vmscan.c revision 994fc28c7b1e697ac56befe4aecabf23f0689f46
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 37#include <asm/tlbflush.h> 38#include <asm/div64.h> 39 40#include <linux/swapops.h> 41 42/* possible outcome of pageout() */ 43typedef enum { 44 /* failed to write page out, page is locked */ 45 PAGE_KEEP, 46 /* move page to the active list, page is locked */ 47 PAGE_ACTIVATE, 48 /* page has been sent to the disk successfully, page is unlocked */ 49 PAGE_SUCCESS, 50 /* page is clean and locked */ 51 PAGE_CLEAN, 52} pageout_t; 53 54struct scan_control { 55 /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */ 56 unsigned long nr_to_scan; 57 58 /* Incremented by the number of inactive pages that were scanned */ 59 unsigned long nr_scanned; 60 61 /* Incremented by the number of pages reclaimed */ 62 unsigned long nr_reclaimed; 63 64 unsigned long nr_mapped; /* From page_state */ 65 66 /* How many pages shrink_cache() should reclaim */ 67 int nr_to_reclaim; 68 69 /* Ask shrink_caches, or shrink_zone to scan at this priority */ 70 unsigned int priority; 71 72 /* This context's GFP mask */ 73 gfp_t gfp_mask; 74 75 int may_writepage; 76 77 /* Can pages be swapped as part of reclaim? */ 78 int may_swap; 79 80 /* This context's SWAP_CLUSTER_MAX. If freeing memory for 81 * suspend, we effectively ignore SWAP_CLUSTER_MAX. 82 * In this context, it doesn't matter that we scan the 83 * whole list at once. */ 84 int swap_cluster_max; 85}; 86 87/* 88 * The list of shrinker callbacks used by to apply pressure to 89 * ageable caches. 90 */ 91struct shrinker { 92 shrinker_t shrinker; 93 struct list_head list; 94 int seeks; /* seeks to recreate an obj */ 95 long nr; /* objs pending delete */ 96}; 97 98#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 99 100#ifdef ARCH_HAS_PREFETCH 101#define prefetch_prev_lru_page(_page, _base, _field) \ 102 do { \ 103 if ((_page)->lru.prev != _base) { \ 104 struct page *prev; \ 105 \ 106 prev = lru_to_page(&(_page->lru)); \ 107 prefetch(&prev->_field); \ 108 } \ 109 } while (0) 110#else 111#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 112#endif 113 114#ifdef ARCH_HAS_PREFETCHW 115#define prefetchw_prev_lru_page(_page, _base, _field) \ 116 do { \ 117 if ((_page)->lru.prev != _base) { \ 118 struct page *prev; \ 119 \ 120 prev = lru_to_page(&(_page->lru)); \ 121 prefetchw(&prev->_field); \ 122 } \ 123 } while (0) 124#else 125#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 126#endif 127 128/* 129 * From 0 .. 100. Higher means more swappy. 130 */ 131int vm_swappiness = 60; 132static long total_memory; 133 134static LIST_HEAD(shrinker_list); 135static DECLARE_RWSEM(shrinker_rwsem); 136 137/* 138 * Add a shrinker callback to be called from the vm 139 */ 140struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) 141{ 142 struct shrinker *shrinker; 143 144 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); 145 if (shrinker) { 146 shrinker->shrinker = theshrinker; 147 shrinker->seeks = seeks; 148 shrinker->nr = 0; 149 down_write(&shrinker_rwsem); 150 list_add_tail(&shrinker->list, &shrinker_list); 151 up_write(&shrinker_rwsem); 152 } 153 return shrinker; 154} 155EXPORT_SYMBOL(set_shrinker); 156 157/* 158 * Remove one 159 */ 160void remove_shrinker(struct shrinker *shrinker) 161{ 162 down_write(&shrinker_rwsem); 163 list_del(&shrinker->list); 164 up_write(&shrinker_rwsem); 165 kfree(shrinker); 166} 167EXPORT_SYMBOL(remove_shrinker); 168 169#define SHRINK_BATCH 128 170/* 171 * Call the shrink functions to age shrinkable caches 172 * 173 * Here we assume it costs one seek to replace a lru page and that it also 174 * takes a seek to recreate a cache object. With this in mind we age equal 175 * percentages of the lru and ageable caches. This should balance the seeks 176 * generated by these structures. 177 * 178 * If the vm encounted mapped pages on the LRU it increase the pressure on 179 * slab to avoid swapping. 180 * 181 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 182 * 183 * `lru_pages' represents the number of on-LRU pages in all the zones which 184 * are eligible for the caller's allocation attempt. It is used for balancing 185 * slab reclaim versus page reclaim. 186 * 187 * Returns the number of slab objects which we shrunk. 188 */ 189static int shrink_slab(unsigned long scanned, gfp_t gfp_mask, 190 unsigned long lru_pages) 191{ 192 struct shrinker *shrinker; 193 int ret = 0; 194 195 if (scanned == 0) 196 scanned = SWAP_CLUSTER_MAX; 197 198 if (!down_read_trylock(&shrinker_rwsem)) 199 return 1; /* Assume we'll be able to shrink next time */ 200 201 list_for_each_entry(shrinker, &shrinker_list, list) { 202 unsigned long long delta; 203 unsigned long total_scan; 204 unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); 205 206 delta = (4 * scanned) / shrinker->seeks; 207 delta *= max_pass; 208 do_div(delta, lru_pages + 1); 209 shrinker->nr += delta; 210 if (shrinker->nr < 0) { 211 printk(KERN_ERR "%s: nr=%ld\n", 212 __FUNCTION__, shrinker->nr); 213 shrinker->nr = max_pass; 214 } 215 216 /* 217 * Avoid risking looping forever due to too large nr value: 218 * never try to free more than twice the estimate number of 219 * freeable entries. 220 */ 221 if (shrinker->nr > max_pass * 2) 222 shrinker->nr = max_pass * 2; 223 224 total_scan = shrinker->nr; 225 shrinker->nr = 0; 226 227 while (total_scan >= SHRINK_BATCH) { 228 long this_scan = SHRINK_BATCH; 229 int shrink_ret; 230 int nr_before; 231 232 nr_before = (*shrinker->shrinker)(0, gfp_mask); 233 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); 234 if (shrink_ret == -1) 235 break; 236 if (shrink_ret < nr_before) 237 ret += nr_before - shrink_ret; 238 mod_page_state(slabs_scanned, this_scan); 239 total_scan -= this_scan; 240 241 cond_resched(); 242 } 243 244 shrinker->nr += total_scan; 245 } 246 up_read(&shrinker_rwsem); 247 return ret; 248} 249 250/* Called without lock on whether page is mapped, so answer is unstable */ 251static inline int page_mapping_inuse(struct page *page) 252{ 253 struct address_space *mapping; 254 255 /* Page is in somebody's page tables. */ 256 if (page_mapped(page)) 257 return 1; 258 259 /* Be more reluctant to reclaim swapcache than pagecache */ 260 if (PageSwapCache(page)) 261 return 1; 262 263 mapping = page_mapping(page); 264 if (!mapping) 265 return 0; 266 267 /* File is mmap'd by somebody? */ 268 return mapping_mapped(mapping); 269} 270 271static inline int is_page_cache_freeable(struct page *page) 272{ 273 return page_count(page) - !!PagePrivate(page) == 2; 274} 275 276static int may_write_to_queue(struct backing_dev_info *bdi) 277{ 278 if (current_is_kswapd()) 279 return 1; 280 if (current_is_pdflush()) /* This is unlikely, but why not... */ 281 return 1; 282 if (!bdi_write_congested(bdi)) 283 return 1; 284 if (bdi == current->backing_dev_info) 285 return 1; 286 return 0; 287} 288 289/* 290 * We detected a synchronous write error writing a page out. Probably 291 * -ENOSPC. We need to propagate that into the address_space for a subsequent 292 * fsync(), msync() or close(). 293 * 294 * The tricky part is that after writepage we cannot touch the mapping: nothing 295 * prevents it from being freed up. But we have a ref on the page and once 296 * that page is locked, the mapping is pinned. 297 * 298 * We're allowed to run sleeping lock_page() here because we know the caller has 299 * __GFP_FS. 300 */ 301static void handle_write_error(struct address_space *mapping, 302 struct page *page, int error) 303{ 304 lock_page(page); 305 if (page_mapping(page) == mapping) { 306 if (error == -ENOSPC) 307 set_bit(AS_ENOSPC, &mapping->flags); 308 else 309 set_bit(AS_EIO, &mapping->flags); 310 } 311 unlock_page(page); 312} 313 314/* 315 * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). 316 */ 317static pageout_t pageout(struct page *page, struct address_space *mapping) 318{ 319 /* 320 * If the page is dirty, only perform writeback if that write 321 * will be non-blocking. To prevent this allocation from being 322 * stalled by pagecache activity. But note that there may be 323 * stalls if we need to run get_block(). We could test 324 * PagePrivate for that. 325 * 326 * If this process is currently in generic_file_write() against 327 * this page's queue, we can perform writeback even if that 328 * will block. 329 * 330 * If the page is swapcache, write it back even if that would 331 * block, for some throttling. This happens by accident, because 332 * swap_backing_dev_info is bust: it doesn't reflect the 333 * congestion state of the swapdevs. Easy to fix, if needed. 334 * See swapfile.c:page_queue_congested(). 335 */ 336 if (!is_page_cache_freeable(page)) 337 return PAGE_KEEP; 338 if (!mapping) { 339 /* 340 * Some data journaling orphaned pages can have 341 * page->mapping == NULL while being dirty with clean buffers. 342 */ 343 if (PagePrivate(page)) { 344 if (try_to_free_buffers(page)) { 345 ClearPageDirty(page); 346 printk("%s: orphaned page\n", __FUNCTION__); 347 return PAGE_CLEAN; 348 } 349 } 350 return PAGE_KEEP; 351 } 352 if (mapping->a_ops->writepage == NULL) 353 return PAGE_ACTIVATE; 354 if (!may_write_to_queue(mapping->backing_dev_info)) 355 return PAGE_KEEP; 356 357 if (clear_page_dirty_for_io(page)) { 358 int res; 359 struct writeback_control wbc = { 360 .sync_mode = WB_SYNC_NONE, 361 .nr_to_write = SWAP_CLUSTER_MAX, 362 .nonblocking = 1, 363 .for_reclaim = 1, 364 }; 365 366 SetPageReclaim(page); 367 res = mapping->a_ops->writepage(page, &wbc); 368 if (res < 0) 369 handle_write_error(mapping, page, res); 370 if (res == AOP_WRITEPAGE_ACTIVATE) { 371 ClearPageReclaim(page); 372 return PAGE_ACTIVATE; 373 } 374 if (!PageWriteback(page)) { 375 /* synchronous write or broken a_ops? */ 376 ClearPageReclaim(page); 377 } 378 379 return PAGE_SUCCESS; 380 } 381 382 return PAGE_CLEAN; 383} 384 385/* 386 * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed 387 */ 388static int shrink_list(struct list_head *page_list, struct scan_control *sc) 389{ 390 LIST_HEAD(ret_pages); 391 struct pagevec freed_pvec; 392 int pgactivate = 0; 393 int reclaimed = 0; 394 395 cond_resched(); 396 397 pagevec_init(&freed_pvec, 1); 398 while (!list_empty(page_list)) { 399 struct address_space *mapping; 400 struct page *page; 401 int may_enter_fs; 402 int referenced; 403 404 cond_resched(); 405 406 page = lru_to_page(page_list); 407 list_del(&page->lru); 408 409 if (TestSetPageLocked(page)) 410 goto keep; 411 412 BUG_ON(PageActive(page)); 413 414 sc->nr_scanned++; 415 /* Double the slab pressure for mapped and swapcache pages */ 416 if (page_mapped(page) || PageSwapCache(page)) 417 sc->nr_scanned++; 418 419 if (PageWriteback(page)) 420 goto keep_locked; 421 422 referenced = page_referenced(page, 1); 423 /* In active use or really unfreeable? Activate it. */ 424 if (referenced && page_mapping_inuse(page)) 425 goto activate_locked; 426 427#ifdef CONFIG_SWAP 428 /* 429 * Anonymous process memory has backing store? 430 * Try to allocate it some swap space here. 431 */ 432 if (PageAnon(page) && !PageSwapCache(page)) { 433 if (!sc->may_swap) 434 goto keep_locked; 435 if (!add_to_swap(page)) 436 goto activate_locked; 437 } 438#endif /* CONFIG_SWAP */ 439 440 mapping = page_mapping(page); 441 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 442 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 443 444 /* 445 * The page is mapped into the page tables of one or more 446 * processes. Try to unmap it here. 447 */ 448 if (page_mapped(page) && mapping) { 449 switch (try_to_unmap(page)) { 450 case SWAP_FAIL: 451 goto activate_locked; 452 case SWAP_AGAIN: 453 goto keep_locked; 454 case SWAP_SUCCESS: 455 ; /* try to free the page below */ 456 } 457 } 458 459 if (PageDirty(page)) { 460 if (referenced) 461 goto keep_locked; 462 if (!may_enter_fs) 463 goto keep_locked; 464 if (laptop_mode && !sc->may_writepage) 465 goto keep_locked; 466 467 /* Page is dirty, try to write it out here */ 468 switch(pageout(page, mapping)) { 469 case PAGE_KEEP: 470 goto keep_locked; 471 case PAGE_ACTIVATE: 472 goto activate_locked; 473 case PAGE_SUCCESS: 474 if (PageWriteback(page) || PageDirty(page)) 475 goto keep; 476 /* 477 * A synchronous write - probably a ramdisk. Go 478 * ahead and try to reclaim the page. 479 */ 480 if (TestSetPageLocked(page)) 481 goto keep; 482 if (PageDirty(page) || PageWriteback(page)) 483 goto keep_locked; 484 mapping = page_mapping(page); 485 case PAGE_CLEAN: 486 ; /* try to free the page below */ 487 } 488 } 489 490 /* 491 * If the page has buffers, try to free the buffer mappings 492 * associated with this page. If we succeed we try to free 493 * the page as well. 494 * 495 * We do this even if the page is PageDirty(). 496 * try_to_release_page() does not perform I/O, but it is 497 * possible for a page to have PageDirty set, but it is actually 498 * clean (all its buffers are clean). This happens if the 499 * buffers were written out directly, with submit_bh(). ext3 500 * will do this, as well as the blockdev mapping. 501 * try_to_release_page() will discover that cleanness and will 502 * drop the buffers and mark the page clean - it can be freed. 503 * 504 * Rarely, pages can have buffers and no ->mapping. These are 505 * the pages which were not successfully invalidated in 506 * truncate_complete_page(). We try to drop those buffers here 507 * and if that worked, and the page is no longer mapped into 508 * process address space (page_count == 1) it can be freed. 509 * Otherwise, leave the page on the LRU so it is swappable. 510 */ 511 if (PagePrivate(page)) { 512 if (!try_to_release_page(page, sc->gfp_mask)) 513 goto activate_locked; 514 if (!mapping && page_count(page) == 1) 515 goto free_it; 516 } 517 518 if (!mapping) 519 goto keep_locked; /* truncate got there first */ 520 521 write_lock_irq(&mapping->tree_lock); 522 523 /* 524 * The non-racy check for busy page. It is critical to check 525 * PageDirty _after_ making sure that the page is freeable and 526 * not in use by anybody. (pagecache + us == 2) 527 */ 528 if (unlikely(page_count(page) != 2)) 529 goto cannot_free; 530 smp_rmb(); 531 if (unlikely(PageDirty(page))) 532 goto cannot_free; 533 534#ifdef CONFIG_SWAP 535 if (PageSwapCache(page)) { 536 swp_entry_t swap = { .val = page_private(page) }; 537 __delete_from_swap_cache(page); 538 write_unlock_irq(&mapping->tree_lock); 539 swap_free(swap); 540 __put_page(page); /* The pagecache ref */ 541 goto free_it; 542 } 543#endif /* CONFIG_SWAP */ 544 545 __remove_from_page_cache(page); 546 write_unlock_irq(&mapping->tree_lock); 547 __put_page(page); 548 549free_it: 550 unlock_page(page); 551 reclaimed++; 552 if (!pagevec_add(&freed_pvec, page)) 553 __pagevec_release_nonlru(&freed_pvec); 554 continue; 555 556cannot_free: 557 write_unlock_irq(&mapping->tree_lock); 558 goto keep_locked; 559 560activate_locked: 561 SetPageActive(page); 562 pgactivate++; 563keep_locked: 564 unlock_page(page); 565keep: 566 list_add(&page->lru, &ret_pages); 567 BUG_ON(PageLRU(page)); 568 } 569 list_splice(&ret_pages, page_list); 570 if (pagevec_count(&freed_pvec)) 571 __pagevec_release_nonlru(&freed_pvec); 572 mod_page_state(pgactivate, pgactivate); 573 sc->nr_reclaimed += reclaimed; 574 return reclaimed; 575} 576 577/* 578 * zone->lru_lock is heavily contended. Some of the functions that 579 * shrink the lists perform better by taking out a batch of pages 580 * and working on them outside the LRU lock. 581 * 582 * For pagecache intensive workloads, this function is the hottest 583 * spot in the kernel (apart from copy_*_user functions). 584 * 585 * Appropriate locks must be held before calling this function. 586 * 587 * @nr_to_scan: The number of pages to look through on the list. 588 * @src: The LRU list to pull pages off. 589 * @dst: The temp list to put pages on to. 590 * @scanned: The number of pages that were scanned. 591 * 592 * returns how many pages were moved onto *@dst. 593 */ 594static int isolate_lru_pages(int nr_to_scan, struct list_head *src, 595 struct list_head *dst, int *scanned) 596{ 597 int nr_taken = 0; 598 struct page *page; 599 int scan = 0; 600 601 while (scan++ < nr_to_scan && !list_empty(src)) { 602 page = lru_to_page(src); 603 prefetchw_prev_lru_page(page, src, flags); 604 605 if (!TestClearPageLRU(page)) 606 BUG(); 607 list_del(&page->lru); 608 if (get_page_testone(page)) { 609 /* 610 * It is being freed elsewhere 611 */ 612 __put_page(page); 613 SetPageLRU(page); 614 list_add(&page->lru, src); 615 continue; 616 } else { 617 list_add(&page->lru, dst); 618 nr_taken++; 619 } 620 } 621 622 *scanned = scan; 623 return nr_taken; 624} 625 626/* 627 * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed 628 */ 629static void shrink_cache(struct zone *zone, struct scan_control *sc) 630{ 631 LIST_HEAD(page_list); 632 struct pagevec pvec; 633 int max_scan = sc->nr_to_scan; 634 635 pagevec_init(&pvec, 1); 636 637 lru_add_drain(); 638 spin_lock_irq(&zone->lru_lock); 639 while (max_scan > 0) { 640 struct page *page; 641 int nr_taken; 642 int nr_scan; 643 int nr_freed; 644 645 nr_taken = isolate_lru_pages(sc->swap_cluster_max, 646 &zone->inactive_list, 647 &page_list, &nr_scan); 648 zone->nr_inactive -= nr_taken; 649 zone->pages_scanned += nr_scan; 650 spin_unlock_irq(&zone->lru_lock); 651 652 if (nr_taken == 0) 653 goto done; 654 655 max_scan -= nr_scan; 656 if (current_is_kswapd()) 657 mod_page_state_zone(zone, pgscan_kswapd, nr_scan); 658 else 659 mod_page_state_zone(zone, pgscan_direct, nr_scan); 660 nr_freed = shrink_list(&page_list, sc); 661 if (current_is_kswapd()) 662 mod_page_state(kswapd_steal, nr_freed); 663 mod_page_state_zone(zone, pgsteal, nr_freed); 664 sc->nr_to_reclaim -= nr_freed; 665 666 spin_lock_irq(&zone->lru_lock); 667 /* 668 * Put back any unfreeable pages. 669 */ 670 while (!list_empty(&page_list)) { 671 page = lru_to_page(&page_list); 672 if (TestSetPageLRU(page)) 673 BUG(); 674 list_del(&page->lru); 675 if (PageActive(page)) 676 add_page_to_active_list(zone, page); 677 else 678 add_page_to_inactive_list(zone, page); 679 if (!pagevec_add(&pvec, page)) { 680 spin_unlock_irq(&zone->lru_lock); 681 __pagevec_release(&pvec); 682 spin_lock_irq(&zone->lru_lock); 683 } 684 } 685 } 686 spin_unlock_irq(&zone->lru_lock); 687done: 688 pagevec_release(&pvec); 689} 690 691/* 692 * This moves pages from the active list to the inactive list. 693 * 694 * We move them the other way if the page is referenced by one or more 695 * processes, from rmap. 696 * 697 * If the pages are mostly unmapped, the processing is fast and it is 698 * appropriate to hold zone->lru_lock across the whole operation. But if 699 * the pages are mapped, the processing is slow (page_referenced()) so we 700 * should drop zone->lru_lock around each page. It's impossible to balance 701 * this, so instead we remove the pages from the LRU while processing them. 702 * It is safe to rely on PG_active against the non-LRU pages in here because 703 * nobody will play with that bit on a non-LRU page. 704 * 705 * The downside is that we have to touch page->_count against each page. 706 * But we had to alter page->flags anyway. 707 */ 708static void 709refill_inactive_zone(struct zone *zone, struct scan_control *sc) 710{ 711 int pgmoved; 712 int pgdeactivate = 0; 713 int pgscanned; 714 int nr_pages = sc->nr_to_scan; 715 LIST_HEAD(l_hold); /* The pages which were snipped off */ 716 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ 717 LIST_HEAD(l_active); /* Pages to go onto the active_list */ 718 struct page *page; 719 struct pagevec pvec; 720 int reclaim_mapped = 0; 721 long mapped_ratio; 722 long distress; 723 long swap_tendency; 724 725 lru_add_drain(); 726 spin_lock_irq(&zone->lru_lock); 727 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, 728 &l_hold, &pgscanned); 729 zone->pages_scanned += pgscanned; 730 zone->nr_active -= pgmoved; 731 spin_unlock_irq(&zone->lru_lock); 732 733 /* 734 * `distress' is a measure of how much trouble we're having reclaiming 735 * pages. 0 -> no problems. 100 -> great trouble. 736 */ 737 distress = 100 >> zone->prev_priority; 738 739 /* 740 * The point of this algorithm is to decide when to start reclaiming 741 * mapped memory instead of just pagecache. Work out how much memory 742 * is mapped. 743 */ 744 mapped_ratio = (sc->nr_mapped * 100) / total_memory; 745 746 /* 747 * Now decide how much we really want to unmap some pages. The mapped 748 * ratio is downgraded - just because there's a lot of mapped memory 749 * doesn't necessarily mean that page reclaim isn't succeeding. 750 * 751 * The distress ratio is important - we don't want to start going oom. 752 * 753 * A 100% value of vm_swappiness overrides this algorithm altogether. 754 */ 755 swap_tendency = mapped_ratio / 2 + distress + vm_swappiness; 756 757 /* 758 * Now use this metric to decide whether to start moving mapped memory 759 * onto the inactive list. 760 */ 761 if (swap_tendency >= 100) 762 reclaim_mapped = 1; 763 764 while (!list_empty(&l_hold)) { 765 cond_resched(); 766 page = lru_to_page(&l_hold); 767 list_del(&page->lru); 768 if (page_mapped(page)) { 769 if (!reclaim_mapped || 770 (total_swap_pages == 0 && PageAnon(page)) || 771 page_referenced(page, 0)) { 772 list_add(&page->lru, &l_active); 773 continue; 774 } 775 } 776 list_add(&page->lru, &l_inactive); 777 } 778 779 pagevec_init(&pvec, 1); 780 pgmoved = 0; 781 spin_lock_irq(&zone->lru_lock); 782 while (!list_empty(&l_inactive)) { 783 page = lru_to_page(&l_inactive); 784 prefetchw_prev_lru_page(page, &l_inactive, flags); 785 if (TestSetPageLRU(page)) 786 BUG(); 787 if (!TestClearPageActive(page)) 788 BUG(); 789 list_move(&page->lru, &zone->inactive_list); 790 pgmoved++; 791 if (!pagevec_add(&pvec, page)) { 792 zone->nr_inactive += pgmoved; 793 spin_unlock_irq(&zone->lru_lock); 794 pgdeactivate += pgmoved; 795 pgmoved = 0; 796 if (buffer_heads_over_limit) 797 pagevec_strip(&pvec); 798 __pagevec_release(&pvec); 799 spin_lock_irq(&zone->lru_lock); 800 } 801 } 802 zone->nr_inactive += pgmoved; 803 pgdeactivate += pgmoved; 804 if (buffer_heads_over_limit) { 805 spin_unlock_irq(&zone->lru_lock); 806 pagevec_strip(&pvec); 807 spin_lock_irq(&zone->lru_lock); 808 } 809 810 pgmoved = 0; 811 while (!list_empty(&l_active)) { 812 page = lru_to_page(&l_active); 813 prefetchw_prev_lru_page(page, &l_active, flags); 814 if (TestSetPageLRU(page)) 815 BUG(); 816 BUG_ON(!PageActive(page)); 817 list_move(&page->lru, &zone->active_list); 818 pgmoved++; 819 if (!pagevec_add(&pvec, page)) { 820 zone->nr_active += pgmoved; 821 pgmoved = 0; 822 spin_unlock_irq(&zone->lru_lock); 823 __pagevec_release(&pvec); 824 spin_lock_irq(&zone->lru_lock); 825 } 826 } 827 zone->nr_active += pgmoved; 828 spin_unlock_irq(&zone->lru_lock); 829 pagevec_release(&pvec); 830 831 mod_page_state_zone(zone, pgrefill, pgscanned); 832 mod_page_state(pgdeactivate, pgdeactivate); 833} 834 835/* 836 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 837 */ 838static void 839shrink_zone(struct zone *zone, struct scan_control *sc) 840{ 841 unsigned long nr_active; 842 unsigned long nr_inactive; 843 844 atomic_inc(&zone->reclaim_in_progress); 845 846 /* 847 * Add one to `nr_to_scan' just to make sure that the kernel will 848 * slowly sift through the active list. 849 */ 850 zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1; 851 nr_active = zone->nr_scan_active; 852 if (nr_active >= sc->swap_cluster_max) 853 zone->nr_scan_active = 0; 854 else 855 nr_active = 0; 856 857 zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1; 858 nr_inactive = zone->nr_scan_inactive; 859 if (nr_inactive >= sc->swap_cluster_max) 860 zone->nr_scan_inactive = 0; 861 else 862 nr_inactive = 0; 863 864 sc->nr_to_reclaim = sc->swap_cluster_max; 865 866 while (nr_active || nr_inactive) { 867 if (nr_active) { 868 sc->nr_to_scan = min(nr_active, 869 (unsigned long)sc->swap_cluster_max); 870 nr_active -= sc->nr_to_scan; 871 refill_inactive_zone(zone, sc); 872 } 873 874 if (nr_inactive) { 875 sc->nr_to_scan = min(nr_inactive, 876 (unsigned long)sc->swap_cluster_max); 877 nr_inactive -= sc->nr_to_scan; 878 shrink_cache(zone, sc); 879 if (sc->nr_to_reclaim <= 0) 880 break; 881 } 882 } 883 884 throttle_vm_writeout(); 885 886 atomic_dec(&zone->reclaim_in_progress); 887} 888 889/* 890 * This is the direct reclaim path, for page-allocating processes. We only 891 * try to reclaim pages from zones which will satisfy the caller's allocation 892 * request. 893 * 894 * We reclaim from a zone even if that zone is over pages_high. Because: 895 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 896 * allocation or 897 * b) The zones may be over pages_high but they must go *over* pages_high to 898 * satisfy the `incremental min' zone defense algorithm. 899 * 900 * Returns the number of reclaimed pages. 901 * 902 * If a zone is deemed to be full of pinned pages then just give it a light 903 * scan then give up on it. 904 */ 905static void 906shrink_caches(struct zone **zones, struct scan_control *sc) 907{ 908 int i; 909 910 for (i = 0; zones[i] != NULL; i++) { 911 struct zone *zone = zones[i]; 912 913 if (zone->present_pages == 0) 914 continue; 915 916 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 917 continue; 918 919 zone->temp_priority = sc->priority; 920 if (zone->prev_priority > sc->priority) 921 zone->prev_priority = sc->priority; 922 923 if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY) 924 continue; /* Let kswapd poll it */ 925 926 shrink_zone(zone, sc); 927 } 928} 929 930/* 931 * This is the main entry point to direct page reclaim. 932 * 933 * If a full scan of the inactive list fails to free enough memory then we 934 * are "out of memory" and something needs to be killed. 935 * 936 * If the caller is !__GFP_FS then the probability of a failure is reasonably 937 * high - the zone may be full of dirty or under-writeback pages, which this 938 * caller can't do much about. We kick pdflush and take explicit naps in the 939 * hope that some of these pages can be written. But if the allocating task 940 * holds filesystem locks which prevent writeout this might not work, and the 941 * allocation attempt will fail. 942 */ 943int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) 944{ 945 int priority; 946 int ret = 0; 947 int total_scanned = 0, total_reclaimed = 0; 948 struct reclaim_state *reclaim_state = current->reclaim_state; 949 struct scan_control sc; 950 unsigned long lru_pages = 0; 951 int i; 952 953 sc.gfp_mask = gfp_mask; 954 sc.may_writepage = 0; 955 sc.may_swap = 1; 956 957 inc_page_state(allocstall); 958 959 for (i = 0; zones[i] != NULL; i++) { 960 struct zone *zone = zones[i]; 961 962 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 963 continue; 964 965 zone->temp_priority = DEF_PRIORITY; 966 lru_pages += zone->nr_active + zone->nr_inactive; 967 } 968 969 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 970 sc.nr_mapped = read_page_state(nr_mapped); 971 sc.nr_scanned = 0; 972 sc.nr_reclaimed = 0; 973 sc.priority = priority; 974 sc.swap_cluster_max = SWAP_CLUSTER_MAX; 975 if (!priority) 976 disable_swap_token(); 977 shrink_caches(zones, &sc); 978 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); 979 if (reclaim_state) { 980 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 981 reclaim_state->reclaimed_slab = 0; 982 } 983 total_scanned += sc.nr_scanned; 984 total_reclaimed += sc.nr_reclaimed; 985 if (total_reclaimed >= sc.swap_cluster_max) { 986 ret = 1; 987 goto out; 988 } 989 990 /* 991 * Try to write back as many pages as we just scanned. This 992 * tends to cause slow streaming writers to write data to the 993 * disk smoothly, at the dirtying rate, which is nice. But 994 * that's undesirable in laptop mode, where we *want* lumpy 995 * writeout. So in laptop mode, write out the whole world. 996 */ 997 if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) { 998 wakeup_pdflush(laptop_mode ? 0 : total_scanned); 999 sc.may_writepage = 1; 1000 } 1001 1002 /* Take a nap, wait for some writeback to complete */ 1003 if (sc.nr_scanned && priority < DEF_PRIORITY - 2) 1004 blk_congestion_wait(WRITE, HZ/10); 1005 } 1006out: 1007 for (i = 0; zones[i] != 0; i++) { 1008 struct zone *zone = zones[i]; 1009 1010 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 1011 continue; 1012 1013 zone->prev_priority = zone->temp_priority; 1014 } 1015 return ret; 1016} 1017 1018/* 1019 * For kswapd, balance_pgdat() will work across all this node's zones until 1020 * they are all at pages_high. 1021 * 1022 * If `nr_pages' is non-zero then it is the number of pages which are to be 1023 * reclaimed, regardless of the zone occupancies. This is a software suspend 1024 * special. 1025 * 1026 * Returns the number of pages which were actually freed. 1027 * 1028 * There is special handling here for zones which are full of pinned pages. 1029 * This can happen if the pages are all mlocked, or if they are all used by 1030 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 1031 * What we do is to detect the case where all pages in the zone have been 1032 * scanned twice and there has been zero successful reclaim. Mark the zone as 1033 * dead and from now on, only perform a short scan. Basically we're polling 1034 * the zone for when the problem goes away. 1035 * 1036 * kswapd scans the zones in the highmem->normal->dma direction. It skips 1037 * zones which have free_pages > pages_high, but once a zone is found to have 1038 * free_pages <= pages_high, we scan that zone and the lower zones regardless 1039 * of the number of free pages in the lower zones. This interoperates with 1040 * the page allocator fallback scheme to ensure that aging of pages is balanced 1041 * across the zones. 1042 */ 1043static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) 1044{ 1045 int to_free = nr_pages; 1046 int all_zones_ok; 1047 int priority; 1048 int i; 1049 int total_scanned, total_reclaimed; 1050 struct reclaim_state *reclaim_state = current->reclaim_state; 1051 struct scan_control sc; 1052 1053loop_again: 1054 total_scanned = 0; 1055 total_reclaimed = 0; 1056 sc.gfp_mask = GFP_KERNEL; 1057 sc.may_writepage = 0; 1058 sc.may_swap = 1; 1059 sc.nr_mapped = read_page_state(nr_mapped); 1060 1061 inc_page_state(pageoutrun); 1062 1063 for (i = 0; i < pgdat->nr_zones; i++) { 1064 struct zone *zone = pgdat->node_zones + i; 1065 1066 zone->temp_priority = DEF_PRIORITY; 1067 } 1068 1069 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1070 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 1071 unsigned long lru_pages = 0; 1072 1073 /* The swap token gets in the way of swapout... */ 1074 if (!priority) 1075 disable_swap_token(); 1076 1077 all_zones_ok = 1; 1078 1079 if (nr_pages == 0) { 1080 /* 1081 * Scan in the highmem->dma direction for the highest 1082 * zone which needs scanning 1083 */ 1084 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 1085 struct zone *zone = pgdat->node_zones + i; 1086 1087 if (zone->present_pages == 0) 1088 continue; 1089 1090 if (zone->all_unreclaimable && 1091 priority != DEF_PRIORITY) 1092 continue; 1093 1094 if (!zone_watermark_ok(zone, order, 1095 zone->pages_high, 0, 0)) { 1096 end_zone = i; 1097 goto scan; 1098 } 1099 } 1100 goto out; 1101 } else { 1102 end_zone = pgdat->nr_zones - 1; 1103 } 1104scan: 1105 for (i = 0; i <= end_zone; i++) { 1106 struct zone *zone = pgdat->node_zones + i; 1107 1108 lru_pages += zone->nr_active + zone->nr_inactive; 1109 } 1110 1111 /* 1112 * Now scan the zone in the dma->highmem direction, stopping 1113 * at the last zone which needs scanning. 1114 * 1115 * We do this because the page allocator works in the opposite 1116 * direction. This prevents the page allocator from allocating 1117 * pages behind kswapd's direction of progress, which would 1118 * cause too much scanning of the lower zones. 1119 */ 1120 for (i = 0; i <= end_zone; i++) { 1121 struct zone *zone = pgdat->node_zones + i; 1122 int nr_slab; 1123 1124 if (zone->present_pages == 0) 1125 continue; 1126 1127 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1128 continue; 1129 1130 if (nr_pages == 0) { /* Not software suspend */ 1131 if (!zone_watermark_ok(zone, order, 1132 zone->pages_high, end_zone, 0)) 1133 all_zones_ok = 0; 1134 } 1135 zone->temp_priority = priority; 1136 if (zone->prev_priority > priority) 1137 zone->prev_priority = priority; 1138 sc.nr_scanned = 0; 1139 sc.nr_reclaimed = 0; 1140 sc.priority = priority; 1141 sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; 1142 atomic_inc(&zone->reclaim_in_progress); 1143 shrink_zone(zone, &sc); 1144 atomic_dec(&zone->reclaim_in_progress); 1145 reclaim_state->reclaimed_slab = 0; 1146 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 1147 lru_pages); 1148 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 1149 total_reclaimed += sc.nr_reclaimed; 1150 total_scanned += sc.nr_scanned; 1151 if (zone->all_unreclaimable) 1152 continue; 1153 if (nr_slab == 0 && zone->pages_scanned >= 1154 (zone->nr_active + zone->nr_inactive) * 4) 1155 zone->all_unreclaimable = 1; 1156 /* 1157 * If we've done a decent amount of scanning and 1158 * the reclaim ratio is low, start doing writepage 1159 * even in laptop mode 1160 */ 1161 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 1162 total_scanned > total_reclaimed+total_reclaimed/2) 1163 sc.may_writepage = 1; 1164 } 1165 if (nr_pages && to_free > total_reclaimed) 1166 continue; /* swsusp: need to do more work */ 1167 if (all_zones_ok) 1168 break; /* kswapd: all done */ 1169 /* 1170 * OK, kswapd is getting into trouble. Take a nap, then take 1171 * another pass across the zones. 1172 */ 1173 if (total_scanned && priority < DEF_PRIORITY - 2) 1174 blk_congestion_wait(WRITE, HZ/10); 1175 1176 /* 1177 * We do this so kswapd doesn't build up large priorities for 1178 * example when it is freeing in parallel with allocators. It 1179 * matches the direct reclaim path behaviour in terms of impact 1180 * on zone->*_priority. 1181 */ 1182 if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) 1183 break; 1184 } 1185out: 1186 for (i = 0; i < pgdat->nr_zones; i++) { 1187 struct zone *zone = pgdat->node_zones + i; 1188 1189 zone->prev_priority = zone->temp_priority; 1190 } 1191 if (!all_zones_ok) { 1192 cond_resched(); 1193 goto loop_again; 1194 } 1195 1196 return total_reclaimed; 1197} 1198 1199/* 1200 * The background pageout daemon, started as a kernel thread 1201 * from the init process. 1202 * 1203 * This basically trickles out pages so that we have _some_ 1204 * free memory available even if there is no other activity 1205 * that frees anything up. This is needed for things like routing 1206 * etc, where we otherwise might have all activity going on in 1207 * asynchronous contexts that cannot page things out. 1208 * 1209 * If there are applications that are active memory-allocators 1210 * (most normal use), this basically shouldn't matter. 1211 */ 1212static int kswapd(void *p) 1213{ 1214 unsigned long order; 1215 pg_data_t *pgdat = (pg_data_t*)p; 1216 struct task_struct *tsk = current; 1217 DEFINE_WAIT(wait); 1218 struct reclaim_state reclaim_state = { 1219 .reclaimed_slab = 0, 1220 }; 1221 cpumask_t cpumask; 1222 1223 daemonize("kswapd%d", pgdat->node_id); 1224 cpumask = node_to_cpumask(pgdat->node_id); 1225 if (!cpus_empty(cpumask)) 1226 set_cpus_allowed(tsk, cpumask); 1227 current->reclaim_state = &reclaim_state; 1228 1229 /* 1230 * Tell the memory management that we're a "memory allocator", 1231 * and that if we need more memory we should get access to it 1232 * regardless (see "__alloc_pages()"). "kswapd" should 1233 * never get caught in the normal page freeing logic. 1234 * 1235 * (Kswapd normally doesn't need memory anyway, but sometimes 1236 * you need a small amount of memory in order to be able to 1237 * page out something else, and this flag essentially protects 1238 * us from recursively trying to free more memory as we're 1239 * trying to free the first piece of memory in the first place). 1240 */ 1241 tsk->flags |= PF_MEMALLOC|PF_KSWAPD; 1242 1243 order = 0; 1244 for ( ; ; ) { 1245 unsigned long new_order; 1246 1247 try_to_freeze(); 1248 1249 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 1250 new_order = pgdat->kswapd_max_order; 1251 pgdat->kswapd_max_order = 0; 1252 if (order < new_order) { 1253 /* 1254 * Don't sleep if someone wants a larger 'order' 1255 * allocation 1256 */ 1257 order = new_order; 1258 } else { 1259 schedule(); 1260 order = pgdat->kswapd_max_order; 1261 } 1262 finish_wait(&pgdat->kswapd_wait, &wait); 1263 1264 balance_pgdat(pgdat, 0, order); 1265 } 1266 return 0; 1267} 1268 1269/* 1270 * A zone is low on free memory, so wake its kswapd task to service it. 1271 */ 1272void wakeup_kswapd(struct zone *zone, int order) 1273{ 1274 pg_data_t *pgdat; 1275 1276 if (zone->present_pages == 0) 1277 return; 1278 1279 pgdat = zone->zone_pgdat; 1280 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) 1281 return; 1282 if (pgdat->kswapd_max_order < order) 1283 pgdat->kswapd_max_order = order; 1284 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) 1285 return; 1286 if (!waitqueue_active(&pgdat->kswapd_wait)) 1287 return; 1288 wake_up_interruptible(&pgdat->kswapd_wait); 1289} 1290 1291#ifdef CONFIG_PM 1292/* 1293 * Try to free `nr_pages' of memory, system-wide. Returns the number of freed 1294 * pages. 1295 */ 1296int shrink_all_memory(int nr_pages) 1297{ 1298 pg_data_t *pgdat; 1299 int nr_to_free = nr_pages; 1300 int ret = 0; 1301 struct reclaim_state reclaim_state = { 1302 .reclaimed_slab = 0, 1303 }; 1304 1305 current->reclaim_state = &reclaim_state; 1306 for_each_pgdat(pgdat) { 1307 int freed; 1308 freed = balance_pgdat(pgdat, nr_to_free, 0); 1309 ret += freed; 1310 nr_to_free -= freed; 1311 if (nr_to_free <= 0) 1312 break; 1313 } 1314 current->reclaim_state = NULL; 1315 return ret; 1316} 1317#endif 1318 1319#ifdef CONFIG_HOTPLUG_CPU 1320/* It's optimal to keep kswapds on the same CPUs as their memory, but 1321 not required for correctness. So if the last cpu in a node goes 1322 away, we get changed to run anywhere: as the first one comes back, 1323 restore their cpu bindings. */ 1324static int __devinit cpu_callback(struct notifier_block *nfb, 1325 unsigned long action, 1326 void *hcpu) 1327{ 1328 pg_data_t *pgdat; 1329 cpumask_t mask; 1330 1331 if (action == CPU_ONLINE) { 1332 for_each_pgdat(pgdat) { 1333 mask = node_to_cpumask(pgdat->node_id); 1334 if (any_online_cpu(mask) != NR_CPUS) 1335 /* One of our CPUs online: restore mask */ 1336 set_cpus_allowed(pgdat->kswapd, mask); 1337 } 1338 } 1339 return NOTIFY_OK; 1340} 1341#endif /* CONFIG_HOTPLUG_CPU */ 1342 1343static int __init kswapd_init(void) 1344{ 1345 pg_data_t *pgdat; 1346 swap_setup(); 1347 for_each_pgdat(pgdat) 1348 pgdat->kswapd 1349 = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); 1350 total_memory = nr_free_pagecache_pages(); 1351 hotcpu_notifier(cpu_callback, 0); 1352 return 0; 1353} 1354 1355module_init(kswapd_init) 1356 1357 1358/* 1359 * Try to free up some pages from this zone through reclaim. 1360 */ 1361int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 1362{ 1363 struct scan_control sc; 1364 int nr_pages = 1 << order; 1365 int total_reclaimed = 0; 1366 1367 /* The reclaim may sleep, so don't do it if sleep isn't allowed */ 1368 if (!(gfp_mask & __GFP_WAIT)) 1369 return 0; 1370 if (zone->all_unreclaimable) 1371 return 0; 1372 1373 sc.gfp_mask = gfp_mask; 1374 sc.may_writepage = 0; 1375 sc.may_swap = 0; 1376 sc.nr_mapped = read_page_state(nr_mapped); 1377 sc.nr_scanned = 0; 1378 sc.nr_reclaimed = 0; 1379 /* scan at the highest priority */ 1380 sc.priority = 0; 1381 disable_swap_token(); 1382 1383 if (nr_pages > SWAP_CLUSTER_MAX) 1384 sc.swap_cluster_max = nr_pages; 1385 else 1386 sc.swap_cluster_max = SWAP_CLUSTER_MAX; 1387 1388 /* Don't reclaim the zone if there are other reclaimers active */ 1389 if (atomic_read(&zone->reclaim_in_progress) > 0) 1390 goto out; 1391 1392 shrink_zone(zone, &sc); 1393 total_reclaimed = sc.nr_reclaimed; 1394 1395 out: 1396 return total_reclaimed; 1397} 1398 1399asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone, 1400 unsigned int state) 1401{ 1402 struct zone *z; 1403 int i; 1404 1405 if (!capable(CAP_SYS_ADMIN)) 1406 return -EACCES; 1407 1408 if (node >= MAX_NUMNODES || !node_online(node)) 1409 return -EINVAL; 1410 1411 /* This will break if we ever add more zones */ 1412 if (!(zone & (1<<ZONE_DMA|1<<ZONE_NORMAL|1<<ZONE_HIGHMEM))) 1413 return -EINVAL; 1414 1415 for (i = 0; i < MAX_NR_ZONES; i++) { 1416 if (!(zone & 1<<i)) 1417 continue; 1418 1419 z = &NODE_DATA(node)->node_zones[i]; 1420 1421 if (state) 1422 z->reclaim_pages = 1; 1423 else 1424 z->reclaim_pages = 0; 1425 } 1426 1427 return 0; 1428} 1429