4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * This file contains the default values for the operation of the
9 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
17 #include <linux/sched.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/swap.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/pagevec.h>
23 #include <linux/init.h>
24 #include <linux/export.h>
25 #include <linux/mm_inline.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page() */
27 #include <linux/percpu_counter.h>
28 #include <linux/percpu.h>
29 #include <linux/cpu.h>
30 #include <linux/notifier.h>
31 #include <linux/backing-dev.h>
32 #include <linux/memcontrol.h>
33 #include <linux/gfp.h>
37 /* How many pages do we try to swap or page in/out together? */
40 static DEFINE_PER_CPU(struct pagevec
[NR_LRU_LISTS
], lru_add_pvecs
);
41 static DEFINE_PER_CPU(struct pagevec
, lru_rotate_pvecs
);
42 static DEFINE_PER_CPU(struct pagevec
, lru_deactivate_pvecs
);
45 * This path almost never happens for VM activity - pages are normally
46 * freed via pagevecs. But it gets used by networking.
48 static void __page_cache_release(struct page
*page
)
52 struct zone
*zone
= page_zone(page
);
54 spin_lock_irqsave(&zone
->lru_lock
, flags
);
55 VM_BUG_ON(!PageLRU(page
));
57 del_page_from_lru(zone
, page
);
58 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
62 static void __put_single_page(struct page
*page
)
64 __page_cache_release(page
);
65 free_hot_cold_page(page
, 0);
68 static void __put_compound_page(struct page
*page
)
70 compound_page_dtor
*dtor
;
72 __page_cache_release(page
);
73 dtor
= get_compound_page_dtor(page
);
77 static void put_compound_page(struct page
*page
)
79 if (unlikely(PageTail(page
))) {
80 /* __split_huge_page_refcount can run under us */
81 struct page
*page_head
= compound_trans_head(page
);
83 if (likely(page
!= page_head
&&
84 get_page_unless_zero(page_head
))) {
87 * page_head wasn't a dangling pointer but it
88 * may not be a head page anymore by the time
89 * we obtain the lock. That is ok as long as it
90 * can't be freed from under us.
92 flags
= compound_lock_irqsave(page_head
);
93 if (unlikely(!PageTail(page
))) {
94 /* __split_huge_page_refcount run before us */
95 compound_unlock_irqrestore(page_head
, flags
);
96 VM_BUG_ON(PageHead(page_head
));
97 if (put_page_testzero(page_head
))
98 __put_single_page(page_head
);
100 if (put_page_testzero(page
))
101 __put_single_page(page
);
104 VM_BUG_ON(page_head
!= page
->first_page
);
106 * We can release the refcount taken by
107 * get_page_unless_zero() now that
108 * __split_huge_page_refcount() is blocked on
111 if (put_page_testzero(page_head
))
113 /* __split_huge_page_refcount will wait now */
114 VM_BUG_ON(page_mapcount(page
) <= 0);
115 atomic_dec(&page
->_mapcount
);
116 VM_BUG_ON(atomic_read(&page_head
->_count
) <= 0);
117 VM_BUG_ON(atomic_read(&page
->_count
) != 0);
118 compound_unlock_irqrestore(page_head
, flags
);
119 if (put_page_testzero(page_head
)) {
120 if (PageHead(page_head
))
121 __put_compound_page(page_head
);
123 __put_single_page(page_head
);
126 /* page_head is a dangling pointer */
127 VM_BUG_ON(PageTail(page
));
130 } else if (put_page_testzero(page
)) {
132 __put_compound_page(page
);
134 __put_single_page(page
);
138 void put_page(struct page
*page
)
140 if (unlikely(PageCompound(page
)))
141 put_compound_page(page
);
142 else if (put_page_testzero(page
))
143 __put_single_page(page
);
145 EXPORT_SYMBOL(put_page
);
148 * This function is exported but must not be called by anything other
149 * than get_page(). It implements the slow path of get_page().
151 bool __get_page_tail(struct page
*page
)
154 * This takes care of get_page() if run on a tail page
155 * returned by one of the get_user_pages/follow_page variants.
156 * get_user_pages/follow_page itself doesn't need the compound
157 * lock because it runs __get_page_tail_foll() under the
158 * proper PT lock that already serializes against
163 struct page
*page_head
= compound_trans_head(page
);
165 if (likely(page
!= page_head
&& get_page_unless_zero(page_head
))) {
167 * page_head wasn't a dangling pointer but it
168 * may not be a head page anymore by the time
169 * we obtain the lock. That is ok as long as it
170 * can't be freed from under us.
172 flags
= compound_lock_irqsave(page_head
);
173 /* here __split_huge_page_refcount won't run anymore */
174 if (likely(PageTail(page
))) {
175 __get_page_tail_foll(page
, false);
178 compound_unlock_irqrestore(page_head
, flags
);
184 EXPORT_SYMBOL(__get_page_tail
);
187 * put_pages_list() - release a list of pages
188 * @pages: list of pages threaded on page->lru
190 * Release a list of pages which are strung together on page.lru. Currently
191 * used by read_cache_pages() and related error recovery code.
193 void put_pages_list(struct list_head
*pages
)
195 while (!list_empty(pages
)) {
198 victim
= list_entry(pages
->prev
, struct page
, lru
);
199 list_del(&victim
->lru
);
200 page_cache_release(victim
);
203 EXPORT_SYMBOL(put_pages_list
);
205 static void pagevec_lru_move_fn(struct pagevec
*pvec
,
206 void (*move_fn
)(struct page
*page
, void *arg
),
210 struct zone
*zone
= NULL
;
211 unsigned long flags
= 0;
213 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
214 struct page
*page
= pvec
->pages
[i
];
215 struct zone
*pagezone
= page_zone(page
);
217 if (pagezone
!= zone
) {
219 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
221 spin_lock_irqsave(&zone
->lru_lock
, flags
);
224 (*move_fn
)(page
, arg
);
227 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
228 release_pages(pvec
->pages
, pvec
->nr
, pvec
->cold
);
229 pagevec_reinit(pvec
);
232 static void pagevec_move_tail_fn(struct page
*page
, void *arg
)
236 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
237 enum lru_list lru
= page_lru_base_type(page
);
238 struct lruvec
*lruvec
;
240 lruvec
= mem_cgroup_lru_move_lists(page_zone(page
),
242 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
248 * pagevec_move_tail() must be called with IRQ disabled.
249 * Otherwise this may cause nasty races.
251 static void pagevec_move_tail(struct pagevec
*pvec
)
255 pagevec_lru_move_fn(pvec
, pagevec_move_tail_fn
, &pgmoved
);
256 __count_vm_events(PGROTATED
, pgmoved
);
260 * Writeback is about to end against a page which has been marked for immediate
261 * reclaim. If it still appears to be reclaimable, move it to the tail of the
264 void rotate_reclaimable_page(struct page
*page
)
266 if (!PageLocked(page
) && !PageDirty(page
) && !PageActive(page
) &&
267 !PageUnevictable(page
) && PageLRU(page
)) {
268 struct pagevec
*pvec
;
271 page_cache_get(page
);
272 local_irq_save(flags
);
273 pvec
= &__get_cpu_var(lru_rotate_pvecs
);
274 if (!pagevec_add(pvec
, page
))
275 pagevec_move_tail(pvec
);
276 local_irq_restore(flags
);
280 static void update_page_reclaim_stat(struct zone
*zone
, struct page
*page
,
281 int file
, int rotated
)
283 struct zone_reclaim_stat
*reclaim_stat
= &zone
->reclaim_stat
;
284 struct zone_reclaim_stat
*memcg_reclaim_stat
;
286 memcg_reclaim_stat
= mem_cgroup_get_reclaim_stat_from_page(page
);
288 reclaim_stat
->recent_scanned
[file
]++;
290 reclaim_stat
->recent_rotated
[file
]++;
292 if (!memcg_reclaim_stat
)
295 memcg_reclaim_stat
->recent_scanned
[file
]++;
297 memcg_reclaim_stat
->recent_rotated
[file
]++;
300 static void __activate_page(struct page
*page
, void *arg
)
302 struct zone
*zone
= page_zone(page
);
304 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
305 int file
= page_is_file_cache(page
);
306 int lru
= page_lru_base_type(page
);
307 del_page_from_lru_list(zone
, page
, lru
);
311 add_page_to_lru_list(zone
, page
, lru
);
312 __count_vm_event(PGACTIVATE
);
314 update_page_reclaim_stat(zone
, page
, file
, 1);
319 static DEFINE_PER_CPU(struct pagevec
, activate_page_pvecs
);
321 static void activate_page_drain(int cpu
)
323 struct pagevec
*pvec
= &per_cpu(activate_page_pvecs
, cpu
);
325 if (pagevec_count(pvec
))
326 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
329 void activate_page(struct page
*page
)
331 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
332 struct pagevec
*pvec
= &get_cpu_var(activate_page_pvecs
);
334 page_cache_get(page
);
335 if (!pagevec_add(pvec
, page
))
336 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
337 put_cpu_var(activate_page_pvecs
);
342 static inline void activate_page_drain(int cpu
)
346 void activate_page(struct page
*page
)
348 struct zone
*zone
= page_zone(page
);
350 spin_lock_irq(&zone
->lru_lock
);
351 __activate_page(page
, NULL
);
352 spin_unlock_irq(&zone
->lru_lock
);
357 * Mark a page as having seen activity.
359 * inactive,unreferenced -> inactive,referenced
360 * inactive,referenced -> active,unreferenced
361 * active,unreferenced -> active,referenced
363 void mark_page_accessed(struct page
*page
)
365 if (!PageActive(page
) && !PageUnevictable(page
) &&
366 PageReferenced(page
) && PageLRU(page
)) {
368 ClearPageReferenced(page
);
369 } else if (!PageReferenced(page
)) {
370 SetPageReferenced(page
);
374 EXPORT_SYMBOL(mark_page_accessed
);
376 void __lru_cache_add(struct page
*page
, enum lru_list lru
)
378 struct pagevec
*pvec
= &get_cpu_var(lru_add_pvecs
)[lru
];
380 page_cache_get(page
);
381 if (!pagevec_add(pvec
, page
))
382 ____pagevec_lru_add(pvec
, lru
);
383 put_cpu_var(lru_add_pvecs
);
385 EXPORT_SYMBOL(__lru_cache_add
);
388 * lru_cache_add_lru - add a page to a page list
389 * @page: the page to be added to the LRU.
390 * @lru: the LRU list to which the page is added.
392 void lru_cache_add_lru(struct page
*page
, enum lru_list lru
)
394 if (PageActive(page
)) {
395 VM_BUG_ON(PageUnevictable(page
));
396 ClearPageActive(page
);
397 } else if (PageUnevictable(page
)) {
398 VM_BUG_ON(PageActive(page
));
399 ClearPageUnevictable(page
);
402 VM_BUG_ON(PageLRU(page
) || PageActive(page
) || PageUnevictable(page
));
403 __lru_cache_add(page
, lru
);
407 * add_page_to_unevictable_list - add a page to the unevictable list
408 * @page: the page to be added to the unevictable list
410 * Add page directly to its zone's unevictable list. To avoid races with
411 * tasks that might be making the page evictable, through eg. munlock,
412 * munmap or exit, while it's not on the lru, we want to add the page
413 * while it's locked or otherwise "invisible" to other tasks. This is
414 * difficult to do when using the pagevec cache, so bypass that.
416 void add_page_to_unevictable_list(struct page
*page
)
418 struct zone
*zone
= page_zone(page
);
420 spin_lock_irq(&zone
->lru_lock
);
421 SetPageUnevictable(page
);
423 add_page_to_lru_list(zone
, page
, LRU_UNEVICTABLE
);
424 spin_unlock_irq(&zone
->lru_lock
);
428 * If the page can not be invalidated, it is moved to the
429 * inactive list to speed up its reclaim. It is moved to the
430 * head of the list, rather than the tail, to give the flusher
431 * threads some time to write it out, as this is much more
432 * effective than the single-page writeout from reclaim.
434 * If the page isn't page_mapped and dirty/writeback, the page
435 * could reclaim asap using PG_reclaim.
437 * 1. active, mapped page -> none
438 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
439 * 3. inactive, mapped page -> none
440 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
441 * 5. inactive, clean -> inactive, tail
444 * In 4, why it moves inactive's head, the VM expects the page would
445 * be write it out by flusher threads as this is much more effective
446 * than the single-page writeout from reclaim.
448 static void lru_deactivate_fn(struct page
*page
, void *arg
)
452 struct zone
*zone
= page_zone(page
);
457 if (PageUnevictable(page
))
460 /* Some processes are using the page */
461 if (page_mapped(page
))
464 active
= PageActive(page
);
466 file
= page_is_file_cache(page
);
467 lru
= page_lru_base_type(page
);
468 del_page_from_lru_list(zone
, page
, lru
+ active
);
469 ClearPageActive(page
);
470 ClearPageReferenced(page
);
471 add_page_to_lru_list(zone
, page
, lru
);
473 if (PageWriteback(page
) || PageDirty(page
)) {
475 * PG_reclaim could be raced with end_page_writeback
476 * It can make readahead confusing. But race window
477 * is _really_ small and it's non-critical problem.
479 SetPageReclaim(page
);
481 struct lruvec
*lruvec
;
483 * The page's writeback ends up during pagevec
484 * We moves tha page into tail of inactive.
486 lruvec
= mem_cgroup_lru_move_lists(zone
, page
, lru
, lru
);
487 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
488 __count_vm_event(PGROTATED
);
492 __count_vm_event(PGDEACTIVATE
);
493 update_page_reclaim_stat(zone
, page
, file
, 0);
497 * Drain pages out of the cpu's pagevecs.
498 * Either "cpu" is the current CPU, and preemption has already been
499 * disabled; or "cpu" is being hot-unplugged, and is already dead.
501 static void drain_cpu_pagevecs(int cpu
)
503 struct pagevec
*pvecs
= per_cpu(lru_add_pvecs
, cpu
);
504 struct pagevec
*pvec
;
508 pvec
= &pvecs
[lru
- LRU_BASE
];
509 if (pagevec_count(pvec
))
510 ____pagevec_lru_add(pvec
, lru
);
513 pvec
= &per_cpu(lru_rotate_pvecs
, cpu
);
514 if (pagevec_count(pvec
)) {
517 /* No harm done if a racing interrupt already did this */
518 local_irq_save(flags
);
519 pagevec_move_tail(pvec
);
520 local_irq_restore(flags
);
523 pvec
= &per_cpu(lru_deactivate_pvecs
, cpu
);
524 if (pagevec_count(pvec
))
525 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
527 activate_page_drain(cpu
);
531 * deactivate_page - forcefully deactivate a page
532 * @page: page to deactivate
534 * This function hints the VM that @page is a good reclaim candidate,
535 * for example if its invalidation fails due to the page being dirty
536 * or under writeback.
538 void deactivate_page(struct page
*page
)
541 * In a workload with many unevictable page such as mprotect, unevictable
542 * page deactivation for accelerating reclaim is pointless.
544 if (PageUnevictable(page
))
547 if (likely(get_page_unless_zero(page
))) {
548 struct pagevec
*pvec
= &get_cpu_var(lru_deactivate_pvecs
);
550 if (!pagevec_add(pvec
, page
))
551 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
552 put_cpu_var(lru_deactivate_pvecs
);
556 void lru_add_drain(void)
558 drain_cpu_pagevecs(get_cpu());
562 static void lru_add_drain_per_cpu(struct work_struct
*dummy
)
568 * Returns 0 for success
570 int lru_add_drain_all(void)
572 return schedule_on_each_cpu(lru_add_drain_per_cpu
);
576 * Batched page_cache_release(). Decrement the reference count on all the
577 * passed pages. If it fell to zero then remove the page from the LRU and
580 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
581 * for the remainder of the operation.
583 * The locking in this function is against shrink_inactive_list(): we recheck
584 * the page count inside the lock to see whether shrink_inactive_list()
585 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
588 void release_pages(struct page
**pages
, int nr
, int cold
)
591 LIST_HEAD(pages_to_free
);
592 struct zone
*zone
= NULL
;
593 unsigned long uninitialized_var(flags
);
595 for (i
= 0; i
< nr
; i
++) {
596 struct page
*page
= pages
[i
];
598 if (unlikely(PageCompound(page
))) {
600 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
603 put_compound_page(page
);
607 if (!put_page_testzero(page
))
611 struct zone
*pagezone
= page_zone(page
);
613 if (pagezone
!= zone
) {
615 spin_unlock_irqrestore(&zone
->lru_lock
,
618 spin_lock_irqsave(&zone
->lru_lock
, flags
);
620 VM_BUG_ON(!PageLRU(page
));
621 __ClearPageLRU(page
);
622 del_page_from_lru(zone
, page
);
625 list_add(&page
->lru
, &pages_to_free
);
628 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
630 free_hot_cold_page_list(&pages_to_free
, cold
);
632 EXPORT_SYMBOL(release_pages
);
635 * The pages which we're about to release may be in the deferred lru-addition
636 * queues. That would prevent them from really being freed right now. That's
637 * OK from a correctness point of view but is inefficient - those pages may be
638 * cache-warm and we want to give them back to the page allocator ASAP.
640 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
641 * and __pagevec_lru_add_active() call release_pages() directly to avoid
644 void __pagevec_release(struct pagevec
*pvec
)
647 release_pages(pvec
->pages
, pagevec_count(pvec
), pvec
->cold
);
648 pagevec_reinit(pvec
);
651 EXPORT_SYMBOL(__pagevec_release
);
653 /* used by __split_huge_page_refcount() */
654 void lru_add_page_tail(struct zone
* zone
,
655 struct page
*page
, struct page
*page_tail
)
661 VM_BUG_ON(!PageHead(page
));
662 VM_BUG_ON(PageCompound(page_tail
));
663 VM_BUG_ON(PageLRU(page_tail
));
664 VM_BUG_ON(!spin_is_locked(&zone
->lru_lock
));
666 SetPageLRU(page_tail
);
668 if (page_evictable(page_tail
, NULL
)) {
669 struct lruvec
*lruvec
;
671 if (PageActive(page
)) {
672 SetPageActive(page_tail
);
674 lru
= LRU_ACTIVE_ANON
;
677 lru
= LRU_INACTIVE_ANON
;
679 update_page_reclaim_stat(zone
, page_tail
, file
, active
);
680 lruvec
= mem_cgroup_lru_add_list(zone
, page_tail
, lru
);
681 if (likely(PageLRU(page
)))
682 list_add(&page_tail
->lru
, page
->lru
.prev
);
684 list_add(&page_tail
->lru
, lruvec
->lists
[lru
].prev
);
685 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
,
686 hpage_nr_pages(page_tail
));
688 SetPageUnevictable(page_tail
);
689 add_page_to_lru_list(zone
, page_tail
, LRU_UNEVICTABLE
);
693 static void ____pagevec_lru_add_fn(struct page
*page
, void *arg
)
695 enum lru_list lru
= (enum lru_list
)arg
;
696 struct zone
*zone
= page_zone(page
);
697 int file
= is_file_lru(lru
);
698 int active
= is_active_lru(lru
);
700 VM_BUG_ON(PageActive(page
));
701 VM_BUG_ON(PageUnevictable(page
));
702 VM_BUG_ON(PageLRU(page
));
707 update_page_reclaim_stat(zone
, page
, file
, active
);
708 add_page_to_lru_list(zone
, page
, lru
);
712 * Add the passed pages to the LRU, then drop the caller's refcount
713 * on them. Reinitialises the caller's pagevec.
715 void ____pagevec_lru_add(struct pagevec
*pvec
, enum lru_list lru
)
717 VM_BUG_ON(is_unevictable_lru(lru
));
719 pagevec_lru_move_fn(pvec
, ____pagevec_lru_add_fn
, (void *)lru
);
722 EXPORT_SYMBOL(____pagevec_lru_add
);
725 * Try to drop buffers from the pages in a pagevec
727 void pagevec_strip(struct pagevec
*pvec
)
731 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
732 struct page
*page
= pvec
->pages
[i
];
734 if (page_has_private(page
) && trylock_page(page
)) {
735 if (page_has_private(page
))
736 try_to_release_page(page
, 0);
743 * pagevec_lookup - gang pagecache lookup
744 * @pvec: Where the resulting pages are placed
745 * @mapping: The address_space to search
746 * @start: The starting page index
747 * @nr_pages: The maximum number of pages
749 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
750 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
751 * reference against the pages in @pvec.
753 * The search returns a group of mapping-contiguous pages with ascending
754 * indexes. There may be holes in the indices due to not-present pages.
756 * pagevec_lookup() returns the number of pages which were found.
758 unsigned pagevec_lookup(struct pagevec
*pvec
, struct address_space
*mapping
,
759 pgoff_t start
, unsigned nr_pages
)
761 pvec
->nr
= find_get_pages(mapping
, start
, nr_pages
, pvec
->pages
);
762 return pagevec_count(pvec
);
765 EXPORT_SYMBOL(pagevec_lookup
);
767 unsigned pagevec_lookup_tag(struct pagevec
*pvec
, struct address_space
*mapping
,
768 pgoff_t
*index
, int tag
, unsigned nr_pages
)
770 pvec
->nr
= find_get_pages_tag(mapping
, index
, tag
,
771 nr_pages
, pvec
->pages
);
772 return pagevec_count(pvec
);
775 EXPORT_SYMBOL(pagevec_lookup_tag
);
778 * Perform any setup for the swap system
780 void __init
swap_setup(void)
782 unsigned long megs
= totalram_pages
>> (20 - PAGE_SHIFT
);
785 bdi_init(swapper_space
.backing_dev_info
);
788 /* Use a smaller cluster for small-memory machines */
794 * Right now other parts of the system means that we
795 * _really_ don't want to cluster much more
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