blob: 96387e20184ab85971794daeb524ed07de6f8e18 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/swap.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 */
6
7/*
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.
11 * Started 18.12.91
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
14 */
15
16#include <linux/mm.h>
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>
33
34/* How many pages do we try to swap or page in/out together? */
35int page_cluster;
36
37#ifdef CONFIG_HUGETLB_PAGE
38
39void put_page(struct page *page)
40{
41 if (unlikely(PageCompound(page))) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070042 page = (struct page *)page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 if (put_page_testzero(page)) {
44 void (*dtor)(struct page *page);
45
46 dtor = (void (*)(struct page *))page[1].mapping;
47 (*dtor)(page);
48 }
49 return;
50 }
Nick Pigginb5810032005-10-29 18:16:12 -070051 if (put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 __page_cache_release(page);
53}
54EXPORT_SYMBOL(put_page);
55#endif
56
57/*
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.
61 *
62 * We don't expect many pages to come through here, so don't bother batching
63 * things up.
64 *
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.
69 *
70 * Returns zero if it cleared PG_writeback.
71 */
72int rotate_reclaimable_page(struct page *page)
73{
74 struct zone *zone;
75 unsigned long flags;
76
77 if (PageLocked(page))
78 return 1;
79 if (PageDirty(page))
80 return 1;
81 if (PageActive(page))
82 return 1;
83 if (!PageLRU(page))
84 return 1;
85
86 zone = page_zone(page);
87 spin_lock_irqsave(&zone->lru_lock, flags);
88 if (PageLRU(page) && !PageActive(page)) {
89 list_del(&page->lru);
90 list_add_tail(&page->lru, &zone->inactive_list);
91 inc_page_state(pgrotated);
92 }
93 if (!test_clear_page_writeback(page))
94 BUG();
95 spin_unlock_irqrestore(&zone->lru_lock, flags);
96 return 0;
97}
98
99/*
100 * FIXME: speed this up?
101 */
102void fastcall activate_page(struct page *page)
103{
104 struct zone *zone = page_zone(page);
105
106 spin_lock_irq(&zone->lru_lock);
107 if (PageLRU(page) && !PageActive(page)) {
108 del_page_from_inactive_list(zone, page);
109 SetPageActive(page);
110 add_page_to_active_list(zone, page);
111 inc_page_state(pgactivate);
112 }
113 spin_unlock_irq(&zone->lru_lock);
114}
115
116/*
117 * Mark a page as having seen activity.
118 *
119 * inactive,unreferenced -> inactive,referenced
120 * inactive,referenced -> active,unreferenced
121 * active,unreferenced -> active,referenced
122 */
123void fastcall mark_page_accessed(struct page *page)
124{
125 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
126 activate_page(page);
127 ClearPageReferenced(page);
128 } else if (!PageReferenced(page)) {
129 SetPageReferenced(page);
130 }
131}
132
133EXPORT_SYMBOL(mark_page_accessed);
134
135/**
136 * lru_cache_add: add a page to the page lists
137 * @page: the page to add
138 */
139static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
140static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
141
142void fastcall lru_cache_add(struct page *page)
143{
144 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
145
146 page_cache_get(page);
147 if (!pagevec_add(pvec, page))
148 __pagevec_lru_add(pvec);
149 put_cpu_var(lru_add_pvecs);
150}
151
152void fastcall lru_cache_add_active(struct page *page)
153{
154 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
155
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);
160}
161
162void lru_add_drain(void)
163{
164 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
165
166 if (pagevec_count(pvec))
167 __pagevec_lru_add(pvec);
168 pvec = &__get_cpu_var(lru_add_active_pvecs);
169 if (pagevec_count(pvec))
170 __pagevec_lru_add_active(pvec);
171 put_cpu_var(lru_add_pvecs);
172}
173
174/*
175 * This path almost never happens for VM activity - pages are normally
176 * freed via pagevecs. But it gets used by networking.
177 */
178void fastcall __page_cache_release(struct page *page)
179{
180 unsigned long flags;
181 struct zone *zone = page_zone(page);
182
183 spin_lock_irqsave(&zone->lru_lock, flags);
184 if (TestClearPageLRU(page))
185 del_page_from_lru(zone, page);
186 if (page_count(page) != 0)
187 page = NULL;
188 spin_unlock_irqrestore(&zone->lru_lock, flags);
189 if (page)
190 free_hot_page(page);
191}
192
193EXPORT_SYMBOL(__page_cache_release);
194
195/*
196 * Batched page_cache_release(). Decrement the reference count on all the
197 * passed pages. If it fell to zero then remove the page from the LRU and
198 * free it.
199 *
200 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
201 * for the remainder of the operation.
202 *
203 * The locking in this function is against shrink_cache(): we recheck the
204 * page count inside the lock to see whether shrink_cache grabbed the page
205 * via the LRU. If it did, give up: shrink_cache will free it.
206 */
207void release_pages(struct page **pages, int nr, int cold)
208{
209 int i;
210 struct pagevec pages_to_free;
211 struct zone *zone = NULL;
212
213 pagevec_init(&pages_to_free, cold);
214 for (i = 0; i < nr; i++) {
215 struct page *page = pages[i];
216 struct zone *pagezone;
217
Nick Pigginb5810032005-10-29 18:16:12 -0700218 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 continue;
220
221 pagezone = page_zone(page);
222 if (pagezone != zone) {
223 if (zone)
224 spin_unlock_irq(&zone->lru_lock);
225 zone = pagezone;
226 spin_lock_irq(&zone->lru_lock);
227 }
228 if (TestClearPageLRU(page))
229 del_page_from_lru(zone, page);
230 if (page_count(page) == 0) {
231 if (!pagevec_add(&pages_to_free, page)) {
232 spin_unlock_irq(&zone->lru_lock);
233 __pagevec_free(&pages_to_free);
234 pagevec_reinit(&pages_to_free);
235 zone = NULL; /* No lock is held */
236 }
237 }
238 }
239 if (zone)
240 spin_unlock_irq(&zone->lru_lock);
241
242 pagevec_free(&pages_to_free);
243}
244
245/*
246 * The pages which we're about to release may be in the deferred lru-addition
247 * queues. That would prevent them from really being freed right now. That's
248 * OK from a correctness point of view but is inefficient - those pages may be
249 * cache-warm and we want to give them back to the page allocator ASAP.
250 *
251 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
252 * and __pagevec_lru_add_active() call release_pages() directly to avoid
253 * mutual recursion.
254 */
255void __pagevec_release(struct pagevec *pvec)
256{
257 lru_add_drain();
258 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
259 pagevec_reinit(pvec);
260}
261
262/*
263 * pagevec_release() for pages which are known to not be on the LRU
264 *
265 * This function reinitialises the caller's pagevec.
266 */
267void __pagevec_release_nonlru(struct pagevec *pvec)
268{
269 int i;
270 struct pagevec pages_to_free;
271
272 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273 for (i = 0; i < pagevec_count(pvec); i++) {
274 struct page *page = pvec->pages[i];
275
276 BUG_ON(PageLRU(page));
277 if (put_page_testzero(page))
278 pagevec_add(&pages_to_free, page);
279 }
280 pagevec_free(&pages_to_free);
281 pagevec_reinit(pvec);
282}
283
284/*
285 * Add the passed pages to the LRU, then drop the caller's refcount
286 * on them. Reinitialises the caller's pagevec.
287 */
288void __pagevec_lru_add(struct pagevec *pvec)
289{
290 int i;
291 struct zone *zone = NULL;
292
293 for (i = 0; i < pagevec_count(pvec); i++) {
294 struct page *page = pvec->pages[i];
295 struct zone *pagezone = page_zone(page);
296
297 if (pagezone != zone) {
298 if (zone)
299 spin_unlock_irq(&zone->lru_lock);
300 zone = pagezone;
301 spin_lock_irq(&zone->lru_lock);
302 }
303 if (TestSetPageLRU(page))
304 BUG();
305 add_page_to_inactive_list(zone, page);
306 }
307 if (zone)
308 spin_unlock_irq(&zone->lru_lock);
309 release_pages(pvec->pages, pvec->nr, pvec->cold);
310 pagevec_reinit(pvec);
311}
312
313EXPORT_SYMBOL(__pagevec_lru_add);
314
315void __pagevec_lru_add_active(struct pagevec *pvec)
316{
317 int i;
318 struct zone *zone = NULL;
319
320 for (i = 0; i < pagevec_count(pvec); i++) {
321 struct page *page = pvec->pages[i];
322 struct zone *pagezone = page_zone(page);
323
324 if (pagezone != zone) {
325 if (zone)
326 spin_unlock_irq(&zone->lru_lock);
327 zone = pagezone;
328 spin_lock_irq(&zone->lru_lock);
329 }
330 if (TestSetPageLRU(page))
331 BUG();
332 if (TestSetPageActive(page))
333 BUG();
334 add_page_to_active_list(zone, page);
335 }
336 if (zone)
337 spin_unlock_irq(&zone->lru_lock);
338 release_pages(pvec->pages, pvec->nr, pvec->cold);
339 pagevec_reinit(pvec);
340}
341
342/*
343 * Try to drop buffers from the pages in a pagevec
344 */
345void pagevec_strip(struct pagevec *pvec)
346{
347 int i;
348
349 for (i = 0; i < pagevec_count(pvec); i++) {
350 struct page *page = pvec->pages[i];
351
352 if (PagePrivate(page) && !TestSetPageLocked(page)) {
353 try_to_release_page(page, 0);
354 unlock_page(page);
355 }
356 }
357}
358
359/**
360 * pagevec_lookup - gang pagecache lookup
361 * @pvec: Where the resulting pages are placed
362 * @mapping: The address_space to search
363 * @start: The starting page index
364 * @nr_pages: The maximum number of pages
365 *
366 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
367 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
368 * reference against the pages in @pvec.
369 *
370 * The search returns a group of mapping-contiguous pages with ascending
371 * indexes. There may be holes in the indices due to not-present pages.
372 *
373 * pagevec_lookup() returns the number of pages which were found.
374 */
375unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
376 pgoff_t start, unsigned nr_pages)
377{
378 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
379 return pagevec_count(pvec);
380}
381
382unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
383 pgoff_t *index, int tag, unsigned nr_pages)
384{
385 pvec->nr = find_get_pages_tag(mapping, index, tag,
386 nr_pages, pvec->pages);
387 return pagevec_count(pvec);
388}
389
390
391#ifdef CONFIG_SMP
392/*
393 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
394 * CPUs
395 */
396#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
397
398static DEFINE_PER_CPU(long, committed_space) = 0;
399
400void vm_acct_memory(long pages)
401{
402 long *local;
403
404 preempt_disable();
405 local = &__get_cpu_var(committed_space);
406 *local += pages;
407 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
408 atomic_add(*local, &vm_committed_space);
409 *local = 0;
410 }
411 preempt_enable();
412}
413EXPORT_SYMBOL(vm_acct_memory);
414
415#ifdef CONFIG_HOTPLUG_CPU
416static void lru_drain_cache(unsigned int cpu)
417{
418 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
419
420 /* CPU is dead, so no locking needed. */
421 if (pagevec_count(pvec))
422 __pagevec_lru_add(pvec);
423 pvec = &per_cpu(lru_add_active_pvecs, cpu);
424 if (pagevec_count(pvec))
425 __pagevec_lru_add_active(pvec);
426}
427
428/* Drop the CPU's cached committed space back into the central pool. */
429static int cpu_swap_callback(struct notifier_block *nfb,
430 unsigned long action,
431 void *hcpu)
432{
433 long *committed;
434
435 committed = &per_cpu(committed_space, (long)hcpu);
436 if (action == CPU_DEAD) {
437 atomic_add(*committed, &vm_committed_space);
438 *committed = 0;
439 lru_drain_cache((long)hcpu);
440 }
441 return NOTIFY_OK;
442}
443#endif /* CONFIG_HOTPLUG_CPU */
444#endif /* CONFIG_SMP */
445
446#ifdef CONFIG_SMP
447void percpu_counter_mod(struct percpu_counter *fbc, long amount)
448{
449 long count;
450 long *pcount;
451 int cpu = get_cpu();
452
453 pcount = per_cpu_ptr(fbc->counters, cpu);
454 count = *pcount + amount;
455 if (count >= FBC_BATCH || count <= -FBC_BATCH) {
456 spin_lock(&fbc->lock);
457 fbc->count += count;
458 spin_unlock(&fbc->lock);
459 count = 0;
460 }
461 *pcount = count;
462 put_cpu();
463}
464EXPORT_SYMBOL(percpu_counter_mod);
465#endif
466
467/*
468 * Perform any setup for the swap system
469 */
470void __init swap_setup(void)
471{
472 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
473
474 /* Use a smaller cluster for small-memory machines */
475 if (megs < 16)
476 page_cluster = 2;
477 else
478 page_cluster = 3;
479 /*
480 * Right now other parts of the system means that we
481 * _really_ don't want to cluster much more
482 */
483 hotcpu_notifier(cpu_swap_callback, 0);
484}