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1da177e4 LT |
1 | /* |
2 | * linux/mm/vmscan.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds | |
5 | * | |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. | |
7 | * kswapd added: 7.1.96 sct | |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed | |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. | |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). | |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. | |
12 | */ | |
13 | ||
14 | #include <linux/mm.h> | |
15 | #include <linux/module.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/kernel_stat.h> | |
18 | #include <linux/swap.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/highmem.h> | |
22 | #include <linux/file.h> | |
23 | #include <linux/writeback.h> | |
24 | #include <linux/blkdev.h> | |
25 | #include <linux/buffer_head.h> /* for try_to_release_page(), | |
26 | buffer_heads_over_limit */ | |
27 | #include <linux/mm_inline.h> | |
28 | #include <linux/pagevec.h> | |
29 | #include <linux/backing-dev.h> | |
30 | #include <linux/rmap.h> | |
31 | #include <linux/topology.h> | |
32 | #include <linux/cpu.h> | |
33 | #include <linux/cpuset.h> | |
34 | #include <linux/notifier.h> | |
35 | #include <linux/rwsem.h> | |
36 | ||
37 | #include <asm/tlbflush.h> | |
38 | #include <asm/div64.h> | |
39 | ||
40 | #include <linux/swapops.h> | |
41 | ||
42 | /* possible outcome of pageout() */ | |
43 | typedef enum { | |
44 | /* failed to write page out, page is locked */ | |
45 | PAGE_KEEP, | |
46 | /* move page to the active list, page is locked */ | |
47 | PAGE_ACTIVATE, | |
48 | /* page has been sent to the disk successfully, page is unlocked */ | |
49 | PAGE_SUCCESS, | |
50 | /* page is clean and locked */ | |
51 | PAGE_CLEAN, | |
52 | } pageout_t; | |
53 | ||
54 | struct scan_control { | |
55 | /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */ | |
56 | unsigned long nr_to_scan; | |
57 | ||
58 | /* Incremented by the number of inactive pages that were scanned */ | |
59 | unsigned long nr_scanned; | |
60 | ||
61 | /* Incremented by the number of pages reclaimed */ | |
62 | unsigned long nr_reclaimed; | |
63 | ||
64 | unsigned long nr_mapped; /* From page_state */ | |
65 | ||
1da177e4 LT |
66 | /* Ask shrink_caches, or shrink_zone to scan at this priority */ |
67 | unsigned int priority; | |
68 | ||
69 | /* This context's GFP mask */ | |
6daa0e28 | 70 | gfp_t gfp_mask; |
1da177e4 LT |
71 | |
72 | int may_writepage; | |
73 | ||
f1fd1067 CL |
74 | /* Can pages be swapped as part of reclaim? */ |
75 | int may_swap; | |
76 | ||
1da177e4 LT |
77 | /* This context's SWAP_CLUSTER_MAX. If freeing memory for |
78 | * suspend, we effectively ignore SWAP_CLUSTER_MAX. | |
79 | * In this context, it doesn't matter that we scan the | |
80 | * whole list at once. */ | |
81 | int swap_cluster_max; | |
82 | }; | |
83 | ||
84 | /* | |
85 | * The list of shrinker callbacks used by to apply pressure to | |
86 | * ageable caches. | |
87 | */ | |
88 | struct shrinker { | |
89 | shrinker_t shrinker; | |
90 | struct list_head list; | |
91 | int seeks; /* seeks to recreate an obj */ | |
92 | long nr; /* objs pending delete */ | |
93 | }; | |
94 | ||
95 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
96 | ||
97 | #ifdef ARCH_HAS_PREFETCH | |
98 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
99 | do { \ | |
100 | if ((_page)->lru.prev != _base) { \ | |
101 | struct page *prev; \ | |
102 | \ | |
103 | prev = lru_to_page(&(_page->lru)); \ | |
104 | prefetch(&prev->_field); \ | |
105 | } \ | |
106 | } while (0) | |
107 | #else | |
108 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
109 | #endif | |
110 | ||
111 | #ifdef ARCH_HAS_PREFETCHW | |
112 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
113 | do { \ | |
114 | if ((_page)->lru.prev != _base) { \ | |
115 | struct page *prev; \ | |
116 | \ | |
117 | prev = lru_to_page(&(_page->lru)); \ | |
118 | prefetchw(&prev->_field); \ | |
119 | } \ | |
120 | } while (0) | |
121 | #else | |
122 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
123 | #endif | |
124 | ||
125 | /* | |
126 | * From 0 .. 100. Higher means more swappy. | |
127 | */ | |
128 | int vm_swappiness = 60; | |
129 | static long total_memory; | |
130 | ||
131 | static LIST_HEAD(shrinker_list); | |
132 | static DECLARE_RWSEM(shrinker_rwsem); | |
133 | ||
134 | /* | |
135 | * Add a shrinker callback to be called from the vm | |
136 | */ | |
137 | struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) | |
138 | { | |
139 | struct shrinker *shrinker; | |
140 | ||
141 | shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); | |
142 | if (shrinker) { | |
143 | shrinker->shrinker = theshrinker; | |
144 | shrinker->seeks = seeks; | |
145 | shrinker->nr = 0; | |
146 | down_write(&shrinker_rwsem); | |
147 | list_add_tail(&shrinker->list, &shrinker_list); | |
148 | up_write(&shrinker_rwsem); | |
149 | } | |
150 | return shrinker; | |
151 | } | |
152 | EXPORT_SYMBOL(set_shrinker); | |
153 | ||
154 | /* | |
155 | * Remove one | |
156 | */ | |
157 | void remove_shrinker(struct shrinker *shrinker) | |
158 | { | |
159 | down_write(&shrinker_rwsem); | |
160 | list_del(&shrinker->list); | |
161 | up_write(&shrinker_rwsem); | |
162 | kfree(shrinker); | |
163 | } | |
164 | EXPORT_SYMBOL(remove_shrinker); | |
165 | ||
166 | #define SHRINK_BATCH 128 | |
167 | /* | |
168 | * Call the shrink functions to age shrinkable caches | |
169 | * | |
170 | * Here we assume it costs one seek to replace a lru page and that it also | |
171 | * takes a seek to recreate a cache object. With this in mind we age equal | |
172 | * percentages of the lru and ageable caches. This should balance the seeks | |
173 | * generated by these structures. | |
174 | * | |
175 | * If the vm encounted mapped pages on the LRU it increase the pressure on | |
176 | * slab to avoid swapping. | |
177 | * | |
178 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
179 | * | |
180 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
181 | * are eligible for the caller's allocation attempt. It is used for balancing | |
182 | * slab reclaim versus page reclaim. | |
b15e0905 | 183 | * |
184 | * Returns the number of slab objects which we shrunk. | |
1da177e4 | 185 | */ |
9d0243bc | 186 | int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages) |
1da177e4 LT |
187 | { |
188 | struct shrinker *shrinker; | |
b15e0905 | 189 | int ret = 0; |
1da177e4 LT |
190 | |
191 | if (scanned == 0) | |
192 | scanned = SWAP_CLUSTER_MAX; | |
193 | ||
194 | if (!down_read_trylock(&shrinker_rwsem)) | |
b15e0905 | 195 | return 1; /* Assume we'll be able to shrink next time */ |
1da177e4 LT |
196 | |
197 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
198 | unsigned long long delta; | |
199 | unsigned long total_scan; | |
ea164d73 | 200 | unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
201 | |
202 | delta = (4 * scanned) / shrinker->seeks; | |
ea164d73 | 203 | delta *= max_pass; |
1da177e4 LT |
204 | do_div(delta, lru_pages + 1); |
205 | shrinker->nr += delta; | |
ea164d73 AA |
206 | if (shrinker->nr < 0) { |
207 | printk(KERN_ERR "%s: nr=%ld\n", | |
208 | __FUNCTION__, shrinker->nr); | |
209 | shrinker->nr = max_pass; | |
210 | } | |
211 | ||
212 | /* | |
213 | * Avoid risking looping forever due to too large nr value: | |
214 | * never try to free more than twice the estimate number of | |
215 | * freeable entries. | |
216 | */ | |
217 | if (shrinker->nr > max_pass * 2) | |
218 | shrinker->nr = max_pass * 2; | |
1da177e4 LT |
219 | |
220 | total_scan = shrinker->nr; | |
221 | shrinker->nr = 0; | |
222 | ||
223 | while (total_scan >= SHRINK_BATCH) { | |
224 | long this_scan = SHRINK_BATCH; | |
225 | int shrink_ret; | |
b15e0905 | 226 | int nr_before; |
1da177e4 | 227 | |
b15e0905 | 228 | nr_before = (*shrinker->shrinker)(0, gfp_mask); |
1da177e4 LT |
229 | shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); |
230 | if (shrink_ret == -1) | |
231 | break; | |
b15e0905 | 232 | if (shrink_ret < nr_before) |
233 | ret += nr_before - shrink_ret; | |
1da177e4 LT |
234 | mod_page_state(slabs_scanned, this_scan); |
235 | total_scan -= this_scan; | |
236 | ||
237 | cond_resched(); | |
238 | } | |
239 | ||
240 | shrinker->nr += total_scan; | |
241 | } | |
242 | up_read(&shrinker_rwsem); | |
b15e0905 | 243 | return ret; |
1da177e4 LT |
244 | } |
245 | ||
246 | /* Called without lock on whether page is mapped, so answer is unstable */ | |
247 | static inline int page_mapping_inuse(struct page *page) | |
248 | { | |
249 | struct address_space *mapping; | |
250 | ||
251 | /* Page is in somebody's page tables. */ | |
252 | if (page_mapped(page)) | |
253 | return 1; | |
254 | ||
255 | /* Be more reluctant to reclaim swapcache than pagecache */ | |
256 | if (PageSwapCache(page)) | |
257 | return 1; | |
258 | ||
259 | mapping = page_mapping(page); | |
260 | if (!mapping) | |
261 | return 0; | |
262 | ||
263 | /* File is mmap'd by somebody? */ | |
264 | return mapping_mapped(mapping); | |
265 | } | |
266 | ||
267 | static inline int is_page_cache_freeable(struct page *page) | |
268 | { | |
269 | return page_count(page) - !!PagePrivate(page) == 2; | |
270 | } | |
271 | ||
272 | static int may_write_to_queue(struct backing_dev_info *bdi) | |
273 | { | |
930d9152 | 274 | if (current->flags & PF_SWAPWRITE) |
1da177e4 LT |
275 | return 1; |
276 | if (!bdi_write_congested(bdi)) | |
277 | return 1; | |
278 | if (bdi == current->backing_dev_info) | |
279 | return 1; | |
280 | return 0; | |
281 | } | |
282 | ||
283 | /* | |
284 | * We detected a synchronous write error writing a page out. Probably | |
285 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
286 | * fsync(), msync() or close(). | |
287 | * | |
288 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
289 | * prevents it from being freed up. But we have a ref on the page and once | |
290 | * that page is locked, the mapping is pinned. | |
291 | * | |
292 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
293 | * __GFP_FS. | |
294 | */ | |
295 | static void handle_write_error(struct address_space *mapping, | |
296 | struct page *page, int error) | |
297 | { | |
298 | lock_page(page); | |
299 | if (page_mapping(page) == mapping) { | |
300 | if (error == -ENOSPC) | |
301 | set_bit(AS_ENOSPC, &mapping->flags); | |
302 | else | |
303 | set_bit(AS_EIO, &mapping->flags); | |
304 | } | |
305 | unlock_page(page); | |
306 | } | |
307 | ||
308 | /* | |
309 | * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). | |
310 | */ | |
311 | static pageout_t pageout(struct page *page, struct address_space *mapping) | |
312 | { | |
313 | /* | |
314 | * If the page is dirty, only perform writeback if that write | |
315 | * will be non-blocking. To prevent this allocation from being | |
316 | * stalled by pagecache activity. But note that there may be | |
317 | * stalls if we need to run get_block(). We could test | |
318 | * PagePrivate for that. | |
319 | * | |
320 | * If this process is currently in generic_file_write() against | |
321 | * this page's queue, we can perform writeback even if that | |
322 | * will block. | |
323 | * | |
324 | * If the page is swapcache, write it back even if that would | |
325 | * block, for some throttling. This happens by accident, because | |
326 | * swap_backing_dev_info is bust: it doesn't reflect the | |
327 | * congestion state of the swapdevs. Easy to fix, if needed. | |
328 | * See swapfile.c:page_queue_congested(). | |
329 | */ | |
330 | if (!is_page_cache_freeable(page)) | |
331 | return PAGE_KEEP; | |
332 | if (!mapping) { | |
333 | /* | |
334 | * Some data journaling orphaned pages can have | |
335 | * page->mapping == NULL while being dirty with clean buffers. | |
336 | */ | |
323aca6c | 337 | if (PagePrivate(page)) { |
1da177e4 LT |
338 | if (try_to_free_buffers(page)) { |
339 | ClearPageDirty(page); | |
340 | printk("%s: orphaned page\n", __FUNCTION__); | |
341 | return PAGE_CLEAN; | |
342 | } | |
343 | } | |
344 | return PAGE_KEEP; | |
345 | } | |
346 | if (mapping->a_ops->writepage == NULL) | |
347 | return PAGE_ACTIVATE; | |
348 | if (!may_write_to_queue(mapping->backing_dev_info)) | |
349 | return PAGE_KEEP; | |
350 | ||
351 | if (clear_page_dirty_for_io(page)) { | |
352 | int res; | |
353 | struct writeback_control wbc = { | |
354 | .sync_mode = WB_SYNC_NONE, | |
355 | .nr_to_write = SWAP_CLUSTER_MAX, | |
356 | .nonblocking = 1, | |
357 | .for_reclaim = 1, | |
358 | }; | |
359 | ||
360 | SetPageReclaim(page); | |
361 | res = mapping->a_ops->writepage(page, &wbc); | |
362 | if (res < 0) | |
363 | handle_write_error(mapping, page, res); | |
994fc28c | 364 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
1da177e4 LT |
365 | ClearPageReclaim(page); |
366 | return PAGE_ACTIVATE; | |
367 | } | |
368 | if (!PageWriteback(page)) { | |
369 | /* synchronous write or broken a_ops? */ | |
370 | ClearPageReclaim(page); | |
371 | } | |
372 | ||
373 | return PAGE_SUCCESS; | |
374 | } | |
375 | ||
376 | return PAGE_CLEAN; | |
377 | } | |
378 | ||
49d2e9cc CL |
379 | static int remove_mapping(struct address_space *mapping, struct page *page) |
380 | { | |
381 | if (!mapping) | |
382 | return 0; /* truncate got there first */ | |
383 | ||
384 | write_lock_irq(&mapping->tree_lock); | |
385 | ||
386 | /* | |
387 | * The non-racy check for busy page. It is critical to check | |
388 | * PageDirty _after_ making sure that the page is freeable and | |
389 | * not in use by anybody. (pagecache + us == 2) | |
390 | */ | |
391 | if (unlikely(page_count(page) != 2)) | |
392 | goto cannot_free; | |
393 | smp_rmb(); | |
394 | if (unlikely(PageDirty(page))) | |
395 | goto cannot_free; | |
396 | ||
397 | if (PageSwapCache(page)) { | |
398 | swp_entry_t swap = { .val = page_private(page) }; | |
399 | __delete_from_swap_cache(page); | |
400 | write_unlock_irq(&mapping->tree_lock); | |
401 | swap_free(swap); | |
402 | __put_page(page); /* The pagecache ref */ | |
403 | return 1; | |
404 | } | |
405 | ||
406 | __remove_from_page_cache(page); | |
407 | write_unlock_irq(&mapping->tree_lock); | |
408 | __put_page(page); | |
409 | return 1; | |
410 | ||
411 | cannot_free: | |
412 | write_unlock_irq(&mapping->tree_lock); | |
413 | return 0; | |
414 | } | |
415 | ||
1da177e4 LT |
416 | /* |
417 | * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed | |
418 | */ | |
419 | static int shrink_list(struct list_head *page_list, struct scan_control *sc) | |
420 | { | |
421 | LIST_HEAD(ret_pages); | |
422 | struct pagevec freed_pvec; | |
423 | int pgactivate = 0; | |
424 | int reclaimed = 0; | |
425 | ||
426 | cond_resched(); | |
427 | ||
428 | pagevec_init(&freed_pvec, 1); | |
429 | while (!list_empty(page_list)) { | |
430 | struct address_space *mapping; | |
431 | struct page *page; | |
432 | int may_enter_fs; | |
433 | int referenced; | |
434 | ||
435 | cond_resched(); | |
436 | ||
437 | page = lru_to_page(page_list); | |
438 | list_del(&page->lru); | |
439 | ||
440 | if (TestSetPageLocked(page)) | |
441 | goto keep; | |
442 | ||
443 | BUG_ON(PageActive(page)); | |
444 | ||
445 | sc->nr_scanned++; | |
446 | /* Double the slab pressure for mapped and swapcache pages */ | |
447 | if (page_mapped(page) || PageSwapCache(page)) | |
448 | sc->nr_scanned++; | |
449 | ||
450 | if (PageWriteback(page)) | |
451 | goto keep_locked; | |
452 | ||
f7b7fd8f | 453 | referenced = page_referenced(page, 1); |
1da177e4 LT |
454 | /* In active use or really unfreeable? Activate it. */ |
455 | if (referenced && page_mapping_inuse(page)) | |
456 | goto activate_locked; | |
457 | ||
458 | #ifdef CONFIG_SWAP | |
459 | /* | |
460 | * Anonymous process memory has backing store? | |
461 | * Try to allocate it some swap space here. | |
462 | */ | |
c340010e | 463 | if (PageAnon(page) && !PageSwapCache(page)) { |
f1fd1067 CL |
464 | if (!sc->may_swap) |
465 | goto keep_locked; | |
1480a540 | 466 | if (!add_to_swap(page, GFP_ATOMIC)) |
1da177e4 LT |
467 | goto activate_locked; |
468 | } | |
469 | #endif /* CONFIG_SWAP */ | |
470 | ||
471 | mapping = page_mapping(page); | |
472 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || | |
473 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
474 | ||
475 | /* | |
476 | * The page is mapped into the page tables of one or more | |
477 | * processes. Try to unmap it here. | |
478 | */ | |
479 | if (page_mapped(page) && mapping) { | |
aa3f18b3 CL |
480 | /* |
481 | * No unmapping if we do not swap | |
482 | */ | |
483 | if (!sc->may_swap) | |
484 | goto keep_locked; | |
485 | ||
a48d07af | 486 | switch (try_to_unmap(page, 0)) { |
1da177e4 LT |
487 | case SWAP_FAIL: |
488 | goto activate_locked; | |
489 | case SWAP_AGAIN: | |
490 | goto keep_locked; | |
491 | case SWAP_SUCCESS: | |
492 | ; /* try to free the page below */ | |
493 | } | |
494 | } | |
495 | ||
496 | if (PageDirty(page)) { | |
497 | if (referenced) | |
498 | goto keep_locked; | |
499 | if (!may_enter_fs) | |
500 | goto keep_locked; | |
52a8363e | 501 | if (!sc->may_writepage) |
1da177e4 LT |
502 | goto keep_locked; |
503 | ||
504 | /* Page is dirty, try to write it out here */ | |
505 | switch(pageout(page, mapping)) { | |
506 | case PAGE_KEEP: | |
507 | goto keep_locked; | |
508 | case PAGE_ACTIVATE: | |
509 | goto activate_locked; | |
510 | case PAGE_SUCCESS: | |
511 | if (PageWriteback(page) || PageDirty(page)) | |
512 | goto keep; | |
513 | /* | |
514 | * A synchronous write - probably a ramdisk. Go | |
515 | * ahead and try to reclaim the page. | |
516 | */ | |
517 | if (TestSetPageLocked(page)) | |
518 | goto keep; | |
519 | if (PageDirty(page) || PageWriteback(page)) | |
520 | goto keep_locked; | |
521 | mapping = page_mapping(page); | |
522 | case PAGE_CLEAN: | |
523 | ; /* try to free the page below */ | |
524 | } | |
525 | } | |
526 | ||
527 | /* | |
528 | * If the page has buffers, try to free the buffer mappings | |
529 | * associated with this page. If we succeed we try to free | |
530 | * the page as well. | |
531 | * | |
532 | * We do this even if the page is PageDirty(). | |
533 | * try_to_release_page() does not perform I/O, but it is | |
534 | * possible for a page to have PageDirty set, but it is actually | |
535 | * clean (all its buffers are clean). This happens if the | |
536 | * buffers were written out directly, with submit_bh(). ext3 | |
537 | * will do this, as well as the blockdev mapping. | |
538 | * try_to_release_page() will discover that cleanness and will | |
539 | * drop the buffers and mark the page clean - it can be freed. | |
540 | * | |
541 | * Rarely, pages can have buffers and no ->mapping. These are | |
542 | * the pages which were not successfully invalidated in | |
543 | * truncate_complete_page(). We try to drop those buffers here | |
544 | * and if that worked, and the page is no longer mapped into | |
545 | * process address space (page_count == 1) it can be freed. | |
546 | * Otherwise, leave the page on the LRU so it is swappable. | |
547 | */ | |
548 | if (PagePrivate(page)) { | |
549 | if (!try_to_release_page(page, sc->gfp_mask)) | |
550 | goto activate_locked; | |
551 | if (!mapping && page_count(page) == 1) | |
552 | goto free_it; | |
553 | } | |
554 | ||
49d2e9cc CL |
555 | if (!remove_mapping(mapping, page)) |
556 | goto keep_locked; | |
1da177e4 LT |
557 | |
558 | free_it: | |
559 | unlock_page(page); | |
560 | reclaimed++; | |
561 | if (!pagevec_add(&freed_pvec, page)) | |
562 | __pagevec_release_nonlru(&freed_pvec); | |
563 | continue; | |
564 | ||
565 | activate_locked: | |
566 | SetPageActive(page); | |
567 | pgactivate++; | |
568 | keep_locked: | |
569 | unlock_page(page); | |
570 | keep: | |
571 | list_add(&page->lru, &ret_pages); | |
572 | BUG_ON(PageLRU(page)); | |
573 | } | |
574 | list_splice(&ret_pages, page_list); | |
575 | if (pagevec_count(&freed_pvec)) | |
576 | __pagevec_release_nonlru(&freed_pvec); | |
577 | mod_page_state(pgactivate, pgactivate); | |
578 | sc->nr_reclaimed += reclaimed; | |
579 | return reclaimed; | |
580 | } | |
581 | ||
7cbe34cf | 582 | #ifdef CONFIG_MIGRATION |
8419c318 CL |
583 | static inline void move_to_lru(struct page *page) |
584 | { | |
585 | list_del(&page->lru); | |
586 | if (PageActive(page)) { | |
587 | /* | |
588 | * lru_cache_add_active checks that | |
589 | * the PG_active bit is off. | |
590 | */ | |
591 | ClearPageActive(page); | |
592 | lru_cache_add_active(page); | |
593 | } else { | |
594 | lru_cache_add(page); | |
595 | } | |
596 | put_page(page); | |
597 | } | |
598 | ||
599 | /* | |
053837fc | 600 | * Add isolated pages on the list back to the LRU. |
8419c318 CL |
601 | * |
602 | * returns the number of pages put back. | |
603 | */ | |
604 | int putback_lru_pages(struct list_head *l) | |
605 | { | |
606 | struct page *page; | |
607 | struct page *page2; | |
608 | int count = 0; | |
609 | ||
610 | list_for_each_entry_safe(page, page2, l, lru) { | |
611 | move_to_lru(page); | |
612 | count++; | |
613 | } | |
614 | return count; | |
615 | } | |
616 | ||
e965f963 CL |
617 | /* |
618 | * Non migratable page | |
619 | */ | |
620 | int fail_migrate_page(struct page *newpage, struct page *page) | |
621 | { | |
622 | return -EIO; | |
623 | } | |
624 | EXPORT_SYMBOL(fail_migrate_page); | |
625 | ||
49d2e9cc CL |
626 | /* |
627 | * swapout a single page | |
628 | * page is locked upon entry, unlocked on exit | |
49d2e9cc CL |
629 | */ |
630 | static int swap_page(struct page *page) | |
631 | { | |
632 | struct address_space *mapping = page_mapping(page); | |
633 | ||
634 | if (page_mapped(page) && mapping) | |
a48d07af | 635 | if (try_to_unmap(page, 0) != SWAP_SUCCESS) |
49d2e9cc CL |
636 | goto unlock_retry; |
637 | ||
638 | if (PageDirty(page)) { | |
639 | /* Page is dirty, try to write it out here */ | |
640 | switch(pageout(page, mapping)) { | |
641 | case PAGE_KEEP: | |
642 | case PAGE_ACTIVATE: | |
643 | goto unlock_retry; | |
644 | ||
645 | case PAGE_SUCCESS: | |
646 | goto retry; | |
647 | ||
648 | case PAGE_CLEAN: | |
649 | ; /* try to free the page below */ | |
650 | } | |
651 | } | |
652 | ||
653 | if (PagePrivate(page)) { | |
654 | if (!try_to_release_page(page, GFP_KERNEL) || | |
655 | (!mapping && page_count(page) == 1)) | |
656 | goto unlock_retry; | |
657 | } | |
658 | ||
659 | if (remove_mapping(mapping, page)) { | |
660 | /* Success */ | |
661 | unlock_page(page); | |
662 | return 0; | |
663 | } | |
664 | ||
665 | unlock_retry: | |
666 | unlock_page(page); | |
667 | ||
668 | retry: | |
d0d96328 | 669 | return -EAGAIN; |
49d2e9cc | 670 | } |
e965f963 | 671 | EXPORT_SYMBOL(swap_page); |
a48d07af CL |
672 | |
673 | /* | |
674 | * Page migration was first developed in the context of the memory hotplug | |
675 | * project. The main authors of the migration code are: | |
676 | * | |
677 | * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> | |
678 | * Hirokazu Takahashi <taka@valinux.co.jp> | |
679 | * Dave Hansen <haveblue@us.ibm.com> | |
680 | * Christoph Lameter <clameter@sgi.com> | |
681 | */ | |
682 | ||
683 | /* | |
684 | * Remove references for a page and establish the new page with the correct | |
685 | * basic settings to be able to stop accesses to the page. | |
686 | */ | |
e965f963 | 687 | int migrate_page_remove_references(struct page *newpage, |
a48d07af CL |
688 | struct page *page, int nr_refs) |
689 | { | |
690 | struct address_space *mapping = page_mapping(page); | |
691 | struct page **radix_pointer; | |
692 | ||
693 | /* | |
694 | * Avoid doing any of the following work if the page count | |
695 | * indicates that the page is in use or truncate has removed | |
696 | * the page. | |
697 | */ | |
698 | if (!mapping || page_mapcount(page) + nr_refs != page_count(page)) | |
699 | return 1; | |
700 | ||
701 | /* | |
702 | * Establish swap ptes for anonymous pages or destroy pte | |
703 | * maps for files. | |
704 | * | |
705 | * In order to reestablish file backed mappings the fault handlers | |
706 | * will take the radix tree_lock which may then be used to stop | |
707 | * processses from accessing this page until the new page is ready. | |
708 | * | |
709 | * A process accessing via a swap pte (an anonymous page) will take a | |
710 | * page_lock on the old page which will block the process until the | |
711 | * migration attempt is complete. At that time the PageSwapCache bit | |
712 | * will be examined. If the page was migrated then the PageSwapCache | |
713 | * bit will be clear and the operation to retrieve the page will be | |
714 | * retried which will find the new page in the radix tree. Then a new | |
715 | * direct mapping may be generated based on the radix tree contents. | |
716 | * | |
717 | * If the page was not migrated then the PageSwapCache bit | |
718 | * is still set and the operation may continue. | |
719 | */ | |
720 | try_to_unmap(page, 1); | |
721 | ||
722 | /* | |
723 | * Give up if we were unable to remove all mappings. | |
724 | */ | |
725 | if (page_mapcount(page)) | |
726 | return 1; | |
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); | |
737 | return 1; | |
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 | { | |
812 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ | |
813 | ||
814 | if (migrate_page_remove_references(newpage, page, 2)) | |
815 | return -EAGAIN; | |
816 | ||
817 | migrate_page_copy(newpage, page); | |
818 | ||
a3351e52 CL |
819 | /* |
820 | * Remove auxiliary swap entries and replace | |
821 | * them with real ptes. | |
822 | * | |
823 | * Note that a real pte entry will allow processes that are not | |
824 | * waiting on the page lock to use the new page via the page tables | |
825 | * before the new page is unlocked. | |
826 | */ | |
827 | remove_from_swap(newpage); | |
a48d07af CL |
828 | return 0; |
829 | } | |
e965f963 | 830 | EXPORT_SYMBOL(migrate_page); |
a48d07af | 831 | |
49d2e9cc CL |
832 | /* |
833 | * migrate_pages | |
834 | * | |
835 | * Two lists are passed to this function. The first list | |
836 | * contains the pages isolated from the LRU to be migrated. | |
837 | * The second list contains new pages that the pages isolated | |
838 | * can be moved to. If the second list is NULL then all | |
839 | * pages are swapped out. | |
840 | * | |
841 | * The function returns after 10 attempts or if no pages | |
842 | * are movable anymore because t has become empty | |
843 | * or no retryable pages exist anymore. | |
844 | * | |
d0d96328 | 845 | * Return: Number of pages not migrated when "to" ran empty. |
49d2e9cc | 846 | */ |
d4984711 CL |
847 | int migrate_pages(struct list_head *from, struct list_head *to, |
848 | struct list_head *moved, struct list_head *failed) | |
49d2e9cc CL |
849 | { |
850 | int retry; | |
49d2e9cc CL |
851 | int nr_failed = 0; |
852 | int pass = 0; | |
853 | struct page *page; | |
854 | struct page *page2; | |
855 | int swapwrite = current->flags & PF_SWAPWRITE; | |
d0d96328 | 856 | int rc; |
49d2e9cc CL |
857 | |
858 | if (!swapwrite) | |
859 | current->flags |= PF_SWAPWRITE; | |
860 | ||
861 | redo: | |
862 | retry = 0; | |
863 | ||
d4984711 | 864 | list_for_each_entry_safe(page, page2, from, lru) { |
a48d07af CL |
865 | struct page *newpage = NULL; |
866 | struct address_space *mapping; | |
867 | ||
49d2e9cc CL |
868 | cond_resched(); |
869 | ||
d0d96328 CL |
870 | rc = 0; |
871 | if (page_count(page) == 1) | |
ee27497d | 872 | /* page was freed from under us. So we are done. */ |
d0d96328 CL |
873 | goto next; |
874 | ||
a48d07af CL |
875 | if (to && list_empty(to)) |
876 | break; | |
877 | ||
49d2e9cc CL |
878 | /* |
879 | * Skip locked pages during the first two passes to give the | |
7cbe34cf CL |
880 | * functions holding the lock time to release the page. Later we |
881 | * use lock_page() to have a higher chance of acquiring the | |
882 | * lock. | |
49d2e9cc | 883 | */ |
d0d96328 | 884 | rc = -EAGAIN; |
49d2e9cc CL |
885 | if (pass > 2) |
886 | lock_page(page); | |
887 | else | |
888 | if (TestSetPageLocked(page)) | |
d0d96328 | 889 | goto next; |
49d2e9cc CL |
890 | |
891 | /* | |
892 | * Only wait on writeback if we have already done a pass where | |
893 | * we we may have triggered writeouts for lots of pages. | |
894 | */ | |
7cbe34cf | 895 | if (pass > 0) { |
49d2e9cc | 896 | wait_on_page_writeback(page); |
7cbe34cf | 897 | } else { |
d0d96328 CL |
898 | if (PageWriteback(page)) |
899 | goto unlock_page; | |
7cbe34cf | 900 | } |
49d2e9cc | 901 | |
d0d96328 CL |
902 | /* |
903 | * Anonymous pages must have swap cache references otherwise | |
904 | * the information contained in the page maps cannot be | |
905 | * preserved. | |
906 | */ | |
49d2e9cc | 907 | if (PageAnon(page) && !PageSwapCache(page)) { |
1480a540 | 908 | if (!add_to_swap(page, GFP_KERNEL)) { |
d0d96328 CL |
909 | rc = -ENOMEM; |
910 | goto unlock_page; | |
49d2e9cc CL |
911 | } |
912 | } | |
49d2e9cc | 913 | |
a48d07af CL |
914 | if (!to) { |
915 | rc = swap_page(page); | |
916 | goto next; | |
917 | } | |
918 | ||
919 | newpage = lru_to_page(to); | |
920 | lock_page(newpage); | |
921 | ||
49d2e9cc | 922 | /* |
a48d07af | 923 | * Pages are properly locked and writeback is complete. |
49d2e9cc CL |
924 | * Try to migrate the page. |
925 | */ | |
a48d07af CL |
926 | mapping = page_mapping(page); |
927 | if (!mapping) | |
928 | goto unlock_both; | |
929 | ||
e965f963 CL |
930 | if (mapping->a_ops->migratepage) { |
931 | rc = mapping->a_ops->migratepage(newpage, page); | |
932 | goto unlock_both; | |
933 | } | |
934 | ||
a48d07af CL |
935 | /* |
936 | * Trigger writeout if page is dirty | |
937 | */ | |
938 | if (PageDirty(page)) { | |
939 | switch (pageout(page, mapping)) { | |
940 | case PAGE_KEEP: | |
941 | case PAGE_ACTIVATE: | |
942 | goto unlock_both; | |
943 | ||
944 | case PAGE_SUCCESS: | |
945 | unlock_page(newpage); | |
946 | goto next; | |
947 | ||
948 | case PAGE_CLEAN: | |
949 | ; /* try to migrate the page below */ | |
950 | } | |
951 | } | |
952 | /* | |
953 | * If we have no buffer or can release the buffer | |
954 | * then do a simple migration. | |
955 | */ | |
956 | if (!page_has_buffers(page) || | |
957 | try_to_release_page(page, GFP_KERNEL)) { | |
958 | rc = migrate_page(newpage, page); | |
959 | goto unlock_both; | |
960 | } | |
961 | ||
962 | /* | |
963 | * On early passes with mapped pages simply | |
964 | * retry. There may be a lock held for some | |
965 | * buffers that may go away. Later | |
966 | * swap them out. | |
967 | */ | |
968 | if (pass > 4) { | |
969 | unlock_page(newpage); | |
970 | newpage = NULL; | |
971 | rc = swap_page(page); | |
972 | goto next; | |
973 | } | |
974 | ||
975 | unlock_both: | |
976 | unlock_page(newpage); | |
d0d96328 CL |
977 | |
978 | unlock_page: | |
979 | unlock_page(page); | |
980 | ||
981 | next: | |
982 | if (rc == -EAGAIN) { | |
983 | retry++; | |
984 | } else if (rc) { | |
985 | /* Permanent failure */ | |
986 | list_move(&page->lru, failed); | |
987 | nr_failed++; | |
988 | } else { | |
a48d07af CL |
989 | if (newpage) { |
990 | /* Successful migration. Return page to LRU */ | |
991 | move_to_lru(newpage); | |
992 | } | |
d4984711 | 993 | list_move(&page->lru, moved); |
d4984711 | 994 | } |
49d2e9cc CL |
995 | } |
996 | if (retry && pass++ < 10) | |
997 | goto redo; | |
998 | ||
999 | if (!swapwrite) | |
1000 | current->flags &= ~PF_SWAPWRITE; | |
1001 | ||
49d2e9cc CL |
1002 | return nr_failed + retry; |
1003 | } | |
8419c318 | 1004 | |
8419c318 CL |
1005 | /* |
1006 | * Isolate one page from the LRU lists and put it on the | |
053837fc | 1007 | * indicated list with elevated refcount. |
8419c318 CL |
1008 | * |
1009 | * Result: | |
1010 | * 0 = page not on LRU list | |
1011 | * 1 = page removed from LRU list and added to the specified list. | |
8419c318 CL |
1012 | */ |
1013 | int isolate_lru_page(struct page *page) | |
1014 | { | |
053837fc | 1015 | int ret = 0; |
8419c318 | 1016 | |
053837fc NP |
1017 | if (PageLRU(page)) { |
1018 | struct zone *zone = page_zone(page); | |
1019 | spin_lock_irq(&zone->lru_lock); | |
1020 | if (TestClearPageLRU(page)) { | |
1021 | ret = 1; | |
1022 | get_page(page); | |
1023 | if (PageActive(page)) | |
1024 | del_page_from_active_list(zone, page); | |
1025 | else | |
1026 | del_page_from_inactive_list(zone, page); | |
1027 | } | |
1028 | spin_unlock_irq(&zone->lru_lock); | |
8419c318 | 1029 | } |
053837fc NP |
1030 | |
1031 | return ret; | |
8419c318 | 1032 | } |
7cbe34cf | 1033 | #endif |
49d2e9cc | 1034 | |
1da177e4 LT |
1035 | /* |
1036 | * zone->lru_lock is heavily contended. Some of the functions that | |
1037 | * shrink the lists perform better by taking out a batch of pages | |
1038 | * and working on them outside the LRU lock. | |
1039 | * | |
1040 | * For pagecache intensive workloads, this function is the hottest | |
1041 | * spot in the kernel (apart from copy_*_user functions). | |
1042 | * | |
1043 | * Appropriate locks must be held before calling this function. | |
1044 | * | |
1045 | * @nr_to_scan: The number of pages to look through on the list. | |
1046 | * @src: The LRU list to pull pages off. | |
1047 | * @dst: The temp list to put pages on to. | |
1048 | * @scanned: The number of pages that were scanned. | |
1049 | * | |
1050 | * returns how many pages were moved onto *@dst. | |
1051 | */ | |
1052 | static int isolate_lru_pages(int nr_to_scan, struct list_head *src, | |
1053 | struct list_head *dst, int *scanned) | |
1054 | { | |
1055 | int nr_taken = 0; | |
1056 | struct page *page; | |
1057 | int scan = 0; | |
1058 | ||
1059 | while (scan++ < nr_to_scan && !list_empty(src)) { | |
1060 | page = lru_to_page(src); | |
1061 | prefetchw_prev_lru_page(page, src, flags); | |
1062 | ||
053837fc | 1063 | if (!TestClearPageLRU(page)) |
21eac81f | 1064 | BUG(); |
053837fc NP |
1065 | list_del(&page->lru); |
1066 | if (get_page_testone(page)) { | |
1067 | /* | |
1068 | * It is being freed elsewhere | |
1069 | */ | |
1070 | __put_page(page); | |
1071 | SetPageLRU(page); | |
1072 | list_add(&page->lru, src); | |
1073 | continue; | |
1074 | } else { | |
1075 | list_add(&page->lru, dst); | |
1076 | nr_taken++; | |
1da177e4 LT |
1077 | } |
1078 | } | |
1079 | ||
1080 | *scanned = scan; | |
1081 | return nr_taken; | |
1082 | } | |
1083 | ||
1084 | /* | |
1085 | * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed | |
1086 | */ | |
1087 | static void shrink_cache(struct zone *zone, struct scan_control *sc) | |
1088 | { | |
1089 | LIST_HEAD(page_list); | |
1090 | struct pagevec pvec; | |
1091 | int max_scan = sc->nr_to_scan; | |
1092 | ||
1093 | pagevec_init(&pvec, 1); | |
1094 | ||
1095 | lru_add_drain(); | |
1096 | spin_lock_irq(&zone->lru_lock); | |
1097 | while (max_scan > 0) { | |
1098 | struct page *page; | |
1099 | int nr_taken; | |
1100 | int nr_scan; | |
1101 | int nr_freed; | |
1102 | ||
1103 | nr_taken = isolate_lru_pages(sc->swap_cluster_max, | |
1104 | &zone->inactive_list, | |
1105 | &page_list, &nr_scan); | |
1106 | zone->nr_inactive -= nr_taken; | |
1107 | zone->pages_scanned += nr_scan; | |
1108 | spin_unlock_irq(&zone->lru_lock); | |
1109 | ||
1110 | if (nr_taken == 0) | |
1111 | goto done; | |
1112 | ||
1113 | max_scan -= nr_scan; | |
1da177e4 | 1114 | nr_freed = shrink_list(&page_list, sc); |
1da177e4 | 1115 | |
a74609fa NP |
1116 | local_irq_disable(); |
1117 | if (current_is_kswapd()) { | |
1118 | __mod_page_state_zone(zone, pgscan_kswapd, nr_scan); | |
1119 | __mod_page_state(kswapd_steal, nr_freed); | |
1120 | } else | |
1121 | __mod_page_state_zone(zone, pgscan_direct, nr_scan); | |
1122 | __mod_page_state_zone(zone, pgsteal, nr_freed); | |
1123 | ||
1124 | spin_lock(&zone->lru_lock); | |
1da177e4 LT |
1125 | /* |
1126 | * Put back any unfreeable pages. | |
1127 | */ | |
1128 | while (!list_empty(&page_list)) { | |
1129 | page = lru_to_page(&page_list); | |
1130 | if (TestSetPageLRU(page)) | |
1131 | BUG(); | |
1132 | list_del(&page->lru); | |
1133 | if (PageActive(page)) | |
1134 | add_page_to_active_list(zone, page); | |
1135 | else | |
1136 | add_page_to_inactive_list(zone, page); | |
1137 | if (!pagevec_add(&pvec, page)) { | |
1138 | spin_unlock_irq(&zone->lru_lock); | |
1139 | __pagevec_release(&pvec); | |
1140 | spin_lock_irq(&zone->lru_lock); | |
1141 | } | |
1142 | } | |
1143 | } | |
1144 | spin_unlock_irq(&zone->lru_lock); | |
1145 | done: | |
1146 | pagevec_release(&pvec); | |
1147 | } | |
1148 | ||
1149 | /* | |
1150 | * This moves pages from the active list to the inactive list. | |
1151 | * | |
1152 | * We move them the other way if the page is referenced by one or more | |
1153 | * processes, from rmap. | |
1154 | * | |
1155 | * If the pages are mostly unmapped, the processing is fast and it is | |
1156 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
1157 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
1158 | * should drop zone->lru_lock around each page. It's impossible to balance | |
1159 | * this, so instead we remove the pages from the LRU while processing them. | |
1160 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
1161 | * nobody will play with that bit on a non-LRU page. | |
1162 | * | |
1163 | * The downside is that we have to touch page->_count against each page. | |
1164 | * But we had to alter page->flags anyway. | |
1165 | */ | |
1166 | static void | |
1167 | refill_inactive_zone(struct zone *zone, struct scan_control *sc) | |
1168 | { | |
1169 | int pgmoved; | |
1170 | int pgdeactivate = 0; | |
1171 | int pgscanned; | |
1172 | int nr_pages = sc->nr_to_scan; | |
1173 | LIST_HEAD(l_hold); /* The pages which were snipped off */ | |
1174 | LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ | |
1175 | LIST_HEAD(l_active); /* Pages to go onto the active_list */ | |
1176 | struct page *page; | |
1177 | struct pagevec pvec; | |
1178 | int reclaim_mapped = 0; | |
1179 | long mapped_ratio; | |
1180 | long distress; | |
1181 | long swap_tendency; | |
1182 | ||
1183 | lru_add_drain(); | |
1184 | spin_lock_irq(&zone->lru_lock); | |
1185 | pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, | |
1186 | &l_hold, &pgscanned); | |
1187 | zone->pages_scanned += pgscanned; | |
1188 | zone->nr_active -= pgmoved; | |
1189 | spin_unlock_irq(&zone->lru_lock); | |
1190 | ||
1191 | /* | |
1192 | * `distress' is a measure of how much trouble we're having reclaiming | |
1193 | * pages. 0 -> no problems. 100 -> great trouble. | |
1194 | */ | |
1195 | distress = 100 >> zone->prev_priority; | |
1196 | ||
1197 | /* | |
1198 | * The point of this algorithm is to decide when to start reclaiming | |
1199 | * mapped memory instead of just pagecache. Work out how much memory | |
1200 | * is mapped. | |
1201 | */ | |
1202 | mapped_ratio = (sc->nr_mapped * 100) / total_memory; | |
1203 | ||
1204 | /* | |
1205 | * Now decide how much we really want to unmap some pages. The mapped | |
1206 | * ratio is downgraded - just because there's a lot of mapped memory | |
1207 | * doesn't necessarily mean that page reclaim isn't succeeding. | |
1208 | * | |
1209 | * The distress ratio is important - we don't want to start going oom. | |
1210 | * | |
1211 | * A 100% value of vm_swappiness overrides this algorithm altogether. | |
1212 | */ | |
1213 | swap_tendency = mapped_ratio / 2 + distress + vm_swappiness; | |
1214 | ||
1215 | /* | |
1216 | * Now use this metric to decide whether to start moving mapped memory | |
1217 | * onto the inactive list. | |
1218 | */ | |
1219 | if (swap_tendency >= 100) | |
1220 | reclaim_mapped = 1; | |
1221 | ||
1222 | while (!list_empty(&l_hold)) { | |
1223 | cond_resched(); | |
1224 | page = lru_to_page(&l_hold); | |
1225 | list_del(&page->lru); | |
1226 | if (page_mapped(page)) { | |
1227 | if (!reclaim_mapped || | |
1228 | (total_swap_pages == 0 && PageAnon(page)) || | |
f7b7fd8f | 1229 | page_referenced(page, 0)) { |
1da177e4 LT |
1230 | list_add(&page->lru, &l_active); |
1231 | continue; | |
1232 | } | |
1233 | } | |
1234 | list_add(&page->lru, &l_inactive); | |
1235 | } | |
1236 | ||
1237 | pagevec_init(&pvec, 1); | |
1238 | pgmoved = 0; | |
1239 | spin_lock_irq(&zone->lru_lock); | |
1240 | while (!list_empty(&l_inactive)) { | |
1241 | page = lru_to_page(&l_inactive); | |
1242 | prefetchw_prev_lru_page(page, &l_inactive, flags); | |
1243 | if (TestSetPageLRU(page)) | |
1244 | BUG(); | |
1245 | if (!TestClearPageActive(page)) | |
1246 | BUG(); | |
1247 | list_move(&page->lru, &zone->inactive_list); | |
1248 | pgmoved++; | |
1249 | if (!pagevec_add(&pvec, page)) { | |
1250 | zone->nr_inactive += pgmoved; | |
1251 | spin_unlock_irq(&zone->lru_lock); | |
1252 | pgdeactivate += pgmoved; | |
1253 | pgmoved = 0; | |
1254 | if (buffer_heads_over_limit) | |
1255 | pagevec_strip(&pvec); | |
1256 | __pagevec_release(&pvec); | |
1257 | spin_lock_irq(&zone->lru_lock); | |
1258 | } | |
1259 | } | |
1260 | zone->nr_inactive += pgmoved; | |
1261 | pgdeactivate += pgmoved; | |
1262 | if (buffer_heads_over_limit) { | |
1263 | spin_unlock_irq(&zone->lru_lock); | |
1264 | pagevec_strip(&pvec); | |
1265 | spin_lock_irq(&zone->lru_lock); | |
1266 | } | |
1267 | ||
1268 | pgmoved = 0; | |
1269 | while (!list_empty(&l_active)) { | |
1270 | page = lru_to_page(&l_active); | |
1271 | prefetchw_prev_lru_page(page, &l_active, flags); | |
1272 | if (TestSetPageLRU(page)) | |
1273 | BUG(); | |
1274 | BUG_ON(!PageActive(page)); | |
1275 | list_move(&page->lru, &zone->active_list); | |
1276 | pgmoved++; | |
1277 | if (!pagevec_add(&pvec, page)) { | |
1278 | zone->nr_active += pgmoved; | |
1279 | pgmoved = 0; | |
1280 | spin_unlock_irq(&zone->lru_lock); | |
1281 | __pagevec_release(&pvec); | |
1282 | spin_lock_irq(&zone->lru_lock); | |
1283 | } | |
1284 | } | |
1285 | zone->nr_active += pgmoved; | |
a74609fa NP |
1286 | spin_unlock(&zone->lru_lock); |
1287 | ||
1288 | __mod_page_state_zone(zone, pgrefill, pgscanned); | |
1289 | __mod_page_state(pgdeactivate, pgdeactivate); | |
1290 | local_irq_enable(); | |
1da177e4 | 1291 | |
a74609fa | 1292 | pagevec_release(&pvec); |
1da177e4 LT |
1293 | } |
1294 | ||
1295 | /* | |
1296 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
1297 | */ | |
1298 | static void | |
1299 | shrink_zone(struct zone *zone, struct scan_control *sc) | |
1300 | { | |
1301 | unsigned long nr_active; | |
1302 | unsigned long nr_inactive; | |
1303 | ||
53e9a615 MH |
1304 | atomic_inc(&zone->reclaim_in_progress); |
1305 | ||
1da177e4 LT |
1306 | /* |
1307 | * Add one to `nr_to_scan' just to make sure that the kernel will | |
1308 | * slowly sift through the active list. | |
1309 | */ | |
1310 | zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1; | |
1311 | nr_active = zone->nr_scan_active; | |
1312 | if (nr_active >= sc->swap_cluster_max) | |
1313 | zone->nr_scan_active = 0; | |
1314 | else | |
1315 | nr_active = 0; | |
1316 | ||
1317 | zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1; | |
1318 | nr_inactive = zone->nr_scan_inactive; | |
1319 | if (nr_inactive >= sc->swap_cluster_max) | |
1320 | zone->nr_scan_inactive = 0; | |
1321 | else | |
1322 | nr_inactive = 0; | |
1323 | ||
1da177e4 LT |
1324 | while (nr_active || nr_inactive) { |
1325 | if (nr_active) { | |
1326 | sc->nr_to_scan = min(nr_active, | |
1327 | (unsigned long)sc->swap_cluster_max); | |
1328 | nr_active -= sc->nr_to_scan; | |
1329 | refill_inactive_zone(zone, sc); | |
1330 | } | |
1331 | ||
1332 | if (nr_inactive) { | |
1333 | sc->nr_to_scan = min(nr_inactive, | |
1334 | (unsigned long)sc->swap_cluster_max); | |
1335 | nr_inactive -= sc->nr_to_scan; | |
1336 | shrink_cache(zone, sc); | |
1da177e4 LT |
1337 | } |
1338 | } | |
1339 | ||
1340 | throttle_vm_writeout(); | |
53e9a615 MH |
1341 | |
1342 | atomic_dec(&zone->reclaim_in_progress); | |
1da177e4 LT |
1343 | } |
1344 | ||
1345 | /* | |
1346 | * This is the direct reclaim path, for page-allocating processes. We only | |
1347 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
1348 | * request. | |
1349 | * | |
1350 | * We reclaim from a zone even if that zone is over pages_high. Because: | |
1351 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order | |
1352 | * allocation or | |
1353 | * b) The zones may be over pages_high but they must go *over* pages_high to | |
1354 | * satisfy the `incremental min' zone defense algorithm. | |
1355 | * | |
1356 | * Returns the number of reclaimed pages. | |
1357 | * | |
1358 | * If a zone is deemed to be full of pinned pages then just give it a light | |
1359 | * scan then give up on it. | |
1360 | */ | |
1361 | static void | |
1362 | shrink_caches(struct zone **zones, struct scan_control *sc) | |
1363 | { | |
1364 | int i; | |
1365 | ||
1366 | for (i = 0; zones[i] != NULL; i++) { | |
1367 | struct zone *zone = zones[i]; | |
1368 | ||
f3fe6512 | 1369 | if (!populated_zone(zone)) |
1da177e4 LT |
1370 | continue; |
1371 | ||
9bf2229f | 1372 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1373 | continue; |
1374 | ||
1375 | zone->temp_priority = sc->priority; | |
1376 | if (zone->prev_priority > sc->priority) | |
1377 | zone->prev_priority = sc->priority; | |
1378 | ||
1379 | if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY) | |
1380 | continue; /* Let kswapd poll it */ | |
1381 | ||
1382 | shrink_zone(zone, sc); | |
1383 | } | |
1384 | } | |
1385 | ||
1386 | /* | |
1387 | * This is the main entry point to direct page reclaim. | |
1388 | * | |
1389 | * If a full scan of the inactive list fails to free enough memory then we | |
1390 | * are "out of memory" and something needs to be killed. | |
1391 | * | |
1392 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
1393 | * high - the zone may be full of dirty or under-writeback pages, which this | |
1394 | * caller can't do much about. We kick pdflush and take explicit naps in the | |
1395 | * hope that some of these pages can be written. But if the allocating task | |
1396 | * holds filesystem locks which prevent writeout this might not work, and the | |
1397 | * allocation attempt will fail. | |
1398 | */ | |
6daa0e28 | 1399 | int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) |
1da177e4 LT |
1400 | { |
1401 | int priority; | |
1402 | int ret = 0; | |
1403 | int total_scanned = 0, total_reclaimed = 0; | |
1404 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1405 | struct scan_control sc; | |
1406 | unsigned long lru_pages = 0; | |
1407 | int i; | |
1408 | ||
1409 | sc.gfp_mask = gfp_mask; | |
52a8363e | 1410 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1411 | sc.may_swap = 1; |
1da177e4 LT |
1412 | |
1413 | inc_page_state(allocstall); | |
1414 | ||
1415 | for (i = 0; zones[i] != NULL; i++) { | |
1416 | struct zone *zone = zones[i]; | |
1417 | ||
9bf2229f | 1418 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1419 | continue; |
1420 | ||
1421 | zone->temp_priority = DEF_PRIORITY; | |
1422 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1423 | } | |
1424 | ||
1425 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1426 | sc.nr_mapped = read_page_state(nr_mapped); | |
1427 | sc.nr_scanned = 0; | |
1428 | sc.nr_reclaimed = 0; | |
1429 | sc.priority = priority; | |
1430 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
f7b7fd8f RR |
1431 | if (!priority) |
1432 | disable_swap_token(); | |
1da177e4 LT |
1433 | shrink_caches(zones, &sc); |
1434 | shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); | |
1435 | if (reclaim_state) { | |
1436 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; | |
1437 | reclaim_state->reclaimed_slab = 0; | |
1438 | } | |
1439 | total_scanned += sc.nr_scanned; | |
1440 | total_reclaimed += sc.nr_reclaimed; | |
1441 | if (total_reclaimed >= sc.swap_cluster_max) { | |
1442 | ret = 1; | |
1443 | goto out; | |
1444 | } | |
1445 | ||
1446 | /* | |
1447 | * Try to write back as many pages as we just scanned. This | |
1448 | * tends to cause slow streaming writers to write data to the | |
1449 | * disk smoothly, at the dirtying rate, which is nice. But | |
1450 | * that's undesirable in laptop mode, where we *want* lumpy | |
1451 | * writeout. So in laptop mode, write out the whole world. | |
1452 | */ | |
1453 | if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) { | |
687a21ce | 1454 | wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
1da177e4 LT |
1455 | sc.may_writepage = 1; |
1456 | } | |
1457 | ||
1458 | /* Take a nap, wait for some writeback to complete */ | |
1459 | if (sc.nr_scanned && priority < DEF_PRIORITY - 2) | |
1460 | blk_congestion_wait(WRITE, HZ/10); | |
1461 | } | |
1462 | out: | |
1463 | for (i = 0; zones[i] != 0; i++) { | |
1464 | struct zone *zone = zones[i]; | |
1465 | ||
9bf2229f | 1466 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 LT |
1467 | continue; |
1468 | ||
1469 | zone->prev_priority = zone->temp_priority; | |
1470 | } | |
1471 | return ret; | |
1472 | } | |
1473 | ||
1474 | /* | |
1475 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
1476 | * they are all at pages_high. | |
1477 | * | |
1478 | * If `nr_pages' is non-zero then it is the number of pages which are to be | |
1479 | * reclaimed, regardless of the zone occupancies. This is a software suspend | |
1480 | * special. | |
1481 | * | |
1482 | * Returns the number of pages which were actually freed. | |
1483 | * | |
1484 | * There is special handling here for zones which are full of pinned pages. | |
1485 | * This can happen if the pages are all mlocked, or if they are all used by | |
1486 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
1487 | * What we do is to detect the case where all pages in the zone have been | |
1488 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
1489 | * dead and from now on, only perform a short scan. Basically we're polling | |
1490 | * the zone for when the problem goes away. | |
1491 | * | |
1492 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
1493 | * zones which have free_pages > pages_high, but once a zone is found to have | |
1494 | * free_pages <= pages_high, we scan that zone and the lower zones regardless | |
1495 | * of the number of free pages in the lower zones. This interoperates with | |
1496 | * the page allocator fallback scheme to ensure that aging of pages is balanced | |
1497 | * across the zones. | |
1498 | */ | |
1499 | static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) | |
1500 | { | |
1501 | int to_free = nr_pages; | |
1502 | int all_zones_ok; | |
1503 | int priority; | |
1504 | int i; | |
1505 | int total_scanned, total_reclaimed; | |
1506 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1507 | struct scan_control sc; | |
1508 | ||
1509 | loop_again: | |
1510 | total_scanned = 0; | |
1511 | total_reclaimed = 0; | |
1512 | sc.gfp_mask = GFP_KERNEL; | |
52a8363e | 1513 | sc.may_writepage = !laptop_mode; |
f1fd1067 | 1514 | sc.may_swap = 1; |
1da177e4 LT |
1515 | sc.nr_mapped = read_page_state(nr_mapped); |
1516 | ||
1517 | inc_page_state(pageoutrun); | |
1518 | ||
1519 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1520 | struct zone *zone = pgdat->node_zones + i; | |
1521 | ||
1522 | zone->temp_priority = DEF_PRIORITY; | |
1523 | } | |
1524 | ||
1525 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1526 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ | |
1527 | unsigned long lru_pages = 0; | |
1528 | ||
f7b7fd8f RR |
1529 | /* The swap token gets in the way of swapout... */ |
1530 | if (!priority) | |
1531 | disable_swap_token(); | |
1532 | ||
1da177e4 LT |
1533 | all_zones_ok = 1; |
1534 | ||
1535 | if (nr_pages == 0) { | |
1536 | /* | |
1537 | * Scan in the highmem->dma direction for the highest | |
1538 | * zone which needs scanning | |
1539 | */ | |
1540 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
1541 | struct zone *zone = pgdat->node_zones + i; | |
1542 | ||
f3fe6512 | 1543 | if (!populated_zone(zone)) |
1da177e4 LT |
1544 | continue; |
1545 | ||
1546 | if (zone->all_unreclaimable && | |
1547 | priority != DEF_PRIORITY) | |
1548 | continue; | |
1549 | ||
1550 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1551 | zone->pages_high, 0, 0)) { |
1da177e4 LT |
1552 | end_zone = i; |
1553 | goto scan; | |
1554 | } | |
1555 | } | |
1556 | goto out; | |
1557 | } else { | |
1558 | end_zone = pgdat->nr_zones - 1; | |
1559 | } | |
1560 | scan: | |
1561 | for (i = 0; i <= end_zone; i++) { | |
1562 | struct zone *zone = pgdat->node_zones + i; | |
1563 | ||
1564 | lru_pages += zone->nr_active + zone->nr_inactive; | |
1565 | } | |
1566 | ||
1567 | /* | |
1568 | * Now scan the zone in the dma->highmem direction, stopping | |
1569 | * at the last zone which needs scanning. | |
1570 | * | |
1571 | * We do this because the page allocator works in the opposite | |
1572 | * direction. This prevents the page allocator from allocating | |
1573 | * pages behind kswapd's direction of progress, which would | |
1574 | * cause too much scanning of the lower zones. | |
1575 | */ | |
1576 | for (i = 0; i <= end_zone; i++) { | |
1577 | struct zone *zone = pgdat->node_zones + i; | |
b15e0905 | 1578 | int nr_slab; |
1da177e4 | 1579 | |
f3fe6512 | 1580 | if (!populated_zone(zone)) |
1da177e4 LT |
1581 | continue; |
1582 | ||
1583 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) | |
1584 | continue; | |
1585 | ||
1586 | if (nr_pages == 0) { /* Not software suspend */ | |
1587 | if (!zone_watermark_ok(zone, order, | |
7fb1d9fc | 1588 | zone->pages_high, end_zone, 0)) |
1da177e4 LT |
1589 | all_zones_ok = 0; |
1590 | } | |
1591 | zone->temp_priority = priority; | |
1592 | if (zone->prev_priority > priority) | |
1593 | zone->prev_priority = priority; | |
1594 | sc.nr_scanned = 0; | |
1595 | sc.nr_reclaimed = 0; | |
1596 | sc.priority = priority; | |
1597 | sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; | |
1e7e5a90 | 1598 | atomic_inc(&zone->reclaim_in_progress); |
1da177e4 | 1599 | shrink_zone(zone, &sc); |
1e7e5a90 | 1600 | atomic_dec(&zone->reclaim_in_progress); |
1da177e4 | 1601 | reclaim_state->reclaimed_slab = 0; |
b15e0905 | 1602 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
1603 | lru_pages); | |
1da177e4 LT |
1604 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
1605 | total_reclaimed += sc.nr_reclaimed; | |
1606 | total_scanned += sc.nr_scanned; | |
1607 | if (zone->all_unreclaimable) | |
1608 | continue; | |
b15e0905 | 1609 | if (nr_slab == 0 && zone->pages_scanned >= |
1610 | (zone->nr_active + zone->nr_inactive) * 4) | |
1da177e4 LT |
1611 | zone->all_unreclaimable = 1; |
1612 | /* | |
1613 | * If we've done a decent amount of scanning and | |
1614 | * the reclaim ratio is low, start doing writepage | |
1615 | * even in laptop mode | |
1616 | */ | |
1617 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && | |
1618 | total_scanned > total_reclaimed+total_reclaimed/2) | |
1619 | sc.may_writepage = 1; | |
1620 | } | |
1621 | if (nr_pages && to_free > total_reclaimed) | |
1622 | continue; /* swsusp: need to do more work */ | |
1623 | if (all_zones_ok) | |
1624 | break; /* kswapd: all done */ | |
1625 | /* | |
1626 | * OK, kswapd is getting into trouble. Take a nap, then take | |
1627 | * another pass across the zones. | |
1628 | */ | |
1629 | if (total_scanned && priority < DEF_PRIORITY - 2) | |
1630 | blk_congestion_wait(WRITE, HZ/10); | |
1631 | ||
1632 | /* | |
1633 | * We do this so kswapd doesn't build up large priorities for | |
1634 | * example when it is freeing in parallel with allocators. It | |
1635 | * matches the direct reclaim path behaviour in terms of impact | |
1636 | * on zone->*_priority. | |
1637 | */ | |
1638 | if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) | |
1639 | break; | |
1640 | } | |
1641 | out: | |
1642 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1643 | struct zone *zone = pgdat->node_zones + i; | |
1644 | ||
1645 | zone->prev_priority = zone->temp_priority; | |
1646 | } | |
1647 | if (!all_zones_ok) { | |
1648 | cond_resched(); | |
1649 | goto loop_again; | |
1650 | } | |
1651 | ||
1652 | return total_reclaimed; | |
1653 | } | |
1654 | ||
1655 | /* | |
1656 | * The background pageout daemon, started as a kernel thread | |
1657 | * from the init process. | |
1658 | * | |
1659 | * This basically trickles out pages so that we have _some_ | |
1660 | * free memory available even if there is no other activity | |
1661 | * that frees anything up. This is needed for things like routing | |
1662 | * etc, where we otherwise might have all activity going on in | |
1663 | * asynchronous contexts that cannot page things out. | |
1664 | * | |
1665 | * If there are applications that are active memory-allocators | |
1666 | * (most normal use), this basically shouldn't matter. | |
1667 | */ | |
1668 | static int kswapd(void *p) | |
1669 | { | |
1670 | unsigned long order; | |
1671 | pg_data_t *pgdat = (pg_data_t*)p; | |
1672 | struct task_struct *tsk = current; | |
1673 | DEFINE_WAIT(wait); | |
1674 | struct reclaim_state reclaim_state = { | |
1675 | .reclaimed_slab = 0, | |
1676 | }; | |
1677 | cpumask_t cpumask; | |
1678 | ||
1679 | daemonize("kswapd%d", pgdat->node_id); | |
1680 | cpumask = node_to_cpumask(pgdat->node_id); | |
1681 | if (!cpus_empty(cpumask)) | |
1682 | set_cpus_allowed(tsk, cpumask); | |
1683 | current->reclaim_state = &reclaim_state; | |
1684 | ||
1685 | /* | |
1686 | * Tell the memory management that we're a "memory allocator", | |
1687 | * and that if we need more memory we should get access to it | |
1688 | * regardless (see "__alloc_pages()"). "kswapd" should | |
1689 | * never get caught in the normal page freeing logic. | |
1690 | * | |
1691 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
1692 | * you need a small amount of memory in order to be able to | |
1693 | * page out something else, and this flag essentially protects | |
1694 | * us from recursively trying to free more memory as we're | |
1695 | * trying to free the first piece of memory in the first place). | |
1696 | */ | |
930d9152 | 1697 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
1da177e4 LT |
1698 | |
1699 | order = 0; | |
1700 | for ( ; ; ) { | |
1701 | unsigned long new_order; | |
3e1d1d28 CL |
1702 | |
1703 | try_to_freeze(); | |
1da177e4 LT |
1704 | |
1705 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
1706 | new_order = pgdat->kswapd_max_order; | |
1707 | pgdat->kswapd_max_order = 0; | |
1708 | if (order < new_order) { | |
1709 | /* | |
1710 | * Don't sleep if someone wants a larger 'order' | |
1711 | * allocation | |
1712 | */ | |
1713 | order = new_order; | |
1714 | } else { | |
1715 | schedule(); | |
1716 | order = pgdat->kswapd_max_order; | |
1717 | } | |
1718 | finish_wait(&pgdat->kswapd_wait, &wait); | |
1719 | ||
1720 | balance_pgdat(pgdat, 0, order); | |
1721 | } | |
1722 | return 0; | |
1723 | } | |
1724 | ||
1725 | /* | |
1726 | * A zone is low on free memory, so wake its kswapd task to service it. | |
1727 | */ | |
1728 | void wakeup_kswapd(struct zone *zone, int order) | |
1729 | { | |
1730 | pg_data_t *pgdat; | |
1731 | ||
f3fe6512 | 1732 | if (!populated_zone(zone)) |
1da177e4 LT |
1733 | return; |
1734 | ||
1735 | pgdat = zone->zone_pgdat; | |
7fb1d9fc | 1736 | if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0)) |
1da177e4 LT |
1737 | return; |
1738 | if (pgdat->kswapd_max_order < order) | |
1739 | pgdat->kswapd_max_order = order; | |
9bf2229f | 1740 | if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
1da177e4 | 1741 | return; |
8d0986e2 | 1742 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
1da177e4 | 1743 | return; |
8d0986e2 | 1744 | wake_up_interruptible(&pgdat->kswapd_wait); |
1da177e4 LT |
1745 | } |
1746 | ||
1747 | #ifdef CONFIG_PM | |
1748 | /* | |
1749 | * Try to free `nr_pages' of memory, system-wide. Returns the number of freed | |
1750 | * pages. | |
1751 | */ | |
1752 | int shrink_all_memory(int nr_pages) | |
1753 | { | |
1754 | pg_data_t *pgdat; | |
1755 | int nr_to_free = nr_pages; | |
1756 | int ret = 0; | |
1757 | struct reclaim_state reclaim_state = { | |
1758 | .reclaimed_slab = 0, | |
1759 | }; | |
1760 | ||
1761 | current->reclaim_state = &reclaim_state; | |
1762 | for_each_pgdat(pgdat) { | |
1763 | int freed; | |
1764 | freed = balance_pgdat(pgdat, nr_to_free, 0); | |
1765 | ret += freed; | |
1766 | nr_to_free -= freed; | |
1767 | if (nr_to_free <= 0) | |
1768 | break; | |
1769 | } | |
1770 | current->reclaim_state = NULL; | |
1771 | return ret; | |
1772 | } | |
1773 | #endif | |
1774 | ||
1775 | #ifdef CONFIG_HOTPLUG_CPU | |
1776 | /* It's optimal to keep kswapds on the same CPUs as their memory, but | |
1777 | not required for correctness. So if the last cpu in a node goes | |
1778 | away, we get changed to run anywhere: as the first one comes back, | |
1779 | restore their cpu bindings. */ | |
1780 | static int __devinit cpu_callback(struct notifier_block *nfb, | |
1781 | unsigned long action, | |
1782 | void *hcpu) | |
1783 | { | |
1784 | pg_data_t *pgdat; | |
1785 | cpumask_t mask; | |
1786 | ||
1787 | if (action == CPU_ONLINE) { | |
1788 | for_each_pgdat(pgdat) { | |
1789 | mask = node_to_cpumask(pgdat->node_id); | |
1790 | if (any_online_cpu(mask) != NR_CPUS) | |
1791 | /* One of our CPUs online: restore mask */ | |
1792 | set_cpus_allowed(pgdat->kswapd, mask); | |
1793 | } | |
1794 | } | |
1795 | return NOTIFY_OK; | |
1796 | } | |
1797 | #endif /* CONFIG_HOTPLUG_CPU */ | |
1798 | ||
1799 | static int __init kswapd_init(void) | |
1800 | { | |
1801 | pg_data_t *pgdat; | |
1802 | swap_setup(); | |
1803 | for_each_pgdat(pgdat) | |
1804 | pgdat->kswapd | |
1805 | = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); | |
1806 | total_memory = nr_free_pagecache_pages(); | |
1807 | hotcpu_notifier(cpu_callback, 0); | |
1808 | return 0; | |
1809 | } | |
1810 | ||
1811 | module_init(kswapd_init) | |
9eeff239 CL |
1812 | |
1813 | #ifdef CONFIG_NUMA | |
1814 | /* | |
1815 | * Zone reclaim mode | |
1816 | * | |
1817 | * If non-zero call zone_reclaim when the number of free pages falls below | |
1818 | * the watermarks. | |
1819 | * | |
1820 | * In the future we may add flags to the mode. However, the page allocator | |
1821 | * should only have to check that zone_reclaim_mode != 0 before calling | |
1822 | * zone_reclaim(). | |
1823 | */ | |
1824 | int zone_reclaim_mode __read_mostly; | |
1825 | ||
1b2ffb78 CL |
1826 | #define RECLAIM_OFF 0 |
1827 | #define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */ | |
1828 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ | |
1829 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ | |
2a16e3f4 | 1830 | #define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */ |
1b2ffb78 | 1831 | |
9eeff239 CL |
1832 | /* |
1833 | * Mininum time between zone reclaim scans | |
1834 | */ | |
2a11ff06 | 1835 | int zone_reclaim_interval __read_mostly = 30*HZ; |
a92f7126 CL |
1836 | |
1837 | /* | |
1838 | * Priority for ZONE_RECLAIM. This determines the fraction of pages | |
1839 | * of a node considered for each zone_reclaim. 4 scans 1/16th of | |
1840 | * a zone. | |
1841 | */ | |
1842 | #define ZONE_RECLAIM_PRIORITY 4 | |
1843 | ||
9eeff239 CL |
1844 | /* |
1845 | * Try to free up some pages from this zone through reclaim. | |
1846 | */ | |
1847 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
1848 | { | |
89288623 | 1849 | int nr_pages; |
9eeff239 CL |
1850 | struct task_struct *p = current; |
1851 | struct reclaim_state reclaim_state; | |
89288623 | 1852 | struct scan_control sc; |
42c722d4 CL |
1853 | cpumask_t mask; |
1854 | int node_id; | |
89288623 CL |
1855 | |
1856 | if (time_before(jiffies, | |
2a11ff06 | 1857 | zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval)) |
89288623 | 1858 | return 0; |
9eeff239 CL |
1859 | |
1860 | if (!(gfp_mask & __GFP_WAIT) || | |
9eeff239 CL |
1861 | zone->all_unreclaimable || |
1862 | atomic_read(&zone->reclaim_in_progress) > 0) | |
1863 | return 0; | |
1864 | ||
42c722d4 CL |
1865 | node_id = zone->zone_pgdat->node_id; |
1866 | mask = node_to_cpumask(node_id); | |
1867 | if (!cpus_empty(mask) && node_id != numa_node_id()) | |
1868 | return 0; | |
1869 | ||
1b2ffb78 CL |
1870 | sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE); |
1871 | sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP); | |
89288623 CL |
1872 | sc.nr_scanned = 0; |
1873 | sc.nr_reclaimed = 0; | |
a92f7126 | 1874 | sc.priority = ZONE_RECLAIM_PRIORITY + 1; |
89288623 CL |
1875 | sc.nr_mapped = read_page_state(nr_mapped); |
1876 | sc.gfp_mask = gfp_mask; | |
9eeff239 CL |
1877 | |
1878 | disable_swap_token(); | |
1879 | ||
89288623 | 1880 | nr_pages = 1 << order; |
9eeff239 CL |
1881 | if (nr_pages > SWAP_CLUSTER_MAX) |
1882 | sc.swap_cluster_max = nr_pages; | |
1883 | else | |
1884 | sc.swap_cluster_max = SWAP_CLUSTER_MAX; | |
1885 | ||
1886 | cond_resched(); | |
1887 | p->flags |= PF_MEMALLOC; | |
1888 | reclaim_state.reclaimed_slab = 0; | |
1889 | p->reclaim_state = &reclaim_state; | |
c84db23c | 1890 | |
a92f7126 CL |
1891 | /* |
1892 | * Free memory by calling shrink zone with increasing priorities | |
1893 | * until we have enough memory freed. | |
1894 | */ | |
1895 | do { | |
1896 | sc.priority--; | |
1897 | shrink_zone(zone, &sc); | |
1898 | ||
1899 | } while (sc.nr_reclaimed < nr_pages && sc.priority > 0); | |
c84db23c | 1900 | |
2a16e3f4 CL |
1901 | if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) { |
1902 | /* | |
1903 | * shrink_slab does not currently allow us to determine | |
1904 | * how many pages were freed in the zone. So we just | |
1905 | * shake the slab and then go offnode for a single allocation. | |
1906 | * | |
1907 | * shrink_slab will free memory on all zones and may take | |
1908 | * a long time. | |
1909 | */ | |
1910 | shrink_slab(sc.nr_scanned, gfp_mask, order); | |
1911 | sc.nr_reclaimed = 1; /* Avoid getting the off node timeout */ | |
1912 | } | |
1913 | ||
9eeff239 CL |
1914 | p->reclaim_state = NULL; |
1915 | current->flags &= ~PF_MEMALLOC; | |
1916 | ||
1917 | if (sc.nr_reclaimed == 0) | |
1918 | zone->last_unsuccessful_zone_reclaim = jiffies; | |
1919 | ||
c84db23c | 1920 | return sc.nr_reclaimed >= nr_pages; |
9eeff239 CL |
1921 | } |
1922 | #endif | |
1923 |