Commit | Line | Data |
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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 | ||
74 | /* This context's SWAP_CLUSTER_MAX. If freeing memory for | |
75 | * suspend, we effectively ignore SWAP_CLUSTER_MAX. | |
76 | * In this context, it doesn't matter that we scan the | |
77 | * whole list at once. */ | |
78 | int swap_cluster_max; | |
79 | }; | |
80 | ||
81 | /* | |
82 | * The list of shrinker callbacks used by to apply pressure to | |
83 | * ageable caches. | |
84 | */ | |
85 | struct shrinker { | |
86 | shrinker_t shrinker; | |
87 | struct list_head list; | |
88 | int seeks; /* seeks to recreate an obj */ | |
89 | long nr; /* objs pending delete */ | |
90 | }; | |
91 | ||
92 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
93 | ||
94 | #ifdef ARCH_HAS_PREFETCH | |
95 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
96 | do { \ | |
97 | if ((_page)->lru.prev != _base) { \ | |
98 | struct page *prev; \ | |
99 | \ | |
100 | prev = lru_to_page(&(_page->lru)); \ | |
101 | prefetch(&prev->_field); \ | |
102 | } \ | |
103 | } while (0) | |
104 | #else | |
105 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
106 | #endif | |
107 | ||
108 | #ifdef ARCH_HAS_PREFETCHW | |
109 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
110 | do { \ | |
111 | if ((_page)->lru.prev != _base) { \ | |
112 | struct page *prev; \ | |
113 | \ | |
114 | prev = lru_to_page(&(_page->lru)); \ | |
115 | prefetchw(&prev->_field); \ | |
116 | } \ | |
117 | } while (0) | |
118 | #else | |
119 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
120 | #endif | |
121 | ||
122 | /* | |
123 | * From 0 .. 100. Higher means more swappy. | |
124 | */ | |
125 | int vm_swappiness = 60; | |
126 | static long total_memory; | |
127 | ||
128 | static LIST_HEAD(shrinker_list); | |
129 | static DECLARE_RWSEM(shrinker_rwsem); | |
130 | ||
131 | /* | |
132 | * Add a shrinker callback to be called from the vm | |
133 | */ | |
134 | struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) | |
135 | { | |
136 | struct shrinker *shrinker; | |
137 | ||
138 | shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); | |
139 | if (shrinker) { | |
140 | shrinker->shrinker = theshrinker; | |
141 | shrinker->seeks = seeks; | |
142 | shrinker->nr = 0; | |
143 | down_write(&shrinker_rwsem); | |
144 | list_add_tail(&shrinker->list, &shrinker_list); | |
145 | up_write(&shrinker_rwsem); | |
146 | } | |
147 | return shrinker; | |
148 | } | |
149 | EXPORT_SYMBOL(set_shrinker); | |
150 | ||
151 | /* | |
152 | * Remove one | |
153 | */ | |
154 | void remove_shrinker(struct shrinker *shrinker) | |
155 | { | |
156 | down_write(&shrinker_rwsem); | |
157 | list_del(&shrinker->list); | |
158 | up_write(&shrinker_rwsem); | |
159 | kfree(shrinker); | |
160 | } | |
161 | EXPORT_SYMBOL(remove_shrinker); | |
162 | ||
163 | #define SHRINK_BATCH 128 | |
164 | /* | |
165 | * Call the shrink functions to age shrinkable caches | |
166 | * | |
167 | * Here we assume it costs one seek to replace a lru page and that it also | |
168 | * takes a seek to recreate a cache object. With this in mind we age equal | |
169 | * percentages of the lru and ageable caches. This should balance the seeks | |
170 | * generated by these structures. | |
171 | * | |
172 | * If the vm encounted mapped pages on the LRU it increase the pressure on | |
173 | * slab to avoid swapping. | |
174 | * | |
175 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
176 | * | |
177 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
178 | * are eligible for the caller's allocation attempt. It is used for balancing | |
179 | * slab reclaim versus page reclaim. | |
b15e0905 | 180 | * |
181 | * Returns the number of slab objects which we shrunk. | |
1da177e4 | 182 | */ |
9d0243bc | 183 | int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages) |
1da177e4 LT |
184 | { |
185 | struct shrinker *shrinker; | |
b15e0905 | 186 | int ret = 0; |
1da177e4 LT |
187 | |
188 | if (scanned == 0) | |
189 | scanned = SWAP_CLUSTER_MAX; | |
190 | ||
191 | if (!down_read_trylock(&shrinker_rwsem)) | |
b15e0905 | 192 | return 1; /* Assume we'll be able to shrink next time */ |
1da177e4 LT |
193 | |
194 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
195 | unsigned long long delta; | |
196 | unsigned long total_scan; | |
ea164d73 | 197 | unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
198 | |
199 | delta = (4 * scanned) / shrinker->seeks; | |
ea164d73 | 200 | delta *= max_pass; |
1da177e4 LT |
201 | do_div(delta, lru_pages + 1); |
202 | shrinker->nr += delta; | |
ea164d73 AA |
203 | if (shrinker->nr < 0) { |
204 | printk(KERN_ERR "%s: nr=%ld\n", | |
205 | __FUNCTION__, shrinker->nr); | |
206 | shrinker->nr = max_pass; | |
207 | } | |
208 | ||
209 | /* | |
210 | * Avoid risking looping forever due to too large nr value: | |
211 | * never try to free more than twice the estimate number of | |
212 | * freeable entries. | |
213 | */ | |
214 | if (shrinker->nr > max_pass * 2) | |
215 | shrinker->nr = max_pass * 2; | |
1da177e4 LT |
216 | |
217 | total_scan = shrinker->nr; | |
218 | shrinker->nr = 0; | |
219 | ||
220 | while (total_scan >= SHRINK_BATCH) { | |
221 | long this_scan = SHRINK_BATCH; | |
222 | int shrink_ret; | |
b15e0905 | 223 | int nr_before; |
1da177e4 | 224 | |
b15e0905 | 225 | nr_before = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
226 | shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); |
227 | if (shrink_ret == -1) | |
228 | break; | |
b15e0905 | 229 | if (shrink_ret < nr_before) |
230 | ret += nr_before - shrink_ret; | |
1da177e4 LT |
231 | mod_page_state(slabs_scanned, this_scan); |
232 | total_scan -= this_scan; | |
233 | ||
234 | cond_resched(); | |
235 | } | |
236 | ||
237 | shrinker->nr += total_scan; | |
238 | } | |
239 | up_read(&shrinker_rwsem); | |
b15e0905 | 240 | return ret; |
1da177e4 LT |
241 | } |
242 | ||
243 | /* Called without lock on whether page is mapped, so answer is unstable */ | |
244 | static inline int page_mapping_inuse(struct page *page) | |
245 | { | |
246 | struct address_space *mapping; | |
247 | ||
248 | /* Page is in somebody's page tables. */ | |
249 | if (page_mapped(page)) | |
250 | return 1; | |
251 | ||
252 | /* Be more reluctant to reclaim swapcache than pagecache */ | |
253 | if (PageSwapCache(page)) | |
254 | return 1; | |
255 | ||
256 | mapping = page_mapping(page); | |
257 | if (!mapping) | |
258 | return 0; | |
259 | ||
260 | /* File is mmap'd by somebody? */ | |
261 | return mapping_mapped(mapping); | |
262 | } | |
263 | ||
264 | static inline int is_page_cache_freeable(struct page *page) | |
265 | { | |
266 | return page_count(page) - !!PagePrivate(page) == 2; | |
267 | } | |
268 | ||
269 | static int may_write_to_queue(struct backing_dev_info *bdi) | |
270 | { | |
271 | if (current_is_kswapd()) | |
272 | return 1; | |
273 | if (current_is_pdflush()) /* This is unlikely, but why not... */ | |
274 | return 1; | |
275 | if (!bdi_write_congested(bdi)) | |
276 | return 1; | |
277 | if (bdi == current->backing_dev_info) | |
278 | return 1; | |
279 | return 0; | |
280 | } | |
281 | ||
282 | /* | |
283 | * We detected a synchronous write error writing a page out. Probably | |
284 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
285 | * fsync(), msync() or close(). | |
286 | * | |
287 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
288 | * prevents it from being freed up. But we have a ref on the page and once | |
289 | * that page is locked, the mapping is pinned. | |
290 | * | |
291 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
292 | * __GFP_FS. | |
293 | */ | |
294 | static void handle_write_error(struct address_space *mapping, | |
295 | struct page *page, int error) | |
296 | { | |
297 | lock_page(page); | |
298 | if (page_mapping(page) == mapping) { | |
299 | if (error == -ENOSPC) | |
300 | set_bit(AS_ENOSPC, &mapping->flags); | |
301 | else | |
302 | set_bit(AS_EIO, &mapping->flags); | |
303 | } | |
304 | unlock_page(page); | |
305 | } | |
306 | ||
307 | /* | |
308 | * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). | |
309 | */ | |
310 | static pageout_t pageout(struct page *page, struct address_space *mapping) | |
311 | { | |
312 | /* | |
313 | * If the page is dirty, only perform writeback if that write | |
314 | * will be non-blocking. To prevent this allocation from being | |
315 | * stalled by pagecache activity. But note that there may be | |
316 | * stalls if we need to run get_block(). We could test | |
317 | * PagePrivate for that. | |
318 | * | |
319 | * If this process is currently in generic_file_write() against | |
320 | * this page's queue, we can perform writeback even if that | |
321 | * will block. | |
322 | * | |
323 | * If the page is swapcache, write it back even if that would | |
324 | * block, for some throttling. This happens by accident, because | |
325 | * swap_backing_dev_info is bust: it doesn't reflect the | |
326 | * congestion state of the swapdevs. Easy to fix, if needed. | |
327 | * See swapfile.c:page_queue_congested(). | |
328 | */ | |
329 | if (!is_page_cache_freeable(page)) | |
330 | return PAGE_KEEP; | |
331 | if (!mapping) { | |
332 | /* | |
333 | * Some data journaling orphaned pages can have | |
334 | * page->mapping == NULL while being dirty with clean buffers. | |
335 | */ | |
323aca6c | 336 | if (PagePrivate(page)) { |
1da177e4 LT |
337 | if (try_to_free_buffers(page)) { |
338 | ClearPageDirty(page); | |
339 | printk("%s: orphaned page\n", __FUNCTION__); | |
340 | return PAGE_CLEAN; | |
341 | } | |
342 | } | |
343 | return PAGE_KEEP; | |
344 | } | |
345 | if (mapping->a_ops->writepage == NULL) | |
346 | return PAGE_ACTIVATE; | |
347 | if (!may_write_to_queue(mapping->backing_dev_info)) | |
348 | return PAGE_KEEP; | |
349 | ||
350 | if (clear_page_dirty_for_io(page)) { | |
351 | int res; | |
352 | struct writeback_control wbc = { | |
353 | .sync_mode = WB_SYNC_NONE, | |
354 | .nr_to_write = SWAP_CLUSTER_MAX, | |
355 | .nonblocking = 1, | |
356 | .for_reclaim = 1, | |
357 | }; | |
358 | ||
359 | SetPageReclaim(page); | |
360 | res = mapping->a_ops->writepage(page, &wbc); | |
361 | if (res < 0) | |
362 | handle_write_error(mapping, page, res); | |
994fc28c | 363 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
1da177e4 LT |
364 | ClearPageReclaim(page); |
365 | return PAGE_ACTIVATE; | |
366 | } | |
367 | if (!PageWriteback(page)) { | |
368 | /* synchronous write or broken a_ops? */ | |
369 | ClearPageReclaim(page); | |
370 | } | |
371 | ||
372 | return PAGE_SUCCESS; | |
373 | } | |
374 | ||
375 | return PAGE_CLEAN; | |
376 | } | |
377 | ||
378 | /* | |
379 | * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed | |
380 | */ | |
381 | static int shrink_list(struct list_head *page_list, struct scan_control *sc) | |
382 | { | |
383 | LIST_HEAD(ret_pages); | |
384 | struct pagevec freed_pvec; | |
385 | int pgactivate = 0; | |
386 | int reclaimed = 0; | |
387 | ||
388 | cond_resched(); | |
389 | ||
390 | pagevec_init(&freed_pvec, 1); | |
391 | while (!list_empty(page_list)) { | |
392 | struct address_space *mapping; | |
393 | struct page *page; | |
394 | int may_enter_fs; | |
395 | int referenced; | |
396 | ||
397 | cond_resched(); | |
398 | ||
399 | page = lru_to_page(page_list); | |
400 | list_del(&page->lru); | |
401 | ||
402 | if (TestSetPageLocked(page)) | |
403 | goto keep; | |
404 | ||
405 | BUG_ON(PageActive(page)); | |
406 | ||
407 | sc->nr_scanned++; | |
408 | /* Double the slab pressure for mapped and swapcache pages */ | |
409 | if (page_mapped(page) || PageSwapCache(page)) | |
410 | sc->nr_scanned++; | |
411 | ||
412 | if (PageWriteback(page)) | |
413 | goto keep_locked; | |
414 | ||
f7b7fd8f | 415 | referenced = page_referenced(page, 1); |
1da177e4 LT |
416 | /* In active use or really unfreeable? Activate it. */ |
417 | if (referenced && page_mapping_inuse(page)) | |
418 | goto activate_locked; | |
419 | ||
420 | #ifdef CONFIG_SWAP | |
421 | /* | |
422 | * Anonymous process memory has backing store? | |
423 | * Try to allocate it some swap space here. | |
424 | */ | |
c340010e | 425 | if (PageAnon(page) && !PageSwapCache(page)) { |
1da177e4 LT |
426 | if (!add_to_swap(page)) |
427 | goto activate_locked; | |
428 | } | |
429 | #endif /* CONFIG_SWAP */ | |
430 | ||
431 | mapping = page_mapping(page); | |
432 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || | |
433 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
434 | ||
435 | /* | |
436 | * The page is mapped into the page tables of one or more | |
437 | * processes. Try to unmap it here. | |
438 | */ | |
439 | if (page_mapped(page) && mapping) { | |
440 | switch (try_to_unmap(page)) { | |
441 | case SWAP_FAIL: | |
442 | goto activate_locked; | |
443 | case SWAP_AGAIN: | |
444 | goto keep_locked; | |
445 | case SWAP_SUCCESS: | |
446 | ; /* try to free the page below */ | |
447 | } | |
448 | } | |
449 | ||
450 | if (PageDirty(page)) { | |
451 | if (referenced) | |
452 | goto keep_locked; | |
453 | if (!may_enter_fs) | |
454 | goto keep_locked; | |
455 | if (laptop_mode && !sc->may_writepage) | |
456 | goto keep_locked; | |
457 | ||
458 | /* Page is dirty, try to write it out here */ | |
459 | switch(pageout(page, mapping)) { | |
460 | case PAGE_KEEP: | |
461 | goto keep_locked; | |
462 | case PAGE_ACTIVATE: | |
463 | goto activate_locked; | |
464 | case PAGE_SUCCESS: | |
465 | if (PageWriteback(page) || PageDirty(page)) | |
466 | goto keep; | |
467 | /* | |
468 | * A synchronous write - probably a ramdisk. Go | |
469 | * ahead and try to reclaim the page. | |
470 | */ | |
471 | if (TestSetPageLocked(page)) | |
472 | goto keep; | |
473 | if (PageDirty(page) || PageWriteback(page)) | |
474 | goto keep_locked; | |
475 | mapping = page_mapping(page); | |
476 | case PAGE_CLEAN: | |
477 | ; /* try to free the page below */ | |
478 | } | |
479 | } | |
480 | ||
481 | /* | |
482 | * If the page has buffers, try to free the buffer mappings | |
483 | * associated with this page. If we succeed we try to free | |
484 | * the page as well. | |
485 | * | |
486 | * We do this even if the page is PageDirty(). | |
487 | * try_to_release_page() does not perform I/O, but it is | |
488 | * possible for a page to have PageDirty set, but it is actually | |
489 | * clean (all its buffers are clean). This happens if the | |
490 | * buffers were written out directly, with submit_bh(). ext3 | |
491 | * will do this, as well as the blockdev mapping. | |
492 | * try_to_release_page() will discover that cleanness and will | |
493 | * drop the buffers and mark the page clean - it can be freed. | |
494 | * | |
495 | * Rarely, pages can have buffers and no ->mapping. These are | |
496 | * the pages which were not successfully invalidated in | |
497 | * truncate_complete_page(). We try to drop those buffers here | |
498 | * and if that worked, and the page is no longer mapped into | |
499 | * process address space (page_count == 1) it can be freed. | |
500 | * Otherwise, leave the page on the LRU so it is swappable. | |
501 | */ | |
502 | if (PagePrivate(page)) { | |
503 | if (!try_to_release_page(page, sc->gfp_mask)) | |
504 | goto activate_locked; | |
505 | if (!mapping && page_count(page) == 1) | |
506 | goto free_it; | |
507 | } | |
508 | ||
509 | if (!mapping) | |
510 | goto keep_locked; /* truncate got there first */ | |
511 | ||
512 | write_lock_irq(&mapping->tree_lock); | |
513 | ||
514 | /* | |
515 | * The non-racy check for busy page. It is critical to check | |
516 | * PageDirty _after_ making sure that the page is freeable and | |
517 | * not in use by anybody. (pagecache + us == 2) | |
518 | */ | |
3d80636a LT |
519 | if (unlikely(page_count(page) != 2)) |
520 | goto cannot_free; | |
521 | smp_rmb(); | |
522 | if (unlikely(PageDirty(page))) | |
523 | goto cannot_free; | |
1da177e4 LT |
524 | |
525 | #ifdef CONFIG_SWAP | |
526 | if (PageSwapCache(page)) { | |
4c21e2f2 | 527 | swp_entry_t swap = { .val = page_private(page) }; |
1da177e4 LT |
528 | __delete_from_swap_cache(page); |
529 | write_unlock_irq(&mapping->tree_lock); | |
530 | swap_free(swap); | |
531 | __put_page(page); /* The pagecache ref */ | |
532 | goto free_it; | |
533 | } | |
534 | #endif /* CONFIG_SWAP */ | |
535 | ||
536 | __remove_from_page_cache(page); | |
537 | write_unlock_irq(&mapping->tree_lock); | |
538 | __put_page(page); | |
539 | ||
540 | free_it: | |
541 | unlock_page(page); | |
542 | reclaimed++; | |
543 | if (!pagevec_add(&freed_pvec, page)) | |
544 | __pagevec_release_nonlru(&freed_pvec); | |
545 | continue; | |
546 | ||
3d80636a LT |
547 | cannot_free: |
548 | write_unlock_irq(&mapping->tree_lock); | |
549 | goto keep_locked; | |
550 | ||
1da177e4 LT |
551 | activate_locked: |
552 | SetPageActive(page); | |
553 | pgactivate++; | |
554 | keep_locked: | |
555 | unlock_page(page); | |
556 | keep: | |
557 | list_add(&page->lru, &ret_pages); | |
558 | BUG_ON(PageLRU(page)); | |
559 | } | |
560 | list_splice(&ret_pages, page_list); | |
561 | if (pagevec_count(&freed_pvec)) | |
562 | __pagevec_release_nonlru(&freed_pvec); | |
563 | mod_page_state(pgactivate, pgactivate); | |
564 | sc->nr_reclaimed += reclaimed; | |
565 | return reclaimed; | |
566 | } | |
567 | ||
568 | /* | |
569 | * zone->lru_lock is heavily contended. Some of the functions that | |
570 | * shrink the lists perform better by taking out a batch of pages | |
571 | * and working on them outside the LRU lock. | |
572 | * | |
573 | * For pagecache intensive workloads, this function is the hottest | |
574 | * spot in the kernel (apart from copy_*_user functions). | |
575 | * | |
576 | * Appropriate locks must be held before calling this function. | |
577 | * | |
578 | * @nr_to_scan: The number of pages to look through on the list. | |
579 | * @src: The LRU list to pull pages off. | |
580 | * @dst: The temp list to put pages on to. | |
581 | * @scanned: The number of pages that were scanned. | |
582 | * | |
583 | * returns how many pages were moved onto *@dst. | |
584 | */ | |
585 | static int isolate_lru_pages(int nr_to_scan, struct list_head *src, | |
586 | struct list_head *dst, int *scanned) | |
587 | { | |
588 | int nr_taken = 0; | |
589 | struct page *page; | |
590 | int scan = 0; | |
591 | ||
592 | while (scan++ < nr_to_scan && !list_empty(src)) { | |
593 | page = lru_to_page(src); | |
594 | prefetchw_prev_lru_page(page, src, flags); | |
595 | ||
21eac81f CL |
596 | switch (__isolate_lru_page(page)) { |
597 | case 1: | |
598 | /* Succeeded to isolate page */ | |
599 | list_move(&page->lru, dst); | |
1da177e4 | 600 | nr_taken++; |
21eac81f CL |
601 | break; |
602 | case -ENOENT: | |
603 | /* Not possible to isolate */ | |
604 | list_move(&page->lru, src); | |
605 | break; | |
606 | default: | |
607 | BUG(); | |
1da177e4 LT |
608 | } |
609 | } | |
610 | ||
611 | *scanned = scan; | |
612 | return nr_taken; | |
613 | } | |
614 | ||
21eac81f CL |
615 | static void lru_add_drain_per_cpu(void *dummy) |
616 | { | |
617 | lru_add_drain(); | |
618 | } | |
619 | ||
620 | /* | |
621 | * Isolate one page from the LRU lists and put it on the | |
622 | * indicated list. Do necessary cache draining if the | |
623 | * page is not on the LRU lists yet. | |
624 | * | |
625 | * Result: | |
626 | * 0 = page not on LRU list | |
627 | * 1 = page removed from LRU list and added to the specified list. | |
628 | * -ENOENT = page is being freed elsewhere. | |
629 | */ | |
630 | int isolate_lru_page(struct page *page) | |
631 | { | |
632 | int rc = 0; | |
633 | struct zone *zone = page_zone(page); | |
634 | ||
635 | redo: | |
636 | spin_lock_irq(&zone->lru_lock); | |
637 | rc = __isolate_lru_page(page); | |
638 | if (rc == 1) { | |
639 | if (PageActive(page)) | |
640 | del_page_from_active_list(zone, page); | |
641 | else | |
642 | del_page_from_inactive_list(zone, page); | |
643 | } | |
644 | spin_unlock_irq(&zone->lru_lock); | |
645 | if (rc == 0) { | |
646 | /* | |
647 | * Maybe this page is still waiting for a cpu to drain it | |
648 | * from one of the lru lists? | |
649 | */ | |
650 | rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL); | |
651 | if (rc == 0 && PageLRU(page)) | |
652 | goto redo; | |
653 | } | |
654 | return rc; | |
655 | } | |
656 | ||
1da177e4 LT |
657 | /* |
658 | * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed | |
659 | */ | |
660 | static void shrink_cache(struct zone *zone, struct scan_control *sc) | |
661 | { | |
662 | LIST_HEAD(page_list); | |
663 | struct pagevec pvec; | |
664 | int max_scan = sc->nr_to_scan; | |
665 | ||
666 | pagevec_init(&pvec, 1); | |
667 | ||
668 | lru_add_drain(); | |
669 | spin_lock_irq(&zone->lru_lock); | |
670 | while (max_scan > 0) { | |
671 | struct page *page; | |
672 | int nr_taken; | |
673 | int nr_scan; | |
674 | int nr_freed; | |
675 | ||
676 | nr_taken = isolate_lru_pages(sc->swap_cluster_max, | |
677 | &zone->inactive_list, | |
678 | &page_list, &nr_scan); | |
679 | zone->nr_inactive -= nr_taken; | |
680 | zone->pages_scanned += nr_scan; | |
681 | spin_unlock_irq(&zone->lru_lock); | |
682 | ||
683 | if (nr_taken == 0) | |
684 | goto done; | |
685 | ||
686 | max_scan -= nr_scan; | |
1da177e4 | 687 | nr_freed = shrink_list(&page_list, sc); |
1da177e4 | 688 | |
a74609fa NP |
689 | local_irq_disable(); |
690 | if (current_is_kswapd()) { | |
691 | __mod_page_state_zone(zone, pgscan_kswapd, nr_scan); | |
692 | __mod_page_state(kswapd_steal, nr_freed); | |
693 | } else | |
694 | __mod_page_state_zone(zone, pgscan_direct, nr_scan); | |
695 | __mod_page_state_zone(zone, pgsteal, nr_freed); | |
696 | ||
697 | spin_lock(&zone->lru_lock); | |
1da177e4 LT |
698 | /* |
699 | * Put back any unfreeable pages. | |
700 | */ | |
701 | while (!list_empty(&page_list)) { | |
702 | page = lru_to_page(&page_list); | |
703 | if (TestSetPageLRU(page)) | |
704 | BUG(); | |
705 | list_del(&page->lru); | |
706 | if (PageActive(page)) | |
707 | add_page_to_active_list(zone, page); | |
708 | else | |
709 | add_page_to_inactive_list(zone, page); | |
710 | if (!pagevec_add(&pvec, page)) { | |
711 | spin_unlock_irq(&zone->lru_lock); | |
712 | __pagevec_release(&pvec); | |
713 | spin_lock_irq(&zone->lru_lock); | |
714 | } | |
715 | } | |
716 | } | |
717 | spin_unlock_irq(&zone->lru_lock); | |
718 | done: | |
719 | pagevec_release(&pvec); | |
720 | } | |
721 | ||
21eac81f CL |
722 | static inline void move_to_lru(struct page *page) |
723 | { | |
724 | list_del(&page->lru); | |
725 | if (PageActive(page)) { | |
726 | /* | |
727 | * lru_cache_add_active checks that | |
728 | * the PG_active bit is off. | |
729 | */ | |
730 | ClearPageActive(page); | |
731 | lru_cache_add_active(page); | |
732 | } else { | |
733 | lru_cache_add(page); | |
734 | } | |
735 | put_page(page); | |
736 | } | |
737 | ||
738 | /* | |
739 | * Add isolated pages on the list back to the LRU | |
740 | * | |
741 | * returns the number of pages put back. | |
742 | */ | |
743 | int putback_lru_pages(struct list_head *l) | |
744 | { | |
745 | struct page *page; | |
746 | struct page *page2; | |
747 | int count = 0; | |
748 | ||
749 | list_for_each_entry_safe(page, page2, l, lru) { | |
750 | move_to_lru(page); | |
751 | count++; | |
752 | } | |
753 | return count; | |
754 | } | |
755 | ||
1da177e4 LT |
756 | /* |
757 | * This moves pages from the active list to the inactive list. | |
758 | * | |
759 | * We move them the other way if the page is referenced by one or more | |
760 | * processes, from rmap. | |
761 | * | |
762 | * If the pages are mostly unmapped, the processing is fast and it is | |
763 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
764 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
765 | * should drop zone->lru_lock around each page. It's impossible to balance | |
766 | * this, so instead we remove the pages from the LRU while processing them. | |
767 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
768 | * nobody will play with that bit on a non-LRU page. | |
769 | * | |
770 | * The downside is that we have to touch page->_count against each page. | |
771 | * But we had to alter page->flags anyway. | |
772 | */ | |
773 | static void | |
774 | refill_inactive_zone(struct zone *zone, struct scan_control *sc) | |
775 | { | |
776 | int pgmoved; | |
777 | int pgdeactivate = 0; | |
778 | int pgscanned; | |
779 | int nr_pages = sc->nr_to_scan; | |
780 | LIST_HEAD(l_hold); /* The pages which were snipped off */ | |
781 | LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ | |
782 | LIST_HEAD(l_active); /* Pages to go onto the active_list */ | |
783 | struct page *page; | |
784 | struct pagevec pvec; | |
785 | int reclaim_mapped = 0; | |
786 | long mapped_ratio; | |
787 | long distress; | |
788 | long swap_tendency; | |
789 | ||
790 | lru_add_drain(); | |
791 | spin_lock_irq(&zone->lru_lock); | |
792 | pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, | |
793 | &l_hold, &pgscanned); | |
794 | zone->pages_scanned += pgscanned; | |
795 | zone->nr_active -= pgmoved; | |
796 | spin_unlock_irq(&zone->lru_lock); | |
797 | ||
798 | /* | |
799 | * `distress' is a measure of how much trouble we're having reclaiming | |
800 | * pages. 0 -> no problems. 100 -> great trouble. | |
801 | */ | |
802 | distress = 100 >> zone->prev_priority; | |
803 | ||
804 | /* | |
805 | * The point of this algorithm is to decide when to start reclaiming | |
806 | * mapped memory instead of just pagecache. Work out how much memory | |
807 | * is mapped. | |
808 | */ | |
809 | mapped_ratio = (sc->nr_mapped * 100) / total_memory; | |
810 | ||
811 | /* | |
812 | * Now decide how much we really want to unmap some pages. The mapped | |
813 | * ratio is downgraded - just because there's a lot of mapped memory | |
814 | * doesn't necessarily mean that page reclaim isn't succeeding. | |
815 | * | |
816 | * The distress ratio is important - we don't want to start going oom. | |
817 | * | |
818 | * A 100% value of vm_swappiness overrides this algorithm altogether. | |
819 | */ | |
820 | swap_tendency = mapped_ratio / 2 + distress + vm_swappiness; | |
821 | ||
822 | /* | |
823 | * Now use this metric to decide whether to start moving mapped memory | |
824 | * onto the inactive list. | |
825 | */ | |
826 | if (swap_tendency >= 100) | |
827 | reclaim_mapped = 1; | |
828 | ||
829 | while (!list_empty(&l_hold)) { | |
830 | cond_resched(); | |
831 | page = lru_to_page(&l_hold); | |
832 | list_del(&page->lru); | |
833 | if (page_mapped(page)) { | |
834 | if (!reclaim_mapped || | |
835 | (total_swap_pages == 0 && PageAnon(page)) || | |
f7b7fd8f | 836 | page_referenced(page, 0)) { |
1da177e4 LT |
837 | list_add(&page->lru, &l_active); |
838 | continue; | |
839 | } | |
840 | } | |
841 | list_add(&page->lru, &l_inactive); | |
842 | } | |
843 | ||
844 | pagevec_init(&pvec, 1); | |
845 | pgmoved = 0; | |
846 | spin_lock_irq(&zone->lru_lock); | |
847 | while (!list_empty(&l_inactive)) { | |
848 | page = lru_to_page(&l_inactive); | |
849 | prefetchw_prev_lru_page(page, &l_inactive, flags); | |
850 | if (TestSetPageLRU(page)) | |
851 | BUG(); | |
852 | if (!TestClearPageActive(page)) | |
853 | BUG(); | |
854 | list_move(&page->lru, &zone->inactive_list); | |
855 | pgmoved++; | |
856 | if (!pagevec_add(&pvec, page)) { | |
857 | zone->nr_inactive += pgmoved; | |
858 | spin_unlock_irq(&zone->lru_lock); | |
859 | pgdeactivate += pgmoved; | |
860 | pgmoved = 0; | |
861 | if (buffer_heads_over_limit) | |
862 | pagevec_strip(&pvec); | |
863 | __pagevec_release(&pvec); | |
864 | spin_lock_irq(&zone->lru_lock); | |
865 | } | |
866 | } | |
867 | zone->nr_inactive += pgmoved; | |
868 | pgdeactivate += pgmoved; | |
869 | if (buffer_heads_over_limit) { | |
870 | spin_unlock_irq(&zone->lru_lock); | |
871 | pagevec_strip(&pvec); | |
872 | spin_lock_irq(&zone->lru_lock); | |
873 | } | |
874 | ||
875 | pgmoved = 0; | |
876 | while (!list_empty(&l_active)) { | |
877 | page = lru_to_page(&l_active); | |
878 | prefetchw_prev_lru_page(page, &l_active, flags); | |
879 | if (TestSetPageLRU(page)) | |
880 | BUG(); | |
881 | BUG_ON(!PageActive(page)); | |
882 | list_move(&page->lru, &zone->active_list); | |
883 | pgmoved++; | |
884 | if (!pagevec_add(&pvec, page)) { | |
885 | zone->nr_active += pgmoved; | |
886 | pgmoved = 0; | |
887 | spin_unlock_irq(&zone->lru_lock); | |
888 | __pagevec_release(&pvec); | |
889 | spin_lock_irq(&zone->lru_lock); | |
890 | } | |
891 | } | |
892 | zone->nr_active += pgmoved; | |
a74609fa NP |
893 | spin_unlock(&zone->lru_lock); |
894 | ||
895 | __mod_page_state_zone(zone, pgrefill, pgscanned); | |
896 | __mod_page_state(pgdeactivate, pgdeactivate); | |
897 | local_irq_enable(); | |
1da177e4 | 898 | |
a74609fa | 899 | pagevec_release(&pvec); |
1da177e4 LT |
900 | } |
901 | ||
902 | /* | |
903 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
904 | */ | |
905 | static void | |
906 | shrink_zone(struct zone *zone, struct scan_control *sc) | |
907 | { | |
908 | unsigned long nr_active; | |
909 | unsigned long nr_inactive; | |
910 | ||
53e9a615 MH |
911 | atomic_inc(&zone->reclaim_in_progress); |
912 | ||
1da177e4 LT |
913 | /* |
914 | * Add one to `nr_to_scan' just to make sure that the kernel will | |
915 | * slowly sift through the active list. | |
916 | */ | |
917 | zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1; | |
918 | nr_active = zone->nr_scan_active; | |
919 | if (nr_active >= sc->swap_cluster_max) | |
920 | zone->nr_scan_active = 0; | |
921 | else | |
922 | nr_active = 0; | |
923 | ||
924 | zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1; | |
925 | nr_inactive = zone->nr_scan_inactive; | |
926 | if (nr_inactive >= sc->swap_cluster_max) | |
927 | zone->nr_scan_inactive = 0; | |
928 | else | |
929 | nr_inactive = 0; | |
930 | ||
1da177e4 LT |
931 | while (nr_active || nr_inactive) { |
932 | if (nr_active) { | |
933 | sc->nr_to_scan = min(nr_active, | |
934 | (unsigned long)sc->swap_cluster_max); | |
935 | nr_active -= sc->nr_to_scan; | |
936 | refill_inactive_zone(zone, sc); | |
937 | } | |
938 | ||
939 | if (nr_inactive) { | |
940 | sc->nr_to_scan = min(nr_inactive, | |
941 | (unsigned long)sc->swap_cluster_max); | |
942 | nr_inactive -= sc->nr_to_scan; | |
943 | shrink_cache(zone, sc); | |
1da177e4 LT |
944 | } |
945 | } | |
946 | ||
947 | throttle_vm_writeout(); | |
53e9a615 MH |
948 | |
949 | atomic_dec(&zone->reclaim_in_progress); | |
1da177e4 LT |
950 | } |
951 | ||
952 | /* | |
953 | * This is the direct reclaim path, for page-allocating processes. We only | |
954 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
955 | * request. | |
956 | * | |
957 | * We reclaim from a zone even if that zone is over pages_high. Because: | |
958 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order | |
959 | * allocation or | |
960 | * b) The zones may be over pages_high but they must go *over* pages_high to | |
961 | * satisfy the `incremental min' zone defense algorithm. | |
962 | * | |
963 | * Returns the number of reclaimed pages. | |
964 | * | |
965 | * If a zone is deemed to be full of pinned pages then just give it a light | |
966 | * scan then give up on it. | |
967 | */ | |
968 | static void | |
969 | shrink_caches(struct zone **zones, struct scan_control *sc) | |
970 | { | |
971 | int i; | |
972 | ||
973 | for (i = 0; zones[i] != NULL; i++) { | |
974 | struct zone *zone = zones[i]; | |
975 | ||
f3fe6512 | 976 | if (!populated_zone(zone)) |
1da177e4 LT |
977 | continue; |
978 | ||
9bf2229f | 979 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
980 | continue; |
981 | ||
982 | zone->temp_priority = sc->priority; | |
983 | if (zone->prev_priority > sc->priority) | |
984 | zone->prev_priority = sc->priority; | |
985 | ||
986 | if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY) | |
987 | continue; /* Let kswapd poll it */ | |
988 | ||
989 | shrink_zone(zone, sc); | |
990 | } | |
991 | } | |
992 | ||
993 | /* | |
994 | * This is the main entry point to direct page reclaim. | |
995 | * | |
996 | * If a full scan of the inactive list fails to free enough memory then we | |
997 | * are "out of memory" and something needs to be killed. | |
998 | * | |
999 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
1000 | * high - the zone may be full of dirty or under-writeback pages, which this | |
1001 | * caller can't do much about. We kick pdflush and take explicit naps in the | |
1002 | * hope that some of these pages can be written. But if the allocating task | |
1003 | * holds filesystem locks which prevent writeout this might not work, and the | |
1004 | * allocation attempt will fail. | |
1005 | */ | |
6daa0e28 | 1006 | int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) |
1da177e4 LT |
1007 | { |
1008 | int priority; | |
1009 | int ret = 0; | |
1010 | int total_scanned = 0, total_reclaimed = 0; | |
1011 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1012 | struct scan_control sc; | |
1013 | unsigned long lru_pages = 0; | |
1014 | int i; | |
1015 | ||
1016 | sc.gfp_mask = gfp_mask; | |
1017 | sc.may_writepage = 0; | |
1018 | ||
1019 | inc_page_state(allocstall); | |
1020 | ||
1021 | for (i = 0; zones[i] != NULL; i++) { | |
1022 | struct zone *zone = zones[i]; | |
1023 | ||
9bf2229f | 1024 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1025 | continue; |
1026 | ||
1027 | zone->temp_priority = DEF_PRIORITY; | |
1028 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1029 | } | |
1030 | ||
1031 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1032 | sc.nr_mapped = read_page_state(nr_mapped); | |
1033 | sc.nr_scanned = 0; | |
1034 | sc.nr_reclaimed = 0; | |
1035 | sc.priority = priority; | |
1036 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
f7b7fd8f RR |
1037 | if (!priority) |
1038 | disable_swap_token(); | |
1da177e4 LT |
1039 | shrink_caches(zones, &sc); |
1040 | shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); | |
1041 | if (reclaim_state) { | |
1042 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; | |
1043 | reclaim_state->reclaimed_slab = 0; | |
1044 | } | |
1045 | total_scanned += sc.nr_scanned; | |
1046 | total_reclaimed += sc.nr_reclaimed; | |
1047 | if (total_reclaimed >= sc.swap_cluster_max) { | |
1048 | ret = 1; | |
1049 | goto out; | |
1050 | } | |
1051 | ||
1052 | /* | |
1053 | * Try to write back as many pages as we just scanned. This | |
1054 | * tends to cause slow streaming writers to write data to the | |
1055 | * disk smoothly, at the dirtying rate, which is nice. But | |
1056 | * that's undesirable in laptop mode, where we *want* lumpy | |
1057 | * writeout. So in laptop mode, write out the whole world. | |
1058 | */ | |
1059 | if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) { | |
687a21ce | 1060 | wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
1da177e4 LT |
1061 | sc.may_writepage = 1; |
1062 | } | |
1063 | ||
1064 | /* Take a nap, wait for some writeback to complete */ | |
1065 | if (sc.nr_scanned && priority < DEF_PRIORITY - 2) | |
1066 | blk_congestion_wait(WRITE, HZ/10); | |
1067 | } | |
1068 | out: | |
1069 | for (i = 0; zones[i] != 0; i++) { | |
1070 | struct zone *zone = zones[i]; | |
1071 | ||
9bf2229f | 1072 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1073 | continue; |
1074 | ||
1075 | zone->prev_priority = zone->temp_priority; | |
1076 | } | |
1077 | return ret; | |
1078 | } | |
1079 | ||
1080 | /* | |
1081 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
1082 | * they are all at pages_high. | |
1083 | * | |
1084 | * If `nr_pages' is non-zero then it is the number of pages which are to be | |
1085 | * reclaimed, regardless of the zone occupancies. This is a software suspend | |
1086 | * special. | |
1087 | * | |
1088 | * Returns the number of pages which were actually freed. | |
1089 | * | |
1090 | * There is special handling here for zones which are full of pinned pages. | |
1091 | * This can happen if the pages are all mlocked, or if they are all used by | |
1092 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
1093 | * What we do is to detect the case where all pages in the zone have been | |
1094 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
1095 | * dead and from now on, only perform a short scan. Basically we're polling | |
1096 | * the zone for when the problem goes away. | |
1097 | * | |
1098 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
1099 | * zones which have free_pages > pages_high, but once a zone is found to have | |
1100 | * free_pages <= pages_high, we scan that zone and the lower zones regardless | |
1101 | * of the number of free pages in the lower zones. This interoperates with | |
1102 | * the page allocator fallback scheme to ensure that aging of pages is balanced | |
1103 | * across the zones. | |
1104 | */ | |
1105 | static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) | |
1106 | { | |
1107 | int to_free = nr_pages; | |
1108 | int all_zones_ok; | |
1109 | int priority; | |
1110 | int i; | |
1111 | int total_scanned, total_reclaimed; | |
1112 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1113 | struct scan_control sc; | |
1114 | ||
1115 | loop_again: | |
1116 | total_scanned = 0; | |
1117 | total_reclaimed = 0; | |
1118 | sc.gfp_mask = GFP_KERNEL; | |
1119 | sc.may_writepage = 0; | |
1120 | sc.nr_mapped = read_page_state(nr_mapped); | |
1121 | ||
1122 | inc_page_state(pageoutrun); | |
1123 | ||
1124 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1125 | struct zone *zone = pgdat->node_zones + i; | |
1126 | ||
1127 | zone->temp_priority = DEF_PRIORITY; | |
1128 | } | |
1129 | ||
1130 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1131 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ | |
1132 | unsigned long lru_pages = 0; | |
1133 | ||
f7b7fd8f RR |
1134 | /* The swap token gets in the way of swapout... */ |
1135 | if (!priority) | |
1136 | disable_swap_token(); | |
1137 | ||
1da177e4 LT |
1138 | all_zones_ok = 1; |
1139 | ||
1140 | if (nr_pages == 0) { | |
1141 | /* | |
1142 | * Scan in the highmem->dma direction for the highest | |
1143 | * zone which needs scanning | |
1144 | */ | |
1145 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
1146 | struct zone *zone = pgdat->node_zones + i; | |
1147 | ||
f3fe6512 | 1148 | if (!populated_zone(zone)) |
1da177e4 LT |
1149 | continue; |
1150 | ||
1151 | if (zone->all_unreclaimable && | |
1152 | priority != DEF_PRIORITY) | |
1153 | continue; | |
1154 | ||
1155 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1156 | zone->pages_high, 0, 0)) { |
1da177e4 LT |
1157 | end_zone = i; |
1158 | goto scan; | |
1159 | } | |
1160 | } | |
1161 | goto out; | |
1162 | } else { | |
1163 | end_zone = pgdat->nr_zones - 1; | |
1164 | } | |
1165 | scan: | |
1166 | for (i = 0; i <= end_zone; i++) { | |
1167 | struct zone *zone = pgdat->node_zones + i; | |
1168 | ||
1169 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1170 | } | |
1171 | ||
1172 | /* | |
1173 | * Now scan the zone in the dma->highmem direction, stopping | |
1174 | * at the last zone which needs scanning. | |
1175 | * | |
1176 | * We do this because the page allocator works in the opposite | |
1177 | * direction. This prevents the page allocator from allocating | |
1178 | * pages behind kswapd's direction of progress, which would | |
1179 | * cause too much scanning of the lower zones. | |
1180 | */ | |
1181 | for (i = 0; i <= end_zone; i++) { | |
1182 | struct zone *zone = pgdat->node_zones + i; | |
b15e0905 | 1183 | int nr_slab; |
1da177e4 | 1184 | |
f3fe6512 | 1185 | if (!populated_zone(zone)) |
1da177e4 LT |
1186 | continue; |
1187 | ||
1188 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) | |
1189 | continue; | |
1190 | ||
1191 | if (nr_pages == 0) { /* Not software suspend */ | |
1192 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1193 | zone->pages_high, end_zone, 0)) |
1da177e4 LT |
1194 | all_zones_ok = 0; |
1195 | } | |
1196 | zone->temp_priority = priority; | |
1197 | if (zone->prev_priority > priority) | |
1198 | zone->prev_priority = priority; | |
1199 | sc.nr_scanned = 0; | |
1200 | sc.nr_reclaimed = 0; | |
1201 | sc.priority = priority; | |
1202 | sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; | |
1e7e5a90 | 1203 | atomic_inc(&zone->reclaim_in_progress); |
1da177e4 | 1204 | shrink_zone(zone, &sc); |
1e7e5a90 | 1205 | atomic_dec(&zone->reclaim_in_progress); |
1da177e4 | 1206 | reclaim_state->reclaimed_slab = 0; |
b15e0905 | 1207 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
1208 | lru_pages); | |
1da177e4 LT |
1209 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
1210 | total_reclaimed += sc.nr_reclaimed; | |
1211 | total_scanned += sc.nr_scanned; | |
1212 | if (zone->all_unreclaimable) | |
1213 | continue; | |
b15e0905 | 1214 | if (nr_slab == 0 && zone->pages_scanned >= |
1215 | (zone->nr_active + zone->nr_inactive) * 4) | |
1da177e4 LT |
1216 | zone->all_unreclaimable = 1; |
1217 | /* | |
1218 | * If we've done a decent amount of scanning and | |
1219 | * the reclaim ratio is low, start doing writepage | |
1220 | * even in laptop mode | |
1221 | */ | |
1222 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && | |
1223 | total_scanned > total_reclaimed+total_reclaimed/2) | |
1224 | sc.may_writepage = 1; | |
1225 | } | |
1226 | if (nr_pages && to_free > total_reclaimed) | |
1227 | continue; /* swsusp: need to do more work */ | |
1228 | if (all_zones_ok) | |
1229 | break; /* kswapd: all done */ | |
1230 | /* | |
1231 | * OK, kswapd is getting into trouble. Take a nap, then take | |
1232 | * another pass across the zones. | |
1233 | */ | |
1234 | if (total_scanned && priority < DEF_PRIORITY - 2) | |
1235 | blk_congestion_wait(WRITE, HZ/10); | |
1236 | ||
1237 | /* | |
1238 | * We do this so kswapd doesn't build up large priorities for | |
1239 | * example when it is freeing in parallel with allocators. It | |
1240 | * matches the direct reclaim path behaviour in terms of impact | |
1241 | * on zone->*_priority. | |
1242 | */ | |
1243 | if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) | |
1244 | break; | |
1245 | } | |
1246 | out: | |
1247 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1248 | struct zone *zone = pgdat->node_zones + i; | |
1249 | ||
1250 | zone->prev_priority = zone->temp_priority; | |
1251 | } | |
1252 | if (!all_zones_ok) { | |
1253 | cond_resched(); | |
1254 | goto loop_again; | |
1255 | } | |
1256 | ||
1257 | return total_reclaimed; | |
1258 | } | |
1259 | ||
1260 | /* | |
1261 | * The background pageout daemon, started as a kernel thread | |
1262 | * from the init process. | |
1263 | * | |
1264 | * This basically trickles out pages so that we have _some_ | |
1265 | * free memory available even if there is no other activity | |
1266 | * that frees anything up. This is needed for things like routing | |
1267 | * etc, where we otherwise might have all activity going on in | |
1268 | * asynchronous contexts that cannot page things out. | |
1269 | * | |
1270 | * If there are applications that are active memory-allocators | |
1271 | * (most normal use), this basically shouldn't matter. | |
1272 | */ | |
1273 | static int kswapd(void *p) | |
1274 | { | |
1275 | unsigned long order; | |
1276 | pg_data_t *pgdat = (pg_data_t*)p; | |
1277 | struct task_struct *tsk = current; | |
1278 | DEFINE_WAIT(wait); | |
1279 | struct reclaim_state reclaim_state = { | |
1280 | .reclaimed_slab = 0, | |
1281 | }; | |
1282 | cpumask_t cpumask; | |
1283 | ||
1284 | daemonize("kswapd%d", pgdat->node_id); | |
1285 | cpumask = node_to_cpumask(pgdat->node_id); | |
1286 | if (!cpus_empty(cpumask)) | |
1287 | set_cpus_allowed(tsk, cpumask); | |
1288 | current->reclaim_state = &reclaim_state; | |
1289 | ||
1290 | /* | |
1291 | * Tell the memory management that we're a "memory allocator", | |
1292 | * and that if we need more memory we should get access to it | |
1293 | * regardless (see "__alloc_pages()"). "kswapd" should | |
1294 | * never get caught in the normal page freeing logic. | |
1295 | * | |
1296 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
1297 | * you need a small amount of memory in order to be able to | |
1298 | * page out something else, and this flag essentially protects | |
1299 | * us from recursively trying to free more memory as we're | |
1300 | * trying to free the first piece of memory in the first place). | |
1301 | */ | |
1302 | tsk->flags |= PF_MEMALLOC|PF_KSWAPD; | |
1303 | ||
1304 | order = 0; | |
1305 | for ( ; ; ) { | |
1306 | unsigned long new_order; | |
3e1d1d28 CL |
1307 | |
1308 | try_to_freeze(); | |
1da177e4 LT |
1309 | |
1310 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
1311 | new_order = pgdat->kswapd_max_order; | |
1312 | pgdat->kswapd_max_order = 0; | |
1313 | if (order < new_order) { | |
1314 | /* | |
1315 | * Don't sleep if someone wants a larger 'order' | |
1316 | * allocation | |
1317 | */ | |
1318 | order = new_order; | |
1319 | } else { | |
1320 | schedule(); | |
1321 | order = pgdat->kswapd_max_order; | |
1322 | } | |
1323 | finish_wait(&pgdat->kswapd_wait, &wait); | |
1324 | ||
1325 | balance_pgdat(pgdat, 0, order); | |
1326 | } | |
1327 | return 0; | |
1328 | } | |
1329 | ||
1330 | /* | |
1331 | * A zone is low on free memory, so wake its kswapd task to service it. | |
1332 | */ | |
1333 | void wakeup_kswapd(struct zone *zone, int order) | |
1334 | { | |
1335 | pg_data_t *pgdat; | |
1336 | ||
f3fe6512 | 1337 | if (!populated_zone(zone)) |
1da177e4 LT |
1338 | return; |
1339 | ||
1340 | pgdat = zone->zone_pgdat; | |
7fb1d9fc | 1341 | if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) |
1da177e4 LT |
1342 | return; |
1343 | if (pgdat->kswapd_max_order < order) | |
1344 | pgdat->kswapd_max_order = order; | |
9bf2229f | 1345 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 | 1346 | return; |
8d0986e2 | 1347 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
1da177e4 | 1348 | return; |
8d0986e2 | 1349 | wake_up_interruptible(&pgdat->kswapd_wait); |
1da177e4 LT |
1350 | } |
1351 | ||
1352 | #ifdef CONFIG_PM | |
1353 | /* | |
1354 | * Try to free `nr_pages' of memory, system-wide. Returns the number of freed | |
1355 | * pages. | |
1356 | */ | |
1357 | int shrink_all_memory(int nr_pages) | |
1358 | { | |
1359 | pg_data_t *pgdat; | |
1360 | int nr_to_free = nr_pages; | |
1361 | int ret = 0; | |
1362 | struct reclaim_state reclaim_state = { | |
1363 | .reclaimed_slab = 0, | |
1364 | }; | |
1365 | ||
1366 | current->reclaim_state = &reclaim_state; | |
1367 | for_each_pgdat(pgdat) { | |
1368 | int freed; | |
1369 | freed = balance_pgdat(pgdat, nr_to_free, 0); | |
1370 | ret += freed; | |
1371 | nr_to_free -= freed; | |
1372 | if (nr_to_free <= 0) | |
1373 | break; | |
1374 | } | |
1375 | current->reclaim_state = NULL; | |
1376 | return ret; | |
1377 | } | |
1378 | #endif | |
1379 | ||
1380 | #ifdef CONFIG_HOTPLUG_CPU | |
1381 | /* It's optimal to keep kswapds on the same CPUs as their memory, but | |
1382 | not required for correctness. So if the last cpu in a node goes | |
1383 | away, we get changed to run anywhere: as the first one comes back, | |
1384 | restore their cpu bindings. */ | |
1385 | static int __devinit cpu_callback(struct notifier_block *nfb, | |
1386 | unsigned long action, | |
1387 | void *hcpu) | |
1388 | { | |
1389 | pg_data_t *pgdat; | |
1390 | cpumask_t mask; | |
1391 | ||
1392 | if (action == CPU_ONLINE) { | |
1393 | for_each_pgdat(pgdat) { | |
1394 | mask = node_to_cpumask(pgdat->node_id); | |
1395 | if (any_online_cpu(mask) != NR_CPUS) | |
1396 | /* One of our CPUs online: restore mask */ | |
1397 | set_cpus_allowed(pgdat->kswapd, mask); | |
1398 | } | |
1399 | } | |
1400 | return NOTIFY_OK; | |
1401 | } | |
1402 | #endif /* CONFIG_HOTPLUG_CPU */ | |
1403 | ||
1404 | static int __init kswapd_init(void) | |
1405 | { | |
1406 | pg_data_t *pgdat; | |
1407 | swap_setup(); | |
1408 | for_each_pgdat(pgdat) | |
1409 | pgdat->kswapd | |
1410 | = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); | |
1411 | total_memory = nr_free_pagecache_pages(); | |
1412 | hotcpu_notifier(cpu_callback, 0); | |
1413 | return 0; | |
1414 | } | |
1415 | ||
1416 | module_init(kswapd_init) |