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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 { | |
1da177e4 LT |
55 | /* Incremented by the number of inactive pages that were scanned */ |
56 | unsigned long nr_scanned; | |
57 | ||
58 | /* Incremented by the number of pages reclaimed */ | |
59 | unsigned long nr_reclaimed; | |
60 | ||
61 | unsigned long nr_mapped; /* From page_state */ | |
62 | ||
1da177e4 | 63 | /* This context's GFP mask */ |
6daa0e28 | 64 | gfp_t gfp_mask; |
1da177e4 LT |
65 | |
66 | int may_writepage; | |
67 | ||
f1fd1067 CL |
68 | /* Can pages be swapped as part of reclaim? */ |
69 | int may_swap; | |
70 | ||
1da177e4 LT |
71 | /* This context's SWAP_CLUSTER_MAX. If freeing memory for |
72 | * suspend, we effectively ignore SWAP_CLUSTER_MAX. | |
73 | * In this context, it doesn't matter that we scan the | |
74 | * whole list at once. */ | |
75 | int swap_cluster_max; | |
76 | }; | |
77 | ||
78 | /* | |
79 | * The list of shrinker callbacks used by to apply pressure to | |
80 | * ageable caches. | |
81 | */ | |
82 | struct shrinker { | |
83 | shrinker_t shrinker; | |
84 | struct list_head list; | |
85 | int seeks; /* seeks to recreate an obj */ | |
86 | long nr; /* objs pending delete */ | |
87 | }; | |
88 | ||
89 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
90 | ||
91 | #ifdef ARCH_HAS_PREFETCH | |
92 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
93 | do { \ | |
94 | if ((_page)->lru.prev != _base) { \ | |
95 | struct page *prev; \ | |
96 | \ | |
97 | prev = lru_to_page(&(_page->lru)); \ | |
98 | prefetch(&prev->_field); \ | |
99 | } \ | |
100 | } while (0) | |
101 | #else | |
102 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
103 | #endif | |
104 | ||
105 | #ifdef ARCH_HAS_PREFETCHW | |
106 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
107 | do { \ | |
108 | if ((_page)->lru.prev != _base) { \ | |
109 | struct page *prev; \ | |
110 | \ | |
111 | prev = lru_to_page(&(_page->lru)); \ | |
112 | prefetchw(&prev->_field); \ | |
113 | } \ | |
114 | } while (0) | |
115 | #else | |
116 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
117 | #endif | |
118 | ||
119 | /* | |
120 | * From 0 .. 100. Higher means more swappy. | |
121 | */ | |
122 | int vm_swappiness = 60; | |
123 | static long total_memory; | |
124 | ||
125 | static LIST_HEAD(shrinker_list); | |
126 | static DECLARE_RWSEM(shrinker_rwsem); | |
127 | ||
128 | /* | |
129 | * Add a shrinker callback to be called from the vm | |
130 | */ | |
131 | struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) | |
132 | { | |
133 | struct shrinker *shrinker; | |
134 | ||
135 | shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); | |
136 | if (shrinker) { | |
137 | shrinker->shrinker = theshrinker; | |
138 | shrinker->seeks = seeks; | |
139 | shrinker->nr = 0; | |
140 | down_write(&shrinker_rwsem); | |
141 | list_add_tail(&shrinker->list, &shrinker_list); | |
142 | up_write(&shrinker_rwsem); | |
143 | } | |
144 | return shrinker; | |
145 | } | |
146 | EXPORT_SYMBOL(set_shrinker); | |
147 | ||
148 | /* | |
149 | * Remove one | |
150 | */ | |
151 | void remove_shrinker(struct shrinker *shrinker) | |
152 | { | |
153 | down_write(&shrinker_rwsem); | |
154 | list_del(&shrinker->list); | |
155 | up_write(&shrinker_rwsem); | |
156 | kfree(shrinker); | |
157 | } | |
158 | EXPORT_SYMBOL(remove_shrinker); | |
159 | ||
160 | #define SHRINK_BATCH 128 | |
161 | /* | |
162 | * Call the shrink functions to age shrinkable caches | |
163 | * | |
164 | * Here we assume it costs one seek to replace a lru page and that it also | |
165 | * takes a seek to recreate a cache object. With this in mind we age equal | |
166 | * percentages of the lru and ageable caches. This should balance the seeks | |
167 | * generated by these structures. | |
168 | * | |
169 | * If the vm encounted mapped pages on the LRU it increase the pressure on | |
170 | * slab to avoid swapping. | |
171 | * | |
172 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
173 | * | |
174 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
175 | * are eligible for the caller's allocation attempt. It is used for balancing | |
176 | * slab reclaim versus page reclaim. | |
b15e0905 AM |
177 | * |
178 | * Returns the number of slab objects which we shrunk. | |
1da177e4 | 179 | */ |
9d0243bc | 180 | int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages) |
1da177e4 LT |
181 | { |
182 | struct shrinker *shrinker; | |
b15e0905 | 183 | int ret = 0; |
1da177e4 LT |
184 | |
185 | if (scanned == 0) | |
186 | scanned = SWAP_CLUSTER_MAX; | |
187 | ||
188 | if (!down_read_trylock(&shrinker_rwsem)) | |
b15e0905 | 189 | return 1; /* Assume we'll be able to shrink next time */ |
1da177e4 LT |
190 | |
191 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
192 | unsigned long long delta; | |
193 | unsigned long total_scan; | |
ea164d73 | 194 | unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
195 | |
196 | delta = (4 * scanned) / shrinker->seeks; | |
ea164d73 | 197 | delta *= max_pass; |
1da177e4 LT |
198 | do_div(delta, lru_pages + 1); |
199 | shrinker->nr += delta; | |
ea164d73 AA |
200 | if (shrinker->nr < 0) { |
201 | printk(KERN_ERR "%s: nr=%ld\n", | |
202 | __FUNCTION__, shrinker->nr); | |
203 | shrinker->nr = max_pass; | |
204 | } | |
205 | ||
206 | /* | |
207 | * Avoid risking looping forever due to too large nr value: | |
208 | * never try to free more than twice the estimate number of | |
209 | * freeable entries. | |
210 | */ | |
211 | if (shrinker->nr > max_pass * 2) | |
212 | shrinker->nr = max_pass * 2; | |
1da177e4 LT |
213 | |
214 | total_scan = shrinker->nr; | |
215 | shrinker->nr = 0; | |
216 | ||
217 | while (total_scan >= SHRINK_BATCH) { | |
218 | long this_scan = SHRINK_BATCH; | |
219 | int shrink_ret; | |
b15e0905 | 220 | int nr_before; |
1da177e4 | 221 | |
b15e0905 | 222 | nr_before = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
223 | shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); |
224 | if (shrink_ret == -1) | |
225 | break; | |
b15e0905 AM |
226 | if (shrink_ret < nr_before) |
227 | ret += nr_before - shrink_ret; | |
1da177e4 LT |
228 | mod_page_state(slabs_scanned, this_scan); |
229 | total_scan -= this_scan; | |
230 | ||
231 | cond_resched(); | |
232 | } | |
233 | ||
234 | shrinker->nr += total_scan; | |
235 | } | |
236 | up_read(&shrinker_rwsem); | |
b15e0905 | 237 | return ret; |
1da177e4 LT |
238 | } |
239 | ||
240 | /* Called without lock on whether page is mapped, so answer is unstable */ | |
241 | static inline int page_mapping_inuse(struct page *page) | |
242 | { | |
243 | struct address_space *mapping; | |
244 | ||
245 | /* Page is in somebody's page tables. */ | |
246 | if (page_mapped(page)) | |
247 | return 1; | |
248 | ||
249 | /* Be more reluctant to reclaim swapcache than pagecache */ | |
250 | if (PageSwapCache(page)) | |
251 | return 1; | |
252 | ||
253 | mapping = page_mapping(page); | |
254 | if (!mapping) | |
255 | return 0; | |
256 | ||
257 | /* File is mmap'd by somebody? */ | |
258 | return mapping_mapped(mapping); | |
259 | } | |
260 | ||
261 | static inline int is_page_cache_freeable(struct page *page) | |
262 | { | |
263 | return page_count(page) - !!PagePrivate(page) == 2; | |
264 | } | |
265 | ||
266 | static int may_write_to_queue(struct backing_dev_info *bdi) | |
267 | { | |
930d9152 | 268 | if (current->flags & PF_SWAPWRITE) |
1da177e4 LT |
269 | return 1; |
270 | if (!bdi_write_congested(bdi)) | |
271 | return 1; | |
272 | if (bdi == current->backing_dev_info) | |
273 | return 1; | |
274 | return 0; | |
275 | } | |
276 | ||
277 | /* | |
278 | * We detected a synchronous write error writing a page out. Probably | |
279 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
280 | * fsync(), msync() or close(). | |
281 | * | |
282 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
283 | * prevents it from being freed up. But we have a ref on the page and once | |
284 | * that page is locked, the mapping is pinned. | |
285 | * | |
286 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
287 | * __GFP_FS. | |
288 | */ | |
289 | static void handle_write_error(struct address_space *mapping, | |
290 | struct page *page, int error) | |
291 | { | |
292 | lock_page(page); | |
293 | if (page_mapping(page) == mapping) { | |
294 | if (error == -ENOSPC) | |
295 | set_bit(AS_ENOSPC, &mapping->flags); | |
296 | else | |
297 | set_bit(AS_EIO, &mapping->flags); | |
298 | } | |
299 | unlock_page(page); | |
300 | } | |
301 | ||
302 | /* | |
303 | * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). | |
304 | */ | |
305 | static pageout_t pageout(struct page *page, struct address_space *mapping) | |
306 | { | |
307 | /* | |
308 | * If the page is dirty, only perform writeback if that write | |
309 | * will be non-blocking. To prevent this allocation from being | |
310 | * stalled by pagecache activity. But note that there may be | |
311 | * stalls if we need to run get_block(). We could test | |
312 | * PagePrivate for that. | |
313 | * | |
314 | * If this process is currently in generic_file_write() against | |
315 | * this page's queue, we can perform writeback even if that | |
316 | * will block. | |
317 | * | |
318 | * If the page is swapcache, write it back even if that would | |
319 | * block, for some throttling. This happens by accident, because | |
320 | * swap_backing_dev_info is bust: it doesn't reflect the | |
321 | * congestion state of the swapdevs. Easy to fix, if needed. | |
322 | * See swapfile.c:page_queue_congested(). | |
323 | */ | |
324 | if (!is_page_cache_freeable(page)) | |
325 | return PAGE_KEEP; | |
326 | if (!mapping) { | |
327 | /* | |
328 | * Some data journaling orphaned pages can have | |
329 | * page->mapping == NULL while being dirty with clean buffers. | |
330 | */ | |
323aca6c | 331 | if (PagePrivate(page)) { |
1da177e4 LT |
332 | if (try_to_free_buffers(page)) { |
333 | ClearPageDirty(page); | |
334 | printk("%s: orphaned page\n", __FUNCTION__); | |
335 | return PAGE_CLEAN; | |
336 | } | |
337 | } | |
338 | return PAGE_KEEP; | |
339 | } | |
340 | if (mapping->a_ops->writepage == NULL) | |
341 | return PAGE_ACTIVATE; | |
342 | if (!may_write_to_queue(mapping->backing_dev_info)) | |
343 | return PAGE_KEEP; | |
344 | ||
345 | if (clear_page_dirty_for_io(page)) { | |
346 | int res; | |
347 | struct writeback_control wbc = { | |
348 | .sync_mode = WB_SYNC_NONE, | |
349 | .nr_to_write = SWAP_CLUSTER_MAX, | |
350 | .nonblocking = 1, | |
351 | .for_reclaim = 1, | |
352 | }; | |
353 | ||
354 | SetPageReclaim(page); | |
355 | res = mapping->a_ops->writepage(page, &wbc); | |
356 | if (res < 0) | |
357 | handle_write_error(mapping, page, res); | |
994fc28c | 358 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
1da177e4 LT |
359 | ClearPageReclaim(page); |
360 | return PAGE_ACTIVATE; | |
361 | } | |
362 | if (!PageWriteback(page)) { | |
363 | /* synchronous write or broken a_ops? */ | |
364 | ClearPageReclaim(page); | |
365 | } | |
366 | ||
367 | return PAGE_SUCCESS; | |
368 | } | |
369 | ||
370 | return PAGE_CLEAN; | |
371 | } | |
372 | ||
49d2e9cc CL |
373 | static int remove_mapping(struct address_space *mapping, struct page *page) |
374 | { | |
375 | if (!mapping) | |
376 | return 0; /* truncate got there first */ | |
377 | ||
378 | write_lock_irq(&mapping->tree_lock); | |
379 | ||
380 | /* | |
381 | * The non-racy check for busy page. It is critical to check | |
382 | * PageDirty _after_ making sure that the page is freeable and | |
383 | * not in use by anybody. (pagecache + us == 2) | |
384 | */ | |
385 | if (unlikely(page_count(page) != 2)) | |
386 | goto cannot_free; | |
387 | smp_rmb(); | |
388 | if (unlikely(PageDirty(page))) | |
389 | goto cannot_free; | |
390 | ||
391 | if (PageSwapCache(page)) { | |
392 | swp_entry_t swap = { .val = page_private(page) }; | |
393 | __delete_from_swap_cache(page); | |
394 | write_unlock_irq(&mapping->tree_lock); | |
395 | swap_free(swap); | |
396 | __put_page(page); /* The pagecache ref */ | |
397 | return 1; | |
398 | } | |
399 | ||
400 | __remove_from_page_cache(page); | |
401 | write_unlock_irq(&mapping->tree_lock); | |
402 | __put_page(page); | |
403 | return 1; | |
404 | ||
405 | cannot_free: | |
406 | write_unlock_irq(&mapping->tree_lock); | |
407 | return 0; | |
408 | } | |
409 | ||
1da177e4 LT |
410 | /* |
411 | * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed | |
412 | */ | |
413 | static int shrink_list(struct list_head *page_list, struct scan_control *sc) | |
414 | { | |
415 | LIST_HEAD(ret_pages); | |
416 | struct pagevec freed_pvec; | |
417 | int pgactivate = 0; | |
418 | int reclaimed = 0; | |
419 | ||
420 | cond_resched(); | |
421 | ||
422 | pagevec_init(&freed_pvec, 1); | |
423 | while (!list_empty(page_list)) { | |
424 | struct address_space *mapping; | |
425 | struct page *page; | |
426 | int may_enter_fs; | |
427 | int referenced; | |
428 | ||
429 | cond_resched(); | |
430 | ||
431 | page = lru_to_page(page_list); | |
432 | list_del(&page->lru); | |
433 | ||
434 | if (TestSetPageLocked(page)) | |
435 | goto keep; | |
436 | ||
437 | BUG_ON(PageActive(page)); | |
438 | ||
439 | sc->nr_scanned++; | |
80e43426 CL |
440 | |
441 | if (!sc->may_swap && page_mapped(page)) | |
442 | goto keep_locked; | |
443 | ||
1da177e4 LT |
444 | /* Double the slab pressure for mapped and swapcache pages */ |
445 | if (page_mapped(page) || PageSwapCache(page)) | |
446 | sc->nr_scanned++; | |
447 | ||
448 | if (PageWriteback(page)) | |
449 | goto keep_locked; | |
450 | ||
f7b7fd8f | 451 | referenced = page_referenced(page, 1); |
1da177e4 LT |
452 | /* In active use or really unfreeable? Activate it. */ |
453 | if (referenced && page_mapping_inuse(page)) | |
454 | goto activate_locked; | |
455 | ||
456 | #ifdef CONFIG_SWAP | |
457 | /* | |
458 | * Anonymous process memory has backing store? | |
459 | * Try to allocate it some swap space here. | |
460 | */ | |
c340010e | 461 | if (PageAnon(page) && !PageSwapCache(page)) { |
f1fd1067 CL |
462 | if (!sc->may_swap) |
463 | goto keep_locked; | |
1480a540 | 464 | if (!add_to_swap(page, GFP_ATOMIC)) |
1da177e4 LT |
465 | goto activate_locked; |
466 | } | |
467 | #endif /* CONFIG_SWAP */ | |
468 | ||
469 | mapping = page_mapping(page); | |
470 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || | |
471 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
472 | ||
473 | /* | |
474 | * The page is mapped into the page tables of one or more | |
475 | * processes. Try to unmap it here. | |
476 | */ | |
477 | if (page_mapped(page) && mapping) { | |
aa3f18b3 CL |
478 | /* |
479 | * No unmapping if we do not swap | |
480 | */ | |
481 | if (!sc->may_swap) | |
482 | goto keep_locked; | |
483 | ||
a48d07af | 484 | switch (try_to_unmap(page, 0)) { |
1da177e4 LT |
485 | case SWAP_FAIL: |
486 | goto activate_locked; | |
487 | case SWAP_AGAIN: | |
488 | goto keep_locked; | |
489 | case SWAP_SUCCESS: | |
490 | ; /* try to free the page below */ | |
491 | } | |
492 | } | |
493 | ||
494 | if (PageDirty(page)) { | |
495 | if (referenced) | |
496 | goto keep_locked; | |
497 | if (!may_enter_fs) | |
498 | goto keep_locked; | |
52a8363e | 499 | if (!sc->may_writepage) |
1da177e4 LT |
500 | goto keep_locked; |
501 | ||
502 | /* Page is dirty, try to write it out here */ | |
503 | switch(pageout(page, mapping)) { | |
504 | case PAGE_KEEP: | |
505 | goto keep_locked; | |
506 | case PAGE_ACTIVATE: | |
507 | goto activate_locked; | |
508 | case PAGE_SUCCESS: | |
509 | if (PageWriteback(page) || PageDirty(page)) | |
510 | goto keep; | |
511 | /* | |
512 | * A synchronous write - probably a ramdisk. Go | |
513 | * ahead and try to reclaim the page. | |
514 | */ | |
515 | if (TestSetPageLocked(page)) | |
516 | goto keep; | |
517 | if (PageDirty(page) || PageWriteback(page)) | |
518 | goto keep_locked; | |
519 | mapping = page_mapping(page); | |
520 | case PAGE_CLEAN: | |
521 | ; /* try to free the page below */ | |
522 | } | |
523 | } | |
524 | ||
525 | /* | |
526 | * If the page has buffers, try to free the buffer mappings | |
527 | * associated with this page. If we succeed we try to free | |
528 | * the page as well. | |
529 | * | |
530 | * We do this even if the page is PageDirty(). | |
531 | * try_to_release_page() does not perform I/O, but it is | |
532 | * possible for a page to have PageDirty set, but it is actually | |
533 | * clean (all its buffers are clean). This happens if the | |
534 | * buffers were written out directly, with submit_bh(). ext3 | |
535 | * will do this, as well as the blockdev mapping. | |
536 | * try_to_release_page() will discover that cleanness and will | |
537 | * drop the buffers and mark the page clean - it can be freed. | |
538 | * | |
539 | * Rarely, pages can have buffers and no ->mapping. These are | |
540 | * the pages which were not successfully invalidated in | |
541 | * truncate_complete_page(). We try to drop those buffers here | |
542 | * and if that worked, and the page is no longer mapped into | |
543 | * process address space (page_count == 1) it can be freed. | |
544 | * Otherwise, leave the page on the LRU so it is swappable. | |
545 | */ | |
546 | if (PagePrivate(page)) { | |
547 | if (!try_to_release_page(page, sc->gfp_mask)) | |
548 | goto activate_locked; | |
549 | if (!mapping && page_count(page) == 1) | |
550 | goto free_it; | |
551 | } | |
552 | ||
49d2e9cc CL |
553 | if (!remove_mapping(mapping, page)) |
554 | goto keep_locked; | |
1da177e4 LT |
555 | |
556 | free_it: | |
557 | unlock_page(page); | |
558 | reclaimed++; | |
559 | if (!pagevec_add(&freed_pvec, page)) | |
560 | __pagevec_release_nonlru(&freed_pvec); | |
561 | continue; | |
562 | ||
563 | activate_locked: | |
564 | SetPageActive(page); | |
565 | pgactivate++; | |
566 | keep_locked: | |
567 | unlock_page(page); | |
568 | keep: | |
569 | list_add(&page->lru, &ret_pages); | |
570 | BUG_ON(PageLRU(page)); | |
571 | } | |
572 | list_splice(&ret_pages, page_list); | |
573 | if (pagevec_count(&freed_pvec)) | |
574 | __pagevec_release_nonlru(&freed_pvec); | |
575 | mod_page_state(pgactivate, pgactivate); | |
576 | sc->nr_reclaimed += reclaimed; | |
577 | return reclaimed; | |
578 | } | |
579 | ||
7cbe34cf | 580 | #ifdef CONFIG_MIGRATION |
8419c318 CL |
581 | static inline void move_to_lru(struct page *page) |
582 | { | |
583 | list_del(&page->lru); | |
584 | if (PageActive(page)) { | |
585 | /* | |
586 | * lru_cache_add_active checks that | |
587 | * the PG_active bit is off. | |
588 | */ | |
589 | ClearPageActive(page); | |
590 | lru_cache_add_active(page); | |
591 | } else { | |
592 | lru_cache_add(page); | |
593 | } | |
594 | put_page(page); | |
595 | } | |
596 | ||
597 | /* | |
053837fc | 598 | * Add isolated pages on the list back to the LRU. |
8419c318 CL |
599 | * |
600 | * returns the number of pages put back. | |
601 | */ | |
602 | int putback_lru_pages(struct list_head *l) | |
603 | { | |
604 | struct page *page; | |
605 | struct page *page2; | |
606 | int count = 0; | |
607 | ||
608 | list_for_each_entry_safe(page, page2, l, lru) { | |
609 | move_to_lru(page); | |
610 | count++; | |
611 | } | |
612 | return count; | |
613 | } | |
614 | ||
e965f963 CL |
615 | /* |
616 | * Non migratable page | |
617 | */ | |
618 | int fail_migrate_page(struct page *newpage, struct page *page) | |
619 | { | |
620 | return -EIO; | |
621 | } | |
622 | EXPORT_SYMBOL(fail_migrate_page); | |
623 | ||
49d2e9cc CL |
624 | /* |
625 | * swapout a single page | |
626 | * page is locked upon entry, unlocked on exit | |
49d2e9cc CL |
627 | */ |
628 | static int swap_page(struct page *page) | |
629 | { | |
630 | struct address_space *mapping = page_mapping(page); | |
631 | ||
632 | if (page_mapped(page) && mapping) | |
418aade4 | 633 | if (try_to_unmap(page, 1) != SWAP_SUCCESS) |
49d2e9cc CL |
634 | goto unlock_retry; |
635 | ||
636 | if (PageDirty(page)) { | |
637 | /* Page is dirty, try to write it out here */ | |
638 | switch(pageout(page, mapping)) { | |
639 | case PAGE_KEEP: | |
640 | case PAGE_ACTIVATE: | |
641 | goto unlock_retry; | |
642 | ||
643 | case PAGE_SUCCESS: | |
644 | goto retry; | |
645 | ||
646 | case PAGE_CLEAN: | |
647 | ; /* try to free the page below */ | |
648 | } | |
649 | } | |
650 | ||
651 | if (PagePrivate(page)) { | |
652 | if (!try_to_release_page(page, GFP_KERNEL) || | |
653 | (!mapping && page_count(page) == 1)) | |
654 | goto unlock_retry; | |
655 | } | |
656 | ||
657 | if (remove_mapping(mapping, page)) { | |
658 | /* Success */ | |
659 | unlock_page(page); | |
660 | return 0; | |
661 | } | |
662 | ||
663 | unlock_retry: | |
664 | unlock_page(page); | |
665 | ||
666 | retry: | |
d0d96328 | 667 | return -EAGAIN; |
49d2e9cc | 668 | } |
e965f963 | 669 | EXPORT_SYMBOL(swap_page); |
a48d07af CL |
670 | |
671 | /* | |
672 | * Page migration was first developed in the context of the memory hotplug | |
673 | * project. The main authors of the migration code are: | |
674 | * | |
675 | * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> | |
676 | * Hirokazu Takahashi <taka@valinux.co.jp> | |
677 | * Dave Hansen <haveblue@us.ibm.com> | |
678 | * Christoph Lameter <clameter@sgi.com> | |
679 | */ | |
680 | ||
681 | /* | |
682 | * Remove references for a page and establish the new page with the correct | |
683 | * basic settings to be able to stop accesses to the page. | |
684 | */ | |
e965f963 | 685 | int migrate_page_remove_references(struct page *newpage, |
a48d07af CL |
686 | struct page *page, int nr_refs) |
687 | { | |
688 | struct address_space *mapping = page_mapping(page); | |
689 | struct page **radix_pointer; | |
690 | ||
691 | /* | |
692 | * Avoid doing any of the following work if the page count | |
693 | * indicates that the page is in use or truncate has removed | |
694 | * the page. | |
695 | */ | |
696 | if (!mapping || page_mapcount(page) + nr_refs != page_count(page)) | |
4983da07 | 697 | return -EAGAIN; |
a48d07af CL |
698 | |
699 | /* | |
700 | * Establish swap ptes for anonymous pages or destroy pte | |
701 | * maps for files. | |
702 | * | |
703 | * In order to reestablish file backed mappings the fault handlers | |
704 | * will take the radix tree_lock which may then be used to stop | |
705 | * processses from accessing this page until the new page is ready. | |
706 | * | |
707 | * A process accessing via a swap pte (an anonymous page) will take a | |
708 | * page_lock on the old page which will block the process until the | |
709 | * migration attempt is complete. At that time the PageSwapCache bit | |
710 | * will be examined. If the page was migrated then the PageSwapCache | |
711 | * bit will be clear and the operation to retrieve the page will be | |
712 | * retried which will find the new page in the radix tree. Then a new | |
713 | * direct mapping may be generated based on the radix tree contents. | |
714 | * | |
715 | * If the page was not migrated then the PageSwapCache bit | |
716 | * is still set and the operation may continue. | |
717 | */ | |
4983da07 CL |
718 | if (try_to_unmap(page, 1) == SWAP_FAIL) |
719 | /* A vma has VM_LOCKED set -> Permanent failure */ | |
720 | return -EPERM; | |
a48d07af CL |
721 | |
722 | /* | |
723 | * Give up if we were unable to remove all mappings. | |
724 | */ | |
725 | if (page_mapcount(page)) | |
4983da07 | 726 | return -EAGAIN; |
a48d07af CL |
727 | |
728 | write_lock_irq(&mapping->tree_lock); | |
729 | ||
730 | radix_pointer = (struct page **)radix_tree_lookup_slot( | |
731 | &mapping->page_tree, | |
732 | page_index(page)); | |
733 | ||
734 | if (!page_mapping(page) || page_count(page) != nr_refs || | |
735 | *radix_pointer != page) { | |
736 | write_unlock_irq(&mapping->tree_lock); | |
4983da07 | 737 | return -EAGAIN; |
a48d07af CL |
738 | } |
739 | ||
740 | /* | |
741 | * Now we know that no one else is looking at the page. | |
742 | * | |
743 | * Certain minimal information about a page must be available | |
744 | * in order for other subsystems to properly handle the page if they | |
745 | * find it through the radix tree update before we are finished | |
746 | * copying the page. | |
747 | */ | |
748 | get_page(newpage); | |
749 | newpage->index = page->index; | |
750 | newpage->mapping = page->mapping; | |
751 | if (PageSwapCache(page)) { | |
752 | SetPageSwapCache(newpage); | |
753 | set_page_private(newpage, page_private(page)); | |
754 | } | |
755 | ||
756 | *radix_pointer = newpage; | |
757 | __put_page(page); | |
758 | write_unlock_irq(&mapping->tree_lock); | |
759 | ||
760 | return 0; | |
761 | } | |
e965f963 | 762 | EXPORT_SYMBOL(migrate_page_remove_references); |
a48d07af CL |
763 | |
764 | /* | |
765 | * Copy the page to its new location | |
766 | */ | |
767 | void migrate_page_copy(struct page *newpage, struct page *page) | |
768 | { | |
769 | copy_highpage(newpage, page); | |
770 | ||
771 | if (PageError(page)) | |
772 | SetPageError(newpage); | |
773 | if (PageReferenced(page)) | |
774 | SetPageReferenced(newpage); | |
775 | if (PageUptodate(page)) | |
776 | SetPageUptodate(newpage); | |
777 | if (PageActive(page)) | |
778 | SetPageActive(newpage); | |
779 | if (PageChecked(page)) | |
780 | SetPageChecked(newpage); | |
781 | if (PageMappedToDisk(page)) | |
782 | SetPageMappedToDisk(newpage); | |
783 | ||
784 | if (PageDirty(page)) { | |
785 | clear_page_dirty_for_io(page); | |
786 | set_page_dirty(newpage); | |
787 | } | |
788 | ||
789 | ClearPageSwapCache(page); | |
790 | ClearPageActive(page); | |
791 | ClearPagePrivate(page); | |
792 | set_page_private(page, 0); | |
793 | page->mapping = NULL; | |
794 | ||
795 | /* | |
796 | * If any waiters have accumulated on the new page then | |
797 | * wake them up. | |
798 | */ | |
799 | if (PageWriteback(newpage)) | |
800 | end_page_writeback(newpage); | |
801 | } | |
e965f963 | 802 | EXPORT_SYMBOL(migrate_page_copy); |
a48d07af CL |
803 | |
804 | /* | |
805 | * Common logic to directly migrate a single page suitable for | |
806 | * pages that do not use PagePrivate. | |
807 | * | |
808 | * Pages are locked upon entry and exit. | |
809 | */ | |
810 | int migrate_page(struct page *newpage, struct page *page) | |
811 | { | |
4983da07 CL |
812 | int rc; |
813 | ||
a48d07af CL |
814 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ |
815 | ||
4983da07 CL |
816 | rc = migrate_page_remove_references(newpage, page, 2); |
817 | ||
818 | if (rc) | |
819 | return rc; | |
a48d07af CL |
820 | |
821 | migrate_page_copy(newpage, page); | |
822 | ||
a3351e52 CL |
823 | /* |
824 | * Remove auxiliary swap entries and replace | |
825 | * them with real ptes. | |
826 | * | |
827 | * Note that a real pte entry will allow processes that are not | |
828 | * waiting on the page lock to use the new page via the page tables | |
829 | * before the new page is unlocked. | |
830 | */ | |
831 | remove_from_swap(newpage); | |
a48d07af CL |
832 | return 0; |
833 | } | |
e965f963 | 834 | EXPORT_SYMBOL(migrate_page); |
a48d07af | 835 | |
49d2e9cc CL |
836 | /* |
837 | * migrate_pages | |
838 | * | |
839 | * Two lists are passed to this function. The first list | |
840 | * contains the pages isolated from the LRU to be migrated. | |
841 | * The second list contains new pages that the pages isolated | |
842 | * can be moved to. If the second list is NULL then all | |
843 | * pages are swapped out. | |
844 | * | |
845 | * The function returns after 10 attempts or if no pages | |
418aade4 | 846 | * are movable anymore because to has become empty |
49d2e9cc CL |
847 | * or no retryable pages exist anymore. |
848 | * | |
d0d96328 | 849 | * Return: Number of pages not migrated when "to" ran empty. |
49d2e9cc | 850 | */ |
d4984711 CL |
851 | int migrate_pages(struct list_head *from, struct list_head *to, |
852 | struct list_head *moved, struct list_head *failed) | |
49d2e9cc CL |
853 | { |
854 | int retry; | |
49d2e9cc CL |
855 | int nr_failed = 0; |
856 | int pass = 0; | |
857 | struct page *page; | |
858 | struct page *page2; | |
859 | int swapwrite = current->flags & PF_SWAPWRITE; | |
d0d96328 | 860 | int rc; |
49d2e9cc CL |
861 | |
862 | if (!swapwrite) | |
863 | current->flags |= PF_SWAPWRITE; | |
864 | ||
865 | redo: | |
866 | retry = 0; | |
867 | ||
d4984711 | 868 | list_for_each_entry_safe(page, page2, from, lru) { |
a48d07af CL |
869 | struct page *newpage = NULL; |
870 | struct address_space *mapping; | |
871 | ||
49d2e9cc CL |
872 | cond_resched(); |
873 | ||
d0d96328 CL |
874 | rc = 0; |
875 | if (page_count(page) == 1) | |
ee27497d | 876 | /* page was freed from under us. So we are done. */ |
d0d96328 CL |
877 | goto next; |
878 | ||
a48d07af CL |
879 | if (to && list_empty(to)) |
880 | break; | |
881 | ||
49d2e9cc CL |
882 | /* |
883 | * Skip locked pages during the first two passes to give the | |
7cbe34cf CL |
884 | * functions holding the lock time to release the page. Later we |
885 | * use lock_page() to have a higher chance of acquiring the | |
886 | * lock. | |
49d2e9cc | 887 | */ |
d0d96328 | 888 | rc = -EAGAIN; |
49d2e9cc CL |
889 | if (pass > 2) |
890 | lock_page(page); | |
891 | else | |
892 | if (TestSetPageLocked(page)) | |
d0d96328 | 893 | goto next; |
49d2e9cc CL |
894 | |
895 | /* | |
896 | * Only wait on writeback if we have already done a pass where | |
897 | * we we may have triggered writeouts for lots of pages. | |
898 | */ | |
7cbe34cf | 899 | if (pass > 0) { |
49d2e9cc | 900 | wait_on_page_writeback(page); |
7cbe34cf | 901 | } else { |
d0d96328 CL |
902 | if (PageWriteback(page)) |
903 | goto unlock_page; | |
7cbe34cf | 904 | } |
49d2e9cc | 905 | |
d0d96328 CL |
906 | /* |
907 | * Anonymous pages must have swap cache references otherwise | |
908 | * the information contained in the page maps cannot be | |
909 | * preserved. | |
910 | */ | |
49d2e9cc | 911 | if (PageAnon(page) && !PageSwapCache(page)) { |
1480a540 | 912 | if (!add_to_swap(page, GFP_KERNEL)) { |
d0d96328 CL |
913 | rc = -ENOMEM; |
914 | goto unlock_page; | |
49d2e9cc CL |
915 | } |
916 | } | |
49d2e9cc | 917 | |
a48d07af CL |
918 | if (!to) { |
919 | rc = swap_page(page); | |
920 | goto next; | |
921 | } | |
922 | ||
923 | newpage = lru_to_page(to); | |
924 | lock_page(newpage); | |
925 | ||
49d2e9cc | 926 | /* |
a48d07af | 927 | * Pages are properly locked and writeback is complete. |
49d2e9cc CL |
928 | * Try to migrate the page. |
929 | */ | |
a48d07af CL |
930 | mapping = page_mapping(page); |
931 | if (!mapping) | |
932 | goto unlock_both; | |
933 | ||
e965f963 | 934 | if (mapping->a_ops->migratepage) { |
418aade4 CL |
935 | /* |
936 | * Most pages have a mapping and most filesystems | |
937 | * should provide a migration function. Anonymous | |
938 | * pages are part of swap space which also has its | |
939 | * own migration function. This is the most common | |
940 | * path for page migration. | |
941 | */ | |
e965f963 CL |
942 | rc = mapping->a_ops->migratepage(newpage, page); |
943 | goto unlock_both; | |
944 | } | |
945 | ||
a48d07af | 946 | /* |
418aade4 CL |
947 | * Default handling if a filesystem does not provide |
948 | * a migration function. We can only migrate clean | |
949 | * pages so try to write out any dirty pages first. | |
a48d07af CL |
950 | */ |
951 | if (PageDirty(page)) { | |
952 | switch (pageout(page, mapping)) { | |
953 | case PAGE_KEEP: | |
954 | case PAGE_ACTIVATE: | |
955 | goto unlock_both; | |
956 | ||
957 | case PAGE_SUCCESS: | |
958 | unlock_page(newpage); | |
959 | goto next; | |
960 | ||
961 | case PAGE_CLEAN: | |
962 | ; /* try to migrate the page below */ | |
963 | } | |
964 | } | |
418aade4 | 965 | |
a48d07af | 966 | /* |
418aade4 CL |
967 | * Buffers are managed in a filesystem specific way. |
968 | * We must have no buffers or drop them. | |
a48d07af CL |
969 | */ |
970 | if (!page_has_buffers(page) || | |
971 | try_to_release_page(page, GFP_KERNEL)) { | |
972 | rc = migrate_page(newpage, page); | |
973 | goto unlock_both; | |
974 | } | |
975 | ||
976 | /* | |
977 | * On early passes with mapped pages simply | |
978 | * retry. There may be a lock held for some | |
979 | * buffers that may go away. Later | |
980 | * swap them out. | |
981 | */ | |
982 | if (pass > 4) { | |
418aade4 CL |
983 | /* |
984 | * Persistently unable to drop buffers..... As a | |
985 | * measure of last resort we fall back to | |
986 | * swap_page(). | |
987 | */ | |
a48d07af CL |
988 | unlock_page(newpage); |
989 | newpage = NULL; | |
990 | rc = swap_page(page); | |
991 | goto next; | |
992 | } | |
993 | ||
994 | unlock_both: | |
995 | unlock_page(newpage); | |
d0d96328 CL |
996 | |
997 | unlock_page: | |
998 | unlock_page(page); | |
999 | ||
1000 | next: | |
1001 | if (rc == -EAGAIN) { | |
1002 | retry++; | |
1003 | } else if (rc) { | |
1004 | /* Permanent failure */ | |
1005 | list_move(&page->lru, failed); | |
1006 | nr_failed++; | |
1007 | } else { | |
a48d07af CL |
1008 | if (newpage) { |
1009 | /* Successful migration. Return page to LRU */ | |
1010 | move_to_lru(newpage); | |
1011 | } | |
d4984711 | 1012 | list_move(&page->lru, moved); |
d4984711 | 1013 | } |
49d2e9cc CL |
1014 | } |
1015 | if (retry && pass++ < 10) | |
1016 | goto redo; | |
1017 | ||
1018 | if (!swapwrite) | |
1019 | current->flags &= ~PF_SWAPWRITE; | |
1020 | ||
49d2e9cc CL |
1021 | return nr_failed + retry; |
1022 | } | |
8419c318 | 1023 | |
8419c318 CL |
1024 | /* |
1025 | * Isolate one page from the LRU lists and put it on the | |
053837fc | 1026 | * indicated list with elevated refcount. |
8419c318 CL |
1027 | * |
1028 | * Result: | |
1029 | * 0 = page not on LRU list | |
1030 | * 1 = page removed from LRU list and added to the specified list. | |
8419c318 CL |
1031 | */ |
1032 | int isolate_lru_page(struct page *page) | |
1033 | { | |
053837fc | 1034 | int ret = 0; |
8419c318 | 1035 | |
053837fc NP |
1036 | if (PageLRU(page)) { |
1037 | struct zone *zone = page_zone(page); | |
1038 | spin_lock_irq(&zone->lru_lock); | |
8d438f96 | 1039 | if (PageLRU(page)) { |
053837fc NP |
1040 | ret = 1; |
1041 | get_page(page); | |
8d438f96 | 1042 | ClearPageLRU(page); |
053837fc NP |
1043 | if (PageActive(page)) |
1044 | del_page_from_active_list(zone, page); | |
1045 | else | |
1046 | del_page_from_inactive_list(zone, page); | |
1047 | } | |
1048 | spin_unlock_irq(&zone->lru_lock); | |
8419c318 | 1049 | } |
053837fc NP |
1050 | |
1051 | return ret; | |
8419c318 | 1052 | } |
7cbe34cf | 1053 | #endif |
49d2e9cc | 1054 | |
1da177e4 LT |
1055 | /* |
1056 | * zone->lru_lock is heavily contended. Some of the functions that | |
1057 | * shrink the lists perform better by taking out a batch of pages | |
1058 | * and working on them outside the LRU lock. | |
1059 | * | |
1060 | * For pagecache intensive workloads, this function is the hottest | |
1061 | * spot in the kernel (apart from copy_*_user functions). | |
1062 | * | |
1063 | * Appropriate locks must be held before calling this function. | |
1064 | * | |
1065 | * @nr_to_scan: The number of pages to look through on the list. | |
1066 | * @src: The LRU list to pull pages off. | |
1067 | * @dst: The temp list to put pages on to. | |
1068 | * @scanned: The number of pages that were scanned. | |
1069 | * | |
1070 | * returns how many pages were moved onto *@dst. | |
1071 | */ | |
1072 | static int isolate_lru_pages(int nr_to_scan, struct list_head *src, | |
1073 | struct list_head *dst, int *scanned) | |
1074 | { | |
1075 | int nr_taken = 0; | |
1076 | struct page *page; | |
1077 | int scan = 0; | |
1078 | ||
1079 | while (scan++ < nr_to_scan && !list_empty(src)) { | |
7c8ee9a8 | 1080 | struct list_head *target; |
1da177e4 LT |
1081 | page = lru_to_page(src); |
1082 | prefetchw_prev_lru_page(page, src, flags); | |
1083 | ||
8d438f96 NP |
1084 | BUG_ON(!PageLRU(page)); |
1085 | ||
053837fc | 1086 | list_del(&page->lru); |
7c8ee9a8 NP |
1087 | target = src; |
1088 | if (likely(get_page_unless_zero(page))) { | |
053837fc | 1089 | /* |
7c8ee9a8 NP |
1090 | * Be careful not to clear PageLRU until after we're |
1091 | * sure the page is not being freed elsewhere -- the | |
1092 | * page release code relies on it. | |
053837fc | 1093 | */ |
7c8ee9a8 NP |
1094 | ClearPageLRU(page); |
1095 | target = dst; | |
1096 | nr_taken++; | |
1097 | } /* else it is being freed elsewhere */ | |
46453a6e | 1098 | |
7c8ee9a8 | 1099 | list_add(&page->lru, target); |
1da177e4 LT |
1100 | } |
1101 | ||
1102 | *scanned = scan; | |
1103 | return nr_taken; | |
1104 | } | |
1105 | ||
1106 | /* | |
1107 | * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed | |
1108 | */ | |
8695949a | 1109 | static void shrink_cache(int max_scan, struct zone *zone, struct scan_control *sc) |
1da177e4 LT |
1110 | { |
1111 | LIST_HEAD(page_list); | |
1112 | struct pagevec pvec; | |
1da177e4 LT |
1113 | |
1114 | pagevec_init(&pvec, 1); | |
1115 | ||
1116 | lru_add_drain(); | |
1117 | spin_lock_irq(&zone->lru_lock); | |
1118 | while (max_scan > 0) { | |
1119 | struct page *page; | |
1120 | int nr_taken; | |
1121 | int nr_scan; | |
1122 | int nr_freed; | |
1123 | ||
1124 | nr_taken = isolate_lru_pages(sc->swap_cluster_max, | |
1125 | &zone->inactive_list, | |
1126 | &page_list, &nr_scan); | |
1127 | zone->nr_inactive -= nr_taken; | |
1128 | zone->pages_scanned += nr_scan; | |
1129 | spin_unlock_irq(&zone->lru_lock); | |
1130 | ||
1131 | if (nr_taken == 0) | |
1132 | goto done; | |
1133 | ||
1134 | max_scan -= nr_scan; | |
1da177e4 | 1135 | nr_freed = shrink_list(&page_list, sc); |
1da177e4 | 1136 | |
a74609fa NP |
1137 | local_irq_disable(); |
1138 | if (current_is_kswapd()) { | |
1139 | __mod_page_state_zone(zone, pgscan_kswapd, nr_scan); | |
1140 | __mod_page_state(kswapd_steal, nr_freed); | |
1141 | } else | |
1142 | __mod_page_state_zone(zone, pgscan_direct, nr_scan); | |
1143 | __mod_page_state_zone(zone, pgsteal, nr_freed); | |
1144 | ||
1145 | spin_lock(&zone->lru_lock); | |
1da177e4 LT |
1146 | /* |
1147 | * Put back any unfreeable pages. | |
1148 | */ | |
1149 | while (!list_empty(&page_list)) { | |
1150 | page = lru_to_page(&page_list); | |
8d438f96 NP |
1151 | BUG_ON(PageLRU(page)); |
1152 | SetPageLRU(page); | |
1da177e4 LT |
1153 | list_del(&page->lru); |
1154 | if (PageActive(page)) | |
1155 | add_page_to_active_list(zone, page); | |
1156 | else | |
1157 | add_page_to_inactive_list(zone, page); | |
1158 | if (!pagevec_add(&pvec, page)) { | |
1159 | spin_unlock_irq(&zone->lru_lock); | |
1160 | __pagevec_release(&pvec); | |
1161 | spin_lock_irq(&zone->lru_lock); | |
1162 | } | |
1163 | } | |
1164 | } | |
1165 | spin_unlock_irq(&zone->lru_lock); | |
1166 | done: | |
1167 | pagevec_release(&pvec); | |
1168 | } | |
1169 | ||
1170 | /* | |
1171 | * This moves pages from the active list to the inactive list. | |
1172 | * | |
1173 | * We move them the other way if the page is referenced by one or more | |
1174 | * processes, from rmap. | |
1175 | * | |
1176 | * If the pages are mostly unmapped, the processing is fast and it is | |
1177 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
1178 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
1179 | * should drop zone->lru_lock around each page. It's impossible to balance | |
1180 | * this, so instead we remove the pages from the LRU while processing them. | |
1181 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
1182 | * nobody will play with that bit on a non-LRU page. | |
1183 | * | |
1184 | * The downside is that we have to touch page->_count against each page. | |
1185 | * But we had to alter page->flags anyway. | |
1186 | */ | |
1187 | static void | |
8695949a | 1188 | refill_inactive_zone(int nr_pages, struct zone *zone, struct scan_control *sc) |
1da177e4 LT |
1189 | { |
1190 | int pgmoved; | |
1191 | int pgdeactivate = 0; | |
1192 | int pgscanned; | |
1da177e4 LT |
1193 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1194 | LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ | |
1195 | LIST_HEAD(l_active); /* Pages to go onto the active_list */ | |
1196 | struct page *page; | |
1197 | struct pagevec pvec; | |
1198 | int reclaim_mapped = 0; | |
2903fb16 CL |
1199 | |
1200 | if (unlikely(sc->may_swap)) { | |
1201 | long mapped_ratio; | |
1202 | long distress; | |
1203 | long swap_tendency; | |
1204 | ||
1205 | /* | |
1206 | * `distress' is a measure of how much trouble we're having | |
1207 | * reclaiming pages. 0 -> no problems. 100 -> great trouble. | |
1208 | */ | |
1209 | distress = 100 >> zone->prev_priority; | |
1210 | ||
1211 | /* | |
1212 | * The point of this algorithm is to decide when to start | |
1213 | * reclaiming mapped memory instead of just pagecache. Work out | |
1214 | * how much memory | |
1215 | * is mapped. | |
1216 | */ | |
1217 | mapped_ratio = (sc->nr_mapped * 100) / total_memory; | |
1218 | ||
1219 | /* | |
1220 | * Now decide how much we really want to unmap some pages. The | |
1221 | * mapped ratio is downgraded - just because there's a lot of | |
1222 | * mapped memory doesn't necessarily mean that page reclaim | |
1223 | * isn't succeeding. | |
1224 | * | |
1225 | * The distress ratio is important - we don't want to start | |
1226 | * going oom. | |
1227 | * | |
1228 | * A 100% value of vm_swappiness overrides this algorithm | |
1229 | * altogether. | |
1230 | */ | |
1231 | swap_tendency = mapped_ratio / 2 + distress + vm_swappiness; | |
1232 | ||
1233 | /* | |
1234 | * Now use this metric to decide whether to start moving mapped | |
1235 | * memory onto the inactive list. | |
1236 | */ | |
1237 | if (swap_tendency >= 100) | |
1238 | reclaim_mapped = 1; | |
1239 | } | |
1da177e4 LT |
1240 | |
1241 | lru_add_drain(); | |
1242 | spin_lock_irq(&zone->lru_lock); | |
1243 | pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, | |
1244 | &l_hold, &pgscanned); | |
1245 | zone->pages_scanned += pgscanned; | |
1246 | zone->nr_active -= pgmoved; | |
1247 | spin_unlock_irq(&zone->lru_lock); | |
1248 | ||
1da177e4 LT |
1249 | while (!list_empty(&l_hold)) { |
1250 | cond_resched(); | |
1251 | page = lru_to_page(&l_hold); | |
1252 | list_del(&page->lru); | |
1253 | if (page_mapped(page)) { | |
1254 | if (!reclaim_mapped || | |
1255 | (total_swap_pages == 0 && PageAnon(page)) || | |
f7b7fd8f | 1256 | page_referenced(page, 0)) { |
1da177e4 LT |
1257 | list_add(&page->lru, &l_active); |
1258 | continue; | |
1259 | } | |
1260 | } | |
1261 | list_add(&page->lru, &l_inactive); | |
1262 | } | |
1263 | ||
1264 | pagevec_init(&pvec, 1); | |
1265 | pgmoved = 0; | |
1266 | spin_lock_irq(&zone->lru_lock); | |
1267 | while (!list_empty(&l_inactive)) { | |
1268 | page = lru_to_page(&l_inactive); | |
1269 | prefetchw_prev_lru_page(page, &l_inactive, flags); | |
8d438f96 NP |
1270 | BUG_ON(PageLRU(page)); |
1271 | SetPageLRU(page); | |
4c84cacf NP |
1272 | BUG_ON(!PageActive(page)); |
1273 | ClearPageActive(page); | |
1274 | ||
1da177e4 LT |
1275 | list_move(&page->lru, &zone->inactive_list); |
1276 | pgmoved++; | |
1277 | if (!pagevec_add(&pvec, page)) { | |
1278 | zone->nr_inactive += pgmoved; | |
1279 | spin_unlock_irq(&zone->lru_lock); | |
1280 | pgdeactivate += pgmoved; | |
1281 | pgmoved = 0; | |
1282 | if (buffer_heads_over_limit) | |
1283 | pagevec_strip(&pvec); | |
1284 | __pagevec_release(&pvec); | |
1285 | spin_lock_irq(&zone->lru_lock); | |
1286 | } | |
1287 | } | |
1288 | zone->nr_inactive += pgmoved; | |
1289 | pgdeactivate += pgmoved; | |
1290 | if (buffer_heads_over_limit) { | |
1291 | spin_unlock_irq(&zone->lru_lock); | |
1292 | pagevec_strip(&pvec); | |
1293 | spin_lock_irq(&zone->lru_lock); | |
1294 | } | |
1295 | ||
1296 | pgmoved = 0; | |
1297 | while (!list_empty(&l_active)) { | |
1298 | page = lru_to_page(&l_active); | |
1299 | prefetchw_prev_lru_page(page, &l_active, flags); | |
8d438f96 NP |
1300 | BUG_ON(PageLRU(page)); |
1301 | SetPageLRU(page); | |
1da177e4 LT |
1302 | BUG_ON(!PageActive(page)); |
1303 | list_move(&page->lru, &zone->active_list); | |
1304 | pgmoved++; | |
1305 | if (!pagevec_add(&pvec, page)) { | |
1306 | zone->nr_active += pgmoved; | |
1307 | pgmoved = 0; | |
1308 | spin_unlock_irq(&zone->lru_lock); | |
1309 | __pagevec_release(&pvec); | |
1310 | spin_lock_irq(&zone->lru_lock); | |
1311 | } | |
1312 | } | |
1313 | zone->nr_active += pgmoved; | |
a74609fa NP |
1314 | spin_unlock(&zone->lru_lock); |
1315 | ||
1316 | __mod_page_state_zone(zone, pgrefill, pgscanned); | |
1317 | __mod_page_state(pgdeactivate, pgdeactivate); | |
1318 | local_irq_enable(); | |
1da177e4 | 1319 | |
a74609fa | 1320 | pagevec_release(&pvec); |
1da177e4 LT |
1321 | } |
1322 | ||
1323 | /* | |
1324 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
1325 | */ | |
1326 | static void | |
8695949a | 1327 | shrink_zone(int priority, struct zone *zone, struct scan_control *sc) |
1da177e4 LT |
1328 | { |
1329 | unsigned long nr_active; | |
1330 | unsigned long nr_inactive; | |
8695949a | 1331 | unsigned long nr_to_scan; |
1da177e4 | 1332 | |
53e9a615 MH |
1333 | atomic_inc(&zone->reclaim_in_progress); |
1334 | ||
1da177e4 LT |
1335 | /* |
1336 | * Add one to `nr_to_scan' just to make sure that the kernel will | |
1337 | * slowly sift through the active list. | |
1338 | */ | |
8695949a | 1339 | zone->nr_scan_active += (zone->nr_active >> priority) + 1; |
1da177e4 LT |
1340 | nr_active = zone->nr_scan_active; |
1341 | if (nr_active >= sc->swap_cluster_max) | |
1342 | zone->nr_scan_active = 0; | |
1343 | else | |
1344 | nr_active = 0; | |
1345 | ||
8695949a | 1346 | zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1; |
1da177e4 LT |
1347 | nr_inactive = zone->nr_scan_inactive; |
1348 | if (nr_inactive >= sc->swap_cluster_max) | |
1349 | zone->nr_scan_inactive = 0; | |
1350 | else | |
1351 | nr_inactive = 0; | |
1352 | ||
1da177e4 LT |
1353 | while (nr_active || nr_inactive) { |
1354 | if (nr_active) { | |
8695949a | 1355 | nr_to_scan = min(nr_active, |
1da177e4 | 1356 | (unsigned long)sc->swap_cluster_max); |
8695949a CL |
1357 | nr_active -= nr_to_scan; |
1358 | refill_inactive_zone(nr_to_scan, zone, sc); | |
1da177e4 LT |
1359 | } |
1360 | ||
1361 | if (nr_inactive) { | |
8695949a | 1362 | nr_to_scan = min(nr_inactive, |
1da177e4 | 1363 | (unsigned long)sc->swap_cluster_max); |
8695949a CL |
1364 | nr_inactive -= nr_to_scan; |
1365 | shrink_cache(nr_to_scan, zone, sc); | |
1da177e4 LT |
1366 | } |
1367 | } | |
1368 | ||
1369 | throttle_vm_writeout(); | |
53e9a615 MH |
1370 | |
1371 | atomic_dec(&zone->reclaim_in_progress); | |
1da177e4 LT |
1372 | } |
1373 | ||
1374 | /* | |
1375 | * This is the direct reclaim path, for page-allocating processes. We only | |
1376 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
1377 | * request. | |
1378 | * | |
1379 | * We reclaim from a zone even if that zone is over pages_high. Because: | |
1380 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order | |
1381 | * allocation or | |
1382 | * b) The zones may be over pages_high but they must go *over* pages_high to | |
1383 | * satisfy the `incremental min' zone defense algorithm. | |
1384 | * | |
1385 | * Returns the number of reclaimed pages. | |
1386 | * | |
1387 | * If a zone is deemed to be full of pinned pages then just give it a light | |
1388 | * scan then give up on it. | |
1389 | */ | |
1390 | static void | |
8695949a | 1391 | shrink_caches(int priority, struct zone **zones, struct scan_control *sc) |
1da177e4 LT |
1392 | { |
1393 | int i; | |
1394 | ||
1395 | for (i = 0; zones[i] != NULL; i++) { | |
1396 | struct zone *zone = zones[i]; | |
1397 | ||
f3fe6512 | 1398 | if (!populated_zone(zone)) |
1da177e4 LT |
1399 | continue; |
1400 | ||
9bf2229f | 1401 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1402 | continue; |
1403 | ||
8695949a CL |
1404 | zone->temp_priority = priority; |
1405 | if (zone->prev_priority > priority) | |
1406 | zone->prev_priority = priority; | |
1da177e4 | 1407 | |
8695949a | 1408 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
1da177e4 LT |
1409 | continue; /* Let kswapd poll it */ |
1410 | ||
8695949a | 1411 | shrink_zone(priority, zone, sc); |
1da177e4 LT |
1412 | } |
1413 | } | |
1414 | ||
1415 | /* | |
1416 | * This is the main entry point to direct page reclaim. | |
1417 | * | |
1418 | * If a full scan of the inactive list fails to free enough memory then we | |
1419 | * are "out of memory" and something needs to be killed. | |
1420 | * | |
1421 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
1422 | * high - the zone may be full of dirty or under-writeback pages, which this | |
1423 | * caller can't do much about. We kick pdflush and take explicit naps in the | |
1424 | * hope that some of these pages can be written. But if the allocating task | |
1425 | * holds filesystem locks which prevent writeout this might not work, and the | |
1426 | * allocation attempt will fail. | |
1427 | */ | |
6daa0e28 | 1428 | int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) |
1da177e4 LT |
1429 | { |
1430 | int priority; | |
1431 | int ret = 0; | |
1432 | int total_scanned = 0, total_reclaimed = 0; | |
1433 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1434 | struct scan_control sc; | |
1435 | unsigned long lru_pages = 0; | |
1436 | int i; | |
1437 | ||
1438 | sc.gfp_mask = gfp_mask; | |
52a8363e | 1439 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1440 | sc.may_swap = 1; |
1da177e4 LT |
1441 | |
1442 | inc_page_state(allocstall); | |
1443 | ||
1444 | for (i = 0; zones[i] != NULL; i++) { | |
1445 | struct zone *zone = zones[i]; | |
1446 | ||
9bf2229f | 1447 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1448 | continue; |
1449 | ||
1450 | zone->temp_priority = DEF_PRIORITY; | |
1451 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1452 | } | |
1453 | ||
1454 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1455 | sc.nr_mapped = read_page_state(nr_mapped); | |
1456 | sc.nr_scanned = 0; | |
1457 | sc.nr_reclaimed = 0; | |
1da177e4 | 1458 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; |
f7b7fd8f RR |
1459 | if (!priority) |
1460 | disable_swap_token(); | |
8695949a | 1461 | shrink_caches(priority, zones, &sc); |
1da177e4 LT |
1462 | shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); |
1463 | if (reclaim_state) { | |
1464 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; | |
1465 | reclaim_state->reclaimed_slab = 0; | |
1466 | } | |
1467 | total_scanned += sc.nr_scanned; | |
1468 | total_reclaimed += sc.nr_reclaimed; | |
1469 | if (total_reclaimed >= sc.swap_cluster_max) { | |
1470 | ret = 1; | |
1471 | goto out; | |
1472 | } | |
1473 | ||
1474 | /* | |
1475 | * Try to write back as many pages as we just scanned. This | |
1476 | * tends to cause slow streaming writers to write data to the | |
1477 | * disk smoothly, at the dirtying rate, which is nice. But | |
1478 | * that's undesirable in laptop mode, where we *want* lumpy | |
1479 | * writeout. So in laptop mode, write out the whole world. | |
1480 | */ | |
1481 | if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) { | |
687a21ce | 1482 | wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
1da177e4 LT |
1483 | sc.may_writepage = 1; |
1484 | } | |
1485 | ||
1486 | /* Take a nap, wait for some writeback to complete */ | |
1487 | if (sc.nr_scanned && priority < DEF_PRIORITY - 2) | |
1488 | blk_congestion_wait(WRITE, HZ/10); | |
1489 | } | |
1490 | out: | |
1491 | for (i = 0; zones[i] != 0; i++) { | |
1492 | struct zone *zone = zones[i]; | |
1493 | ||
9bf2229f | 1494 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1495 | continue; |
1496 | ||
1497 | zone->prev_priority = zone->temp_priority; | |
1498 | } | |
1499 | return ret; | |
1500 | } | |
1501 | ||
1502 | /* | |
1503 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
1504 | * they are all at pages_high. | |
1505 | * | |
1506 | * If `nr_pages' is non-zero then it is the number of pages which are to be | |
1507 | * reclaimed, regardless of the zone occupancies. This is a software suspend | |
1508 | * special. | |
1509 | * | |
1510 | * Returns the number of pages which were actually freed. | |
1511 | * | |
1512 | * There is special handling here for zones which are full of pinned pages. | |
1513 | * This can happen if the pages are all mlocked, or if they are all used by | |
1514 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
1515 | * What we do is to detect the case where all pages in the zone have been | |
1516 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
1517 | * dead and from now on, only perform a short scan. Basically we're polling | |
1518 | * the zone for when the problem goes away. | |
1519 | * | |
1520 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
1521 | * zones which have free_pages > pages_high, but once a zone is found to have | |
1522 | * free_pages <= pages_high, we scan that zone and the lower zones regardless | |
1523 | * of the number of free pages in the lower zones. This interoperates with | |
1524 | * the page allocator fallback scheme to ensure that aging of pages is balanced | |
1525 | * across the zones. | |
1526 | */ | |
1527 | static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) | |
1528 | { | |
1529 | int to_free = nr_pages; | |
1530 | int all_zones_ok; | |
1531 | int priority; | |
1532 | int i; | |
1533 | int total_scanned, total_reclaimed; | |
1534 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1535 | struct scan_control sc; | |
1536 | ||
1537 | loop_again: | |
1538 | total_scanned = 0; | |
1539 | total_reclaimed = 0; | |
1540 | sc.gfp_mask = GFP_KERNEL; | |
52a8363e | 1541 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1542 | sc.may_swap = 1; |
1da177e4 LT |
1543 | sc.nr_mapped = read_page_state(nr_mapped); |
1544 | ||
1545 | inc_page_state(pageoutrun); | |
1546 | ||
1547 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1548 | struct zone *zone = pgdat->node_zones + i; | |
1549 | ||
1550 | zone->temp_priority = DEF_PRIORITY; | |
1551 | } | |
1552 | ||
1553 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1554 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ | |
1555 | unsigned long lru_pages = 0; | |
1556 | ||
f7b7fd8f RR |
1557 | /* The swap token gets in the way of swapout... */ |
1558 | if (!priority) | |
1559 | disable_swap_token(); | |
1560 | ||
1da177e4 LT |
1561 | all_zones_ok = 1; |
1562 | ||
1563 | if (nr_pages == 0) { | |
1564 | /* | |
1565 | * Scan in the highmem->dma direction for the highest | |
1566 | * zone which needs scanning | |
1567 | */ | |
1568 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
1569 | struct zone *zone = pgdat->node_zones + i; | |
1570 | ||
f3fe6512 | 1571 | if (!populated_zone(zone)) |
1da177e4 LT |
1572 | continue; |
1573 | ||
1574 | if (zone->all_unreclaimable && | |
1575 | priority != DEF_PRIORITY) | |
1576 | continue; | |
1577 | ||
1578 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1579 | zone->pages_high, 0, 0)) { |
1da177e4 LT |
1580 | end_zone = i; |
1581 | goto scan; | |
1582 | } | |
1583 | } | |
1584 | goto out; | |
1585 | } else { | |
1586 | end_zone = pgdat->nr_zones - 1; | |
1587 | } | |
1588 | scan: | |
1589 | for (i = 0; i <= end_zone; i++) { | |
1590 | struct zone *zone = pgdat->node_zones + i; | |
1591 | ||
1592 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1593 | } | |
1594 | ||
1595 | /* | |
1596 | * Now scan the zone in the dma->highmem direction, stopping | |
1597 | * at the last zone which needs scanning. | |
1598 | * | |
1599 | * We do this because the page allocator works in the opposite | |
1600 | * direction. This prevents the page allocator from allocating | |
1601 | * pages behind kswapd's direction of progress, which would | |
1602 | * cause too much scanning of the lower zones. | |
1603 | */ | |
1604 | for (i = 0; i <= end_zone; i++) { | |
1605 | struct zone *zone = pgdat->node_zones + i; | |
b15e0905 | 1606 | int nr_slab; |
1da177e4 | 1607 | |
f3fe6512 | 1608 | if (!populated_zone(zone)) |
1da177e4 LT |
1609 | continue; |
1610 | ||
1611 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) | |
1612 | continue; | |
1613 | ||
1614 | if (nr_pages == 0) { /* Not software suspend */ | |
1615 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1616 | zone->pages_high, end_zone, 0)) |
1da177e4 LT |
1617 | all_zones_ok = 0; |
1618 | } | |
1619 | zone->temp_priority = priority; | |
1620 | if (zone->prev_priority > priority) | |
1621 | zone->prev_priority = priority; | |
1622 | sc.nr_scanned = 0; | |
1623 | sc.nr_reclaimed = 0; | |
1da177e4 | 1624 | sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; |
8695949a | 1625 | shrink_zone(priority, zone, &sc); |
1da177e4 | 1626 | reclaim_state->reclaimed_slab = 0; |
b15e0905 AM |
1627 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
1628 | lru_pages); | |
1da177e4 LT |
1629 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
1630 | total_reclaimed += sc.nr_reclaimed; | |
1631 | total_scanned += sc.nr_scanned; | |
1632 | if (zone->all_unreclaimable) | |
1633 | continue; | |
b15e0905 AM |
1634 | if (nr_slab == 0 && zone->pages_scanned >= |
1635 | (zone->nr_active + zone->nr_inactive) * 4) | |
1da177e4 LT |
1636 | zone->all_unreclaimable = 1; |
1637 | /* | |
1638 | * If we've done a decent amount of scanning and | |
1639 | * the reclaim ratio is low, start doing writepage | |
1640 | * even in laptop mode | |
1641 | */ | |
1642 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && | |
1643 | total_scanned > total_reclaimed+total_reclaimed/2) | |
1644 | sc.may_writepage = 1; | |
1645 | } | |
1646 | if (nr_pages && to_free > total_reclaimed) | |
1647 | continue; /* swsusp: need to do more work */ | |
1648 | if (all_zones_ok) | |
1649 | break; /* kswapd: all done */ | |
1650 | /* | |
1651 | * OK, kswapd is getting into trouble. Take a nap, then take | |
1652 | * another pass across the zones. | |
1653 | */ | |
1654 | if (total_scanned && priority < DEF_PRIORITY - 2) | |
1655 | blk_congestion_wait(WRITE, HZ/10); | |
1656 | ||
1657 | /* | |
1658 | * We do this so kswapd doesn't build up large priorities for | |
1659 | * example when it is freeing in parallel with allocators. It | |
1660 | * matches the direct reclaim path behaviour in terms of impact | |
1661 | * on zone->*_priority. | |
1662 | */ | |
1663 | if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) | |
1664 | break; | |
1665 | } | |
1666 | out: | |
1667 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1668 | struct zone *zone = pgdat->node_zones + i; | |
1669 | ||
1670 | zone->prev_priority = zone->temp_priority; | |
1671 | } | |
1672 | if (!all_zones_ok) { | |
1673 | cond_resched(); | |
1674 | goto loop_again; | |
1675 | } | |
1676 | ||
1677 | return total_reclaimed; | |
1678 | } | |
1679 | ||
1680 | /* | |
1681 | * The background pageout daemon, started as a kernel thread | |
1682 | * from the init process. | |
1683 | * | |
1684 | * This basically trickles out pages so that we have _some_ | |
1685 | * free memory available even if there is no other activity | |
1686 | * that frees anything up. This is needed for things like routing | |
1687 | * etc, where we otherwise might have all activity going on in | |
1688 | * asynchronous contexts that cannot page things out. | |
1689 | * | |
1690 | * If there are applications that are active memory-allocators | |
1691 | * (most normal use), this basically shouldn't matter. | |
1692 | */ | |
1693 | static int kswapd(void *p) | |
1694 | { | |
1695 | unsigned long order; | |
1696 | pg_data_t *pgdat = (pg_data_t*)p; | |
1697 | struct task_struct *tsk = current; | |
1698 | DEFINE_WAIT(wait); | |
1699 | struct reclaim_state reclaim_state = { | |
1700 | .reclaimed_slab = 0, | |
1701 | }; | |
1702 | cpumask_t cpumask; | |
1703 | ||
1704 | daemonize("kswapd%d", pgdat->node_id); | |
1705 | cpumask = node_to_cpumask(pgdat->node_id); | |
1706 | if (!cpus_empty(cpumask)) | |
1707 | set_cpus_allowed(tsk, cpumask); | |
1708 | current->reclaim_state = &reclaim_state; | |
1709 | ||
1710 | /* | |
1711 | * Tell the memory management that we're a "memory allocator", | |
1712 | * and that if we need more memory we should get access to it | |
1713 | * regardless (see "__alloc_pages()"). "kswapd" should | |
1714 | * never get caught in the normal page freeing logic. | |
1715 | * | |
1716 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
1717 | * you need a small amount of memory in order to be able to | |
1718 | * page out something else, and this flag essentially protects | |
1719 | * us from recursively trying to free more memory as we're | |
1720 | * trying to free the first piece of memory in the first place). | |
1721 | */ | |
930d9152 | 1722 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
1da177e4 LT |
1723 | |
1724 | order = 0; | |
1725 | for ( ; ; ) { | |
1726 | unsigned long new_order; | |
3e1d1d28 CL |
1727 | |
1728 | try_to_freeze(); | |
1da177e4 LT |
1729 | |
1730 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
1731 | new_order = pgdat->kswapd_max_order; | |
1732 | pgdat->kswapd_max_order = 0; | |
1733 | if (order < new_order) { | |
1734 | /* | |
1735 | * Don't sleep if someone wants a larger 'order' | |
1736 | * allocation | |
1737 | */ | |
1738 | order = new_order; | |
1739 | } else { | |
1740 | schedule(); | |
1741 | order = pgdat->kswapd_max_order; | |
1742 | } | |
1743 | finish_wait(&pgdat->kswapd_wait, &wait); | |
1744 | ||
1745 | balance_pgdat(pgdat, 0, order); | |
1746 | } | |
1747 | return 0; | |
1748 | } | |
1749 | ||
1750 | /* | |
1751 | * A zone is low on free memory, so wake its kswapd task to service it. | |
1752 | */ | |
1753 | void wakeup_kswapd(struct zone *zone, int order) | |
1754 | { | |
1755 | pg_data_t *pgdat; | |
1756 | ||
f3fe6512 | 1757 | if (!populated_zone(zone)) |
1da177e4 LT |
1758 | return; |
1759 | ||
1760 | pgdat = zone->zone_pgdat; | |
7fb1d9fc | 1761 | if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) |
1da177e4 LT |
1762 | return; |
1763 | if (pgdat->kswapd_max_order < order) | |
1764 | pgdat->kswapd_max_order = order; | |
9bf2229f | 1765 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 | 1766 | return; |
8d0986e2 | 1767 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
1da177e4 | 1768 | return; |
8d0986e2 | 1769 | wake_up_interruptible(&pgdat->kswapd_wait); |
1da177e4 LT |
1770 | } |
1771 | ||
1772 | #ifdef CONFIG_PM | |
1773 | /* | |
1774 | * Try to free `nr_pages' of memory, system-wide. Returns the number of freed | |
1775 | * pages. | |
1776 | */ | |
1777 | int shrink_all_memory(int nr_pages) | |
1778 | { | |
1779 | pg_data_t *pgdat; | |
1780 | int nr_to_free = nr_pages; | |
1781 | int ret = 0; | |
1782 | struct reclaim_state reclaim_state = { | |
1783 | .reclaimed_slab = 0, | |
1784 | }; | |
1785 | ||
1786 | current->reclaim_state = &reclaim_state; | |
1787 | for_each_pgdat(pgdat) { | |
1788 | int freed; | |
1789 | freed = balance_pgdat(pgdat, nr_to_free, 0); | |
1790 | ret += freed; | |
1791 | nr_to_free -= freed; | |
1792 | if (nr_to_free <= 0) | |
1793 | break; | |
1794 | } | |
1795 | current->reclaim_state = NULL; | |
1796 | return ret; | |
1797 | } | |
1798 | #endif | |
1799 | ||
1800 | #ifdef CONFIG_HOTPLUG_CPU | |
1801 | /* It's optimal to keep kswapds on the same CPUs as their memory, but | |
1802 | not required for correctness. So if the last cpu in a node goes | |
1803 | away, we get changed to run anywhere: as the first one comes back, | |
1804 | restore their cpu bindings. */ | |
1805 | static int __devinit cpu_callback(struct notifier_block *nfb, | |
1806 | unsigned long action, | |
1807 | void *hcpu) | |
1808 | { | |
1809 | pg_data_t *pgdat; | |
1810 | cpumask_t mask; | |
1811 | ||
1812 | if (action == CPU_ONLINE) { | |
1813 | for_each_pgdat(pgdat) { | |
1814 | mask = node_to_cpumask(pgdat->node_id); | |
1815 | if (any_online_cpu(mask) != NR_CPUS) | |
1816 | /* One of our CPUs online: restore mask */ | |
1817 | set_cpus_allowed(pgdat->kswapd, mask); | |
1818 | } | |
1819 | } | |
1820 | return NOTIFY_OK; | |
1821 | } | |
1822 | #endif /* CONFIG_HOTPLUG_CPU */ | |
1823 | ||
1824 | static int __init kswapd_init(void) | |
1825 | { | |
1826 | pg_data_t *pgdat; | |
1827 | swap_setup(); | |
1828 | for_each_pgdat(pgdat) | |
1829 | pgdat->kswapd | |
1830 | = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); | |
1831 | total_memory = nr_free_pagecache_pages(); | |
1832 | hotcpu_notifier(cpu_callback, 0); | |
1833 | return 0; | |
1834 | } | |
1835 | ||
1836 | module_init(kswapd_init) | |
9eeff239 CL |
1837 | |
1838 | #ifdef CONFIG_NUMA | |
1839 | /* | |
1840 | * Zone reclaim mode | |
1841 | * | |
1842 | * If non-zero call zone_reclaim when the number of free pages falls below | |
1843 | * the watermarks. | |
1844 | * | |
1845 | * In the future we may add flags to the mode. However, the page allocator | |
1846 | * should only have to check that zone_reclaim_mode != 0 before calling | |
1847 | * zone_reclaim(). | |
1848 | */ | |
1849 | int zone_reclaim_mode __read_mostly; | |
1850 | ||
1b2ffb78 CL |
1851 | #define RECLAIM_OFF 0 |
1852 | #define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */ | |
1853 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ | |
1854 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ | |
2a16e3f4 | 1855 | #define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */ |
1b2ffb78 | 1856 | |
9eeff239 CL |
1857 | /* |
1858 | * Mininum time between zone reclaim scans | |
1859 | */ | |
2a11ff06 | 1860 | int zone_reclaim_interval __read_mostly = 30*HZ; |
a92f7126 CL |
1861 | |
1862 | /* | |
1863 | * Priority for ZONE_RECLAIM. This determines the fraction of pages | |
1864 | * of a node considered for each zone_reclaim. 4 scans 1/16th of | |
1865 | * a zone. | |
1866 | */ | |
1867 | #define ZONE_RECLAIM_PRIORITY 4 | |
1868 | ||
9eeff239 CL |
1869 | /* |
1870 | * Try to free up some pages from this zone through reclaim. | |
1871 | */ | |
1872 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
1873 | { | |
89288623 | 1874 | int nr_pages; |
9eeff239 CL |
1875 | struct task_struct *p = current; |
1876 | struct reclaim_state reclaim_state; | |
89288623 | 1877 | struct scan_control sc; |
42c722d4 CL |
1878 | cpumask_t mask; |
1879 | int node_id; | |
8695949a | 1880 | int priority; |
89288623 CL |
1881 | |
1882 | if (time_before(jiffies, | |
2a11ff06 | 1883 | zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval)) |
89288623 | 1884 | return 0; |
9eeff239 CL |
1885 | |
1886 | if (!(gfp_mask & __GFP_WAIT) || | |
9eeff239 | 1887 | zone->all_unreclaimable || |
a6bf5270 CL |
1888 | atomic_read(&zone->reclaim_in_progress) > 0 || |
1889 | (p->flags & PF_MEMALLOC)) | |
9eeff239 CL |
1890 | return 0; |
1891 | ||
42c722d4 CL |
1892 | node_id = zone->zone_pgdat->node_id; |
1893 | mask = node_to_cpumask(node_id); | |
1894 | if (!cpus_empty(mask) && node_id != numa_node_id()) | |
1895 | return 0; | |
1896 | ||
1b2ffb78 CL |
1897 | sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE); |
1898 | sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP); | |
89288623 CL |
1899 | sc.nr_scanned = 0; |
1900 | sc.nr_reclaimed = 0; | |
89288623 CL |
1901 | sc.nr_mapped = read_page_state(nr_mapped); |
1902 | sc.gfp_mask = gfp_mask; | |
9eeff239 CL |
1903 | |
1904 | disable_swap_token(); | |
1905 | ||
89288623 | 1906 | nr_pages = 1 << order; |
9eeff239 CL |
1907 | if (nr_pages > SWAP_CLUSTER_MAX) |
1908 | sc.swap_cluster_max = nr_pages; | |
1909 | else | |
1910 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
1911 | ||
1912 | cond_resched(); | |
d4f7796e CL |
1913 | /* |
1914 | * We need to be able to allocate from the reserves for RECLAIM_SWAP | |
1915 | * and we also need to be able to write out pages for RECLAIM_WRITE | |
1916 | * and RECLAIM_SWAP. | |
1917 | */ | |
1918 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; | |
9eeff239 CL |
1919 | reclaim_state.reclaimed_slab = 0; |
1920 | p->reclaim_state = &reclaim_state; | |
c84db23c | 1921 | |
a92f7126 CL |
1922 | /* |
1923 | * Free memory by calling shrink zone with increasing priorities | |
1924 | * until we have enough memory freed. | |
1925 | */ | |
8695949a | 1926 | priority = ZONE_RECLAIM_PRIORITY; |
a92f7126 | 1927 | do { |
8695949a CL |
1928 | shrink_zone(priority, zone, &sc); |
1929 | priority--; | |
1930 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); | |
c84db23c | 1931 | |
2a16e3f4 CL |
1932 | if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) { |
1933 | /* | |
1934 | * shrink_slab does not currently allow us to determine | |
1935 | * how many pages were freed in the zone. So we just | |
1936 | * shake the slab and then go offnode for a single allocation. | |
1937 | * | |
1938 | * shrink_slab will free memory on all zones and may take | |
1939 | * a long time. | |
1940 | */ | |
1941 | shrink_slab(sc.nr_scanned, gfp_mask, order); | |
2a16e3f4 CL |
1942 | } |
1943 | ||
9eeff239 | 1944 | p->reclaim_state = NULL; |
d4f7796e | 1945 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
9eeff239 CL |
1946 | |
1947 | if (sc.nr_reclaimed == 0) | |
1948 | zone->last_unsuccessful_zone_reclaim = jiffies; | |
1949 | ||
c84db23c | 1950 | return sc.nr_reclaimed >= nr_pages; |
9eeff239 CL |
1951 | } |
1952 | #endif | |
1953 |