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1da177e4 LT |
1 | /* |
2 | * linux/mm/vmscan.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds | |
5 | * | |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. | |
7 | * kswapd added: 7.1.96 sct | |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed | |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. | |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). | |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. | |
12 | */ | |
13 | ||
14 | #include <linux/mm.h> | |
15 | #include <linux/module.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/kernel_stat.h> | |
18 | #include <linux/swap.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/highmem.h> | |
22 | #include <linux/file.h> | |
23 | #include <linux/writeback.h> | |
24 | #include <linux/blkdev.h> | |
25 | #include <linux/buffer_head.h> /* for try_to_release_page(), | |
26 | buffer_heads_over_limit */ | |
27 | #include <linux/mm_inline.h> | |
28 | #include <linux/pagevec.h> | |
29 | #include <linux/backing-dev.h> | |
30 | #include <linux/rmap.h> | |
31 | #include <linux/topology.h> | |
32 | #include <linux/cpu.h> | |
33 | #include <linux/cpuset.h> | |
34 | #include <linux/notifier.h> | |
35 | #include <linux/rwsem.h> | |
36 | ||
37 | #include <asm/tlbflush.h> | |
38 | #include <asm/div64.h> | |
39 | ||
40 | #include <linux/swapops.h> | |
41 | ||
42 | /* possible outcome of pageout() */ | |
43 | typedef enum { | |
44 | /* failed to write page out, page is locked */ | |
45 | PAGE_KEEP, | |
46 | /* move page to the active list, page is locked */ | |
47 | PAGE_ACTIVATE, | |
48 | /* page has been sent to the disk successfully, page is unlocked */ | |
49 | PAGE_SUCCESS, | |
50 | /* page is clean and locked */ | |
51 | PAGE_CLEAN, | |
52 | } pageout_t; | |
53 | ||
54 | struct scan_control { | |
55 | /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */ | |
56 | unsigned long nr_to_scan; | |
57 | ||
58 | /* Incremented by the number of inactive pages that were scanned */ | |
59 | unsigned long nr_scanned; | |
60 | ||
61 | /* Incremented by the number of pages reclaimed */ | |
62 | unsigned long nr_reclaimed; | |
63 | ||
64 | unsigned long nr_mapped; /* From page_state */ | |
65 | ||
1da177e4 LT |
66 | /* Ask shrink_caches, or shrink_zone to scan at this priority */ |
67 | unsigned int priority; | |
68 | ||
69 | /* This context's GFP mask */ | |
6daa0e28 | 70 | gfp_t gfp_mask; |
1da177e4 LT |
71 | |
72 | int may_writepage; | |
73 | ||
f1fd1067 CL |
74 | /* Can pages be swapped as part of reclaim? */ |
75 | int may_swap; | |
76 | ||
1da177e4 LT |
77 | /* This context's SWAP_CLUSTER_MAX. If freeing memory for |
78 | * suspend, we effectively ignore SWAP_CLUSTER_MAX. | |
79 | * In this context, it doesn't matter that we scan the | |
80 | * whole list at once. */ | |
81 | int swap_cluster_max; | |
82 | }; | |
83 | ||
84 | /* | |
85 | * The list of shrinker callbacks used by to apply pressure to | |
86 | * ageable caches. | |
87 | */ | |
88 | struct shrinker { | |
89 | shrinker_t shrinker; | |
90 | struct list_head list; | |
91 | int seeks; /* seeks to recreate an obj */ | |
92 | long nr; /* objs pending delete */ | |
93 | }; | |
94 | ||
95 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
96 | ||
97 | #ifdef ARCH_HAS_PREFETCH | |
98 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
99 | do { \ | |
100 | if ((_page)->lru.prev != _base) { \ | |
101 | struct page *prev; \ | |
102 | \ | |
103 | prev = lru_to_page(&(_page->lru)); \ | |
104 | prefetch(&prev->_field); \ | |
105 | } \ | |
106 | } while (0) | |
107 | #else | |
108 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
109 | #endif | |
110 | ||
111 | #ifdef ARCH_HAS_PREFETCHW | |
112 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
113 | do { \ | |
114 | if ((_page)->lru.prev != _base) { \ | |
115 | struct page *prev; \ | |
116 | \ | |
117 | prev = lru_to_page(&(_page->lru)); \ | |
118 | prefetchw(&prev->_field); \ | |
119 | } \ | |
120 | } while (0) | |
121 | #else | |
122 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
123 | #endif | |
124 | ||
125 | /* | |
126 | * From 0 .. 100. Higher means more swappy. | |
127 | */ | |
128 | int vm_swappiness = 60; | |
129 | static long total_memory; | |
130 | ||
131 | static LIST_HEAD(shrinker_list); | |
132 | static DECLARE_RWSEM(shrinker_rwsem); | |
133 | ||
134 | /* | |
135 | * Add a shrinker callback to be called from the vm | |
136 | */ | |
137 | struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) | |
138 | { | |
139 | struct shrinker *shrinker; | |
140 | ||
141 | shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); | |
142 | if (shrinker) { | |
143 | shrinker->shrinker = theshrinker; | |
144 | shrinker->seeks = seeks; | |
145 | shrinker->nr = 0; | |
146 | down_write(&shrinker_rwsem); | |
147 | list_add_tail(&shrinker->list, &shrinker_list); | |
148 | up_write(&shrinker_rwsem); | |
149 | } | |
150 | return shrinker; | |
151 | } | |
152 | EXPORT_SYMBOL(set_shrinker); | |
153 | ||
154 | /* | |
155 | * Remove one | |
156 | */ | |
157 | void remove_shrinker(struct shrinker *shrinker) | |
158 | { | |
159 | down_write(&shrinker_rwsem); | |
160 | list_del(&shrinker->list); | |
161 | up_write(&shrinker_rwsem); | |
162 | kfree(shrinker); | |
163 | } | |
164 | EXPORT_SYMBOL(remove_shrinker); | |
165 | ||
166 | #define SHRINK_BATCH 128 | |
167 | /* | |
168 | * Call the shrink functions to age shrinkable caches | |
169 | * | |
170 | * Here we assume it costs one seek to replace a lru page and that it also | |
171 | * takes a seek to recreate a cache object. With this in mind we age equal | |
172 | * percentages of the lru and ageable caches. This should balance the seeks | |
173 | * generated by these structures. | |
174 | * | |
175 | * If the vm encounted mapped pages on the LRU it increase the pressure on | |
176 | * slab to avoid swapping. | |
177 | * | |
178 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
179 | * | |
180 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
181 | * are eligible for the caller's allocation attempt. It is used for balancing | |
182 | * slab reclaim versus page reclaim. | |
b15e0905 | 183 | * |
184 | * Returns the number of slab objects which we shrunk. | |
1da177e4 | 185 | */ |
9d0243bc | 186 | int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages) |
1da177e4 LT |
187 | { |
188 | struct shrinker *shrinker; | |
b15e0905 | 189 | int ret = 0; |
1da177e4 LT |
190 | |
191 | if (scanned == 0) | |
192 | scanned = SWAP_CLUSTER_MAX; | |
193 | ||
194 | if (!down_read_trylock(&shrinker_rwsem)) | |
b15e0905 | 195 | return 1; /* Assume we'll be able to shrink next time */ |
1da177e4 LT |
196 | |
197 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
198 | unsigned long long delta; | |
199 | unsigned long total_scan; | |
ea164d73 | 200 | unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
201 | |
202 | delta = (4 * scanned) / shrinker->seeks; | |
ea164d73 | 203 | delta *= max_pass; |
1da177e4 LT |
204 | do_div(delta, lru_pages + 1); |
205 | shrinker->nr += delta; | |
ea164d73 AA |
206 | if (shrinker->nr < 0) { |
207 | printk(KERN_ERR "%s: nr=%ld\n", | |
208 | __FUNCTION__, shrinker->nr); | |
209 | shrinker->nr = max_pass; | |
210 | } | |
211 | ||
212 | /* | |
213 | * Avoid risking looping forever due to too large nr value: | |
214 | * never try to free more than twice the estimate number of | |
215 | * freeable entries. | |
216 | */ | |
217 | if (shrinker->nr > max_pass * 2) | |
218 | shrinker->nr = max_pass * 2; | |
1da177e4 LT |
219 | |
220 | total_scan = shrinker->nr; | |
221 | shrinker->nr = 0; | |
222 | ||
223 | while (total_scan >= SHRINK_BATCH) { | |
224 | long this_scan = SHRINK_BATCH; | |
225 | int shrink_ret; | |
b15e0905 | 226 | int nr_before; |
1da177e4 | 227 | |
b15e0905 | 228 | nr_before = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
229 | shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); |
230 | if (shrink_ret == -1) | |
231 | break; | |
b15e0905 | 232 | if (shrink_ret < nr_before) |
233 | ret += nr_before - shrink_ret; | |
1da177e4 LT |
234 | mod_page_state(slabs_scanned, this_scan); |
235 | total_scan -= this_scan; | |
236 | ||
237 | cond_resched(); | |
238 | } | |
239 | ||
240 | shrinker->nr += total_scan; | |
241 | } | |
242 | up_read(&shrinker_rwsem); | |
b15e0905 | 243 | return ret; |
1da177e4 LT |
244 | } |
245 | ||
246 | /* Called without lock on whether page is mapped, so answer is unstable */ | |
247 | static inline int page_mapping_inuse(struct page *page) | |
248 | { | |
249 | struct address_space *mapping; | |
250 | ||
251 | /* Page is in somebody's page tables. */ | |
252 | if (page_mapped(page)) | |
253 | return 1; | |
254 | ||
255 | /* Be more reluctant to reclaim swapcache than pagecache */ | |
256 | if (PageSwapCache(page)) | |
257 | return 1; | |
258 | ||
259 | mapping = page_mapping(page); | |
260 | if (!mapping) | |
261 | return 0; | |
262 | ||
263 | /* File is mmap'd by somebody? */ | |
264 | return mapping_mapped(mapping); | |
265 | } | |
266 | ||
267 | static inline int is_page_cache_freeable(struct page *page) | |
268 | { | |
269 | return page_count(page) - !!PagePrivate(page) == 2; | |
270 | } | |
271 | ||
272 | static int may_write_to_queue(struct backing_dev_info *bdi) | |
273 | { | |
930d9152 | 274 | if (current->flags & PF_SWAPWRITE) |
1da177e4 LT |
275 | return 1; |
276 | if (!bdi_write_congested(bdi)) | |
277 | return 1; | |
278 | if (bdi == current->backing_dev_info) | |
279 | return 1; | |
280 | return 0; | |
281 | } | |
282 | ||
283 | /* | |
284 | * We detected a synchronous write error writing a page out. Probably | |
285 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
286 | * fsync(), msync() or close(). | |
287 | * | |
288 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
289 | * prevents it from being freed up. But we have a ref on the page and once | |
290 | * that page is locked, the mapping is pinned. | |
291 | * | |
292 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
293 | * __GFP_FS. | |
294 | */ | |
295 | static void handle_write_error(struct address_space *mapping, | |
296 | struct page *page, int error) | |
297 | { | |
298 | lock_page(page); | |
299 | if (page_mapping(page) == mapping) { | |
300 | if (error == -ENOSPC) | |
301 | set_bit(AS_ENOSPC, &mapping->flags); | |
302 | else | |
303 | set_bit(AS_EIO, &mapping->flags); | |
304 | } | |
305 | unlock_page(page); | |
306 | } | |
307 | ||
308 | /* | |
309 | * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). | |
310 | */ | |
311 | static pageout_t pageout(struct page *page, struct address_space *mapping) | |
312 | { | |
313 | /* | |
314 | * If the page is dirty, only perform writeback if that write | |
315 | * will be non-blocking. To prevent this allocation from being | |
316 | * stalled by pagecache activity. But note that there may be | |
317 | * stalls if we need to run get_block(). We could test | |
318 | * PagePrivate for that. | |
319 | * | |
320 | * If this process is currently in generic_file_write() against | |
321 | * this page's queue, we can perform writeback even if that | |
322 | * will block. | |
323 | * | |
324 | * If the page is swapcache, write it back even if that would | |
325 | * block, for some throttling. This happens by accident, because | |
326 | * swap_backing_dev_info is bust: it doesn't reflect the | |
327 | * congestion state of the swapdevs. Easy to fix, if needed. | |
328 | * See swapfile.c:page_queue_congested(). | |
329 | */ | |
330 | if (!is_page_cache_freeable(page)) | |
331 | return PAGE_KEEP; | |
332 | if (!mapping) { | |
333 | /* | |
334 | * Some data journaling orphaned pages can have | |
335 | * page->mapping == NULL while being dirty with clean buffers. | |
336 | */ | |
323aca6c | 337 | if (PagePrivate(page)) { |
1da177e4 LT |
338 | if (try_to_free_buffers(page)) { |
339 | ClearPageDirty(page); | |
340 | printk("%s: orphaned page\n", __FUNCTION__); | |
341 | return PAGE_CLEAN; | |
342 | } | |
343 | } | |
344 | return PAGE_KEEP; | |
345 | } | |
346 | if (mapping->a_ops->writepage == NULL) | |
347 | return PAGE_ACTIVATE; | |
348 | if (!may_write_to_queue(mapping->backing_dev_info)) | |
349 | return PAGE_KEEP; | |
350 | ||
351 | if (clear_page_dirty_for_io(page)) { | |
352 | int res; | |
353 | struct writeback_control wbc = { | |
354 | .sync_mode = WB_SYNC_NONE, | |
355 | .nr_to_write = SWAP_CLUSTER_MAX, | |
356 | .nonblocking = 1, | |
357 | .for_reclaim = 1, | |
358 | }; | |
359 | ||
360 | SetPageReclaim(page); | |
361 | res = mapping->a_ops->writepage(page, &wbc); | |
362 | if (res < 0) | |
363 | handle_write_error(mapping, page, res); | |
994fc28c | 364 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
1da177e4 LT |
365 | ClearPageReclaim(page); |
366 | return PAGE_ACTIVATE; | |
367 | } | |
368 | if (!PageWriteback(page)) { | |
369 | /* synchronous write or broken a_ops? */ | |
370 | ClearPageReclaim(page); | |
371 | } | |
372 | ||
373 | return PAGE_SUCCESS; | |
374 | } | |
375 | ||
376 | return PAGE_CLEAN; | |
377 | } | |
378 | ||
49d2e9cc CL |
379 | static int remove_mapping(struct address_space *mapping, struct page *page) |
380 | { | |
381 | if (!mapping) | |
382 | return 0; /* truncate got there first */ | |
383 | ||
384 | write_lock_irq(&mapping->tree_lock); | |
385 | ||
386 | /* | |
387 | * The non-racy check for busy page. It is critical to check | |
388 | * PageDirty _after_ making sure that the page is freeable and | |
389 | * not in use by anybody. (pagecache + us == 2) | |
390 | */ | |
391 | if (unlikely(page_count(page) != 2)) | |
392 | goto cannot_free; | |
393 | smp_rmb(); | |
394 | if (unlikely(PageDirty(page))) | |
395 | goto cannot_free; | |
396 | ||
397 | if (PageSwapCache(page)) { | |
398 | swp_entry_t swap = { .val = page_private(page) }; | |
399 | __delete_from_swap_cache(page); | |
400 | write_unlock_irq(&mapping->tree_lock); | |
401 | swap_free(swap); | |
402 | __put_page(page); /* The pagecache ref */ | |
403 | return 1; | |
404 | } | |
405 | ||
406 | __remove_from_page_cache(page); | |
407 | write_unlock_irq(&mapping->tree_lock); | |
408 | __put_page(page); | |
409 | return 1; | |
410 | ||
411 | cannot_free: | |
412 | write_unlock_irq(&mapping->tree_lock); | |
413 | return 0; | |
414 | } | |
415 | ||
1da177e4 LT |
416 | /* |
417 | * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed | |
418 | */ | |
419 | static int shrink_list(struct list_head *page_list, struct scan_control *sc) | |
420 | { | |
421 | LIST_HEAD(ret_pages); | |
422 | struct pagevec freed_pvec; | |
423 | int pgactivate = 0; | |
424 | int reclaimed = 0; | |
425 | ||
426 | cond_resched(); | |
427 | ||
428 | pagevec_init(&freed_pvec, 1); | |
429 | while (!list_empty(page_list)) { | |
430 | struct address_space *mapping; | |
431 | struct page *page; | |
432 | int may_enter_fs; | |
433 | int referenced; | |
434 | ||
435 | cond_resched(); | |
436 | ||
437 | page = lru_to_page(page_list); | |
438 | list_del(&page->lru); | |
439 | ||
440 | if (TestSetPageLocked(page)) | |
441 | goto keep; | |
442 | ||
443 | BUG_ON(PageActive(page)); | |
444 | ||
445 | sc->nr_scanned++; | |
446 | /* Double the slab pressure for mapped and swapcache pages */ | |
447 | if (page_mapped(page) || PageSwapCache(page)) | |
448 | sc->nr_scanned++; | |
449 | ||
450 | if (PageWriteback(page)) | |
451 | goto keep_locked; | |
452 | ||
f7b7fd8f | 453 | referenced = page_referenced(page, 1); |
1da177e4 LT |
454 | /* In active use or really unfreeable? Activate it. */ |
455 | if (referenced && page_mapping_inuse(page)) | |
456 | goto activate_locked; | |
457 | ||
458 | #ifdef CONFIG_SWAP | |
459 | /* | |
460 | * Anonymous process memory has backing store? | |
461 | * Try to allocate it some swap space here. | |
462 | */ | |
c340010e | 463 | if (PageAnon(page) && !PageSwapCache(page)) { |
f1fd1067 CL |
464 | if (!sc->may_swap) |
465 | goto keep_locked; | |
1480a540 | 466 | if (!add_to_swap(page, GFP_ATOMIC)) |
1da177e4 LT |
467 | goto activate_locked; |
468 | } | |
469 | #endif /* CONFIG_SWAP */ | |
470 | ||
471 | mapping = page_mapping(page); | |
472 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || | |
473 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
474 | ||
475 | /* | |
476 | * The page is mapped into the page tables of one or more | |
477 | * processes. Try to unmap it here. | |
478 | */ | |
479 | if (page_mapped(page) && mapping) { | |
480 | switch (try_to_unmap(page)) { | |
481 | case SWAP_FAIL: | |
482 | goto activate_locked; | |
483 | case SWAP_AGAIN: | |
484 | goto keep_locked; | |
485 | case SWAP_SUCCESS: | |
486 | ; /* try to free the page below */ | |
487 | } | |
488 | } | |
489 | ||
490 | if (PageDirty(page)) { | |
491 | if (referenced) | |
492 | goto keep_locked; | |
493 | if (!may_enter_fs) | |
494 | goto keep_locked; | |
52a8363e | 495 | if (!sc->may_writepage) |
1da177e4 LT |
496 | goto keep_locked; |
497 | ||
498 | /* Page is dirty, try to write it out here */ | |
499 | switch(pageout(page, mapping)) { | |
500 | case PAGE_KEEP: | |
501 | goto keep_locked; | |
502 | case PAGE_ACTIVATE: | |
503 | goto activate_locked; | |
504 | case PAGE_SUCCESS: | |
505 | if (PageWriteback(page) || PageDirty(page)) | |
506 | goto keep; | |
507 | /* | |
508 | * A synchronous write - probably a ramdisk. Go | |
509 | * ahead and try to reclaim the page. | |
510 | */ | |
511 | if (TestSetPageLocked(page)) | |
512 | goto keep; | |
513 | if (PageDirty(page) || PageWriteback(page)) | |
514 | goto keep_locked; | |
515 | mapping = page_mapping(page); | |
516 | case PAGE_CLEAN: | |
517 | ; /* try to free the page below */ | |
518 | } | |
519 | } | |
520 | ||
521 | /* | |
522 | * If the page has buffers, try to free the buffer mappings | |
523 | * associated with this page. If we succeed we try to free | |
524 | * the page as well. | |
525 | * | |
526 | * We do this even if the page is PageDirty(). | |
527 | * try_to_release_page() does not perform I/O, but it is | |
528 | * possible for a page to have PageDirty set, but it is actually | |
529 | * clean (all its buffers are clean). This happens if the | |
530 | * buffers were written out directly, with submit_bh(). ext3 | |
531 | * will do this, as well as the blockdev mapping. | |
532 | * try_to_release_page() will discover that cleanness and will | |
533 | * drop the buffers and mark the page clean - it can be freed. | |
534 | * | |
535 | * Rarely, pages can have buffers and no ->mapping. These are | |
536 | * the pages which were not successfully invalidated in | |
537 | * truncate_complete_page(). We try to drop those buffers here | |
538 | * and if that worked, and the page is no longer mapped into | |
539 | * process address space (page_count == 1) it can be freed. | |
540 | * Otherwise, leave the page on the LRU so it is swappable. | |
541 | */ | |
542 | if (PagePrivate(page)) { | |
543 | if (!try_to_release_page(page, sc->gfp_mask)) | |
544 | goto activate_locked; | |
545 | if (!mapping && page_count(page) == 1) | |
546 | goto free_it; | |
547 | } | |
548 | ||
49d2e9cc CL |
549 | if (!remove_mapping(mapping, page)) |
550 | goto keep_locked; | |
1da177e4 LT |
551 | |
552 | free_it: | |
553 | unlock_page(page); | |
554 | reclaimed++; | |
555 | if (!pagevec_add(&freed_pvec, page)) | |
556 | __pagevec_release_nonlru(&freed_pvec); | |
557 | continue; | |
558 | ||
559 | activate_locked: | |
560 | SetPageActive(page); | |
561 | pgactivate++; | |
562 | keep_locked: | |
563 | unlock_page(page); | |
564 | keep: | |
565 | list_add(&page->lru, &ret_pages); | |
566 | BUG_ON(PageLRU(page)); | |
567 | } | |
568 | list_splice(&ret_pages, page_list); | |
569 | if (pagevec_count(&freed_pvec)) | |
570 | __pagevec_release_nonlru(&freed_pvec); | |
571 | mod_page_state(pgactivate, pgactivate); | |
572 | sc->nr_reclaimed += reclaimed; | |
573 | return reclaimed; | |
574 | } | |
575 | ||
7cbe34cf | 576 | #ifdef CONFIG_MIGRATION |
8419c318 CL |
577 | static inline void move_to_lru(struct page *page) |
578 | { | |
579 | list_del(&page->lru); | |
580 | if (PageActive(page)) { | |
581 | /* | |
582 | * lru_cache_add_active checks that | |
583 | * the PG_active bit is off. | |
584 | */ | |
585 | ClearPageActive(page); | |
586 | lru_cache_add_active(page); | |
587 | } else { | |
588 | lru_cache_add(page); | |
589 | } | |
590 | put_page(page); | |
591 | } | |
592 | ||
593 | /* | |
053837fc | 594 | * Add isolated pages on the list back to the LRU. |
8419c318 CL |
595 | * |
596 | * returns the number of pages put back. | |
597 | */ | |
598 | int putback_lru_pages(struct list_head *l) | |
599 | { | |
600 | struct page *page; | |
601 | struct page *page2; | |
602 | int count = 0; | |
603 | ||
604 | list_for_each_entry_safe(page, page2, l, lru) { | |
605 | move_to_lru(page); | |
606 | count++; | |
607 | } | |
608 | return count; | |
609 | } | |
610 | ||
49d2e9cc CL |
611 | /* |
612 | * swapout a single page | |
613 | * page is locked upon entry, unlocked on exit | |
49d2e9cc CL |
614 | */ |
615 | static int swap_page(struct page *page) | |
616 | { | |
617 | struct address_space *mapping = page_mapping(page); | |
618 | ||
619 | if (page_mapped(page) && mapping) | |
620 | if (try_to_unmap(page) != SWAP_SUCCESS) | |
621 | goto unlock_retry; | |
622 | ||
623 | if (PageDirty(page)) { | |
624 | /* Page is dirty, try to write it out here */ | |
625 | switch(pageout(page, mapping)) { | |
626 | case PAGE_KEEP: | |
627 | case PAGE_ACTIVATE: | |
628 | goto unlock_retry; | |
629 | ||
630 | case PAGE_SUCCESS: | |
631 | goto retry; | |
632 | ||
633 | case PAGE_CLEAN: | |
634 | ; /* try to free the page below */ | |
635 | } | |
636 | } | |
637 | ||
638 | if (PagePrivate(page)) { | |
639 | if (!try_to_release_page(page, GFP_KERNEL) || | |
640 | (!mapping && page_count(page) == 1)) | |
641 | goto unlock_retry; | |
642 | } | |
643 | ||
644 | if (remove_mapping(mapping, page)) { | |
645 | /* Success */ | |
646 | unlock_page(page); | |
647 | return 0; | |
648 | } | |
649 | ||
650 | unlock_retry: | |
651 | unlock_page(page); | |
652 | ||
653 | retry: | |
d0d96328 | 654 | return -EAGAIN; |
49d2e9cc CL |
655 | } |
656 | /* | |
657 | * migrate_pages | |
658 | * | |
659 | * Two lists are passed to this function. The first list | |
660 | * contains the pages isolated from the LRU to be migrated. | |
661 | * The second list contains new pages that the pages isolated | |
662 | * can be moved to. If the second list is NULL then all | |
663 | * pages are swapped out. | |
664 | * | |
665 | * The function returns after 10 attempts or if no pages | |
666 | * are movable anymore because t has become empty | |
667 | * or no retryable pages exist anymore. | |
668 | * | |
669 | * SIMPLIFIED VERSION: This implementation of migrate_pages | |
670 | * is only swapping out pages and never touches the second | |
671 | * list. The direct migration patchset | |
672 | * extends this function to avoid the use of swap. | |
d0d96328 CL |
673 | * |
674 | * Return: Number of pages not migrated when "to" ran empty. | |
49d2e9cc | 675 | */ |
d4984711 CL |
676 | int migrate_pages(struct list_head *from, struct list_head *to, |
677 | struct list_head *moved, struct list_head *failed) | |
49d2e9cc CL |
678 | { |
679 | int retry; | |
49d2e9cc CL |
680 | int nr_failed = 0; |
681 | int pass = 0; | |
682 | struct page *page; | |
683 | struct page *page2; | |
684 | int swapwrite = current->flags & PF_SWAPWRITE; | |
d0d96328 | 685 | int rc; |
49d2e9cc CL |
686 | |
687 | if (!swapwrite) | |
688 | current->flags |= PF_SWAPWRITE; | |
689 | ||
690 | redo: | |
691 | retry = 0; | |
692 | ||
d4984711 | 693 | list_for_each_entry_safe(page, page2, from, lru) { |
49d2e9cc CL |
694 | cond_resched(); |
695 | ||
d0d96328 CL |
696 | rc = 0; |
697 | if (page_count(page) == 1) | |
ee27497d | 698 | /* page was freed from under us. So we are done. */ |
d0d96328 CL |
699 | goto next; |
700 | ||
49d2e9cc CL |
701 | /* |
702 | * Skip locked pages during the first two passes to give the | |
7cbe34cf CL |
703 | * functions holding the lock time to release the page. Later we |
704 | * use lock_page() to have a higher chance of acquiring the | |
705 | * lock. | |
49d2e9cc | 706 | */ |
d0d96328 | 707 | rc = -EAGAIN; |
49d2e9cc CL |
708 | if (pass > 2) |
709 | lock_page(page); | |
710 | else | |
711 | if (TestSetPageLocked(page)) | |
d0d96328 | 712 | goto next; |
49d2e9cc CL |
713 | |
714 | /* | |
715 | * Only wait on writeback if we have already done a pass where | |
716 | * we we may have triggered writeouts for lots of pages. | |
717 | */ | |
7cbe34cf | 718 | if (pass > 0) { |
49d2e9cc | 719 | wait_on_page_writeback(page); |
7cbe34cf | 720 | } else { |
d0d96328 CL |
721 | if (PageWriteback(page)) |
722 | goto unlock_page; | |
7cbe34cf | 723 | } |
49d2e9cc | 724 | |
d0d96328 CL |
725 | /* |
726 | * Anonymous pages must have swap cache references otherwise | |
727 | * the information contained in the page maps cannot be | |
728 | * preserved. | |
729 | */ | |
49d2e9cc | 730 | if (PageAnon(page) && !PageSwapCache(page)) { |
1480a540 | 731 | if (!add_to_swap(page, GFP_KERNEL)) { |
d0d96328 CL |
732 | rc = -ENOMEM; |
733 | goto unlock_page; | |
49d2e9cc CL |
734 | } |
735 | } | |
49d2e9cc CL |
736 | |
737 | /* | |
738 | * Page is properly locked and writeback is complete. | |
739 | * Try to migrate the page. | |
740 | */ | |
d0d96328 CL |
741 | rc = swap_page(page); |
742 | goto next; | |
743 | ||
744 | unlock_page: | |
745 | unlock_page(page); | |
746 | ||
747 | next: | |
748 | if (rc == -EAGAIN) { | |
749 | retry++; | |
750 | } else if (rc) { | |
751 | /* Permanent failure */ | |
752 | list_move(&page->lru, failed); | |
753 | nr_failed++; | |
754 | } else { | |
755 | /* Success */ | |
d4984711 | 756 | list_move(&page->lru, moved); |
d4984711 | 757 | } |
49d2e9cc CL |
758 | } |
759 | if (retry && pass++ < 10) | |
760 | goto redo; | |
761 | ||
762 | if (!swapwrite) | |
763 | current->flags &= ~PF_SWAPWRITE; | |
764 | ||
49d2e9cc CL |
765 | return nr_failed + retry; |
766 | } | |
8419c318 | 767 | |
8419c318 CL |
768 | /* |
769 | * Isolate one page from the LRU lists and put it on the | |
053837fc | 770 | * indicated list with elevated refcount. |
8419c318 CL |
771 | * |
772 | * Result: | |
773 | * 0 = page not on LRU list | |
774 | * 1 = page removed from LRU list and added to the specified list. | |
8419c318 CL |
775 | */ |
776 | int isolate_lru_page(struct page *page) | |
777 | { | |
053837fc | 778 | int ret = 0; |
8419c318 | 779 | |
053837fc NP |
780 | if (PageLRU(page)) { |
781 | struct zone *zone = page_zone(page); | |
782 | spin_lock_irq(&zone->lru_lock); | |
783 | if (TestClearPageLRU(page)) { | |
784 | ret = 1; | |
785 | get_page(page); | |
786 | if (PageActive(page)) | |
787 | del_page_from_active_list(zone, page); | |
788 | else | |
789 | del_page_from_inactive_list(zone, page); | |
790 | } | |
791 | spin_unlock_irq(&zone->lru_lock); | |
8419c318 | 792 | } |
053837fc NP |
793 | |
794 | return ret; | |
8419c318 | 795 | } |
7cbe34cf | 796 | #endif |
49d2e9cc | 797 | |
1da177e4 LT |
798 | /* |
799 | * zone->lru_lock is heavily contended. Some of the functions that | |
800 | * shrink the lists perform better by taking out a batch of pages | |
801 | * and working on them outside the LRU lock. | |
802 | * | |
803 | * For pagecache intensive workloads, this function is the hottest | |
804 | * spot in the kernel (apart from copy_*_user functions). | |
805 | * | |
806 | * Appropriate locks must be held before calling this function. | |
807 | * | |
808 | * @nr_to_scan: The number of pages to look through on the list. | |
809 | * @src: The LRU list to pull pages off. | |
810 | * @dst: The temp list to put pages on to. | |
811 | * @scanned: The number of pages that were scanned. | |
812 | * | |
813 | * returns how many pages were moved onto *@dst. | |
814 | */ | |
815 | static int isolate_lru_pages(int nr_to_scan, struct list_head *src, | |
816 | struct list_head *dst, int *scanned) | |
817 | { | |
818 | int nr_taken = 0; | |
819 | struct page *page; | |
820 | int scan = 0; | |
821 | ||
822 | while (scan++ < nr_to_scan && !list_empty(src)) { | |
823 | page = lru_to_page(src); | |
824 | prefetchw_prev_lru_page(page, src, flags); | |
825 | ||
053837fc | 826 | if (!TestClearPageLRU(page)) |
21eac81f | 827 | BUG(); |
053837fc NP |
828 | list_del(&page->lru); |
829 | if (get_page_testone(page)) { | |
830 | /* | |
831 | * It is being freed elsewhere | |
832 | */ | |
833 | __put_page(page); | |
834 | SetPageLRU(page); | |
835 | list_add(&page->lru, src); | |
836 | continue; | |
837 | } else { | |
838 | list_add(&page->lru, dst); | |
839 | nr_taken++; | |
1da177e4 LT |
840 | } |
841 | } | |
842 | ||
843 | *scanned = scan; | |
844 | return nr_taken; | |
845 | } | |
846 | ||
847 | /* | |
848 | * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed | |
849 | */ | |
850 | static void shrink_cache(struct zone *zone, struct scan_control *sc) | |
851 | { | |
852 | LIST_HEAD(page_list); | |
853 | struct pagevec pvec; | |
854 | int max_scan = sc->nr_to_scan; | |
855 | ||
856 | pagevec_init(&pvec, 1); | |
857 | ||
858 | lru_add_drain(); | |
859 | spin_lock_irq(&zone->lru_lock); | |
860 | while (max_scan > 0) { | |
861 | struct page *page; | |
862 | int nr_taken; | |
863 | int nr_scan; | |
864 | int nr_freed; | |
865 | ||
866 | nr_taken = isolate_lru_pages(sc->swap_cluster_max, | |
867 | &zone->inactive_list, | |
868 | &page_list, &nr_scan); | |
869 | zone->nr_inactive -= nr_taken; | |
870 | zone->pages_scanned += nr_scan; | |
871 | spin_unlock_irq(&zone->lru_lock); | |
872 | ||
873 | if (nr_taken == 0) | |
874 | goto done; | |
875 | ||
876 | max_scan -= nr_scan; | |
1da177e4 | 877 | nr_freed = shrink_list(&page_list, sc); |
1da177e4 | 878 | |
a74609fa NP |
879 | local_irq_disable(); |
880 | if (current_is_kswapd()) { | |
881 | __mod_page_state_zone(zone, pgscan_kswapd, nr_scan); | |
882 | __mod_page_state(kswapd_steal, nr_freed); | |
883 | } else | |
884 | __mod_page_state_zone(zone, pgscan_direct, nr_scan); | |
885 | __mod_page_state_zone(zone, pgsteal, nr_freed); | |
886 | ||
887 | spin_lock(&zone->lru_lock); | |
1da177e4 LT |
888 | /* |
889 | * Put back any unfreeable pages. | |
890 | */ | |
891 | while (!list_empty(&page_list)) { | |
892 | page = lru_to_page(&page_list); | |
893 | if (TestSetPageLRU(page)) | |
894 | BUG(); | |
895 | list_del(&page->lru); | |
896 | if (PageActive(page)) | |
897 | add_page_to_active_list(zone, page); | |
898 | else | |
899 | add_page_to_inactive_list(zone, page); | |
900 | if (!pagevec_add(&pvec, page)) { | |
901 | spin_unlock_irq(&zone->lru_lock); | |
902 | __pagevec_release(&pvec); | |
903 | spin_lock_irq(&zone->lru_lock); | |
904 | } | |
905 | } | |
906 | } | |
907 | spin_unlock_irq(&zone->lru_lock); | |
908 | done: | |
909 | pagevec_release(&pvec); | |
910 | } | |
911 | ||
912 | /* | |
913 | * This moves pages from the active list to the inactive list. | |
914 | * | |
915 | * We move them the other way if the page is referenced by one or more | |
916 | * processes, from rmap. | |
917 | * | |
918 | * If the pages are mostly unmapped, the processing is fast and it is | |
919 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
920 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
921 | * should drop zone->lru_lock around each page. It's impossible to balance | |
922 | * this, so instead we remove the pages from the LRU while processing them. | |
923 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
924 | * nobody will play with that bit on a non-LRU page. | |
925 | * | |
926 | * The downside is that we have to touch page->_count against each page. | |
927 | * But we had to alter page->flags anyway. | |
928 | */ | |
929 | static void | |
930 | refill_inactive_zone(struct zone *zone, struct scan_control *sc) | |
931 | { | |
932 | int pgmoved; | |
933 | int pgdeactivate = 0; | |
934 | int pgscanned; | |
935 | int nr_pages = sc->nr_to_scan; | |
936 | LIST_HEAD(l_hold); /* The pages which were snipped off */ | |
937 | LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ | |
938 | LIST_HEAD(l_active); /* Pages to go onto the active_list */ | |
939 | struct page *page; | |
940 | struct pagevec pvec; | |
941 | int reclaim_mapped = 0; | |
942 | long mapped_ratio; | |
943 | long distress; | |
944 | long swap_tendency; | |
945 | ||
946 | lru_add_drain(); | |
947 | spin_lock_irq(&zone->lru_lock); | |
948 | pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, | |
949 | &l_hold, &pgscanned); | |
950 | zone->pages_scanned += pgscanned; | |
951 | zone->nr_active -= pgmoved; | |
952 | spin_unlock_irq(&zone->lru_lock); | |
953 | ||
954 | /* | |
955 | * `distress' is a measure of how much trouble we're having reclaiming | |
956 | * pages. 0 -> no problems. 100 -> great trouble. | |
957 | */ | |
958 | distress = 100 >> zone->prev_priority; | |
959 | ||
960 | /* | |
961 | * The point of this algorithm is to decide when to start reclaiming | |
962 | * mapped memory instead of just pagecache. Work out how much memory | |
963 | * is mapped. | |
964 | */ | |
965 | mapped_ratio = (sc->nr_mapped * 100) / total_memory; | |
966 | ||
967 | /* | |
968 | * Now decide how much we really want to unmap some pages. The mapped | |
969 | * ratio is downgraded - just because there's a lot of mapped memory | |
970 | * doesn't necessarily mean that page reclaim isn't succeeding. | |
971 | * | |
972 | * The distress ratio is important - we don't want to start going oom. | |
973 | * | |
974 | * A 100% value of vm_swappiness overrides this algorithm altogether. | |
975 | */ | |
976 | swap_tendency = mapped_ratio / 2 + distress + vm_swappiness; | |
977 | ||
978 | /* | |
979 | * Now use this metric to decide whether to start moving mapped memory | |
980 | * onto the inactive list. | |
981 | */ | |
982 | if (swap_tendency >= 100) | |
983 | reclaim_mapped = 1; | |
984 | ||
985 | while (!list_empty(&l_hold)) { | |
986 | cond_resched(); | |
987 | page = lru_to_page(&l_hold); | |
988 | list_del(&page->lru); | |
989 | if (page_mapped(page)) { | |
990 | if (!reclaim_mapped || | |
991 | (total_swap_pages == 0 && PageAnon(page)) || | |
f7b7fd8f | 992 | page_referenced(page, 0)) { |
1da177e4 LT |
993 | list_add(&page->lru, &l_active); |
994 | continue; | |
995 | } | |
996 | } | |
997 | list_add(&page->lru, &l_inactive); | |
998 | } | |
999 | ||
1000 | pagevec_init(&pvec, 1); | |
1001 | pgmoved = 0; | |
1002 | spin_lock_irq(&zone->lru_lock); | |
1003 | while (!list_empty(&l_inactive)) { | |
1004 | page = lru_to_page(&l_inactive); | |
1005 | prefetchw_prev_lru_page(page, &l_inactive, flags); | |
1006 | if (TestSetPageLRU(page)) | |
1007 | BUG(); | |
1008 | if (!TestClearPageActive(page)) | |
1009 | BUG(); | |
1010 | list_move(&page->lru, &zone->inactive_list); | |
1011 | pgmoved++; | |
1012 | if (!pagevec_add(&pvec, page)) { | |
1013 | zone->nr_inactive += pgmoved; | |
1014 | spin_unlock_irq(&zone->lru_lock); | |
1015 | pgdeactivate += pgmoved; | |
1016 | pgmoved = 0; | |
1017 | if (buffer_heads_over_limit) | |
1018 | pagevec_strip(&pvec); | |
1019 | __pagevec_release(&pvec); | |
1020 | spin_lock_irq(&zone->lru_lock); | |
1021 | } | |
1022 | } | |
1023 | zone->nr_inactive += pgmoved; | |
1024 | pgdeactivate += pgmoved; | |
1025 | if (buffer_heads_over_limit) { | |
1026 | spin_unlock_irq(&zone->lru_lock); | |
1027 | pagevec_strip(&pvec); | |
1028 | spin_lock_irq(&zone->lru_lock); | |
1029 | } | |
1030 | ||
1031 | pgmoved = 0; | |
1032 | while (!list_empty(&l_active)) { | |
1033 | page = lru_to_page(&l_active); | |
1034 | prefetchw_prev_lru_page(page, &l_active, flags); | |
1035 | if (TestSetPageLRU(page)) | |
1036 | BUG(); | |
1037 | BUG_ON(!PageActive(page)); | |
1038 | list_move(&page->lru, &zone->active_list); | |
1039 | pgmoved++; | |
1040 | if (!pagevec_add(&pvec, page)) { | |
1041 | zone->nr_active += pgmoved; | |
1042 | pgmoved = 0; | |
1043 | spin_unlock_irq(&zone->lru_lock); | |
1044 | __pagevec_release(&pvec); | |
1045 | spin_lock_irq(&zone->lru_lock); | |
1046 | } | |
1047 | } | |
1048 | zone->nr_active += pgmoved; | |
a74609fa NP |
1049 | spin_unlock(&zone->lru_lock); |
1050 | ||
1051 | __mod_page_state_zone(zone, pgrefill, pgscanned); | |
1052 | __mod_page_state(pgdeactivate, pgdeactivate); | |
1053 | local_irq_enable(); | |
1da177e4 | 1054 | |
a74609fa | 1055 | pagevec_release(&pvec); |
1da177e4 LT |
1056 | } |
1057 | ||
1058 | /* | |
1059 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
1060 | */ | |
1061 | static void | |
1062 | shrink_zone(struct zone *zone, struct scan_control *sc) | |
1063 | { | |
1064 | unsigned long nr_active; | |
1065 | unsigned long nr_inactive; | |
1066 | ||
53e9a615 MH |
1067 | atomic_inc(&zone->reclaim_in_progress); |
1068 | ||
1da177e4 LT |
1069 | /* |
1070 | * Add one to `nr_to_scan' just to make sure that the kernel will | |
1071 | * slowly sift through the active list. | |
1072 | */ | |
1073 | zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1; | |
1074 | nr_active = zone->nr_scan_active; | |
1075 | if (nr_active >= sc->swap_cluster_max) | |
1076 | zone->nr_scan_active = 0; | |
1077 | else | |
1078 | nr_active = 0; | |
1079 | ||
1080 | zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1; | |
1081 | nr_inactive = zone->nr_scan_inactive; | |
1082 | if (nr_inactive >= sc->swap_cluster_max) | |
1083 | zone->nr_scan_inactive = 0; | |
1084 | else | |
1085 | nr_inactive = 0; | |
1086 | ||
1da177e4 LT |
1087 | while (nr_active || nr_inactive) { |
1088 | if (nr_active) { | |
1089 | sc->nr_to_scan = min(nr_active, | |
1090 | (unsigned long)sc->swap_cluster_max); | |
1091 | nr_active -= sc->nr_to_scan; | |
1092 | refill_inactive_zone(zone, sc); | |
1093 | } | |
1094 | ||
1095 | if (nr_inactive) { | |
1096 | sc->nr_to_scan = min(nr_inactive, | |
1097 | (unsigned long)sc->swap_cluster_max); | |
1098 | nr_inactive -= sc->nr_to_scan; | |
1099 | shrink_cache(zone, sc); | |
1da177e4 LT |
1100 | } |
1101 | } | |
1102 | ||
1103 | throttle_vm_writeout(); | |
53e9a615 MH |
1104 | |
1105 | atomic_dec(&zone->reclaim_in_progress); | |
1da177e4 LT |
1106 | } |
1107 | ||
1108 | /* | |
1109 | * This is the direct reclaim path, for page-allocating processes. We only | |
1110 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
1111 | * request. | |
1112 | * | |
1113 | * We reclaim from a zone even if that zone is over pages_high. Because: | |
1114 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order | |
1115 | * allocation or | |
1116 | * b) The zones may be over pages_high but they must go *over* pages_high to | |
1117 | * satisfy the `incremental min' zone defense algorithm. | |
1118 | * | |
1119 | * Returns the number of reclaimed pages. | |
1120 | * | |
1121 | * If a zone is deemed to be full of pinned pages then just give it a light | |
1122 | * scan then give up on it. | |
1123 | */ | |
1124 | static void | |
1125 | shrink_caches(struct zone **zones, struct scan_control *sc) | |
1126 | { | |
1127 | int i; | |
1128 | ||
1129 | for (i = 0; zones[i] != NULL; i++) { | |
1130 | struct zone *zone = zones[i]; | |
1131 | ||
f3fe6512 | 1132 | if (!populated_zone(zone)) |
1da177e4 LT |
1133 | continue; |
1134 | ||
9bf2229f | 1135 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1136 | continue; |
1137 | ||
1138 | zone->temp_priority = sc->priority; | |
1139 | if (zone->prev_priority > sc->priority) | |
1140 | zone->prev_priority = sc->priority; | |
1141 | ||
1142 | if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY) | |
1143 | continue; /* Let kswapd poll it */ | |
1144 | ||
1145 | shrink_zone(zone, sc); | |
1146 | } | |
1147 | } | |
1148 | ||
1149 | /* | |
1150 | * This is the main entry point to direct page reclaim. | |
1151 | * | |
1152 | * If a full scan of the inactive list fails to free enough memory then we | |
1153 | * are "out of memory" and something needs to be killed. | |
1154 | * | |
1155 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
1156 | * high - the zone may be full of dirty or under-writeback pages, which this | |
1157 | * caller can't do much about. We kick pdflush and take explicit naps in the | |
1158 | * hope that some of these pages can be written. But if the allocating task | |
1159 | * holds filesystem locks which prevent writeout this might not work, and the | |
1160 | * allocation attempt will fail. | |
1161 | */ | |
6daa0e28 | 1162 | int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) |
1da177e4 LT |
1163 | { |
1164 | int priority; | |
1165 | int ret = 0; | |
1166 | int total_scanned = 0, total_reclaimed = 0; | |
1167 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1168 | struct scan_control sc; | |
1169 | unsigned long lru_pages = 0; | |
1170 | int i; | |
1171 | ||
1172 | sc.gfp_mask = gfp_mask; | |
52a8363e | 1173 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1174 | sc.may_swap = 1; |
1da177e4 LT |
1175 | |
1176 | inc_page_state(allocstall); | |
1177 | ||
1178 | for (i = 0; zones[i] != NULL; i++) { | |
1179 | struct zone *zone = zones[i]; | |
1180 | ||
9bf2229f | 1181 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1182 | continue; |
1183 | ||
1184 | zone->temp_priority = DEF_PRIORITY; | |
1185 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1186 | } | |
1187 | ||
1188 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1189 | sc.nr_mapped = read_page_state(nr_mapped); | |
1190 | sc.nr_scanned = 0; | |
1191 | sc.nr_reclaimed = 0; | |
1192 | sc.priority = priority; | |
1193 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
f7b7fd8f RR |
1194 | if (!priority) |
1195 | disable_swap_token(); | |
1da177e4 LT |
1196 | shrink_caches(zones, &sc); |
1197 | shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); | |
1198 | if (reclaim_state) { | |
1199 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; | |
1200 | reclaim_state->reclaimed_slab = 0; | |
1201 | } | |
1202 | total_scanned += sc.nr_scanned; | |
1203 | total_reclaimed += sc.nr_reclaimed; | |
1204 | if (total_reclaimed >= sc.swap_cluster_max) { | |
1205 | ret = 1; | |
1206 | goto out; | |
1207 | } | |
1208 | ||
1209 | /* | |
1210 | * Try to write back as many pages as we just scanned. This | |
1211 | * tends to cause slow streaming writers to write data to the | |
1212 | * disk smoothly, at the dirtying rate, which is nice. But | |
1213 | * that's undesirable in laptop mode, where we *want* lumpy | |
1214 | * writeout. So in laptop mode, write out the whole world. | |
1215 | */ | |
1216 | if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) { | |
687a21ce | 1217 | wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
1da177e4 LT |
1218 | sc.may_writepage = 1; |
1219 | } | |
1220 | ||
1221 | /* Take a nap, wait for some writeback to complete */ | |
1222 | if (sc.nr_scanned && priority < DEF_PRIORITY - 2) | |
1223 | blk_congestion_wait(WRITE, HZ/10); | |
1224 | } | |
1225 | out: | |
1226 | for (i = 0; zones[i] != 0; i++) { | |
1227 | struct zone *zone = zones[i]; | |
1228 | ||
9bf2229f | 1229 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1230 | continue; |
1231 | ||
1232 | zone->prev_priority = zone->temp_priority; | |
1233 | } | |
1234 | return ret; | |
1235 | } | |
1236 | ||
1237 | /* | |
1238 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
1239 | * they are all at pages_high. | |
1240 | * | |
1241 | * If `nr_pages' is non-zero then it is the number of pages which are to be | |
1242 | * reclaimed, regardless of the zone occupancies. This is a software suspend | |
1243 | * special. | |
1244 | * | |
1245 | * Returns the number of pages which were actually freed. | |
1246 | * | |
1247 | * There is special handling here for zones which are full of pinned pages. | |
1248 | * This can happen if the pages are all mlocked, or if they are all used by | |
1249 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
1250 | * What we do is to detect the case where all pages in the zone have been | |
1251 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
1252 | * dead and from now on, only perform a short scan. Basically we're polling | |
1253 | * the zone for when the problem goes away. | |
1254 | * | |
1255 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
1256 | * zones which have free_pages > pages_high, but once a zone is found to have | |
1257 | * free_pages <= pages_high, we scan that zone and the lower zones regardless | |
1258 | * of the number of free pages in the lower zones. This interoperates with | |
1259 | * the page allocator fallback scheme to ensure that aging of pages is balanced | |
1260 | * across the zones. | |
1261 | */ | |
1262 | static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) | |
1263 | { | |
1264 | int to_free = nr_pages; | |
1265 | int all_zones_ok; | |
1266 | int priority; | |
1267 | int i; | |
1268 | int total_scanned, total_reclaimed; | |
1269 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1270 | struct scan_control sc; | |
1271 | ||
1272 | loop_again: | |
1273 | total_scanned = 0; | |
1274 | total_reclaimed = 0; | |
1275 | sc.gfp_mask = GFP_KERNEL; | |
52a8363e | 1276 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1277 | sc.may_swap = 1; |
1da177e4 LT |
1278 | sc.nr_mapped = read_page_state(nr_mapped); |
1279 | ||
1280 | inc_page_state(pageoutrun); | |
1281 | ||
1282 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1283 | struct zone *zone = pgdat->node_zones + i; | |
1284 | ||
1285 | zone->temp_priority = DEF_PRIORITY; | |
1286 | } | |
1287 | ||
1288 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1289 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ | |
1290 | unsigned long lru_pages = 0; | |
1291 | ||
f7b7fd8f RR |
1292 | /* The swap token gets in the way of swapout... */ |
1293 | if (!priority) | |
1294 | disable_swap_token(); | |
1295 | ||
1da177e4 LT |
1296 | all_zones_ok = 1; |
1297 | ||
1298 | if (nr_pages == 0) { | |
1299 | /* | |
1300 | * Scan in the highmem->dma direction for the highest | |
1301 | * zone which needs scanning | |
1302 | */ | |
1303 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
1304 | struct zone *zone = pgdat->node_zones + i; | |
1305 | ||
f3fe6512 | 1306 | if (!populated_zone(zone)) |
1da177e4 LT |
1307 | continue; |
1308 | ||
1309 | if (zone->all_unreclaimable && | |
1310 | priority != DEF_PRIORITY) | |
1311 | continue; | |
1312 | ||
1313 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1314 | zone->pages_high, 0, 0)) { |
1da177e4 LT |
1315 | end_zone = i; |
1316 | goto scan; | |
1317 | } | |
1318 | } | |
1319 | goto out; | |
1320 | } else { | |
1321 | end_zone = pgdat->nr_zones - 1; | |
1322 | } | |
1323 | scan: | |
1324 | for (i = 0; i <= end_zone; i++) { | |
1325 | struct zone *zone = pgdat->node_zones + i; | |
1326 | ||
1327 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1328 | } | |
1329 | ||
1330 | /* | |
1331 | * Now scan the zone in the dma->highmem direction, stopping | |
1332 | * at the last zone which needs scanning. | |
1333 | * | |
1334 | * We do this because the page allocator works in the opposite | |
1335 | * direction. This prevents the page allocator from allocating | |
1336 | * pages behind kswapd's direction of progress, which would | |
1337 | * cause too much scanning of the lower zones. | |
1338 | */ | |
1339 | for (i = 0; i <= end_zone; i++) { | |
1340 | struct zone *zone = pgdat->node_zones + i; | |
b15e0905 | 1341 | int nr_slab; |
1da177e4 | 1342 | |
f3fe6512 | 1343 | if (!populated_zone(zone)) |
1da177e4 LT |
1344 | continue; |
1345 | ||
1346 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) | |
1347 | continue; | |
1348 | ||
1349 | if (nr_pages == 0) { /* Not software suspend */ | |
1350 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1351 | zone->pages_high, end_zone, 0)) |
1da177e4 LT |
1352 | all_zones_ok = 0; |
1353 | } | |
1354 | zone->temp_priority = priority; | |
1355 | if (zone->prev_priority > priority) | |
1356 | zone->prev_priority = priority; | |
1357 | sc.nr_scanned = 0; | |
1358 | sc.nr_reclaimed = 0; | |
1359 | sc.priority = priority; | |
1360 | sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; | |
1e7e5a90 | 1361 | atomic_inc(&zone->reclaim_in_progress); |
1da177e4 | 1362 | shrink_zone(zone, &sc); |
1e7e5a90 | 1363 | atomic_dec(&zone->reclaim_in_progress); |
1da177e4 | 1364 | reclaim_state->reclaimed_slab = 0; |
b15e0905 | 1365 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
1366 | lru_pages); | |
1da177e4 LT |
1367 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
1368 | total_reclaimed += sc.nr_reclaimed; | |
1369 | total_scanned += sc.nr_scanned; | |
1370 | if (zone->all_unreclaimable) | |
1371 | continue; | |
b15e0905 | 1372 | if (nr_slab == 0 && zone->pages_scanned >= |
1373 | (zone->nr_active + zone->nr_inactive) * 4) | |
1da177e4 LT |
1374 | zone->all_unreclaimable = 1; |
1375 | /* | |
1376 | * If we've done a decent amount of scanning and | |
1377 | * the reclaim ratio is low, start doing writepage | |
1378 | * even in laptop mode | |
1379 | */ | |
1380 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && | |
1381 | total_scanned > total_reclaimed+total_reclaimed/2) | |
1382 | sc.may_writepage = 1; | |
1383 | } | |
1384 | if (nr_pages && to_free > total_reclaimed) | |
1385 | continue; /* swsusp: need to do more work */ | |
1386 | if (all_zones_ok) | |
1387 | break; /* kswapd: all done */ | |
1388 | /* | |
1389 | * OK, kswapd is getting into trouble. Take a nap, then take | |
1390 | * another pass across the zones. | |
1391 | */ | |
1392 | if (total_scanned && priority < DEF_PRIORITY - 2) | |
1393 | blk_congestion_wait(WRITE, HZ/10); | |
1394 | ||
1395 | /* | |
1396 | * We do this so kswapd doesn't build up large priorities for | |
1397 | * example when it is freeing in parallel with allocators. It | |
1398 | * matches the direct reclaim path behaviour in terms of impact | |
1399 | * on zone->*_priority. | |
1400 | */ | |
1401 | if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) | |
1402 | break; | |
1403 | } | |
1404 | out: | |
1405 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1406 | struct zone *zone = pgdat->node_zones + i; | |
1407 | ||
1408 | zone->prev_priority = zone->temp_priority; | |
1409 | } | |
1410 | if (!all_zones_ok) { | |
1411 | cond_resched(); | |
1412 | goto loop_again; | |
1413 | } | |
1414 | ||
1415 | return total_reclaimed; | |
1416 | } | |
1417 | ||
1418 | /* | |
1419 | * The background pageout daemon, started as a kernel thread | |
1420 | * from the init process. | |
1421 | * | |
1422 | * This basically trickles out pages so that we have _some_ | |
1423 | * free memory available even if there is no other activity | |
1424 | * that frees anything up. This is needed for things like routing | |
1425 | * etc, where we otherwise might have all activity going on in | |
1426 | * asynchronous contexts that cannot page things out. | |
1427 | * | |
1428 | * If there are applications that are active memory-allocators | |
1429 | * (most normal use), this basically shouldn't matter. | |
1430 | */ | |
1431 | static int kswapd(void *p) | |
1432 | { | |
1433 | unsigned long order; | |
1434 | pg_data_t *pgdat = (pg_data_t*)p; | |
1435 | struct task_struct *tsk = current; | |
1436 | DEFINE_WAIT(wait); | |
1437 | struct reclaim_state reclaim_state = { | |
1438 | .reclaimed_slab = 0, | |
1439 | }; | |
1440 | cpumask_t cpumask; | |
1441 | ||
1442 | daemonize("kswapd%d", pgdat->node_id); | |
1443 | cpumask = node_to_cpumask(pgdat->node_id); | |
1444 | if (!cpus_empty(cpumask)) | |
1445 | set_cpus_allowed(tsk, cpumask); | |
1446 | current->reclaim_state = &reclaim_state; | |
1447 | ||
1448 | /* | |
1449 | * Tell the memory management that we're a "memory allocator", | |
1450 | * and that if we need more memory we should get access to it | |
1451 | * regardless (see "__alloc_pages()"). "kswapd" should | |
1452 | * never get caught in the normal page freeing logic. | |
1453 | * | |
1454 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
1455 | * you need a small amount of memory in order to be able to | |
1456 | * page out something else, and this flag essentially protects | |
1457 | * us from recursively trying to free more memory as we're | |
1458 | * trying to free the first piece of memory in the first place). | |
1459 | */ | |
930d9152 | 1460 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
1da177e4 LT |
1461 | |
1462 | order = 0; | |
1463 | for ( ; ; ) { | |
1464 | unsigned long new_order; | |
3e1d1d28 CL |
1465 | |
1466 | try_to_freeze(); | |
1da177e4 LT |
1467 | |
1468 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
1469 | new_order = pgdat->kswapd_max_order; | |
1470 | pgdat->kswapd_max_order = 0; | |
1471 | if (order < new_order) { | |
1472 | /* | |
1473 | * Don't sleep if someone wants a larger 'order' | |
1474 | * allocation | |
1475 | */ | |
1476 | order = new_order; | |
1477 | } else { | |
1478 | schedule(); | |
1479 | order = pgdat->kswapd_max_order; | |
1480 | } | |
1481 | finish_wait(&pgdat->kswapd_wait, &wait); | |
1482 | ||
1483 | balance_pgdat(pgdat, 0, order); | |
1484 | } | |
1485 | return 0; | |
1486 | } | |
1487 | ||
1488 | /* | |
1489 | * A zone is low on free memory, so wake its kswapd task to service it. | |
1490 | */ | |
1491 | void wakeup_kswapd(struct zone *zone, int order) | |
1492 | { | |
1493 | pg_data_t *pgdat; | |
1494 | ||
f3fe6512 | 1495 | if (!populated_zone(zone)) |
1da177e4 LT |
1496 | return; |
1497 | ||
1498 | pgdat = zone->zone_pgdat; | |
7fb1d9fc | 1499 | if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) |
1da177e4 LT |
1500 | return; |
1501 | if (pgdat->kswapd_max_order < order) | |
1502 | pgdat->kswapd_max_order = order; | |
9bf2229f | 1503 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 | 1504 | return; |
8d0986e2 | 1505 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
1da177e4 | 1506 | return; |
8d0986e2 | 1507 | wake_up_interruptible(&pgdat->kswapd_wait); |
1da177e4 LT |
1508 | } |
1509 | ||
1510 | #ifdef CONFIG_PM | |
1511 | /* | |
1512 | * Try to free `nr_pages' of memory, system-wide. Returns the number of freed | |
1513 | * pages. | |
1514 | */ | |
1515 | int shrink_all_memory(int nr_pages) | |
1516 | { | |
1517 | pg_data_t *pgdat; | |
1518 | int nr_to_free = nr_pages; | |
1519 | int ret = 0; | |
1520 | struct reclaim_state reclaim_state = { | |
1521 | .reclaimed_slab = 0, | |
1522 | }; | |
1523 | ||
1524 | current->reclaim_state = &reclaim_state; | |
1525 | for_each_pgdat(pgdat) { | |
1526 | int freed; | |
1527 | freed = balance_pgdat(pgdat, nr_to_free, 0); | |
1528 | ret += freed; | |
1529 | nr_to_free -= freed; | |
1530 | if (nr_to_free <= 0) | |
1531 | break; | |
1532 | } | |
1533 | current->reclaim_state = NULL; | |
1534 | return ret; | |
1535 | } | |
1536 | #endif | |
1537 | ||
1538 | #ifdef CONFIG_HOTPLUG_CPU | |
1539 | /* It's optimal to keep kswapds on the same CPUs as their memory, but | |
1540 | not required for correctness. So if the last cpu in a node goes | |
1541 | away, we get changed to run anywhere: as the first one comes back, | |
1542 | restore their cpu bindings. */ | |
1543 | static int __devinit cpu_callback(struct notifier_block *nfb, | |
1544 | unsigned long action, | |
1545 | void *hcpu) | |
1546 | { | |
1547 | pg_data_t *pgdat; | |
1548 | cpumask_t mask; | |
1549 | ||
1550 | if (action == CPU_ONLINE) { | |
1551 | for_each_pgdat(pgdat) { | |
1552 | mask = node_to_cpumask(pgdat->node_id); | |
1553 | if (any_online_cpu(mask) != NR_CPUS) | |
1554 | /* One of our CPUs online: restore mask */ | |
1555 | set_cpus_allowed(pgdat->kswapd, mask); | |
1556 | } | |
1557 | } | |
1558 | return NOTIFY_OK; | |
1559 | } | |
1560 | #endif /* CONFIG_HOTPLUG_CPU */ | |
1561 | ||
1562 | static int __init kswapd_init(void) | |
1563 | { | |
1564 | pg_data_t *pgdat; | |
1565 | swap_setup(); | |
1566 | for_each_pgdat(pgdat) | |
1567 | pgdat->kswapd | |
1568 | = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); | |
1569 | total_memory = nr_free_pagecache_pages(); | |
1570 | hotcpu_notifier(cpu_callback, 0); | |
1571 | return 0; | |
1572 | } | |
1573 | ||
1574 | module_init(kswapd_init) | |
9eeff239 CL |
1575 | |
1576 | #ifdef CONFIG_NUMA | |
1577 | /* | |
1578 | * Zone reclaim mode | |
1579 | * | |
1580 | * If non-zero call zone_reclaim when the number of free pages falls below | |
1581 | * the watermarks. | |
1582 | * | |
1583 | * In the future we may add flags to the mode. However, the page allocator | |
1584 | * should only have to check that zone_reclaim_mode != 0 before calling | |
1585 | * zone_reclaim(). | |
1586 | */ | |
1587 | int zone_reclaim_mode __read_mostly; | |
1588 | ||
1589 | /* | |
1590 | * Mininum time between zone reclaim scans | |
1591 | */ | |
89288623 | 1592 | #define ZONE_RECLAIM_INTERVAL 30*HZ |
9eeff239 CL |
1593 | /* |
1594 | * Try to free up some pages from this zone through reclaim. | |
1595 | */ | |
1596 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
1597 | { | |
89288623 | 1598 | int nr_pages; |
9eeff239 CL |
1599 | struct task_struct *p = current; |
1600 | struct reclaim_state reclaim_state; | |
89288623 | 1601 | struct scan_control sc; |
42c722d4 CL |
1602 | cpumask_t mask; |
1603 | int node_id; | |
89288623 CL |
1604 | |
1605 | if (time_before(jiffies, | |
1606 | zone->last_unsuccessful_zone_reclaim + ZONE_RECLAIM_INTERVAL)) | |
1607 | return 0; | |
9eeff239 CL |
1608 | |
1609 | if (!(gfp_mask & __GFP_WAIT) || | |
9eeff239 CL |
1610 | zone->all_unreclaimable || |
1611 | atomic_read(&zone->reclaim_in_progress) > 0) | |
1612 | return 0; | |
1613 | ||
42c722d4 CL |
1614 | node_id = zone->zone_pgdat->node_id; |
1615 | mask = node_to_cpumask(node_id); | |
1616 | if (!cpus_empty(mask) && node_id != numa_node_id()) | |
1617 | return 0; | |
1618 | ||
89288623 CL |
1619 | sc.may_writepage = 0; |
1620 | sc.may_swap = 0; | |
1621 | sc.nr_scanned = 0; | |
1622 | sc.nr_reclaimed = 0; | |
1623 | sc.priority = 0; | |
1624 | sc.nr_mapped = read_page_state(nr_mapped); | |
1625 | sc.gfp_mask = gfp_mask; | |
9eeff239 CL |
1626 | |
1627 | disable_swap_token(); | |
1628 | ||
89288623 | 1629 | nr_pages = 1 << order; |
9eeff239 CL |
1630 | if (nr_pages > SWAP_CLUSTER_MAX) |
1631 | sc.swap_cluster_max = nr_pages; | |
1632 | else | |
1633 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
1634 | ||
1635 | cond_resched(); | |
1636 | p->flags |= PF_MEMALLOC; | |
1637 | reclaim_state.reclaimed_slab = 0; | |
1638 | p->reclaim_state = &reclaim_state; | |
1639 | shrink_zone(zone, &sc); | |
1640 | p->reclaim_state = NULL; | |
1641 | current->flags &= ~PF_MEMALLOC; | |
1642 | ||
1643 | if (sc.nr_reclaimed == 0) | |
1644 | zone->last_unsuccessful_zone_reclaim = jiffies; | |
1645 | ||
1646 | return sc.nr_reclaimed > nr_pages; | |
1647 | } | |
1648 | #endif | |
1649 |