Staging: vt6655: Integrate drivers/staging/vt6655 into build system.
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / vmscan.c
blobe8fa2d9eb212d7cfb739f02305a340fbf023565d
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 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
58 /* This context's GFP mask */
59 gfp_t gfp_mask;
61 int may_writepage;
63 /* Can mapped pages be reclaimed? */
64 int may_unmap;
66 /* Can pages be swapped as part of reclaim? */
67 int may_swap;
69 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
70 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
71 * In this context, it doesn't matter that we scan the
72 * whole list at once. */
73 int swap_cluster_max;
75 int swappiness;
77 int all_unreclaimable;
79 int order;
81 /* Which cgroup do we reclaim from */
82 struct mem_cgroup *mem_cgroup;
85 * Nodemask of nodes allowed by the caller. If NULL, all nodes
86 * are scanned.
88 nodemask_t *nodemask;
90 /* Pluggable isolate pages callback */
91 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
92 unsigned long *scanned, int order, int mode,
93 struct zone *z, struct mem_cgroup *mem_cont,
94 int active, int file);
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
101 do { \
102 if ((_page)->lru.prev != _base) { \
103 struct page *prev; \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
108 } while (0)
109 #else
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
111 #endif
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
115 do { \
116 if ((_page)->lru.prev != _base) { \
117 struct page *prev; \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
122 } while (0)
123 #else
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
125 #endif
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness = 60;
131 long vm_total_pages; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list);
134 static DECLARE_RWSEM(shrinker_rwsem);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
138 #else
139 #define scanning_global_lru(sc) (1)
140 #endif
142 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
145 if (!scanning_global_lru(sc))
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
148 return &zone->reclaim_stat;
151 static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc,
152 enum lru_list lru)
154 if (!scanning_global_lru(sc))
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
157 return zone_page_state(zone, NR_LRU_BASE + lru);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker *shrinker)
166 shrinker->nr = 0;
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
171 EXPORT_SYMBOL(register_shrinker);
174 * Remove one
176 void unregister_shrinker(struct shrinker *shrinker)
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
182 EXPORT_SYMBOL(unregister_shrinker);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
207 struct shrinker *shrinker;
208 unsigned long ret = 0;
210 if (scanned == 0)
211 scanned = SWAP_CLUSTER_MAX;
213 if (!down_read_trylock(&shrinker_rwsem))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
219 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
221 delta = (4 * scanned) / shrinker->seeks;
222 delta *= max_pass;
223 do_div(delta, lru_pages + 1);
224 shrinker->nr += delta;
225 if (shrinker->nr < 0) {
226 printk(KERN_ERR "shrink_slab: %pF negative objects to "
227 "delete nr=%ld\n",
228 shrinker->shrink, shrinker->nr);
229 shrinker->nr = max_pass;
233 * Avoid risking looping forever due to too large nr value:
234 * never try to free more than twice the estimate number of
235 * freeable entries.
237 if (shrinker->nr > max_pass * 2)
238 shrinker->nr = max_pass * 2;
240 total_scan = shrinker->nr;
241 shrinker->nr = 0;
243 while (total_scan >= SHRINK_BATCH) {
244 long this_scan = SHRINK_BATCH;
245 int shrink_ret;
246 int nr_before;
248 nr_before = (*shrinker->shrink)(0, gfp_mask);
249 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
250 if (shrink_ret == -1)
251 break;
252 if (shrink_ret < nr_before)
253 ret += nr_before - shrink_ret;
254 count_vm_events(SLABS_SCANNED, this_scan);
255 total_scan -= this_scan;
257 cond_resched();
260 shrinker->nr += total_scan;
262 up_read(&shrinker_rwsem);
263 return ret;
266 /* Called without lock on whether page is mapped, so answer is unstable */
267 static inline int page_mapping_inuse(struct page *page)
269 struct address_space *mapping;
271 /* Page is in somebody's page tables. */
272 if (page_mapped(page))
273 return 1;
275 /* Be more reluctant to reclaim swapcache than pagecache */
276 if (PageSwapCache(page))
277 return 1;
279 mapping = page_mapping(page);
280 if (!mapping)
281 return 0;
283 /* File is mmap'd by somebody? */
284 return mapping_mapped(mapping);
287 static inline int is_page_cache_freeable(struct page *page)
289 return page_count(page) - !!page_has_private(page) == 2;
292 static int may_write_to_queue(struct backing_dev_info *bdi)
294 if (current->flags & PF_SWAPWRITE)
295 return 1;
296 if (!bdi_write_congested(bdi))
297 return 1;
298 if (bdi == current->backing_dev_info)
299 return 1;
300 return 0;
304 * We detected a synchronous write error writing a page out. Probably
305 * -ENOSPC. We need to propagate that into the address_space for a subsequent
306 * fsync(), msync() or close().
308 * The tricky part is that after writepage we cannot touch the mapping: nothing
309 * prevents it from being freed up. But we have a ref on the page and once
310 * that page is locked, the mapping is pinned.
312 * We're allowed to run sleeping lock_page() here because we know the caller has
313 * __GFP_FS.
315 static void handle_write_error(struct address_space *mapping,
316 struct page *page, int error)
318 lock_page(page);
319 if (page_mapping(page) == mapping)
320 mapping_set_error(mapping, error);
321 unlock_page(page);
324 /* Request for sync pageout. */
325 enum pageout_io {
326 PAGEOUT_IO_ASYNC,
327 PAGEOUT_IO_SYNC,
330 /* possible outcome of pageout() */
331 typedef enum {
332 /* failed to write page out, page is locked */
333 PAGE_KEEP,
334 /* move page to the active list, page is locked */
335 PAGE_ACTIVATE,
336 /* page has been sent to the disk successfully, page is unlocked */
337 PAGE_SUCCESS,
338 /* page is clean and locked */
339 PAGE_CLEAN,
340 } pageout_t;
343 * pageout is called by shrink_page_list() for each dirty page.
344 * Calls ->writepage().
346 static pageout_t pageout(struct page *page, struct address_space *mapping,
347 enum pageout_io sync_writeback)
350 * If the page is dirty, only perform writeback if that write
351 * will be non-blocking. To prevent this allocation from being
352 * stalled by pagecache activity. But note that there may be
353 * stalls if we need to run get_block(). We could test
354 * PagePrivate for that.
356 * If this process is currently in generic_file_write() against
357 * this page's queue, we can perform writeback even if that
358 * will block.
360 * If the page is swapcache, write it back even if that would
361 * block, for some throttling. This happens by accident, because
362 * swap_backing_dev_info is bust: it doesn't reflect the
363 * congestion state of the swapdevs. Easy to fix, if needed.
364 * See swapfile.c:page_queue_congested().
366 if (!is_page_cache_freeable(page))
367 return PAGE_KEEP;
368 if (!mapping) {
370 * Some data journaling orphaned pages can have
371 * page->mapping == NULL while being dirty with clean buffers.
373 if (page_has_private(page)) {
374 if (try_to_free_buffers(page)) {
375 ClearPageDirty(page);
376 printk("%s: orphaned page\n", __func__);
377 return PAGE_CLEAN;
380 return PAGE_KEEP;
382 if (mapping->a_ops->writepage == NULL)
383 return PAGE_ACTIVATE;
384 if (!may_write_to_queue(mapping->backing_dev_info))
385 return PAGE_KEEP;
387 if (clear_page_dirty_for_io(page)) {
388 int res;
389 struct writeback_control wbc = {
390 .sync_mode = WB_SYNC_NONE,
391 .nr_to_write = SWAP_CLUSTER_MAX,
392 .range_start = 0,
393 .range_end = LLONG_MAX,
394 .nonblocking = 1,
395 .for_reclaim = 1,
398 SetPageReclaim(page);
399 res = mapping->a_ops->writepage(page, &wbc);
400 if (res < 0)
401 handle_write_error(mapping, page, res);
402 if (res == AOP_WRITEPAGE_ACTIVATE) {
403 ClearPageReclaim(page);
404 return PAGE_ACTIVATE;
408 * Wait on writeback if requested to. This happens when
409 * direct reclaiming a large contiguous area and the
410 * first attempt to free a range of pages fails.
412 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
413 wait_on_page_writeback(page);
415 if (!PageWriteback(page)) {
416 /* synchronous write or broken a_ops? */
417 ClearPageReclaim(page);
419 inc_zone_page_state(page, NR_VMSCAN_WRITE);
420 return PAGE_SUCCESS;
423 return PAGE_CLEAN;
427 * Same as remove_mapping, but if the page is removed from the mapping, it
428 * gets returned with a refcount of 0.
430 static int __remove_mapping(struct address_space *mapping, struct page *page)
432 BUG_ON(!PageLocked(page));
433 BUG_ON(mapping != page_mapping(page));
435 spin_lock_irq(&mapping->tree_lock);
437 * The non racy check for a busy page.
439 * Must be careful with the order of the tests. When someone has
440 * a ref to the page, it may be possible that they dirty it then
441 * drop the reference. So if PageDirty is tested before page_count
442 * here, then the following race may occur:
444 * get_user_pages(&page);
445 * [user mapping goes away]
446 * write_to(page);
447 * !PageDirty(page) [good]
448 * SetPageDirty(page);
449 * put_page(page);
450 * !page_count(page) [good, discard it]
452 * [oops, our write_to data is lost]
454 * Reversing the order of the tests ensures such a situation cannot
455 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
456 * load is not satisfied before that of page->_count.
458 * Note that if SetPageDirty is always performed via set_page_dirty,
459 * and thus under tree_lock, then this ordering is not required.
461 if (!page_freeze_refs(page, 2))
462 goto cannot_free;
463 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
464 if (unlikely(PageDirty(page))) {
465 page_unfreeze_refs(page, 2);
466 goto cannot_free;
469 if (PageSwapCache(page)) {
470 swp_entry_t swap = { .val = page_private(page) };
471 __delete_from_swap_cache(page);
472 spin_unlock_irq(&mapping->tree_lock);
473 swapcache_free(swap, page);
474 } else {
475 __remove_from_page_cache(page);
476 spin_unlock_irq(&mapping->tree_lock);
477 mem_cgroup_uncharge_cache_page(page);
480 return 1;
482 cannot_free:
483 spin_unlock_irq(&mapping->tree_lock);
484 return 0;
488 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
489 * someone else has a ref on the page, abort and return 0. If it was
490 * successfully detached, return 1. Assumes the caller has a single ref on
491 * this page.
493 int remove_mapping(struct address_space *mapping, struct page *page)
495 if (__remove_mapping(mapping, page)) {
497 * Unfreezing the refcount with 1 rather than 2 effectively
498 * drops the pagecache ref for us without requiring another
499 * atomic operation.
501 page_unfreeze_refs(page, 1);
502 return 1;
504 return 0;
508 * putback_lru_page - put previously isolated page onto appropriate LRU list
509 * @page: page to be put back to appropriate lru list
511 * Add previously isolated @page to appropriate LRU list.
512 * Page may still be unevictable for other reasons.
514 * lru_lock must not be held, interrupts must be enabled.
516 void putback_lru_page(struct page *page)
518 int lru;
519 int active = !!TestClearPageActive(page);
520 int was_unevictable = PageUnevictable(page);
522 VM_BUG_ON(PageLRU(page));
524 redo:
525 ClearPageUnevictable(page);
527 if (page_evictable(page, NULL)) {
529 * For evictable pages, we can use the cache.
530 * In event of a race, worst case is we end up with an
531 * unevictable page on [in]active list.
532 * We know how to handle that.
534 lru = active + page_is_file_cache(page);
535 lru_cache_add_lru(page, lru);
536 } else {
538 * Put unevictable pages directly on zone's unevictable
539 * list.
541 lru = LRU_UNEVICTABLE;
542 add_page_to_unevictable_list(page);
546 * page's status can change while we move it among lru. If an evictable
547 * page is on unevictable list, it never be freed. To avoid that,
548 * check after we added it to the list, again.
550 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
551 if (!isolate_lru_page(page)) {
552 put_page(page);
553 goto redo;
555 /* This means someone else dropped this page from LRU
556 * So, it will be freed or putback to LRU again. There is
557 * nothing to do here.
561 if (was_unevictable && lru != LRU_UNEVICTABLE)
562 count_vm_event(UNEVICTABLE_PGRESCUED);
563 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
564 count_vm_event(UNEVICTABLE_PGCULLED);
566 put_page(page); /* drop ref from isolate */
570 * shrink_page_list() returns the number of reclaimed pages
572 static unsigned long shrink_page_list(struct list_head *page_list,
573 struct scan_control *sc,
574 enum pageout_io sync_writeback)
576 LIST_HEAD(ret_pages);
577 struct pagevec freed_pvec;
578 int pgactivate = 0;
579 unsigned long nr_reclaimed = 0;
580 unsigned long vm_flags;
582 cond_resched();
584 pagevec_init(&freed_pvec, 1);
585 while (!list_empty(page_list)) {
586 struct address_space *mapping;
587 struct page *page;
588 int may_enter_fs;
589 int referenced;
591 cond_resched();
593 page = lru_to_page(page_list);
594 list_del(&page->lru);
596 if (!trylock_page(page))
597 goto keep;
599 VM_BUG_ON(PageActive(page));
601 sc->nr_scanned++;
603 if (unlikely(!page_evictable(page, NULL)))
604 goto cull_mlocked;
606 if (!sc->may_unmap && page_mapped(page))
607 goto keep_locked;
609 /* Double the slab pressure for mapped and swapcache pages */
610 if (page_mapped(page) || PageSwapCache(page))
611 sc->nr_scanned++;
613 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
614 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
616 if (PageWriteback(page)) {
618 * Synchronous reclaim is performed in two passes,
619 * first an asynchronous pass over the list to
620 * start parallel writeback, and a second synchronous
621 * pass to wait for the IO to complete. Wait here
622 * for any page for which writeback has already
623 * started.
625 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
626 wait_on_page_writeback(page);
627 else
628 goto keep_locked;
631 referenced = page_referenced(page, 1,
632 sc->mem_cgroup, &vm_flags);
633 /* In active use or really unfreeable? Activate it. */
634 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
635 referenced && page_mapping_inuse(page))
636 goto activate_locked;
639 * Anonymous process memory has backing store?
640 * Try to allocate it some swap space here.
642 if (PageAnon(page) && !PageSwapCache(page)) {
643 if (!(sc->gfp_mask & __GFP_IO))
644 goto keep_locked;
645 if (!add_to_swap(page))
646 goto activate_locked;
647 may_enter_fs = 1;
650 mapping = page_mapping(page);
653 * The page is mapped into the page tables of one or more
654 * processes. Try to unmap it here.
656 if (page_mapped(page) && mapping) {
657 switch (try_to_unmap(page, 0)) {
658 case SWAP_FAIL:
659 goto activate_locked;
660 case SWAP_AGAIN:
661 goto keep_locked;
662 case SWAP_MLOCK:
663 goto cull_mlocked;
664 case SWAP_SUCCESS:
665 ; /* try to free the page below */
669 if (PageDirty(page)) {
670 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
671 goto keep_locked;
672 if (!may_enter_fs)
673 goto keep_locked;
674 if (!sc->may_writepage)
675 goto keep_locked;
677 /* Page is dirty, try to write it out here */
678 switch (pageout(page, mapping, sync_writeback)) {
679 case PAGE_KEEP:
680 goto keep_locked;
681 case PAGE_ACTIVATE:
682 goto activate_locked;
683 case PAGE_SUCCESS:
684 if (PageWriteback(page) || PageDirty(page))
685 goto keep;
687 * A synchronous write - probably a ramdisk. Go
688 * ahead and try to reclaim the page.
690 if (!trylock_page(page))
691 goto keep;
692 if (PageDirty(page) || PageWriteback(page))
693 goto keep_locked;
694 mapping = page_mapping(page);
695 case PAGE_CLEAN:
696 ; /* try to free the page below */
701 * If the page has buffers, try to free the buffer mappings
702 * associated with this page. If we succeed we try to free
703 * the page as well.
705 * We do this even if the page is PageDirty().
706 * try_to_release_page() does not perform I/O, but it is
707 * possible for a page to have PageDirty set, but it is actually
708 * clean (all its buffers are clean). This happens if the
709 * buffers were written out directly, with submit_bh(). ext3
710 * will do this, as well as the blockdev mapping.
711 * try_to_release_page() will discover that cleanness and will
712 * drop the buffers and mark the page clean - it can be freed.
714 * Rarely, pages can have buffers and no ->mapping. These are
715 * the pages which were not successfully invalidated in
716 * truncate_complete_page(). We try to drop those buffers here
717 * and if that worked, and the page is no longer mapped into
718 * process address space (page_count == 1) it can be freed.
719 * Otherwise, leave the page on the LRU so it is swappable.
721 if (page_has_private(page)) {
722 if (!try_to_release_page(page, sc->gfp_mask))
723 goto activate_locked;
724 if (!mapping && page_count(page) == 1) {
725 unlock_page(page);
726 if (put_page_testzero(page))
727 goto free_it;
728 else {
730 * rare race with speculative reference.
731 * the speculative reference will free
732 * this page shortly, so we may
733 * increment nr_reclaimed here (and
734 * leave it off the LRU).
736 nr_reclaimed++;
737 continue;
742 if (!mapping || !__remove_mapping(mapping, page))
743 goto keep_locked;
746 * At this point, we have no other references and there is
747 * no way to pick any more up (removed from LRU, removed
748 * from pagecache). Can use non-atomic bitops now (and
749 * we obviously don't have to worry about waking up a process
750 * waiting on the page lock, because there are no references.
752 __clear_page_locked(page);
753 free_it:
754 nr_reclaimed++;
755 if (!pagevec_add(&freed_pvec, page)) {
756 __pagevec_free(&freed_pvec);
757 pagevec_reinit(&freed_pvec);
759 continue;
761 cull_mlocked:
762 if (PageSwapCache(page))
763 try_to_free_swap(page);
764 unlock_page(page);
765 putback_lru_page(page);
766 continue;
768 activate_locked:
769 /* Not a candidate for swapping, so reclaim swap space. */
770 if (PageSwapCache(page) && vm_swap_full())
771 try_to_free_swap(page);
772 VM_BUG_ON(PageActive(page));
773 SetPageActive(page);
774 pgactivate++;
775 keep_locked:
776 unlock_page(page);
777 keep:
778 list_add(&page->lru, &ret_pages);
779 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
781 list_splice(&ret_pages, page_list);
782 if (pagevec_count(&freed_pvec))
783 __pagevec_free(&freed_pvec);
784 count_vm_events(PGACTIVATE, pgactivate);
785 return nr_reclaimed;
788 /* LRU Isolation modes. */
789 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
790 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
791 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
794 * Attempt to remove the specified page from its LRU. Only take this page
795 * if it is of the appropriate PageActive status. Pages which are being
796 * freed elsewhere are also ignored.
798 * page: page to consider
799 * mode: one of the LRU isolation modes defined above
801 * returns 0 on success, -ve errno on failure.
803 int __isolate_lru_page(struct page *page, int mode, int file)
805 int ret = -EINVAL;
807 /* Only take pages on the LRU. */
808 if (!PageLRU(page))
809 return ret;
812 * When checking the active state, we need to be sure we are
813 * dealing with comparible boolean values. Take the logical not
814 * of each.
816 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
817 return ret;
819 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
820 return ret;
823 * When this function is being called for lumpy reclaim, we
824 * initially look into all LRU pages, active, inactive and
825 * unevictable; only give shrink_page_list evictable pages.
827 if (PageUnevictable(page))
828 return ret;
830 ret = -EBUSY;
832 if (likely(get_page_unless_zero(page))) {
834 * Be careful not to clear PageLRU until after we're
835 * sure the page is not being freed elsewhere -- the
836 * page release code relies on it.
838 ClearPageLRU(page);
839 ret = 0;
842 return ret;
846 * zone->lru_lock is heavily contended. Some of the functions that
847 * shrink the lists perform better by taking out a batch of pages
848 * and working on them outside the LRU lock.
850 * For pagecache intensive workloads, this function is the hottest
851 * spot in the kernel (apart from copy_*_user functions).
853 * Appropriate locks must be held before calling this function.
855 * @nr_to_scan: The number of pages to look through on the list.
856 * @src: The LRU list to pull pages off.
857 * @dst: The temp list to put pages on to.
858 * @scanned: The number of pages that were scanned.
859 * @order: The caller's attempted allocation order
860 * @mode: One of the LRU isolation modes
861 * @file: True [1] if isolating file [!anon] pages
863 * returns how many pages were moved onto *@dst.
865 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
866 struct list_head *src, struct list_head *dst,
867 unsigned long *scanned, int order, int mode, int file)
869 unsigned long nr_taken = 0;
870 unsigned long scan;
872 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
873 struct page *page;
874 unsigned long pfn;
875 unsigned long end_pfn;
876 unsigned long page_pfn;
877 int zone_id;
879 page = lru_to_page(src);
880 prefetchw_prev_lru_page(page, src, flags);
882 VM_BUG_ON(!PageLRU(page));
884 switch (__isolate_lru_page(page, mode, file)) {
885 case 0:
886 list_move(&page->lru, dst);
887 mem_cgroup_del_lru(page);
888 nr_taken++;
889 break;
891 case -EBUSY:
892 /* else it is being freed elsewhere */
893 list_move(&page->lru, src);
894 mem_cgroup_rotate_lru_list(page, page_lru(page));
895 continue;
897 default:
898 BUG();
901 if (!order)
902 continue;
905 * Attempt to take all pages in the order aligned region
906 * surrounding the tag page. Only take those pages of
907 * the same active state as that tag page. We may safely
908 * round the target page pfn down to the requested order
909 * as the mem_map is guarenteed valid out to MAX_ORDER,
910 * where that page is in a different zone we will detect
911 * it from its zone id and abort this block scan.
913 zone_id = page_zone_id(page);
914 page_pfn = page_to_pfn(page);
915 pfn = page_pfn & ~((1 << order) - 1);
916 end_pfn = pfn + (1 << order);
917 for (; pfn < end_pfn; pfn++) {
918 struct page *cursor_page;
920 /* The target page is in the block, ignore it. */
921 if (unlikely(pfn == page_pfn))
922 continue;
924 /* Avoid holes within the zone. */
925 if (unlikely(!pfn_valid_within(pfn)))
926 break;
928 cursor_page = pfn_to_page(pfn);
930 /* Check that we have not crossed a zone boundary. */
931 if (unlikely(page_zone_id(cursor_page) != zone_id))
932 continue;
933 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
934 list_move(&cursor_page->lru, dst);
935 mem_cgroup_del_lru(page);
936 nr_taken++;
937 scan++;
942 *scanned = scan;
943 return nr_taken;
946 static unsigned long isolate_pages_global(unsigned long nr,
947 struct list_head *dst,
948 unsigned long *scanned, int order,
949 int mode, struct zone *z,
950 struct mem_cgroup *mem_cont,
951 int active, int file)
953 int lru = LRU_BASE;
954 if (active)
955 lru += LRU_ACTIVE;
956 if (file)
957 lru += LRU_FILE;
958 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
959 mode, !!file);
963 * clear_active_flags() is a helper for shrink_active_list(), clearing
964 * any active bits from the pages in the list.
966 static unsigned long clear_active_flags(struct list_head *page_list,
967 unsigned int *count)
969 int nr_active = 0;
970 int lru;
971 struct page *page;
973 list_for_each_entry(page, page_list, lru) {
974 lru = page_is_file_cache(page);
975 if (PageActive(page)) {
976 lru += LRU_ACTIVE;
977 ClearPageActive(page);
978 nr_active++;
980 count[lru]++;
983 return nr_active;
987 * isolate_lru_page - tries to isolate a page from its LRU list
988 * @page: page to isolate from its LRU list
990 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
991 * vmstat statistic corresponding to whatever LRU list the page was on.
993 * Returns 0 if the page was removed from an LRU list.
994 * Returns -EBUSY if the page was not on an LRU list.
996 * The returned page will have PageLRU() cleared. If it was found on
997 * the active list, it will have PageActive set. If it was found on
998 * the unevictable list, it will have the PageUnevictable bit set. That flag
999 * may need to be cleared by the caller before letting the page go.
1001 * The vmstat statistic corresponding to the list on which the page was
1002 * found will be decremented.
1004 * Restrictions:
1005 * (1) Must be called with an elevated refcount on the page. This is a
1006 * fundamentnal difference from isolate_lru_pages (which is called
1007 * without a stable reference).
1008 * (2) the lru_lock must not be held.
1009 * (3) interrupts must be enabled.
1011 int isolate_lru_page(struct page *page)
1013 int ret = -EBUSY;
1015 if (PageLRU(page)) {
1016 struct zone *zone = page_zone(page);
1018 spin_lock_irq(&zone->lru_lock);
1019 if (PageLRU(page) && get_page_unless_zero(page)) {
1020 int lru = page_lru(page);
1021 ret = 0;
1022 ClearPageLRU(page);
1024 del_page_from_lru_list(zone, page, lru);
1026 spin_unlock_irq(&zone->lru_lock);
1028 return ret;
1032 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1033 * of reclaimed pages
1035 static unsigned long shrink_inactive_list(unsigned long max_scan,
1036 struct zone *zone, struct scan_control *sc,
1037 int priority, int file)
1039 LIST_HEAD(page_list);
1040 struct pagevec pvec;
1041 unsigned long nr_scanned = 0;
1042 unsigned long nr_reclaimed = 0;
1043 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1044 int lumpy_reclaim = 0;
1047 * If we need a large contiguous chunk of memory, or have
1048 * trouble getting a small set of contiguous pages, we
1049 * will reclaim both active and inactive pages.
1051 * We use the same threshold as pageout congestion_wait below.
1053 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1054 lumpy_reclaim = 1;
1055 else if (sc->order && priority < DEF_PRIORITY - 2)
1056 lumpy_reclaim = 1;
1058 pagevec_init(&pvec, 1);
1060 lru_add_drain();
1061 spin_lock_irq(&zone->lru_lock);
1062 do {
1063 struct page *page;
1064 unsigned long nr_taken;
1065 unsigned long nr_scan;
1066 unsigned long nr_freed;
1067 unsigned long nr_active;
1068 unsigned int count[NR_LRU_LISTS] = { 0, };
1069 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1071 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1072 &page_list, &nr_scan, sc->order, mode,
1073 zone, sc->mem_cgroup, 0, file);
1074 nr_active = clear_active_flags(&page_list, count);
1075 __count_vm_events(PGDEACTIVATE, nr_active);
1077 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1078 -count[LRU_ACTIVE_FILE]);
1079 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1080 -count[LRU_INACTIVE_FILE]);
1081 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1082 -count[LRU_ACTIVE_ANON]);
1083 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1084 -count[LRU_INACTIVE_ANON]);
1086 if (scanning_global_lru(sc))
1087 zone->pages_scanned += nr_scan;
1089 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1090 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1091 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1092 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1094 spin_unlock_irq(&zone->lru_lock);
1096 nr_scanned += nr_scan;
1097 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1100 * If we are direct reclaiming for contiguous pages and we do
1101 * not reclaim everything in the list, try again and wait
1102 * for IO to complete. This will stall high-order allocations
1103 * but that should be acceptable to the caller
1105 if (nr_freed < nr_taken && !current_is_kswapd() &&
1106 lumpy_reclaim) {
1107 congestion_wait(WRITE, HZ/10);
1110 * The attempt at page out may have made some
1111 * of the pages active, mark them inactive again.
1113 nr_active = clear_active_flags(&page_list, count);
1114 count_vm_events(PGDEACTIVATE, nr_active);
1116 nr_freed += shrink_page_list(&page_list, sc,
1117 PAGEOUT_IO_SYNC);
1120 nr_reclaimed += nr_freed;
1121 local_irq_disable();
1122 if (current_is_kswapd()) {
1123 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1124 __count_vm_events(KSWAPD_STEAL, nr_freed);
1125 } else if (scanning_global_lru(sc))
1126 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1128 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1130 if (nr_taken == 0)
1131 goto done;
1133 spin_lock(&zone->lru_lock);
1135 * Put back any unfreeable pages.
1137 while (!list_empty(&page_list)) {
1138 int lru;
1139 page = lru_to_page(&page_list);
1140 VM_BUG_ON(PageLRU(page));
1141 list_del(&page->lru);
1142 if (unlikely(!page_evictable(page, NULL))) {
1143 spin_unlock_irq(&zone->lru_lock);
1144 putback_lru_page(page);
1145 spin_lock_irq(&zone->lru_lock);
1146 continue;
1148 SetPageLRU(page);
1149 lru = page_lru(page);
1150 add_page_to_lru_list(zone, page, lru);
1151 if (PageActive(page)) {
1152 int file = !!page_is_file_cache(page);
1153 reclaim_stat->recent_rotated[file]++;
1155 if (!pagevec_add(&pvec, page)) {
1156 spin_unlock_irq(&zone->lru_lock);
1157 __pagevec_release(&pvec);
1158 spin_lock_irq(&zone->lru_lock);
1161 } while (nr_scanned < max_scan);
1162 spin_unlock(&zone->lru_lock);
1163 done:
1164 local_irq_enable();
1165 pagevec_release(&pvec);
1166 return nr_reclaimed;
1170 * We are about to scan this zone at a certain priority level. If that priority
1171 * level is smaller (ie: more urgent) than the previous priority, then note
1172 * that priority level within the zone. This is done so that when the next
1173 * process comes in to scan this zone, it will immediately start out at this
1174 * priority level rather than having to build up its own scanning priority.
1175 * Here, this priority affects only the reclaim-mapped threshold.
1177 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1179 if (priority < zone->prev_priority)
1180 zone->prev_priority = priority;
1184 * This moves pages from the active list to the inactive list.
1186 * We move them the other way if the page is referenced by one or more
1187 * processes, from rmap.
1189 * If the pages are mostly unmapped, the processing is fast and it is
1190 * appropriate to hold zone->lru_lock across the whole operation. But if
1191 * the pages are mapped, the processing is slow (page_referenced()) so we
1192 * should drop zone->lru_lock around each page. It's impossible to balance
1193 * this, so instead we remove the pages from the LRU while processing them.
1194 * It is safe to rely on PG_active against the non-LRU pages in here because
1195 * nobody will play with that bit on a non-LRU page.
1197 * The downside is that we have to touch page->_count against each page.
1198 * But we had to alter page->flags anyway.
1201 static void move_active_pages_to_lru(struct zone *zone,
1202 struct list_head *list,
1203 enum lru_list lru)
1205 unsigned long pgmoved = 0;
1206 struct pagevec pvec;
1207 struct page *page;
1209 pagevec_init(&pvec, 1);
1211 while (!list_empty(list)) {
1212 page = lru_to_page(list);
1213 prefetchw_prev_lru_page(page, list, flags);
1215 VM_BUG_ON(PageLRU(page));
1216 SetPageLRU(page);
1218 VM_BUG_ON(!PageActive(page));
1219 if (!is_active_lru(lru))
1220 ClearPageActive(page); /* we are de-activating */
1222 list_move(&page->lru, &zone->lru[lru].list);
1223 mem_cgroup_add_lru_list(page, lru);
1224 pgmoved++;
1226 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1227 spin_unlock_irq(&zone->lru_lock);
1228 if (buffer_heads_over_limit)
1229 pagevec_strip(&pvec);
1230 __pagevec_release(&pvec);
1231 spin_lock_irq(&zone->lru_lock);
1234 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1235 if (!is_active_lru(lru))
1236 __count_vm_events(PGDEACTIVATE, pgmoved);
1239 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1240 struct scan_control *sc, int priority, int file)
1242 unsigned long pgmoved;
1243 unsigned long pgscanned;
1244 unsigned long vm_flags;
1245 LIST_HEAD(l_hold); /* The pages which were snipped off */
1246 LIST_HEAD(l_active);
1247 LIST_HEAD(l_inactive);
1248 struct page *page;
1249 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1251 lru_add_drain();
1252 spin_lock_irq(&zone->lru_lock);
1253 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1254 ISOLATE_ACTIVE, zone,
1255 sc->mem_cgroup, 1, file);
1257 * zone->pages_scanned is used for detect zone's oom
1258 * mem_cgroup remembers nr_scan by itself.
1260 if (scanning_global_lru(sc)) {
1261 zone->pages_scanned += pgscanned;
1263 reclaim_stat->recent_scanned[!!file] += pgmoved;
1265 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1266 if (file)
1267 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1268 else
1269 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1270 spin_unlock_irq(&zone->lru_lock);
1272 pgmoved = 0; /* count referenced (mapping) mapped pages */
1273 while (!list_empty(&l_hold)) {
1274 cond_resched();
1275 page = lru_to_page(&l_hold);
1276 list_del(&page->lru);
1278 if (unlikely(!page_evictable(page, NULL))) {
1279 putback_lru_page(page);
1280 continue;
1283 /* page_referenced clears PageReferenced */
1284 if (page_mapping_inuse(page) &&
1285 page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1286 pgmoved++;
1288 * Identify referenced, file-backed active pages and
1289 * give them one more trip around the active list. So
1290 * that executable code get better chances to stay in
1291 * memory under moderate memory pressure. Anon pages
1292 * are not likely to be evicted by use-once streaming
1293 * IO, plus JVM can create lots of anon VM_EXEC pages,
1294 * so we ignore them here.
1296 if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
1297 list_add(&page->lru, &l_active);
1298 continue;
1302 list_add(&page->lru, &l_inactive);
1306 * Move pages back to the lru list.
1308 spin_lock_irq(&zone->lru_lock);
1310 * Count referenced pages from currently used mappings as rotated,
1311 * even though only some of them are actually re-activated. This
1312 * helps balance scan pressure between file and anonymous pages in
1313 * get_scan_ratio.
1315 reclaim_stat->recent_rotated[!!file] += pgmoved;
1317 move_active_pages_to_lru(zone, &l_active,
1318 LRU_ACTIVE + file * LRU_FILE);
1319 move_active_pages_to_lru(zone, &l_inactive,
1320 LRU_BASE + file * LRU_FILE);
1322 spin_unlock_irq(&zone->lru_lock);
1325 static int inactive_anon_is_low_global(struct zone *zone)
1327 unsigned long active, inactive;
1329 active = zone_page_state(zone, NR_ACTIVE_ANON);
1330 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1332 if (inactive * zone->inactive_ratio < active)
1333 return 1;
1335 return 0;
1339 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1340 * @zone: zone to check
1341 * @sc: scan control of this context
1343 * Returns true if the zone does not have enough inactive anon pages,
1344 * meaning some active anon pages need to be deactivated.
1346 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1348 int low;
1350 if (scanning_global_lru(sc))
1351 low = inactive_anon_is_low_global(zone);
1352 else
1353 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1354 return low;
1357 static int inactive_file_is_low_global(struct zone *zone)
1359 unsigned long active, inactive;
1361 active = zone_page_state(zone, NR_ACTIVE_FILE);
1362 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1364 return (active > inactive);
1368 * inactive_file_is_low - check if file pages need to be deactivated
1369 * @zone: zone to check
1370 * @sc: scan control of this context
1372 * When the system is doing streaming IO, memory pressure here
1373 * ensures that active file pages get deactivated, until more
1374 * than half of the file pages are on the inactive list.
1376 * Once we get to that situation, protect the system's working
1377 * set from being evicted by disabling active file page aging.
1379 * This uses a different ratio than the anonymous pages, because
1380 * the page cache uses a use-once replacement algorithm.
1382 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1384 int low;
1386 if (scanning_global_lru(sc))
1387 low = inactive_file_is_low_global(zone);
1388 else
1389 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1390 return low;
1393 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1394 struct zone *zone, struct scan_control *sc, int priority)
1396 int file = is_file_lru(lru);
1398 if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
1399 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1400 return 0;
1403 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1404 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1405 return 0;
1407 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1411 * Determine how aggressively the anon and file LRU lists should be
1412 * scanned. The relative value of each set of LRU lists is determined
1413 * by looking at the fraction of the pages scanned we did rotate back
1414 * onto the active list instead of evict.
1416 * percent[0] specifies how much pressure to put on ram/swap backed
1417 * memory, while percent[1] determines pressure on the file LRUs.
1419 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1420 unsigned long *percent)
1422 unsigned long anon, file, free;
1423 unsigned long anon_prio, file_prio;
1424 unsigned long ap, fp;
1425 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1427 anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
1428 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
1429 file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
1430 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1432 if (scanning_global_lru(sc)) {
1433 free = zone_page_state(zone, NR_FREE_PAGES);
1434 /* If we have very few page cache pages,
1435 force-scan anon pages. */
1436 if (unlikely(file + free <= high_wmark_pages(zone))) {
1437 percent[0] = 100;
1438 percent[1] = 0;
1439 return;
1444 * OK, so we have swap space and a fair amount of page cache
1445 * pages. We use the recently rotated / recently scanned
1446 * ratios to determine how valuable each cache is.
1448 * Because workloads change over time (and to avoid overflow)
1449 * we keep these statistics as a floating average, which ends
1450 * up weighing recent references more than old ones.
1452 * anon in [0], file in [1]
1454 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1455 spin_lock_irq(&zone->lru_lock);
1456 reclaim_stat->recent_scanned[0] /= 2;
1457 reclaim_stat->recent_rotated[0] /= 2;
1458 spin_unlock_irq(&zone->lru_lock);
1461 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1462 spin_lock_irq(&zone->lru_lock);
1463 reclaim_stat->recent_scanned[1] /= 2;
1464 reclaim_stat->recent_rotated[1] /= 2;
1465 spin_unlock_irq(&zone->lru_lock);
1469 * With swappiness at 100, anonymous and file have the same priority.
1470 * This scanning priority is essentially the inverse of IO cost.
1472 anon_prio = sc->swappiness;
1473 file_prio = 200 - sc->swappiness;
1476 * The amount of pressure on anon vs file pages is inversely
1477 * proportional to the fraction of recently scanned pages on
1478 * each list that were recently referenced and in active use.
1480 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1481 ap /= reclaim_stat->recent_rotated[0] + 1;
1483 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1484 fp /= reclaim_stat->recent_rotated[1] + 1;
1486 /* Normalize to percentages */
1487 percent[0] = 100 * ap / (ap + fp + 1);
1488 percent[1] = 100 - percent[0];
1492 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1493 * until we collected @swap_cluster_max pages to scan.
1495 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1496 unsigned long *nr_saved_scan,
1497 unsigned long swap_cluster_max)
1499 unsigned long nr;
1501 *nr_saved_scan += nr_to_scan;
1502 nr = *nr_saved_scan;
1504 if (nr >= swap_cluster_max)
1505 *nr_saved_scan = 0;
1506 else
1507 nr = 0;
1509 return nr;
1513 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1515 static void shrink_zone(int priority, struct zone *zone,
1516 struct scan_control *sc)
1518 unsigned long nr[NR_LRU_LISTS];
1519 unsigned long nr_to_scan;
1520 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1521 enum lru_list l;
1522 unsigned long nr_reclaimed = sc->nr_reclaimed;
1523 unsigned long swap_cluster_max = sc->swap_cluster_max;
1524 int noswap = 0;
1526 /* If we have no swap space, do not bother scanning anon pages. */
1527 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1528 noswap = 1;
1529 percent[0] = 0;
1530 percent[1] = 100;
1531 } else
1532 get_scan_ratio(zone, sc, percent);
1534 for_each_evictable_lru(l) {
1535 int file = is_file_lru(l);
1536 unsigned long scan;
1538 scan = zone_nr_pages(zone, sc, l);
1539 if (priority || noswap) {
1540 scan >>= priority;
1541 scan = (scan * percent[file]) / 100;
1543 if (scanning_global_lru(sc))
1544 nr[l] = nr_scan_try_batch(scan,
1545 &zone->lru[l].nr_saved_scan,
1546 swap_cluster_max);
1547 else
1548 nr[l] = scan;
1551 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1552 nr[LRU_INACTIVE_FILE]) {
1553 for_each_evictable_lru(l) {
1554 if (nr[l]) {
1555 nr_to_scan = min(nr[l], swap_cluster_max);
1556 nr[l] -= nr_to_scan;
1558 nr_reclaimed += shrink_list(l, nr_to_scan,
1559 zone, sc, priority);
1563 * On large memory systems, scan >> priority can become
1564 * really large. This is fine for the starting priority;
1565 * we want to put equal scanning pressure on each zone.
1566 * However, if the VM has a harder time of freeing pages,
1567 * with multiple processes reclaiming pages, the total
1568 * freeing target can get unreasonably large.
1570 if (nr_reclaimed > swap_cluster_max &&
1571 priority < DEF_PRIORITY && !current_is_kswapd())
1572 break;
1575 sc->nr_reclaimed = nr_reclaimed;
1578 * Even if we did not try to evict anon pages at all, we want to
1579 * rebalance the anon lru active/inactive ratio.
1581 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1582 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1584 throttle_vm_writeout(sc->gfp_mask);
1588 * This is the direct reclaim path, for page-allocating processes. We only
1589 * try to reclaim pages from zones which will satisfy the caller's allocation
1590 * request.
1592 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1593 * Because:
1594 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1595 * allocation or
1596 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1597 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1598 * zone defense algorithm.
1600 * If a zone is deemed to be full of pinned pages then just give it a light
1601 * scan then give up on it.
1603 static void shrink_zones(int priority, struct zonelist *zonelist,
1604 struct scan_control *sc)
1606 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1607 struct zoneref *z;
1608 struct zone *zone;
1610 sc->all_unreclaimable = 1;
1611 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1612 sc->nodemask) {
1613 if (!populated_zone(zone))
1614 continue;
1616 * Take care memory controller reclaiming has small influence
1617 * to global LRU.
1619 if (scanning_global_lru(sc)) {
1620 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1621 continue;
1622 note_zone_scanning_priority(zone, priority);
1624 if (zone_is_all_unreclaimable(zone) &&
1625 priority != DEF_PRIORITY)
1626 continue; /* Let kswapd poll it */
1627 sc->all_unreclaimable = 0;
1628 } else {
1630 * Ignore cpuset limitation here. We just want to reduce
1631 * # of used pages by us regardless of memory shortage.
1633 sc->all_unreclaimable = 0;
1634 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1635 priority);
1638 shrink_zone(priority, zone, sc);
1643 * This is the main entry point to direct page reclaim.
1645 * If a full scan of the inactive list fails to free enough memory then we
1646 * are "out of memory" and something needs to be killed.
1648 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1649 * high - the zone may be full of dirty or under-writeback pages, which this
1650 * caller can't do much about. We kick pdflush and take explicit naps in the
1651 * hope that some of these pages can be written. But if the allocating task
1652 * holds filesystem locks which prevent writeout this might not work, and the
1653 * allocation attempt will fail.
1655 * returns: 0, if no pages reclaimed
1656 * else, the number of pages reclaimed
1658 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1659 struct scan_control *sc)
1661 int priority;
1662 unsigned long ret = 0;
1663 unsigned long total_scanned = 0;
1664 struct reclaim_state *reclaim_state = current->reclaim_state;
1665 unsigned long lru_pages = 0;
1666 struct zoneref *z;
1667 struct zone *zone;
1668 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1670 delayacct_freepages_start();
1672 if (scanning_global_lru(sc))
1673 count_vm_event(ALLOCSTALL);
1675 * mem_cgroup will not do shrink_slab.
1677 if (scanning_global_lru(sc)) {
1678 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1680 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1681 continue;
1683 lru_pages += zone_lru_pages(zone);
1687 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1688 sc->nr_scanned = 0;
1689 if (!priority)
1690 disable_swap_token();
1691 shrink_zones(priority, zonelist, sc);
1693 * Don't shrink slabs when reclaiming memory from
1694 * over limit cgroups
1696 if (scanning_global_lru(sc)) {
1697 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1698 if (reclaim_state) {
1699 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1700 reclaim_state->reclaimed_slab = 0;
1703 total_scanned += sc->nr_scanned;
1704 if (sc->nr_reclaimed >= sc->swap_cluster_max) {
1705 ret = sc->nr_reclaimed;
1706 goto out;
1710 * Try to write back as many pages as we just scanned. This
1711 * tends to cause slow streaming writers to write data to the
1712 * disk smoothly, at the dirtying rate, which is nice. But
1713 * that's undesirable in laptop mode, where we *want* lumpy
1714 * writeout. So in laptop mode, write out the whole world.
1716 if (total_scanned > sc->swap_cluster_max +
1717 sc->swap_cluster_max / 2) {
1718 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1719 sc->may_writepage = 1;
1722 /* Take a nap, wait for some writeback to complete */
1723 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1724 congestion_wait(WRITE, HZ/10);
1726 /* top priority shrink_zones still had more to do? don't OOM, then */
1727 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1728 ret = sc->nr_reclaimed;
1729 out:
1731 * Now that we've scanned all the zones at this priority level, note
1732 * that level within the zone so that the next thread which performs
1733 * scanning of this zone will immediately start out at this priority
1734 * level. This affects only the decision whether or not to bring
1735 * mapped pages onto the inactive list.
1737 if (priority < 0)
1738 priority = 0;
1740 if (scanning_global_lru(sc)) {
1741 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1743 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1744 continue;
1746 zone->prev_priority = priority;
1748 } else
1749 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1751 delayacct_freepages_end();
1753 return ret;
1756 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1757 gfp_t gfp_mask, nodemask_t *nodemask)
1759 struct scan_control sc = {
1760 .gfp_mask = gfp_mask,
1761 .may_writepage = !laptop_mode,
1762 .swap_cluster_max = SWAP_CLUSTER_MAX,
1763 .may_unmap = 1,
1764 .may_swap = 1,
1765 .swappiness = vm_swappiness,
1766 .order = order,
1767 .mem_cgroup = NULL,
1768 .isolate_pages = isolate_pages_global,
1769 .nodemask = nodemask,
1772 return do_try_to_free_pages(zonelist, &sc);
1775 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1777 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1778 gfp_t gfp_mask,
1779 bool noswap,
1780 unsigned int swappiness)
1782 struct scan_control sc = {
1783 .may_writepage = !laptop_mode,
1784 .may_unmap = 1,
1785 .may_swap = !noswap,
1786 .swap_cluster_max = SWAP_CLUSTER_MAX,
1787 .swappiness = swappiness,
1788 .order = 0,
1789 .mem_cgroup = mem_cont,
1790 .isolate_pages = mem_cgroup_isolate_pages,
1791 .nodemask = NULL, /* we don't care the placement */
1793 struct zonelist *zonelist;
1795 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1796 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1797 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1798 return do_try_to_free_pages(zonelist, &sc);
1800 #endif
1803 * For kswapd, balance_pgdat() will work across all this node's zones until
1804 * they are all at high_wmark_pages(zone).
1806 * Returns the number of pages which were actually freed.
1808 * There is special handling here for zones which are full of pinned pages.
1809 * This can happen if the pages are all mlocked, or if they are all used by
1810 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1811 * What we do is to detect the case where all pages in the zone have been
1812 * scanned twice and there has been zero successful reclaim. Mark the zone as
1813 * dead and from now on, only perform a short scan. Basically we're polling
1814 * the zone for when the problem goes away.
1816 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1817 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1818 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1819 * lower zones regardless of the number of free pages in the lower zones. This
1820 * interoperates with the page allocator fallback scheme to ensure that aging
1821 * of pages is balanced across the zones.
1823 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1825 int all_zones_ok;
1826 int priority;
1827 int i;
1828 unsigned long total_scanned;
1829 struct reclaim_state *reclaim_state = current->reclaim_state;
1830 struct scan_control sc = {
1831 .gfp_mask = GFP_KERNEL,
1832 .may_unmap = 1,
1833 .may_swap = 1,
1834 .swap_cluster_max = SWAP_CLUSTER_MAX,
1835 .swappiness = vm_swappiness,
1836 .order = order,
1837 .mem_cgroup = NULL,
1838 .isolate_pages = isolate_pages_global,
1841 * temp_priority is used to remember the scanning priority at which
1842 * this zone was successfully refilled to
1843 * free_pages == high_wmark_pages(zone).
1845 int temp_priority[MAX_NR_ZONES];
1847 loop_again:
1848 total_scanned = 0;
1849 sc.nr_reclaimed = 0;
1850 sc.may_writepage = !laptop_mode;
1851 count_vm_event(PAGEOUTRUN);
1853 for (i = 0; i < pgdat->nr_zones; i++)
1854 temp_priority[i] = DEF_PRIORITY;
1856 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1857 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1858 unsigned long lru_pages = 0;
1860 /* The swap token gets in the way of swapout... */
1861 if (!priority)
1862 disable_swap_token();
1864 all_zones_ok = 1;
1867 * Scan in the highmem->dma direction for the highest
1868 * zone which needs scanning
1870 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1871 struct zone *zone = pgdat->node_zones + i;
1873 if (!populated_zone(zone))
1874 continue;
1876 if (zone_is_all_unreclaimable(zone) &&
1877 priority != DEF_PRIORITY)
1878 continue;
1881 * Do some background aging of the anon list, to give
1882 * pages a chance to be referenced before reclaiming.
1884 if (inactive_anon_is_low(zone, &sc))
1885 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1886 &sc, priority, 0);
1888 if (!zone_watermark_ok(zone, order,
1889 high_wmark_pages(zone), 0, 0)) {
1890 end_zone = i;
1891 break;
1894 if (i < 0)
1895 goto out;
1897 for (i = 0; i <= end_zone; i++) {
1898 struct zone *zone = pgdat->node_zones + i;
1900 lru_pages += zone_lru_pages(zone);
1904 * Now scan the zone in the dma->highmem direction, stopping
1905 * at the last zone which needs scanning.
1907 * We do this because the page allocator works in the opposite
1908 * direction. This prevents the page allocator from allocating
1909 * pages behind kswapd's direction of progress, which would
1910 * cause too much scanning of the lower zones.
1912 for (i = 0; i <= end_zone; i++) {
1913 struct zone *zone = pgdat->node_zones + i;
1914 int nr_slab;
1916 if (!populated_zone(zone))
1917 continue;
1919 if (zone_is_all_unreclaimable(zone) &&
1920 priority != DEF_PRIORITY)
1921 continue;
1923 if (!zone_watermark_ok(zone, order,
1924 high_wmark_pages(zone), end_zone, 0))
1925 all_zones_ok = 0;
1926 temp_priority[i] = priority;
1927 sc.nr_scanned = 0;
1928 note_zone_scanning_priority(zone, priority);
1930 * We put equal pressure on every zone, unless one
1931 * zone has way too many pages free already.
1933 if (!zone_watermark_ok(zone, order,
1934 8*high_wmark_pages(zone), end_zone, 0))
1935 shrink_zone(priority, zone, &sc);
1936 reclaim_state->reclaimed_slab = 0;
1937 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1938 lru_pages);
1939 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1940 total_scanned += sc.nr_scanned;
1941 if (zone_is_all_unreclaimable(zone))
1942 continue;
1943 if (nr_slab == 0 && zone->pages_scanned >=
1944 (zone_lru_pages(zone) * 6))
1945 zone_set_flag(zone,
1946 ZONE_ALL_UNRECLAIMABLE);
1948 * If we've done a decent amount of scanning and
1949 * the reclaim ratio is low, start doing writepage
1950 * even in laptop mode
1952 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1953 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
1954 sc.may_writepage = 1;
1956 if (all_zones_ok)
1957 break; /* kswapd: all done */
1959 * OK, kswapd is getting into trouble. Take a nap, then take
1960 * another pass across the zones.
1962 if (total_scanned && priority < DEF_PRIORITY - 2)
1963 congestion_wait(WRITE, HZ/10);
1966 * We do this so kswapd doesn't build up large priorities for
1967 * example when it is freeing in parallel with allocators. It
1968 * matches the direct reclaim path behaviour in terms of impact
1969 * on zone->*_priority.
1971 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
1972 break;
1974 out:
1976 * Note within each zone the priority level at which this zone was
1977 * brought into a happy state. So that the next thread which scans this
1978 * zone will start out at that priority level.
1980 for (i = 0; i < pgdat->nr_zones; i++) {
1981 struct zone *zone = pgdat->node_zones + i;
1983 zone->prev_priority = temp_priority[i];
1985 if (!all_zones_ok) {
1986 cond_resched();
1988 try_to_freeze();
1991 * Fragmentation may mean that the system cannot be
1992 * rebalanced for high-order allocations in all zones.
1993 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
1994 * it means the zones have been fully scanned and are still
1995 * not balanced. For high-order allocations, there is
1996 * little point trying all over again as kswapd may
1997 * infinite loop.
1999 * Instead, recheck all watermarks at order-0 as they
2000 * are the most important. If watermarks are ok, kswapd will go
2001 * back to sleep. High-order users can still perform direct
2002 * reclaim if they wish.
2004 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2005 order = sc.order = 0;
2007 goto loop_again;
2010 return sc.nr_reclaimed;
2014 * The background pageout daemon, started as a kernel thread
2015 * from the init process.
2017 * This basically trickles out pages so that we have _some_
2018 * free memory available even if there is no other activity
2019 * that frees anything up. This is needed for things like routing
2020 * etc, where we otherwise might have all activity going on in
2021 * asynchronous contexts that cannot page things out.
2023 * If there are applications that are active memory-allocators
2024 * (most normal use), this basically shouldn't matter.
2026 static int kswapd(void *p)
2028 unsigned long order;
2029 pg_data_t *pgdat = (pg_data_t*)p;
2030 struct task_struct *tsk = current;
2031 DEFINE_WAIT(wait);
2032 struct reclaim_state reclaim_state = {
2033 .reclaimed_slab = 0,
2035 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2037 lockdep_set_current_reclaim_state(GFP_KERNEL);
2039 if (!cpumask_empty(cpumask))
2040 set_cpus_allowed_ptr(tsk, cpumask);
2041 current->reclaim_state = &reclaim_state;
2044 * Tell the memory management that we're a "memory allocator",
2045 * and that if we need more memory we should get access to it
2046 * regardless (see "__alloc_pages()"). "kswapd" should
2047 * never get caught in the normal page freeing logic.
2049 * (Kswapd normally doesn't need memory anyway, but sometimes
2050 * you need a small amount of memory in order to be able to
2051 * page out something else, and this flag essentially protects
2052 * us from recursively trying to free more memory as we're
2053 * trying to free the first piece of memory in the first place).
2055 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2056 set_freezable();
2058 order = 0;
2059 for ( ; ; ) {
2060 unsigned long new_order;
2062 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2063 new_order = pgdat->kswapd_max_order;
2064 pgdat->kswapd_max_order = 0;
2065 if (order < new_order) {
2067 * Don't sleep if someone wants a larger 'order'
2068 * allocation
2070 order = new_order;
2071 } else {
2072 if (!freezing(current))
2073 schedule();
2075 order = pgdat->kswapd_max_order;
2077 finish_wait(&pgdat->kswapd_wait, &wait);
2079 if (!try_to_freeze()) {
2080 /* We can speed up thawing tasks if we don't call
2081 * balance_pgdat after returning from the refrigerator
2083 balance_pgdat(pgdat, order);
2086 return 0;
2090 * A zone is low on free memory, so wake its kswapd task to service it.
2092 void wakeup_kswapd(struct zone *zone, int order)
2094 pg_data_t *pgdat;
2096 if (!populated_zone(zone))
2097 return;
2099 pgdat = zone->zone_pgdat;
2100 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2101 return;
2102 if (pgdat->kswapd_max_order < order)
2103 pgdat->kswapd_max_order = order;
2104 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2105 return;
2106 if (!waitqueue_active(&pgdat->kswapd_wait))
2107 return;
2108 wake_up_interruptible(&pgdat->kswapd_wait);
2111 unsigned long global_lru_pages(void)
2113 return global_page_state(NR_ACTIVE_ANON)
2114 + global_page_state(NR_ACTIVE_FILE)
2115 + global_page_state(NR_INACTIVE_ANON)
2116 + global_page_state(NR_INACTIVE_FILE);
2119 #ifdef CONFIG_HIBERNATION
2121 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
2122 * from LRU lists system-wide, for given pass and priority.
2124 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
2126 static void shrink_all_zones(unsigned long nr_pages, int prio,
2127 int pass, struct scan_control *sc)
2129 struct zone *zone;
2130 unsigned long nr_reclaimed = 0;
2132 for_each_populated_zone(zone) {
2133 enum lru_list l;
2135 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2136 continue;
2138 for_each_evictable_lru(l) {
2139 enum zone_stat_item ls = NR_LRU_BASE + l;
2140 unsigned long lru_pages = zone_page_state(zone, ls);
2142 /* For pass = 0, we don't shrink the active list */
2143 if (pass == 0 && (l == LRU_ACTIVE_ANON ||
2144 l == LRU_ACTIVE_FILE))
2145 continue;
2147 zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1;
2148 if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) {
2149 unsigned long nr_to_scan;
2151 zone->lru[l].nr_saved_scan = 0;
2152 nr_to_scan = min(nr_pages, lru_pages);
2153 nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2154 sc, prio);
2155 if (nr_reclaimed >= nr_pages) {
2156 sc->nr_reclaimed += nr_reclaimed;
2157 return;
2162 sc->nr_reclaimed += nr_reclaimed;
2166 * Try to free `nr_pages' of memory, system-wide, and return the number of
2167 * freed pages.
2169 * Rather than trying to age LRUs the aim is to preserve the overall
2170 * LRU order by reclaiming preferentially
2171 * inactive > active > active referenced > active mapped
2173 unsigned long shrink_all_memory(unsigned long nr_pages)
2175 unsigned long lru_pages, nr_slab;
2176 int pass;
2177 struct reclaim_state reclaim_state;
2178 struct scan_control sc = {
2179 .gfp_mask = GFP_KERNEL,
2180 .may_unmap = 0,
2181 .may_writepage = 1,
2182 .isolate_pages = isolate_pages_global,
2183 .nr_reclaimed = 0,
2186 current->reclaim_state = &reclaim_state;
2188 lru_pages = global_lru_pages();
2189 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2190 /* If slab caches are huge, it's better to hit them first */
2191 while (nr_slab >= lru_pages) {
2192 reclaim_state.reclaimed_slab = 0;
2193 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2194 if (!reclaim_state.reclaimed_slab)
2195 break;
2197 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2198 if (sc.nr_reclaimed >= nr_pages)
2199 goto out;
2201 nr_slab -= reclaim_state.reclaimed_slab;
2205 * We try to shrink LRUs in 5 passes:
2206 * 0 = Reclaim from inactive_list only
2207 * 1 = Reclaim from active list but don't reclaim mapped
2208 * 2 = 2nd pass of type 1
2209 * 3 = Reclaim mapped (normal reclaim)
2210 * 4 = 2nd pass of type 3
2212 for (pass = 0; pass < 5; pass++) {
2213 int prio;
2215 /* Force reclaiming mapped pages in the passes #3 and #4 */
2216 if (pass > 2)
2217 sc.may_unmap = 1;
2219 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2220 unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2222 sc.nr_scanned = 0;
2223 sc.swap_cluster_max = nr_to_scan;
2224 shrink_all_zones(nr_to_scan, prio, pass, &sc);
2225 if (sc.nr_reclaimed >= nr_pages)
2226 goto out;
2228 reclaim_state.reclaimed_slab = 0;
2229 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2230 global_lru_pages());
2231 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2232 if (sc.nr_reclaimed >= nr_pages)
2233 goto out;
2235 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2236 congestion_wait(WRITE, HZ / 10);
2241 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
2242 * something in slab caches
2244 if (!sc.nr_reclaimed) {
2245 do {
2246 reclaim_state.reclaimed_slab = 0;
2247 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2248 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2249 } while (sc.nr_reclaimed < nr_pages &&
2250 reclaim_state.reclaimed_slab > 0);
2254 out:
2255 current->reclaim_state = NULL;
2257 return sc.nr_reclaimed;
2259 #endif /* CONFIG_HIBERNATION */
2261 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2262 not required for correctness. So if the last cpu in a node goes
2263 away, we get changed to run anywhere: as the first one comes back,
2264 restore their cpu bindings. */
2265 static int __devinit cpu_callback(struct notifier_block *nfb,
2266 unsigned long action, void *hcpu)
2268 int nid;
2270 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2271 for_each_node_state(nid, N_HIGH_MEMORY) {
2272 pg_data_t *pgdat = NODE_DATA(nid);
2273 const struct cpumask *mask;
2275 mask = cpumask_of_node(pgdat->node_id);
2277 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2278 /* One of our CPUs online: restore mask */
2279 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2282 return NOTIFY_OK;
2286 * This kswapd start function will be called by init and node-hot-add.
2287 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2289 int kswapd_run(int nid)
2291 pg_data_t *pgdat = NODE_DATA(nid);
2292 int ret = 0;
2294 if (pgdat->kswapd)
2295 return 0;
2297 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2298 if (IS_ERR(pgdat->kswapd)) {
2299 /* failure at boot is fatal */
2300 BUG_ON(system_state == SYSTEM_BOOTING);
2301 printk("Failed to start kswapd on node %d\n",nid);
2302 ret = -1;
2304 return ret;
2307 static int __init kswapd_init(void)
2309 int nid;
2311 swap_setup();
2312 for_each_node_state(nid, N_HIGH_MEMORY)
2313 kswapd_run(nid);
2314 hotcpu_notifier(cpu_callback, 0);
2315 return 0;
2318 module_init(kswapd_init)
2320 #ifdef CONFIG_NUMA
2322 * Zone reclaim mode
2324 * If non-zero call zone_reclaim when the number of free pages falls below
2325 * the watermarks.
2327 int zone_reclaim_mode __read_mostly;
2329 #define RECLAIM_OFF 0
2330 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2331 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2332 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2335 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2336 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2337 * a zone.
2339 #define ZONE_RECLAIM_PRIORITY 4
2342 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2343 * occur.
2345 int sysctl_min_unmapped_ratio = 1;
2348 * If the number of slab pages in a zone grows beyond this percentage then
2349 * slab reclaim needs to occur.
2351 int sysctl_min_slab_ratio = 5;
2353 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2355 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2356 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2357 zone_page_state(zone, NR_ACTIVE_FILE);
2360 * It's possible for there to be more file mapped pages than
2361 * accounted for by the pages on the file LRU lists because
2362 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2364 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2367 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2368 static long zone_pagecache_reclaimable(struct zone *zone)
2370 long nr_pagecache_reclaimable;
2371 long delta = 0;
2374 * If RECLAIM_SWAP is set, then all file pages are considered
2375 * potentially reclaimable. Otherwise, we have to worry about
2376 * pages like swapcache and zone_unmapped_file_pages() provides
2377 * a better estimate
2379 if (zone_reclaim_mode & RECLAIM_SWAP)
2380 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2381 else
2382 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2384 /* If we can't clean pages, remove dirty pages from consideration */
2385 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2386 delta += zone_page_state(zone, NR_FILE_DIRTY);
2388 /* Watch for any possible underflows due to delta */
2389 if (unlikely(delta > nr_pagecache_reclaimable))
2390 delta = nr_pagecache_reclaimable;
2392 return nr_pagecache_reclaimable - delta;
2396 * Try to free up some pages from this zone through reclaim.
2398 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2400 /* Minimum pages needed in order to stay on node */
2401 const unsigned long nr_pages = 1 << order;
2402 struct task_struct *p = current;
2403 struct reclaim_state reclaim_state;
2404 int priority;
2405 struct scan_control sc = {
2406 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2407 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2408 .may_swap = 1,
2409 .swap_cluster_max = max_t(unsigned long, nr_pages,
2410 SWAP_CLUSTER_MAX),
2411 .gfp_mask = gfp_mask,
2412 .swappiness = vm_swappiness,
2413 .order = order,
2414 .isolate_pages = isolate_pages_global,
2416 unsigned long slab_reclaimable;
2418 disable_swap_token();
2419 cond_resched();
2421 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2422 * and we also need to be able to write out pages for RECLAIM_WRITE
2423 * and RECLAIM_SWAP.
2425 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2426 reclaim_state.reclaimed_slab = 0;
2427 p->reclaim_state = &reclaim_state;
2429 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2431 * Free memory by calling shrink zone with increasing
2432 * priorities until we have enough memory freed.
2434 priority = ZONE_RECLAIM_PRIORITY;
2435 do {
2436 note_zone_scanning_priority(zone, priority);
2437 shrink_zone(priority, zone, &sc);
2438 priority--;
2439 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2442 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2443 if (slab_reclaimable > zone->min_slab_pages) {
2445 * shrink_slab() does not currently allow us to determine how
2446 * many pages were freed in this zone. So we take the current
2447 * number of slab pages and shake the slab until it is reduced
2448 * by the same nr_pages that we used for reclaiming unmapped
2449 * pages.
2451 * Note that shrink_slab will free memory on all zones and may
2452 * take a long time.
2454 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2455 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2456 slab_reclaimable - nr_pages)
2460 * Update nr_reclaimed by the number of slab pages we
2461 * reclaimed from this zone.
2463 sc.nr_reclaimed += slab_reclaimable -
2464 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2467 p->reclaim_state = NULL;
2468 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2469 return sc.nr_reclaimed >= nr_pages;
2472 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2474 int node_id;
2475 int ret;
2478 * Zone reclaim reclaims unmapped file backed pages and
2479 * slab pages if we are over the defined limits.
2481 * A small portion of unmapped file backed pages is needed for
2482 * file I/O otherwise pages read by file I/O will be immediately
2483 * thrown out if the zone is overallocated. So we do not reclaim
2484 * if less than a specified percentage of the zone is used by
2485 * unmapped file backed pages.
2487 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2488 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2489 return ZONE_RECLAIM_FULL;
2491 if (zone_is_all_unreclaimable(zone))
2492 return ZONE_RECLAIM_FULL;
2495 * Do not scan if the allocation should not be delayed.
2497 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2498 return ZONE_RECLAIM_NOSCAN;
2501 * Only run zone reclaim on the local zone or on zones that do not
2502 * have associated processors. This will favor the local processor
2503 * over remote processors and spread off node memory allocations
2504 * as wide as possible.
2506 node_id = zone_to_nid(zone);
2507 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2508 return ZONE_RECLAIM_NOSCAN;
2510 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2511 return ZONE_RECLAIM_NOSCAN;
2513 ret = __zone_reclaim(zone, gfp_mask, order);
2514 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2516 if (!ret)
2517 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2519 return ret;
2521 #endif
2524 * page_evictable - test whether a page is evictable
2525 * @page: the page to test
2526 * @vma: the VMA in which the page is or will be mapped, may be NULL
2528 * Test whether page is evictable--i.e., should be placed on active/inactive
2529 * lists vs unevictable list. The vma argument is !NULL when called from the
2530 * fault path to determine how to instantate a new page.
2532 * Reasons page might not be evictable:
2533 * (1) page's mapping marked unevictable
2534 * (2) page is part of an mlocked VMA
2537 int page_evictable(struct page *page, struct vm_area_struct *vma)
2540 if (mapping_unevictable(page_mapping(page)))
2541 return 0;
2543 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2544 return 0;
2546 return 1;
2550 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2551 * @page: page to check evictability and move to appropriate lru list
2552 * @zone: zone page is in
2554 * Checks a page for evictability and moves the page to the appropriate
2555 * zone lru list.
2557 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2558 * have PageUnevictable set.
2560 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2562 VM_BUG_ON(PageActive(page));
2564 retry:
2565 ClearPageUnevictable(page);
2566 if (page_evictable(page, NULL)) {
2567 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2569 __dec_zone_state(zone, NR_UNEVICTABLE);
2570 list_move(&page->lru, &zone->lru[l].list);
2571 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2572 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2573 __count_vm_event(UNEVICTABLE_PGRESCUED);
2574 } else {
2576 * rotate unevictable list
2578 SetPageUnevictable(page);
2579 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2580 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2581 if (page_evictable(page, NULL))
2582 goto retry;
2587 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2588 * @mapping: struct address_space to scan for evictable pages
2590 * Scan all pages in mapping. Check unevictable pages for
2591 * evictability and move them to the appropriate zone lru list.
2593 void scan_mapping_unevictable_pages(struct address_space *mapping)
2595 pgoff_t next = 0;
2596 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2597 PAGE_CACHE_SHIFT;
2598 struct zone *zone;
2599 struct pagevec pvec;
2601 if (mapping->nrpages == 0)
2602 return;
2604 pagevec_init(&pvec, 0);
2605 while (next < end &&
2606 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2607 int i;
2608 int pg_scanned = 0;
2610 zone = NULL;
2612 for (i = 0; i < pagevec_count(&pvec); i++) {
2613 struct page *page = pvec.pages[i];
2614 pgoff_t page_index = page->index;
2615 struct zone *pagezone = page_zone(page);
2617 pg_scanned++;
2618 if (page_index > next)
2619 next = page_index;
2620 next++;
2622 if (pagezone != zone) {
2623 if (zone)
2624 spin_unlock_irq(&zone->lru_lock);
2625 zone = pagezone;
2626 spin_lock_irq(&zone->lru_lock);
2629 if (PageLRU(page) && PageUnevictable(page))
2630 check_move_unevictable_page(page, zone);
2632 if (zone)
2633 spin_unlock_irq(&zone->lru_lock);
2634 pagevec_release(&pvec);
2636 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2642 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2643 * @zone - zone of which to scan the unevictable list
2645 * Scan @zone's unevictable LRU lists to check for pages that have become
2646 * evictable. Move those that have to @zone's inactive list where they
2647 * become candidates for reclaim, unless shrink_inactive_zone() decides
2648 * to reactivate them. Pages that are still unevictable are rotated
2649 * back onto @zone's unevictable list.
2651 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2652 static void scan_zone_unevictable_pages(struct zone *zone)
2654 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2655 unsigned long scan;
2656 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2658 while (nr_to_scan > 0) {
2659 unsigned long batch_size = min(nr_to_scan,
2660 SCAN_UNEVICTABLE_BATCH_SIZE);
2662 spin_lock_irq(&zone->lru_lock);
2663 for (scan = 0; scan < batch_size; scan++) {
2664 struct page *page = lru_to_page(l_unevictable);
2666 if (!trylock_page(page))
2667 continue;
2669 prefetchw_prev_lru_page(page, l_unevictable, flags);
2671 if (likely(PageLRU(page) && PageUnevictable(page)))
2672 check_move_unevictable_page(page, zone);
2674 unlock_page(page);
2676 spin_unlock_irq(&zone->lru_lock);
2678 nr_to_scan -= batch_size;
2684 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2686 * A really big hammer: scan all zones' unevictable LRU lists to check for
2687 * pages that have become evictable. Move those back to the zones'
2688 * inactive list where they become candidates for reclaim.
2689 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2690 * and we add swap to the system. As such, it runs in the context of a task
2691 * that has possibly/probably made some previously unevictable pages
2692 * evictable.
2694 static void scan_all_zones_unevictable_pages(void)
2696 struct zone *zone;
2698 for_each_zone(zone) {
2699 scan_zone_unevictable_pages(zone);
2704 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2705 * all nodes' unevictable lists for evictable pages
2707 unsigned long scan_unevictable_pages;
2709 int scan_unevictable_handler(struct ctl_table *table, int write,
2710 struct file *file, void __user *buffer,
2711 size_t *length, loff_t *ppos)
2713 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2715 if (write && *(unsigned long *)table->data)
2716 scan_all_zones_unevictable_pages();
2718 scan_unevictable_pages = 0;
2719 return 0;
2723 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2724 * a specified node's per zone unevictable lists for evictable pages.
2727 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2728 struct sysdev_attribute *attr,
2729 char *buf)
2731 return sprintf(buf, "0\n"); /* always zero; should fit... */
2734 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2735 struct sysdev_attribute *attr,
2736 const char *buf, size_t count)
2738 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2739 struct zone *zone;
2740 unsigned long res;
2741 unsigned long req = strict_strtoul(buf, 10, &res);
2743 if (!req)
2744 return 1; /* zero is no-op */
2746 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2747 if (!populated_zone(zone))
2748 continue;
2749 scan_zone_unevictable_pages(zone);
2751 return 1;
2755 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2756 read_scan_unevictable_node,
2757 write_scan_unevictable_node);
2759 int scan_unevictable_register_node(struct node *node)
2761 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2764 void scan_unevictable_unregister_node(struct node *node)
2766 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);