bzip2/lzma: move initrd/ramfs options out of BLK_DEV
[linux-2.6/cjktty.git] / mm / vmscan.c
blobd196f46c8808ea56734f12501d0e53968cc3f4eb
1 /*
2 * linux/mm/vmscan.c
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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.
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>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
49 #include "internal.h"
51 struct scan_control {
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
55 /* This context's GFP mask */
56 gfp_t gfp_mask;
58 int may_writepage;
60 /* Can pages be swapped as part of reclaim? */
61 int may_swap;
63 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
64 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
65 * In this context, it doesn't matter that we scan the
66 * whole list at once. */
67 int swap_cluster_max;
69 int swappiness;
71 int all_unreclaimable;
73 int order;
75 /* Which cgroup do we reclaim from */
76 struct mem_cgroup *mem_cgroup;
78 /* Pluggable isolate pages callback */
79 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
80 unsigned long *scanned, int order, int mode,
81 struct zone *z, struct mem_cgroup *mem_cont,
82 int active, int file);
85 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
87 #ifdef ARCH_HAS_PREFETCH
88 #define prefetch_prev_lru_page(_page, _base, _field) \
89 do { \
90 if ((_page)->lru.prev != _base) { \
91 struct page *prev; \
93 prev = lru_to_page(&(_page->lru)); \
94 prefetch(&prev->_field); \
95 } \
96 } while (0)
97 #else
98 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
99 #endif
101 #ifdef ARCH_HAS_PREFETCHW
102 #define prefetchw_prev_lru_page(_page, _base, _field) \
103 do { \
104 if ((_page)->lru.prev != _base) { \
105 struct page *prev; \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetchw(&prev->_field); \
110 } while (0)
111 #else
112 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
113 #endif
116 * From 0 .. 100. Higher means more swappy.
118 int vm_swappiness = 60;
119 long vm_total_pages; /* The total number of pages which the VM controls */
121 static LIST_HEAD(shrinker_list);
122 static DECLARE_RWSEM(shrinker_rwsem);
124 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
125 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
126 #else
127 #define scan_global_lru(sc) (1)
128 #endif
131 * Add a shrinker callback to be called from the vm
133 void register_shrinker(struct shrinker *shrinker)
135 shrinker->nr = 0;
136 down_write(&shrinker_rwsem);
137 list_add_tail(&shrinker->list, &shrinker_list);
138 up_write(&shrinker_rwsem);
140 EXPORT_SYMBOL(register_shrinker);
143 * Remove one
145 void unregister_shrinker(struct shrinker *shrinker)
147 down_write(&shrinker_rwsem);
148 list_del(&shrinker->list);
149 up_write(&shrinker_rwsem);
151 EXPORT_SYMBOL(unregister_shrinker);
153 #define SHRINK_BATCH 128
155 * Call the shrink functions to age shrinkable caches
157 * Here we assume it costs one seek to replace a lru page and that it also
158 * takes a seek to recreate a cache object. With this in mind we age equal
159 * percentages of the lru and ageable caches. This should balance the seeks
160 * generated by these structures.
162 * If the vm encountered mapped pages on the LRU it increase the pressure on
163 * slab to avoid swapping.
165 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
167 * `lru_pages' represents the number of on-LRU pages in all the zones which
168 * are eligible for the caller's allocation attempt. It is used for balancing
169 * slab reclaim versus page reclaim.
171 * Returns the number of slab objects which we shrunk.
173 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
174 unsigned long lru_pages)
176 struct shrinker *shrinker;
177 unsigned long ret = 0;
179 if (scanned == 0)
180 scanned = SWAP_CLUSTER_MAX;
182 if (!down_read_trylock(&shrinker_rwsem))
183 return 1; /* Assume we'll be able to shrink next time */
185 list_for_each_entry(shrinker, &shrinker_list, list) {
186 unsigned long long delta;
187 unsigned long total_scan;
188 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
190 delta = (4 * scanned) / shrinker->seeks;
191 delta *= max_pass;
192 do_div(delta, lru_pages + 1);
193 shrinker->nr += delta;
194 if (shrinker->nr < 0) {
195 printk(KERN_ERR "%s: nr=%ld\n",
196 __func__, shrinker->nr);
197 shrinker->nr = max_pass;
201 * Avoid risking looping forever due to too large nr value:
202 * never try to free more than twice the estimate number of
203 * freeable entries.
205 if (shrinker->nr > max_pass * 2)
206 shrinker->nr = max_pass * 2;
208 total_scan = shrinker->nr;
209 shrinker->nr = 0;
211 while (total_scan >= SHRINK_BATCH) {
212 long this_scan = SHRINK_BATCH;
213 int shrink_ret;
214 int nr_before;
216 nr_before = (*shrinker->shrink)(0, gfp_mask);
217 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
218 if (shrink_ret == -1)
219 break;
220 if (shrink_ret < nr_before)
221 ret += nr_before - shrink_ret;
222 count_vm_events(SLABS_SCANNED, this_scan);
223 total_scan -= this_scan;
225 cond_resched();
228 shrinker->nr += total_scan;
230 up_read(&shrinker_rwsem);
231 return ret;
234 /* Called without lock on whether page is mapped, so answer is unstable */
235 static inline int page_mapping_inuse(struct page *page)
237 struct address_space *mapping;
239 /* Page is in somebody's page tables. */
240 if (page_mapped(page))
241 return 1;
243 /* Be more reluctant to reclaim swapcache than pagecache */
244 if (PageSwapCache(page))
245 return 1;
247 mapping = page_mapping(page);
248 if (!mapping)
249 return 0;
251 /* File is mmap'd by somebody? */
252 return mapping_mapped(mapping);
255 static inline int is_page_cache_freeable(struct page *page)
257 return page_count(page) - !!PagePrivate(page) == 2;
260 static int may_write_to_queue(struct backing_dev_info *bdi)
262 if (current->flags & PF_SWAPWRITE)
263 return 1;
264 if (!bdi_write_congested(bdi))
265 return 1;
266 if (bdi == current->backing_dev_info)
267 return 1;
268 return 0;
272 * We detected a synchronous write error writing a page out. Probably
273 * -ENOSPC. We need to propagate that into the address_space for a subsequent
274 * fsync(), msync() or close().
276 * The tricky part is that after writepage we cannot touch the mapping: nothing
277 * prevents it from being freed up. But we have a ref on the page and once
278 * that page is locked, the mapping is pinned.
280 * We're allowed to run sleeping lock_page() here because we know the caller has
281 * __GFP_FS.
283 static void handle_write_error(struct address_space *mapping,
284 struct page *page, int error)
286 lock_page(page);
287 if (page_mapping(page) == mapping)
288 mapping_set_error(mapping, error);
289 unlock_page(page);
292 /* Request for sync pageout. */
293 enum pageout_io {
294 PAGEOUT_IO_ASYNC,
295 PAGEOUT_IO_SYNC,
298 /* possible outcome of pageout() */
299 typedef enum {
300 /* failed to write page out, page is locked */
301 PAGE_KEEP,
302 /* move page to the active list, page is locked */
303 PAGE_ACTIVATE,
304 /* page has been sent to the disk successfully, page is unlocked */
305 PAGE_SUCCESS,
306 /* page is clean and locked */
307 PAGE_CLEAN,
308 } pageout_t;
311 * pageout is called by shrink_page_list() for each dirty page.
312 * Calls ->writepage().
314 static pageout_t pageout(struct page *page, struct address_space *mapping,
315 enum pageout_io sync_writeback)
318 * If the page is dirty, only perform writeback if that write
319 * will be non-blocking. To prevent this allocation from being
320 * stalled by pagecache activity. But note that there may be
321 * stalls if we need to run get_block(). We could test
322 * PagePrivate for that.
324 * If this process is currently in generic_file_write() against
325 * this page's queue, we can perform writeback even if that
326 * will block.
328 * If the page is swapcache, write it back even if that would
329 * block, for some throttling. This happens by accident, because
330 * swap_backing_dev_info is bust: it doesn't reflect the
331 * congestion state of the swapdevs. Easy to fix, if needed.
332 * See swapfile.c:page_queue_congested().
334 if (!is_page_cache_freeable(page))
335 return PAGE_KEEP;
336 if (!mapping) {
338 * Some data journaling orphaned pages can have
339 * page->mapping == NULL while being dirty with clean buffers.
341 if (PagePrivate(page)) {
342 if (try_to_free_buffers(page)) {
343 ClearPageDirty(page);
344 printk("%s: orphaned page\n", __func__);
345 return PAGE_CLEAN;
348 return PAGE_KEEP;
350 if (mapping->a_ops->writepage == NULL)
351 return PAGE_ACTIVATE;
352 if (!may_write_to_queue(mapping->backing_dev_info))
353 return PAGE_KEEP;
355 if (clear_page_dirty_for_io(page)) {
356 int res;
357 struct writeback_control wbc = {
358 .sync_mode = WB_SYNC_NONE,
359 .nr_to_write = SWAP_CLUSTER_MAX,
360 .range_start = 0,
361 .range_end = LLONG_MAX,
362 .nonblocking = 1,
363 .for_reclaim = 1,
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;
376 * Wait on writeback if requested to. This happens when
377 * direct reclaiming a large contiguous area and the
378 * first attempt to free a range of pages fails.
380 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
381 wait_on_page_writeback(page);
383 if (!PageWriteback(page)) {
384 /* synchronous write or broken a_ops? */
385 ClearPageReclaim(page);
387 inc_zone_page_state(page, NR_VMSCAN_WRITE);
388 return PAGE_SUCCESS;
391 return PAGE_CLEAN;
395 * Same as remove_mapping, but if the page is removed from the mapping, it
396 * gets returned with a refcount of 0.
398 static int __remove_mapping(struct address_space *mapping, struct page *page)
400 BUG_ON(!PageLocked(page));
401 BUG_ON(mapping != page_mapping(page));
403 spin_lock_irq(&mapping->tree_lock);
405 * The non racy check for a busy page.
407 * Must be careful with the order of the tests. When someone has
408 * a ref to the page, it may be possible that they dirty it then
409 * drop the reference. So if PageDirty is tested before page_count
410 * here, then the following race may occur:
412 * get_user_pages(&page);
413 * [user mapping goes away]
414 * write_to(page);
415 * !PageDirty(page) [good]
416 * SetPageDirty(page);
417 * put_page(page);
418 * !page_count(page) [good, discard it]
420 * [oops, our write_to data is lost]
422 * Reversing the order of the tests ensures such a situation cannot
423 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
424 * load is not satisfied before that of page->_count.
426 * Note that if SetPageDirty is always performed via set_page_dirty,
427 * and thus under tree_lock, then this ordering is not required.
429 if (!page_freeze_refs(page, 2))
430 goto cannot_free;
431 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
432 if (unlikely(PageDirty(page))) {
433 page_unfreeze_refs(page, 2);
434 goto cannot_free;
437 if (PageSwapCache(page)) {
438 swp_entry_t swap = { .val = page_private(page) };
439 __delete_from_swap_cache(page);
440 spin_unlock_irq(&mapping->tree_lock);
441 swap_free(swap);
442 } else {
443 __remove_from_page_cache(page);
444 spin_unlock_irq(&mapping->tree_lock);
447 return 1;
449 cannot_free:
450 spin_unlock_irq(&mapping->tree_lock);
451 return 0;
455 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
456 * someone else has a ref on the page, abort and return 0. If it was
457 * successfully detached, return 1. Assumes the caller has a single ref on
458 * this page.
460 int remove_mapping(struct address_space *mapping, struct page *page)
462 if (__remove_mapping(mapping, page)) {
464 * Unfreezing the refcount with 1 rather than 2 effectively
465 * drops the pagecache ref for us without requiring another
466 * atomic operation.
468 page_unfreeze_refs(page, 1);
469 return 1;
471 return 0;
475 * putback_lru_page - put previously isolated page onto appropriate LRU list
476 * @page: page to be put back to appropriate lru list
478 * Add previously isolated @page to appropriate LRU list.
479 * Page may still be unevictable for other reasons.
481 * lru_lock must not be held, interrupts must be enabled.
483 #ifdef CONFIG_UNEVICTABLE_LRU
484 void putback_lru_page(struct page *page)
486 int lru;
487 int active = !!TestClearPageActive(page);
488 int was_unevictable = PageUnevictable(page);
490 VM_BUG_ON(PageLRU(page));
492 redo:
493 ClearPageUnevictable(page);
495 if (page_evictable(page, NULL)) {
497 * For evictable pages, we can use the cache.
498 * In event of a race, worst case is we end up with an
499 * unevictable page on [in]active list.
500 * We know how to handle that.
502 lru = active + page_is_file_cache(page);
503 lru_cache_add_lru(page, lru);
504 } else {
506 * Put unevictable pages directly on zone's unevictable
507 * list.
509 lru = LRU_UNEVICTABLE;
510 add_page_to_unevictable_list(page);
512 mem_cgroup_move_lists(page, lru);
515 * page's status can change while we move it among lru. If an evictable
516 * page is on unevictable list, it never be freed. To avoid that,
517 * check after we added it to the list, again.
519 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
520 if (!isolate_lru_page(page)) {
521 put_page(page);
522 goto redo;
524 /* This means someone else dropped this page from LRU
525 * So, it will be freed or putback to LRU again. There is
526 * nothing to do here.
530 if (was_unevictable && lru != LRU_UNEVICTABLE)
531 count_vm_event(UNEVICTABLE_PGRESCUED);
532 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
533 count_vm_event(UNEVICTABLE_PGCULLED);
535 put_page(page); /* drop ref from isolate */
538 #else /* CONFIG_UNEVICTABLE_LRU */
540 void putback_lru_page(struct page *page)
542 int lru;
543 VM_BUG_ON(PageLRU(page));
545 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
546 lru_cache_add_lru(page, lru);
547 mem_cgroup_move_lists(page, lru);
548 put_page(page);
550 #endif /* CONFIG_UNEVICTABLE_LRU */
554 * shrink_page_list() returns the number of reclaimed pages
556 static unsigned long shrink_page_list(struct list_head *page_list,
557 struct scan_control *sc,
558 enum pageout_io sync_writeback)
560 LIST_HEAD(ret_pages);
561 struct pagevec freed_pvec;
562 int pgactivate = 0;
563 unsigned long nr_reclaimed = 0;
565 cond_resched();
567 pagevec_init(&freed_pvec, 1);
568 while (!list_empty(page_list)) {
569 struct address_space *mapping;
570 struct page *page;
571 int may_enter_fs;
572 int referenced;
574 cond_resched();
576 page = lru_to_page(page_list);
577 list_del(&page->lru);
579 if (!trylock_page(page))
580 goto keep;
582 VM_BUG_ON(PageActive(page));
584 sc->nr_scanned++;
586 if (unlikely(!page_evictable(page, NULL)))
587 goto cull_mlocked;
589 if (!sc->may_swap && page_mapped(page))
590 goto keep_locked;
592 /* Double the slab pressure for mapped and swapcache pages */
593 if (page_mapped(page) || PageSwapCache(page))
594 sc->nr_scanned++;
596 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
597 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
599 if (PageWriteback(page)) {
601 * Synchronous reclaim is performed in two passes,
602 * first an asynchronous pass over the list to
603 * start parallel writeback, and a second synchronous
604 * pass to wait for the IO to complete. Wait here
605 * for any page for which writeback has already
606 * started.
608 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
609 wait_on_page_writeback(page);
610 else
611 goto keep_locked;
614 referenced = page_referenced(page, 1, sc->mem_cgroup);
615 /* In active use or really unfreeable? Activate it. */
616 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
617 referenced && page_mapping_inuse(page))
618 goto activate_locked;
620 #ifdef CONFIG_SWAP
622 * Anonymous process memory has backing store?
623 * Try to allocate it some swap space here.
625 if (PageAnon(page) && !PageSwapCache(page)) {
626 if (!(sc->gfp_mask & __GFP_IO))
627 goto keep_locked;
628 switch (try_to_munlock(page)) {
629 case SWAP_FAIL: /* shouldn't happen */
630 case SWAP_AGAIN:
631 goto keep_locked;
632 case SWAP_MLOCK:
633 goto cull_mlocked;
634 case SWAP_SUCCESS:
635 ; /* fall thru'; add to swap cache */
637 if (!add_to_swap(page, GFP_ATOMIC))
638 goto activate_locked;
639 may_enter_fs = 1;
641 #endif /* CONFIG_SWAP */
643 mapping = page_mapping(page);
646 * The page is mapped into the page tables of one or more
647 * processes. Try to unmap it here.
649 if (page_mapped(page) && mapping) {
650 switch (try_to_unmap(page, 0)) {
651 case SWAP_FAIL:
652 goto activate_locked;
653 case SWAP_AGAIN:
654 goto keep_locked;
655 case SWAP_MLOCK:
656 goto cull_mlocked;
657 case SWAP_SUCCESS:
658 ; /* try to free the page below */
662 if (PageDirty(page)) {
663 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
664 goto keep_locked;
665 if (!may_enter_fs)
666 goto keep_locked;
667 if (!sc->may_writepage)
668 goto keep_locked;
670 /* Page is dirty, try to write it out here */
671 switch (pageout(page, mapping, sync_writeback)) {
672 case PAGE_KEEP:
673 goto keep_locked;
674 case PAGE_ACTIVATE:
675 goto activate_locked;
676 case PAGE_SUCCESS:
677 if (PageWriteback(page) || PageDirty(page))
678 goto keep;
680 * A synchronous write - probably a ramdisk. Go
681 * ahead and try to reclaim the page.
683 if (!trylock_page(page))
684 goto keep;
685 if (PageDirty(page) || PageWriteback(page))
686 goto keep_locked;
687 mapping = page_mapping(page);
688 case PAGE_CLEAN:
689 ; /* try to free the page below */
694 * If the page has buffers, try to free the buffer mappings
695 * associated with this page. If we succeed we try to free
696 * the page as well.
698 * We do this even if the page is PageDirty().
699 * try_to_release_page() does not perform I/O, but it is
700 * possible for a page to have PageDirty set, but it is actually
701 * clean (all its buffers are clean). This happens if the
702 * buffers were written out directly, with submit_bh(). ext3
703 * will do this, as well as the blockdev mapping.
704 * try_to_release_page() will discover that cleanness and will
705 * drop the buffers and mark the page clean - it can be freed.
707 * Rarely, pages can have buffers and no ->mapping. These are
708 * the pages which were not successfully invalidated in
709 * truncate_complete_page(). We try to drop those buffers here
710 * and if that worked, and the page is no longer mapped into
711 * process address space (page_count == 1) it can be freed.
712 * Otherwise, leave the page on the LRU so it is swappable.
714 if (PagePrivate(page)) {
715 if (!try_to_release_page(page, sc->gfp_mask))
716 goto activate_locked;
717 if (!mapping && page_count(page) == 1) {
718 unlock_page(page);
719 if (put_page_testzero(page))
720 goto free_it;
721 else {
723 * rare race with speculative reference.
724 * the speculative reference will free
725 * this page shortly, so we may
726 * increment nr_reclaimed here (and
727 * leave it off the LRU).
729 nr_reclaimed++;
730 continue;
735 if (!mapping || !__remove_mapping(mapping, page))
736 goto keep_locked;
739 * At this point, we have no other references and there is
740 * no way to pick any more up (removed from LRU, removed
741 * from pagecache). Can use non-atomic bitops now (and
742 * we obviously don't have to worry about waking up a process
743 * waiting on the page lock, because there are no references.
745 __clear_page_locked(page);
746 free_it:
747 nr_reclaimed++;
748 if (!pagevec_add(&freed_pvec, page)) {
749 __pagevec_free(&freed_pvec);
750 pagevec_reinit(&freed_pvec);
752 continue;
754 cull_mlocked:
755 unlock_page(page);
756 putback_lru_page(page);
757 continue;
759 activate_locked:
760 /* Not a candidate for swapping, so reclaim swap space. */
761 if (PageSwapCache(page) && vm_swap_full())
762 remove_exclusive_swap_page_ref(page);
763 VM_BUG_ON(PageActive(page));
764 SetPageActive(page);
765 pgactivate++;
766 keep_locked:
767 unlock_page(page);
768 keep:
769 list_add(&page->lru, &ret_pages);
770 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
772 list_splice(&ret_pages, page_list);
773 if (pagevec_count(&freed_pvec))
774 __pagevec_free(&freed_pvec);
775 count_vm_events(PGACTIVATE, pgactivate);
776 return nr_reclaimed;
779 /* LRU Isolation modes. */
780 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
781 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
782 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
785 * Attempt to remove the specified page from its LRU. Only take this page
786 * if it is of the appropriate PageActive status. Pages which are being
787 * freed elsewhere are also ignored.
789 * page: page to consider
790 * mode: one of the LRU isolation modes defined above
792 * returns 0 on success, -ve errno on failure.
794 int __isolate_lru_page(struct page *page, int mode, int file)
796 int ret = -EINVAL;
798 /* Only take pages on the LRU. */
799 if (!PageLRU(page))
800 return ret;
803 * When checking the active state, we need to be sure we are
804 * dealing with comparible boolean values. Take the logical not
805 * of each.
807 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
808 return ret;
810 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
811 return ret;
814 * When this function is being called for lumpy reclaim, we
815 * initially look into all LRU pages, active, inactive and
816 * unevictable; only give shrink_page_list evictable pages.
818 if (PageUnevictable(page))
819 return ret;
821 ret = -EBUSY;
822 if (likely(get_page_unless_zero(page))) {
824 * Be careful not to clear PageLRU until after we're
825 * sure the page is not being freed elsewhere -- the
826 * page release code relies on it.
828 ClearPageLRU(page);
829 ret = 0;
832 return ret;
836 * zone->lru_lock is heavily contended. Some of the functions that
837 * shrink the lists perform better by taking out a batch of pages
838 * and working on them outside the LRU lock.
840 * For pagecache intensive workloads, this function is the hottest
841 * spot in the kernel (apart from copy_*_user functions).
843 * Appropriate locks must be held before calling this function.
845 * @nr_to_scan: The number of pages to look through on the list.
846 * @src: The LRU list to pull pages off.
847 * @dst: The temp list to put pages on to.
848 * @scanned: The number of pages that were scanned.
849 * @order: The caller's attempted allocation order
850 * @mode: One of the LRU isolation modes
851 * @file: True [1] if isolating file [!anon] pages
853 * returns how many pages were moved onto *@dst.
855 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
856 struct list_head *src, struct list_head *dst,
857 unsigned long *scanned, int order, int mode, int file)
859 unsigned long nr_taken = 0;
860 unsigned long scan;
862 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
863 struct page *page;
864 unsigned long pfn;
865 unsigned long end_pfn;
866 unsigned long page_pfn;
867 int zone_id;
869 page = lru_to_page(src);
870 prefetchw_prev_lru_page(page, src, flags);
872 VM_BUG_ON(!PageLRU(page));
874 switch (__isolate_lru_page(page, mode, file)) {
875 case 0:
876 list_move(&page->lru, dst);
877 nr_taken++;
878 break;
880 case -EBUSY:
881 /* else it is being freed elsewhere */
882 list_move(&page->lru, src);
883 continue;
885 default:
886 BUG();
889 if (!order)
890 continue;
893 * Attempt to take all pages in the order aligned region
894 * surrounding the tag page. Only take those pages of
895 * the same active state as that tag page. We may safely
896 * round the target page pfn down to the requested order
897 * as the mem_map is guarenteed valid out to MAX_ORDER,
898 * where that page is in a different zone we will detect
899 * it from its zone id and abort this block scan.
901 zone_id = page_zone_id(page);
902 page_pfn = page_to_pfn(page);
903 pfn = page_pfn & ~((1 << order) - 1);
904 end_pfn = pfn + (1 << order);
905 for (; pfn < end_pfn; pfn++) {
906 struct page *cursor_page;
908 /* The target page is in the block, ignore it. */
909 if (unlikely(pfn == page_pfn))
910 continue;
912 /* Avoid holes within the zone. */
913 if (unlikely(!pfn_valid_within(pfn)))
914 break;
916 cursor_page = pfn_to_page(pfn);
918 /* Check that we have not crossed a zone boundary. */
919 if (unlikely(page_zone_id(cursor_page) != zone_id))
920 continue;
921 switch (__isolate_lru_page(cursor_page, mode, file)) {
922 case 0:
923 list_move(&cursor_page->lru, dst);
924 nr_taken++;
925 scan++;
926 break;
928 case -EBUSY:
929 /* else it is being freed elsewhere */
930 list_move(&cursor_page->lru, src);
931 default:
932 break; /* ! on LRU or wrong list */
937 *scanned = scan;
938 return nr_taken;
941 static unsigned long isolate_pages_global(unsigned long nr,
942 struct list_head *dst,
943 unsigned long *scanned, int order,
944 int mode, struct zone *z,
945 struct mem_cgroup *mem_cont,
946 int active, int file)
948 int lru = LRU_BASE;
949 if (active)
950 lru += LRU_ACTIVE;
951 if (file)
952 lru += LRU_FILE;
953 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
954 mode, !!file);
958 * clear_active_flags() is a helper for shrink_active_list(), clearing
959 * any active bits from the pages in the list.
961 static unsigned long clear_active_flags(struct list_head *page_list,
962 unsigned int *count)
964 int nr_active = 0;
965 int lru;
966 struct page *page;
968 list_for_each_entry(page, page_list, lru) {
969 lru = page_is_file_cache(page);
970 if (PageActive(page)) {
971 lru += LRU_ACTIVE;
972 ClearPageActive(page);
973 nr_active++;
975 count[lru]++;
978 return nr_active;
982 * isolate_lru_page - tries to isolate a page from its LRU list
983 * @page: page to isolate from its LRU list
985 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
986 * vmstat statistic corresponding to whatever LRU list the page was on.
988 * Returns 0 if the page was removed from an LRU list.
989 * Returns -EBUSY if the page was not on an LRU list.
991 * The returned page will have PageLRU() cleared. If it was found on
992 * the active list, it will have PageActive set. If it was found on
993 * the unevictable list, it will have the PageUnevictable bit set. That flag
994 * may need to be cleared by the caller before letting the page go.
996 * The vmstat statistic corresponding to the list on which the page was
997 * found will be decremented.
999 * Restrictions:
1000 * (1) Must be called with an elevated refcount on the page. This is a
1001 * fundamentnal difference from isolate_lru_pages (which is called
1002 * without a stable reference).
1003 * (2) the lru_lock must not be held.
1004 * (3) interrupts must be enabled.
1006 int isolate_lru_page(struct page *page)
1008 int ret = -EBUSY;
1010 if (PageLRU(page)) {
1011 struct zone *zone = page_zone(page);
1013 spin_lock_irq(&zone->lru_lock);
1014 if (PageLRU(page) && get_page_unless_zero(page)) {
1015 int lru = page_lru(page);
1016 ret = 0;
1017 ClearPageLRU(page);
1019 del_page_from_lru_list(zone, page, lru);
1021 spin_unlock_irq(&zone->lru_lock);
1023 return ret;
1027 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1028 * of reclaimed pages
1030 static unsigned long shrink_inactive_list(unsigned long max_scan,
1031 struct zone *zone, struct scan_control *sc,
1032 int priority, int file)
1034 LIST_HEAD(page_list);
1035 struct pagevec pvec;
1036 unsigned long nr_scanned = 0;
1037 unsigned long nr_reclaimed = 0;
1039 pagevec_init(&pvec, 1);
1041 lru_add_drain();
1042 spin_lock_irq(&zone->lru_lock);
1043 do {
1044 struct page *page;
1045 unsigned long nr_taken;
1046 unsigned long nr_scan;
1047 unsigned long nr_freed;
1048 unsigned long nr_active;
1049 unsigned int count[NR_LRU_LISTS] = { 0, };
1050 int mode = ISOLATE_INACTIVE;
1053 * If we need a large contiguous chunk of memory, or have
1054 * trouble getting a small set of contiguous pages, we
1055 * will reclaim both active and inactive pages.
1057 * We use the same threshold as pageout congestion_wait below.
1059 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1060 mode = ISOLATE_BOTH;
1061 else if (sc->order && priority < DEF_PRIORITY - 2)
1062 mode = ISOLATE_BOTH;
1064 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1065 &page_list, &nr_scan, sc->order, mode,
1066 zone, sc->mem_cgroup, 0, file);
1067 nr_active = clear_active_flags(&page_list, count);
1068 __count_vm_events(PGDEACTIVATE, nr_active);
1070 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1071 -count[LRU_ACTIVE_FILE]);
1072 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1073 -count[LRU_INACTIVE_FILE]);
1074 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1075 -count[LRU_ACTIVE_ANON]);
1076 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1077 -count[LRU_INACTIVE_ANON]);
1079 if (scan_global_lru(sc)) {
1080 zone->pages_scanned += nr_scan;
1081 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1082 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1083 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1084 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1086 spin_unlock_irq(&zone->lru_lock);
1088 nr_scanned += nr_scan;
1089 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1092 * If we are direct reclaiming for contiguous pages and we do
1093 * not reclaim everything in the list, try again and wait
1094 * for IO to complete. This will stall high-order allocations
1095 * but that should be acceptable to the caller
1097 if (nr_freed < nr_taken && !current_is_kswapd() &&
1098 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1099 congestion_wait(WRITE, HZ/10);
1102 * The attempt at page out may have made some
1103 * of the pages active, mark them inactive again.
1105 nr_active = clear_active_flags(&page_list, count);
1106 count_vm_events(PGDEACTIVATE, nr_active);
1108 nr_freed += shrink_page_list(&page_list, sc,
1109 PAGEOUT_IO_SYNC);
1112 nr_reclaimed += nr_freed;
1113 local_irq_disable();
1114 if (current_is_kswapd()) {
1115 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1116 __count_vm_events(KSWAPD_STEAL, nr_freed);
1117 } else if (scan_global_lru(sc))
1118 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1120 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1122 if (nr_taken == 0)
1123 goto done;
1125 spin_lock(&zone->lru_lock);
1127 * Put back any unfreeable pages.
1129 while (!list_empty(&page_list)) {
1130 int lru;
1131 page = lru_to_page(&page_list);
1132 VM_BUG_ON(PageLRU(page));
1133 list_del(&page->lru);
1134 if (unlikely(!page_evictable(page, NULL))) {
1135 spin_unlock_irq(&zone->lru_lock);
1136 putback_lru_page(page);
1137 spin_lock_irq(&zone->lru_lock);
1138 continue;
1140 SetPageLRU(page);
1141 lru = page_lru(page);
1142 add_page_to_lru_list(zone, page, lru);
1143 mem_cgroup_move_lists(page, lru);
1144 if (PageActive(page) && scan_global_lru(sc)) {
1145 int file = !!page_is_file_cache(page);
1146 zone->recent_rotated[file]++;
1148 if (!pagevec_add(&pvec, page)) {
1149 spin_unlock_irq(&zone->lru_lock);
1150 __pagevec_release(&pvec);
1151 spin_lock_irq(&zone->lru_lock);
1154 } while (nr_scanned < max_scan);
1155 spin_unlock(&zone->lru_lock);
1156 done:
1157 local_irq_enable();
1158 pagevec_release(&pvec);
1159 return nr_reclaimed;
1163 * We are about to scan this zone at a certain priority level. If that priority
1164 * level is smaller (ie: more urgent) than the previous priority, then note
1165 * that priority level within the zone. This is done so that when the next
1166 * process comes in to scan this zone, it will immediately start out at this
1167 * priority level rather than having to build up its own scanning priority.
1168 * Here, this priority affects only the reclaim-mapped threshold.
1170 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1172 if (priority < zone->prev_priority)
1173 zone->prev_priority = priority;
1176 static inline int zone_is_near_oom(struct zone *zone)
1178 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
1182 * This moves pages from the active list to the inactive list.
1184 * We move them the other way if the page is referenced by one or more
1185 * processes, from rmap.
1187 * If the pages are mostly unmapped, the processing is fast and it is
1188 * appropriate to hold zone->lru_lock across the whole operation. But if
1189 * the pages are mapped, the processing is slow (page_referenced()) so we
1190 * should drop zone->lru_lock around each page. It's impossible to balance
1191 * this, so instead we remove the pages from the LRU while processing them.
1192 * It is safe to rely on PG_active against the non-LRU pages in here because
1193 * nobody will play with that bit on a non-LRU page.
1195 * The downside is that we have to touch page->_count against each page.
1196 * But we had to alter page->flags anyway.
1200 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1201 struct scan_control *sc, int priority, int file)
1203 unsigned long pgmoved;
1204 int pgdeactivate = 0;
1205 unsigned long pgscanned;
1206 LIST_HEAD(l_hold); /* The pages which were snipped off */
1207 LIST_HEAD(l_inactive);
1208 struct page *page;
1209 struct pagevec pvec;
1210 enum lru_list lru;
1212 lru_add_drain();
1213 spin_lock_irq(&zone->lru_lock);
1214 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1215 ISOLATE_ACTIVE, zone,
1216 sc->mem_cgroup, 1, file);
1218 * zone->pages_scanned is used for detect zone's oom
1219 * mem_cgroup remembers nr_scan by itself.
1221 if (scan_global_lru(sc)) {
1222 zone->pages_scanned += pgscanned;
1223 zone->recent_scanned[!!file] += pgmoved;
1226 if (file)
1227 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1228 else
1229 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1230 spin_unlock_irq(&zone->lru_lock);
1232 pgmoved = 0;
1233 while (!list_empty(&l_hold)) {
1234 cond_resched();
1235 page = lru_to_page(&l_hold);
1236 list_del(&page->lru);
1238 if (unlikely(!page_evictable(page, NULL))) {
1239 putback_lru_page(page);
1240 continue;
1243 /* page_referenced clears PageReferenced */
1244 if (page_mapping_inuse(page) &&
1245 page_referenced(page, 0, sc->mem_cgroup))
1246 pgmoved++;
1248 list_add(&page->lru, &l_inactive);
1251 spin_lock_irq(&zone->lru_lock);
1253 * Count referenced pages from currently used mappings as
1254 * rotated, even though they are moved to the inactive list.
1255 * This helps balance scan pressure between file and anonymous
1256 * pages in get_scan_ratio.
1258 zone->recent_rotated[!!file] += pgmoved;
1261 * Move the pages to the [file or anon] inactive list.
1263 pagevec_init(&pvec, 1);
1265 pgmoved = 0;
1266 lru = LRU_BASE + file * LRU_FILE;
1267 while (!list_empty(&l_inactive)) {
1268 page = lru_to_page(&l_inactive);
1269 prefetchw_prev_lru_page(page, &l_inactive, flags);
1270 VM_BUG_ON(PageLRU(page));
1271 SetPageLRU(page);
1272 VM_BUG_ON(!PageActive(page));
1273 ClearPageActive(page);
1275 list_move(&page->lru, &zone->lru[lru].list);
1276 mem_cgroup_move_lists(page, lru);
1277 pgmoved++;
1278 if (!pagevec_add(&pvec, page)) {
1279 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1280 spin_unlock_irq(&zone->lru_lock);
1281 pgdeactivate += pgmoved;
1282 pgmoved = 0;
1283 if (buffer_heads_over_limit)
1284 pagevec_strip(&pvec);
1285 __pagevec_release(&pvec);
1286 spin_lock_irq(&zone->lru_lock);
1289 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1290 pgdeactivate += pgmoved;
1291 if (buffer_heads_over_limit) {
1292 spin_unlock_irq(&zone->lru_lock);
1293 pagevec_strip(&pvec);
1294 spin_lock_irq(&zone->lru_lock);
1296 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1297 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1298 spin_unlock_irq(&zone->lru_lock);
1299 if (vm_swap_full())
1300 pagevec_swap_free(&pvec);
1302 pagevec_release(&pvec);
1305 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1306 struct zone *zone, struct scan_control *sc, int priority)
1308 int file = is_file_lru(lru);
1310 if (lru == LRU_ACTIVE_FILE) {
1311 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1312 return 0;
1315 if (lru == LRU_ACTIVE_ANON &&
1316 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1317 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1318 return 0;
1320 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1324 * Determine how aggressively the anon and file LRU lists should be
1325 * scanned. The relative value of each set of LRU lists is determined
1326 * by looking at the fraction of the pages scanned we did rotate back
1327 * onto the active list instead of evict.
1329 * percent[0] specifies how much pressure to put on ram/swap backed
1330 * memory, while percent[1] determines pressure on the file LRUs.
1332 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1333 unsigned long *percent)
1335 unsigned long anon, file, free;
1336 unsigned long anon_prio, file_prio;
1337 unsigned long ap, fp;
1339 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1340 zone_page_state(zone, NR_INACTIVE_ANON);
1341 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1342 zone_page_state(zone, NR_INACTIVE_FILE);
1343 free = zone_page_state(zone, NR_FREE_PAGES);
1345 /* If we have no swap space, do not bother scanning anon pages. */
1346 if (nr_swap_pages <= 0) {
1347 percent[0] = 0;
1348 percent[1] = 100;
1349 return;
1352 /* If we have very few page cache pages, force-scan anon pages. */
1353 if (unlikely(file + free <= zone->pages_high)) {
1354 percent[0] = 100;
1355 percent[1] = 0;
1356 return;
1360 * OK, so we have swap space and a fair amount of page cache
1361 * pages. We use the recently rotated / recently scanned
1362 * ratios to determine how valuable each cache is.
1364 * Because workloads change over time (and to avoid overflow)
1365 * we keep these statistics as a floating average, which ends
1366 * up weighing recent references more than old ones.
1368 * anon in [0], file in [1]
1370 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1371 spin_lock_irq(&zone->lru_lock);
1372 zone->recent_scanned[0] /= 2;
1373 zone->recent_rotated[0] /= 2;
1374 spin_unlock_irq(&zone->lru_lock);
1377 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1378 spin_lock_irq(&zone->lru_lock);
1379 zone->recent_scanned[1] /= 2;
1380 zone->recent_rotated[1] /= 2;
1381 spin_unlock_irq(&zone->lru_lock);
1385 * With swappiness at 100, anonymous and file have the same priority.
1386 * This scanning priority is essentially the inverse of IO cost.
1388 anon_prio = sc->swappiness;
1389 file_prio = 200 - sc->swappiness;
1392 * The amount of pressure on anon vs file pages is inversely
1393 * proportional to the fraction of recently scanned pages on
1394 * each list that were recently referenced and in active use.
1396 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1397 ap /= zone->recent_rotated[0] + 1;
1399 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1400 fp /= zone->recent_rotated[1] + 1;
1402 /* Normalize to percentages */
1403 percent[0] = 100 * ap / (ap + fp + 1);
1404 percent[1] = 100 - percent[0];
1409 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1411 static unsigned long shrink_zone(int priority, struct zone *zone,
1412 struct scan_control *sc)
1414 unsigned long nr[NR_LRU_LISTS];
1415 unsigned long nr_to_scan;
1416 unsigned long nr_reclaimed = 0;
1417 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1418 enum lru_list l;
1420 get_scan_ratio(zone, sc, percent);
1422 for_each_evictable_lru(l) {
1423 if (scan_global_lru(sc)) {
1424 int file = is_file_lru(l);
1425 int scan;
1427 scan = zone_page_state(zone, NR_LRU_BASE + l);
1428 if (priority) {
1429 scan >>= priority;
1430 scan = (scan * percent[file]) / 100;
1432 zone->lru[l].nr_scan += scan;
1433 nr[l] = zone->lru[l].nr_scan;
1434 if (nr[l] >= sc->swap_cluster_max)
1435 zone->lru[l].nr_scan = 0;
1436 else
1437 nr[l] = 0;
1438 } else {
1440 * This reclaim occurs not because zone memory shortage
1441 * but because memory controller hits its limit.
1442 * Don't modify zone reclaim related data.
1444 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1445 priority, l);
1449 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1450 nr[LRU_INACTIVE_FILE]) {
1451 for_each_evictable_lru(l) {
1452 if (nr[l]) {
1453 nr_to_scan = min(nr[l],
1454 (unsigned long)sc->swap_cluster_max);
1455 nr[l] -= nr_to_scan;
1457 nr_reclaimed += shrink_list(l, nr_to_scan,
1458 zone, sc, priority);
1464 * Even if we did not try to evict anon pages at all, we want to
1465 * rebalance the anon lru active/inactive ratio.
1467 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1468 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1469 else if (!scan_global_lru(sc))
1470 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1472 throttle_vm_writeout(sc->gfp_mask);
1473 return nr_reclaimed;
1477 * This is the direct reclaim path, for page-allocating processes. We only
1478 * try to reclaim pages from zones which will satisfy the caller's allocation
1479 * request.
1481 * We reclaim from a zone even if that zone is over pages_high. Because:
1482 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1483 * allocation or
1484 * b) The zones may be over pages_high but they must go *over* pages_high to
1485 * satisfy the `incremental min' zone defense algorithm.
1487 * Returns the number of reclaimed pages.
1489 * If a zone is deemed to be full of pinned pages then just give it a light
1490 * scan then give up on it.
1492 static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1493 struct scan_control *sc)
1495 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1496 unsigned long nr_reclaimed = 0;
1497 struct zoneref *z;
1498 struct zone *zone;
1500 sc->all_unreclaimable = 1;
1501 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1502 if (!populated_zone(zone))
1503 continue;
1505 * Take care memory controller reclaiming has small influence
1506 * to global LRU.
1508 if (scan_global_lru(sc)) {
1509 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1510 continue;
1511 note_zone_scanning_priority(zone, priority);
1513 if (zone_is_all_unreclaimable(zone) &&
1514 priority != DEF_PRIORITY)
1515 continue; /* Let kswapd poll it */
1516 sc->all_unreclaimable = 0;
1517 } else {
1519 * Ignore cpuset limitation here. We just want to reduce
1520 * # of used pages by us regardless of memory shortage.
1522 sc->all_unreclaimable = 0;
1523 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1524 priority);
1527 nr_reclaimed += shrink_zone(priority, zone, sc);
1530 return nr_reclaimed;
1534 * This is the main entry point to direct page reclaim.
1536 * If a full scan of the inactive list fails to free enough memory then we
1537 * are "out of memory" and something needs to be killed.
1539 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1540 * high - the zone may be full of dirty or under-writeback pages, which this
1541 * caller can't do much about. We kick pdflush and take explicit naps in the
1542 * hope that some of these pages can be written. But if the allocating task
1543 * holds filesystem locks which prevent writeout this might not work, and the
1544 * allocation attempt will fail.
1546 * returns: 0, if no pages reclaimed
1547 * else, the number of pages reclaimed
1549 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1550 struct scan_control *sc)
1552 int priority;
1553 unsigned long ret = 0;
1554 unsigned long total_scanned = 0;
1555 unsigned long nr_reclaimed = 0;
1556 struct reclaim_state *reclaim_state = current->reclaim_state;
1557 unsigned long lru_pages = 0;
1558 struct zoneref *z;
1559 struct zone *zone;
1560 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1562 delayacct_freepages_start();
1564 if (scan_global_lru(sc))
1565 count_vm_event(ALLOCSTALL);
1567 * mem_cgroup will not do shrink_slab.
1569 if (scan_global_lru(sc)) {
1570 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1572 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1573 continue;
1575 lru_pages += zone_lru_pages(zone);
1579 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1580 sc->nr_scanned = 0;
1581 if (!priority)
1582 disable_swap_token();
1583 nr_reclaimed += shrink_zones(priority, zonelist, sc);
1585 * Don't shrink slabs when reclaiming memory from
1586 * over limit cgroups
1588 if (scan_global_lru(sc)) {
1589 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1590 if (reclaim_state) {
1591 nr_reclaimed += reclaim_state->reclaimed_slab;
1592 reclaim_state->reclaimed_slab = 0;
1595 total_scanned += sc->nr_scanned;
1596 if (nr_reclaimed >= sc->swap_cluster_max) {
1597 ret = nr_reclaimed;
1598 goto out;
1602 * Try to write back as many pages as we just scanned. This
1603 * tends to cause slow streaming writers to write data to the
1604 * disk smoothly, at the dirtying rate, which is nice. But
1605 * that's undesirable in laptop mode, where we *want* lumpy
1606 * writeout. So in laptop mode, write out the whole world.
1608 if (total_scanned > sc->swap_cluster_max +
1609 sc->swap_cluster_max / 2) {
1610 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1611 sc->may_writepage = 1;
1614 /* Take a nap, wait for some writeback to complete */
1615 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1616 congestion_wait(WRITE, HZ/10);
1618 /* top priority shrink_zones still had more to do? don't OOM, then */
1619 if (!sc->all_unreclaimable && scan_global_lru(sc))
1620 ret = nr_reclaimed;
1621 out:
1623 * Now that we've scanned all the zones at this priority level, note
1624 * that level within the zone so that the next thread which performs
1625 * scanning of this zone will immediately start out at this priority
1626 * level. This affects only the decision whether or not to bring
1627 * mapped pages onto the inactive list.
1629 if (priority < 0)
1630 priority = 0;
1632 if (scan_global_lru(sc)) {
1633 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1635 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1636 continue;
1638 zone->prev_priority = priority;
1640 } else
1641 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1643 delayacct_freepages_end();
1645 return ret;
1648 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1649 gfp_t gfp_mask)
1651 struct scan_control sc = {
1652 .gfp_mask = gfp_mask,
1653 .may_writepage = !laptop_mode,
1654 .swap_cluster_max = SWAP_CLUSTER_MAX,
1655 .may_swap = 1,
1656 .swappiness = vm_swappiness,
1657 .order = order,
1658 .mem_cgroup = NULL,
1659 .isolate_pages = isolate_pages_global,
1662 return do_try_to_free_pages(zonelist, &sc);
1665 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1667 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1668 gfp_t gfp_mask)
1670 struct scan_control sc = {
1671 .may_writepage = !laptop_mode,
1672 .may_swap = 1,
1673 .swap_cluster_max = SWAP_CLUSTER_MAX,
1674 .swappiness = vm_swappiness,
1675 .order = 0,
1676 .mem_cgroup = mem_cont,
1677 .isolate_pages = mem_cgroup_isolate_pages,
1679 struct zonelist *zonelist;
1681 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1682 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1683 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1684 return do_try_to_free_pages(zonelist, &sc);
1686 #endif
1689 * For kswapd, balance_pgdat() will work across all this node's zones until
1690 * they are all at pages_high.
1692 * Returns the number of pages which were actually freed.
1694 * There is special handling here for zones which are full of pinned pages.
1695 * This can happen if the pages are all mlocked, or if they are all used by
1696 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1697 * What we do is to detect the case where all pages in the zone have been
1698 * scanned twice and there has been zero successful reclaim. Mark the zone as
1699 * dead and from now on, only perform a short scan. Basically we're polling
1700 * the zone for when the problem goes away.
1702 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1703 * zones which have free_pages > pages_high, but once a zone is found to have
1704 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1705 * of the number of free pages in the lower zones. This interoperates with
1706 * the page allocator fallback scheme to ensure that aging of pages is balanced
1707 * across the zones.
1709 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1711 int all_zones_ok;
1712 int priority;
1713 int i;
1714 unsigned long total_scanned;
1715 unsigned long nr_reclaimed;
1716 struct reclaim_state *reclaim_state = current->reclaim_state;
1717 struct scan_control sc = {
1718 .gfp_mask = GFP_KERNEL,
1719 .may_swap = 1,
1720 .swap_cluster_max = SWAP_CLUSTER_MAX,
1721 .swappiness = vm_swappiness,
1722 .order = order,
1723 .mem_cgroup = NULL,
1724 .isolate_pages = isolate_pages_global,
1727 * temp_priority is used to remember the scanning priority at which
1728 * this zone was successfully refilled to free_pages == pages_high.
1730 int temp_priority[MAX_NR_ZONES];
1732 loop_again:
1733 total_scanned = 0;
1734 nr_reclaimed = 0;
1735 sc.may_writepage = !laptop_mode;
1736 count_vm_event(PAGEOUTRUN);
1738 for (i = 0; i < pgdat->nr_zones; i++)
1739 temp_priority[i] = DEF_PRIORITY;
1741 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1742 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1743 unsigned long lru_pages = 0;
1745 /* The swap token gets in the way of swapout... */
1746 if (!priority)
1747 disable_swap_token();
1749 all_zones_ok = 1;
1752 * Scan in the highmem->dma direction for the highest
1753 * zone which needs scanning
1755 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1756 struct zone *zone = pgdat->node_zones + i;
1758 if (!populated_zone(zone))
1759 continue;
1761 if (zone_is_all_unreclaimable(zone) &&
1762 priority != DEF_PRIORITY)
1763 continue;
1766 * Do some background aging of the anon list, to give
1767 * pages a chance to be referenced before reclaiming.
1769 if (inactive_anon_is_low(zone))
1770 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1771 &sc, priority, 0);
1773 if (!zone_watermark_ok(zone, order, zone->pages_high,
1774 0, 0)) {
1775 end_zone = i;
1776 break;
1779 if (i < 0)
1780 goto out;
1782 for (i = 0; i <= end_zone; i++) {
1783 struct zone *zone = pgdat->node_zones + i;
1785 lru_pages += zone_lru_pages(zone);
1789 * Now scan the zone in the dma->highmem direction, stopping
1790 * at the last zone which needs scanning.
1792 * We do this because the page allocator works in the opposite
1793 * direction. This prevents the page allocator from allocating
1794 * pages behind kswapd's direction of progress, which would
1795 * cause too much scanning of the lower zones.
1797 for (i = 0; i <= end_zone; i++) {
1798 struct zone *zone = pgdat->node_zones + i;
1799 int nr_slab;
1801 if (!populated_zone(zone))
1802 continue;
1804 if (zone_is_all_unreclaimable(zone) &&
1805 priority != DEF_PRIORITY)
1806 continue;
1808 if (!zone_watermark_ok(zone, order, zone->pages_high,
1809 end_zone, 0))
1810 all_zones_ok = 0;
1811 temp_priority[i] = priority;
1812 sc.nr_scanned = 0;
1813 note_zone_scanning_priority(zone, priority);
1815 * We put equal pressure on every zone, unless one
1816 * zone has way too many pages free already.
1818 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1819 end_zone, 0))
1820 nr_reclaimed += shrink_zone(priority, zone, &sc);
1821 reclaim_state->reclaimed_slab = 0;
1822 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1823 lru_pages);
1824 nr_reclaimed += reclaim_state->reclaimed_slab;
1825 total_scanned += sc.nr_scanned;
1826 if (zone_is_all_unreclaimable(zone))
1827 continue;
1828 if (nr_slab == 0 && zone->pages_scanned >=
1829 (zone_lru_pages(zone) * 6))
1830 zone_set_flag(zone,
1831 ZONE_ALL_UNRECLAIMABLE);
1833 * If we've done a decent amount of scanning and
1834 * the reclaim ratio is low, start doing writepage
1835 * even in laptop mode
1837 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1838 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1839 sc.may_writepage = 1;
1841 if (all_zones_ok)
1842 break; /* kswapd: all done */
1844 * OK, kswapd is getting into trouble. Take a nap, then take
1845 * another pass across the zones.
1847 if (total_scanned && priority < DEF_PRIORITY - 2)
1848 congestion_wait(WRITE, HZ/10);
1851 * We do this so kswapd doesn't build up large priorities for
1852 * example when it is freeing in parallel with allocators. It
1853 * matches the direct reclaim path behaviour in terms of impact
1854 * on zone->*_priority.
1856 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1857 break;
1859 out:
1861 * Note within each zone the priority level at which this zone was
1862 * brought into a happy state. So that the next thread which scans this
1863 * zone will start out at that priority level.
1865 for (i = 0; i < pgdat->nr_zones; i++) {
1866 struct zone *zone = pgdat->node_zones + i;
1868 zone->prev_priority = temp_priority[i];
1870 if (!all_zones_ok) {
1871 cond_resched();
1873 try_to_freeze();
1875 goto loop_again;
1878 return nr_reclaimed;
1882 * The background pageout daemon, started as a kernel thread
1883 * from the init process.
1885 * This basically trickles out pages so that we have _some_
1886 * free memory available even if there is no other activity
1887 * that frees anything up. This is needed for things like routing
1888 * etc, where we otherwise might have all activity going on in
1889 * asynchronous contexts that cannot page things out.
1891 * If there are applications that are active memory-allocators
1892 * (most normal use), this basically shouldn't matter.
1894 static int kswapd(void *p)
1896 unsigned long order;
1897 pg_data_t *pgdat = (pg_data_t*)p;
1898 struct task_struct *tsk = current;
1899 DEFINE_WAIT(wait);
1900 struct reclaim_state reclaim_state = {
1901 .reclaimed_slab = 0,
1903 node_to_cpumask_ptr(cpumask, pgdat->node_id);
1905 if (!cpumask_empty(cpumask))
1906 set_cpus_allowed_ptr(tsk, cpumask);
1907 current->reclaim_state = &reclaim_state;
1910 * Tell the memory management that we're a "memory allocator",
1911 * and that if we need more memory we should get access to it
1912 * regardless (see "__alloc_pages()"). "kswapd" should
1913 * never get caught in the normal page freeing logic.
1915 * (Kswapd normally doesn't need memory anyway, but sometimes
1916 * you need a small amount of memory in order to be able to
1917 * page out something else, and this flag essentially protects
1918 * us from recursively trying to free more memory as we're
1919 * trying to free the first piece of memory in the first place).
1921 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1922 set_freezable();
1924 order = 0;
1925 for ( ; ; ) {
1926 unsigned long new_order;
1928 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1929 new_order = pgdat->kswapd_max_order;
1930 pgdat->kswapd_max_order = 0;
1931 if (order < new_order) {
1933 * Don't sleep if someone wants a larger 'order'
1934 * allocation
1936 order = new_order;
1937 } else {
1938 if (!freezing(current))
1939 schedule();
1941 order = pgdat->kswapd_max_order;
1943 finish_wait(&pgdat->kswapd_wait, &wait);
1945 if (!try_to_freeze()) {
1946 /* We can speed up thawing tasks if we don't call
1947 * balance_pgdat after returning from the refrigerator
1949 balance_pgdat(pgdat, order);
1952 return 0;
1956 * A zone is low on free memory, so wake its kswapd task to service it.
1958 void wakeup_kswapd(struct zone *zone, int order)
1960 pg_data_t *pgdat;
1962 if (!populated_zone(zone))
1963 return;
1965 pgdat = zone->zone_pgdat;
1966 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1967 return;
1968 if (pgdat->kswapd_max_order < order)
1969 pgdat->kswapd_max_order = order;
1970 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1971 return;
1972 if (!waitqueue_active(&pgdat->kswapd_wait))
1973 return;
1974 wake_up_interruptible(&pgdat->kswapd_wait);
1977 unsigned long global_lru_pages(void)
1979 return global_page_state(NR_ACTIVE_ANON)
1980 + global_page_state(NR_ACTIVE_FILE)
1981 + global_page_state(NR_INACTIVE_ANON)
1982 + global_page_state(NR_INACTIVE_FILE);
1985 #ifdef CONFIG_PM
1987 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1988 * from LRU lists system-wide, for given pass and priority, and returns the
1989 * number of reclaimed pages
1991 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1993 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1994 int pass, struct scan_control *sc)
1996 struct zone *zone;
1997 unsigned long nr_to_scan, ret = 0;
1998 enum lru_list l;
2000 for_each_zone(zone) {
2002 if (!populated_zone(zone))
2003 continue;
2005 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2006 continue;
2008 for_each_evictable_lru(l) {
2009 /* For pass = 0, we don't shrink the active list */
2010 if (pass == 0 &&
2011 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2012 continue;
2014 zone->lru[l].nr_scan +=
2015 (zone_page_state(zone, NR_LRU_BASE + l)
2016 >> prio) + 1;
2017 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2018 zone->lru[l].nr_scan = 0;
2019 nr_to_scan = min(nr_pages,
2020 zone_page_state(zone,
2021 NR_LRU_BASE + l));
2022 ret += shrink_list(l, nr_to_scan, zone,
2023 sc, prio);
2024 if (ret >= nr_pages)
2025 return ret;
2030 return ret;
2034 * Try to free `nr_pages' of memory, system-wide, and return the number of
2035 * freed pages.
2037 * Rather than trying to age LRUs the aim is to preserve the overall
2038 * LRU order by reclaiming preferentially
2039 * inactive > active > active referenced > active mapped
2041 unsigned long shrink_all_memory(unsigned long nr_pages)
2043 unsigned long lru_pages, nr_slab;
2044 unsigned long ret = 0;
2045 int pass;
2046 struct reclaim_state reclaim_state;
2047 struct scan_control sc = {
2048 .gfp_mask = GFP_KERNEL,
2049 .may_swap = 0,
2050 .swap_cluster_max = nr_pages,
2051 .may_writepage = 1,
2052 .swappiness = vm_swappiness,
2053 .isolate_pages = isolate_pages_global,
2056 current->reclaim_state = &reclaim_state;
2058 lru_pages = global_lru_pages();
2059 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2060 /* If slab caches are huge, it's better to hit them first */
2061 while (nr_slab >= lru_pages) {
2062 reclaim_state.reclaimed_slab = 0;
2063 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2064 if (!reclaim_state.reclaimed_slab)
2065 break;
2067 ret += reclaim_state.reclaimed_slab;
2068 if (ret >= nr_pages)
2069 goto out;
2071 nr_slab -= reclaim_state.reclaimed_slab;
2075 * We try to shrink LRUs in 5 passes:
2076 * 0 = Reclaim from inactive_list only
2077 * 1 = Reclaim from active list but don't reclaim mapped
2078 * 2 = 2nd pass of type 1
2079 * 3 = Reclaim mapped (normal reclaim)
2080 * 4 = 2nd pass of type 3
2082 for (pass = 0; pass < 5; pass++) {
2083 int prio;
2085 /* Force reclaiming mapped pages in the passes #3 and #4 */
2086 if (pass > 2) {
2087 sc.may_swap = 1;
2088 sc.swappiness = 100;
2091 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2092 unsigned long nr_to_scan = nr_pages - ret;
2094 sc.nr_scanned = 0;
2095 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2096 if (ret >= nr_pages)
2097 goto out;
2099 reclaim_state.reclaimed_slab = 0;
2100 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2101 global_lru_pages());
2102 ret += reclaim_state.reclaimed_slab;
2103 if (ret >= nr_pages)
2104 goto out;
2106 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2107 congestion_wait(WRITE, HZ / 10);
2112 * If ret = 0, we could not shrink LRUs, but there may be something
2113 * in slab caches
2115 if (!ret) {
2116 do {
2117 reclaim_state.reclaimed_slab = 0;
2118 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2119 ret += reclaim_state.reclaimed_slab;
2120 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2123 out:
2124 current->reclaim_state = NULL;
2126 return ret;
2128 #endif
2130 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2131 not required for correctness. So if the last cpu in a node goes
2132 away, we get changed to run anywhere: as the first one comes back,
2133 restore their cpu bindings. */
2134 static int __devinit cpu_callback(struct notifier_block *nfb,
2135 unsigned long action, void *hcpu)
2137 int nid;
2139 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2140 for_each_node_state(nid, N_HIGH_MEMORY) {
2141 pg_data_t *pgdat = NODE_DATA(nid);
2142 node_to_cpumask_ptr(mask, pgdat->node_id);
2144 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2145 /* One of our CPUs online: restore mask */
2146 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2149 return NOTIFY_OK;
2153 * This kswapd start function will be called by init and node-hot-add.
2154 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2156 int kswapd_run(int nid)
2158 pg_data_t *pgdat = NODE_DATA(nid);
2159 int ret = 0;
2161 if (pgdat->kswapd)
2162 return 0;
2164 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2165 if (IS_ERR(pgdat->kswapd)) {
2166 /* failure at boot is fatal */
2167 BUG_ON(system_state == SYSTEM_BOOTING);
2168 printk("Failed to start kswapd on node %d\n",nid);
2169 ret = -1;
2171 return ret;
2174 static int __init kswapd_init(void)
2176 int nid;
2178 swap_setup();
2179 for_each_node_state(nid, N_HIGH_MEMORY)
2180 kswapd_run(nid);
2181 hotcpu_notifier(cpu_callback, 0);
2182 return 0;
2185 module_init(kswapd_init)
2187 #ifdef CONFIG_NUMA
2189 * Zone reclaim mode
2191 * If non-zero call zone_reclaim when the number of free pages falls below
2192 * the watermarks.
2194 int zone_reclaim_mode __read_mostly;
2196 #define RECLAIM_OFF 0
2197 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2198 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2199 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2202 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2203 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2204 * a zone.
2206 #define ZONE_RECLAIM_PRIORITY 4
2209 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2210 * occur.
2212 int sysctl_min_unmapped_ratio = 1;
2215 * If the number of slab pages in a zone grows beyond this percentage then
2216 * slab reclaim needs to occur.
2218 int sysctl_min_slab_ratio = 5;
2221 * Try to free up some pages from this zone through reclaim.
2223 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2225 /* Minimum pages needed in order to stay on node */
2226 const unsigned long nr_pages = 1 << order;
2227 struct task_struct *p = current;
2228 struct reclaim_state reclaim_state;
2229 int priority;
2230 unsigned long nr_reclaimed = 0;
2231 struct scan_control sc = {
2232 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2233 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2234 .swap_cluster_max = max_t(unsigned long, nr_pages,
2235 SWAP_CLUSTER_MAX),
2236 .gfp_mask = gfp_mask,
2237 .swappiness = vm_swappiness,
2238 .isolate_pages = isolate_pages_global,
2240 unsigned long slab_reclaimable;
2242 disable_swap_token();
2243 cond_resched();
2245 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2246 * and we also need to be able to write out pages for RECLAIM_WRITE
2247 * and RECLAIM_SWAP.
2249 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2250 reclaim_state.reclaimed_slab = 0;
2251 p->reclaim_state = &reclaim_state;
2253 if (zone_page_state(zone, NR_FILE_PAGES) -
2254 zone_page_state(zone, NR_FILE_MAPPED) >
2255 zone->min_unmapped_pages) {
2257 * Free memory by calling shrink zone with increasing
2258 * priorities until we have enough memory freed.
2260 priority = ZONE_RECLAIM_PRIORITY;
2261 do {
2262 note_zone_scanning_priority(zone, priority);
2263 nr_reclaimed += shrink_zone(priority, zone, &sc);
2264 priority--;
2265 } while (priority >= 0 && nr_reclaimed < nr_pages);
2268 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2269 if (slab_reclaimable > zone->min_slab_pages) {
2271 * shrink_slab() does not currently allow us to determine how
2272 * many pages were freed in this zone. So we take the current
2273 * number of slab pages and shake the slab until it is reduced
2274 * by the same nr_pages that we used for reclaiming unmapped
2275 * pages.
2277 * Note that shrink_slab will free memory on all zones and may
2278 * take a long time.
2280 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2281 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2282 slab_reclaimable - nr_pages)
2286 * Update nr_reclaimed by the number of slab pages we
2287 * reclaimed from this zone.
2289 nr_reclaimed += slab_reclaimable -
2290 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2293 p->reclaim_state = NULL;
2294 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2295 return nr_reclaimed >= nr_pages;
2298 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2300 int node_id;
2301 int ret;
2304 * Zone reclaim reclaims unmapped file backed pages and
2305 * slab pages if we are over the defined limits.
2307 * A small portion of unmapped file backed pages is needed for
2308 * file I/O otherwise pages read by file I/O will be immediately
2309 * thrown out if the zone is overallocated. So we do not reclaim
2310 * if less than a specified percentage of the zone is used by
2311 * unmapped file backed pages.
2313 if (zone_page_state(zone, NR_FILE_PAGES) -
2314 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2315 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2316 <= zone->min_slab_pages)
2317 return 0;
2319 if (zone_is_all_unreclaimable(zone))
2320 return 0;
2323 * Do not scan if the allocation should not be delayed.
2325 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2326 return 0;
2329 * Only run zone reclaim on the local zone or on zones that do not
2330 * have associated processors. This will favor the local processor
2331 * over remote processors and spread off node memory allocations
2332 * as wide as possible.
2334 node_id = zone_to_nid(zone);
2335 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2336 return 0;
2338 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2339 return 0;
2340 ret = __zone_reclaim(zone, gfp_mask, order);
2341 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2343 return ret;
2345 #endif
2347 #ifdef CONFIG_UNEVICTABLE_LRU
2349 * page_evictable - test whether a page is evictable
2350 * @page: the page to test
2351 * @vma: the VMA in which the page is or will be mapped, may be NULL
2353 * Test whether page is evictable--i.e., should be placed on active/inactive
2354 * lists vs unevictable list. The vma argument is !NULL when called from the
2355 * fault path to determine how to instantate a new page.
2357 * Reasons page might not be evictable:
2358 * (1) page's mapping marked unevictable
2359 * (2) page is part of an mlocked VMA
2362 int page_evictable(struct page *page, struct vm_area_struct *vma)
2365 if (mapping_unevictable(page_mapping(page)))
2366 return 0;
2368 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2369 return 0;
2371 return 1;
2375 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2376 * @page: page to check evictability and move to appropriate lru list
2377 * @zone: zone page is in
2379 * Checks a page for evictability and moves the page to the appropriate
2380 * zone lru list.
2382 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2383 * have PageUnevictable set.
2385 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2387 VM_BUG_ON(PageActive(page));
2389 retry:
2390 ClearPageUnevictable(page);
2391 if (page_evictable(page, NULL)) {
2392 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2394 __dec_zone_state(zone, NR_UNEVICTABLE);
2395 list_move(&page->lru, &zone->lru[l].list);
2396 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2397 __count_vm_event(UNEVICTABLE_PGRESCUED);
2398 } else {
2400 * rotate unevictable list
2402 SetPageUnevictable(page);
2403 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2404 if (page_evictable(page, NULL))
2405 goto retry;
2410 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2411 * @mapping: struct address_space to scan for evictable pages
2413 * Scan all pages in mapping. Check unevictable pages for
2414 * evictability and move them to the appropriate zone lru list.
2416 void scan_mapping_unevictable_pages(struct address_space *mapping)
2418 pgoff_t next = 0;
2419 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2420 PAGE_CACHE_SHIFT;
2421 struct zone *zone;
2422 struct pagevec pvec;
2424 if (mapping->nrpages == 0)
2425 return;
2427 pagevec_init(&pvec, 0);
2428 while (next < end &&
2429 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2430 int i;
2431 int pg_scanned = 0;
2433 zone = NULL;
2435 for (i = 0; i < pagevec_count(&pvec); i++) {
2436 struct page *page = pvec.pages[i];
2437 pgoff_t page_index = page->index;
2438 struct zone *pagezone = page_zone(page);
2440 pg_scanned++;
2441 if (page_index > next)
2442 next = page_index;
2443 next++;
2445 if (pagezone != zone) {
2446 if (zone)
2447 spin_unlock_irq(&zone->lru_lock);
2448 zone = pagezone;
2449 spin_lock_irq(&zone->lru_lock);
2452 if (PageLRU(page) && PageUnevictable(page))
2453 check_move_unevictable_page(page, zone);
2455 if (zone)
2456 spin_unlock_irq(&zone->lru_lock);
2457 pagevec_release(&pvec);
2459 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2465 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2466 * @zone - zone of which to scan the unevictable list
2468 * Scan @zone's unevictable LRU lists to check for pages that have become
2469 * evictable. Move those that have to @zone's inactive list where they
2470 * become candidates for reclaim, unless shrink_inactive_zone() decides
2471 * to reactivate them. Pages that are still unevictable are rotated
2472 * back onto @zone's unevictable list.
2474 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2475 void scan_zone_unevictable_pages(struct zone *zone)
2477 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2478 unsigned long scan;
2479 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2481 while (nr_to_scan > 0) {
2482 unsigned long batch_size = min(nr_to_scan,
2483 SCAN_UNEVICTABLE_BATCH_SIZE);
2485 spin_lock_irq(&zone->lru_lock);
2486 for (scan = 0; scan < batch_size; scan++) {
2487 struct page *page = lru_to_page(l_unevictable);
2489 if (!trylock_page(page))
2490 continue;
2492 prefetchw_prev_lru_page(page, l_unevictable, flags);
2494 if (likely(PageLRU(page) && PageUnevictable(page)))
2495 check_move_unevictable_page(page, zone);
2497 unlock_page(page);
2499 spin_unlock_irq(&zone->lru_lock);
2501 nr_to_scan -= batch_size;
2507 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2509 * A really big hammer: scan all zones' unevictable LRU lists to check for
2510 * pages that have become evictable. Move those back to the zones'
2511 * inactive list where they become candidates for reclaim.
2512 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2513 * and we add swap to the system. As such, it runs in the context of a task
2514 * that has possibly/probably made some previously unevictable pages
2515 * evictable.
2517 void scan_all_zones_unevictable_pages(void)
2519 struct zone *zone;
2521 for_each_zone(zone) {
2522 scan_zone_unevictable_pages(zone);
2527 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2528 * all nodes' unevictable lists for evictable pages
2530 unsigned long scan_unevictable_pages;
2532 int scan_unevictable_handler(struct ctl_table *table, int write,
2533 struct file *file, void __user *buffer,
2534 size_t *length, loff_t *ppos)
2536 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2538 if (write && *(unsigned long *)table->data)
2539 scan_all_zones_unevictable_pages();
2541 scan_unevictable_pages = 0;
2542 return 0;
2546 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2547 * a specified node's per zone unevictable lists for evictable pages.
2550 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2551 struct sysdev_attribute *attr,
2552 char *buf)
2554 return sprintf(buf, "0\n"); /* always zero; should fit... */
2557 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2558 struct sysdev_attribute *attr,
2559 const char *buf, size_t count)
2561 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2562 struct zone *zone;
2563 unsigned long res;
2564 unsigned long req = strict_strtoul(buf, 10, &res);
2566 if (!req)
2567 return 1; /* zero is no-op */
2569 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2570 if (!populated_zone(zone))
2571 continue;
2572 scan_zone_unevictable_pages(zone);
2574 return 1;
2578 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2579 read_scan_unevictable_node,
2580 write_scan_unevictable_node);
2582 int scan_unevictable_register_node(struct node *node)
2584 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2587 void scan_unevictable_unregister_node(struct node *node)
2589 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2592 #endif