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/module.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>
34 /* How many pages do we try to swap or page in/out together? */
37 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
38 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
39 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs) = { 0, };
42 * This path almost never happens for VM activity - pages are normally
43 * freed via pagevecs. But it gets used by networking.
45 static void __page_cache_release(struct page *page)
49 struct zone *zone = page_zone(page);
51 spin_lock_irqsave(&zone->lru_lock, flags);
52 VM_BUG_ON(!PageLRU(page));
54 del_page_from_lru(zone, page);
55 spin_unlock_irqrestore(&zone->lru_lock, flags);
60 static void put_compound_page(struct page *page)
62 page = compound_head(page);
63 if (put_page_testzero(page)) {
64 compound_page_dtor *dtor;
66 dtor = get_compound_page_dtor(page);
71 void put_page(struct page *page)
73 if (unlikely(PageCompound(page)))
74 put_compound_page(page);
75 else if (put_page_testzero(page))
76 __page_cache_release(page);
78 EXPORT_SYMBOL(put_page);
81 * put_pages_list(): release a list of pages
83 * Release a list of pages which are strung together on page.lru. Currently
84 * used by read_cache_pages() and related error recovery code.
86 * @pages: list of pages threaded on page->lru
88 void put_pages_list(struct list_head *pages)
90 while (!list_empty(pages)) {
93 victim = list_entry(pages->prev, struct page, lru);
94 list_del(&victim->lru);
95 page_cache_release(victim);
98 EXPORT_SYMBOL(put_pages_list);
101 * pagevec_move_tail() must be called with IRQ disabled.
102 * Otherwise this may cause nasty races.
104 static void pagevec_move_tail(struct pagevec *pvec)
108 struct zone *zone = NULL;
110 for (i = 0; i < pagevec_count(pvec); i++) {
111 struct page *page = pvec->pages[i];
112 struct zone *pagezone = page_zone(page);
114 if (pagezone != zone) {
116 spin_unlock(&zone->lru_lock);
118 spin_lock(&zone->lru_lock);
120 if (PageLRU(page) && !PageActive(page)) {
121 list_move_tail(&page->lru, &zone->inactive_list);
126 spin_unlock(&zone->lru_lock);
127 __count_vm_events(PGROTATED, pgmoved);
128 release_pages(pvec->pages, pvec->nr, pvec->cold);
129 pagevec_reinit(pvec);
133 * Writeback is about to end against a page which has been marked for immediate
134 * reclaim. If it still appears to be reclaimable, move it to the tail of the
137 * Returns zero if it cleared PG_writeback.
139 int rotate_reclaimable_page(struct page *page)
141 struct pagevec *pvec;
144 if (PageLocked(page))
148 if (PageActive(page))
153 page_cache_get(page);
154 local_irq_save(flags);
155 pvec = &__get_cpu_var(lru_rotate_pvecs);
156 if (!pagevec_add(pvec, page))
157 pagevec_move_tail(pvec);
158 local_irq_restore(flags);
160 if (!test_clear_page_writeback(page))
167 * FIXME: speed this up?
169 void activate_page(struct page *page)
171 struct zone *zone = page_zone(page);
173 spin_lock_irq(&zone->lru_lock);
174 if (PageLRU(page) && !PageActive(page)) {
175 del_page_from_inactive_list(zone, page);
177 add_page_to_active_list(zone, page);
178 __count_vm_event(PGACTIVATE);
179 mem_cgroup_move_lists(page_get_page_cgroup(page), true);
181 spin_unlock_irq(&zone->lru_lock);
185 * Mark a page as having seen activity.
187 * inactive,unreferenced -> inactive,referenced
188 * inactive,referenced -> active,unreferenced
189 * active,unreferenced -> active,referenced
191 void mark_page_accessed(struct page *page)
193 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
195 ClearPageReferenced(page);
196 } else if (!PageReferenced(page)) {
197 SetPageReferenced(page);
201 EXPORT_SYMBOL(mark_page_accessed);
204 * lru_cache_add: add a page to the page lists
205 * @page: the page to add
207 void lru_cache_add(struct page *page)
209 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
211 page_cache_get(page);
212 if (!pagevec_add(pvec, page))
213 __pagevec_lru_add(pvec);
214 put_cpu_var(lru_add_pvecs);
217 void lru_cache_add_active(struct page *page)
219 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
221 page_cache_get(page);
222 if (!pagevec_add(pvec, page))
223 __pagevec_lru_add_active(pvec);
224 put_cpu_var(lru_add_active_pvecs);
228 * Drain pages out of the cpu's pagevecs.
229 * Either "cpu" is the current CPU, and preemption has already been
230 * disabled; or "cpu" is being hot-unplugged, and is already dead.
232 static void drain_cpu_pagevecs(int cpu)
234 struct pagevec *pvec;
236 pvec = &per_cpu(lru_add_pvecs, cpu);
237 if (pagevec_count(pvec))
238 __pagevec_lru_add(pvec);
240 pvec = &per_cpu(lru_add_active_pvecs, cpu);
241 if (pagevec_count(pvec))
242 __pagevec_lru_add_active(pvec);
244 pvec = &per_cpu(lru_rotate_pvecs, cpu);
245 if (pagevec_count(pvec)) {
248 /* No harm done if a racing interrupt already did this */
249 local_irq_save(flags);
250 pagevec_move_tail(pvec);
251 local_irq_restore(flags);
255 void lru_add_drain(void)
257 drain_cpu_pagevecs(get_cpu());
262 static void lru_add_drain_per_cpu(struct work_struct *dummy)
268 * Returns 0 for success
270 int lru_add_drain_all(void)
272 return schedule_on_each_cpu(lru_add_drain_per_cpu);
278 * Returns 0 for success
280 int lru_add_drain_all(void)
288 * Batched page_cache_release(). Decrement the reference count on all the
289 * passed pages. If it fell to zero then remove the page from the LRU and
292 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
293 * for the remainder of the operation.
295 * The locking in this function is against shrink_cache(): we recheck the
296 * page count inside the lock to see whether shrink_cache grabbed the page
297 * via the LRU. If it did, give up: shrink_cache will free it.
299 void release_pages(struct page **pages, int nr, int cold)
302 struct pagevec pages_to_free;
303 struct zone *zone = NULL;
304 unsigned long uninitialized_var(flags);
306 pagevec_init(&pages_to_free, cold);
307 for (i = 0; i < nr; i++) {
308 struct page *page = pages[i];
310 if (unlikely(PageCompound(page))) {
312 spin_unlock_irqrestore(&zone->lru_lock, flags);
315 put_compound_page(page);
319 if (!put_page_testzero(page))
323 struct zone *pagezone = page_zone(page);
324 if (pagezone != zone) {
326 spin_unlock_irqrestore(&zone->lru_lock,
329 spin_lock_irqsave(&zone->lru_lock, flags);
331 VM_BUG_ON(!PageLRU(page));
332 __ClearPageLRU(page);
333 del_page_from_lru(zone, page);
336 if (!pagevec_add(&pages_to_free, page)) {
338 spin_unlock_irqrestore(&zone->lru_lock, flags);
341 __pagevec_free(&pages_to_free);
342 pagevec_reinit(&pages_to_free);
346 spin_unlock_irqrestore(&zone->lru_lock, flags);
348 pagevec_free(&pages_to_free);
352 * The pages which we're about to release may be in the deferred lru-addition
353 * queues. That would prevent them from really being freed right now. That's
354 * OK from a correctness point of view but is inefficient - those pages may be
355 * cache-warm and we want to give them back to the page allocator ASAP.
357 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
358 * and __pagevec_lru_add_active() call release_pages() directly to avoid
361 void __pagevec_release(struct pagevec *pvec)
364 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
365 pagevec_reinit(pvec);
368 EXPORT_SYMBOL(__pagevec_release);
371 * pagevec_release() for pages which are known to not be on the LRU
373 * This function reinitialises the caller's pagevec.
375 void __pagevec_release_nonlru(struct pagevec *pvec)
378 struct pagevec pages_to_free;
380 pagevec_init(&pages_to_free, pvec->cold);
381 for (i = 0; i < pagevec_count(pvec); i++) {
382 struct page *page = pvec->pages[i];
384 VM_BUG_ON(PageLRU(page));
385 if (put_page_testzero(page))
386 pagevec_add(&pages_to_free, page);
388 pagevec_free(&pages_to_free);
389 pagevec_reinit(pvec);
393 * Add the passed pages to the LRU, then drop the caller's refcount
394 * on them. Reinitialises the caller's pagevec.
396 void __pagevec_lru_add(struct pagevec *pvec)
399 struct zone *zone = NULL;
401 for (i = 0; i < pagevec_count(pvec); i++) {
402 struct page *page = pvec->pages[i];
403 struct zone *pagezone = page_zone(page);
405 if (pagezone != zone) {
407 spin_unlock_irq(&zone->lru_lock);
409 spin_lock_irq(&zone->lru_lock);
411 VM_BUG_ON(PageLRU(page));
413 add_page_to_inactive_list(zone, page);
416 spin_unlock_irq(&zone->lru_lock);
417 release_pages(pvec->pages, pvec->nr, pvec->cold);
418 pagevec_reinit(pvec);
421 EXPORT_SYMBOL(__pagevec_lru_add);
423 void __pagevec_lru_add_active(struct pagevec *pvec)
426 struct zone *zone = NULL;
428 for (i = 0; i < pagevec_count(pvec); i++) {
429 struct page *page = pvec->pages[i];
430 struct zone *pagezone = page_zone(page);
432 if (pagezone != zone) {
434 spin_unlock_irq(&zone->lru_lock);
436 spin_lock_irq(&zone->lru_lock);
438 VM_BUG_ON(PageLRU(page));
440 VM_BUG_ON(PageActive(page));
442 add_page_to_active_list(zone, page);
445 spin_unlock_irq(&zone->lru_lock);
446 release_pages(pvec->pages, pvec->nr, pvec->cold);
447 pagevec_reinit(pvec);
451 * Try to drop buffers from the pages in a pagevec
453 void pagevec_strip(struct pagevec *pvec)
457 for (i = 0; i < pagevec_count(pvec); i++) {
458 struct page *page = pvec->pages[i];
460 if (PagePrivate(page) && !TestSetPageLocked(page)) {
461 if (PagePrivate(page))
462 try_to_release_page(page, 0);
469 * pagevec_lookup - gang pagecache lookup
470 * @pvec: Where the resulting pages are placed
471 * @mapping: The address_space to search
472 * @start: The starting page index
473 * @nr_pages: The maximum number of pages
475 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
476 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
477 * reference against the pages in @pvec.
479 * The search returns a group of mapping-contiguous pages with ascending
480 * indexes. There may be holes in the indices due to not-present pages.
482 * pagevec_lookup() returns the number of pages which were found.
484 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
485 pgoff_t start, unsigned nr_pages)
487 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
488 return pagevec_count(pvec);
491 EXPORT_SYMBOL(pagevec_lookup);
493 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
494 pgoff_t *index, int tag, unsigned nr_pages)
496 pvec->nr = find_get_pages_tag(mapping, index, tag,
497 nr_pages, pvec->pages);
498 return pagevec_count(pvec);
501 EXPORT_SYMBOL(pagevec_lookup_tag);
505 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
508 #define ACCT_THRESHOLD max(16, NR_CPUS * 2)
510 static DEFINE_PER_CPU(long, committed_space) = 0;
512 void vm_acct_memory(long pages)
517 local = &__get_cpu_var(committed_space);
519 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
520 atomic_add(*local, &vm_committed_space);
526 #ifdef CONFIG_HOTPLUG_CPU
528 /* Drop the CPU's cached committed space back into the central pool. */
529 static int cpu_swap_callback(struct notifier_block *nfb,
530 unsigned long action,
535 committed = &per_cpu(committed_space, (long)hcpu);
536 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
537 atomic_add(*committed, &vm_committed_space);
539 drain_cpu_pagevecs((long)hcpu);
543 #endif /* CONFIG_HOTPLUG_CPU */
544 #endif /* CONFIG_SMP */
547 * Perform any setup for the swap system
549 void __init swap_setup(void)
551 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
554 bdi_init(swapper_space.backing_dev_info);
557 /* Use a smaller cluster for small-memory machines */
563 * Right now other parts of the system means that we
564 * _really_ don't want to cluster much more
566 #ifdef CONFIG_HOTPLUG_CPU
567 hotcpu_notifier(cpu_swap_callback, 0);