4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * This file contains the default values for the opereation 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/module.h>
28 #include <linux/percpu_counter.h>
29 #include <linux/percpu.h>
30 #include <linux/cpu.h>
31 #include <linux/notifier.h>
32 #include <linux/init.h>
34 /* How many pages do we try to swap or page in/out together? */
37 static void put_compound_page(struct page *page)
39 page = (struct page *)page_private(page);
40 if (put_page_testzero(page)) {
41 void (*dtor)(struct page *page);
43 dtor = (void (*)(struct page *))page[1].mapping;
48 void put_page(struct page *page)
50 if (unlikely(PageCompound(page)))
51 put_compound_page(page);
52 else if (put_page_testzero(page))
53 __page_cache_release(page);
55 EXPORT_SYMBOL(put_page);
58 * Writeback is about to end against a page which has been marked for immediate
59 * reclaim. If it still appears to be reclaimable, move it to the tail of the
60 * inactive list. The page still has PageWriteback set, which will pin it.
62 * We don't expect many pages to come through here, so don't bother batching
65 * To avoid placing the page at the tail of the LRU while PG_writeback is still
66 * set, this function will clear PG_writeback before performing the page
67 * motion. Do that inside the lru lock because once PG_writeback is cleared
68 * we may not touch the page.
70 * Returns zero if it cleared PG_writeback.
72 int rotate_reclaimable_page(struct page *page)
86 zone = page_zone(page);
87 spin_lock_irqsave(&zone->lru_lock, flags);
88 if (PageLRU(page) && !PageActive(page)) {
90 list_add_tail(&page->lru, &zone->inactive_list);
91 inc_page_state(pgrotated);
93 if (!test_clear_page_writeback(page))
95 spin_unlock_irqrestore(&zone->lru_lock, flags);
100 * FIXME: speed this up?
102 void fastcall activate_page(struct page *page)
104 struct zone *zone = page_zone(page);
106 spin_lock_irq(&zone->lru_lock);
107 if (PageLRU(page) && !PageActive(page)) {
108 del_page_from_inactive_list(zone, page);
110 add_page_to_active_list(zone, page);
111 inc_page_state(pgactivate);
113 spin_unlock_irq(&zone->lru_lock);
117 * Mark a page as having seen activity.
119 * inactive,unreferenced -> inactive,referenced
120 * inactive,referenced -> active,unreferenced
121 * active,unreferenced -> active,referenced
123 void fastcall mark_page_accessed(struct page *page)
125 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
127 ClearPageReferenced(page);
128 } else if (!PageReferenced(page)) {
129 SetPageReferenced(page);
133 EXPORT_SYMBOL(mark_page_accessed);
136 * lru_cache_add: add a page to the page lists
137 * @page: the page to add
139 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
140 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
142 void fastcall lru_cache_add(struct page *page)
144 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
146 page_cache_get(page);
147 if (!pagevec_add(pvec, page))
148 __pagevec_lru_add(pvec);
149 put_cpu_var(lru_add_pvecs);
152 void fastcall lru_cache_add_active(struct page *page)
154 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
156 page_cache_get(page);
157 if (!pagevec_add(pvec, page))
158 __pagevec_lru_add_active(pvec);
159 put_cpu_var(lru_add_active_pvecs);
162 static void __lru_add_drain(int cpu)
164 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
166 /* CPU is dead, so no locking needed. */
167 if (pagevec_count(pvec))
168 __pagevec_lru_add(pvec);
169 pvec = &per_cpu(lru_add_active_pvecs, cpu);
170 if (pagevec_count(pvec))
171 __pagevec_lru_add_active(pvec);
174 void lru_add_drain(void)
176 __lru_add_drain(get_cpu());
181 static void lru_add_drain_per_cpu(void *dummy)
187 * Returns 0 for success
189 int lru_add_drain_all(void)
191 return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
197 * Returns 0 for success
199 int lru_add_drain_all(void)
207 * This path almost never happens for VM activity - pages are normally
208 * freed via pagevecs. But it gets used by networking.
210 void fastcall __page_cache_release(struct page *page)
213 struct zone *zone = page_zone(page);
215 spin_lock_irqsave(&zone->lru_lock, flags);
216 if (TestClearPageLRU(page))
217 del_page_from_lru(zone, page);
218 if (page_count(page) != 0)
220 spin_unlock_irqrestore(&zone->lru_lock, flags);
225 EXPORT_SYMBOL(__page_cache_release);
228 * Batched page_cache_release(). Decrement the reference count on all the
229 * passed pages. If it fell to zero then remove the page from the LRU and
232 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
233 * for the remainder of the operation.
235 * The locking in this function is against shrink_cache(): we recheck the
236 * page count inside the lock to see whether shrink_cache grabbed the page
237 * via the LRU. If it did, give up: shrink_cache will free it.
239 void release_pages(struct page **pages, int nr, int cold)
242 struct pagevec pages_to_free;
243 struct zone *zone = NULL;
245 pagevec_init(&pages_to_free, cold);
246 for (i = 0; i < nr; i++) {
247 struct page *page = pages[i];
248 struct zone *pagezone;
250 if (unlikely(PageCompound(page))) {
252 spin_unlock_irq(&zone->lru_lock);
255 put_compound_page(page);
259 if (!put_page_testzero(page))
262 pagezone = page_zone(page);
263 if (pagezone != zone) {
265 spin_unlock_irq(&zone->lru_lock);
267 spin_lock_irq(&zone->lru_lock);
269 if (TestClearPageLRU(page))
270 del_page_from_lru(zone, page);
271 if (page_count(page) == 0) {
272 if (!pagevec_add(&pages_to_free, page)) {
273 spin_unlock_irq(&zone->lru_lock);
274 __pagevec_free(&pages_to_free);
275 pagevec_reinit(&pages_to_free);
276 zone = NULL; /* No lock is held */
281 spin_unlock_irq(&zone->lru_lock);
283 pagevec_free(&pages_to_free);
287 * The pages which we're about to release may be in the deferred lru-addition
288 * queues. That would prevent them from really being freed right now. That's
289 * OK from a correctness point of view but is inefficient - those pages may be
290 * cache-warm and we want to give them back to the page allocator ASAP.
292 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
293 * and __pagevec_lru_add_active() call release_pages() directly to avoid
296 void __pagevec_release(struct pagevec *pvec)
299 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
300 pagevec_reinit(pvec);
303 EXPORT_SYMBOL(__pagevec_release);
306 * pagevec_release() for pages which are known to not be on the LRU
308 * This function reinitialises the caller's pagevec.
310 void __pagevec_release_nonlru(struct pagevec *pvec)
313 struct pagevec pages_to_free;
315 pagevec_init(&pages_to_free, pvec->cold);
316 for (i = 0; i < pagevec_count(pvec); i++) {
317 struct page *page = pvec->pages[i];
319 BUG_ON(PageLRU(page));
320 if (put_page_testzero(page))
321 pagevec_add(&pages_to_free, page);
323 pagevec_free(&pages_to_free);
324 pagevec_reinit(pvec);
328 * Add the passed pages to the LRU, then drop the caller's refcount
329 * on them. Reinitialises the caller's pagevec.
331 void __pagevec_lru_add(struct pagevec *pvec)
334 struct zone *zone = NULL;
336 for (i = 0; i < pagevec_count(pvec); i++) {
337 struct page *page = pvec->pages[i];
338 struct zone *pagezone = page_zone(page);
340 if (pagezone != zone) {
342 spin_unlock_irq(&zone->lru_lock);
344 spin_lock_irq(&zone->lru_lock);
346 if (TestSetPageLRU(page))
348 add_page_to_inactive_list(zone, page);
351 spin_unlock_irq(&zone->lru_lock);
352 release_pages(pvec->pages, pvec->nr, pvec->cold);
353 pagevec_reinit(pvec);
356 EXPORT_SYMBOL(__pagevec_lru_add);
358 void __pagevec_lru_add_active(struct pagevec *pvec)
361 struct zone *zone = NULL;
363 for (i = 0; i < pagevec_count(pvec); i++) {
364 struct page *page = pvec->pages[i];
365 struct zone *pagezone = page_zone(page);
367 if (pagezone != zone) {
369 spin_unlock_irq(&zone->lru_lock);
371 spin_lock_irq(&zone->lru_lock);
373 if (TestSetPageLRU(page))
375 if (TestSetPageActive(page))
377 add_page_to_active_list(zone, page);
380 spin_unlock_irq(&zone->lru_lock);
381 release_pages(pvec->pages, pvec->nr, pvec->cold);
382 pagevec_reinit(pvec);
386 * Try to drop buffers from the pages in a pagevec
388 void pagevec_strip(struct pagevec *pvec)
392 for (i = 0; i < pagevec_count(pvec); i++) {
393 struct page *page = pvec->pages[i];
395 if (PagePrivate(page) && !TestSetPageLocked(page)) {
396 try_to_release_page(page, 0);
403 * pagevec_lookup - gang pagecache lookup
404 * @pvec: Where the resulting pages are placed
405 * @mapping: The address_space to search
406 * @start: The starting page index
407 * @nr_pages: The maximum number of pages
409 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
410 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
411 * reference against the pages in @pvec.
413 * The search returns a group of mapping-contiguous pages with ascending
414 * indexes. There may be holes in the indices due to not-present pages.
416 * pagevec_lookup() returns the number of pages which were found.
418 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
419 pgoff_t start, unsigned nr_pages)
421 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
422 return pagevec_count(pvec);
425 EXPORT_SYMBOL(pagevec_lookup);
427 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
428 pgoff_t *index, int tag, unsigned nr_pages)
430 pvec->nr = find_get_pages_tag(mapping, index, tag,
431 nr_pages, pvec->pages);
432 return pagevec_count(pvec);
435 EXPORT_SYMBOL(pagevec_lookup_tag);
439 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
442 #define ACCT_THRESHOLD max(16, NR_CPUS * 2)
444 static DEFINE_PER_CPU(long, committed_space) = 0;
446 void vm_acct_memory(long pages)
451 local = &__get_cpu_var(committed_space);
453 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
454 atomic_add(*local, &vm_committed_space);
460 #ifdef CONFIG_HOTPLUG_CPU
462 /* Drop the CPU's cached committed space back into the central pool. */
463 static int cpu_swap_callback(struct notifier_block *nfb,
464 unsigned long action,
469 committed = &per_cpu(committed_space, (long)hcpu);
470 if (action == CPU_DEAD) {
471 atomic_add(*committed, &vm_committed_space);
473 __lru_add_drain((long)hcpu);
477 #endif /* CONFIG_HOTPLUG_CPU */
478 #endif /* CONFIG_SMP */
481 void percpu_counter_mod(struct percpu_counter *fbc, long amount)
487 pcount = per_cpu_ptr(fbc->counters, cpu);
488 count = *pcount + amount;
489 if (count >= FBC_BATCH || count <= -FBC_BATCH) {
490 spin_lock(&fbc->lock);
492 spin_unlock(&fbc->lock);
498 EXPORT_SYMBOL(percpu_counter_mod);
502 * Perform any setup for the swap system
504 void __init swap_setup(void)
506 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
508 /* Use a smaller cluster for small-memory machines */
514 * Right now other parts of the system means that we
515 * _really_ don't want to cluster much more
517 hotcpu_notifier(cpu_swap_callback, 0);