[patch] remove gendisk->stamp_idle field
[linux-2.6.22.y-op.git] / mm / vmscan.c
blob64f9570cff568103c8031706322c0e78b8f93029
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/file.h>
23 #include <linux/writeback.h>
24 #include <linux/blkdev.h>
25 #include <linux/buffer_head.h> /* for try_to_release_page(),
26 buffer_heads_over_limit */
27 #include <linux/mm_inline.h>
28 #include <linux/pagevec.h>
29 #include <linux/backing-dev.h>
30 #include <linux/rmap.h>
31 #include <linux/topology.h>
32 #include <linux/cpu.h>
33 #include <linux/cpuset.h>
34 #include <linux/notifier.h>
35 #include <linux/rwsem.h>
37 #include <asm/tlbflush.h>
38 #include <asm/div64.h>
40 #include <linux/swapops.h>
42 /* possible outcome of pageout() */
43 typedef enum {
44 /* failed to write page out, page is locked */
45 PAGE_KEEP,
46 /* move page to the active list, page is locked */
47 PAGE_ACTIVATE,
48 /* page has been sent to the disk successfully, page is unlocked */
49 PAGE_SUCCESS,
50 /* page is clean and locked */
51 PAGE_CLEAN,
52 } pageout_t;
54 struct scan_control {
55 /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
56 unsigned long nr_to_scan;
58 /* Incremented by the number of inactive pages that were scanned */
59 unsigned long nr_scanned;
61 /* Incremented by the number of pages reclaimed */
62 unsigned long nr_reclaimed;
64 unsigned long nr_mapped; /* From page_state */
66 /* How many pages shrink_cache() should reclaim */
67 int nr_to_reclaim;
69 /* Ask shrink_caches, or shrink_zone to scan at this priority */
70 unsigned int priority;
72 /* This context's GFP mask */
73 unsigned int gfp_mask;
75 int may_writepage;
77 /* Can pages be swapped as part of reclaim? */
78 int may_swap;
80 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
81 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
82 * In this context, it doesn't matter that we scan the
83 * whole list at once. */
84 int swap_cluster_max;
88 * The list of shrinker callbacks used by to apply pressure to
89 * ageable caches.
91 struct shrinker {
92 shrinker_t shrinker;
93 struct list_head list;
94 int seeks; /* seeks to recreate an obj */
95 long nr; /* objs pending delete */
98 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
100 #ifdef ARCH_HAS_PREFETCH
101 #define prefetch_prev_lru_page(_page, _base, _field) \
102 do { \
103 if ((_page)->lru.prev != _base) { \
104 struct page *prev; \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetch(&prev->_field); \
109 } while (0)
110 #else
111 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
112 #endif
114 #ifdef ARCH_HAS_PREFETCHW
115 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 do { \
117 if ((_page)->lru.prev != _base) { \
118 struct page *prev; \
120 prev = lru_to_page(&(_page->lru)); \
121 prefetchw(&prev->_field); \
123 } while (0)
124 #else
125 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
126 #endif
129 * From 0 .. 100. Higher means more swappy.
131 int vm_swappiness = 60;
132 static long total_memory;
134 static LIST_HEAD(shrinker_list);
135 static DECLARE_RWSEM(shrinker_rwsem);
138 * Add a shrinker callback to be called from the vm
140 struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
142 struct shrinker *shrinker;
144 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
145 if (shrinker) {
146 shrinker->shrinker = theshrinker;
147 shrinker->seeks = seeks;
148 shrinker->nr = 0;
149 down_write(&shrinker_rwsem);
150 list_add_tail(&shrinker->list, &shrinker_list);
151 up_write(&shrinker_rwsem);
153 return shrinker;
155 EXPORT_SYMBOL(set_shrinker);
158 * Remove one
160 void remove_shrinker(struct shrinker *shrinker)
162 down_write(&shrinker_rwsem);
163 list_del(&shrinker->list);
164 up_write(&shrinker_rwsem);
165 kfree(shrinker);
167 EXPORT_SYMBOL(remove_shrinker);
169 #define SHRINK_BATCH 128
171 * Call the shrink functions to age shrinkable caches
173 * Here we assume it costs one seek to replace a lru page and that it also
174 * takes a seek to recreate a cache object. With this in mind we age equal
175 * percentages of the lru and ageable caches. This should balance the seeks
176 * generated by these structures.
178 * If the vm encounted mapped pages on the LRU it increase the pressure on
179 * slab to avoid swapping.
181 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
183 * `lru_pages' represents the number of on-LRU pages in all the zones which
184 * are eligible for the caller's allocation attempt. It is used for balancing
185 * slab reclaim versus page reclaim.
187 * Returns the number of slab objects which we shrunk.
189 static int shrink_slab(unsigned long scanned, unsigned int gfp_mask,
190 unsigned long lru_pages)
192 struct shrinker *shrinker;
193 int ret = 0;
195 if (scanned == 0)
196 scanned = SWAP_CLUSTER_MAX;
198 if (!down_read_trylock(&shrinker_rwsem))
199 return 1; /* Assume we'll be able to shrink next time */
201 list_for_each_entry(shrinker, &shrinker_list, list) {
202 unsigned long long delta;
203 unsigned long total_scan;
205 delta = (4 * scanned) / shrinker->seeks;
206 delta *= (*shrinker->shrinker)(0, gfp_mask);
207 do_div(delta, lru_pages + 1);
208 shrinker->nr += delta;
209 if (shrinker->nr < 0)
210 shrinker->nr = LONG_MAX; /* It wrapped! */
212 total_scan = shrinker->nr;
213 shrinker->nr = 0;
215 while (total_scan >= SHRINK_BATCH) {
216 long this_scan = SHRINK_BATCH;
217 int shrink_ret;
218 int nr_before;
220 nr_before = (*shrinker->shrinker)(0, gfp_mask);
221 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
222 if (shrink_ret == -1)
223 break;
224 if (shrink_ret < nr_before)
225 ret += nr_before - shrink_ret;
226 mod_page_state(slabs_scanned, this_scan);
227 total_scan -= this_scan;
229 cond_resched();
232 shrinker->nr += total_scan;
234 up_read(&shrinker_rwsem);
235 return ret;
238 /* Called without lock on whether page is mapped, so answer is unstable */
239 static inline int page_mapping_inuse(struct page *page)
241 struct address_space *mapping;
243 /* Page is in somebody's page tables. */
244 if (page_mapped(page))
245 return 1;
247 /* Be more reluctant to reclaim swapcache than pagecache */
248 if (PageSwapCache(page))
249 return 1;
251 mapping = page_mapping(page);
252 if (!mapping)
253 return 0;
255 /* File is mmap'd by somebody? */
256 return mapping_mapped(mapping);
259 static inline int is_page_cache_freeable(struct page *page)
261 return page_count(page) - !!PagePrivate(page) == 2;
264 static int may_write_to_queue(struct backing_dev_info *bdi)
266 if (current_is_kswapd())
267 return 1;
268 if (current_is_pdflush()) /* This is unlikely, but why not... */
269 return 1;
270 if (!bdi_write_congested(bdi))
271 return 1;
272 if (bdi == current->backing_dev_info)
273 return 1;
274 return 0;
278 * We detected a synchronous write error writing a page out. Probably
279 * -ENOSPC. We need to propagate that into the address_space for a subsequent
280 * fsync(), msync() or close().
282 * The tricky part is that after writepage we cannot touch the mapping: nothing
283 * prevents it from being freed up. But we have a ref on the page and once
284 * that page is locked, the mapping is pinned.
286 * We're allowed to run sleeping lock_page() here because we know the caller has
287 * __GFP_FS.
289 static void handle_write_error(struct address_space *mapping,
290 struct page *page, int error)
292 lock_page(page);
293 if (page_mapping(page) == mapping) {
294 if (error == -ENOSPC)
295 set_bit(AS_ENOSPC, &mapping->flags);
296 else
297 set_bit(AS_EIO, &mapping->flags);
299 unlock_page(page);
303 * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
305 static pageout_t pageout(struct page *page, struct address_space *mapping)
308 * If the page is dirty, only perform writeback if that write
309 * will be non-blocking. To prevent this allocation from being
310 * stalled by pagecache activity. But note that there may be
311 * stalls if we need to run get_block(). We could test
312 * PagePrivate for that.
314 * If this process is currently in generic_file_write() against
315 * this page's queue, we can perform writeback even if that
316 * will block.
318 * If the page is swapcache, write it back even if that would
319 * block, for some throttling. This happens by accident, because
320 * swap_backing_dev_info is bust: it doesn't reflect the
321 * congestion state of the swapdevs. Easy to fix, if needed.
322 * See swapfile.c:page_queue_congested().
324 if (!is_page_cache_freeable(page))
325 return PAGE_KEEP;
326 if (!mapping) {
328 * Some data journaling orphaned pages can have
329 * page->mapping == NULL while being dirty with clean buffers.
331 if (PagePrivate(page)) {
332 if (try_to_free_buffers(page)) {
333 ClearPageDirty(page);
334 printk("%s: orphaned page\n", __FUNCTION__);
335 return PAGE_CLEAN;
338 return PAGE_KEEP;
340 if (mapping->a_ops->writepage == NULL)
341 return PAGE_ACTIVATE;
342 if (!may_write_to_queue(mapping->backing_dev_info))
343 return PAGE_KEEP;
345 if (clear_page_dirty_for_io(page)) {
346 int res;
347 struct writeback_control wbc = {
348 .sync_mode = WB_SYNC_NONE,
349 .nr_to_write = SWAP_CLUSTER_MAX,
350 .nonblocking = 1,
351 .for_reclaim = 1,
354 SetPageReclaim(page);
355 res = mapping->a_ops->writepage(page, &wbc);
356 if (res < 0)
357 handle_write_error(mapping, page, res);
358 if (res == WRITEPAGE_ACTIVATE) {
359 ClearPageReclaim(page);
360 return PAGE_ACTIVATE;
362 if (!PageWriteback(page)) {
363 /* synchronous write or broken a_ops? */
364 ClearPageReclaim(page);
367 return PAGE_SUCCESS;
370 return PAGE_CLEAN;
374 * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
376 static int shrink_list(struct list_head *page_list, struct scan_control *sc)
378 LIST_HEAD(ret_pages);
379 struct pagevec freed_pvec;
380 int pgactivate = 0;
381 int reclaimed = 0;
383 cond_resched();
385 pagevec_init(&freed_pvec, 1);
386 while (!list_empty(page_list)) {
387 struct address_space *mapping;
388 struct page *page;
389 int may_enter_fs;
390 int referenced;
392 cond_resched();
394 page = lru_to_page(page_list);
395 list_del(&page->lru);
397 if (TestSetPageLocked(page))
398 goto keep;
400 BUG_ON(PageActive(page));
402 sc->nr_scanned++;
403 /* Double the slab pressure for mapped and swapcache pages */
404 if (page_mapped(page) || PageSwapCache(page))
405 sc->nr_scanned++;
407 if (PageWriteback(page))
408 goto keep_locked;
410 referenced = page_referenced(page, 1, sc->priority <= 0);
411 /* In active use or really unfreeable? Activate it. */
412 if (referenced && page_mapping_inuse(page))
413 goto activate_locked;
415 #ifdef CONFIG_SWAP
417 * Anonymous process memory has backing store?
418 * Try to allocate it some swap space here.
420 if (PageAnon(page) && !PageSwapCache(page) && sc->may_swap) {
421 if (!add_to_swap(page))
422 goto activate_locked;
424 #endif /* CONFIG_SWAP */
426 mapping = page_mapping(page);
427 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
428 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
431 * The page is mapped into the page tables of one or more
432 * processes. Try to unmap it here.
434 if (page_mapped(page) && mapping) {
435 switch (try_to_unmap(page)) {
436 case SWAP_FAIL:
437 goto activate_locked;
438 case SWAP_AGAIN:
439 goto keep_locked;
440 case SWAP_SUCCESS:
441 ; /* try to free the page below */
445 if (PageDirty(page)) {
446 if (referenced)
447 goto keep_locked;
448 if (!may_enter_fs)
449 goto keep_locked;
450 if (laptop_mode && !sc->may_writepage)
451 goto keep_locked;
453 /* Page is dirty, try to write it out here */
454 switch(pageout(page, mapping)) {
455 case PAGE_KEEP:
456 goto keep_locked;
457 case PAGE_ACTIVATE:
458 goto activate_locked;
459 case PAGE_SUCCESS:
460 if (PageWriteback(page) || PageDirty(page))
461 goto keep;
463 * A synchronous write - probably a ramdisk. Go
464 * ahead and try to reclaim the page.
466 if (TestSetPageLocked(page))
467 goto keep;
468 if (PageDirty(page) || PageWriteback(page))
469 goto keep_locked;
470 mapping = page_mapping(page);
471 case PAGE_CLEAN:
472 ; /* try to free the page below */
477 * If the page has buffers, try to free the buffer mappings
478 * associated with this page. If we succeed we try to free
479 * the page as well.
481 * We do this even if the page is PageDirty().
482 * try_to_release_page() does not perform I/O, but it is
483 * possible for a page to have PageDirty set, but it is actually
484 * clean (all its buffers are clean). This happens if the
485 * buffers were written out directly, with submit_bh(). ext3
486 * will do this, as well as the blockdev mapping.
487 * try_to_release_page() will discover that cleanness and will
488 * drop the buffers and mark the page clean - it can be freed.
490 * Rarely, pages can have buffers and no ->mapping. These are
491 * the pages which were not successfully invalidated in
492 * truncate_complete_page(). We try to drop those buffers here
493 * and if that worked, and the page is no longer mapped into
494 * process address space (page_count == 1) it can be freed.
495 * Otherwise, leave the page on the LRU so it is swappable.
497 if (PagePrivate(page)) {
498 if (!try_to_release_page(page, sc->gfp_mask))
499 goto activate_locked;
500 if (!mapping && page_count(page) == 1)
501 goto free_it;
504 if (!mapping)
505 goto keep_locked; /* truncate got there first */
507 write_lock_irq(&mapping->tree_lock);
510 * The non-racy check for busy page. It is critical to check
511 * PageDirty _after_ making sure that the page is freeable and
512 * not in use by anybody. (pagecache + us == 2)
514 if (unlikely(page_count(page) != 2))
515 goto cannot_free;
516 smp_rmb();
517 if (unlikely(PageDirty(page)))
518 goto cannot_free;
520 #ifdef CONFIG_SWAP
521 if (PageSwapCache(page)) {
522 swp_entry_t swap = { .val = page->private };
523 __delete_from_swap_cache(page);
524 write_unlock_irq(&mapping->tree_lock);
525 swap_free(swap);
526 __put_page(page); /* The pagecache ref */
527 goto free_it;
529 #endif /* CONFIG_SWAP */
531 __remove_from_page_cache(page);
532 write_unlock_irq(&mapping->tree_lock);
533 __put_page(page);
535 free_it:
536 unlock_page(page);
537 reclaimed++;
538 if (!pagevec_add(&freed_pvec, page))
539 __pagevec_release_nonlru(&freed_pvec);
540 continue;
542 cannot_free:
543 write_unlock_irq(&mapping->tree_lock);
544 goto keep_locked;
546 activate_locked:
547 SetPageActive(page);
548 pgactivate++;
549 keep_locked:
550 unlock_page(page);
551 keep:
552 list_add(&page->lru, &ret_pages);
553 BUG_ON(PageLRU(page));
555 list_splice(&ret_pages, page_list);
556 if (pagevec_count(&freed_pvec))
557 __pagevec_release_nonlru(&freed_pvec);
558 mod_page_state(pgactivate, pgactivate);
559 sc->nr_reclaimed += reclaimed;
560 return reclaimed;
564 * zone->lru_lock is heavily contended. Some of the functions that
565 * shrink the lists perform better by taking out a batch of pages
566 * and working on them outside the LRU lock.
568 * For pagecache intensive workloads, this function is the hottest
569 * spot in the kernel (apart from copy_*_user functions).
571 * Appropriate locks must be held before calling this function.
573 * @nr_to_scan: The number of pages to look through on the list.
574 * @src: The LRU list to pull pages off.
575 * @dst: The temp list to put pages on to.
576 * @scanned: The number of pages that were scanned.
578 * returns how many pages were moved onto *@dst.
580 static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
581 struct list_head *dst, int *scanned)
583 int nr_taken = 0;
584 struct page *page;
585 int scan = 0;
587 while (scan++ < nr_to_scan && !list_empty(src)) {
588 page = lru_to_page(src);
589 prefetchw_prev_lru_page(page, src, flags);
591 if (!TestClearPageLRU(page))
592 BUG();
593 list_del(&page->lru);
594 if (get_page_testone(page)) {
596 * It is being freed elsewhere
598 __put_page(page);
599 SetPageLRU(page);
600 list_add(&page->lru, src);
601 continue;
602 } else {
603 list_add(&page->lru, dst);
604 nr_taken++;
608 *scanned = scan;
609 return nr_taken;
613 * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
615 static void shrink_cache(struct zone *zone, struct scan_control *sc)
617 LIST_HEAD(page_list);
618 struct pagevec pvec;
619 int max_scan = sc->nr_to_scan;
621 pagevec_init(&pvec, 1);
623 lru_add_drain();
624 spin_lock_irq(&zone->lru_lock);
625 while (max_scan > 0) {
626 struct page *page;
627 int nr_taken;
628 int nr_scan;
629 int nr_freed;
631 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
632 &zone->inactive_list,
633 &page_list, &nr_scan);
634 zone->nr_inactive -= nr_taken;
635 zone->pages_scanned += nr_scan;
636 spin_unlock_irq(&zone->lru_lock);
638 if (nr_taken == 0)
639 goto done;
641 max_scan -= nr_scan;
642 if (current_is_kswapd())
643 mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
644 else
645 mod_page_state_zone(zone, pgscan_direct, nr_scan);
646 nr_freed = shrink_list(&page_list, sc);
647 if (current_is_kswapd())
648 mod_page_state(kswapd_steal, nr_freed);
649 mod_page_state_zone(zone, pgsteal, nr_freed);
650 sc->nr_to_reclaim -= nr_freed;
652 spin_lock_irq(&zone->lru_lock);
654 * Put back any unfreeable pages.
656 while (!list_empty(&page_list)) {
657 page = lru_to_page(&page_list);
658 if (TestSetPageLRU(page))
659 BUG();
660 list_del(&page->lru);
661 if (PageActive(page))
662 add_page_to_active_list(zone, page);
663 else
664 add_page_to_inactive_list(zone, page);
665 if (!pagevec_add(&pvec, page)) {
666 spin_unlock_irq(&zone->lru_lock);
667 __pagevec_release(&pvec);
668 spin_lock_irq(&zone->lru_lock);
672 spin_unlock_irq(&zone->lru_lock);
673 done:
674 pagevec_release(&pvec);
678 * This moves pages from the active list to the inactive list.
680 * We move them the other way if the page is referenced by one or more
681 * processes, from rmap.
683 * If the pages are mostly unmapped, the processing is fast and it is
684 * appropriate to hold zone->lru_lock across the whole operation. But if
685 * the pages are mapped, the processing is slow (page_referenced()) so we
686 * should drop zone->lru_lock around each page. It's impossible to balance
687 * this, so instead we remove the pages from the LRU while processing them.
688 * It is safe to rely on PG_active against the non-LRU pages in here because
689 * nobody will play with that bit on a non-LRU page.
691 * The downside is that we have to touch page->_count against each page.
692 * But we had to alter page->flags anyway.
694 static void
695 refill_inactive_zone(struct zone *zone, struct scan_control *sc)
697 int pgmoved;
698 int pgdeactivate = 0;
699 int pgscanned;
700 int nr_pages = sc->nr_to_scan;
701 LIST_HEAD(l_hold); /* The pages which were snipped off */
702 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
703 LIST_HEAD(l_active); /* Pages to go onto the active_list */
704 struct page *page;
705 struct pagevec pvec;
706 int reclaim_mapped = 0;
707 long mapped_ratio;
708 long distress;
709 long swap_tendency;
711 lru_add_drain();
712 spin_lock_irq(&zone->lru_lock);
713 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
714 &l_hold, &pgscanned);
715 zone->pages_scanned += pgscanned;
716 zone->nr_active -= pgmoved;
717 spin_unlock_irq(&zone->lru_lock);
720 * `distress' is a measure of how much trouble we're having reclaiming
721 * pages. 0 -> no problems. 100 -> great trouble.
723 distress = 100 >> zone->prev_priority;
726 * The point of this algorithm is to decide when to start reclaiming
727 * mapped memory instead of just pagecache. Work out how much memory
728 * is mapped.
730 mapped_ratio = (sc->nr_mapped * 100) / total_memory;
733 * Now decide how much we really want to unmap some pages. The mapped
734 * ratio is downgraded - just because there's a lot of mapped memory
735 * doesn't necessarily mean that page reclaim isn't succeeding.
737 * The distress ratio is important - we don't want to start going oom.
739 * A 100% value of vm_swappiness overrides this algorithm altogether.
741 swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
744 * Now use this metric to decide whether to start moving mapped memory
745 * onto the inactive list.
747 if (swap_tendency >= 100)
748 reclaim_mapped = 1;
750 while (!list_empty(&l_hold)) {
751 cond_resched();
752 page = lru_to_page(&l_hold);
753 list_del(&page->lru);
754 if (page_mapped(page)) {
755 if (!reclaim_mapped ||
756 (total_swap_pages == 0 && PageAnon(page)) ||
757 page_referenced(page, 0, sc->priority <= 0)) {
758 list_add(&page->lru, &l_active);
759 continue;
762 list_add(&page->lru, &l_inactive);
765 pagevec_init(&pvec, 1);
766 pgmoved = 0;
767 spin_lock_irq(&zone->lru_lock);
768 while (!list_empty(&l_inactive)) {
769 page = lru_to_page(&l_inactive);
770 prefetchw_prev_lru_page(page, &l_inactive, flags);
771 if (TestSetPageLRU(page))
772 BUG();
773 if (!TestClearPageActive(page))
774 BUG();
775 list_move(&page->lru, &zone->inactive_list);
776 pgmoved++;
777 if (!pagevec_add(&pvec, page)) {
778 zone->nr_inactive += pgmoved;
779 spin_unlock_irq(&zone->lru_lock);
780 pgdeactivate += pgmoved;
781 pgmoved = 0;
782 if (buffer_heads_over_limit)
783 pagevec_strip(&pvec);
784 __pagevec_release(&pvec);
785 spin_lock_irq(&zone->lru_lock);
788 zone->nr_inactive += pgmoved;
789 pgdeactivate += pgmoved;
790 if (buffer_heads_over_limit) {
791 spin_unlock_irq(&zone->lru_lock);
792 pagevec_strip(&pvec);
793 spin_lock_irq(&zone->lru_lock);
796 pgmoved = 0;
797 while (!list_empty(&l_active)) {
798 page = lru_to_page(&l_active);
799 prefetchw_prev_lru_page(page, &l_active, flags);
800 if (TestSetPageLRU(page))
801 BUG();
802 BUG_ON(!PageActive(page));
803 list_move(&page->lru, &zone->active_list);
804 pgmoved++;
805 if (!pagevec_add(&pvec, page)) {
806 zone->nr_active += pgmoved;
807 pgmoved = 0;
808 spin_unlock_irq(&zone->lru_lock);
809 __pagevec_release(&pvec);
810 spin_lock_irq(&zone->lru_lock);
813 zone->nr_active += pgmoved;
814 spin_unlock_irq(&zone->lru_lock);
815 pagevec_release(&pvec);
817 mod_page_state_zone(zone, pgrefill, pgscanned);
818 mod_page_state(pgdeactivate, pgdeactivate);
822 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
824 static void
825 shrink_zone(struct zone *zone, struct scan_control *sc)
827 unsigned long nr_active;
828 unsigned long nr_inactive;
830 atomic_inc(&zone->reclaim_in_progress);
833 * Add one to `nr_to_scan' just to make sure that the kernel will
834 * slowly sift through the active list.
836 zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
837 nr_active = zone->nr_scan_active;
838 if (nr_active >= sc->swap_cluster_max)
839 zone->nr_scan_active = 0;
840 else
841 nr_active = 0;
843 zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
844 nr_inactive = zone->nr_scan_inactive;
845 if (nr_inactive >= sc->swap_cluster_max)
846 zone->nr_scan_inactive = 0;
847 else
848 nr_inactive = 0;
850 sc->nr_to_reclaim = sc->swap_cluster_max;
852 while (nr_active || nr_inactive) {
853 if (nr_active) {
854 sc->nr_to_scan = min(nr_active,
855 (unsigned long)sc->swap_cluster_max);
856 nr_active -= sc->nr_to_scan;
857 refill_inactive_zone(zone, sc);
860 if (nr_inactive) {
861 sc->nr_to_scan = min(nr_inactive,
862 (unsigned long)sc->swap_cluster_max);
863 nr_inactive -= sc->nr_to_scan;
864 shrink_cache(zone, sc);
865 if (sc->nr_to_reclaim <= 0)
866 break;
870 throttle_vm_writeout();
872 atomic_dec(&zone->reclaim_in_progress);
876 * This is the direct reclaim path, for page-allocating processes. We only
877 * try to reclaim pages from zones which will satisfy the caller's allocation
878 * request.
880 * We reclaim from a zone even if that zone is over pages_high. Because:
881 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
882 * allocation or
883 * b) The zones may be over pages_high but they must go *over* pages_high to
884 * satisfy the `incremental min' zone defense algorithm.
886 * Returns the number of reclaimed pages.
888 * If a zone is deemed to be full of pinned pages then just give it a light
889 * scan then give up on it.
891 static void
892 shrink_caches(struct zone **zones, struct scan_control *sc)
894 int i;
896 for (i = 0; zones[i] != NULL; i++) {
897 struct zone *zone = zones[i];
899 if (zone->present_pages == 0)
900 continue;
902 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
903 continue;
905 zone->temp_priority = sc->priority;
906 if (zone->prev_priority > sc->priority)
907 zone->prev_priority = sc->priority;
909 if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
910 continue; /* Let kswapd poll it */
912 shrink_zone(zone, sc);
917 * This is the main entry point to direct page reclaim.
919 * If a full scan of the inactive list fails to free enough memory then we
920 * are "out of memory" and something needs to be killed.
922 * If the caller is !__GFP_FS then the probability of a failure is reasonably
923 * high - the zone may be full of dirty or under-writeback pages, which this
924 * caller can't do much about. We kick pdflush and take explicit naps in the
925 * hope that some of these pages can be written. But if the allocating task
926 * holds filesystem locks which prevent writeout this might not work, and the
927 * allocation attempt will fail.
929 int try_to_free_pages(struct zone **zones, unsigned int gfp_mask)
931 int priority;
932 int ret = 0;
933 int total_scanned = 0, total_reclaimed = 0;
934 struct reclaim_state *reclaim_state = current->reclaim_state;
935 struct scan_control sc;
936 unsigned long lru_pages = 0;
937 int i;
939 sc.gfp_mask = gfp_mask;
940 sc.may_writepage = 0;
941 sc.may_swap = 1;
943 inc_page_state(allocstall);
945 for (i = 0; zones[i] != NULL; i++) {
946 struct zone *zone = zones[i];
948 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
949 continue;
951 zone->temp_priority = DEF_PRIORITY;
952 lru_pages += zone->nr_active + zone->nr_inactive;
955 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
956 sc.nr_mapped = read_page_state(nr_mapped);
957 sc.nr_scanned = 0;
958 sc.nr_reclaimed = 0;
959 sc.priority = priority;
960 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
961 shrink_caches(zones, &sc);
962 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
963 if (reclaim_state) {
964 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
965 reclaim_state->reclaimed_slab = 0;
967 total_scanned += sc.nr_scanned;
968 total_reclaimed += sc.nr_reclaimed;
969 if (total_reclaimed >= sc.swap_cluster_max) {
970 ret = 1;
971 goto out;
975 * Try to write back as many pages as we just scanned. This
976 * tends to cause slow streaming writers to write data to the
977 * disk smoothly, at the dirtying rate, which is nice. But
978 * that's undesirable in laptop mode, where we *want* lumpy
979 * writeout. So in laptop mode, write out the whole world.
981 if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
982 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
983 sc.may_writepage = 1;
986 /* Take a nap, wait for some writeback to complete */
987 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
988 blk_congestion_wait(WRITE, HZ/10);
990 out:
991 for (i = 0; zones[i] != 0; i++) {
992 struct zone *zone = zones[i];
994 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
995 continue;
997 zone->prev_priority = zone->temp_priority;
999 return ret;
1003 * For kswapd, balance_pgdat() will work across all this node's zones until
1004 * they are all at pages_high.
1006 * If `nr_pages' is non-zero then it is the number of pages which are to be
1007 * reclaimed, regardless of the zone occupancies. This is a software suspend
1008 * special.
1010 * Returns the number of pages which were actually freed.
1012 * There is special handling here for zones which are full of pinned pages.
1013 * This can happen if the pages are all mlocked, or if they are all used by
1014 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1015 * What we do is to detect the case where all pages in the zone have been
1016 * scanned twice and there has been zero successful reclaim. Mark the zone as
1017 * dead and from now on, only perform a short scan. Basically we're polling
1018 * the zone for when the problem goes away.
1020 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1021 * zones which have free_pages > pages_high, but once a zone is found to have
1022 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1023 * of the number of free pages in the lower zones. This interoperates with
1024 * the page allocator fallback scheme to ensure that aging of pages is balanced
1025 * across the zones.
1027 static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
1029 int to_free = nr_pages;
1030 int all_zones_ok;
1031 int priority;
1032 int i;
1033 int total_scanned, total_reclaimed;
1034 struct reclaim_state *reclaim_state = current->reclaim_state;
1035 struct scan_control sc;
1037 loop_again:
1038 total_scanned = 0;
1039 total_reclaimed = 0;
1040 sc.gfp_mask = GFP_KERNEL;
1041 sc.may_writepage = 0;
1042 sc.may_swap = 1;
1043 sc.nr_mapped = read_page_state(nr_mapped);
1045 inc_page_state(pageoutrun);
1047 for (i = 0; i < pgdat->nr_zones; i++) {
1048 struct zone *zone = pgdat->node_zones + i;
1050 zone->temp_priority = DEF_PRIORITY;
1053 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1054 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1055 unsigned long lru_pages = 0;
1057 all_zones_ok = 1;
1059 if (nr_pages == 0) {
1061 * Scan in the highmem->dma direction for the highest
1062 * zone which needs scanning
1064 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1065 struct zone *zone = pgdat->node_zones + i;
1067 if (zone->present_pages == 0)
1068 continue;
1070 if (zone->all_unreclaimable &&
1071 priority != DEF_PRIORITY)
1072 continue;
1074 if (!zone_watermark_ok(zone, order,
1075 zone->pages_high, 0, 0, 0)) {
1076 end_zone = i;
1077 goto scan;
1080 goto out;
1081 } else {
1082 end_zone = pgdat->nr_zones - 1;
1084 scan:
1085 for (i = 0; i <= end_zone; i++) {
1086 struct zone *zone = pgdat->node_zones + i;
1088 lru_pages += zone->nr_active + zone->nr_inactive;
1092 * Now scan the zone in the dma->highmem direction, stopping
1093 * at the last zone which needs scanning.
1095 * We do this because the page allocator works in the opposite
1096 * direction. This prevents the page allocator from allocating
1097 * pages behind kswapd's direction of progress, which would
1098 * cause too much scanning of the lower zones.
1100 for (i = 0; i <= end_zone; i++) {
1101 struct zone *zone = pgdat->node_zones + i;
1102 int nr_slab;
1104 if (zone->present_pages == 0)
1105 continue;
1107 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1108 continue;
1110 if (nr_pages == 0) { /* Not software suspend */
1111 if (!zone_watermark_ok(zone, order,
1112 zone->pages_high, end_zone, 0, 0))
1113 all_zones_ok = 0;
1115 zone->temp_priority = priority;
1116 if (zone->prev_priority > priority)
1117 zone->prev_priority = priority;
1118 sc.nr_scanned = 0;
1119 sc.nr_reclaimed = 0;
1120 sc.priority = priority;
1121 sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
1122 atomic_inc(&zone->reclaim_in_progress);
1123 shrink_zone(zone, &sc);
1124 atomic_dec(&zone->reclaim_in_progress);
1125 reclaim_state->reclaimed_slab = 0;
1126 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1127 lru_pages);
1128 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1129 total_reclaimed += sc.nr_reclaimed;
1130 total_scanned += sc.nr_scanned;
1131 if (zone->all_unreclaimable)
1132 continue;
1133 if (nr_slab == 0 && zone->pages_scanned >=
1134 (zone->nr_active + zone->nr_inactive) * 4)
1135 zone->all_unreclaimable = 1;
1137 * If we've done a decent amount of scanning and
1138 * the reclaim ratio is low, start doing writepage
1139 * even in laptop mode
1141 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1142 total_scanned > total_reclaimed+total_reclaimed/2)
1143 sc.may_writepage = 1;
1145 if (nr_pages && to_free > total_reclaimed)
1146 continue; /* swsusp: need to do more work */
1147 if (all_zones_ok)
1148 break; /* kswapd: all done */
1150 * OK, kswapd is getting into trouble. Take a nap, then take
1151 * another pass across the zones.
1153 if (total_scanned && priority < DEF_PRIORITY - 2)
1154 blk_congestion_wait(WRITE, HZ/10);
1157 * We do this so kswapd doesn't build up large priorities for
1158 * example when it is freeing in parallel with allocators. It
1159 * matches the direct reclaim path behaviour in terms of impact
1160 * on zone->*_priority.
1162 if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
1163 break;
1165 out:
1166 for (i = 0; i < pgdat->nr_zones; i++) {
1167 struct zone *zone = pgdat->node_zones + i;
1169 zone->prev_priority = zone->temp_priority;
1171 if (!all_zones_ok) {
1172 cond_resched();
1173 goto loop_again;
1176 return total_reclaimed;
1180 * The background pageout daemon, started as a kernel thread
1181 * from the init process.
1183 * This basically trickles out pages so that we have _some_
1184 * free memory available even if there is no other activity
1185 * that frees anything up. This is needed for things like routing
1186 * etc, where we otherwise might have all activity going on in
1187 * asynchronous contexts that cannot page things out.
1189 * If there are applications that are active memory-allocators
1190 * (most normal use), this basically shouldn't matter.
1192 static int kswapd(void *p)
1194 unsigned long order;
1195 pg_data_t *pgdat = (pg_data_t*)p;
1196 struct task_struct *tsk = current;
1197 DEFINE_WAIT(wait);
1198 struct reclaim_state reclaim_state = {
1199 .reclaimed_slab = 0,
1201 cpumask_t cpumask;
1203 daemonize("kswapd%d", pgdat->node_id);
1204 cpumask = node_to_cpumask(pgdat->node_id);
1205 if (!cpus_empty(cpumask))
1206 set_cpus_allowed(tsk, cpumask);
1207 current->reclaim_state = &reclaim_state;
1210 * Tell the memory management that we're a "memory allocator",
1211 * and that if we need more memory we should get access to it
1212 * regardless (see "__alloc_pages()"). "kswapd" should
1213 * never get caught in the normal page freeing logic.
1215 * (Kswapd normally doesn't need memory anyway, but sometimes
1216 * you need a small amount of memory in order to be able to
1217 * page out something else, and this flag essentially protects
1218 * us from recursively trying to free more memory as we're
1219 * trying to free the first piece of memory in the first place).
1221 tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
1223 order = 0;
1224 for ( ; ; ) {
1225 unsigned long new_order;
1227 try_to_freeze();
1229 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1230 new_order = pgdat->kswapd_max_order;
1231 pgdat->kswapd_max_order = 0;
1232 if (order < new_order) {
1234 * Don't sleep if someone wants a larger 'order'
1235 * allocation
1237 order = new_order;
1238 } else {
1239 schedule();
1240 order = pgdat->kswapd_max_order;
1242 finish_wait(&pgdat->kswapd_wait, &wait);
1244 balance_pgdat(pgdat, 0, order);
1246 return 0;
1250 * A zone is low on free memory, so wake its kswapd task to service it.
1252 void wakeup_kswapd(struct zone *zone, int order)
1254 pg_data_t *pgdat;
1256 if (zone->present_pages == 0)
1257 return;
1259 pgdat = zone->zone_pgdat;
1260 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0, 0))
1261 return;
1262 if (pgdat->kswapd_max_order < order)
1263 pgdat->kswapd_max_order = order;
1264 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
1265 return;
1266 if (!waitqueue_active(&pgdat->kswapd_wait))
1267 return;
1268 wake_up_interruptible(&pgdat->kswapd_wait);
1271 #ifdef CONFIG_PM
1273 * Try to free `nr_pages' of memory, system-wide. Returns the number of freed
1274 * pages.
1276 int shrink_all_memory(int nr_pages)
1278 pg_data_t *pgdat;
1279 int nr_to_free = nr_pages;
1280 int ret = 0;
1281 struct reclaim_state reclaim_state = {
1282 .reclaimed_slab = 0,
1285 current->reclaim_state = &reclaim_state;
1286 for_each_pgdat(pgdat) {
1287 int freed;
1288 freed = balance_pgdat(pgdat, nr_to_free, 0);
1289 ret += freed;
1290 nr_to_free -= freed;
1291 if (nr_to_free <= 0)
1292 break;
1294 current->reclaim_state = NULL;
1295 return ret;
1297 #endif
1299 #ifdef CONFIG_HOTPLUG_CPU
1300 /* It's optimal to keep kswapds on the same CPUs as their memory, but
1301 not required for correctness. So if the last cpu in a node goes
1302 away, we get changed to run anywhere: as the first one comes back,
1303 restore their cpu bindings. */
1304 static int __devinit cpu_callback(struct notifier_block *nfb,
1305 unsigned long action,
1306 void *hcpu)
1308 pg_data_t *pgdat;
1309 cpumask_t mask;
1311 if (action == CPU_ONLINE) {
1312 for_each_pgdat(pgdat) {
1313 mask = node_to_cpumask(pgdat->node_id);
1314 if (any_online_cpu(mask) != NR_CPUS)
1315 /* One of our CPUs online: restore mask */
1316 set_cpus_allowed(pgdat->kswapd, mask);
1319 return NOTIFY_OK;
1321 #endif /* CONFIG_HOTPLUG_CPU */
1323 static int __init kswapd_init(void)
1325 pg_data_t *pgdat;
1326 swap_setup();
1327 for_each_pgdat(pgdat)
1328 pgdat->kswapd
1329 = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
1330 total_memory = nr_free_pagecache_pages();
1331 hotcpu_notifier(cpu_callback, 0);
1332 return 0;
1335 module_init(kswapd_init)
1339 * Try to free up some pages from this zone through reclaim.
1341 int zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
1343 struct scan_control sc;
1344 int nr_pages = 1 << order;
1345 int total_reclaimed = 0;
1347 /* The reclaim may sleep, so don't do it if sleep isn't allowed */
1348 if (!(gfp_mask & __GFP_WAIT))
1349 return 0;
1350 if (zone->all_unreclaimable)
1351 return 0;
1353 sc.gfp_mask = gfp_mask;
1354 sc.may_writepage = 0;
1355 sc.may_swap = 0;
1356 sc.nr_mapped = read_page_state(nr_mapped);
1357 sc.nr_scanned = 0;
1358 sc.nr_reclaimed = 0;
1359 /* scan at the highest priority */
1360 sc.priority = 0;
1362 if (nr_pages > SWAP_CLUSTER_MAX)
1363 sc.swap_cluster_max = nr_pages;
1364 else
1365 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
1367 /* Don't reclaim the zone if there are other reclaimers active */
1368 if (atomic_read(&zone->reclaim_in_progress) > 0)
1369 goto out;
1371 shrink_zone(zone, &sc);
1372 total_reclaimed = sc.nr_reclaimed;
1374 out:
1375 return total_reclaimed;
1378 asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone,
1379 unsigned int state)
1381 struct zone *z;
1382 int i;
1384 if (!capable(CAP_SYS_ADMIN))
1385 return -EACCES;
1387 if (node >= MAX_NUMNODES || !node_online(node))
1388 return -EINVAL;
1390 /* This will break if we ever add more zones */
1391 if (!(zone & (1<<ZONE_DMA|1<<ZONE_NORMAL|1<<ZONE_HIGHMEM)))
1392 return -EINVAL;
1394 for (i = 0; i < MAX_NR_ZONES; i++) {
1395 if (!(zone & 1<<i))
1396 continue;
1398 z = &NODE_DATA(node)->node_zones[i];
1400 if (state)
1401 z->reclaim_pages = 1;
1402 else
1403 z->reclaim_pages = 0;
1406 return 0;