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/slab.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/notifier.h> 36 #include <linux/rwsem.h> 37 #include <linux/delay.h> 38 #include <linux/kthread.h> 39 #include <linux/freezer.h> 40 #include <linux/memcontrol.h> 41 #include <linux/delayacct.h> 42 #include <linux/sysctl.h> 43 44 #include <asm/tlbflush.h> 45 #include <asm/div64.h> 46 47 #include <linux/swapops.h> 48 49 #include "internal.h" 50 51 struct scan_control { 52 /* Incremented by the number of inactive pages that were scanned */ 53 unsigned long nr_scanned; 54 55 /* Number of pages freed so far during a call to shrink_zones() */ 56 unsigned long nr_reclaimed; 57 58 /* This context's GFP mask */ 59 gfp_t gfp_mask; 60 61 int may_writepage; 62 63 /* Can mapped pages be reclaimed? */ 64 int may_unmap; 65 66 /* This context's SWAP_CLUSTER_MAX. If freeing memory for 67 * suspend, we effectively ignore SWAP_CLUSTER_MAX. 68 * In this context, it doesn't matter that we scan the 69 * whole list at once. */ 70 int swap_cluster_max; 71 72 int swappiness; 73 74 int all_unreclaimable; 75 76 int order; 77 78 /* Which cgroup do we reclaim from */ 79 struct mem_cgroup *mem_cgroup; 80 81 /* 82 * Nodemask of nodes allowed by the caller. If NULL, all nodes 83 * are scanned. 84 */ 85 nodemask_t *nodemask; 86 87 /* Pluggable isolate pages callback */ 88 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst, 89 unsigned long *scanned, int order, int mode, 90 struct zone *z, struct mem_cgroup *mem_cont, 91 int active, int file); 92 }; 93 94 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 95 96 #ifdef ARCH_HAS_PREFETCH 97 #define prefetch_prev_lru_page(_page, _base, _field) \ 98 do { \ 99 if ((_page)->lru.prev != _base) { \ 100 struct page *prev; \ 101 \ 102 prev = lru_to_page(&(_page->lru)); \ 103 prefetch(&prev->_field); \ 104 } \ 105 } while (0) 106 #else 107 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 108 #endif 109 110 #ifdef ARCH_HAS_PREFETCHW 111 #define prefetchw_prev_lru_page(_page, _base, _field) \ 112 do { \ 113 if ((_page)->lru.prev != _base) { \ 114 struct page *prev; \ 115 \ 116 prev = lru_to_page(&(_page->lru)); \ 117 prefetchw(&prev->_field); \ 118 } \ 119 } while (0) 120 #else 121 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 122 #endif 123 124 /* 125 * From 0 .. 100. Higher means more swappy. 126 */ 127 int vm_swappiness = 60; 128 long vm_total_pages; /* The total number of pages which the VM controls */ 129 130 static LIST_HEAD(shrinker_list); 131 static DECLARE_RWSEM(shrinker_rwsem); 132 133 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 134 #define scanning_global_lru(sc) (!(sc)->mem_cgroup) 135 #else 136 #define scanning_global_lru(sc) (1) 137 #endif 138 139 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 140 struct scan_control *sc) 141 { 142 if (!scanning_global_lru(sc)) 143 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 144 145 return &zone->reclaim_stat; 146 } 147 148 static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc, 149 enum lru_list lru) 150 { 151 if (!scanning_global_lru(sc)) 152 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); 153 154 return zone_page_state(zone, NR_LRU_BASE + lru); 155 } 156 157 158 /* 159 * Add a shrinker callback to be called from the vm 160 */ 161 void register_shrinker(struct shrinker *shrinker) 162 { 163 shrinker->nr = 0; 164 down_write(&shrinker_rwsem); 165 list_add_tail(&shrinker->list, &shrinker_list); 166 up_write(&shrinker_rwsem); 167 } 168 EXPORT_SYMBOL(register_shrinker); 169 170 /* 171 * Remove one 172 */ 173 void unregister_shrinker(struct shrinker *shrinker) 174 { 175 down_write(&shrinker_rwsem); 176 list_del(&shrinker->list); 177 up_write(&shrinker_rwsem); 178 } 179 EXPORT_SYMBOL(unregister_shrinker); 180 181 #define SHRINK_BATCH 128 182 /* 183 * Call the shrink functions to age shrinkable caches 184 * 185 * Here we assume it costs one seek to replace a lru page and that it also 186 * takes a seek to recreate a cache object. With this in mind we age equal 187 * percentages of the lru and ageable caches. This should balance the seeks 188 * generated by these structures. 189 * 190 * If the vm encountered mapped pages on the LRU it increase the pressure on 191 * slab to avoid swapping. 192 * 193 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 194 * 195 * `lru_pages' represents the number of on-LRU pages in all the zones which 196 * are eligible for the caller's allocation attempt. It is used for balancing 197 * slab reclaim versus page reclaim. 198 * 199 * Returns the number of slab objects which we shrunk. 200 */ 201 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 202 unsigned long lru_pages) 203 { 204 struct shrinker *shrinker; 205 unsigned long ret = 0; 206 207 if (scanned == 0) 208 scanned = SWAP_CLUSTER_MAX; 209 210 if (!down_read_trylock(&shrinker_rwsem)) 211 return 1; /* Assume we'll be able to shrink next time */ 212 213 list_for_each_entry(shrinker, &shrinker_list, list) { 214 unsigned long long delta; 215 unsigned long total_scan; 216 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask); 217 218 delta = (4 * scanned) / shrinker->seeks; 219 delta *= max_pass; 220 do_div(delta, lru_pages + 1); 221 shrinker->nr += delta; 222 if (shrinker->nr < 0) { 223 printk(KERN_ERR "shrink_slab: %pF negative objects to " 224 "delete nr=%ld\n", 225 shrinker->shrink, shrinker->nr); 226 shrinker->nr = max_pass; 227 } 228 229 /* 230 * Avoid risking looping forever due to too large nr value: 231 * never try to free more than twice the estimate number of 232 * freeable entries. 233 */ 234 if (shrinker->nr > max_pass * 2) 235 shrinker->nr = max_pass * 2; 236 237 total_scan = shrinker->nr; 238 shrinker->nr = 0; 239 240 while (total_scan >= SHRINK_BATCH) { 241 long this_scan = SHRINK_BATCH; 242 int shrink_ret; 243 int nr_before; 244 245 nr_before = (*shrinker->shrink)(0, gfp_mask); 246 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask); 247 if (shrink_ret == -1) 248 break; 249 if (shrink_ret < nr_before) 250 ret += nr_before - shrink_ret; 251 count_vm_events(SLABS_SCANNED, this_scan); 252 total_scan -= this_scan; 253 254 cond_resched(); 255 } 256 257 shrinker->nr += total_scan; 258 } 259 up_read(&shrinker_rwsem); 260 return ret; 261 } 262 263 /* Called without lock on whether page is mapped, so answer is unstable */ 264 static inline int page_mapping_inuse(struct page *page) 265 { 266 struct address_space *mapping; 267 268 /* Page is in somebody's page tables. */ 269 if (page_mapped(page)) 270 return 1; 271 272 /* Be more reluctant to reclaim swapcache than pagecache */ 273 if (PageSwapCache(page)) 274 return 1; 275 276 mapping = page_mapping(page); 277 if (!mapping) 278 return 0; 279 280 /* File is mmap'd by somebody? */ 281 return mapping_mapped(mapping); 282 } 283 284 static inline int is_page_cache_freeable(struct page *page) 285 { 286 return page_count(page) - !!PagePrivate(page) == 2; 287 } 288 289 static int may_write_to_queue(struct backing_dev_info *bdi) 290 { 291 if (current->flags & PF_SWAPWRITE) 292 return 1; 293 if (!bdi_write_congested(bdi)) 294 return 1; 295 if (bdi == current->backing_dev_info) 296 return 1; 297 return 0; 298 } 299 300 /* 301 * We detected a synchronous write error writing a page out. Probably 302 * -ENOSPC. We need to propagate that into the address_space for a subsequent 303 * fsync(), msync() or close(). 304 * 305 * The tricky part is that after writepage we cannot touch the mapping: nothing 306 * prevents it from being freed up. But we have a ref on the page and once 307 * that page is locked, the mapping is pinned. 308 * 309 * We're allowed to run sleeping lock_page() here because we know the caller has 310 * __GFP_FS. 311 */ 312 static void handle_write_error(struct address_space *mapping, 313 struct page *page, int error) 314 { 315 lock_page(page); 316 if (page_mapping(page) == mapping) 317 mapping_set_error(mapping, error); 318 unlock_page(page); 319 } 320 321 /* Request for sync pageout. */ 322 enum pageout_io { 323 PAGEOUT_IO_ASYNC, 324 PAGEOUT_IO_SYNC, 325 }; 326 327 /* possible outcome of pageout() */ 328 typedef enum { 329 /* failed to write page out, page is locked */ 330 PAGE_KEEP, 331 /* move page to the active list, page is locked */ 332 PAGE_ACTIVATE, 333 /* page has been sent to the disk successfully, page is unlocked */ 334 PAGE_SUCCESS, 335 /* page is clean and locked */ 336 PAGE_CLEAN, 337 } pageout_t; 338 339 /* 340 * pageout is called by shrink_page_list() for each dirty page. 341 * Calls ->writepage(). 342 */ 343 static pageout_t pageout(struct page *page, struct address_space *mapping, 344 enum pageout_io sync_writeback) 345 { 346 /* 347 * If the page is dirty, only perform writeback if that write 348 * will be non-blocking. To prevent this allocation from being 349 * stalled by pagecache activity. But note that there may be 350 * stalls if we need to run get_block(). We could test 351 * PagePrivate for that. 352 * 353 * If this process is currently in generic_file_write() against 354 * this page's queue, we can perform writeback even if that 355 * will block. 356 * 357 * If the page is swapcache, write it back even if that would 358 * block, for some throttling. This happens by accident, because 359 * swap_backing_dev_info is bust: it doesn't reflect the 360 * congestion state of the swapdevs. Easy to fix, if needed. 361 * See swapfile.c:page_queue_congested(). 362 */ 363 if (!is_page_cache_freeable(page)) 364 return PAGE_KEEP; 365 if (!mapping) { 366 /* 367 * Some data journaling orphaned pages can have 368 * page->mapping == NULL while being dirty with clean buffers. 369 */ 370 if (PagePrivate(page)) { 371 if (try_to_free_buffers(page)) { 372 ClearPageDirty(page); 373 printk("%s: orphaned page\n", __func__); 374 return PAGE_CLEAN; 375 } 376 } 377 return PAGE_KEEP; 378 } 379 if (mapping->a_ops->writepage == NULL) 380 return PAGE_ACTIVATE; 381 if (!may_write_to_queue(mapping->backing_dev_info)) 382 return PAGE_KEEP; 383 384 if (clear_page_dirty_for_io(page)) { 385 int res; 386 struct writeback_control wbc = { 387 .sync_mode = WB_SYNC_NONE, 388 .nr_to_write = SWAP_CLUSTER_MAX, 389 .range_start = 0, 390 .range_end = LLONG_MAX, 391 .nonblocking = 1, 392 .for_reclaim = 1, 393 }; 394 395 SetPageReclaim(page); 396 res = mapping->a_ops->writepage(page, &wbc); 397 if (res < 0) 398 handle_write_error(mapping, page, res); 399 if (res == AOP_WRITEPAGE_ACTIVATE) { 400 ClearPageReclaim(page); 401 return PAGE_ACTIVATE; 402 } 403 404 /* 405 * Wait on writeback if requested to. This happens when 406 * direct reclaiming a large contiguous area and the 407 * first attempt to free a range of pages fails. 408 */ 409 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) 410 wait_on_page_writeback(page); 411 412 if (!PageWriteback(page)) { 413 /* synchronous write or broken a_ops? */ 414 ClearPageReclaim(page); 415 } 416 inc_zone_page_state(page, NR_VMSCAN_WRITE); 417 return PAGE_SUCCESS; 418 } 419 420 return PAGE_CLEAN; 421 } 422 423 /* 424 * Same as remove_mapping, but if the page is removed from the mapping, it 425 * gets returned with a refcount of 0. 426 */ 427 static int __remove_mapping(struct address_space *mapping, struct page *page) 428 { 429 BUG_ON(!PageLocked(page)); 430 BUG_ON(mapping != page_mapping(page)); 431 432 spin_lock_irq(&mapping->tree_lock); 433 /* 434 * The non racy check for a busy page. 435 * 436 * Must be careful with the order of the tests. When someone has 437 * a ref to the page, it may be possible that they dirty it then 438 * drop the reference. So if PageDirty is tested before page_count 439 * here, then the following race may occur: 440 * 441 * get_user_pages(&page); 442 * [user mapping goes away] 443 * write_to(page); 444 * !PageDirty(page) [good] 445 * SetPageDirty(page); 446 * put_page(page); 447 * !page_count(page) [good, discard it] 448 * 449 * [oops, our write_to data is lost] 450 * 451 * Reversing the order of the tests ensures such a situation cannot 452 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 453 * load is not satisfied before that of page->_count. 454 * 455 * Note that if SetPageDirty is always performed via set_page_dirty, 456 * and thus under tree_lock, then this ordering is not required. 457 */ 458 if (!page_freeze_refs(page, 2)) 459 goto cannot_free; 460 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 461 if (unlikely(PageDirty(page))) { 462 page_unfreeze_refs(page, 2); 463 goto cannot_free; 464 } 465 466 if (PageSwapCache(page)) { 467 swp_entry_t swap = { .val = page_private(page) }; 468 __delete_from_swap_cache(page); 469 spin_unlock_irq(&mapping->tree_lock); 470 swap_free(swap); 471 } else { 472 __remove_from_page_cache(page); 473 spin_unlock_irq(&mapping->tree_lock); 474 } 475 476 return 1; 477 478 cannot_free: 479 spin_unlock_irq(&mapping->tree_lock); 480 return 0; 481 } 482 483 /* 484 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 485 * someone else has a ref on the page, abort and return 0. If it was 486 * successfully detached, return 1. Assumes the caller has a single ref on 487 * this page. 488 */ 489 int remove_mapping(struct address_space *mapping, struct page *page) 490 { 491 if (__remove_mapping(mapping, page)) { 492 /* 493 * Unfreezing the refcount with 1 rather than 2 effectively 494 * drops the pagecache ref for us without requiring another 495 * atomic operation. 496 */ 497 page_unfreeze_refs(page, 1); 498 return 1; 499 } 500 return 0; 501 } 502 503 /** 504 * putback_lru_page - put previously isolated page onto appropriate LRU list 505 * @page: page to be put back to appropriate lru list 506 * 507 * Add previously isolated @page to appropriate LRU list. 508 * Page may still be unevictable for other reasons. 509 * 510 * lru_lock must not be held, interrupts must be enabled. 511 */ 512 #ifdef CONFIG_UNEVICTABLE_LRU 513 void putback_lru_page(struct page *page) 514 { 515 int lru; 516 int active = !!TestClearPageActive(page); 517 int was_unevictable = PageUnevictable(page); 518 519 VM_BUG_ON(PageLRU(page)); 520 521 redo: 522 ClearPageUnevictable(page); 523 524 if (page_evictable(page, NULL)) { 525 /* 526 * For evictable pages, we can use the cache. 527 * In event of a race, worst case is we end up with an 528 * unevictable page on [in]active list. 529 * We know how to handle that. 530 */ 531 lru = active + page_is_file_cache(page); 532 lru_cache_add_lru(page, lru); 533 } else { 534 /* 535 * Put unevictable pages directly on zone's unevictable 536 * list. 537 */ 538 lru = LRU_UNEVICTABLE; 539 add_page_to_unevictable_list(page); 540 } 541 542 /* 543 * page's status can change while we move it among lru. If an evictable 544 * page is on unevictable list, it never be freed. To avoid that, 545 * check after we added it to the list, again. 546 */ 547 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 548 if (!isolate_lru_page(page)) { 549 put_page(page); 550 goto redo; 551 } 552 /* This means someone else dropped this page from LRU 553 * So, it will be freed or putback to LRU again. There is 554 * nothing to do here. 555 */ 556 } 557 558 if (was_unevictable && lru != LRU_UNEVICTABLE) 559 count_vm_event(UNEVICTABLE_PGRESCUED); 560 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 561 count_vm_event(UNEVICTABLE_PGCULLED); 562 563 put_page(page); /* drop ref from isolate */ 564 } 565 566 #else /* CONFIG_UNEVICTABLE_LRU */ 567 568 void putback_lru_page(struct page *page) 569 { 570 int lru; 571 VM_BUG_ON(PageLRU(page)); 572 573 lru = !!TestClearPageActive(page) + page_is_file_cache(page); 574 lru_cache_add_lru(page, lru); 575 put_page(page); 576 } 577 #endif /* CONFIG_UNEVICTABLE_LRU */ 578 579 580 /* 581 * shrink_page_list() returns the number of reclaimed pages 582 */ 583 static unsigned long shrink_page_list(struct list_head *page_list, 584 struct scan_control *sc, 585 enum pageout_io sync_writeback) 586 { 587 LIST_HEAD(ret_pages); 588 struct pagevec freed_pvec; 589 int pgactivate = 0; 590 unsigned long nr_reclaimed = 0; 591 592 cond_resched(); 593 594 pagevec_init(&freed_pvec, 1); 595 while (!list_empty(page_list)) { 596 struct address_space *mapping; 597 struct page *page; 598 int may_enter_fs; 599 int referenced; 600 601 cond_resched(); 602 603 page = lru_to_page(page_list); 604 list_del(&page->lru); 605 606 if (!trylock_page(page)) 607 goto keep; 608 609 VM_BUG_ON(PageActive(page)); 610 611 sc->nr_scanned++; 612 613 if (unlikely(!page_evictable(page, NULL))) 614 goto cull_mlocked; 615 616 if (!sc->may_unmap && page_mapped(page)) 617 goto keep_locked; 618 619 /* Double the slab pressure for mapped and swapcache pages */ 620 if (page_mapped(page) || PageSwapCache(page)) 621 sc->nr_scanned++; 622 623 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 624 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 625 626 if (PageWriteback(page)) { 627 /* 628 * Synchronous reclaim is performed in two passes, 629 * first an asynchronous pass over the list to 630 * start parallel writeback, and a second synchronous 631 * pass to wait for the IO to complete. Wait here 632 * for any page for which writeback has already 633 * started. 634 */ 635 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) 636 wait_on_page_writeback(page); 637 else 638 goto keep_locked; 639 } 640 641 referenced = page_referenced(page, 1, sc->mem_cgroup); 642 /* In active use or really unfreeable? Activate it. */ 643 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && 644 referenced && page_mapping_inuse(page)) 645 goto activate_locked; 646 647 /* 648 * Anonymous process memory has backing store? 649 * Try to allocate it some swap space here. 650 */ 651 if (PageAnon(page) && !PageSwapCache(page)) { 652 if (!(sc->gfp_mask & __GFP_IO)) 653 goto keep_locked; 654 if (!add_to_swap(page)) 655 goto activate_locked; 656 may_enter_fs = 1; 657 } 658 659 mapping = page_mapping(page); 660 661 /* 662 * The page is mapped into the page tables of one or more 663 * processes. Try to unmap it here. 664 */ 665 if (page_mapped(page) && mapping) { 666 switch (try_to_unmap(page, 0)) { 667 case SWAP_FAIL: 668 goto activate_locked; 669 case SWAP_AGAIN: 670 goto keep_locked; 671 case SWAP_MLOCK: 672 goto cull_mlocked; 673 case SWAP_SUCCESS: 674 ; /* try to free the page below */ 675 } 676 } 677 678 if (PageDirty(page)) { 679 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced) 680 goto keep_locked; 681 if (!may_enter_fs) 682 goto keep_locked; 683 if (!sc->may_writepage) 684 goto keep_locked; 685 686 /* Page is dirty, try to write it out here */ 687 switch (pageout(page, mapping, sync_writeback)) { 688 case PAGE_KEEP: 689 goto keep_locked; 690 case PAGE_ACTIVATE: 691 goto activate_locked; 692 case PAGE_SUCCESS: 693 if (PageWriteback(page) || PageDirty(page)) 694 goto keep; 695 /* 696 * A synchronous write - probably a ramdisk. Go 697 * ahead and try to reclaim the page. 698 */ 699 if (!trylock_page(page)) 700 goto keep; 701 if (PageDirty(page) || PageWriteback(page)) 702 goto keep_locked; 703 mapping = page_mapping(page); 704 case PAGE_CLEAN: 705 ; /* try to free the page below */ 706 } 707 } 708 709 /* 710 * If the page has buffers, try to free the buffer mappings 711 * associated with this page. If we succeed we try to free 712 * the page as well. 713 * 714 * We do this even if the page is PageDirty(). 715 * try_to_release_page() does not perform I/O, but it is 716 * possible for a page to have PageDirty set, but it is actually 717 * clean (all its buffers are clean). This happens if the 718 * buffers were written out directly, with submit_bh(). ext3 719 * will do this, as well as the blockdev mapping. 720 * try_to_release_page() will discover that cleanness and will 721 * drop the buffers and mark the page clean - it can be freed. 722 * 723 * Rarely, pages can have buffers and no ->mapping. These are 724 * the pages which were not successfully invalidated in 725 * truncate_complete_page(). We try to drop those buffers here 726 * and if that worked, and the page is no longer mapped into 727 * process address space (page_count == 1) it can be freed. 728 * Otherwise, leave the page on the LRU so it is swappable. 729 */ 730 if (PagePrivate(page)) { 731 if (!try_to_release_page(page, sc->gfp_mask)) 732 goto activate_locked; 733 if (!mapping && page_count(page) == 1) { 734 unlock_page(page); 735 if (put_page_testzero(page)) 736 goto free_it; 737 else { 738 /* 739 * rare race with speculative reference. 740 * the speculative reference will free 741 * this page shortly, so we may 742 * increment nr_reclaimed here (and 743 * leave it off the LRU). 744 */ 745 nr_reclaimed++; 746 continue; 747 } 748 } 749 } 750 751 if (!mapping || !__remove_mapping(mapping, page)) 752 goto keep_locked; 753 754 /* 755 * At this point, we have no other references and there is 756 * no way to pick any more up (removed from LRU, removed 757 * from pagecache). Can use non-atomic bitops now (and 758 * we obviously don't have to worry about waking up a process 759 * waiting on the page lock, because there are no references. 760 */ 761 __clear_page_locked(page); 762 free_it: 763 nr_reclaimed++; 764 if (!pagevec_add(&freed_pvec, page)) { 765 __pagevec_free(&freed_pvec); 766 pagevec_reinit(&freed_pvec); 767 } 768 continue; 769 770 cull_mlocked: 771 if (PageSwapCache(page)) 772 try_to_free_swap(page); 773 unlock_page(page); 774 putback_lru_page(page); 775 continue; 776 777 activate_locked: 778 /* Not a candidate for swapping, so reclaim swap space. */ 779 if (PageSwapCache(page) && vm_swap_full()) 780 try_to_free_swap(page); 781 VM_BUG_ON(PageActive(page)); 782 SetPageActive(page); 783 pgactivate++; 784 keep_locked: 785 unlock_page(page); 786 keep: 787 list_add(&page->lru, &ret_pages); 788 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 789 } 790 list_splice(&ret_pages, page_list); 791 if (pagevec_count(&freed_pvec)) 792 __pagevec_free(&freed_pvec); 793 count_vm_events(PGACTIVATE, pgactivate); 794 return nr_reclaimed; 795 } 796 797 /* LRU Isolation modes. */ 798 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */ 799 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */ 800 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ 801 802 /* 803 * Attempt to remove the specified page from its LRU. Only take this page 804 * if it is of the appropriate PageActive status. Pages which are being 805 * freed elsewhere are also ignored. 806 * 807 * page: page to consider 808 * mode: one of the LRU isolation modes defined above 809 * 810 * returns 0 on success, -ve errno on failure. 811 */ 812 int __isolate_lru_page(struct page *page, int mode, int file) 813 { 814 int ret = -EINVAL; 815 816 /* Only take pages on the LRU. */ 817 if (!PageLRU(page)) 818 return ret; 819 820 /* 821 * When checking the active state, we need to be sure we are 822 * dealing with comparible boolean values. Take the logical not 823 * of each. 824 */ 825 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 826 return ret; 827 828 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file)) 829 return ret; 830 831 /* 832 * When this function is being called for lumpy reclaim, we 833 * initially look into all LRU pages, active, inactive and 834 * unevictable; only give shrink_page_list evictable pages. 835 */ 836 if (PageUnevictable(page)) 837 return ret; 838 839 ret = -EBUSY; 840 841 if (likely(get_page_unless_zero(page))) { 842 /* 843 * Be careful not to clear PageLRU until after we're 844 * sure the page is not being freed elsewhere -- the 845 * page release code relies on it. 846 */ 847 ClearPageLRU(page); 848 ret = 0; 849 mem_cgroup_del_lru(page); 850 } 851 852 return ret; 853 } 854 855 /* 856 * zone->lru_lock is heavily contended. Some of the functions that 857 * shrink the lists perform better by taking out a batch of pages 858 * and working on them outside the LRU lock. 859 * 860 * For pagecache intensive workloads, this function is the hottest 861 * spot in the kernel (apart from copy_*_user functions). 862 * 863 * Appropriate locks must be held before calling this function. 864 * 865 * @nr_to_scan: The number of pages to look through on the list. 866 * @src: The LRU list to pull pages off. 867 * @dst: The temp list to put pages on to. 868 * @scanned: The number of pages that were scanned. 869 * @order: The caller's attempted allocation order 870 * @mode: One of the LRU isolation modes 871 * @file: True [1] if isolating file [!anon] pages 872 * 873 * returns how many pages were moved onto *@dst. 874 */ 875 static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 876 struct list_head *src, struct list_head *dst, 877 unsigned long *scanned, int order, int mode, int file) 878 { 879 unsigned long nr_taken = 0; 880 unsigned long scan; 881 882 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 883 struct page *page; 884 unsigned long pfn; 885 unsigned long end_pfn; 886 unsigned long page_pfn; 887 int zone_id; 888 889 page = lru_to_page(src); 890 prefetchw_prev_lru_page(page, src, flags); 891 892 VM_BUG_ON(!PageLRU(page)); 893 894 switch (__isolate_lru_page(page, mode, file)) { 895 case 0: 896 list_move(&page->lru, dst); 897 nr_taken++; 898 break; 899 900 case -EBUSY: 901 /* else it is being freed elsewhere */ 902 list_move(&page->lru, src); 903 continue; 904 905 default: 906 BUG(); 907 } 908 909 if (!order) 910 continue; 911 912 /* 913 * Attempt to take all pages in the order aligned region 914 * surrounding the tag page. Only take those pages of 915 * the same active state as that tag page. We may safely 916 * round the target page pfn down to the requested order 917 * as the mem_map is guarenteed valid out to MAX_ORDER, 918 * where that page is in a different zone we will detect 919 * it from its zone id and abort this block scan. 920 */ 921 zone_id = page_zone_id(page); 922 page_pfn = page_to_pfn(page); 923 pfn = page_pfn & ~((1 << order) - 1); 924 end_pfn = pfn + (1 << order); 925 for (; pfn < end_pfn; pfn++) { 926 struct page *cursor_page; 927 928 /* The target page is in the block, ignore it. */ 929 if (unlikely(pfn == page_pfn)) 930 continue; 931 932 /* Avoid holes within the zone. */ 933 if (unlikely(!pfn_valid_within(pfn))) 934 break; 935 936 cursor_page = pfn_to_page(pfn); 937 938 /* Check that we have not crossed a zone boundary. */ 939 if (unlikely(page_zone_id(cursor_page) != zone_id)) 940 continue; 941 switch (__isolate_lru_page(cursor_page, mode, file)) { 942 case 0: 943 list_move(&cursor_page->lru, dst); 944 nr_taken++; 945 scan++; 946 break; 947 948 case -EBUSY: 949 /* else it is being freed elsewhere */ 950 list_move(&cursor_page->lru, src); 951 default: 952 break; /* ! on LRU or wrong list */ 953 } 954 } 955 } 956 957 *scanned = scan; 958 return nr_taken; 959 } 960 961 static unsigned long isolate_pages_global(unsigned long nr, 962 struct list_head *dst, 963 unsigned long *scanned, int order, 964 int mode, struct zone *z, 965 struct mem_cgroup *mem_cont, 966 int active, int file) 967 { 968 int lru = LRU_BASE; 969 if (active) 970 lru += LRU_ACTIVE; 971 if (file) 972 lru += LRU_FILE; 973 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 974 mode, !!file); 975 } 976 977 /* 978 * clear_active_flags() is a helper for shrink_active_list(), clearing 979 * any active bits from the pages in the list. 980 */ 981 static unsigned long clear_active_flags(struct list_head *page_list, 982 unsigned int *count) 983 { 984 int nr_active = 0; 985 int lru; 986 struct page *page; 987 988 list_for_each_entry(page, page_list, lru) { 989 lru = page_is_file_cache(page); 990 if (PageActive(page)) { 991 lru += LRU_ACTIVE; 992 ClearPageActive(page); 993 nr_active++; 994 } 995 count[lru]++; 996 } 997 998 return nr_active; 999 } 1000 1001 /** 1002 * isolate_lru_page - tries to isolate a page from its LRU list 1003 * @page: page to isolate from its LRU list 1004 * 1005 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1006 * vmstat statistic corresponding to whatever LRU list the page was on. 1007 * 1008 * Returns 0 if the page was removed from an LRU list. 1009 * Returns -EBUSY if the page was not on an LRU list. 1010 * 1011 * The returned page will have PageLRU() cleared. If it was found on 1012 * the active list, it will have PageActive set. If it was found on 1013 * the unevictable list, it will have the PageUnevictable bit set. That flag 1014 * may need to be cleared by the caller before letting the page go. 1015 * 1016 * The vmstat statistic corresponding to the list on which the page was 1017 * found will be decremented. 1018 * 1019 * Restrictions: 1020 * (1) Must be called with an elevated refcount on the page. This is a 1021 * fundamentnal difference from isolate_lru_pages (which is called 1022 * without a stable reference). 1023 * (2) the lru_lock must not be held. 1024 * (3) interrupts must be enabled. 1025 */ 1026 int isolate_lru_page(struct page *page) 1027 { 1028 int ret = -EBUSY; 1029 1030 if (PageLRU(page)) { 1031 struct zone *zone = page_zone(page); 1032 1033 spin_lock_irq(&zone->lru_lock); 1034 if (PageLRU(page) && get_page_unless_zero(page)) { 1035 int lru = page_lru(page); 1036 ret = 0; 1037 ClearPageLRU(page); 1038 1039 del_page_from_lru_list(zone, page, lru); 1040 } 1041 spin_unlock_irq(&zone->lru_lock); 1042 } 1043 return ret; 1044 } 1045 1046 /* 1047 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1048 * of reclaimed pages 1049 */ 1050 static unsigned long shrink_inactive_list(unsigned long max_scan, 1051 struct zone *zone, struct scan_control *sc, 1052 int priority, int file) 1053 { 1054 LIST_HEAD(page_list); 1055 struct pagevec pvec; 1056 unsigned long nr_scanned = 0; 1057 unsigned long nr_reclaimed = 0; 1058 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1059 1060 pagevec_init(&pvec, 1); 1061 1062 lru_add_drain(); 1063 spin_lock_irq(&zone->lru_lock); 1064 do { 1065 struct page *page; 1066 unsigned long nr_taken; 1067 unsigned long nr_scan; 1068 unsigned long nr_freed; 1069 unsigned long nr_active; 1070 unsigned int count[NR_LRU_LISTS] = { 0, }; 1071 int mode = ISOLATE_INACTIVE; 1072 1073 /* 1074 * If we need a large contiguous chunk of memory, or have 1075 * trouble getting a small set of contiguous pages, we 1076 * will reclaim both active and inactive pages. 1077 * 1078 * We use the same threshold as pageout congestion_wait below. 1079 */ 1080 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1081 mode = ISOLATE_BOTH; 1082 else if (sc->order && priority < DEF_PRIORITY - 2) 1083 mode = ISOLATE_BOTH; 1084 1085 nr_taken = sc->isolate_pages(sc->swap_cluster_max, 1086 &page_list, &nr_scan, sc->order, mode, 1087 zone, sc->mem_cgroup, 0, file); 1088 nr_active = clear_active_flags(&page_list, count); 1089 __count_vm_events(PGDEACTIVATE, nr_active); 1090 1091 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1092 -count[LRU_ACTIVE_FILE]); 1093 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1094 -count[LRU_INACTIVE_FILE]); 1095 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1096 -count[LRU_ACTIVE_ANON]); 1097 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1098 -count[LRU_INACTIVE_ANON]); 1099 1100 if (scanning_global_lru(sc)) 1101 zone->pages_scanned += nr_scan; 1102 1103 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON]; 1104 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON]; 1105 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE]; 1106 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE]; 1107 1108 spin_unlock_irq(&zone->lru_lock); 1109 1110 nr_scanned += nr_scan; 1111 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); 1112 1113 /* 1114 * If we are direct reclaiming for contiguous pages and we do 1115 * not reclaim everything in the list, try again and wait 1116 * for IO to complete. This will stall high-order allocations 1117 * but that should be acceptable to the caller 1118 */ 1119 if (nr_freed < nr_taken && !current_is_kswapd() && 1120 sc->order > PAGE_ALLOC_COSTLY_ORDER) { 1121 congestion_wait(WRITE, HZ/10); 1122 1123 /* 1124 * The attempt at page out may have made some 1125 * of the pages active, mark them inactive again. 1126 */ 1127 nr_active = clear_active_flags(&page_list, count); 1128 count_vm_events(PGDEACTIVATE, nr_active); 1129 1130 nr_freed += shrink_page_list(&page_list, sc, 1131 PAGEOUT_IO_SYNC); 1132 } 1133 1134 nr_reclaimed += nr_freed; 1135 local_irq_disable(); 1136 if (current_is_kswapd()) { 1137 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan); 1138 __count_vm_events(KSWAPD_STEAL, nr_freed); 1139 } else if (scanning_global_lru(sc)) 1140 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan); 1141 1142 __count_zone_vm_events(PGSTEAL, zone, nr_freed); 1143 1144 if (nr_taken == 0) 1145 goto done; 1146 1147 spin_lock(&zone->lru_lock); 1148 /* 1149 * Put back any unfreeable pages. 1150 */ 1151 while (!list_empty(&page_list)) { 1152 int lru; 1153 page = lru_to_page(&page_list); 1154 VM_BUG_ON(PageLRU(page)); 1155 list_del(&page->lru); 1156 if (unlikely(!page_evictable(page, NULL))) { 1157 spin_unlock_irq(&zone->lru_lock); 1158 putback_lru_page(page); 1159 spin_lock_irq(&zone->lru_lock); 1160 continue; 1161 } 1162 SetPageLRU(page); 1163 lru = page_lru(page); 1164 add_page_to_lru_list(zone, page, lru); 1165 if (PageActive(page)) { 1166 int file = !!page_is_file_cache(page); 1167 reclaim_stat->recent_rotated[file]++; 1168 } 1169 if (!pagevec_add(&pvec, page)) { 1170 spin_unlock_irq(&zone->lru_lock); 1171 __pagevec_release(&pvec); 1172 spin_lock_irq(&zone->lru_lock); 1173 } 1174 } 1175 } while (nr_scanned < max_scan); 1176 spin_unlock(&zone->lru_lock); 1177 done: 1178 local_irq_enable(); 1179 pagevec_release(&pvec); 1180 return nr_reclaimed; 1181 } 1182 1183 /* 1184 * We are about to scan this zone at a certain priority level. If that priority 1185 * level is smaller (ie: more urgent) than the previous priority, then note 1186 * that priority level within the zone. This is done so that when the next 1187 * process comes in to scan this zone, it will immediately start out at this 1188 * priority level rather than having to build up its own scanning priority. 1189 * Here, this priority affects only the reclaim-mapped threshold. 1190 */ 1191 static inline void note_zone_scanning_priority(struct zone *zone, int priority) 1192 { 1193 if (priority < zone->prev_priority) 1194 zone->prev_priority = priority; 1195 } 1196 1197 /* 1198 * This moves pages from the active list to the inactive list. 1199 * 1200 * We move them the other way if the page is referenced by one or more 1201 * processes, from rmap. 1202 * 1203 * If the pages are mostly unmapped, the processing is fast and it is 1204 * appropriate to hold zone->lru_lock across the whole operation. But if 1205 * the pages are mapped, the processing is slow (page_referenced()) so we 1206 * should drop zone->lru_lock around each page. It's impossible to balance 1207 * this, so instead we remove the pages from the LRU while processing them. 1208 * It is safe to rely on PG_active against the non-LRU pages in here because 1209 * nobody will play with that bit on a non-LRU page. 1210 * 1211 * The downside is that we have to touch page->_count against each page. 1212 * But we had to alter page->flags anyway. 1213 */ 1214 1215 1216 static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1217 struct scan_control *sc, int priority, int file) 1218 { 1219 unsigned long pgmoved; 1220 int pgdeactivate = 0; 1221 unsigned long pgscanned; 1222 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1223 LIST_HEAD(l_inactive); 1224 struct page *page; 1225 struct pagevec pvec; 1226 enum lru_list lru; 1227 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1228 1229 lru_add_drain(); 1230 spin_lock_irq(&zone->lru_lock); 1231 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order, 1232 ISOLATE_ACTIVE, zone, 1233 sc->mem_cgroup, 1, file); 1234 /* 1235 * zone->pages_scanned is used for detect zone's oom 1236 * mem_cgroup remembers nr_scan by itself. 1237 */ 1238 if (scanning_global_lru(sc)) { 1239 zone->pages_scanned += pgscanned; 1240 } 1241 reclaim_stat->recent_scanned[!!file] += pgmoved; 1242 1243 if (file) 1244 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved); 1245 else 1246 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved); 1247 spin_unlock_irq(&zone->lru_lock); 1248 1249 pgmoved = 0; 1250 while (!list_empty(&l_hold)) { 1251 cond_resched(); 1252 page = lru_to_page(&l_hold); 1253 list_del(&page->lru); 1254 1255 if (unlikely(!page_evictable(page, NULL))) { 1256 putback_lru_page(page); 1257 continue; 1258 } 1259 1260 /* page_referenced clears PageReferenced */ 1261 if (page_mapping_inuse(page) && 1262 page_referenced(page, 0, sc->mem_cgroup)) 1263 pgmoved++; 1264 1265 list_add(&page->lru, &l_inactive); 1266 } 1267 1268 /* 1269 * Move the pages to the [file or anon] inactive list. 1270 */ 1271 pagevec_init(&pvec, 1); 1272 lru = LRU_BASE + file * LRU_FILE; 1273 1274 spin_lock_irq(&zone->lru_lock); 1275 /* 1276 * Count referenced pages from currently used mappings as 1277 * rotated, even though they are moved to the inactive list. 1278 * This helps balance scan pressure between file and anonymous 1279 * pages in get_scan_ratio. 1280 */ 1281 reclaim_stat->recent_rotated[!!file] += pgmoved; 1282 1283 pgmoved = 0; 1284 while (!list_empty(&l_inactive)) { 1285 page = lru_to_page(&l_inactive); 1286 prefetchw_prev_lru_page(page, &l_inactive, flags); 1287 VM_BUG_ON(PageLRU(page)); 1288 SetPageLRU(page); 1289 VM_BUG_ON(!PageActive(page)); 1290 ClearPageActive(page); 1291 1292 list_move(&page->lru, &zone->lru[lru].list); 1293 mem_cgroup_add_lru_list(page, lru); 1294 pgmoved++; 1295 if (!pagevec_add(&pvec, page)) { 1296 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1297 spin_unlock_irq(&zone->lru_lock); 1298 pgdeactivate += pgmoved; 1299 pgmoved = 0; 1300 if (buffer_heads_over_limit) 1301 pagevec_strip(&pvec); 1302 __pagevec_release(&pvec); 1303 spin_lock_irq(&zone->lru_lock); 1304 } 1305 } 1306 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1307 pgdeactivate += pgmoved; 1308 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1309 __count_vm_events(PGDEACTIVATE, pgdeactivate); 1310 spin_unlock_irq(&zone->lru_lock); 1311 if (buffer_heads_over_limit) 1312 pagevec_strip(&pvec); 1313 pagevec_release(&pvec); 1314 } 1315 1316 static int inactive_anon_is_low_global(struct zone *zone) 1317 { 1318 unsigned long active, inactive; 1319 1320 active = zone_page_state(zone, NR_ACTIVE_ANON); 1321 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1322 1323 if (inactive * zone->inactive_ratio < active) 1324 return 1; 1325 1326 return 0; 1327 } 1328 1329 /** 1330 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1331 * @zone: zone to check 1332 * @sc: scan control of this context 1333 * 1334 * Returns true if the zone does not have enough inactive anon pages, 1335 * meaning some active anon pages need to be deactivated. 1336 */ 1337 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1338 { 1339 int low; 1340 1341 if (scanning_global_lru(sc)) 1342 low = inactive_anon_is_low_global(zone); 1343 else 1344 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1345 return low; 1346 } 1347 1348 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1349 struct zone *zone, struct scan_control *sc, int priority) 1350 { 1351 int file = is_file_lru(lru); 1352 1353 if (lru == LRU_ACTIVE_FILE) { 1354 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1355 return 0; 1356 } 1357 1358 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) { 1359 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1360 return 0; 1361 } 1362 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1363 } 1364 1365 /* 1366 * Determine how aggressively the anon and file LRU lists should be 1367 * scanned. The relative value of each set of LRU lists is determined 1368 * by looking at the fraction of the pages scanned we did rotate back 1369 * onto the active list instead of evict. 1370 * 1371 * percent[0] specifies how much pressure to put on ram/swap backed 1372 * memory, while percent[1] determines pressure on the file LRUs. 1373 */ 1374 static void get_scan_ratio(struct zone *zone, struct scan_control *sc, 1375 unsigned long *percent) 1376 { 1377 unsigned long anon, file, free; 1378 unsigned long anon_prio, file_prio; 1379 unsigned long ap, fp; 1380 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1381 1382 /* If we have no swap space, do not bother scanning anon pages. */ 1383 if (nr_swap_pages <= 0) { 1384 percent[0] = 0; 1385 percent[1] = 100; 1386 return; 1387 } 1388 1389 anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) + 1390 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON); 1391 file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) + 1392 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE); 1393 1394 if (scanning_global_lru(sc)) { 1395 free = zone_page_state(zone, NR_FREE_PAGES); 1396 /* If we have very few page cache pages, 1397 force-scan anon pages. */ 1398 if (unlikely(file + free <= zone->pages_high)) { 1399 percent[0] = 100; 1400 percent[1] = 0; 1401 return; 1402 } 1403 } 1404 1405 /* 1406 * OK, so we have swap space and a fair amount of page cache 1407 * pages. We use the recently rotated / recently scanned 1408 * ratios to determine how valuable each cache is. 1409 * 1410 * Because workloads change over time (and to avoid overflow) 1411 * we keep these statistics as a floating average, which ends 1412 * up weighing recent references more than old ones. 1413 * 1414 * anon in [0], file in [1] 1415 */ 1416 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1417 spin_lock_irq(&zone->lru_lock); 1418 reclaim_stat->recent_scanned[0] /= 2; 1419 reclaim_stat->recent_rotated[0] /= 2; 1420 spin_unlock_irq(&zone->lru_lock); 1421 } 1422 1423 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1424 spin_lock_irq(&zone->lru_lock); 1425 reclaim_stat->recent_scanned[1] /= 2; 1426 reclaim_stat->recent_rotated[1] /= 2; 1427 spin_unlock_irq(&zone->lru_lock); 1428 } 1429 1430 /* 1431 * With swappiness at 100, anonymous and file have the same priority. 1432 * This scanning priority is essentially the inverse of IO cost. 1433 */ 1434 anon_prio = sc->swappiness; 1435 file_prio = 200 - sc->swappiness; 1436 1437 /* 1438 * The amount of pressure on anon vs file pages is inversely 1439 * proportional to the fraction of recently scanned pages on 1440 * each list that were recently referenced and in active use. 1441 */ 1442 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1443 ap /= reclaim_stat->recent_rotated[0] + 1; 1444 1445 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1446 fp /= reclaim_stat->recent_rotated[1] + 1; 1447 1448 /* Normalize to percentages */ 1449 percent[0] = 100 * ap / (ap + fp + 1); 1450 percent[1] = 100 - percent[0]; 1451 } 1452 1453 1454 /* 1455 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1456 */ 1457 static void shrink_zone(int priority, struct zone *zone, 1458 struct scan_control *sc) 1459 { 1460 unsigned long nr[NR_LRU_LISTS]; 1461 unsigned long nr_to_scan; 1462 unsigned long percent[2]; /* anon @ 0; file @ 1 */ 1463 enum lru_list l; 1464 unsigned long nr_reclaimed = sc->nr_reclaimed; 1465 unsigned long swap_cluster_max = sc->swap_cluster_max; 1466 1467 get_scan_ratio(zone, sc, percent); 1468 1469 for_each_evictable_lru(l) { 1470 int file = is_file_lru(l); 1471 int scan; 1472 1473 scan = zone_nr_pages(zone, sc, l); 1474 if (priority) { 1475 scan >>= priority; 1476 scan = (scan * percent[file]) / 100; 1477 } 1478 if (scanning_global_lru(sc)) { 1479 zone->lru[l].nr_scan += scan; 1480 nr[l] = zone->lru[l].nr_scan; 1481 if (nr[l] >= swap_cluster_max) 1482 zone->lru[l].nr_scan = 0; 1483 else 1484 nr[l] = 0; 1485 } else 1486 nr[l] = scan; 1487 } 1488 1489 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1490 nr[LRU_INACTIVE_FILE]) { 1491 for_each_evictable_lru(l) { 1492 if (nr[l]) { 1493 nr_to_scan = min(nr[l], swap_cluster_max); 1494 nr[l] -= nr_to_scan; 1495 1496 nr_reclaimed += shrink_list(l, nr_to_scan, 1497 zone, sc, priority); 1498 } 1499 } 1500 /* 1501 * On large memory systems, scan >> priority can become 1502 * really large. This is fine for the starting priority; 1503 * we want to put equal scanning pressure on each zone. 1504 * However, if the VM has a harder time of freeing pages, 1505 * with multiple processes reclaiming pages, the total 1506 * freeing target can get unreasonably large. 1507 */ 1508 if (nr_reclaimed > swap_cluster_max && 1509 priority < DEF_PRIORITY && !current_is_kswapd()) 1510 break; 1511 } 1512 1513 sc->nr_reclaimed = nr_reclaimed; 1514 1515 /* 1516 * Even if we did not try to evict anon pages at all, we want to 1517 * rebalance the anon lru active/inactive ratio. 1518 */ 1519 if (inactive_anon_is_low(zone, sc)) 1520 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1521 1522 throttle_vm_writeout(sc->gfp_mask); 1523 } 1524 1525 /* 1526 * This is the direct reclaim path, for page-allocating processes. We only 1527 * try to reclaim pages from zones which will satisfy the caller's allocation 1528 * request. 1529 * 1530 * We reclaim from a zone even if that zone is over pages_high. Because: 1531 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1532 * allocation or 1533 * b) The zones may be over pages_high but they must go *over* pages_high to 1534 * satisfy the `incremental min' zone defense algorithm. 1535 * 1536 * If a zone is deemed to be full of pinned pages then just give it a light 1537 * scan then give up on it. 1538 */ 1539 static void shrink_zones(int priority, struct zonelist *zonelist, 1540 struct scan_control *sc) 1541 { 1542 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); 1543 struct zoneref *z; 1544 struct zone *zone; 1545 1546 sc->all_unreclaimable = 1; 1547 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, 1548 sc->nodemask) { 1549 if (!populated_zone(zone)) 1550 continue; 1551 /* 1552 * Take care memory controller reclaiming has small influence 1553 * to global LRU. 1554 */ 1555 if (scanning_global_lru(sc)) { 1556 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1557 continue; 1558 note_zone_scanning_priority(zone, priority); 1559 1560 if (zone_is_all_unreclaimable(zone) && 1561 priority != DEF_PRIORITY) 1562 continue; /* Let kswapd poll it */ 1563 sc->all_unreclaimable = 0; 1564 } else { 1565 /* 1566 * Ignore cpuset limitation here. We just want to reduce 1567 * # of used pages by us regardless of memory shortage. 1568 */ 1569 sc->all_unreclaimable = 0; 1570 mem_cgroup_note_reclaim_priority(sc->mem_cgroup, 1571 priority); 1572 } 1573 1574 shrink_zone(priority, zone, sc); 1575 } 1576 } 1577 1578 /* 1579 * This is the main entry point to direct page reclaim. 1580 * 1581 * If a full scan of the inactive list fails to free enough memory then we 1582 * are "out of memory" and something needs to be killed. 1583 * 1584 * If the caller is !__GFP_FS then the probability of a failure is reasonably 1585 * high - the zone may be full of dirty or under-writeback pages, which this 1586 * caller can't do much about. We kick pdflush and take explicit naps in the 1587 * hope that some of these pages can be written. But if the allocating task 1588 * holds filesystem locks which prevent writeout this might not work, and the 1589 * allocation attempt will fail. 1590 * 1591 * returns: 0, if no pages reclaimed 1592 * else, the number of pages reclaimed 1593 */ 1594 static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 1595 struct scan_control *sc) 1596 { 1597 int priority; 1598 unsigned long ret = 0; 1599 unsigned long total_scanned = 0; 1600 struct reclaim_state *reclaim_state = current->reclaim_state; 1601 unsigned long lru_pages = 0; 1602 struct zoneref *z; 1603 struct zone *zone; 1604 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); 1605 1606 delayacct_freepages_start(); 1607 1608 if (scanning_global_lru(sc)) 1609 count_vm_event(ALLOCSTALL); 1610 /* 1611 * mem_cgroup will not do shrink_slab. 1612 */ 1613 if (scanning_global_lru(sc)) { 1614 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { 1615 1616 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1617 continue; 1618 1619 lru_pages += zone_lru_pages(zone); 1620 } 1621 } 1622 1623 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1624 sc->nr_scanned = 0; 1625 if (!priority) 1626 disable_swap_token(); 1627 shrink_zones(priority, zonelist, sc); 1628 /* 1629 * Don't shrink slabs when reclaiming memory from 1630 * over limit cgroups 1631 */ 1632 if (scanning_global_lru(sc)) { 1633 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 1634 if (reclaim_state) { 1635 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 1636 reclaim_state->reclaimed_slab = 0; 1637 } 1638 } 1639 total_scanned += sc->nr_scanned; 1640 if (sc->nr_reclaimed >= sc->swap_cluster_max) { 1641 ret = sc->nr_reclaimed; 1642 goto out; 1643 } 1644 1645 /* 1646 * Try to write back as many pages as we just scanned. This 1647 * tends to cause slow streaming writers to write data to the 1648 * disk smoothly, at the dirtying rate, which is nice. But 1649 * that's undesirable in laptop mode, where we *want* lumpy 1650 * writeout. So in laptop mode, write out the whole world. 1651 */ 1652 if (total_scanned > sc->swap_cluster_max + 1653 sc->swap_cluster_max / 2) { 1654 wakeup_pdflush(laptop_mode ? 0 : total_scanned); 1655 sc->may_writepage = 1; 1656 } 1657 1658 /* Take a nap, wait for some writeback to complete */ 1659 if (sc->nr_scanned && priority < DEF_PRIORITY - 2) 1660 congestion_wait(WRITE, HZ/10); 1661 } 1662 /* top priority shrink_zones still had more to do? don't OOM, then */ 1663 if (!sc->all_unreclaimable && scanning_global_lru(sc)) 1664 ret = sc->nr_reclaimed; 1665 out: 1666 /* 1667 * Now that we've scanned all the zones at this priority level, note 1668 * that level within the zone so that the next thread which performs 1669 * scanning of this zone will immediately start out at this priority 1670 * level. This affects only the decision whether or not to bring 1671 * mapped pages onto the inactive list. 1672 */ 1673 if (priority < 0) 1674 priority = 0; 1675 1676 if (scanning_global_lru(sc)) { 1677 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { 1678 1679 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1680 continue; 1681 1682 zone->prev_priority = priority; 1683 } 1684 } else 1685 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority); 1686 1687 delayacct_freepages_end(); 1688 1689 return ret; 1690 } 1691 1692 unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 1693 gfp_t gfp_mask, nodemask_t *nodemask) 1694 { 1695 struct scan_control sc = { 1696 .gfp_mask = gfp_mask, 1697 .may_writepage = !laptop_mode, 1698 .swap_cluster_max = SWAP_CLUSTER_MAX, 1699 .may_unmap = 1, 1700 .swappiness = vm_swappiness, 1701 .order = order, 1702 .mem_cgroup = NULL, 1703 .isolate_pages = isolate_pages_global, 1704 .nodemask = nodemask, 1705 }; 1706 1707 return do_try_to_free_pages(zonelist, &sc); 1708 } 1709 1710 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1711 1712 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 1713 gfp_t gfp_mask, 1714 bool noswap, 1715 unsigned int swappiness) 1716 { 1717 struct scan_control sc = { 1718 .may_writepage = !laptop_mode, 1719 .may_unmap = 1, 1720 .swap_cluster_max = SWAP_CLUSTER_MAX, 1721 .swappiness = swappiness, 1722 .order = 0, 1723 .mem_cgroup = mem_cont, 1724 .isolate_pages = mem_cgroup_isolate_pages, 1725 .nodemask = NULL, /* we don't care the placement */ 1726 }; 1727 struct zonelist *zonelist; 1728 1729 if (noswap) 1730 sc.may_unmap = 0; 1731 1732 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 1733 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 1734 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 1735 return do_try_to_free_pages(zonelist, &sc); 1736 } 1737 #endif 1738 1739 /* 1740 * For kswapd, balance_pgdat() will work across all this node's zones until 1741 * they are all at pages_high. 1742 * 1743 * Returns the number of pages which were actually freed. 1744 * 1745 * There is special handling here for zones which are full of pinned pages. 1746 * This can happen if the pages are all mlocked, or if they are all used by 1747 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 1748 * What we do is to detect the case where all pages in the zone have been 1749 * scanned twice and there has been zero successful reclaim. Mark the zone as 1750 * dead and from now on, only perform a short scan. Basically we're polling 1751 * the zone for when the problem goes away. 1752 * 1753 * kswapd scans the zones in the highmem->normal->dma direction. It skips 1754 * zones which have free_pages > pages_high, but once a zone is found to have 1755 * free_pages <= pages_high, we scan that zone and the lower zones regardless 1756 * of the number of free pages in the lower zones. This interoperates with 1757 * the page allocator fallback scheme to ensure that aging of pages is balanced 1758 * across the zones. 1759 */ 1760 static unsigned long balance_pgdat(pg_data_t *pgdat, int order) 1761 { 1762 int all_zones_ok; 1763 int priority; 1764 int i; 1765 unsigned long total_scanned; 1766 struct reclaim_state *reclaim_state = current->reclaim_state; 1767 struct scan_control sc = { 1768 .gfp_mask = GFP_KERNEL, 1769 .may_unmap = 1, 1770 .swap_cluster_max = SWAP_CLUSTER_MAX, 1771 .swappiness = vm_swappiness, 1772 .order = order, 1773 .mem_cgroup = NULL, 1774 .isolate_pages = isolate_pages_global, 1775 }; 1776 /* 1777 * temp_priority is used to remember the scanning priority at which 1778 * this zone was successfully refilled to free_pages == pages_high. 1779 */ 1780 int temp_priority[MAX_NR_ZONES]; 1781 1782 loop_again: 1783 total_scanned = 0; 1784 sc.nr_reclaimed = 0; 1785 sc.may_writepage = !laptop_mode; 1786 count_vm_event(PAGEOUTRUN); 1787 1788 for (i = 0; i < pgdat->nr_zones; i++) 1789 temp_priority[i] = DEF_PRIORITY; 1790 1791 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1792 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 1793 unsigned long lru_pages = 0; 1794 1795 /* The swap token gets in the way of swapout... */ 1796 if (!priority) 1797 disable_swap_token(); 1798 1799 all_zones_ok = 1; 1800 1801 /* 1802 * Scan in the highmem->dma direction for the highest 1803 * zone which needs scanning 1804 */ 1805 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 1806 struct zone *zone = pgdat->node_zones + i; 1807 1808 if (!populated_zone(zone)) 1809 continue; 1810 1811 if (zone_is_all_unreclaimable(zone) && 1812 priority != DEF_PRIORITY) 1813 continue; 1814 1815 /* 1816 * Do some background aging of the anon list, to give 1817 * pages a chance to be referenced before reclaiming. 1818 */ 1819 if (inactive_anon_is_low(zone, &sc)) 1820 shrink_active_list(SWAP_CLUSTER_MAX, zone, 1821 &sc, priority, 0); 1822 1823 if (!zone_watermark_ok(zone, order, zone->pages_high, 1824 0, 0)) { 1825 end_zone = i; 1826 break; 1827 } 1828 } 1829 if (i < 0) 1830 goto out; 1831 1832 for (i = 0; i <= end_zone; i++) { 1833 struct zone *zone = pgdat->node_zones + i; 1834 1835 lru_pages += zone_lru_pages(zone); 1836 } 1837 1838 /* 1839 * Now scan the zone in the dma->highmem direction, stopping 1840 * at the last zone which needs scanning. 1841 * 1842 * We do this because the page allocator works in the opposite 1843 * direction. This prevents the page allocator from allocating 1844 * pages behind kswapd's direction of progress, which would 1845 * cause too much scanning of the lower zones. 1846 */ 1847 for (i = 0; i <= end_zone; i++) { 1848 struct zone *zone = pgdat->node_zones + i; 1849 int nr_slab; 1850 1851 if (!populated_zone(zone)) 1852 continue; 1853 1854 if (zone_is_all_unreclaimable(zone) && 1855 priority != DEF_PRIORITY) 1856 continue; 1857 1858 if (!zone_watermark_ok(zone, order, zone->pages_high, 1859 end_zone, 0)) 1860 all_zones_ok = 0; 1861 temp_priority[i] = priority; 1862 sc.nr_scanned = 0; 1863 note_zone_scanning_priority(zone, priority); 1864 /* 1865 * We put equal pressure on every zone, unless one 1866 * zone has way too many pages free already. 1867 */ 1868 if (!zone_watermark_ok(zone, order, 8*zone->pages_high, 1869 end_zone, 0)) 1870 shrink_zone(priority, zone, &sc); 1871 reclaim_state->reclaimed_slab = 0; 1872 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 1873 lru_pages); 1874 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 1875 total_scanned += sc.nr_scanned; 1876 if (zone_is_all_unreclaimable(zone)) 1877 continue; 1878 if (nr_slab == 0 && zone->pages_scanned >= 1879 (zone_lru_pages(zone) * 6)) 1880 zone_set_flag(zone, 1881 ZONE_ALL_UNRECLAIMABLE); 1882 /* 1883 * If we've done a decent amount of scanning and 1884 * the reclaim ratio is low, start doing writepage 1885 * even in laptop mode 1886 */ 1887 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 1888 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 1889 sc.may_writepage = 1; 1890 } 1891 if (all_zones_ok) 1892 break; /* kswapd: all done */ 1893 /* 1894 * OK, kswapd is getting into trouble. Take a nap, then take 1895 * another pass across the zones. 1896 */ 1897 if (total_scanned && priority < DEF_PRIORITY - 2) 1898 congestion_wait(WRITE, HZ/10); 1899 1900 /* 1901 * We do this so kswapd doesn't build up large priorities for 1902 * example when it is freeing in parallel with allocators. It 1903 * matches the direct reclaim path behaviour in terms of impact 1904 * on zone->*_priority. 1905 */ 1906 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 1907 break; 1908 } 1909 out: 1910 /* 1911 * Note within each zone the priority level at which this zone was 1912 * brought into a happy state. So that the next thread which scans this 1913 * zone will start out at that priority level. 1914 */ 1915 for (i = 0; i < pgdat->nr_zones; i++) { 1916 struct zone *zone = pgdat->node_zones + i; 1917 1918 zone->prev_priority = temp_priority[i]; 1919 } 1920 if (!all_zones_ok) { 1921 cond_resched(); 1922 1923 try_to_freeze(); 1924 1925 /* 1926 * Fragmentation may mean that the system cannot be 1927 * rebalanced for high-order allocations in all zones. 1928 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 1929 * it means the zones have been fully scanned and are still 1930 * not balanced. For high-order allocations, there is 1931 * little point trying all over again as kswapd may 1932 * infinite loop. 1933 * 1934 * Instead, recheck all watermarks at order-0 as they 1935 * are the most important. If watermarks are ok, kswapd will go 1936 * back to sleep. High-order users can still perform direct 1937 * reclaim if they wish. 1938 */ 1939 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 1940 order = sc.order = 0; 1941 1942 goto loop_again; 1943 } 1944 1945 return sc.nr_reclaimed; 1946 } 1947 1948 /* 1949 * The background pageout daemon, started as a kernel thread 1950 * from the init process. 1951 * 1952 * This basically trickles out pages so that we have _some_ 1953 * free memory available even if there is no other activity 1954 * that frees anything up. This is needed for things like routing 1955 * etc, where we otherwise might have all activity going on in 1956 * asynchronous contexts that cannot page things out. 1957 * 1958 * If there are applications that are active memory-allocators 1959 * (most normal use), this basically shouldn't matter. 1960 */ 1961 static int kswapd(void *p) 1962 { 1963 unsigned long order; 1964 pg_data_t *pgdat = (pg_data_t*)p; 1965 struct task_struct *tsk = current; 1966 DEFINE_WAIT(wait); 1967 struct reclaim_state reclaim_state = { 1968 .reclaimed_slab = 0, 1969 }; 1970 node_to_cpumask_ptr(cpumask, pgdat->node_id); 1971 1972 lockdep_set_current_reclaim_state(GFP_KERNEL); 1973 1974 if (!cpumask_empty(cpumask)) 1975 set_cpus_allowed_ptr(tsk, cpumask); 1976 current->reclaim_state = &reclaim_state; 1977 1978 /* 1979 * Tell the memory management that we're a "memory allocator", 1980 * and that if we need more memory we should get access to it 1981 * regardless (see "__alloc_pages()"). "kswapd" should 1982 * never get caught in the normal page freeing logic. 1983 * 1984 * (Kswapd normally doesn't need memory anyway, but sometimes 1985 * you need a small amount of memory in order to be able to 1986 * page out something else, and this flag essentially protects 1987 * us from recursively trying to free more memory as we're 1988 * trying to free the first piece of memory in the first place). 1989 */ 1990 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 1991 set_freezable(); 1992 1993 order = 0; 1994 for ( ; ; ) { 1995 unsigned long new_order; 1996 1997 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 1998 new_order = pgdat->kswapd_max_order; 1999 pgdat->kswapd_max_order = 0; 2000 if (order < new_order) { 2001 /* 2002 * Don't sleep if someone wants a larger 'order' 2003 * allocation 2004 */ 2005 order = new_order; 2006 } else { 2007 if (!freezing(current)) 2008 schedule(); 2009 2010 order = pgdat->kswapd_max_order; 2011 } 2012 finish_wait(&pgdat->kswapd_wait, &wait); 2013 2014 if (!try_to_freeze()) { 2015 /* We can speed up thawing tasks if we don't call 2016 * balance_pgdat after returning from the refrigerator 2017 */ 2018 balance_pgdat(pgdat, order); 2019 } 2020 } 2021 return 0; 2022 } 2023 2024 /* 2025 * A zone is low on free memory, so wake its kswapd task to service it. 2026 */ 2027 void wakeup_kswapd(struct zone *zone, int order) 2028 { 2029 pg_data_t *pgdat; 2030 2031 if (!populated_zone(zone)) 2032 return; 2033 2034 pgdat = zone->zone_pgdat; 2035 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) 2036 return; 2037 if (pgdat->kswapd_max_order < order) 2038 pgdat->kswapd_max_order = order; 2039 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2040 return; 2041 if (!waitqueue_active(&pgdat->kswapd_wait)) 2042 return; 2043 wake_up_interruptible(&pgdat->kswapd_wait); 2044 } 2045 2046 unsigned long global_lru_pages(void) 2047 { 2048 return global_page_state(NR_ACTIVE_ANON) 2049 + global_page_state(NR_ACTIVE_FILE) 2050 + global_page_state(NR_INACTIVE_ANON) 2051 + global_page_state(NR_INACTIVE_FILE); 2052 } 2053 2054 #ifdef CONFIG_PM 2055 /* 2056 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages 2057 * from LRU lists system-wide, for given pass and priority. 2058 * 2059 * For pass > 3 we also try to shrink the LRU lists that contain a few pages 2060 */ 2061 static void shrink_all_zones(unsigned long nr_pages, int prio, 2062 int pass, struct scan_control *sc) 2063 { 2064 struct zone *zone; 2065 unsigned long nr_reclaimed = 0; 2066 2067 for_each_populated_zone(zone) { 2068 enum lru_list l; 2069 2070 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY) 2071 continue; 2072 2073 for_each_evictable_lru(l) { 2074 enum zone_stat_item ls = NR_LRU_BASE + l; 2075 unsigned long lru_pages = zone_page_state(zone, ls); 2076 2077 /* For pass = 0, we don't shrink the active list */ 2078 if (pass == 0 && (l == LRU_ACTIVE_ANON || 2079 l == LRU_ACTIVE_FILE)) 2080 continue; 2081 2082 zone->lru[l].nr_scan += (lru_pages >> prio) + 1; 2083 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) { 2084 unsigned long nr_to_scan; 2085 2086 zone->lru[l].nr_scan = 0; 2087 nr_to_scan = min(nr_pages, lru_pages); 2088 nr_reclaimed += shrink_list(l, nr_to_scan, zone, 2089 sc, prio); 2090 if (nr_reclaimed >= nr_pages) { 2091 sc->nr_reclaimed = nr_reclaimed; 2092 return; 2093 } 2094 } 2095 } 2096 } 2097 sc->nr_reclaimed = nr_reclaimed; 2098 } 2099 2100 /* 2101 * Try to free `nr_pages' of memory, system-wide, and return the number of 2102 * freed pages. 2103 * 2104 * Rather than trying to age LRUs the aim is to preserve the overall 2105 * LRU order by reclaiming preferentially 2106 * inactive > active > active referenced > active mapped 2107 */ 2108 unsigned long shrink_all_memory(unsigned long nr_pages) 2109 { 2110 unsigned long lru_pages, nr_slab; 2111 int pass; 2112 struct reclaim_state reclaim_state; 2113 struct scan_control sc = { 2114 .gfp_mask = GFP_KERNEL, 2115 .may_unmap = 0, 2116 .may_writepage = 1, 2117 .isolate_pages = isolate_pages_global, 2118 }; 2119 2120 current->reclaim_state = &reclaim_state; 2121 2122 lru_pages = global_lru_pages(); 2123 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE); 2124 /* If slab caches are huge, it's better to hit them first */ 2125 while (nr_slab >= lru_pages) { 2126 reclaim_state.reclaimed_slab = 0; 2127 shrink_slab(nr_pages, sc.gfp_mask, lru_pages); 2128 if (!reclaim_state.reclaimed_slab) 2129 break; 2130 2131 sc.nr_reclaimed += reclaim_state.reclaimed_slab; 2132 if (sc.nr_reclaimed >= nr_pages) 2133 goto out; 2134 2135 nr_slab -= reclaim_state.reclaimed_slab; 2136 } 2137 2138 /* 2139 * We try to shrink LRUs in 5 passes: 2140 * 0 = Reclaim from inactive_list only 2141 * 1 = Reclaim from active list but don't reclaim mapped 2142 * 2 = 2nd pass of type 1 2143 * 3 = Reclaim mapped (normal reclaim) 2144 * 4 = 2nd pass of type 3 2145 */ 2146 for (pass = 0; pass < 5; pass++) { 2147 int prio; 2148 2149 /* Force reclaiming mapped pages in the passes #3 and #4 */ 2150 if (pass > 2) 2151 sc.may_unmap = 1; 2152 2153 for (prio = DEF_PRIORITY; prio >= 0; prio--) { 2154 unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed; 2155 2156 sc.nr_scanned = 0; 2157 sc.swap_cluster_max = nr_to_scan; 2158 shrink_all_zones(nr_to_scan, prio, pass, &sc); 2159 if (sc.nr_reclaimed >= nr_pages) 2160 goto out; 2161 2162 reclaim_state.reclaimed_slab = 0; 2163 shrink_slab(sc.nr_scanned, sc.gfp_mask, 2164 global_lru_pages()); 2165 sc.nr_reclaimed += reclaim_state.reclaimed_slab; 2166 if (sc.nr_reclaimed >= nr_pages) 2167 goto out; 2168 2169 if (sc.nr_scanned && prio < DEF_PRIORITY - 2) 2170 congestion_wait(WRITE, HZ / 10); 2171 } 2172 } 2173 2174 /* 2175 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be 2176 * something in slab caches 2177 */ 2178 if (!sc.nr_reclaimed) { 2179 do { 2180 reclaim_state.reclaimed_slab = 0; 2181 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages()); 2182 sc.nr_reclaimed += reclaim_state.reclaimed_slab; 2183 } while (sc.nr_reclaimed < nr_pages && 2184 reclaim_state.reclaimed_slab > 0); 2185 } 2186 2187 2188 out: 2189 current->reclaim_state = NULL; 2190 2191 return sc.nr_reclaimed; 2192 } 2193 #endif 2194 2195 /* It's optimal to keep kswapds on the same CPUs as their memory, but 2196 not required for correctness. So if the last cpu in a node goes 2197 away, we get changed to run anywhere: as the first one comes back, 2198 restore their cpu bindings. */ 2199 static int __devinit cpu_callback(struct notifier_block *nfb, 2200 unsigned long action, void *hcpu) 2201 { 2202 int nid; 2203 2204 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2205 for_each_node_state(nid, N_HIGH_MEMORY) { 2206 pg_data_t *pgdat = NODE_DATA(nid); 2207 node_to_cpumask_ptr(mask, pgdat->node_id); 2208 2209 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2210 /* One of our CPUs online: restore mask */ 2211 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2212 } 2213 } 2214 return NOTIFY_OK; 2215 } 2216 2217 /* 2218 * This kswapd start function will be called by init and node-hot-add. 2219 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2220 */ 2221 int kswapd_run(int nid) 2222 { 2223 pg_data_t *pgdat = NODE_DATA(nid); 2224 int ret = 0; 2225 2226 if (pgdat->kswapd) 2227 return 0; 2228 2229 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2230 if (IS_ERR(pgdat->kswapd)) { 2231 /* failure at boot is fatal */ 2232 BUG_ON(system_state == SYSTEM_BOOTING); 2233 printk("Failed to start kswapd on node %d\n",nid); 2234 ret = -1; 2235 } 2236 return ret; 2237 } 2238 2239 static int __init kswapd_init(void) 2240 { 2241 int nid; 2242 2243 swap_setup(); 2244 for_each_node_state(nid, N_HIGH_MEMORY) 2245 kswapd_run(nid); 2246 hotcpu_notifier(cpu_callback, 0); 2247 return 0; 2248 } 2249 2250 module_init(kswapd_init) 2251 2252 #ifdef CONFIG_NUMA 2253 /* 2254 * Zone reclaim mode 2255 * 2256 * If non-zero call zone_reclaim when the number of free pages falls below 2257 * the watermarks. 2258 */ 2259 int zone_reclaim_mode __read_mostly; 2260 2261 #define RECLAIM_OFF 0 2262 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2263 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2264 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2265 2266 /* 2267 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2268 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2269 * a zone. 2270 */ 2271 #define ZONE_RECLAIM_PRIORITY 4 2272 2273 /* 2274 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2275 * occur. 2276 */ 2277 int sysctl_min_unmapped_ratio = 1; 2278 2279 /* 2280 * If the number of slab pages in a zone grows beyond this percentage then 2281 * slab reclaim needs to occur. 2282 */ 2283 int sysctl_min_slab_ratio = 5; 2284 2285 /* 2286 * Try to free up some pages from this zone through reclaim. 2287 */ 2288 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2289 { 2290 /* Minimum pages needed in order to stay on node */ 2291 const unsigned long nr_pages = 1 << order; 2292 struct task_struct *p = current; 2293 struct reclaim_state reclaim_state; 2294 int priority; 2295 struct scan_control sc = { 2296 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2297 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2298 .swap_cluster_max = max_t(unsigned long, nr_pages, 2299 SWAP_CLUSTER_MAX), 2300 .gfp_mask = gfp_mask, 2301 .swappiness = vm_swappiness, 2302 .order = order, 2303 .isolate_pages = isolate_pages_global, 2304 }; 2305 unsigned long slab_reclaimable; 2306 2307 disable_swap_token(); 2308 cond_resched(); 2309 /* 2310 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2311 * and we also need to be able to write out pages for RECLAIM_WRITE 2312 * and RECLAIM_SWAP. 2313 */ 2314 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2315 reclaim_state.reclaimed_slab = 0; 2316 p->reclaim_state = &reclaim_state; 2317 2318 if (zone_page_state(zone, NR_FILE_PAGES) - 2319 zone_page_state(zone, NR_FILE_MAPPED) > 2320 zone->min_unmapped_pages) { 2321 /* 2322 * Free memory by calling shrink zone with increasing 2323 * priorities until we have enough memory freed. 2324 */ 2325 priority = ZONE_RECLAIM_PRIORITY; 2326 do { 2327 note_zone_scanning_priority(zone, priority); 2328 shrink_zone(priority, zone, &sc); 2329 priority--; 2330 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 2331 } 2332 2333 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2334 if (slab_reclaimable > zone->min_slab_pages) { 2335 /* 2336 * shrink_slab() does not currently allow us to determine how 2337 * many pages were freed in this zone. So we take the current 2338 * number of slab pages and shake the slab until it is reduced 2339 * by the same nr_pages that we used for reclaiming unmapped 2340 * pages. 2341 * 2342 * Note that shrink_slab will free memory on all zones and may 2343 * take a long time. 2344 */ 2345 while (shrink_slab(sc.nr_scanned, gfp_mask, order) && 2346 zone_page_state(zone, NR_SLAB_RECLAIMABLE) > 2347 slab_reclaimable - nr_pages) 2348 ; 2349 2350 /* 2351 * Update nr_reclaimed by the number of slab pages we 2352 * reclaimed from this zone. 2353 */ 2354 sc.nr_reclaimed += slab_reclaimable - 2355 zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2356 } 2357 2358 p->reclaim_state = NULL; 2359 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 2360 return sc.nr_reclaimed >= nr_pages; 2361 } 2362 2363 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2364 { 2365 int node_id; 2366 int ret; 2367 2368 /* 2369 * Zone reclaim reclaims unmapped file backed pages and 2370 * slab pages if we are over the defined limits. 2371 * 2372 * A small portion of unmapped file backed pages is needed for 2373 * file I/O otherwise pages read by file I/O will be immediately 2374 * thrown out if the zone is overallocated. So we do not reclaim 2375 * if less than a specified percentage of the zone is used by 2376 * unmapped file backed pages. 2377 */ 2378 if (zone_page_state(zone, NR_FILE_PAGES) - 2379 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages 2380 && zone_page_state(zone, NR_SLAB_RECLAIMABLE) 2381 <= zone->min_slab_pages) 2382 return 0; 2383 2384 if (zone_is_all_unreclaimable(zone)) 2385 return 0; 2386 2387 /* 2388 * Do not scan if the allocation should not be delayed. 2389 */ 2390 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 2391 return 0; 2392 2393 /* 2394 * Only run zone reclaim on the local zone or on zones that do not 2395 * have associated processors. This will favor the local processor 2396 * over remote processors and spread off node memory allocations 2397 * as wide as possible. 2398 */ 2399 node_id = zone_to_nid(zone); 2400 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 2401 return 0; 2402 2403 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 2404 return 0; 2405 ret = __zone_reclaim(zone, gfp_mask, order); 2406 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 2407 2408 return ret; 2409 } 2410 #endif 2411 2412 #ifdef CONFIG_UNEVICTABLE_LRU 2413 /* 2414 * page_evictable - test whether a page is evictable 2415 * @page: the page to test 2416 * @vma: the VMA in which the page is or will be mapped, may be NULL 2417 * 2418 * Test whether page is evictable--i.e., should be placed on active/inactive 2419 * lists vs unevictable list. The vma argument is !NULL when called from the 2420 * fault path to determine how to instantate a new page. 2421 * 2422 * Reasons page might not be evictable: 2423 * (1) page's mapping marked unevictable 2424 * (2) page is part of an mlocked VMA 2425 * 2426 */ 2427 int page_evictable(struct page *page, struct vm_area_struct *vma) 2428 { 2429 2430 if (mapping_unevictable(page_mapping(page))) 2431 return 0; 2432 2433 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 2434 return 0; 2435 2436 return 1; 2437 } 2438 2439 /** 2440 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 2441 * @page: page to check evictability and move to appropriate lru list 2442 * @zone: zone page is in 2443 * 2444 * Checks a page for evictability and moves the page to the appropriate 2445 * zone lru list. 2446 * 2447 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 2448 * have PageUnevictable set. 2449 */ 2450 static void check_move_unevictable_page(struct page *page, struct zone *zone) 2451 { 2452 VM_BUG_ON(PageActive(page)); 2453 2454 retry: 2455 ClearPageUnevictable(page); 2456 if (page_evictable(page, NULL)) { 2457 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page); 2458 2459 __dec_zone_state(zone, NR_UNEVICTABLE); 2460 list_move(&page->lru, &zone->lru[l].list); 2461 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 2462 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 2463 __count_vm_event(UNEVICTABLE_PGRESCUED); 2464 } else { 2465 /* 2466 * rotate unevictable list 2467 */ 2468 SetPageUnevictable(page); 2469 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 2470 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 2471 if (page_evictable(page, NULL)) 2472 goto retry; 2473 } 2474 } 2475 2476 /** 2477 * scan_mapping_unevictable_pages - scan an address space for evictable pages 2478 * @mapping: struct address_space to scan for evictable pages 2479 * 2480 * Scan all pages in mapping. Check unevictable pages for 2481 * evictability and move them to the appropriate zone lru list. 2482 */ 2483 void scan_mapping_unevictable_pages(struct address_space *mapping) 2484 { 2485 pgoff_t next = 0; 2486 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 2487 PAGE_CACHE_SHIFT; 2488 struct zone *zone; 2489 struct pagevec pvec; 2490 2491 if (mapping->nrpages == 0) 2492 return; 2493 2494 pagevec_init(&pvec, 0); 2495 while (next < end && 2496 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 2497 int i; 2498 int pg_scanned = 0; 2499 2500 zone = NULL; 2501 2502 for (i = 0; i < pagevec_count(&pvec); i++) { 2503 struct page *page = pvec.pages[i]; 2504 pgoff_t page_index = page->index; 2505 struct zone *pagezone = page_zone(page); 2506 2507 pg_scanned++; 2508 if (page_index > next) 2509 next = page_index; 2510 next++; 2511 2512 if (pagezone != zone) { 2513 if (zone) 2514 spin_unlock_irq(&zone->lru_lock); 2515 zone = pagezone; 2516 spin_lock_irq(&zone->lru_lock); 2517 } 2518 2519 if (PageLRU(page) && PageUnevictable(page)) 2520 check_move_unevictable_page(page, zone); 2521 } 2522 if (zone) 2523 spin_unlock_irq(&zone->lru_lock); 2524 pagevec_release(&pvec); 2525 2526 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 2527 } 2528 2529 } 2530 2531 /** 2532 * scan_zone_unevictable_pages - check unevictable list for evictable pages 2533 * @zone - zone of which to scan the unevictable list 2534 * 2535 * Scan @zone's unevictable LRU lists to check for pages that have become 2536 * evictable. Move those that have to @zone's inactive list where they 2537 * become candidates for reclaim, unless shrink_inactive_zone() decides 2538 * to reactivate them. Pages that are still unevictable are rotated 2539 * back onto @zone's unevictable list. 2540 */ 2541 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 2542 static void scan_zone_unevictable_pages(struct zone *zone) 2543 { 2544 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 2545 unsigned long scan; 2546 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 2547 2548 while (nr_to_scan > 0) { 2549 unsigned long batch_size = min(nr_to_scan, 2550 SCAN_UNEVICTABLE_BATCH_SIZE); 2551 2552 spin_lock_irq(&zone->lru_lock); 2553 for (scan = 0; scan < batch_size; scan++) { 2554 struct page *page = lru_to_page(l_unevictable); 2555 2556 if (!trylock_page(page)) 2557 continue; 2558 2559 prefetchw_prev_lru_page(page, l_unevictable, flags); 2560 2561 if (likely(PageLRU(page) && PageUnevictable(page))) 2562 check_move_unevictable_page(page, zone); 2563 2564 unlock_page(page); 2565 } 2566 spin_unlock_irq(&zone->lru_lock); 2567 2568 nr_to_scan -= batch_size; 2569 } 2570 } 2571 2572 2573 /** 2574 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 2575 * 2576 * A really big hammer: scan all zones' unevictable LRU lists to check for 2577 * pages that have become evictable. Move those back to the zones' 2578 * inactive list where they become candidates for reclaim. 2579 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 2580 * and we add swap to the system. As such, it runs in the context of a task 2581 * that has possibly/probably made some previously unevictable pages 2582 * evictable. 2583 */ 2584 static void scan_all_zones_unevictable_pages(void) 2585 { 2586 struct zone *zone; 2587 2588 for_each_zone(zone) { 2589 scan_zone_unevictable_pages(zone); 2590 } 2591 } 2592 2593 /* 2594 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 2595 * all nodes' unevictable lists for evictable pages 2596 */ 2597 unsigned long scan_unevictable_pages; 2598 2599 int scan_unevictable_handler(struct ctl_table *table, int write, 2600 struct file *file, void __user *buffer, 2601 size_t *length, loff_t *ppos) 2602 { 2603 proc_doulongvec_minmax(table, write, file, buffer, length, ppos); 2604 2605 if (write && *(unsigned long *)table->data) 2606 scan_all_zones_unevictable_pages(); 2607 2608 scan_unevictable_pages = 0; 2609 return 0; 2610 } 2611 2612 /* 2613 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 2614 * a specified node's per zone unevictable lists for evictable pages. 2615 */ 2616 2617 static ssize_t read_scan_unevictable_node(struct sys_device *dev, 2618 struct sysdev_attribute *attr, 2619 char *buf) 2620 { 2621 return sprintf(buf, "0\n"); /* always zero; should fit... */ 2622 } 2623 2624 static ssize_t write_scan_unevictable_node(struct sys_device *dev, 2625 struct sysdev_attribute *attr, 2626 const char *buf, size_t count) 2627 { 2628 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 2629 struct zone *zone; 2630 unsigned long res; 2631 unsigned long req = strict_strtoul(buf, 10, &res); 2632 2633 if (!req) 2634 return 1; /* zero is no-op */ 2635 2636 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 2637 if (!populated_zone(zone)) 2638 continue; 2639 scan_zone_unevictable_pages(zone); 2640 } 2641 return 1; 2642 } 2643 2644 2645 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 2646 read_scan_unevictable_node, 2647 write_scan_unevictable_node); 2648 2649 int scan_unevictable_register_node(struct node *node) 2650 { 2651 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 2652 } 2653 2654 void scan_unevictable_unregister_node(struct node *node) 2655 { 2656 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 2657 } 2658 2659 #endif 2660