vmscan.c revision 83e33a4711760469f5c3861b8ffea4947656d4eb
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/file.h> 23#include <linux/writeback.h> 24#include <linux/blkdev.h> 25#include <linux/buffer_head.h> /* for try_to_release_page(), 26 buffer_heads_over_limit */ 27#include <linux/mm_inline.h> 28#include <linux/pagevec.h> 29#include <linux/backing-dev.h> 30#include <linux/rmap.h> 31#include <linux/topology.h> 32#include <linux/cpu.h> 33#include <linux/cpuset.h> 34#include <linux/notifier.h> 35#include <linux/rwsem.h> 36#include <linux/delay.h> 37#include <linux/kthread.h> 38 39#include <asm/tlbflush.h> 40#include <asm/div64.h> 41 42#include <linux/swapops.h> 43 44#include "internal.h" 45 46struct scan_control { 47 /* Incremented by the number of inactive pages that were scanned */ 48 unsigned long nr_scanned; 49 50 /* This context's GFP mask */ 51 gfp_t gfp_mask; 52 53 int may_writepage; 54 55 /* Can pages be swapped as part of reclaim? */ 56 int may_swap; 57 58 /* This context's SWAP_CLUSTER_MAX. If freeing memory for 59 * suspend, we effectively ignore SWAP_CLUSTER_MAX. 60 * In this context, it doesn't matter that we scan the 61 * whole list at once. */ 62 int swap_cluster_max; 63 64 int swappiness; 65 66 int all_unreclaimable; 67}; 68 69/* 70 * The list of shrinker callbacks used by to apply pressure to 71 * ageable caches. 72 */ 73struct shrinker { 74 shrinker_t shrinker; 75 struct list_head list; 76 int seeks; /* seeks to recreate an obj */ 77 long nr; /* objs pending delete */ 78}; 79 80#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 81 82#ifdef ARCH_HAS_PREFETCH 83#define prefetch_prev_lru_page(_page, _base, _field) \ 84 do { \ 85 if ((_page)->lru.prev != _base) { \ 86 struct page *prev; \ 87 \ 88 prev = lru_to_page(&(_page->lru)); \ 89 prefetch(&prev->_field); \ 90 } \ 91 } while (0) 92#else 93#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 94#endif 95 96#ifdef ARCH_HAS_PREFETCHW 97#define prefetchw_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 prefetchw(&prev->_field); \ 104 } \ 105 } while (0) 106#else 107#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 108#endif 109 110/* 111 * From 0 .. 100. Higher means more swappy. 112 */ 113int vm_swappiness = 60; 114long vm_total_pages; /* The total number of pages which the VM controls */ 115 116static LIST_HEAD(shrinker_list); 117static DECLARE_RWSEM(shrinker_rwsem); 118 119/* 120 * Add a shrinker callback to be called from the vm 121 */ 122struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) 123{ 124 struct shrinker *shrinker; 125 126 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); 127 if (shrinker) { 128 shrinker->shrinker = theshrinker; 129 shrinker->seeks = seeks; 130 shrinker->nr = 0; 131 down_write(&shrinker_rwsem); 132 list_add_tail(&shrinker->list, &shrinker_list); 133 up_write(&shrinker_rwsem); 134 } 135 return shrinker; 136} 137EXPORT_SYMBOL(set_shrinker); 138 139/* 140 * Remove one 141 */ 142void remove_shrinker(struct shrinker *shrinker) 143{ 144 down_write(&shrinker_rwsem); 145 list_del(&shrinker->list); 146 up_write(&shrinker_rwsem); 147 kfree(shrinker); 148} 149EXPORT_SYMBOL(remove_shrinker); 150 151#define SHRINK_BATCH 128 152/* 153 * Call the shrink functions to age shrinkable caches 154 * 155 * Here we assume it costs one seek to replace a lru page and that it also 156 * takes a seek to recreate a cache object. With this in mind we age equal 157 * percentages of the lru and ageable caches. This should balance the seeks 158 * generated by these structures. 159 * 160 * If the vm encounted mapped pages on the LRU it increase the pressure on 161 * slab to avoid swapping. 162 * 163 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 164 * 165 * `lru_pages' represents the number of on-LRU pages in all the zones which 166 * are eligible for the caller's allocation attempt. It is used for balancing 167 * slab reclaim versus page reclaim. 168 * 169 * Returns the number of slab objects which we shrunk. 170 */ 171unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 172 unsigned long lru_pages) 173{ 174 struct shrinker *shrinker; 175 unsigned long ret = 0; 176 177 if (scanned == 0) 178 scanned = SWAP_CLUSTER_MAX; 179 180 if (!down_read_trylock(&shrinker_rwsem)) 181 return 1; /* Assume we'll be able to shrink next time */ 182 183 list_for_each_entry(shrinker, &shrinker_list, list) { 184 unsigned long long delta; 185 unsigned long total_scan; 186 unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); 187 188 delta = (4 * scanned) / shrinker->seeks; 189 delta *= max_pass; 190 do_div(delta, lru_pages + 1); 191 shrinker->nr += delta; 192 if (shrinker->nr < 0) { 193 printk(KERN_ERR "%s: nr=%ld\n", 194 __FUNCTION__, shrinker->nr); 195 shrinker->nr = max_pass; 196 } 197 198 /* 199 * Avoid risking looping forever due to too large nr value: 200 * never try to free more than twice the estimate number of 201 * freeable entries. 202 */ 203 if (shrinker->nr > max_pass * 2) 204 shrinker->nr = max_pass * 2; 205 206 total_scan = shrinker->nr; 207 shrinker->nr = 0; 208 209 while (total_scan >= SHRINK_BATCH) { 210 long this_scan = SHRINK_BATCH; 211 int shrink_ret; 212 int nr_before; 213 214 nr_before = (*shrinker->shrinker)(0, gfp_mask); 215 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); 216 if (shrink_ret == -1) 217 break; 218 if (shrink_ret < nr_before) 219 ret += nr_before - shrink_ret; 220 count_vm_events(SLABS_SCANNED, this_scan); 221 total_scan -= this_scan; 222 223 cond_resched(); 224 } 225 226 shrinker->nr += total_scan; 227 } 228 up_read(&shrinker_rwsem); 229 return ret; 230} 231 232/* Called without lock on whether page is mapped, so answer is unstable */ 233static inline int page_mapping_inuse(struct page *page) 234{ 235 struct address_space *mapping; 236 237 /* Page is in somebody's page tables. */ 238 if (page_mapped(page)) 239 return 1; 240 241 /* Be more reluctant to reclaim swapcache than pagecache */ 242 if (PageSwapCache(page)) 243 return 1; 244 245 mapping = page_mapping(page); 246 if (!mapping) 247 return 0; 248 249 /* File is mmap'd by somebody? */ 250 return mapping_mapped(mapping); 251} 252 253static inline int is_page_cache_freeable(struct page *page) 254{ 255 return page_count(page) - !!PagePrivate(page) == 2; 256} 257 258static int may_write_to_queue(struct backing_dev_info *bdi) 259{ 260 if (current->flags & PF_SWAPWRITE) 261 return 1; 262 if (!bdi_write_congested(bdi)) 263 return 1; 264 if (bdi == current->backing_dev_info) 265 return 1; 266 return 0; 267} 268 269/* 270 * We detected a synchronous write error writing a page out. Probably 271 * -ENOSPC. We need to propagate that into the address_space for a subsequent 272 * fsync(), msync() or close(). 273 * 274 * The tricky part is that after writepage we cannot touch the mapping: nothing 275 * prevents it from being freed up. But we have a ref on the page and once 276 * that page is locked, the mapping is pinned. 277 * 278 * We're allowed to run sleeping lock_page() here because we know the caller has 279 * __GFP_FS. 280 */ 281static void handle_write_error(struct address_space *mapping, 282 struct page *page, int error) 283{ 284 lock_page(page); 285 if (page_mapping(page) == mapping) { 286 if (error == -ENOSPC) 287 set_bit(AS_ENOSPC, &mapping->flags); 288 else 289 set_bit(AS_EIO, &mapping->flags); 290 } 291 unlock_page(page); 292} 293 294/* possible outcome of pageout() */ 295typedef enum { 296 /* failed to write page out, page is locked */ 297 PAGE_KEEP, 298 /* move page to the active list, page is locked */ 299 PAGE_ACTIVATE, 300 /* page has been sent to the disk successfully, page is unlocked */ 301 PAGE_SUCCESS, 302 /* page is clean and locked */ 303 PAGE_CLEAN, 304} pageout_t; 305 306/* 307 * pageout is called by shrink_page_list() for each dirty page. 308 * Calls ->writepage(). 309 */ 310static pageout_t pageout(struct page *page, struct address_space *mapping) 311{ 312 /* 313 * If the page is dirty, only perform writeback if that write 314 * will be non-blocking. To prevent this allocation from being 315 * stalled by pagecache activity. But note that there may be 316 * stalls if we need to run get_block(). We could test 317 * PagePrivate for that. 318 * 319 * If this process is currently in generic_file_write() against 320 * this page's queue, we can perform writeback even if that 321 * will block. 322 * 323 * If the page is swapcache, write it back even if that would 324 * block, for some throttling. This happens by accident, because 325 * swap_backing_dev_info is bust: it doesn't reflect the 326 * congestion state of the swapdevs. Easy to fix, if needed. 327 * See swapfile.c:page_queue_congested(). 328 */ 329 if (!is_page_cache_freeable(page)) 330 return PAGE_KEEP; 331 if (!mapping) { 332 /* 333 * Some data journaling orphaned pages can have 334 * page->mapping == NULL while being dirty with clean buffers. 335 */ 336 if (PagePrivate(page)) { 337 if (try_to_free_buffers(page)) { 338 ClearPageDirty(page); 339 printk("%s: orphaned page\n", __FUNCTION__); 340 return PAGE_CLEAN; 341 } 342 } 343 return PAGE_KEEP; 344 } 345 if (mapping->a_ops->writepage == NULL) 346 return PAGE_ACTIVATE; 347 if (!may_write_to_queue(mapping->backing_dev_info)) 348 return PAGE_KEEP; 349 350 if (clear_page_dirty_for_io(page)) { 351 int res; 352 struct writeback_control wbc = { 353 .sync_mode = WB_SYNC_NONE, 354 .nr_to_write = SWAP_CLUSTER_MAX, 355 .range_start = 0, 356 .range_end = LLONG_MAX, 357 .nonblocking = 1, 358 .for_reclaim = 1, 359 }; 360 361 SetPageReclaim(page); 362 res = mapping->a_ops->writepage(page, &wbc); 363 if (res < 0) 364 handle_write_error(mapping, page, res); 365 if (res == AOP_WRITEPAGE_ACTIVATE) { 366 ClearPageReclaim(page); 367 return PAGE_ACTIVATE; 368 } 369 if (!PageWriteback(page)) { 370 /* synchronous write or broken a_ops? */ 371 ClearPageReclaim(page); 372 } 373 374 return PAGE_SUCCESS; 375 } 376 377 return PAGE_CLEAN; 378} 379 380int remove_mapping(struct address_space *mapping, struct page *page) 381{ 382 BUG_ON(!PageLocked(page)); 383 BUG_ON(mapping != page_mapping(page)); 384 385 write_lock_irq(&mapping->tree_lock); 386 387 /* 388 * The non-racy check for busy page. It is critical to check 389 * PageDirty _after_ making sure that the page is freeable and 390 * not in use by anybody. (pagecache + us == 2) 391 */ 392 if (unlikely(page_count(page) != 2)) 393 goto cannot_free; 394 smp_rmb(); 395 if (unlikely(PageDirty(page))) 396 goto cannot_free; 397 398 if (PageSwapCache(page)) { 399 swp_entry_t swap = { .val = page_private(page) }; 400 __delete_from_swap_cache(page); 401 write_unlock_irq(&mapping->tree_lock); 402 swap_free(swap); 403 __put_page(page); /* The pagecache ref */ 404 return 1; 405 } 406 407 __remove_from_page_cache(page); 408 write_unlock_irq(&mapping->tree_lock); 409 __put_page(page); 410 return 1; 411 412cannot_free: 413 write_unlock_irq(&mapping->tree_lock); 414 return 0; 415} 416 417/* 418 * shrink_page_list() returns the number of reclaimed pages 419 */ 420static unsigned long shrink_page_list(struct list_head *page_list, 421 struct scan_control *sc) 422{ 423 LIST_HEAD(ret_pages); 424 struct pagevec freed_pvec; 425 int pgactivate = 0; 426 unsigned long nr_reclaimed = 0; 427 428 cond_resched(); 429 430 pagevec_init(&freed_pvec, 1); 431 while (!list_empty(page_list)) { 432 struct address_space *mapping; 433 struct page *page; 434 int may_enter_fs; 435 int referenced; 436 437 cond_resched(); 438 439 page = lru_to_page(page_list); 440 list_del(&page->lru); 441 442 if (TestSetPageLocked(page)) 443 goto keep; 444 445 VM_BUG_ON(PageActive(page)); 446 447 sc->nr_scanned++; 448 449 if (!sc->may_swap && page_mapped(page)) 450 goto keep_locked; 451 452 /* Double the slab pressure for mapped and swapcache pages */ 453 if (page_mapped(page) || PageSwapCache(page)) 454 sc->nr_scanned++; 455 456 if (PageWriteback(page)) 457 goto keep_locked; 458 459 referenced = page_referenced(page, 1); 460 /* In active use or really unfreeable? Activate it. */ 461 if (referenced && page_mapping_inuse(page)) 462 goto activate_locked; 463 464#ifdef CONFIG_SWAP 465 /* 466 * Anonymous process memory has backing store? 467 * Try to allocate it some swap space here. 468 */ 469 if (PageAnon(page) && !PageSwapCache(page)) 470 if (!add_to_swap(page, GFP_ATOMIC)) 471 goto activate_locked; 472#endif /* CONFIG_SWAP */ 473 474 mapping = page_mapping(page); 475 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 476 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 477 478 /* 479 * The page is mapped into the page tables of one or more 480 * processes. Try to unmap it here. 481 */ 482 if (page_mapped(page) && mapping) { 483 switch (try_to_unmap(page, 0)) { 484 case SWAP_FAIL: 485 goto activate_locked; 486 case SWAP_AGAIN: 487 goto keep_locked; 488 case SWAP_SUCCESS: 489 ; /* try to free the page below */ 490 } 491 } 492 493 if (PageDirty(page)) { 494 if (referenced) 495 goto keep_locked; 496 if (!may_enter_fs) 497 goto keep_locked; 498 if (!sc->may_writepage) 499 goto keep_locked; 500 501 /* Page is dirty, try to write it out here */ 502 switch(pageout(page, mapping)) { 503 case PAGE_KEEP: 504 goto keep_locked; 505 case PAGE_ACTIVATE: 506 goto activate_locked; 507 case PAGE_SUCCESS: 508 if (PageWriteback(page) || PageDirty(page)) 509 goto keep; 510 /* 511 * A synchronous write - probably a ramdisk. Go 512 * ahead and try to reclaim the page. 513 */ 514 if (TestSetPageLocked(page)) 515 goto keep; 516 if (PageDirty(page) || PageWriteback(page)) 517 goto keep_locked; 518 mapping = page_mapping(page); 519 case PAGE_CLEAN: 520 ; /* try to free the page below */ 521 } 522 } 523 524 /* 525 * If the page has buffers, try to free the buffer mappings 526 * associated with this page. If we succeed we try to free 527 * the page as well. 528 * 529 * We do this even if the page is PageDirty(). 530 * try_to_release_page() does not perform I/O, but it is 531 * possible for a page to have PageDirty set, but it is actually 532 * clean (all its buffers are clean). This happens if the 533 * buffers were written out directly, with submit_bh(). ext3 534 * will do this, as well as the blockdev mapping. 535 * try_to_release_page() will discover that cleanness and will 536 * drop the buffers and mark the page clean - it can be freed. 537 * 538 * Rarely, pages can have buffers and no ->mapping. These are 539 * the pages which were not successfully invalidated in 540 * truncate_complete_page(). We try to drop those buffers here 541 * and if that worked, and the page is no longer mapped into 542 * process address space (page_count == 1) it can be freed. 543 * Otherwise, leave the page on the LRU so it is swappable. 544 */ 545 if (PagePrivate(page)) { 546 if (!try_to_release_page(page, sc->gfp_mask)) 547 goto activate_locked; 548 if (!mapping && page_count(page) == 1) 549 goto free_it; 550 } 551 552 if (!mapping || !remove_mapping(mapping, page)) 553 goto keep_locked; 554 555free_it: 556 unlock_page(page); 557 nr_reclaimed++; 558 if (!pagevec_add(&freed_pvec, page)) 559 __pagevec_release_nonlru(&freed_pvec); 560 continue; 561 562activate_locked: 563 SetPageActive(page); 564 pgactivate++; 565keep_locked: 566 unlock_page(page); 567keep: 568 list_add(&page->lru, &ret_pages); 569 VM_BUG_ON(PageLRU(page)); 570 } 571 list_splice(&ret_pages, page_list); 572 if (pagevec_count(&freed_pvec)) 573 __pagevec_release_nonlru(&freed_pvec); 574 count_vm_events(PGACTIVATE, pgactivate); 575 return nr_reclaimed; 576} 577 578/* 579 * zone->lru_lock is heavily contended. Some of the functions that 580 * shrink the lists perform better by taking out a batch of pages 581 * and working on them outside the LRU lock. 582 * 583 * For pagecache intensive workloads, this function is the hottest 584 * spot in the kernel (apart from copy_*_user functions). 585 * 586 * Appropriate locks must be held before calling this function. 587 * 588 * @nr_to_scan: The number of pages to look through on the list. 589 * @src: The LRU list to pull pages off. 590 * @dst: The temp list to put pages on to. 591 * @scanned: The number of pages that were scanned. 592 * 593 * returns how many pages were moved onto *@dst. 594 */ 595static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 596 struct list_head *src, struct list_head *dst, 597 unsigned long *scanned) 598{ 599 unsigned long nr_taken = 0; 600 struct page *page; 601 unsigned long scan; 602 603 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 604 struct list_head *target; 605 page = lru_to_page(src); 606 prefetchw_prev_lru_page(page, src, flags); 607 608 VM_BUG_ON(!PageLRU(page)); 609 610 list_del(&page->lru); 611 target = src; 612 if (likely(get_page_unless_zero(page))) { 613 /* 614 * Be careful not to clear PageLRU until after we're 615 * sure the page is not being freed elsewhere -- the 616 * page release code relies on it. 617 */ 618 ClearPageLRU(page); 619 target = dst; 620 nr_taken++; 621 } /* else it is being freed elsewhere */ 622 623 list_add(&page->lru, target); 624 } 625 626 *scanned = scan; 627 return nr_taken; 628} 629 630/* 631 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 632 * of reclaimed pages 633 */ 634static unsigned long shrink_inactive_list(unsigned long max_scan, 635 struct zone *zone, struct scan_control *sc) 636{ 637 LIST_HEAD(page_list); 638 struct pagevec pvec; 639 unsigned long nr_scanned = 0; 640 unsigned long nr_reclaimed = 0; 641 642 pagevec_init(&pvec, 1); 643 644 lru_add_drain(); 645 spin_lock_irq(&zone->lru_lock); 646 do { 647 struct page *page; 648 unsigned long nr_taken; 649 unsigned long nr_scan; 650 unsigned long nr_freed; 651 652 nr_taken = isolate_lru_pages(sc->swap_cluster_max, 653 &zone->inactive_list, 654 &page_list, &nr_scan); 655 zone->nr_inactive -= nr_taken; 656 zone->pages_scanned += nr_scan; 657 spin_unlock_irq(&zone->lru_lock); 658 659 nr_scanned += nr_scan; 660 nr_freed = shrink_page_list(&page_list, sc); 661 nr_reclaimed += nr_freed; 662 local_irq_disable(); 663 if (current_is_kswapd()) { 664 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan); 665 __count_vm_events(KSWAPD_STEAL, nr_freed); 666 } else 667 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan); 668 __count_vm_events(PGACTIVATE, nr_freed); 669 670 if (nr_taken == 0) 671 goto done; 672 673 spin_lock(&zone->lru_lock); 674 /* 675 * Put back any unfreeable pages. 676 */ 677 while (!list_empty(&page_list)) { 678 page = lru_to_page(&page_list); 679 VM_BUG_ON(PageLRU(page)); 680 SetPageLRU(page); 681 list_del(&page->lru); 682 if (PageActive(page)) 683 add_page_to_active_list(zone, page); 684 else 685 add_page_to_inactive_list(zone, page); 686 if (!pagevec_add(&pvec, page)) { 687 spin_unlock_irq(&zone->lru_lock); 688 __pagevec_release(&pvec); 689 spin_lock_irq(&zone->lru_lock); 690 } 691 } 692 } while (nr_scanned < max_scan); 693 spin_unlock(&zone->lru_lock); 694done: 695 local_irq_enable(); 696 pagevec_release(&pvec); 697 return nr_reclaimed; 698} 699 700static inline int zone_is_near_oom(struct zone *zone) 701{ 702 return zone->pages_scanned >= (zone->nr_active + zone->nr_inactive)*3; 703} 704 705/* 706 * This moves pages from the active list to the inactive list. 707 * 708 * We move them the other way if the page is referenced by one or more 709 * processes, from rmap. 710 * 711 * If the pages are mostly unmapped, the processing is fast and it is 712 * appropriate to hold zone->lru_lock across the whole operation. But if 713 * the pages are mapped, the processing is slow (page_referenced()) so we 714 * should drop zone->lru_lock around each page. It's impossible to balance 715 * this, so instead we remove the pages from the LRU while processing them. 716 * It is safe to rely on PG_active against the non-LRU pages in here because 717 * nobody will play with that bit on a non-LRU page. 718 * 719 * The downside is that we have to touch page->_count against each page. 720 * But we had to alter page->flags anyway. 721 */ 722static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 723 struct scan_control *sc) 724{ 725 unsigned long pgmoved; 726 int pgdeactivate = 0; 727 unsigned long pgscanned; 728 LIST_HEAD(l_hold); /* The pages which were snipped off */ 729 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ 730 LIST_HEAD(l_active); /* Pages to go onto the active_list */ 731 struct page *page; 732 struct pagevec pvec; 733 int reclaim_mapped = 0; 734 735 if (sc->may_swap) { 736 long mapped_ratio; 737 long distress; 738 long swap_tendency; 739 740 if (zone_is_near_oom(zone)) 741 goto force_reclaim_mapped; 742 743 /* 744 * `distress' is a measure of how much trouble we're having 745 * reclaiming pages. 0 -> no problems. 100 -> great trouble. 746 */ 747 distress = 100 >> zone->prev_priority; 748 749 /* 750 * The point of this algorithm is to decide when to start 751 * reclaiming mapped memory instead of just pagecache. Work out 752 * how much memory 753 * is mapped. 754 */ 755 mapped_ratio = ((global_page_state(NR_FILE_MAPPED) + 756 global_page_state(NR_ANON_PAGES)) * 100) / 757 vm_total_pages; 758 759 /* 760 * Now decide how much we really want to unmap some pages. The 761 * mapped ratio is downgraded - just because there's a lot of 762 * mapped memory doesn't necessarily mean that page reclaim 763 * isn't succeeding. 764 * 765 * The distress ratio is important - we don't want to start 766 * going oom. 767 * 768 * A 100% value of vm_swappiness overrides this algorithm 769 * altogether. 770 */ 771 swap_tendency = mapped_ratio / 2 + distress + sc->swappiness; 772 773 /* 774 * Now use this metric to decide whether to start moving mapped 775 * memory onto the inactive list. 776 */ 777 if (swap_tendency >= 100) 778force_reclaim_mapped: 779 reclaim_mapped = 1; 780 } 781 782 lru_add_drain(); 783 spin_lock_irq(&zone->lru_lock); 784 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, 785 &l_hold, &pgscanned); 786 zone->pages_scanned += pgscanned; 787 zone->nr_active -= pgmoved; 788 spin_unlock_irq(&zone->lru_lock); 789 790 while (!list_empty(&l_hold)) { 791 cond_resched(); 792 page = lru_to_page(&l_hold); 793 list_del(&page->lru); 794 if (page_mapped(page)) { 795 if (!reclaim_mapped || 796 (total_swap_pages == 0 && PageAnon(page)) || 797 page_referenced(page, 0)) { 798 list_add(&page->lru, &l_active); 799 continue; 800 } 801 } 802 list_add(&page->lru, &l_inactive); 803 } 804 805 pagevec_init(&pvec, 1); 806 pgmoved = 0; 807 spin_lock_irq(&zone->lru_lock); 808 while (!list_empty(&l_inactive)) { 809 page = lru_to_page(&l_inactive); 810 prefetchw_prev_lru_page(page, &l_inactive, flags); 811 VM_BUG_ON(PageLRU(page)); 812 SetPageLRU(page); 813 VM_BUG_ON(!PageActive(page)); 814 ClearPageActive(page); 815 816 list_move(&page->lru, &zone->inactive_list); 817 pgmoved++; 818 if (!pagevec_add(&pvec, page)) { 819 zone->nr_inactive += pgmoved; 820 spin_unlock_irq(&zone->lru_lock); 821 pgdeactivate += pgmoved; 822 pgmoved = 0; 823 if (buffer_heads_over_limit) 824 pagevec_strip(&pvec); 825 __pagevec_release(&pvec); 826 spin_lock_irq(&zone->lru_lock); 827 } 828 } 829 zone->nr_inactive += pgmoved; 830 pgdeactivate += pgmoved; 831 if (buffer_heads_over_limit) { 832 spin_unlock_irq(&zone->lru_lock); 833 pagevec_strip(&pvec); 834 spin_lock_irq(&zone->lru_lock); 835 } 836 837 pgmoved = 0; 838 while (!list_empty(&l_active)) { 839 page = lru_to_page(&l_active); 840 prefetchw_prev_lru_page(page, &l_active, flags); 841 VM_BUG_ON(PageLRU(page)); 842 SetPageLRU(page); 843 VM_BUG_ON(!PageActive(page)); 844 list_move(&page->lru, &zone->active_list); 845 pgmoved++; 846 if (!pagevec_add(&pvec, page)) { 847 zone->nr_active += pgmoved; 848 pgmoved = 0; 849 spin_unlock_irq(&zone->lru_lock); 850 __pagevec_release(&pvec); 851 spin_lock_irq(&zone->lru_lock); 852 } 853 } 854 zone->nr_active += pgmoved; 855 856 __count_zone_vm_events(PGREFILL, zone, pgscanned); 857 __count_vm_events(PGDEACTIVATE, pgdeactivate); 858 spin_unlock_irq(&zone->lru_lock); 859 860 pagevec_release(&pvec); 861} 862 863/* 864 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 865 */ 866static unsigned long shrink_zone(int priority, struct zone *zone, 867 struct scan_control *sc) 868{ 869 unsigned long nr_active; 870 unsigned long nr_inactive; 871 unsigned long nr_to_scan; 872 unsigned long nr_reclaimed = 0; 873 874 atomic_inc(&zone->reclaim_in_progress); 875 876 /* 877 * Add one to `nr_to_scan' just to make sure that the kernel will 878 * slowly sift through the active list. 879 */ 880 zone->nr_scan_active += (zone->nr_active >> priority) + 1; 881 nr_active = zone->nr_scan_active; 882 if (nr_active >= sc->swap_cluster_max) 883 zone->nr_scan_active = 0; 884 else 885 nr_active = 0; 886 887 zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1; 888 nr_inactive = zone->nr_scan_inactive; 889 if (nr_inactive >= sc->swap_cluster_max) 890 zone->nr_scan_inactive = 0; 891 else 892 nr_inactive = 0; 893 894 while (nr_active || nr_inactive) { 895 if (nr_active) { 896 nr_to_scan = min(nr_active, 897 (unsigned long)sc->swap_cluster_max); 898 nr_active -= nr_to_scan; 899 shrink_active_list(nr_to_scan, zone, sc); 900 } 901 902 if (nr_inactive) { 903 nr_to_scan = min(nr_inactive, 904 (unsigned long)sc->swap_cluster_max); 905 nr_inactive -= nr_to_scan; 906 nr_reclaimed += shrink_inactive_list(nr_to_scan, zone, 907 sc); 908 } 909 } 910 911 throttle_vm_writeout(); 912 913 atomic_dec(&zone->reclaim_in_progress); 914 return nr_reclaimed; 915} 916 917/* 918 * This is the direct reclaim path, for page-allocating processes. We only 919 * try to reclaim pages from zones which will satisfy the caller's allocation 920 * request. 921 * 922 * We reclaim from a zone even if that zone is over pages_high. Because: 923 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 924 * allocation or 925 * b) The zones may be over pages_high but they must go *over* pages_high to 926 * satisfy the `incremental min' zone defense algorithm. 927 * 928 * Returns the number of reclaimed pages. 929 * 930 * If a zone is deemed to be full of pinned pages then just give it a light 931 * scan then give up on it. 932 */ 933static unsigned long shrink_zones(int priority, struct zone **zones, 934 struct scan_control *sc) 935{ 936 unsigned long nr_reclaimed = 0; 937 int i; 938 939 sc->all_unreclaimable = 1; 940 for (i = 0; zones[i] != NULL; i++) { 941 struct zone *zone = zones[i]; 942 943 if (!populated_zone(zone)) 944 continue; 945 946 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 947 continue; 948 949 zone->temp_priority = priority; 950 if (zone->prev_priority > priority) 951 zone->prev_priority = priority; 952 953 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 954 continue; /* Let kswapd poll it */ 955 956 sc->all_unreclaimable = 0; 957 958 nr_reclaimed += shrink_zone(priority, zone, sc); 959 } 960 return nr_reclaimed; 961} 962 963/* 964 * This is the main entry point to direct page reclaim. 965 * 966 * If a full scan of the inactive list fails to free enough memory then we 967 * are "out of memory" and something needs to be killed. 968 * 969 * If the caller is !__GFP_FS then the probability of a failure is reasonably 970 * high - the zone may be full of dirty or under-writeback pages, which this 971 * caller can't do much about. We kick pdflush and take explicit naps in the 972 * hope that some of these pages can be written. But if the allocating task 973 * holds filesystem locks which prevent writeout this might not work, and the 974 * allocation attempt will fail. 975 */ 976unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask) 977{ 978 int priority; 979 int ret = 0; 980 unsigned long total_scanned = 0; 981 unsigned long nr_reclaimed = 0; 982 struct reclaim_state *reclaim_state = current->reclaim_state; 983 unsigned long lru_pages = 0; 984 int i; 985 struct scan_control sc = { 986 .gfp_mask = gfp_mask, 987 .may_writepage = !laptop_mode, 988 .swap_cluster_max = SWAP_CLUSTER_MAX, 989 .may_swap = 1, 990 .swappiness = vm_swappiness, 991 }; 992 993 count_vm_event(ALLOCSTALL); 994 995 for (i = 0; zones[i] != NULL; i++) { 996 struct zone *zone = zones[i]; 997 998 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 999 continue; 1000 1001 zone->temp_priority = DEF_PRIORITY; 1002 lru_pages += zone->nr_active + zone->nr_inactive; 1003 } 1004 1005 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1006 sc.nr_scanned = 0; 1007 if (!priority) 1008 disable_swap_token(); 1009 nr_reclaimed += shrink_zones(priority, zones, &sc); 1010 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); 1011 if (reclaim_state) { 1012 nr_reclaimed += reclaim_state->reclaimed_slab; 1013 reclaim_state->reclaimed_slab = 0; 1014 } 1015 total_scanned += sc.nr_scanned; 1016 if (nr_reclaimed >= sc.swap_cluster_max) { 1017 ret = 1; 1018 goto out; 1019 } 1020 1021 /* 1022 * Try to write back as many pages as we just scanned. This 1023 * tends to cause slow streaming writers to write data to the 1024 * disk smoothly, at the dirtying rate, which is nice. But 1025 * that's undesirable in laptop mode, where we *want* lumpy 1026 * writeout. So in laptop mode, write out the whole world. 1027 */ 1028 if (total_scanned > sc.swap_cluster_max + 1029 sc.swap_cluster_max / 2) { 1030 wakeup_pdflush(laptop_mode ? 0 : total_scanned); 1031 sc.may_writepage = 1; 1032 } 1033 1034 /* Take a nap, wait for some writeback to complete */ 1035 if (sc.nr_scanned && priority < DEF_PRIORITY - 2) 1036 blk_congestion_wait(WRITE, HZ/10); 1037 } 1038 /* top priority shrink_caches still had more to do? don't OOM, then */ 1039 if (!sc.all_unreclaimable) 1040 ret = 1; 1041out: 1042 for (i = 0; zones[i] != 0; i++) { 1043 struct zone *zone = zones[i]; 1044 1045 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 1046 continue; 1047 1048 zone->prev_priority = zone->temp_priority; 1049 } 1050 return ret; 1051} 1052 1053/* 1054 * For kswapd, balance_pgdat() will work across all this node's zones until 1055 * they are all at pages_high. 1056 * 1057 * Returns the number of pages which were actually freed. 1058 * 1059 * There is special handling here for zones which are full of pinned pages. 1060 * This can happen if the pages are all mlocked, or if they are all used by 1061 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 1062 * What we do is to detect the case where all pages in the zone have been 1063 * scanned twice and there has been zero successful reclaim. Mark the zone as 1064 * dead and from now on, only perform a short scan. Basically we're polling 1065 * the zone for when the problem goes away. 1066 * 1067 * kswapd scans the zones in the highmem->normal->dma direction. It skips 1068 * zones which have free_pages > pages_high, but once a zone is found to have 1069 * free_pages <= pages_high, we scan that zone and the lower zones regardless 1070 * of the number of free pages in the lower zones. This interoperates with 1071 * the page allocator fallback scheme to ensure that aging of pages is balanced 1072 * across the zones. 1073 */ 1074static unsigned long balance_pgdat(pg_data_t *pgdat, int order) 1075{ 1076 int all_zones_ok; 1077 int priority; 1078 int i; 1079 unsigned long total_scanned; 1080 unsigned long nr_reclaimed; 1081 struct reclaim_state *reclaim_state = current->reclaim_state; 1082 struct scan_control sc = { 1083 .gfp_mask = GFP_KERNEL, 1084 .may_swap = 1, 1085 .swap_cluster_max = SWAP_CLUSTER_MAX, 1086 .swappiness = vm_swappiness, 1087 }; 1088 1089loop_again: 1090 total_scanned = 0; 1091 nr_reclaimed = 0; 1092 sc.may_writepage = !laptop_mode; 1093 count_vm_event(PAGEOUTRUN); 1094 1095 for (i = 0; i < pgdat->nr_zones; i++) { 1096 struct zone *zone = pgdat->node_zones + i; 1097 1098 zone->temp_priority = DEF_PRIORITY; 1099 } 1100 1101 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1102 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 1103 unsigned long lru_pages = 0; 1104 1105 /* The swap token gets in the way of swapout... */ 1106 if (!priority) 1107 disable_swap_token(); 1108 1109 all_zones_ok = 1; 1110 1111 /* 1112 * Scan in the highmem->dma direction for the highest 1113 * zone which needs scanning 1114 */ 1115 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 1116 struct zone *zone = pgdat->node_zones + i; 1117 1118 if (!populated_zone(zone)) 1119 continue; 1120 1121 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1122 continue; 1123 1124 if (!zone_watermark_ok(zone, order, zone->pages_high, 1125 0, 0)) { 1126 end_zone = i; 1127 goto scan; 1128 } 1129 } 1130 goto out; 1131scan: 1132 for (i = 0; i <= end_zone; i++) { 1133 struct zone *zone = pgdat->node_zones + i; 1134 1135 lru_pages += zone->nr_active + zone->nr_inactive; 1136 } 1137 1138 /* 1139 * Now scan the zone in the dma->highmem direction, stopping 1140 * at the last zone which needs scanning. 1141 * 1142 * We do this because the page allocator works in the opposite 1143 * direction. This prevents the page allocator from allocating 1144 * pages behind kswapd's direction of progress, which would 1145 * cause too much scanning of the lower zones. 1146 */ 1147 for (i = 0; i <= end_zone; i++) { 1148 struct zone *zone = pgdat->node_zones + i; 1149 int nr_slab; 1150 1151 if (!populated_zone(zone)) 1152 continue; 1153 1154 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1155 continue; 1156 1157 if (!zone_watermark_ok(zone, order, zone->pages_high, 1158 end_zone, 0)) 1159 all_zones_ok = 0; 1160 zone->temp_priority = priority; 1161 if (zone->prev_priority > priority) 1162 zone->prev_priority = priority; 1163 sc.nr_scanned = 0; 1164 nr_reclaimed += shrink_zone(priority, zone, &sc); 1165 reclaim_state->reclaimed_slab = 0; 1166 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 1167 lru_pages); 1168 nr_reclaimed += reclaim_state->reclaimed_slab; 1169 total_scanned += sc.nr_scanned; 1170 if (zone->all_unreclaimable) 1171 continue; 1172 if (nr_slab == 0 && zone->pages_scanned >= 1173 (zone->nr_active + zone->nr_inactive) * 6) 1174 zone->all_unreclaimable = 1; 1175 /* 1176 * If we've done a decent amount of scanning and 1177 * the reclaim ratio is low, start doing writepage 1178 * even in laptop mode 1179 */ 1180 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 1181 total_scanned > nr_reclaimed + nr_reclaimed / 2) 1182 sc.may_writepage = 1; 1183 } 1184 if (all_zones_ok) 1185 break; /* kswapd: all done */ 1186 /* 1187 * OK, kswapd is getting into trouble. Take a nap, then take 1188 * another pass across the zones. 1189 */ 1190 if (total_scanned && priority < DEF_PRIORITY - 2) 1191 blk_congestion_wait(WRITE, HZ/10); 1192 1193 /* 1194 * We do this so kswapd doesn't build up large priorities for 1195 * example when it is freeing in parallel with allocators. It 1196 * matches the direct reclaim path behaviour in terms of impact 1197 * on zone->*_priority. 1198 */ 1199 if (nr_reclaimed >= SWAP_CLUSTER_MAX) 1200 break; 1201 } 1202out: 1203 for (i = 0; i < pgdat->nr_zones; i++) { 1204 struct zone *zone = pgdat->node_zones + i; 1205 1206 zone->prev_priority = zone->temp_priority; 1207 } 1208 if (!all_zones_ok) { 1209 cond_resched(); 1210 goto loop_again; 1211 } 1212 1213 return nr_reclaimed; 1214} 1215 1216/* 1217 * The background pageout daemon, started as a kernel thread 1218 * from the init process. 1219 * 1220 * This basically trickles out pages so that we have _some_ 1221 * free memory available even if there is no other activity 1222 * that frees anything up. This is needed for things like routing 1223 * etc, where we otherwise might have all activity going on in 1224 * asynchronous contexts that cannot page things out. 1225 * 1226 * If there are applications that are active memory-allocators 1227 * (most normal use), this basically shouldn't matter. 1228 */ 1229static int kswapd(void *p) 1230{ 1231 unsigned long order; 1232 pg_data_t *pgdat = (pg_data_t*)p; 1233 struct task_struct *tsk = current; 1234 DEFINE_WAIT(wait); 1235 struct reclaim_state reclaim_state = { 1236 .reclaimed_slab = 0, 1237 }; 1238 cpumask_t cpumask; 1239 1240 cpumask = node_to_cpumask(pgdat->node_id); 1241 if (!cpus_empty(cpumask)) 1242 set_cpus_allowed(tsk, cpumask); 1243 current->reclaim_state = &reclaim_state; 1244 1245 /* 1246 * Tell the memory management that we're a "memory allocator", 1247 * and that if we need more memory we should get access to it 1248 * regardless (see "__alloc_pages()"). "kswapd" should 1249 * never get caught in the normal page freeing logic. 1250 * 1251 * (Kswapd normally doesn't need memory anyway, but sometimes 1252 * you need a small amount of memory in order to be able to 1253 * page out something else, and this flag essentially protects 1254 * us from recursively trying to free more memory as we're 1255 * trying to free the first piece of memory in the first place). 1256 */ 1257 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 1258 1259 order = 0; 1260 for ( ; ; ) { 1261 unsigned long new_order; 1262 1263 try_to_freeze(); 1264 1265 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 1266 new_order = pgdat->kswapd_max_order; 1267 pgdat->kswapd_max_order = 0; 1268 if (order < new_order) { 1269 /* 1270 * Don't sleep if someone wants a larger 'order' 1271 * allocation 1272 */ 1273 order = new_order; 1274 } else { 1275 schedule(); 1276 order = pgdat->kswapd_max_order; 1277 } 1278 finish_wait(&pgdat->kswapd_wait, &wait); 1279 1280 balance_pgdat(pgdat, order); 1281 } 1282 return 0; 1283} 1284 1285/* 1286 * A zone is low on free memory, so wake its kswapd task to service it. 1287 */ 1288void wakeup_kswapd(struct zone *zone, int order) 1289{ 1290 pg_data_t *pgdat; 1291 1292 if (!populated_zone(zone)) 1293 return; 1294 1295 pgdat = zone->zone_pgdat; 1296 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) 1297 return; 1298 if (pgdat->kswapd_max_order < order) 1299 pgdat->kswapd_max_order = order; 1300 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 1301 return; 1302 if (!waitqueue_active(&pgdat->kswapd_wait)) 1303 return; 1304 wake_up_interruptible(&pgdat->kswapd_wait); 1305} 1306 1307#ifdef CONFIG_PM 1308/* 1309 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages 1310 * from LRU lists system-wide, for given pass and priority, and returns the 1311 * number of reclaimed pages 1312 * 1313 * For pass > 3 we also try to shrink the LRU lists that contain a few pages 1314 */ 1315static unsigned long shrink_all_zones(unsigned long nr_pages, int pass, 1316 int prio, struct scan_control *sc) 1317{ 1318 struct zone *zone; 1319 unsigned long nr_to_scan, ret = 0; 1320 1321 for_each_zone(zone) { 1322 1323 if (!populated_zone(zone)) 1324 continue; 1325 1326 if (zone->all_unreclaimable && prio != DEF_PRIORITY) 1327 continue; 1328 1329 /* For pass = 0 we don't shrink the active list */ 1330 if (pass > 0) { 1331 zone->nr_scan_active += (zone->nr_active >> prio) + 1; 1332 if (zone->nr_scan_active >= nr_pages || pass > 3) { 1333 zone->nr_scan_active = 0; 1334 nr_to_scan = min(nr_pages, zone->nr_active); 1335 shrink_active_list(nr_to_scan, zone, sc); 1336 } 1337 } 1338 1339 zone->nr_scan_inactive += (zone->nr_inactive >> prio) + 1; 1340 if (zone->nr_scan_inactive >= nr_pages || pass > 3) { 1341 zone->nr_scan_inactive = 0; 1342 nr_to_scan = min(nr_pages, zone->nr_inactive); 1343 ret += shrink_inactive_list(nr_to_scan, zone, sc); 1344 if (ret >= nr_pages) 1345 return ret; 1346 } 1347 } 1348 1349 return ret; 1350} 1351 1352/* 1353 * Try to free `nr_pages' of memory, system-wide, and return the number of 1354 * freed pages. 1355 * 1356 * Rather than trying to age LRUs the aim is to preserve the overall 1357 * LRU order by reclaiming preferentially 1358 * inactive > active > active referenced > active mapped 1359 */ 1360unsigned long shrink_all_memory(unsigned long nr_pages) 1361{ 1362 unsigned long lru_pages, nr_slab; 1363 unsigned long ret = 0; 1364 int pass; 1365 struct reclaim_state reclaim_state; 1366 struct zone *zone; 1367 struct scan_control sc = { 1368 .gfp_mask = GFP_KERNEL, 1369 .may_swap = 0, 1370 .swap_cluster_max = nr_pages, 1371 .may_writepage = 1, 1372 .swappiness = vm_swappiness, 1373 }; 1374 1375 current->reclaim_state = &reclaim_state; 1376 1377 lru_pages = 0; 1378 for_each_zone(zone) 1379 lru_pages += zone->nr_active + zone->nr_inactive; 1380 1381 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE); 1382 /* If slab caches are huge, it's better to hit them first */ 1383 while (nr_slab >= lru_pages) { 1384 reclaim_state.reclaimed_slab = 0; 1385 shrink_slab(nr_pages, sc.gfp_mask, lru_pages); 1386 if (!reclaim_state.reclaimed_slab) 1387 break; 1388 1389 ret += reclaim_state.reclaimed_slab; 1390 if (ret >= nr_pages) 1391 goto out; 1392 1393 nr_slab -= reclaim_state.reclaimed_slab; 1394 } 1395 1396 /* 1397 * We try to shrink LRUs in 5 passes: 1398 * 0 = Reclaim from inactive_list only 1399 * 1 = Reclaim from active list but don't reclaim mapped 1400 * 2 = 2nd pass of type 1 1401 * 3 = Reclaim mapped (normal reclaim) 1402 * 4 = 2nd pass of type 3 1403 */ 1404 for (pass = 0; pass < 5; pass++) { 1405 int prio; 1406 1407 /* Needed for shrinking slab caches later on */ 1408 if (!lru_pages) 1409 for_each_zone(zone) { 1410 lru_pages += zone->nr_active; 1411 lru_pages += zone->nr_inactive; 1412 } 1413 1414 /* Force reclaiming mapped pages in the passes #3 and #4 */ 1415 if (pass > 2) { 1416 sc.may_swap = 1; 1417 sc.swappiness = 100; 1418 } 1419 1420 for (prio = DEF_PRIORITY; prio >= 0; prio--) { 1421 unsigned long nr_to_scan = nr_pages - ret; 1422 1423 sc.nr_scanned = 0; 1424 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc); 1425 if (ret >= nr_pages) 1426 goto out; 1427 1428 reclaim_state.reclaimed_slab = 0; 1429 shrink_slab(sc.nr_scanned, sc.gfp_mask, lru_pages); 1430 ret += reclaim_state.reclaimed_slab; 1431 if (ret >= nr_pages) 1432 goto out; 1433 1434 if (sc.nr_scanned && prio < DEF_PRIORITY - 2) 1435 blk_congestion_wait(WRITE, HZ / 10); 1436 } 1437 1438 lru_pages = 0; 1439 } 1440 1441 /* 1442 * If ret = 0, we could not shrink LRUs, but there may be something 1443 * in slab caches 1444 */ 1445 if (!ret) 1446 do { 1447 reclaim_state.reclaimed_slab = 0; 1448 shrink_slab(nr_pages, sc.gfp_mask, lru_pages); 1449 ret += reclaim_state.reclaimed_slab; 1450 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0); 1451 1452out: 1453 current->reclaim_state = NULL; 1454 1455 return ret; 1456} 1457#endif 1458 1459#ifdef CONFIG_HOTPLUG_CPU 1460/* It's optimal to keep kswapds on the same CPUs as their memory, but 1461 not required for correctness. So if the last cpu in a node goes 1462 away, we get changed to run anywhere: as the first one comes back, 1463 restore their cpu bindings. */ 1464static int __devinit cpu_callback(struct notifier_block *nfb, 1465 unsigned long action, void *hcpu) 1466{ 1467 pg_data_t *pgdat; 1468 cpumask_t mask; 1469 1470 if (action == CPU_ONLINE) { 1471 for_each_online_pgdat(pgdat) { 1472 mask = node_to_cpumask(pgdat->node_id); 1473 if (any_online_cpu(mask) != NR_CPUS) 1474 /* One of our CPUs online: restore mask */ 1475 set_cpus_allowed(pgdat->kswapd, mask); 1476 } 1477 } 1478 return NOTIFY_OK; 1479} 1480#endif /* CONFIG_HOTPLUG_CPU */ 1481 1482/* 1483 * This kswapd start function will be called by init and node-hot-add. 1484 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 1485 */ 1486int kswapd_run(int nid) 1487{ 1488 pg_data_t *pgdat = NODE_DATA(nid); 1489 int ret = 0; 1490 1491 if (pgdat->kswapd) 1492 return 0; 1493 1494 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 1495 if (IS_ERR(pgdat->kswapd)) { 1496 /* failure at boot is fatal */ 1497 BUG_ON(system_state == SYSTEM_BOOTING); 1498 printk("Failed to start kswapd on node %d\n",nid); 1499 ret = -1; 1500 } 1501 return ret; 1502} 1503 1504static int __init kswapd_init(void) 1505{ 1506 int nid; 1507 1508 swap_setup(); 1509 for_each_online_node(nid) 1510 kswapd_run(nid); 1511 hotcpu_notifier(cpu_callback, 0); 1512 return 0; 1513} 1514 1515module_init(kswapd_init) 1516 1517#ifdef CONFIG_NUMA 1518/* 1519 * Zone reclaim mode 1520 * 1521 * If non-zero call zone_reclaim when the number of free pages falls below 1522 * the watermarks. 1523 */ 1524int zone_reclaim_mode __read_mostly; 1525 1526#define RECLAIM_OFF 0 1527#define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */ 1528#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 1529#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 1530 1531/* 1532 * Priority for ZONE_RECLAIM. This determines the fraction of pages 1533 * of a node considered for each zone_reclaim. 4 scans 1/16th of 1534 * a zone. 1535 */ 1536#define ZONE_RECLAIM_PRIORITY 4 1537 1538/* 1539 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 1540 * occur. 1541 */ 1542int sysctl_min_unmapped_ratio = 1; 1543 1544/* 1545 * If the number of slab pages in a zone grows beyond this percentage then 1546 * slab reclaim needs to occur. 1547 */ 1548int sysctl_min_slab_ratio = 5; 1549 1550/* 1551 * Try to free up some pages from this zone through reclaim. 1552 */ 1553static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 1554{ 1555 /* Minimum pages needed in order to stay on node */ 1556 const unsigned long nr_pages = 1 << order; 1557 struct task_struct *p = current; 1558 struct reclaim_state reclaim_state; 1559 int priority; 1560 unsigned long nr_reclaimed = 0; 1561 struct scan_control sc = { 1562 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 1563 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP), 1564 .swap_cluster_max = max_t(unsigned long, nr_pages, 1565 SWAP_CLUSTER_MAX), 1566 .gfp_mask = gfp_mask, 1567 .swappiness = vm_swappiness, 1568 }; 1569 unsigned long slab_reclaimable; 1570 1571 disable_swap_token(); 1572 cond_resched(); 1573 /* 1574 * We need to be able to allocate from the reserves for RECLAIM_SWAP 1575 * and we also need to be able to write out pages for RECLAIM_WRITE 1576 * and RECLAIM_SWAP. 1577 */ 1578 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 1579 reclaim_state.reclaimed_slab = 0; 1580 p->reclaim_state = &reclaim_state; 1581 1582 if (zone_page_state(zone, NR_FILE_PAGES) - 1583 zone_page_state(zone, NR_FILE_MAPPED) > 1584 zone->min_unmapped_pages) { 1585 /* 1586 * Free memory by calling shrink zone with increasing 1587 * priorities until we have enough memory freed. 1588 */ 1589 priority = ZONE_RECLAIM_PRIORITY; 1590 do { 1591 nr_reclaimed += shrink_zone(priority, zone, &sc); 1592 priority--; 1593 } while (priority >= 0 && nr_reclaimed < nr_pages); 1594 } 1595 1596 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 1597 if (slab_reclaimable > zone->min_slab_pages) { 1598 /* 1599 * shrink_slab() does not currently allow us to determine how 1600 * many pages were freed in this zone. So we take the current 1601 * number of slab pages and shake the slab until it is reduced 1602 * by the same nr_pages that we used for reclaiming unmapped 1603 * pages. 1604 * 1605 * Note that shrink_slab will free memory on all zones and may 1606 * take a long time. 1607 */ 1608 while (shrink_slab(sc.nr_scanned, gfp_mask, order) && 1609 zone_page_state(zone, NR_SLAB_RECLAIMABLE) > 1610 slab_reclaimable - nr_pages) 1611 ; 1612 1613 /* 1614 * Update nr_reclaimed by the number of slab pages we 1615 * reclaimed from this zone. 1616 */ 1617 nr_reclaimed += slab_reclaimable - 1618 zone_page_state(zone, NR_SLAB_RECLAIMABLE); 1619 } 1620 1621 p->reclaim_state = NULL; 1622 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 1623 return nr_reclaimed >= nr_pages; 1624} 1625 1626int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 1627{ 1628 cpumask_t mask; 1629 int node_id; 1630 1631 /* 1632 * Zone reclaim reclaims unmapped file backed pages and 1633 * slab pages if we are over the defined limits. 1634 * 1635 * A small portion of unmapped file backed pages is needed for 1636 * file I/O otherwise pages read by file I/O will be immediately 1637 * thrown out if the zone is overallocated. So we do not reclaim 1638 * if less than a specified percentage of the zone is used by 1639 * unmapped file backed pages. 1640 */ 1641 if (zone_page_state(zone, NR_FILE_PAGES) - 1642 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages 1643 && zone_page_state(zone, NR_SLAB_RECLAIMABLE) 1644 <= zone->min_slab_pages) 1645 return 0; 1646 1647 /* 1648 * Avoid concurrent zone reclaims, do not reclaim in a zone that does 1649 * not have reclaimable pages and if we should not delay the allocation 1650 * then do not scan. 1651 */ 1652 if (!(gfp_mask & __GFP_WAIT) || 1653 zone->all_unreclaimable || 1654 atomic_read(&zone->reclaim_in_progress) > 0 || 1655 (current->flags & PF_MEMALLOC)) 1656 return 0; 1657 1658 /* 1659 * Only run zone reclaim on the local zone or on zones that do not 1660 * have associated processors. This will favor the local processor 1661 * over remote processors and spread off node memory allocations 1662 * as wide as possible. 1663 */ 1664 node_id = zone->zone_pgdat->node_id; 1665 mask = node_to_cpumask(node_id); 1666 if (!cpus_empty(mask) && node_id != numa_node_id()) 1667 return 0; 1668 return __zone_reclaim(zone, gfp_mask, order); 1669} 1670#endif 1671