 * that isolated the page, the page cache radix tree and 382 * optional buffer heads at page->private. 383 */ 384 return page_count(page) - page_has_private(page) == 2; 385 } 386 387 static int may_write_to_queue(struct backing_dev_info *bdi, 388 struct scan_control *sc) 389 { 390 if (current->flags & PF_SWAPWRITE) 391 return 1; 392 if (!bdi_write_congested(bdi)) 393 return 1; 394 if (bdi == current->backing_dev_info) 395 return 1; 396 397 /* lumpy reclaim for hugepage often need a lot of write */ 398 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 399 return 1; 400 return 0; 401 } 402 403 /* 404 * We detected a synchronous write error writing a page out. Probably 405 * -ENOSPC. We need to propagate that into the address_space for a subsequent 406 * fsync(), msync() or close(). 407 * 408 * The tricky part is that after writepage we cannot touch the mapping: nothing 409 * prevents it from being freed up. But we have a ref on the page and once 410 * that page is locked, the mapping is pinned. 411 * 412 * We're allowed to run sleeping lock_page() here because we know the caller has 413 * __GFP_FS. 414 */ 415 static void handle_write_error(struct address_space *mapping, 416 struct page *page, int error) 417 { 418 lock_page(page); 419 if (page_mapping(page) == mapping) 420 mapping_set_error(mapping, error); 421 unlock_page(page); 422 } 423 424 /* possible outcome of pageout() */ 425 typedef enum { 426 /* failed to write page out, page is locked */ 427 PAGE_KEEP, 428 /* move page to the active list, page is locked */ 429 PAGE_ACTIVATE, 430 /* page has been sent to the disk successfully, page is unlocked */ 431 PAGE_SUCCESS, 432 /* page is clean and locked */ 433 PAGE_CLEAN, 434 } pageout_t; 435 436 /* 437 * pageout is called by shrink_page_list() for each dirty page. 438 * Calls ->writepage(). 439 */ 440 static pageout_t pageout(struct page *page, struct address_space *mapping, 441 struct scan_control *sc) 442 { 443 /* 444 * If the page is dirty, only perform writeback if that write 445 * will be non-blocking. To prevent this allocation from being 446 * stalled by pagecache activity. But note that there may be 447 * stalls if we need to run get_block(). We could test 448 * PagePrivate for that. 449 * 450 * If this process is currently in __generic_file_aio_write() against 451 * this page's queue, we can perform writeback even if that 452 * will block. 453 * 454 * If the page is swapcache, write it back even if that would 455 * block, for some throttling. This happens by accident, because 456 * swap_backing_dev_info is bust: it doesn't reflect the 457 * congestion state of the swapdevs. Easy to fix, if needed. 458 */ 459 if (!is_page_cache_freeable(page)) 460 return PAGE_KEEP; 461 if (!mapping) { 462 /* 463 * Some data journaling orphaned pages can have 464 * page->mapping == NULL while being dirty with clean buffers. 465 */ 466 if (page_has_private(page)) { 467 if (try_to_free_buffers(page)) { 468 ClearPageDirty(page); 469 printk("%s: orphaned page\n", __func__); 470 return PAGE_CLEAN; 471 } 472 } 473 return PAGE_KEEP; 474 } 475 if (mapping->a_ops->writepage == NULL) 476 return PAGE_ACTIVATE; 477 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 478 return PAGE_KEEP; 479 480 if (clear_page_dirty_for_io(page)) { 481 int res; 482 struct writeback_control wbc = { 483 .sync_mode = WB_SYNC_NONE, 484 .nr_to_write = SWAP_CLUSTER_MAX, 485 .range_start = 0, 486 .range_end = LLONG_MAX, 487 .for_reclaim = 1, 488 }; 489 490 SetPageReclaim(page); 491 res = mapping->a_ops->writepage(page, &wbc); 492 if (res < 0) 493 handle_write_error(mapping, page, res); 494 if (res == AOP_WRITEPAGE_ACTIVATE) { 495 ClearPageReclaim(page); 496 return PAGE_ACTIVATE; 497 } 498 499 /* 500 * Wait on writeback if requested to. This happens when 501 * direct reclaiming a large contiguous area and the 502 * first attempt to free a range of pages fails. 503 */ 504 if (PageWriteback(page) && 505 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 506 wait_on_page_writeback(page); 507 508 if (!PageWriteback(page)) { 509 /* synchronous write or broken a_ops? */ 510 ClearPageReclaim(page); 511 } 512 trace_mm_vmscan_writepage(page, 513 trace_reclaim_flags(page, sc->reclaim_mode)); 514 inc_zone_page_state(page, NR_VMSCAN_WRITE); 515 return PAGE_SUCCESS; 516 } 517 518 return PAGE_CLEAN; 519 } 520 521 /* 522 * Same as remove_mapping, but if the page is removed from the mapping, it 523 * gets returned with a refcount of 0. 524 */ 525 static int __remove_mapping(struct address_space *mapping, struct page *page) 526 { 527 BUG_ON(!PageLocked(page)); 528 BUG_ON(mapping != page_mapping(page)); 529 530 spin_lock_irq(&mapping->tree_lock); 531 /* 532 * The non racy check for a busy page. 533 * 534 * Must be careful with the order of the tests. When someone has 535 * a ref to the page, it may be possible that they dirty it then 536 * drop the reference. So if PageDirty is tested before page_count 537 * here, then the following race may occur: 538 * 539 * get_user_pages(&page); 540 * [user mapping goes away] 541 * write_to(page); 542 * !PageDirty(page) [good] 543 * SetPageDirty(page); 544 * put_page(page); 545 * !page_count(page) [good, discard it] 546 * 547 * [oops, our write_to data is lost] 548 * 549 * Reversing the order of the tests ensures such a situation cannot 550 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 551 * load is not satisfied before that of page->_count. 552 * 553 * Note that if SetPageDirty is always performed via set_page_dirty, 554 * and thus under tree_lock, then this ordering is not required. 555 */ 556 if (!page_freeze_refs(page, 2)) 557 goto cannot_free; 558 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 559 if (unlikely(PageDirty(page))) { 560 page_unfreeze_refs(page, 2); 561 goto cannot_free; 562 } 563 564 if (PageSwapCache(page)) { 565 swp_entry_t swap = { .val = page_private(page) }; 566 __delete_from_swap_cache(page); 567 spin_unlock_irq(&mapping->tree_lock); 568 swapcache_free(swap, page); 569 } else { 570 void (*freepage)(struct page *); 571 572 freepage = mapping->a_ops->freepage; 573 574 __delete_from_page_cache(page); 575 spin_unlock_irq(&mapping->tree_lock); 576 mem_cgroup_uncharge_cache_page(page); 577 578 if (freepage != NULL) 579 freepage(page); 580 } 581 582 return 1; 583 584 cannot_free: 585 spin_unlock_irq(&mapping->tree_lock); 586 return 0; 587 } 588 589 /* 590 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 591 * someone else has a ref on the page, abort and return 0. If it was 592 * successfully detached, return 1. Assumes the caller has a single ref on 593 * this page. 594 */ 595 int remove_mapping(struct address_space *mapping, struct page *page) 596 { 597 if (__remove_mapping(mapping, page)) { 598 /* 599 * Unfreezing the refcount with 1 rather than 2 effectively 600 * drops the pagecache ref for us without requiring another 601 * atomic operation. 602 */ 603 page_unfreeze_refs(page, 1); 604 return 1; 605 } 606 return 0; 607 } 608 609 /** 610 * putback_lru_page - put previously isolated page onto appropriate LRU list 611 * @page: page to be put back to appropriate lru list 612 * 613 * Add previously isolated @page to appropriate LRU list. 614 * Page may still be unevictable for other reasons. 615 * 616 * lru_lock must not be held, interrupts must be enabled. 617 */ 618 void putback_lru_page(struct page *page) 619 { 620 int lru; 621 int active = !!TestClearPageActive(page); 622 int was_unevictable = PageUnevictable(page); 623 624 VM_BUG_ON(PageLRU(page)); 625 626 redo: 627 ClearPageUnevictable(page); 628 629 if (page_evictable(page, NULL)) { 630 /* 631 * For evictable pages, we can use the cache. 632 * In event of a race, worst case is we end up with an 633 * unevictable page on [in]active list. 634 * We know how to handle that. 635 */ 636 lru = active + page_lru_base_type(page); 637 lru_cache_add_lru(page, lru); 638 } else { 639 /* 640 * Put unevictable pages directly on zone's unevictable 641 * list. 642 */ 643 lru = LRU_UNEVICTABLE; 644 add_page_to_unevictable_list(page); 645 /* 646 * When racing with an mlock clearing (page is 647 * unlocked), make sure that if the other thread does 648 * not observe our setting of PG_lru and fails 649 * isolation, we see PG_mlocked cleared below and move 650 * the page back to the evictable list. 651 * 652 * The other side is TestClearPageMlocked(). 653 */ 654 smp_mb(); 655 } 656 657 /* 658 * page's status can change while we move it among lru. If an evictable 659 * page is on unevictable list, it never be freed. To avoid that, 660 * check after we added it to the list, again. 661 */ 662 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 663 if (!isolate_lru_page(page)) { 664 put_page(page); 665 goto redo; 666 } 667 /* This means someone else dropped this page from LRU 668 * So, it will be freed or putback to LRU again. There is 669 * nothing to do here. 670 */ 671 } 672 673 if (was_unevictable && lru != LRU_UNEVICTABLE) 674 count_vm_event(UNEVICTABLE_PGRESCUED); 675 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 676 count_vm_event(UNEVICTABLE_PGCULLED); 677 678 put_page(page); /* drop ref from isolate */ 679 } 680 681 enum page_references { 682 PAGEREF_RECLAIM, 683 PAGEREF_RECLAIM_CLEAN, 684 PAGEREF_KEEP, 685 PAGEREF_ACTIVATE, 686 }; 687 688 static enum page_references page_check_references(struct page *page, 689 struct scan_control *sc) 690 { 691 int referenced_ptes, referenced_page; 692 unsigned long vm_flags; 693 694 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 695 referenced_page = TestClearPageReferenced(page); 696 697 /* Lumpy reclaim - ignore references */ 698 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 699 return PAGEREF_RECLAIM; 700 701 /* 702 * Mlock lost the isolation race with us. Let try_to_unmap() 703 * move the page to the unevictable list. 704 */ 705 if (vm_flags & VM_LOCKED) 706 return PAGEREF_RECLAIM; 707 708 if (referenced_ptes) { 709 if (PageAnon(page)) 710 return PAGEREF_ACTIVATE; 711 /* 712 * All mapped pages start out with page table 713 * references from the instantiating fault, so we need 714 * to look twice if a mapped file page is used more 715 * than once. 716 * 717 * Mark it and spare it for another trip around the 718 * inactive list. Another page table reference will 719 * lead to its activation. 720 * 721 * Note: the mark is set for activated pages as well 722 * so that recently deactivated but used pages are 723 * quickly recovered. 724 */ 725 SetPageReferenced(page); 726 727 if (referenced_page) 728 return PAGEREF_ACTIVATE; 729 730 return PAGEREF_KEEP; 731 } 732 733 /* Reclaim if clean, defer dirty pages to writeback */ 734 if (referenced_page && !PageSwapBacked(page)) 735 return PAGEREF_RECLAIM_CLEAN; 736 737 return PAGEREF_RECLAIM; 738 } 739 740 static noinline_for_stack void free_page_list(struct list_head *free_pages) 741 { 742 struct pagevec freed_pvec; 743 struct page *page, *tmp; 744 745 pagevec_init(&freed_pvec, 1); 746 747 list_for_each_entry_safe(page, tmp, free_pages, lru) { 748 list_del(&page->lru); 749 if (!pagevec_add(&freed_pvec, page)) { 750 __pagevec_free(&freed_pvec); 751 pagevec_reinit(&freed_pvec); 752 } 753 } 754 755 pagevec_free(&freed_pvec); 756 } 757 758 /* 759 * shrink_page_list() returns the number of reclaimed pages 760 */ 761 static unsigned long shrink_page_list(struct list_head *page_list, 762 struct zone *zone, 763 struct scan_control *sc) 764 { 765 LIST_HEAD(ret_pages); 766 LIST_HEAD(free_pages); 767 int pgactivate = 0; 768 unsigned long nr_dirty = 0; 769 unsigned long nr_congested = 0; 770 unsigned long nr_reclaimed = 0; 771 772 cond_resched(); 773 774 while (!list_empty(page_list)) { 775 enum page_references references; 776 struct address_space *mapping; 777 struct page *page; 778 int may_enter_fs; 779 780 cond_resched(); 781 782 page = lru_to_page(page_list); 783 list_del(&page->lru); 784 785 if (!trylock_page(page)) 786 goto keep; 787 788 VM_BUG_ON(PageActive(page)); 789 VM_BUG_ON(page_zone(page) != zone); 790 791 sc->nr_scanned++; 792 793 if (unlikely(!page_evictable(page, NULL))) 794 goto cull_mlocked; 795 796 if (!sc->may_unmap && page_mapped(page)) 797 goto keep_locked; 798 799 /* Double the slab pressure for mapped and swapcache pages */ 800 if (page_mapped(page) || PageSwapCache(page)) 801 sc->nr_scanned++; 802 803 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 804 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 805 806 if (PageWriteback(page)) { 807 /* 808 * Synchronous reclaim is performed in two passes, 809 * first an asynchronous pass over the list to 810 * start parallel writeback, and a second synchronous 811 * pass to wait for the IO to complete. Wait here 812 * for any page for which writeback has already 813 * started. 814 */ 815 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 816 may_enter_fs) 817 wait_on_page_writeback(page); 818 else { 819 unlock_page(page); 820 goto keep_lumpy; 821 } 822 } 823 824 references = page_check_references(page, sc); 825 switch (references) { 826 case PAGEREF_ACTIVATE: 827 goto activate_locked; 828 case PAGEREF_KEEP: 829 goto keep_locked; 830 case PAGEREF_RECLAIM: 831 case PAGEREF_RECLAIM_CLEAN: 832 ; /* try to reclaim the page below */ 833 } 834 835 /* 836 * Anonymous process memory has backing store? 837 * Try to allocate it some swap space here. 838 */ 839 if (PageAnon(page) && !PageSwapCache(page)) { 840 if (!(sc->gfp_mask & __GFP_IO)) 841 goto keep_locked; 842 if (!add_to_swap(page)) 843 goto activate_locked; 844 may_enter_fs = 1; 845 } 846 847 mapping = page_mapping(page); 848 849 /* 850 * The page is mapped into the page tables of one or more 851 * processes. Try to unmap it here. 852 */ 853 if (page_mapped(page) && mapping) { 854 switch (try_to_unmap(page, TTU_UNMAP)) { 855 case SWAP_FAIL: 856 goto activate_locked; 857 case SWAP_AGAIN: 858 goto keep_locked; 859 case SWAP_MLOCK: 860 goto cull_mlocked; 861 case SWAP_SUCCESS: 862 ; /* try to free the page below */ 863 } 864 } 865 866 if (PageDirty(page)) { 867 nr_dirty++; 868 869 if (references == PAGEREF_RECLAIM_CLEAN) 870 goto keep_locked; 871 if (!may_enter_fs) 872 goto keep_locked; 873 if (!sc->may_writepage) 874 goto keep_locked; 875 876 /* Page is dirty, try to write it out here */ 877 switch (pageout(page, mapping, sc)) { 878 case PAGE_KEEP: 879 nr_congested++; 880 goto keep_locked; 881 case PAGE_ACTIVATE: 882 goto activate_locked; 883 case PAGE_SUCCESS: 884 if (PageWriteback(page)) 885 goto keep_lumpy; 886 if (PageDirty(page)) 887 goto keep; 888 889 /* 890 * A synchronous write - probably a ramdisk. Go 891 * ahead and try to reclaim the page. 892 */ 893 if (!trylock_page(page)) 894 goto keep; 895 if (PageDirty(page) || PageWriteback(page)) 896 goto keep_locked; 897 mapping = page_mapping(page); 898 case PAGE_CLEAN: 899 ; /* try to free the page below */ 900 } 901 } 902 903 /* 904 * If the page has buffers, try to free the buffer mappings 905 * associated with this page. If we succeed we try to free 906 * the page as well. 907 * 908 * We do this even if the page is PageDirty(). 909 * try_to_release_page() does not perform I/O, but it is 910 * possible for a page to have PageDirty set, but it is actually 911 * clean (all its buffers are clean). This happens if the 912 * buffers were written out directly, with submit_bh(). ext3 913 * will do this, as well as the blockdev mapping. 914 * try_to_release_page() will discover that cleanness and will 915 * drop the buffers and mark the page clean - it can be freed. 916 * 917 * Rarely, pages can have buffers and no ->mapping. These are 918 * the pages which were not successfully invalidated in 919 * truncate_complete_page(). We try to drop those buffers here 920 * and if that worked, and the page is no longer mapped into 921 * process address space (page_count == 1) it can be freed. 922 * Otherwise, leave the page on the LRU so it is swappable. 923 */ 924 if (page_has_private(page)) { 925 if (!try_to_release_page(page, sc->gfp_mask)) 926 goto activate_locked; 927 if (!mapping && page_count(page) == 1) { 928 unlock_page(page); 929 if (put_page_testzero(page)) 930 goto free_it; 931 else { 932 /* 933 * rare race with speculative reference. 934 * the speculative reference will free 935 * this page shortly, so we may 936 * increment nr_reclaimed here (and 937 * leave it off the LRU). 938 */ 939 nr_reclaimed++; 940 continue; 941 } 942 } 943 } 944 945 if (!mapping || !__remove_mapping(mapping, page)) 946 goto keep_locked; 947 948 /* 949 * At this point, we have no other references and there is 950 * no way to pick any more up (removed from LRU, removed 951 * from pagecache). Can use non-atomic bitops now (and 952 * we obviously don't have to worry about waking up a process 953 * waiting on the page lock, because there are no references. 954 */ 955 __clear_page_locked(page); 956 free_it: 957 nr_reclaimed++; 958 959 /* 960 * Is there need to periodically free_page_list? It would 961 * appear not as the counts should be low 962 */ 963 list_add(&page->lru, &free_pages); 964 continue; 965 966 cull_mlocked: 967 if (PageSwapCache(page)) 968 try_to_free_swap(page); 969 unlock_page(page); 970 putback_lru_page(page); 971 reset_reclaim_mode(sc); 972 continue; 973 974 activate_locked: 975 /* Not a candidate for swapping, so reclaim swap space. */ 976 if (PageSwapCache(page) && vm_swap_full()) 977 try_to_free_swap(page); 978 VM_BUG_ON(PageActive(page)); 979 SetPageActive(page); 980 pgactivate++; 981 keep_locked: 982 unlock_page(page); 983 keep: 984 reset_reclaim_mode(sc); 985 keep_lumpy: 986 list_add(&page->lru, &ret_pages); 987 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 988 } 989 990 /* 991 * Tag a zone as congested if all the dirty pages encountered were 992 * backed by a congested BDI. In this case, reclaimers should just 993 * back off and wait for congestion to clear because further reclaim 994 * will encounter the same problem 995 */ 996 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 997 zone_set_flag(zone, ZONE_CONGESTED); 998 999 free_page_list(&free_pages); 1000 1001 list_splice(&ret_pages, page_list); 1002 count_vm_events(PGACTIVATE, pgactivate); 1003 return nr_reclaimed; 1004 } 1005 1006 /* 1007 * Attempt to remove the specified page from its LRU. Only take this page 1008 * if it is of the appropriate PageActive status. Pages which are being 1009 * freed elsewhere are also ignored. 1010 * 1011 * page: page to consider 1012 * mode: one of the LRU isolation modes defined above 1013 * 1014 * returns 0 on success, -ve errno on failure. 1015 */ 1016 int __isolate_lru_page(struct page *page, int mode, int file) 1017 { 1018 int ret = -EINVAL; 1019 1020 /* Only take pages on the LRU. */ 1021 if (!PageLRU(page)) 1022 return ret; 1023 1024 /* 1025 * When checking the active state, we need to be sure we are 1026 * dealing with comparible boolean values. Take the logical not 1027 * of each. 1028 */ 1029 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 1030 return ret; 1031 1032 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 1033 return ret; 1034 1035 /* 1036 * When this function is being called for lumpy reclaim, we 1037 * initially look into all LRU pages, active, inactive and 1038 * unevictable; only give shrink_page_list evictable pages. 1039 */ 1040 if (PageUnevictable(page)) 1041 return ret; 1042 1043 ret = -EBUSY; 1044 1045 if (likely(get_page_unless_zero(page))) { 1046 /* 1047 * Be careful not to clear PageLRU until after we're 1048 * sure the page is not being freed elsewhere -- the 1049 * page release code relies on it. 1050 */ 1051 ClearPageLRU(page); 1052 ret = 0; 1053 } 1054 1055 return ret; 1056 } 1057 1058 /* 1059 * zone->lru_lock is heavily contended. Some of the functions that 1060 * shrink the lists perform better by taking out a batch of pages 1061 * and working on them outside the LRU lock. 1062 * 1063 * For pagecache intensive workloads, this function is the hottest 1064 * spot in the kernel (apart from copy_*_user functions). 1065 * 1066 * Appropriate locks must be held before calling this function. 1067 * 1068 * @nr_to_scan: The number of pages to look through on the list. 1069 * @src: The LRU list to pull pages off. 1070 * @dst: The temp list to put pages on to. 1071 * @scanned: The number of pages that were scanned. 1072 * @order: The caller's attempted allocation order 1073 * @mode: One of the LRU isolation modes 1074 * @file: True [1] if isolating file [!anon] pages 1075 * 1076 * returns how many pages were moved onto *@dst. 1077 */ 1078 static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1079 struct list_head *src, struct list_head *dst, 1080 unsigned long *scanned, int order, int mode, int file) 1081 { 1082 unsigned long nr_taken = 0; 1083 unsigned long nr_lumpy_taken = 0; 1084 unsigned long nr_lumpy_dirty = 0; 1085 unsigned long nr_lumpy_failed = 0; 1086 unsigned long scan; 1087 1088 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1089 struct page *page; 1090 unsigned long pfn; 1091 unsigned long end_pfn; 1092 unsigned long page_pfn; 1093 int zone_id; 1094 1095 page = lru_to_page(src); 1096 prefetchw_prev_lru_page(page, src, flags); 1097 1098 VM_BUG_ON(!PageLRU(page)); 1099 1100 switch (__isolate_lru_page(page, mode, file)) { 1101 case 0: 1102 list_move(&page->lru, dst); 1103 mem_cgroup_del_lru(page); 1104 nr_taken += hpage_nr_pages(page); 1105 break; 1106 1107 case -EBUSY: 1108 /* else it is being freed elsewhere */ 1109 list_move(&page->lru, src); 1110 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1111 continue; 1112 1113 default: 1114 BUG(); 1115 } 1116 1117 if (!order) 1118 continue; 1119 1120 /* 1121 * Attempt to take all pages in the order aligned region 1122 * surrounding the tag page. Only take those pages of 1123 * the same active state as that tag page. We may safely 1124 * round the target page pfn down to the requested order 1125 * as the mem_map is guaranteed valid out to MAX_ORDER, 1126 * where that page is in a different zone we will detect 1127 * it from its zone id and abort this block scan. 1128 */ 1129 zone_id = page_zone_id(page); 1130 page_pfn = page_to_pfn(page); 1131 pfn = page_pfn & ~((1 << order) - 1); 1132 end_pfn = pfn + (1 << order); 1133 for (; pfn < end_pfn; pfn++) { 1134 struct page *cursor_page; 1135 1136 /* The target page is in the block, ignore it. */ 1137 if (unlikely(pfn == page_pfn)) 1138 continue; 1139 1140 /* Avoid holes within the zone. */ 1141 if (unlikely(!pfn_valid_within(pfn))) 1142 break; 1143 1144 cursor_page = pfn_to_page(pfn); 1145 1146 /* Check that we have not crossed a zone boundary. */ 1147 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1148 break; 1149 1150 /* 1151 * If we don't have enough swap space, reclaiming of 1152 * anon page which don't already have a swap slot is 1153 * pointless. 1154 */ 1155 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1156 !PageSwapCache(cursor_page)) 1157 break; 1158 1159 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1160 list_move(&cursor_page->lru, dst); 1161 mem_cgroup_del_lru(cursor_page); 1162 nr_taken += hpage_nr_pages(page); 1163 nr_lumpy_taken++; 1164 if (PageDirty(cursor_page)) 1165 nr_lumpy_dirty++; 1166 scan++; 1167 } else { 1168 /* 1169 * Check if the page is freed already. 1170 * 1171 * We can't use page_count() as that 1172 * requires compound_head and we don't 1173 * have a pin on the page here. If a 1174 * page is tail, we may or may not 1175 * have isolated the head, so assume 1176 * it's not free, it'd be tricky to 1177 * track the head status without a 1178 * page pin. 1179 */ 1180 if (!PageTail(cursor_page) && 1181 !atomic_read(&cursor_page->_count)) 1182 continue; 1183 break; 1184 } 1185 } 1186 1187 /* If we break out of the loop above, lumpy reclaim failed */ 1188 if (pfn < end_pfn) 1189 nr_lumpy_failed++; 1190 } 1191 1192 *scanned = scan; 1193 1194 trace_mm_vmscan_lru_isolate(order, 1195 nr_to_scan, scan, 1196 nr_taken, 1197 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1198 mode); 1199 return nr_taken; 1200 } 1201 1202 static unsigned long isolate_pages_global(unsigned long nr, 1203 struct list_head *dst, 1204 unsigned long *scanned, int order, 1205 int mode, struct zone *z, 1206 int active, int file) 1207 { 1208 int lru = LRU_BASE; 1209 if (active) 1210 lru += LRU_ACTIVE; 1211 if (file) 1212 lru += LRU_FILE; 1213 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1214 mode, file); 1215 } 1216 1217 /* 1218 * clear_active_flags() is a helper for shrink_active_list(), clearing 1219 * any active bits from the pages in the list. 1220 */ 1221 static unsigned long clear_active_flags(struct list_head *page_list, 1222 unsigned int *count) 1223 { 1224 int nr_active = 0; 1225 int lru; 1226 struct page *page; 1227 1228 list_for_each_entry(page, page_list, lru) { 1229 int numpages = hpage_nr_pages(page); 1230 lru = page_lru_base_type(page); 1231 if (PageActive(page)) { 1232 lru += LRU_ACTIVE; 1233 ClearPageActive(page); 1234 nr_active += numpages; 1235 } 1236 if (count) 1237 count[lru] += numpages; 1238 } 1239 1240 return nr_active; 1241 } 1242 1243 /** 1244 * isolate_lru_page - tries to isolate a page from its LRU list 1245 * @page: page to isolate from its LRU list 1246 * 1247 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1248 * vmstat statistic corresponding to whatever LRU list the page was on. 1249 * 1250 * Returns 0 if the page was removed from an LRU list. 1251 * Returns -EBUSY if the page was not on an LRU list. 1252 * 1253 * The returned page will have PageLRU() cleared. If it was found on 1254 * the active list, it will have PageActive set. If it was found on 1255 * the unevictable list, it will have the PageUnevictable bit set. That flag 1256 * may need to be cleared by the caller before letting the page go. 1257 * 1258 * The vmstat statistic corresponding to the list on which the page was 1259 * found will be decremented. 1260 * 1261 * Restrictions: 1262 * (1) Must be called with an elevated refcount on the page. This is a 1263 * fundamentnal difference from isolate_lru_pages (which is called 1264 * without a stable reference). 1265 * (2) the lru_lock must not be held. 1266 * (3) interrupts must be enabled. 1267 */ 1268 int isolate_lru_page(struct page *page) 1269 { 1270 int ret = -EBUSY; 1271 1272 VM_BUG_ON(!page_count(page)); 1273 1274 if (PageLRU(page)) { 1275 struct zone *zone = page_zone(page); 1276 1277 spin_lock_irq(&zone->lru_lock); 1278 if (PageLRU(page)) { 1279 int lru = page_lru(page); 1280 ret = 0; 1281 get_page(page); 1282 ClearPageLRU(page); 1283 1284 del_page_from_lru_list(zone, page, lru); 1285 } 1286 spin_unlock_irq(&zone->lru_lock); 1287 } 1288 return ret; 1289 } 1290 1291 /* 1292 * Are there way too many processes in the direct reclaim path already? 1293 */ 1294 static int too_many_isolated(struct zone *zone, int file, 1295 struct scan_control *sc) 1296 { 1297 unsigned long inactive, isolated; 1298 1299 if (current_is_kswapd()) 1300 return 0; 1301 1302 if (!scanning_global_lru(sc)) 1303 return 0; 1304 1305 if (file) { 1306 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1307 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1308 } else { 1309 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1310 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1311 } 1312 1313 return isolated > inactive; 1314 } 1315 1316 /* 1317 * TODO: Try merging with migrations version of putback_lru_pages 1318 */ 1319 static noinline_for_stack void 1320 putback_lru_pages(struct zone *zone, struct scan_control *sc, 1321 unsigned long nr_anon, unsigned long nr_file, 1322 struct list_head *page_list) 1323 { 1324 struct page *page; 1325 struct pagevec pvec; 1326 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1327 1328 pagevec_init(&pvec, 1); 1329 1330 /* 1331 * Put back any unfreeable pages. 1332 */ 1333 spin_lock(&zone->lru_lock); 1334 while (!list_empty(page_list)) { 1335 int lru; 1336 page = lru_to_page(page_list); 1337 VM_BUG_ON(PageLRU(page)); 1338 list_del(&page->lru); 1339 if (unlikely(!page_evictable(page, NULL))) { 1340 spin_unlock_irq(&zone->lru_lock); 1341 putback_lru_page(page); 1342 spin_lock_irq(&zone->lru_lock); 1343 continue; 1344 } 1345 SetPageLRU(page); 1346 lru = page_lru(page); 1347 add_page_to_lru_list(zone, page, lru); 1348 if (is_active_lru(lru)) { 1349 int file = is_file_lru(lru); 1350 int numpages = hpage_nr_pages(page); 1351 reclaim_stat->recent_rotated[file] += numpages; 1352 } 1353 if (!pagevec_add(&pvec, page)) { 1354 spin_unlock_irq(&zone->lru_lock); 1355 __pagevec_release(&pvec); 1356 spin_lock_irq(&zone->lru_lock); 1357 } 1358 } 1359 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1360 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1361 1362 spin_unlock_irq(&zone->lru_lock); 1363 pagevec_release(&pvec); 1364 } 1365 1366 static noinline_for_stack void update_isolated_counts(struct zone *zone, 1367 struct scan_control *sc, 1368 unsigned long *nr_anon, 1369 unsigned long *nr_file, 1370 struct list_head *isolated_list) 1371 { 1372 unsigned long nr_active; 1373 unsigned int count[NR_LRU_LISTS] = { 0, }; 1374 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1375 1376 nr_active = clear_active_flags(isolated_list, count); 1377 __count_vm_events(PGDEACTIVATE, nr_active); 1378 1379 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1380 -count[LRU_ACTIVE_FILE]); 1381 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1382 -count[LRU_INACTIVE_FILE]); 1383 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1384 -count[LRU_ACTIVE_ANON]); 1385 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1386 -count[LRU_INACTIVE_ANON]); 1387 1388 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1389 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1390 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1391 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1392 1393 reclaim_stat->recent_scanned[0] += *nr_anon; 1394 reclaim_stat->recent_scanned[1] += *nr_file; 1395 } 1396 1397 /* 1398 * Returns true if the caller should wait to clean dirty/writeback pages. 1399 * 1400 * If we are direct reclaiming for contiguous pages and we do not reclaim 1401 * everything in the list, try again and wait for writeback IO to complete. 1402 * This will stall high-order allocations noticeably. Only do that when really 1403 * need to free the pages under high memory pressure. 1404 */ 1405 static inline bool should_reclaim_stall(unsigned long nr_taken, 1406 unsigned long nr_freed, 1407 int priority, 1408 struct scan_control *sc) 1409 { 1410 int lumpy_stall_priority; 1411 1412 /* kswapd should not stall on sync IO */ 1413 if (current_is_kswapd()) 1414 return false; 1415 1416 /* Only stall on lumpy reclaim */ 1417 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1418 return false; 1419 1420 /* If we have relaimed everything on the isolated list, no stall */ 1421 if (nr_freed == nr_taken) 1422 return false; 1423 1424 /* 1425 * For high-order allocations, there are two stall thresholds. 1426 * High-cost allocations stall immediately where as lower 1427 * order allocations such as stacks require the scanning 1428 * priority to be much higher before stalling. 1429 */ 1430 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1431 lumpy_stall_priority = DEF_PRIORITY; 1432 else 1433 lumpy_stall_priority = DEF_PRIORITY / 3; 1434 1435 return priority <= lumpy_stall_priority; 1436 } 1437 1438 /* 1439 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1440 * of reclaimed pages 1441 */ 1442 static noinline_for_stack unsigned long 1443 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1444 struct scan_control *sc, int priority, int file) 1445 { 1446 LIST_HEAD(page_list); 1447 unsigned long nr_scanned; 1448 unsigned long nr_reclaimed = 0; 1449 unsigned long nr_taken; 1450 unsigned long nr_anon; 1451 unsigned long nr_file; 1452 1453 while (unlikely(too_many_isolated(zone, file, sc))) { 1454 congestion_wait(BLK_RW_ASYNC, HZ/10); 1455 1456 /* We are about to die and free our memory. Return now. */ 1457 if (fatal_signal_pending(current)) 1458 return SWAP_CLUSTER_MAX; 1459 } 1460 1461 set_reclaim_mode(priority, sc, false); 1462 lru_add_drain(); 1463 spin_lock_irq(&zone->lru_lock); 1464 1465 if (scanning_global_lru(sc)) { 1466 nr_taken = isolate_pages_global(nr_to_scan, 1467 &page_list, &nr_scanned, sc->order, 1468 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1469 ISOLATE_BOTH : ISOLATE_INACTIVE, 1470 zone, 0, file); 1471 zone->pages_scanned += nr_scanned; 1472 if (current_is_kswapd()) 1473 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1474 nr_scanned); 1475 else 1476 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1477 nr_scanned); 1478 } else { 1479 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1480 &page_list, &nr_scanned, sc->order, 1481 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1482 ISOLATE_BOTH : ISOLATE_INACTIVE, 1483 zone, sc->mem_cgroup, 1484 0, file); 1485 /* 1486 * mem_cgroup_isolate_pages() keeps track of 1487 * scanned pages on its own. 1488 */ 1489 } 1490 1491 if (nr_taken == 0) { 1492 spin_unlock_irq(&zone->lru_lock); 1493 return 0; 1494 } 1495 1496 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1497 1498 spin_unlock_irq(&zone->lru_lock); 1499 1500 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1501 1502 /* Check if we should syncronously wait for writeback */ 1503 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1504 set_reclaim_mode(priority, sc, true); 1505 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1506 } 1507 1508 local_irq_disable(); 1509 if (current_is_kswapd()) 1510 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1511 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1512 1513 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1514 1515 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1516 zone_idx(zone), 1517 nr_scanned, nr_reclaimed, 1518 priority, 1519 trace_shrink_flags(file, sc->reclaim_mode)); 1520 return nr_reclaimed; 1521 } 1522 1523 /* 1524 * This moves pages from the active list to the inactive list. 1525 * 1526 * We move them the other way if the page is referenced by one or more 1527 * processes, from rmap. 1528 * 1529 * If the pages are mostly unmapped, the processing is fast and it is 1530 * appropriate to hold zone->lru_lock across the whole operation. But if 1531 * the pages are mapped, the processing is slow (page_referenced()) so we 1532 * should drop zone->lru_lock around each page. It's impossible to balance 1533 * this, so instead we remove the pages from the LRU while processing them. 1534 * It is safe to rely on PG_active against the non-LRU pages in here because 1535 * nobody will play with that bit on a non-LRU page. 1536 * 1537 * The downside is that we have to touch page->_count against each page. 1538 * But we had to alter page->flags anyway. 1539 */ 1540 1541 static void move_active_pages_to_lru(struct zone *zone, 1542 struct list_head *list, 1543 enum lru_list lru) 1544 { 1545 unsigned long pgmoved = 0; 1546 struct pagevec pvec; 1547 struct page *page; 1548 1549 pagevec_init(&pvec, 1); 1550 1551 while (!list_empty(list)) { 1552 page = lru_to_page(list); 1553 1554 VM_BUG_ON(PageLRU(page)); 1555 SetPageLRU(page); 1556 1557 list_move(&page->lru, &zone->lru[lru].list); 1558 mem_cgroup_add_lru_list(page, lru); 1559 pgmoved += hpage_nr_pages(page); 1560 1561 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1562 spin_unlock_irq(&zone->lru_lock); 1563 if (buffer_heads_over_limit) 1564 pagevec_strip(&pvec); 1565 __pagevec_release(&pvec); 1566 spin_lock_irq(&zone->lru_lock); 1567 } 1568 } 1569 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1570 if (!is_active_lru(lru)) 1571 __count_vm_events(PGDEACTIVATE, pgmoved); 1572 } 1573 1574 static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1575 struct scan_control *sc, int priority, int file) 1576 { 1577 unsigned long nr_taken; 1578 unsigned long pgscanned; 1579 unsigned long vm_flags; 1580 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1581 LIST_HEAD(l_active); 1582 LIST_HEAD(l_inactive); 1583 struct page *page; 1584 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1585 unsigned long nr_rotated = 0; 1586 1587 lru_add_drain(); 1588 spin_lock_irq(&zone->lru_lock); 1589 if (scanning_global_lru(sc)) { 1590 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1591 &pgscanned, sc->order, 1592 ISOLATE_ACTIVE, zone, 1593 1, file); 1594 zone->pages_scanned += pgscanned; 1595 } else { 1596 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1597 &pgscanned, sc->order, 1598 ISOLATE_ACTIVE, zone, 1599 sc->mem_cgroup, 1, file); 1600 /* 1601 * mem_cgroup_isolate_pages() keeps track of 1602 * scanned pages on its own. 1603 */ 1604 } 1605 1606 reclaim_stat->recent_scanned[file] += nr_taken; 1607 1608 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1609 if (file) 1610 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1611 else 1612 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1613 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1614 spin_unlock_irq(&zone->lru_lock); 1615 1616 while (!list_empty(&l_hold)) { 1617 cond_resched(); 1618 page = lru_to_page(&l_hold); 1619 list_del(&page->lru); 1620 1621 if (unlikely(!page_evictable(page, NULL))) { 1622 putback_lru_page(page); 1623 continue; 1624 } 1625 1626 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1627 nr_rotated += hpage_nr_pages(page); 1628 /* 1629 * Identify referenced, file-backed active pages and 1630 * give them one more trip around the active list. So 1631 * that executable code get better chances to stay in 1632 * memory under moderate memory pressure. Anon pages 1633 * are not likely to be evicted by use-once streaming 1634 * IO, plus JVM can create lots of anon VM_EXEC pages, 1635 * so we ignore them here. 1636 */ 1637 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1638 list_add(&page->lru, &l_active); 1639 continue; 1640 } 1641 } 1642 1643 ClearPageActive(page); /* we are de-activating */ 1644 list_add(&page->lru, &l_inactive); 1645 } 1646 1647 /* 1648 * Move pages back to the lru list. 1649 */ 1650 spin_lock_irq(&zone->lru_lock); 1651 /* 1652 * Count referenced pages from currently used mappings as rotated, 1653 * even though only some of them are actually re-activated. This 1654 * helps balance scan pressure between file and anonymous pages in 1655 * get_scan_ratio. 1656 */ 1657 reclaim_stat->recent_rotated[file] += nr_rotated; 1658 1659 move_active_pages_to_lru(zone, &l_active, 1660 LRU_ACTIVE + file * LRU_FILE); 1661 move_active_pages_to_lru(zone, &l_inactive, 1662 LRU_BASE + file * LRU_FILE); 1663 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1664 spin_unlock_irq(&zone->lru_lock); 1665 } 1666 1667 #ifdef CONFIG_SWAP 1668 static int inactive_anon_is_low_global(struct zone *zone) 1669 { 1670 unsigned long active, inactive; 1671 1672 active = zone_page_state(zone, NR_ACTIVE_ANON); 1673 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1674 1675 if (inactive * zone->inactive_ratio < active) 1676 return 1; 1677 1678 return 0; 1679 } 1680 1681 /** 1682 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1683 * @zone: zone to check 1684 * @sc: scan control of this context 1685 * 1686 * Returns true if the zone does not have enough inactive anon pages, 1687 * meaning some active anon pages need to be deactivated. 1688 */ 1689 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1690 { 1691 int low; 1692 1693 /* 1694 * If we don't have swap space, anonymous page deactivation 1695 * is pointless. 1696 */ 1697 if (!total_swap_pages) 1698 return 0; 1699 1700 if (scanning_global_lru(sc)) 1701 low = inactive_anon_is_low_global(zone); 1702 else 1703 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1704 return low; 1705 } 1706 #else 1707 static inline int inactive_anon_is_low(struct zone *zone, 1708 struct scan_control *sc) 1709 { 1710 return 0; 1711 } 1712 #endif 1713 1714 static int inactive_file_is_low_global(struct zone *zone) 1715 { 1716 unsigned long active, inactive; 1717 1718 active = zone_page_state(zone, NR_ACTIVE_FILE); 1719 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1720 1721 return (active > inactive); 1722 } 1723 1724 /** 1725 * inactive_file_is_low - check if file pages need to be deactivated 1726 * @zone: zone to check 1727 * @sc: scan control of this context 1728 * 1729 * When the system is doing streaming IO, memory pressure here 1730 * ensures that active file pages get deactivated, until more 1731 * than half of the file pages are on the inactive list. 1732 * 1733 * Once we get to that situation, protect the system's working 1734 * set from being evicted by disabling active file page aging. 1735 * 1736 * This uses a different ratio than the anonymous pages, because 1737 * the page cache uses a use-once replacement algorithm. 1738 */ 1739 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1740 { 1741 int low; 1742 1743 if (scanning_global_lru(sc)) 1744 low = inactive_file_is_low_global(zone); 1745 else 1746 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1747 return low; 1748 } 1749 1750 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1751 int file) 1752 { 1753 if (file) 1754 return inactive_file_is_low(zone, sc); 1755 else 1756 return inactive_anon_is_low(zone, sc); 1757 } 1758 1759 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1760 struct zone *zone, struct scan_control *sc, int priority) 1761 { 1762 int file = is_file_lru(lru); 1763 1764 if (is_active_lru(lru)) { 1765 if (inactive_list_is_low(zone, sc, file)) 1766 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1767 return 0; 1768 } 1769 1770 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1771 } 1772 1773 /* 1774 * Determine how aggressively the anon and file LRU lists should be 1775 * scanned. The relative value of each set of LRU lists is determined 1776 * by looking at the fraction of the pages scanned we did rotate back 1777 * onto the active list instead of evict. 1778 * 1779 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1780 */ 1781 static void get_scan_count(struct zone *zone, struct scan_control *sc, 1782 unsigned long *nr, int priority) 1783 { 1784 unsigned long anon, file, free; 1785 unsigned long anon_prio, file_prio; 1786 unsigned long ap, fp; 1787 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1788 u64 fraction[2], denominator; 1789 enum lru_list l; 1790 int noswap = 0; 1791 int force_scan = 0; 1792 1793 1794 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1795 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1796 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1797 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1798 1799 if (((anon + file) >> priority) < SWAP_CLUSTER_MAX) { 1800 /* kswapd does zone balancing and need to scan this zone */ 1801 if (scanning_global_lru(sc) && current_is_kswapd()) 1802 force_scan = 1; 1803 /* memcg may have small limit and need to avoid priority drop */ 1804 if (!scanning_global_lru(sc)) 1805 force_scan = 1; 1806 } 1807 1808 /* If we have no swap space, do not bother scanning anon pages. */ 1809 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1810 noswap = 1; 1811 fraction[0] = 0; 1812 fraction[1] = 1; 1813 denominator = 1; 1814 goto out; 1815 } 1816 1817 if (scanning_global_lru(sc)) { 1818 free = zone_page_state(zone, NR_FREE_PAGES); 1819 /* If we have very few page cache pages, 1820 force-scan anon pages. */ 1821 if (unlikely(file + free <= high_wmark_pages(zone))) { 1822 fraction[0] = 1; 1823 fraction[1] = 0; 1824 denominator = 1; 1825 goto out; 1826 } 1827 } 1828 1829 /* 1830 * With swappiness at 100, anonymous and file have the same priority. 1831 * This scanning priority is essentially the inverse of IO cost. 1832 */ 1833 anon_prio = sc->swappiness; 1834 file_prio = 200 - sc->swappiness; 1835 1836 /* 1837 * OK, so we have swap space and a fair amount of page cache 1838 * pages. We use the recently rotated / recently scanned 1839 * ratios to determine how valuable each cache is. 1840 * 1841 * Because workloads change over time (and to avoid overflow) 1842 * we keep these statistics as a floating average, which ends 1843 * up weighing recent references more than old ones. 1844 * 1845 * anon in [0], file in [1] 1846 */ 1847 spin_lock_irq(&zone->lru_lock); 1848 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1849 reclaim_stat->recent_scanned[0] /= 2; 1850 reclaim_stat->recent_rotated[0] /= 2; 1851 } 1852 1853 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1854 reclaim_stat->recent_scanned[1] /= 2; 1855 reclaim_stat->recent_rotated[1] /= 2; 1856 } 1857 1858 /* 1859 * The amount of pressure on anon vs file pages is inversely 1860 * proportional to the fraction of recently scanned pages on 1861 * each list that were recently referenced and in active use. 1862 */ 1863 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1864 ap /= reclaim_stat->recent_rotated[0] + 1; 1865 1866 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1867 fp /= reclaim_stat->recent_rotated[1] + 1; 1868 spin_unlock_irq(&zone->lru_lock); 1869 1870 fraction[0] = ap; 1871 fraction[1] = fp; 1872 denominator = ap + fp + 1; 1873 out: 1874 for_each_evictable_lru(l) { 1875 int file = is_file_lru(l); 1876 unsigned long scan; 1877 1878 scan = zone_nr_lru_pages(zone, sc, l); 1879 if (priority || noswap) { 1880 scan >>= priority; 1881 scan = div64_u64(scan * fraction[file], denominator); 1882 } 1883 1884 /* 1885 * If zone is small or memcg is small, nr[l] can be 0. 1886 * This results no-scan on this priority and priority drop down. 1887 * For global direct reclaim, it can visit next zone and tend 1888 * not to have problems. For global kswapd, it's for zone 1889 * balancing and it need to scan a small amounts. When using 1890 * memcg, priority drop can cause big latency. So, it's better 1891 * to scan small amount. See may_noscan above. 1892 */ 1893 if (!scan && force_scan) { 1894 if (file) 1895 scan = SWAP_CLUSTER_MAX; 1896 else if (!noswap) 1897 scan = SWAP_CLUSTER_MAX; 1898 } 1899 nr[l] = scan; 1900 } 1901 } 1902 1903 /* 1904 * Reclaim/compaction depends on a number of pages being freed. To avoid 1905 * disruption to the system, a small number of order-0 pages continue to be 1906 * rotated and reclaimed in the normal fashion. However, by the time we get 1907 * back to the allocator and call try_to_compact_zone(), we ensure that 1908 * there are enough free pages for it to be likely successful 1909 */ 1910 static inline bool should_continue_reclaim(struct zone *zone, 1911 unsigned long nr_reclaimed, 1912 unsigned long nr_scanned, 1913 struct scan_control *sc) 1914 { 1915 unsigned long pages_for_compaction; 1916 unsigned long inactive_lru_pages; 1917 1918 /* If not in reclaim/compaction mode, stop */ 1919 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1920 return false; 1921 1922 /* Consider stopping depending on scan and reclaim activity */ 1923 if (sc->gfp_mask & __GFP_REPEAT) { 1924 /* 1925 * For __GFP_REPEAT allocations, stop reclaiming if the 1926 * full LRU list has been scanned and we are still failing 1927 * to reclaim pages. This full LRU scan is potentially 1928 * expensive but a __GFP_REPEAT caller really wants to succeed 1929 */ 1930 if (!nr_reclaimed && !nr_scanned) 1931 return false; 1932 } else { 1933 /* 1934 * For non-__GFP_REPEAT allocations which can presumably 1935 * fail without consequence, stop if we failed to reclaim 1936 * any pages from the last SWAP_CLUSTER_MAX number of 1937 * pages that were scanned. This will return to the 1938 * caller faster at the risk reclaim/compaction and 1939 * the resulting allocation attempt fails 1940 */ 1941 if (!nr_reclaimed) 1942 return false; 1943 } 1944 1945 /* 1946 * If we have not reclaimed enough pages for compaction and the 1947 * inactive lists are large enough, continue reclaiming 1948 */ 1949 pages_for_compaction = (2UL << sc->order); 1950 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1951 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1952 if (sc->nr_reclaimed < pages_for_compaction && 1953 inactive_lru_pages > pages_for_compaction) 1954 return true; 1955 1956 /* If compaction would go ahead or the allocation would succeed, stop */ 1957 switch (compaction_suitable(zone, sc->order)) { 1958 case COMPACT_PARTIAL: 1959 case COMPACT_CONTINUE: 1960 return false; 1961 default: 1962 return true; 1963 } 1964 } 1965 1966 /* 1967 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1968 */ 1969 static void shrink_zone(int priority, struct zone *zone, 1970 struct scan_control *sc) 1971 { 1972 unsigned long nr[NR_LRU_LISTS]; 1973 unsigned long nr_to_scan; 1974 enum lru_list l; 1975 unsigned long nr_reclaimed, nr_scanned; 1976 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1977 1978 restart: 1979 nr_reclaimed = 0; 1980 nr_scanned = sc->nr_scanned; 1981 get_scan_count(zone, sc, nr, priority); 1982 1983 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1984 nr[LRU_INACTIVE_FILE]) { 1985 for_each_evictable_lru(l) { 1986 if (nr[l]) { 1987 nr_to_scan = min_t(unsigned long, 1988 nr[l], SWAP_CLUSTER_MAX); 1989 nr[l] -= nr_to_scan; 1990 1991 nr_reclaimed += shrink_list(l, nr_to_scan, 1992 zone, sc, priority); 1993 } 1994 } 1995 /* 1996 * On large memory systems, scan >> priority can become 1997 * really large. This is fine for the starting priority; 1998 * we want to put equal scanning pressure on each zone. 1999 * However, if the VM has a harder time of freeing pages, 2000 * with multiple processes reclaiming pages, the total 2001 * freeing target can get unreasonably large. 2002 */ 2003 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 2004 break; 2005 } 2006 sc->nr_reclaimed += nr_reclaimed; 2007 2008 /* 2009 * Even if we did not try to evict anon pages at all, we want to 2010 * rebalance the anon lru active/inactive ratio. 2011 */ 2012 if (inactive_anon_is_low(zone, sc)) 2013 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 2014 2015 /* reclaim/compaction might need reclaim to continue */ 2016 if (should_continue_reclaim(zone, nr_reclaimed, 2017 sc->nr_scanned - nr_scanned, sc)) 2018 goto restart; 2019 2020 throttle_vm_writeout(sc->gfp_mask); 2021 } 2022 2023 /* 2024 * This is the direct reclaim path, for page-allocating processes. We only 2025 * try to reclaim pages from zones which will satisfy the caller's allocation 2026 * request. 2027 * 2028 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 2029 * Because: 2030 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 2031 * allocation or 2032 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 2033 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 2034 * zone defense algorithm. 2035 * 2036 * If a zone is deemed to be full of pinned pages then just give it a light 2037 * scan then give up on it. 2038 */ 2039 static void shrink_zones(int priority, struct zonelist *zonelist, 2040 struct scan_control *sc) 2041 { 2042 struct zoneref *z; 2043 struct zone *zone; 2044 unsigned long nr_soft_reclaimed; 2045 unsigned long nr_soft_scanned; 2046 2047 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2048 gfp_zone(sc->gfp_mask), sc->nodemask) { 2049 if (!populated_zone(zone)) 2050 continue; 2051 /* 2052 * Take care memory controller reclaiming has small influence 2053 * to global LRU. 2054 */ 2055 if (scanning_global_lru(sc)) { 2056 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2057 continue; 2058 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2059 continue; /* Let kswapd poll it */ 2060 /* 2061 * This steals pages from memory cgroups over softlimit 2062 * and returns the number of reclaimed pages and 2063 * scanned pages. This works for global memory pressure 2064 * and balancing, not for a memcg's limit. 2065 */ 2066 nr_soft_scanned = 0; 2067 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2068 sc->order, sc->gfp_mask, 2069 &nr_soft_scanned); 2070 sc->nr_reclaimed += nr_soft_reclaimed; 2071 sc->nr_scanned += nr_soft_scanned; 2072 /* need some check for avoid more shrink_zone() */ 2073 } 2074 2075 shrink_zone(priority, zone, sc); 2076 } 2077 } 2078 2079 static bool zone_reclaimable(struct zone *zone) 2080 { 2081 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 2082 } 2083 2084 /* All zones in zonelist are unreclaimable? */ 2085 static bool all_unreclaimable(struct zonelist *zonelist, 2086 struct scan_control *sc) 2087 { 2088 struct zoneref *z; 2089 struct zone *zone; 2090 2091 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2092 gfp_zone(sc->gfp_mask), sc->nodemask) { 2093 if (!populated_zone(zone)) 2094 continue; 2095 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2096 continue; 2097 if (!zone->all_unreclaimable) 2098 return false; 2099 } 2100 2101 return true; 2102 } 2103 2104 /* 2105 * This is the main entry point to direct page reclaim. 2106 * 2107 * If a full scan of the inactive list fails to free enough memory then we 2108 * are "out of memory" and something needs to be killed. 2109 * 2110 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2111 * high - the zone may be full of dirty or under-writeback pages, which this 2112 * caller can't do much about. We kick the writeback threads and take explicit 2113 * naps in the hope that some of these pages can be written. But if the 2114 * allocating task holds filesystem locks which prevent writeout this might not 2115 * work, and the allocation attempt will fail. 2116 * 2117 * returns: 0, if no pages reclaimed 2118 * else, the number of pages reclaimed 2119 */ 2120 static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2121 struct scan_control *sc, 2122 struct shrink_control *shrink) 2123 { 2124 int priority; 2125 unsigned long total_scanned = 0; 2126 struct reclaim_state *reclaim_state = current->reclaim_state; 2127 struct zoneref *z; 2128 struct zone *zone; 2129 unsigned long writeback_threshold; 2130 2131 get_mems_allowed(); 2132 delayacct_freepages_start(); 2133 2134 if (scanning_global_lru(sc)) 2135 count_vm_event(ALLOCSTALL); 2136 2137 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2138 sc->nr_scanned = 0; 2139 if (!priority) 2140 disable_swap_token(sc->mem_cgroup); 2141 shrink_zones(priority, zonelist, sc); 2142 /* 2143 * Don't shrink slabs when reclaiming memory from 2144 * over limit cgroups 2145 */ 2146 if (scanning_global_lru(sc)) { 2147 unsigned long lru_pages = 0; 2148 for_each_zone_zonelist(zone, z, zonelist, 2149 gfp_zone(sc->gfp_mask)) { 2150 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2151 continue; 2152 2153 lru_pages += zone_reclaimable_pages(zone); 2154 } 2155 2156 shrink_slab(shrink, sc->nr_scanned, lru_pages); 2157 if (reclaim_state) { 2158 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2159 reclaim_state->reclaimed_slab = 0; 2160 } 2161 } 2162 total_scanned += sc->nr_scanned; 2163 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2164 goto out; 2165 2166 /* 2167 * Try to write back as many pages as we just scanned. This 2168 * tends to cause slow streaming writers to write data to the 2169 * disk smoothly, at the dirtying rate, which is nice. But 2170 * that's undesirable in laptop mode, where we *want* lumpy 2171 * writeout. So in laptop mode, write out the whole world. 2172 */ 2173 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2174 if (total_scanned > writeback_threshold) { 2175 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2176 sc->may_writepage = 1; 2177 } 2178 2179 /* Take a nap, wait for some writeback to complete */ 2180 if (!sc->hibernation_mode && sc->nr_scanned && 2181 priority < DEF_PRIORITY - 2) { 2182 struct zone *preferred_zone; 2183 2184 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2185 &cpuset_current_mems_allowed, 2186 &preferred_zone); 2187 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2188 } 2189 } 2190 2191 out: 2192 delayacct_freepages_end(); 2193 put_mems_allowed(); 2194 2195 if (sc->nr_reclaimed) 2196 return sc->nr_reclaimed; 2197 2198 /* 2199 * As hibernation is going on, kswapd is freezed so that it can't mark 2200 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2201 * check. 2202 */ 2203 if (oom_killer_disabled) 2204 return 0; 2205 2206 /* top priority shrink_zones still had more to do? don't OOM, then */ 2207 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2208 return 1; 2209 2210 return 0; 2211 } 2212 2213 unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2214 gfp_t gfp_mask, nodemask_t *nodemask) 2215 { 2216 unsigned long nr_reclaimed; 2217 struct scan_control sc = { 2218 .gfp_mask = gfp_mask, 2219 .may_writepage = !laptop_mode, 2220 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2221 .may_unmap = 1, 2222 .may_swap = 1, 2223 .swappiness = vm_swappiness, 2224 .order = order, 2225 .mem_cgroup = NULL, 2226 .nodemask = nodemask, 2227 }; 2228 struct shrink_control shrink = { 2229 .gfp_mask = sc.gfp_mask, 2230 }; 2231 2232 trace_mm_vmscan_direct_reclaim_begin(order, 2233 sc.may_writepage, 2234 gfp_mask); 2235 2236 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2237 2238 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2239 2240 return nr_reclaimed; 2241 } 2242 2243 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 2244 2245 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2246 gfp_t gfp_mask, bool noswap, 2247 unsigned int swappiness, 2248 struct zone *zone, 2249 unsigned long *nr_scanned) 2250 { 2251 struct scan_control sc = { 2252 .nr_scanned = 0, 2253 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2254 .may_writepage = !laptop_mode, 2255 .may_unmap = 1, 2256 .may_swap = !noswap, 2257 .swappiness = swappiness, 2258 .order = 0, 2259 .mem_cgroup = mem, 2260 }; 2261 2262 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2263 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2264 2265 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2266 sc.may_writepage, 2267 sc.gfp_mask); 2268 2269 /* 2270 * NOTE: Although we can get the priority field, using it 2271 * here is not a good idea, since it limits the pages we can scan. 2272 * if we don't reclaim here, the shrink_zone from balance_pgdat 2273 * will pick up pages from other mem cgroup's as well. We hack 2274 * the priority and make it zero. 2275 */ 2276 shrink_zone(0, zone, &sc); 2277 2278 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2279 2280 *nr_scanned = sc.nr_scanned; 2281 return sc.nr_reclaimed; 2282 } 2283 2284 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2285 gfp_t gfp_mask, 2286 bool noswap, 2287 unsigned int swappiness) 2288 { 2289 struct zonelist *zonelist; 2290 unsigned long nr_reclaimed; 2291 int nid; 2292 struct scan_control sc = { 2293 .may_writepage = !laptop_mode, 2294 .may_unmap = 1, 2295 .may_swap = !noswap, 2296 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2297 .swappiness = swappiness, 2298 .order = 0, 2299 .mem_cgroup = mem_cont, 2300 .nodemask = NULL, /* we don't care the placement */ 2301 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2302 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 2303 }; 2304 struct shrink_control shrink = { 2305 .gfp_mask = sc.gfp_mask, 2306 }; 2307 2308 /* 2309 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't 2310 * take care of from where we get pages. So the node where we start the 2311 * scan does not need to be the current node. 2312 */ 2313 nid = mem_cgroup_select_victim_node(mem_cont); 2314 2315 zonelist = NODE_DATA(nid)->node_zonelists; 2316 2317 trace_mm_vmscan_memcg_reclaim_begin(0, 2318 sc.may_writepage, 2319 sc.gfp_mask); 2320 2321 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2322 2323 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2324 2325 return nr_reclaimed; 2326 } 2327 #endif 2328 2329 /* 2330 * pgdat_balanced is used when checking if a node is balanced for high-order 2331 * allocations. Only zones that meet watermarks and are in a zone allowed 2332 * by the callers classzone_idx are added to balanced_pages. The total of 2333 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2334 * for the node to be considered balanced. Forcing all zones to be balanced 2335 * for high orders can cause excessive reclaim when there are imbalanced zones. 2336 * The choice of 25% is due to 2337 * o a 16M DMA zone that is balanced will not balance a zone on any 2338 * reasonable sized machine 2339 * o On all other machines, the top zone must be at least a reasonable 2340 * percentage of the middle zones. For example, on 32-bit x86, highmem 2341 * would need to be at least 256M for it to be balance a whole node. 2342 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2343 * to balance a node on its own. These seemed like reasonable ratios. 2344 */ 2345 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2346 int classzone_idx) 2347 { 2348 unsigned long present_pages = 0; 2349 int i; 2350 2351 for (i = 0; i <= classzone_idx; i++) 2352 present_pages += pgdat->node_zones[i].present_pages; 2353 2354 /* A special case here: if zone has no page, we think it's balanced */ 2355 return balanced_pages >= (present_pages >> 2); 2356 } 2357 2358 /* is kswapd sleeping prematurely? */ 2359 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2360 int classzone_idx) 2361 { 2362 int i; 2363 unsigned long balanced = 0; 2364 bool all_zones_ok = true; 2365 2366 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2367 if (remaining) 2368 return true; 2369 2370 /* Check the watermark levels */ 2371 for (i = 0; i <= classzone_idx; i++) { 2372 struct zone *zone = pgdat->node_zones + i; 2373 2374 if (!populated_zone(zone)) 2375 continue; 2376 2377 /* 2378 * balance_pgdat() skips over all_unreclaimable after 2379 * DEF_PRIORITY. Effectively, it considers them balanced so 2380 * they must be considered balanced here as well if kswapd 2381 * is to sleep 2382 */ 2383 if (zone->all_unreclaimable) { 2384 balanced += zone->present_pages; 2385 continue; 2386 } 2387 2388 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2389 i, 0)) 2390 all_zones_ok = false; 2391 else 2392 balanced += zone->present_pages; 2393 } 2394 2395 /* 2396 * For high-order requests, the balanced zones must contain at least 2397 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2398 * must be balanced 2399 */ 2400 if (order) 2401 return !pgdat_balanced(pgdat, balanced, classzone_idx); 2402 else 2403 return !all_zones_ok; 2404 } 2405 2406 /* 2407 * For kswapd, balance_pgdat() will work across all this node's zones until 2408 * they are all at high_wmark_pages(zone). 2409 * 2410 * Returns the final order kswapd was reclaiming at 2411 * 2412 * There is special handling here for zones which are full of pinned pages. 2413 * This can happen if the pages are all mlocked, or if they are all used by 2414 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2415 * What we do is to detect the case where all pages in the zone have been 2416 * scanned twice and there has been zero successful reclaim. Mark the zone as 2417 * dead and from now on, only perform a short scan. Basically we're polling 2418 * the zone for when the problem goes away. 2419 * 2420 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2421 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2422 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2423 * lower zones regardless of the number of free pages in the lower zones. This 2424 * interoperates with the page allocator fallback scheme to ensure that aging 2425 * of pages is balanced across the zones. 2426 */ 2427 static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2428 int *classzone_idx) 2429 { 2430 int all_zones_ok; 2431 unsigned long balanced; 2432 int priority; 2433 int i; 2434 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2435 unsigned long total_scanned; 2436 struct reclaim_state *reclaim_state = current->reclaim_state; 2437 unsigned long nr_soft_reclaimed; 2438 unsigned long nr_soft_scanned; 2439 struct scan_control sc = { 2440 .gfp_mask = GFP_KERNEL, 2441 .may_unmap = 1, 2442 .may_swap = 1, 2443 /* 2444 * kswapd doesn't want to be bailed out while reclaim. because 2445 * we want to put equal scanning pressure on each zone. 2446 */ 2447 .nr_to_reclaim = ULONG_MAX, 2448 .swappiness = vm_swappiness, 2449 .order = order, 2450 .mem_cgroup = NULL, 2451 }; 2452 struct shrink_control shrink = { 2453 .gfp_mask = sc.gfp_mask, 2454 }; 2455 loop_again: 2456 total_scanned = 0; 2457 sc.nr_reclaimed = 0; 2458 sc.may_writepage = !laptop_mode; 2459 count_vm_event(PAGEOUTRUN); 2460 2461 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2462 unsigned long lru_pages = 0; 2463 int has_under_min_watermark_zone = 0; 2464 2465 /* The swap token gets in the way of swapout... */ 2466 if (!priority) 2467 disable_swap_token(NULL); 2468 2469 all_zones_ok = 1; 2470 balanced = 0; 2471 2472 /* 2473 * Scan in the highmem->dma direction for the highest 2474 * zone which needs scanning 2475 */ 2476 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2477 struct zone *zone = pgdat->node_zones + i; 2478 2479 if (!populated_zone(zone)) 2480 continue; 2481 2482 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2483 continue; 2484 2485 /* 2486 * Do some background aging of the anon list, to give 2487 * pages a chance to be referenced before reclaiming. 2488 */ 2489 if (inactive_anon_is_low(zone, &sc)) 2490 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2491 &sc, priority, 0); 2492 2493 if (!zone_watermark_ok_safe(zone, order, 2494 high_wmark_pages(zone), 0, 0)) { 2495 end_zone = i; 2496 break; 2497 } 2498 } 2499 if (i < 0) 2500 goto out; 2501 2502 for (i = 0; i <= end_zone; i++) { 2503 struct zone *zone = pgdat->node_zones + i; 2504 2505 lru_pages += zone_reclaimable_pages(zone); 2506 } 2507 2508 /* 2509 * Now scan the zone in the dma->highmem direction, stopping 2510 * at the last zone which needs scanning. 2511 * 2512 * We do this because the page allocator works in the opposite 2513 * direction. This prevents the page allocator from allocating 2514 * pages behind kswapd's direction of progress, which would 2515 * cause too much scanning of the lower zones. 2516 */ 2517 for (i = 0; i <= end_zone; i++) { 2518 struct zone *zone = pgdat->node_zones + i; 2519 int nr_slab; 2520 unsigned long balance_gap; 2521 2522 if (!populated_zone(zone)) 2523 continue; 2524 2525 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2526 continue; 2527 2528 sc.nr_scanned = 0; 2529 2530 nr_soft_scanned = 0; 2531 /* 2532 * Call soft limit reclaim before calling shrink_zone. 2533 */ 2534 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2535 order, sc.gfp_mask, 2536 &nr_soft_scanned); 2537 sc.nr_reclaimed += nr_soft_reclaimed; 2538 total_scanned += nr_soft_scanned; 2539 2540 /* 2541 * We put equal pressure on every zone, unless 2542 * one zone has way too many pages free 2543 * already. The "too many pages" is defined 2544 * as the high wmark plus a "gap" where the 2545 * gap is either the low watermark or 1% 2546 * of the zone, whichever is smaller. 2547 */ 2548 balance_gap = min(low_wmark_pages(zone), 2549 (zone->present_pages + 2550 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2551 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2552 if (!zone_watermark_ok_safe(zone, order, 2553 high_wmark_pages(zone) + balance_gap, 2554 end_zone, 0)) { 2555 shrink_zone(priority, zone, &sc); 2556 2557 reclaim_state->reclaimed_slab = 0; 2558 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); 2559 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2560 total_scanned += sc.nr_scanned; 2561 2562 if (nr_slab == 0 && !zone_reclaimable(zone)) 2563 zone->all_unreclaimable = 1; 2564 } 2565 2566 /* 2567 * If we've done a decent amount of scanning and 2568 * the reclaim ratio is low, start doing writepage 2569 * even in laptop mode 2570 */ 2571 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2572 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2573 sc.may_writepage = 1; 2574 2575 if (zone->all_unreclaimable) { 2576 if (end_zone && end_zone == i) 2577 end_zone--; 2578 continue; 2579 } 2580 2581 if (!zone_watermark_ok_safe(zone, order, 2582 high_wmark_pages(zone), end_zone, 0)) { 2583 all_zones_ok = 0; 2584 /* 2585 * We are still under min water mark. This 2586 * means that we have a GFP_ATOMIC allocation 2587 * failure risk. Hurry up! 2588 */ 2589 if (!zone_watermark_ok_safe(zone, order, 2590 min_wmark_pages(zone), end_zone, 0)) 2591 has_under_min_watermark_zone = 1; 2592 } else { 2593 /* 2594 * If a zone reaches its high watermark, 2595 * consider it to be no longer congested. It's 2596 * possible there are dirty pages backed by 2597 * congested BDIs but as pressure is relieved, 2598 * spectulatively avoid congestion waits 2599 */ 2600 zone_clear_flag(zone, ZONE_CONGESTED); 2601 if (i <= *classzone_idx) 2602 balanced += zone->present_pages; 2603 } 2604 2605 } 2606 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2607 break; /* kswapd: all done */ 2608 /* 2609 * OK, kswapd is getting into trouble. Take a nap, then take 2610 * another pass across the zones. 2611 */ 2612 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2613 if (has_under_min_watermark_zone) 2614 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2615 else 2616 congestion_wait(BLK_RW_ASYNC, HZ/10); 2617 } 2618 2619 /* 2620 * We do this so kswapd doesn't build up large priorities for 2621 * example when it is freeing in parallel with allocators. It 2622 * matches the direct reclaim path behaviour in terms of impact 2623 * on zone->*_priority. 2624 */ 2625 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2626 break; 2627 } 2628 out: 2629 2630 /* 2631 * order-0: All zones must meet high watermark for a balanced node 2632 * high-order: Balanced zones must make up at least 25% of the node 2633 * for the node to be balanced 2634 */ 2635 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2636 cond_resched(); 2637 2638 try_to_freeze(); 2639 2640 /* 2641 * Fragmentation may mean that the system cannot be 2642 * rebalanced for high-order allocations in all zones. 2643 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2644 * it means the zones have been fully scanned and are still 2645 * not balanced. For high-order allocations, there is 2646 * little point trying all over again as kswapd may 2647 * infinite loop. 2648 * 2649 * Instead, recheck all watermarks at order-0 as they 2650 * are the most important. If watermarks are ok, kswapd will go 2651 * back to sleep. High-order users can still perform direct 2652 * reclaim if they wish. 2653 */ 2654 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2655 order = sc.order = 0; 2656 2657 goto loop_again; 2658 } 2659 2660 /* 2661 * If kswapd was reclaiming at a higher order, it has the option of 2662 * sleeping without all zones being balanced. Before it does, it must 2663 * ensure that the watermarks for order-0 on *all* zones are met and 2664 * that the congestion flags are cleared. The congestion flag must 2665 * be cleared as kswapd is the only mechanism that clears the flag 2666 * and it is potentially going to sleep here. 2667 */ 2668 if (order) { 2669 for (i = 0; i <= end_zone; i++) { 2670 struct zone *zone = pgdat->node_zones + i; 2671 2672 if (!populated_zone(zone)) 2673 continue; 2674 2675 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2676 continue; 2677 2678 /* Confirm the zone is balanced for order-0 */ 2679 if (!zone_watermark_ok(zone, 0, 2680 high_wmark_pages(zone), 0, 0)) { 2681 order = sc.order = 0; 2682 goto loop_again; 2683 } 2684 2685 /* If balanced, clear the congested flag */ 2686 zone_clear_flag(zone, ZONE_CONGESTED); 2687 } 2688 } 2689 2690 /* 2691 * Return the order we were reclaiming at so sleeping_prematurely() 2692 * makes a decision on the order we were last reclaiming at. However, 2693 * if another caller entered the allocator slow path while kswapd 2694 * was awake, order will remain at the higher level 2695 */ 2696 *classzone_idx = end_zone; 2697 return order; 2698 } 2699 2700 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2701 { 2702 long remaining = 0; 2703 DEFINE_WAIT(wait); 2704 2705 if (freezing(current) || kthread_should_stop()) 2706 return; 2707 2708 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2709 2710 /* Try to sleep for a short interval */ 2711 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2712 remaining = schedule_timeout(HZ/10); 2713 finish_wait(&pgdat->kswapd_wait, &wait); 2714 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2715 } 2716 2717 /* 2718 * After a short sleep, check if it was a premature sleep. If not, then 2719 * go fully to sleep until explicitly woken up. 2720 */ 2721 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2722 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2723 2724 /* 2725 * vmstat counters are not perfectly accurate and the estimated 2726 * value for counters such as NR_FREE_PAGES can deviate from the 2727 * true value by nr_online_cpus * threshold. To avoid the zone 2728 * watermarks being breached while under pressure, we reduce the 2729 * per-cpu vmstat threshold while kswapd is awake and restore 2730 * them before going back to sleep. 2731 */ 2732 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2733 schedule(); 2734 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2735 } else { 2736 if (remaining) 2737 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2738 else 2739 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2740 } 2741 finish_wait(&pgdat->kswapd_wait, &wait); 2742 } 2743 2744 /* 2745 * The background pageout daemon, started as a kernel thread 2746 * from the init process. 2747 * 2748 * This basically trickles out pages so that we have _some_ 2749 * free memory available even if there is no other activity 2750 * that frees anything up. This is needed for things like routing 2751 * etc, where we otherwise might have all activity going on in 2752 * asynchronous contexts that cannot page things out. 2753 * 2754 * If there are applications that are active memory-allocators 2755 * (most normal use), this basically shouldn't matter. 2756 */ 2757 static int kswapd(void *p) 2758 { 2759 unsigned long order, new_order; 2760 int classzone_idx, new_classzone_idx; 2761 pg_data_t *pgdat = (pg_data_t*)p; 2762 struct task_struct *tsk = current; 2763 2764 struct reclaim_state reclaim_state = { 2765 .reclaimed_slab = 0, 2766 }; 2767 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2768 2769 lockdep_set_current_reclaim_state(GFP_KERNEL); 2770 2771 if (!cpumask_empty(cpumask)) 2772 set_cpus_allowed_ptr(tsk, cpumask); 2773 current->reclaim_state = &reclaim_state; 2774 2775 /* 2776 * Tell the memory management that we're a "memory allocator", 2777 * and that if we need more memory we should get access to it 2778 * regardless (see "__alloc_pages()"). "kswapd" should 2779 * never get caught in the normal page freeing logic. 2780 * 2781 * (Kswapd normally doesn't need memory anyway, but sometimes 2782 * you need a small amount of memory in order to be able to 2783 * page out something else, and this flag essentially protects 2784 * us from recursively trying to free more memory as we're 2785 * trying to free the first piece of memory in the first place). 2786 */ 2787 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2788 set_freezable(); 2789 2790 order = new_order = 0; 2791 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; 2792 for ( ; ; ) { 2793 int ret; 2794 2795 /* 2796 * If the last balance_pgdat was unsuccessful it's unlikely a 2797 * new request of a similar or harder type will succeed soon 2798 * so consider going to sleep on the basis we reclaimed at 2799 */ 2800 if (classzone_idx >= new_classzone_idx && order == new_order) { 2801 new_order = pgdat->kswapd_max_order; 2802 new_classzone_idx = pgdat->classzone_idx; 2803 pgdat->kswapd_max_order = 0; 2804 pgdat->classzone_idx = pgdat->nr_zones - 1; 2805 } 2806 2807 if (order < new_order || classzone_idx > new_classzone_idx) { 2808 /* 2809 * Don't sleep if someone wants a larger 'order' 2810 * allocation or has tigher zone constraints 2811 */ 2812 order = new_order; 2813 classzone_idx = new_classzone_idx; 2814 } else { 2815 kswapd_try_to_sleep(pgdat, order, classzone_idx); 2816 order = pgdat->kswapd_max_order; 2817 classzone_idx = pgdat->classzone_idx; 2818 pgdat->kswapd_max_order = 0; 2819 pgdat->classzone_idx = pgdat->nr_zones - 1; 2820 } 2821 2822 ret = try_to_freeze(); 2823 if (kthread_should_stop()) 2824 break; 2825 2826 /* 2827 * We can speed up thawing tasks if we don't call balance_pgdat 2828 * after returning from the refrigerator 2829 */ 2830 if (!ret) { 2831 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2832 order = balance_pgdat(pgdat, order, &classzone_idx); 2833 } 2834 } 2835 return 0; 2836 } 2837 2838 /* 2839 * A zone is low on free memory, so wake its kswapd task to service it. 2840 */ 2841 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2842 { 2843 pg_data_t *pgdat; 2844 2845 if (!populated_zone(zone)) 2846 return; 2847 2848 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2849 return; 2850 pgdat = zone->zone_pgdat; 2851 if (pgdat->kswapd_max_order < order) { 2852 pgdat->kswapd_max_order = order; 2853 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2854 } 2855 if (!waitqueue_active(&pgdat->kswapd_wait)) 2856 return; 2857 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2858 return; 2859 2860 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2861 wake_up_interruptible(&pgdat->kswapd_wait); 2862 } 2863 2864 /* 2865 * The reclaimable count would be mostly accurate. 2866 * The less reclaimable pages may be 2867 * - mlocked pages, which will be moved to unevictable list when encountered 2868 * - mapped pages, which may require several travels to be reclaimed 2869 * - dirty pages, which is not "instantly" reclaimable 2870 */ 2871 unsigned long global_reclaimable_pages(void) 2872 { 2873 int nr; 2874 2875 nr = global_page_state(NR_ACTIVE_FILE) + 2876 global_page_state(NR_INACTIVE_FILE); 2877 2878 if (nr_swap_pages > 0) 2879 nr += global_page_state(NR_ACTIVE_ANON) + 2880 global_page_state(NR_INACTIVE_ANON); 2881 2882 return nr; 2883 } 2884 2885 unsigned long zone_reclaimable_pages(struct zone *zone) 2886 { 2887 int nr; 2888 2889 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2890 zone_page_state(zone, NR_INACTIVE_FILE); 2891 2892 if (nr_swap_pages > 0) 2893 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2894 zone_page_state(zone, NR_INACTIVE_ANON); 2895 2896 return nr; 2897 } 2898 2899 #ifdef CONFIG_HIBERNATION 2900 /* 2901 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2902 * freed pages. 2903 * 2904 * Rather than trying to age LRUs the aim is to preserve the overall 2905 * LRU order by reclaiming preferentially 2906 * inactive > active > active referenced > active mapped 2907 */ 2908 unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2909 { 2910 struct reclaim_state reclaim_state; 2911 struct scan_control sc = { 2912 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2913 .may_swap = 1, 2914 .may_unmap = 1, 2915 .may_writepage = 1, 2916 .nr_to_reclaim = nr_to_reclaim, 2917 .hibernation_mode = 1, 2918 .swappiness = vm_swappiness, 2919 .order = 0, 2920 }; 2921 struct shrink_control shrink = { 2922 .gfp_mask = sc.gfp_mask, 2923 }; 2924 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2925 struct task_struct *p = current; 2926 unsigned long nr_reclaimed; 2927 2928 p->flags |= PF_MEMALLOC; 2929 lockdep_set_current_reclaim_state(sc.gfp_mask); 2930 reclaim_state.reclaimed_slab = 0; 2931 p->reclaim_state = &reclaim_state; 2932 2933 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2934 2935 p->reclaim_state = NULL; 2936 lockdep_clear_current_reclaim_state(); 2937 p->flags &= ~PF_MEMALLOC; 2938 2939 return nr_reclaimed; 2940 } 2941 #endif /* CONFIG_HIBERNATION */ 2942 2943 /* It's optimal to keep kswapds on the same CPUs as their memory, but 2944 not required for correctness. So if the last cpu in a node goes 2945 away, we get changed to run anywhere: as the first one comes back, 2946 restore their cpu bindings. */ 2947 static int __devinit cpu_callback(struct notifier_block *nfb, 2948 unsigned long action, void *hcpu) 2949 { 2950 int nid; 2951 2952 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2953 for_each_node_state(nid, N_HIGH_MEMORY) { 2954 pg_data_t *pgdat = NODE_DATA(nid); 2955 const struct cpumask *mask; 2956 2957 mask = cpumask_of_node(pgdat->node_id); 2958 2959 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2960 /* One of our CPUs online: restore mask */ 2961 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2962 } 2963 } 2964 return NOTIFY_OK; 2965 } 2966 2967 /* 2968 * This kswapd start function will be called by init and node-hot-add. 2969 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2970 */ 2971 int kswapd_run(int nid) 2972 { 2973 pg_data_t *pgdat = NODE_DATA(nid); 2974 int ret = 0; 2975 2976 if (pgdat->kswapd) 2977 return 0; 2978 2979 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2980 if (IS_ERR(pgdat->kswapd)) { 2981 /* failure at boot is fatal */ 2982 BUG_ON(system_state == SYSTEM_BOOTING); 2983 printk("Failed to start kswapd on node %d\n",nid); 2984 ret = -1; 2985 } 2986 return ret; 2987 } 2988 2989 /* 2990 * Called by memory hotplug when all memory in a node is offlined. 2991 */ 2992 void kswapd_stop(int nid) 2993 { 2994 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2995 2996 if (kswapd) 2997 kthread_stop(kswapd); 2998 } 2999 3000 static int __init kswapd_init(void) 3001 { 3002 int nid; 3003 3004 swap_setup(); 3005 for_each_node_state(nid, N_HIGH_MEMORY) 3006 kswapd_run(nid); 3007 hotcpu_notifier(cpu_callback, 0); 3008 return 0; 3009 } 3010 3011 module_init(kswapd_init) 3012 3013 #ifdef CONFIG_NUMA 3014 /* 3015 * Zone reclaim mode 3016 * 3017 * If non-zero call zone_reclaim when the number of free pages falls below 3018 * the watermarks. 3019 */ 3020 int zone_reclaim_mode __read_mostly; 3021 3022 #define RECLAIM_OFF 0 3023 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 3024 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 3025 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 3026 3027 /* 3028 * Priority for ZONE_RECLAIM. This determines the fraction of pages 3029 * of a node considered for each zone_reclaim. 4 scans 1/16th of 3030 * a zone. 3031 */ 3032 #define ZONE_RECLAIM_PRIORITY 4 3033 3034 /* 3035 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 3036 * occur. 3037 */ 3038 int sysctl_min_unmapped_ratio = 1; 3039 3040 /* 3041 * If the number of slab pages in a zone grows beyond this percentage then 3042 * slab reclaim needs to occur. 3043 */ 3044 int sysctl_min_slab_ratio = 5; 3045 3046 static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 3047 { 3048 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 3049 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 3050 zone_page_state(zone, NR_ACTIVE_FILE); 3051 3052 /* 3053 * It's possible for there to be more file mapped pages than 3054 * accounted for by the pages on the file LRU lists because 3055 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 3056 */ 3057 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 3058 } 3059 3060 /* Work out how many page cache pages we can reclaim in this reclaim_mode */ 3061 static long zone_pagecache_reclaimable(struct zone *zone) 3062 { 3063 long nr_pagecache_reclaimable; 3064 long delta = 0; 3065 3066 /* 3067 * If RECLAIM_SWAP is set, then all file pages are considered 3068 * potentially reclaimable. Otherwise, we have to worry about 3069 * pages like swapcache and zone_unmapped_file_pages() provides 3070 * a better estimate 3071 */ 3072 if (zone_reclaim_mode & RECLAIM_SWAP) 3073 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 3074 else 3075 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 3076 3077 /* If we can't clean pages, remove dirty pages from consideration */ 3078 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 3079 delta += zone_page_state(zone, NR_FILE_DIRTY); 3080 3081 /* Watch for any possible underflows due to delta */ 3082 if (unlikely(delta > nr_pagecache_reclaimable)) 3083 delta = nr_pagecache_reclaimable; 3084 3085 return nr_pagecache_reclaimable - delta; 3086 } 3087 3088 /* 3089 * Try to free up some pages from this zone through reclaim. 3090 */ 3091 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3092 { 3093 /* Minimum pages needed in order to stay on node */ 3094 const unsigned long nr_pages = 1 << order; 3095 struct task_struct *p = current; 3096 struct reclaim_state reclaim_state; 3097 int priority; 3098 struct scan_control sc = { 3099 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 3100 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 3101 .may_swap = 1, 3102 .nr_to_reclaim = max_t(unsigned long, nr_pages, 3103 SWAP_CLUSTER_MAX), 3104 .gfp_mask = gfp_mask, 3105 .swappiness = vm_swappiness, 3106 .order = order, 3107 }; 3108 struct shrink_control shrink = { 3109 .gfp_mask = sc.gfp_mask, 3110 }; 3111 unsigned long nr_slab_pages0, nr_slab_pages1; 3112 3113 cond_resched(); 3114 /* 3115 * We need to be able to allocate from the reserves for RECLAIM_SWAP 3116 * and we also need to be able to write out pages for RECLAIM_WRITE 3117 * and RECLAIM_SWAP. 3118 */ 3119 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 3120 lockdep_set_current_reclaim_state(gfp_mask); 3121 reclaim_state.reclaimed_slab = 0; 3122 p->reclaim_state = &reclaim_state; 3123 3124 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 3125 /* 3126 * Free memory by calling shrink zone with increasing 3127 * priorities until we have enough memory freed. 3128 */ 3129 priority = ZONE_RECLAIM_PRIORITY; 3130 do { 3131 shrink_zone(priority, zone, &sc); 3132 priority--; 3133 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 3134 } 3135 3136 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3137 if (nr_slab_pages0 > zone->min_slab_pages) { 3138 /* 3139 * shrink_slab() does not currently allow us to determine how 3140 * many pages were freed in this zone. So we take the current 3141 * number of slab pages and shake the slab until it is reduced 3142 * by the same nr_pages that we used for reclaiming unmapped 3143 * pages. 3144 * 3145 * Note that shrink_slab will free memory on all zones and may 3146 * take a long time. 3147 */ 3148 for (;;) { 3149 unsigned long lru_pages = zone_reclaimable_pages(zone); 3150 3151 /* No reclaimable slab or very low memory pressure */ 3152 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) 3153 break; 3154 3155 /* Freed enough memory */ 3156 nr_slab_pages1 = zone_page_state(zone, 3157 NR_SLAB_RECLAIMABLE); 3158 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3159 break; 3160 } 3161 3162 /* 3163 * Update nr_reclaimed by the number of slab pages we 3164 * reclaimed from this zone. 3165 */ 3166 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3167 if (nr_slab_pages1 < nr_slab_pages0) 3168 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3169 } 3170 3171 p->reclaim_state = NULL; 3172 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3173 lockdep_clear_current_reclaim_state(); 3174 return sc.nr_reclaimed >= nr_pages; 3175 } 3176 3177 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3178 { 3179 int node_id; 3180 int ret; 3181 3182 /* 3183 * Zone reclaim reclaims unmapped file backed pages and 3184 * slab pages if we are over the defined limits. 3185 * 3186 * A small portion of unmapped file backed pages is needed for 3187 * file I/O otherwise pages read by file I/O will be immediately 3188 * thrown out if the zone is overallocated. So we do not reclaim 3189 * if less than a specified percentage of the zone is used by 3190 * unmapped file backed pages. 3191 */ 3192 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3193 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3194 return ZONE_RECLAIM_FULL; 3195 3196 if (zone->all_unreclaimable) 3197 return ZONE_RECLAIM_FULL; 3198 3199 /* 3200 * Do not scan if the allocation should not be delayed. 3201 */ 3202 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3203 return ZONE_RECLAIM_NOSCAN; 3204 3205 /* 3206 * Only run zone reclaim on the local zone or on zones that do not 3207 * have associated processors. This will favor the local processor 3208 * over remote processors and spread off node memory allocations 3209 * as wide as possible. 3210 */ 3211 node_id = zone_to_nid(zone); 3212 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3213 return ZONE_RECLAIM_NOSCAN; 3214 3215 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3216 return ZONE_RECLAIM_NOSCAN; 3217 3218 ret = __zone_reclaim(zone, gfp_mask, order); 3219 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3220 3221 if (!ret) 3222 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3223 3224 return ret; 3225 } 3226 #endif 3227 3228 /* 3229 * page_evictable - test whether a page is evictable 3230 * @page: the page to test 3231 * @vma: the VMA in which the page is or will be mapped, may be NULL 3232 * 3233 * Test whether page is evictable--i.e., should be placed on active/inactive 3234 * lists vs unevictable list. The vma argument is !NULL when called from the 3235 * fault path to determine how to instantate a new page. 3236 * 3237 * Reasons page might not be evictable: 3238 * (1) page's mapping marked unevictable 3239 * (2) page is part of an mlocked VMA 3240 * 3241 */ 3242 int page_evictable(struct page *page, struct vm_area_struct *vma) 3243 { 3244 3245 if (mapping_unevictable(page_mapping(page))) 3246 return 0; 3247 3248 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3249 return 0; 3250 3251 return 1; 3252 } 3253 3254 /** 3255 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3256 * @page: page to check evictability and move to appropriate lru list 3257 * @zone: zone page is in 3258 * 3259 * Checks a page for evictability and moves the page to the appropriate 3260 * zone lru list. 3261 * 3262 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3263 * have PageUnevictable set. 3264 */ 3265 static void check_move_unevictable_page(struct page *page, struct zone *zone) 3266 { 3267 VM_BUG_ON(PageActive(page)); 3268 3269 retry: 3270 ClearPageUnevictable(page); 3271 if (page_evictable(page, NULL)) { 3272 enum lru_list l = page_lru_base_type(page); 3273 3274 __dec_zone_state(zone, NR_UNEVICTABLE); 3275 list_move(&page->lru, &zone->lru[l].list); 3276 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3277 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3278 __count_vm_event(UNEVICTABLE_PGRESCUED); 3279 } else { 3280 /* 3281 * rotate unevictable list 3282 */ 3283 SetPageUnevictable(page); 3284 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3285 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3286 if (page_evictable(page, NULL)) 3287 goto retry; 3288 } 3289 } 3290 3291 /** 3292 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3293 * @mapping: struct address_space to scan for evictable pages 3294 * 3295 * Scan all pages in mapping. Check unevictable pages for 3296 * evictability and move them to the appropriate zone lru list. 3297 */ 3298 void scan_mapping_unevictable_pages(struct address_space *mapping) 3299 { 3300 pgoff_t next = 0; 3301 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3302 PAGE_CACHE_SHIFT; 3303 struct zone *zone; 3304 struct pagevec pvec; 3305 3306 if (mapping->nrpages == 0) 3307 return; 3308 3309 pagevec_init(&pvec, 0); 3310 while (next < end && 3311 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3312 int i; 3313 int pg_scanned = 0; 3314 3315 zone = NULL; 3316 3317 for (i = 0; i < pagevec_count(&pvec); i++) { 3318 struct page *page = pvec.pages[i]; 3319 pgoff_t page_index = page->index; 3320 struct zone *pagezone = page_zone(page); 3321 3322 pg_scanned++; 3323 if (page_index > next) 3324 next = page_index; 3325 next++; 3326 3327 if (pagezone != zone) { 3328 if (zone) 3329 spin_unlock_irq(&zone->lru_lock); 3330 zone = pagezone; 3331 spin_lock_irq(&zone->lru_lock); 3332 } 3333 3334 if (PageLRU(page) && PageUnevictable(page)) 3335 check_move_unevictable_page(page, zone); 3336 } 3337 if (zone) 3338 spin_unlock_irq(&zone->lru_lock); 3339 pagevec_release(&pvec); 3340 3341 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3342 } 3343 3344 } 3345 3346 /** 3347 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3348 * @zone - zone of which to scan the unevictable list 3349 * 3350 * Scan @zone's unevictable LRU lists to check for pages that have become 3351 * evictable. Move those that have to @zone's inactive list where they 3352 * become candidates for reclaim, unless shrink_inactive_zone() decides 3353 * to reactivate them. Pages that are still unevictable are rotated 3354 * back onto @zone's unevictable list. 3355 */ 3356 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3357 static void scan_zone_unevictable_pages(struct zone *zone) 3358 { 3359 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3360 unsigned long scan; 3361 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3362 3363 while (nr_to_scan > 0) { 3364 unsigned long batch_size = min(nr_to_scan, 3365 SCAN_UNEVICTABLE_BATCH_SIZE); 3366 3367 spin_lock_irq(&zone->lru_lock); 3368 for (scan = 0; scan < batch_size; scan++) { 3369 struct page *page = lru_to_page(l_unevictable); 3370 3371 if (!trylock_page(page)) 3372 continue; 3373 3374 prefetchw_prev_lru_page(page, l_unevictable, flags); 3375 3376 if (likely(PageLRU(page) && PageUnevictable(page))) 3377 check_move_unevictable_page(page, zone); 3378 3379 unlock_page(page); 3380 } 3381 spin_unlock_irq(&zone->lru_lock); 3382 3383 nr_to_scan -= batch_size; 3384 } 3385 } 3386 3387 3388 /** 3389 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3390 * 3391 * A really big hammer: scan all zones' unevictable LRU lists to check for 3392 * pages that have become evictable. Move those back to the zones' 3393 * inactive list where they become candidates for reclaim. 3394 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3395 * and we add swap to the system. As such, it runs in the context of a task 3396 * that has possibly/probably made some previously unevictable pages 3397 * evictable. 3398 */ 3399 static void scan_all_zones_unevictable_pages(void) 3400 { 3401 struct zone *zone; 3402 3403 for_each_zone(zone) { 3404 scan_zone_unevictable_pages(zone); 3405 } 3406 } 3407 3408 /* 3409 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3410 * all nodes' unevictable lists for evictable pages 3411 */ 3412 unsigned long scan_unevictable_pages; 3413 3414 int scan_unevictable_handler(struct ctl_table *table, int write, 3415 void __user *buffer, 3416 size_t *length, loff_t *ppos) 3417 { 3418 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3419 3420 if (write && *(unsigned long *)table->data) 3421 scan_all_zones_unevictable_pages(); 3422 3423 scan_unevictable_pages = 0; 3424 return 0; 3425 } 3426 3427 #ifdef CONFIG_NUMA 3428 /* 3429 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3430 * a specified node's per zone unevictable lists for evictable pages. 3431 */ 3432 3433 static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3434 struct sysdev_attribute *attr, 3435 char *buf) 3436 { 3437 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3438 } 3439 3440 static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3441 struct sysdev_attribute *attr, 3442 const char *buf, size_t count) 3443 { 3444 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3445 struct zone *zone; 3446 unsigned long res; 3447 unsigned long req = strict_strtoul(buf, 10, &res); 3448 3449 if (!req) 3450 return 1; /* zero is no-op */ 3451 3452 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3453 if (!populated_zone(zone)) 3454 continue; 3455 scan_zone_unevictable_pages(zone); 3456 } 3457 return 1; 3458 } 3459 3460 3461 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3462 read_scan_unevictable_node, 3463 write_scan_unevictable_node); 3464 3465 int scan_unevictable_register_node(struct node *node) 3466 { 3467 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3468 } 3469 3470 void scan_unevictable_unregister_node(struct node *node) 3471 { 3472 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3473 } 3474 #endif 3475