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1da177e4 LT |
1 | /* |
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? */ | |
35 | int page_cluster; | |
36 | ||
1da177e4 LT |
37 | void put_page(struct page *page) |
38 | { | |
39 | if (unlikely(PageCompound(page))) { | |
4c21e2f2 | 40 | page = (struct page *)page_private(page); |
1da177e4 LT |
41 | if (put_page_testzero(page)) { |
42 | void (*dtor)(struct page *page); | |
43 | ||
44 | dtor = (void (*)(struct page *))page[1].mapping; | |
45 | (*dtor)(page); | |
46 | } | |
47 | return; | |
48 | } | |
b5810039 | 49 | if (put_page_testzero(page)) |
1da177e4 LT |
50 | __page_cache_release(page); |
51 | } | |
52 | EXPORT_SYMBOL(put_page); | |
1da177e4 LT |
53 | |
54 | /* | |
55 | * Writeback is about to end against a page which has been marked for immediate | |
56 | * reclaim. If it still appears to be reclaimable, move it to the tail of the | |
57 | * inactive list. The page still has PageWriteback set, which will pin it. | |
58 | * | |
59 | * We don't expect many pages to come through here, so don't bother batching | |
60 | * things up. | |
61 | * | |
62 | * To avoid placing the page at the tail of the LRU while PG_writeback is still | |
63 | * set, this function will clear PG_writeback before performing the page | |
64 | * motion. Do that inside the lru lock because once PG_writeback is cleared | |
65 | * we may not touch the page. | |
66 | * | |
67 | * Returns zero if it cleared PG_writeback. | |
68 | */ | |
69 | int rotate_reclaimable_page(struct page *page) | |
70 | { | |
71 | struct zone *zone; | |
72 | unsigned long flags; | |
73 | ||
74 | if (PageLocked(page)) | |
75 | return 1; | |
76 | if (PageDirty(page)) | |
77 | return 1; | |
78 | if (PageActive(page)) | |
79 | return 1; | |
80 | if (!PageLRU(page)) | |
81 | return 1; | |
82 | ||
83 | zone = page_zone(page); | |
84 | spin_lock_irqsave(&zone->lru_lock, flags); | |
85 | if (PageLRU(page) && !PageActive(page)) { | |
86 | list_del(&page->lru); | |
87 | list_add_tail(&page->lru, &zone->inactive_list); | |
88 | inc_page_state(pgrotated); | |
89 | } | |
90 | if (!test_clear_page_writeback(page)) | |
91 | BUG(); | |
92 | spin_unlock_irqrestore(&zone->lru_lock, flags); | |
93 | return 0; | |
94 | } | |
95 | ||
96 | /* | |
97 | * FIXME: speed this up? | |
98 | */ | |
99 | void fastcall activate_page(struct page *page) | |
100 | { | |
101 | struct zone *zone = page_zone(page); | |
102 | ||
103 | spin_lock_irq(&zone->lru_lock); | |
104 | if (PageLRU(page) && !PageActive(page)) { | |
105 | del_page_from_inactive_list(zone, page); | |
106 | SetPageActive(page); | |
107 | add_page_to_active_list(zone, page); | |
108 | inc_page_state(pgactivate); | |
109 | } | |
110 | spin_unlock_irq(&zone->lru_lock); | |
111 | } | |
112 | ||
113 | /* | |
114 | * Mark a page as having seen activity. | |
115 | * | |
116 | * inactive,unreferenced -> inactive,referenced | |
117 | * inactive,referenced -> active,unreferenced | |
118 | * active,unreferenced -> active,referenced | |
119 | */ | |
120 | void fastcall mark_page_accessed(struct page *page) | |
121 | { | |
122 | if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) { | |
123 | activate_page(page); | |
124 | ClearPageReferenced(page); | |
125 | } else if (!PageReferenced(page)) { | |
126 | SetPageReferenced(page); | |
127 | } | |
128 | } | |
129 | ||
130 | EXPORT_SYMBOL(mark_page_accessed); | |
131 | ||
132 | /** | |
133 | * lru_cache_add: add a page to the page lists | |
134 | * @page: the page to add | |
135 | */ | |
136 | static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, }; | |
137 | static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, }; | |
138 | ||
139 | void fastcall lru_cache_add(struct page *page) | |
140 | { | |
141 | struct pagevec *pvec = &get_cpu_var(lru_add_pvecs); | |
142 | ||
143 | page_cache_get(page); | |
144 | if (!pagevec_add(pvec, page)) | |
145 | __pagevec_lru_add(pvec); | |
146 | put_cpu_var(lru_add_pvecs); | |
147 | } | |
148 | ||
149 | void fastcall lru_cache_add_active(struct page *page) | |
150 | { | |
151 | struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs); | |
152 | ||
153 | page_cache_get(page); | |
154 | if (!pagevec_add(pvec, page)) | |
155 | __pagevec_lru_add_active(pvec); | |
156 | put_cpu_var(lru_add_active_pvecs); | |
157 | } | |
158 | ||
80bfed90 | 159 | static void __lru_add_drain(int cpu) |
1da177e4 | 160 | { |
80bfed90 | 161 | struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu); |
1da177e4 | 162 | |
80bfed90 | 163 | /* CPU is dead, so no locking needed. */ |
1da177e4 LT |
164 | if (pagevec_count(pvec)) |
165 | __pagevec_lru_add(pvec); | |
80bfed90 | 166 | pvec = &per_cpu(lru_add_active_pvecs, cpu); |
1da177e4 LT |
167 | if (pagevec_count(pvec)) |
168 | __pagevec_lru_add_active(pvec); | |
80bfed90 AM |
169 | } |
170 | ||
171 | void lru_add_drain(void) | |
172 | { | |
173 | __lru_add_drain(get_cpu()); | |
174 | put_cpu(); | |
1da177e4 LT |
175 | } |
176 | ||
177 | /* | |
178 | * This path almost never happens for VM activity - pages are normally | |
179 | * freed via pagevecs. But it gets used by networking. | |
180 | */ | |
181 | void fastcall __page_cache_release(struct page *page) | |
182 | { | |
183 | unsigned long flags; | |
184 | struct zone *zone = page_zone(page); | |
185 | ||
186 | spin_lock_irqsave(&zone->lru_lock, flags); | |
187 | if (TestClearPageLRU(page)) | |
188 | del_page_from_lru(zone, page); | |
189 | if (page_count(page) != 0) | |
190 | page = NULL; | |
191 | spin_unlock_irqrestore(&zone->lru_lock, flags); | |
192 | if (page) | |
193 | free_hot_page(page); | |
194 | } | |
195 | ||
196 | EXPORT_SYMBOL(__page_cache_release); | |
197 | ||
198 | /* | |
199 | * Batched page_cache_release(). Decrement the reference count on all the | |
200 | * passed pages. If it fell to zero then remove the page from the LRU and | |
201 | * free it. | |
202 | * | |
203 | * Avoid taking zone->lru_lock if possible, but if it is taken, retain it | |
204 | * for the remainder of the operation. | |
205 | * | |
206 | * The locking in this function is against shrink_cache(): we recheck the | |
207 | * page count inside the lock to see whether shrink_cache grabbed the page | |
208 | * via the LRU. If it did, give up: shrink_cache will free it. | |
209 | */ | |
210 | void release_pages(struct page **pages, int nr, int cold) | |
211 | { | |
212 | int i; | |
213 | struct pagevec pages_to_free; | |
214 | struct zone *zone = NULL; | |
215 | ||
216 | pagevec_init(&pages_to_free, cold); | |
217 | for (i = 0; i < nr; i++) { | |
218 | struct page *page = pages[i]; | |
219 | struct zone *pagezone; | |
220 | ||
b5810039 | 221 | if (!put_page_testzero(page)) |
1da177e4 LT |
222 | continue; |
223 | ||
224 | pagezone = page_zone(page); | |
225 | if (pagezone != zone) { | |
226 | if (zone) | |
227 | spin_unlock_irq(&zone->lru_lock); | |
228 | zone = pagezone; | |
229 | spin_lock_irq(&zone->lru_lock); | |
230 | } | |
231 | if (TestClearPageLRU(page)) | |
232 | del_page_from_lru(zone, page); | |
233 | if (page_count(page) == 0) { | |
234 | if (!pagevec_add(&pages_to_free, page)) { | |
235 | spin_unlock_irq(&zone->lru_lock); | |
236 | __pagevec_free(&pages_to_free); | |
237 | pagevec_reinit(&pages_to_free); | |
238 | zone = NULL; /* No lock is held */ | |
239 | } | |
240 | } | |
241 | } | |
242 | if (zone) | |
243 | spin_unlock_irq(&zone->lru_lock); | |
244 | ||
245 | pagevec_free(&pages_to_free); | |
246 | } | |
247 | ||
248 | /* | |
249 | * The pages which we're about to release may be in the deferred lru-addition | |
250 | * queues. That would prevent them from really being freed right now. That's | |
251 | * OK from a correctness point of view but is inefficient - those pages may be | |
252 | * cache-warm and we want to give them back to the page allocator ASAP. | |
253 | * | |
254 | * So __pagevec_release() will drain those queues here. __pagevec_lru_add() | |
255 | * and __pagevec_lru_add_active() call release_pages() directly to avoid | |
256 | * mutual recursion. | |
257 | */ | |
258 | void __pagevec_release(struct pagevec *pvec) | |
259 | { | |
260 | lru_add_drain(); | |
261 | release_pages(pvec->pages, pagevec_count(pvec), pvec->cold); | |
262 | pagevec_reinit(pvec); | |
263 | } | |
264 | ||
7f285701 SF |
265 | EXPORT_SYMBOL(__pagevec_release); |
266 | ||
1da177e4 LT |
267 | /* |
268 | * pagevec_release() for pages which are known to not be on the LRU | |
269 | * | |
270 | * This function reinitialises the caller's pagevec. | |
271 | */ | |
272 | void __pagevec_release_nonlru(struct pagevec *pvec) | |
273 | { | |
274 | int i; | |
275 | struct pagevec pages_to_free; | |
276 | ||
277 | pagevec_init(&pages_to_free, pvec->cold); | |
1da177e4 LT |
278 | for (i = 0; i < pagevec_count(pvec); i++) { |
279 | struct page *page = pvec->pages[i]; | |
280 | ||
281 | BUG_ON(PageLRU(page)); | |
282 | if (put_page_testzero(page)) | |
283 | pagevec_add(&pages_to_free, page); | |
284 | } | |
285 | pagevec_free(&pages_to_free); | |
286 | pagevec_reinit(pvec); | |
287 | } | |
288 | ||
289 | /* | |
290 | * Add the passed pages to the LRU, then drop the caller's refcount | |
291 | * on them. Reinitialises the caller's pagevec. | |
292 | */ | |
293 | void __pagevec_lru_add(struct pagevec *pvec) | |
294 | { | |
295 | int i; | |
296 | struct zone *zone = NULL; | |
297 | ||
298 | for (i = 0; i < pagevec_count(pvec); i++) { | |
299 | struct page *page = pvec->pages[i]; | |
300 | struct zone *pagezone = page_zone(page); | |
301 | ||
302 | if (pagezone != zone) { | |
303 | if (zone) | |
304 | spin_unlock_irq(&zone->lru_lock); | |
305 | zone = pagezone; | |
306 | spin_lock_irq(&zone->lru_lock); | |
307 | } | |
308 | if (TestSetPageLRU(page)) | |
309 | BUG(); | |
310 | add_page_to_inactive_list(zone, page); | |
311 | } | |
312 | if (zone) | |
313 | spin_unlock_irq(&zone->lru_lock); | |
314 | release_pages(pvec->pages, pvec->nr, pvec->cold); | |
315 | pagevec_reinit(pvec); | |
316 | } | |
317 | ||
318 | EXPORT_SYMBOL(__pagevec_lru_add); | |
319 | ||
320 | void __pagevec_lru_add_active(struct pagevec *pvec) | |
321 | { | |
322 | int i; | |
323 | struct zone *zone = NULL; | |
324 | ||
325 | for (i = 0; i < pagevec_count(pvec); i++) { | |
326 | struct page *page = pvec->pages[i]; | |
327 | struct zone *pagezone = page_zone(page); | |
328 | ||
329 | if (pagezone != zone) { | |
330 | if (zone) | |
331 | spin_unlock_irq(&zone->lru_lock); | |
332 | zone = pagezone; | |
333 | spin_lock_irq(&zone->lru_lock); | |
334 | } | |
335 | if (TestSetPageLRU(page)) | |
336 | BUG(); | |
337 | if (TestSetPageActive(page)) | |
338 | BUG(); | |
339 | add_page_to_active_list(zone, page); | |
340 | } | |
341 | if (zone) | |
342 | spin_unlock_irq(&zone->lru_lock); | |
343 | release_pages(pvec->pages, pvec->nr, pvec->cold); | |
344 | pagevec_reinit(pvec); | |
345 | } | |
346 | ||
347 | /* | |
348 | * Try to drop buffers from the pages in a pagevec | |
349 | */ | |
350 | void pagevec_strip(struct pagevec *pvec) | |
351 | { | |
352 | int i; | |
353 | ||
354 | for (i = 0; i < pagevec_count(pvec); i++) { | |
355 | struct page *page = pvec->pages[i]; | |
356 | ||
357 | if (PagePrivate(page) && !TestSetPageLocked(page)) { | |
358 | try_to_release_page(page, 0); | |
359 | unlock_page(page); | |
360 | } | |
361 | } | |
362 | } | |
363 | ||
364 | /** | |
365 | * pagevec_lookup - gang pagecache lookup | |
366 | * @pvec: Where the resulting pages are placed | |
367 | * @mapping: The address_space to search | |
368 | * @start: The starting page index | |
369 | * @nr_pages: The maximum number of pages | |
370 | * | |
371 | * pagevec_lookup() will search for and return a group of up to @nr_pages pages | |
372 | * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a | |
373 | * reference against the pages in @pvec. | |
374 | * | |
375 | * The search returns a group of mapping-contiguous pages with ascending | |
376 | * indexes. There may be holes in the indices due to not-present pages. | |
377 | * | |
378 | * pagevec_lookup() returns the number of pages which were found. | |
379 | */ | |
380 | unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping, | |
381 | pgoff_t start, unsigned nr_pages) | |
382 | { | |
383 | pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages); | |
384 | return pagevec_count(pvec); | |
385 | } | |
386 | ||
387 | unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping, | |
388 | pgoff_t *index, int tag, unsigned nr_pages) | |
389 | { | |
390 | pvec->nr = find_get_pages_tag(mapping, index, tag, | |
391 | nr_pages, pvec->pages); | |
392 | return pagevec_count(pvec); | |
393 | } | |
394 | ||
7f285701 | 395 | EXPORT_SYMBOL(pagevec_lookup_tag); |
1da177e4 LT |
396 | |
397 | #ifdef CONFIG_SMP | |
398 | /* | |
399 | * We tolerate a little inaccuracy to avoid ping-ponging the counter between | |
400 | * CPUs | |
401 | */ | |
402 | #define ACCT_THRESHOLD max(16, NR_CPUS * 2) | |
403 | ||
404 | static DEFINE_PER_CPU(long, committed_space) = 0; | |
405 | ||
406 | void vm_acct_memory(long pages) | |
407 | { | |
408 | long *local; | |
409 | ||
410 | preempt_disable(); | |
411 | local = &__get_cpu_var(committed_space); | |
412 | *local += pages; | |
413 | if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) { | |
414 | atomic_add(*local, &vm_committed_space); | |
415 | *local = 0; | |
416 | } | |
417 | preempt_enable(); | |
418 | } | |
1da177e4 LT |
419 | |
420 | #ifdef CONFIG_HOTPLUG_CPU | |
1da177e4 LT |
421 | |
422 | /* Drop the CPU's cached committed space back into the central pool. */ | |
423 | static int cpu_swap_callback(struct notifier_block *nfb, | |
424 | unsigned long action, | |
425 | void *hcpu) | |
426 | { | |
427 | long *committed; | |
428 | ||
429 | committed = &per_cpu(committed_space, (long)hcpu); | |
430 | if (action == CPU_DEAD) { | |
431 | atomic_add(*committed, &vm_committed_space); | |
432 | *committed = 0; | |
80bfed90 | 433 | __lru_add_drain((long)hcpu); |
1da177e4 LT |
434 | } |
435 | return NOTIFY_OK; | |
436 | } | |
437 | #endif /* CONFIG_HOTPLUG_CPU */ | |
438 | #endif /* CONFIG_SMP */ | |
439 | ||
440 | #ifdef CONFIG_SMP | |
441 | void percpu_counter_mod(struct percpu_counter *fbc, long amount) | |
442 | { | |
443 | long count; | |
444 | long *pcount; | |
445 | int cpu = get_cpu(); | |
446 | ||
447 | pcount = per_cpu_ptr(fbc->counters, cpu); | |
448 | count = *pcount + amount; | |
449 | if (count >= FBC_BATCH || count <= -FBC_BATCH) { | |
450 | spin_lock(&fbc->lock); | |
451 | fbc->count += count; | |
452 | spin_unlock(&fbc->lock); | |
453 | count = 0; | |
454 | } | |
455 | *pcount = count; | |
456 | put_cpu(); | |
457 | } | |
458 | EXPORT_SYMBOL(percpu_counter_mod); | |
459 | #endif | |
460 | ||
461 | /* | |
462 | * Perform any setup for the swap system | |
463 | */ | |
464 | void __init swap_setup(void) | |
465 | { | |
466 | unsigned long megs = num_physpages >> (20 - PAGE_SHIFT); | |
467 | ||
468 | /* Use a smaller cluster for small-memory machines */ | |
469 | if (megs < 16) | |
470 | page_cluster = 2; | |
471 | else | |
472 | page_cluster = 3; | |
473 | /* | |
474 | * Right now other parts of the system means that we | |
475 | * _really_ don't want to cluster much more | |
476 | */ | |
477 | hotcpu_notifier(cpu_swap_callback, 0); | |
478 | } |