blob: 2e34b61a70c727afc2895529c1997a1a8d399eee [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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() */
43typedef 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
54struct 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 /* Ask shrink_caches, or shrink_zone to scan at this priority */
67 unsigned int priority;
68
69 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040070 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
72 int may_writepage;
73
Christoph Lameterf1fd1062006-01-18 17:42:30 -080074 /* Can pages be swapped as part of reclaim? */
75 int may_swap;
76
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 /* 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 */
88struct 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 */
128int vm_swappiness = 60;
129static long total_memory;
130
131static LIST_HEAD(shrinker_list);
132static DECLARE_RWSEM(shrinker_rwsem);
133
134/*
135 * Add a shrinker callback to be called from the vm
136 */
137struct 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}
152EXPORT_SYMBOL(set_shrinker);
153
154/*
155 * Remove one
156 */
157void 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}
164EXPORT_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.
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700183 *
184 * Returns the number of slab objects which we shrunk.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 */
Andrew Morton9d0243b2006-01-08 01:00:39 -0800186int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187{
188 struct shrinker *shrinker;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700189 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190
191 if (scanned == 0)
192 scanned = SWAP_CLUSTER_MAX;
193
194 if (!down_read_trylock(&shrinker_rwsem))
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700195 return 1; /* Assume we'll be able to shrink next time */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196
197 list_for_each_entry(shrinker, &shrinker_list, list) {
198 unsigned long long delta;
199 unsigned long total_scan;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800200 unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201
202 delta = (4 * scanned) / shrinker->seeks;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800203 delta *= max_pass;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 do_div(delta, lru_pages + 1);
205 shrinker->nr += delta;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800206 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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219
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;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700226 int nr_before;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700228 nr_before = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
230 if (shrink_ret == -1)
231 break;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700232 if (shrink_ret < nr_before)
233 ret += nr_before - shrink_ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234 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);
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700243 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244}
245
246/* Called without lock on whether page is mapped, so answer is unstable */
247static 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
267static inline int is_page_cache_freeable(struct page *page)
268{
269 return page_count(page) - !!PagePrivate(page) == 2;
270}
271
272static int may_write_to_queue(struct backing_dev_info *bdi)
273{
Christoph Lameter930d9152006-01-08 01:00:47 -0800274 if (current->flags & PF_SWAPWRITE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275 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 */
295static 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 */
311static 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 */
akpm@osdl.org323aca62005-04-16 15:24:06 -0700337 if (PagePrivate(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 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);
Zach Brown994fc28c2005-12-15 14:28:17 -0800364 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 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
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800379static 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
411cannot_free:
412 write_unlock_irq(&mapping->tree_lock);
413 return 0;
414}
415
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416/*
417 * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
418 */
419static 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
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800453 referenced = page_referenced(page, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 /* 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 */
Lee Schermerhornc3400102005-10-29 18:15:51 -0700463 if (PageAnon(page) && !PageSwapCache(page)) {
Christoph Lameterf1fd1062006-01-18 17:42:30 -0800464 if (!sc->may_swap)
465 goto keep_locked;
Christoph Lameter1480a542006-01-08 01:00:53 -0800466 if (!add_to_swap(page, GFP_ATOMIC))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467 goto activate_locked;
468 }
469#endif /* CONFIG_SWAP */
470
471 mapping = page_mapping(page);
472 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
473 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
474
475 /*
476 * The page is mapped into the page tables of one or more
477 * processes. Try to unmap it here.
478 */
479 if (page_mapped(page) && mapping) {
480 switch (try_to_unmap(page)) {
481 case SWAP_FAIL:
482 goto activate_locked;
483 case SWAP_AGAIN:
484 goto keep_locked;
485 case SWAP_SUCCESS:
486 ; /* try to free the page below */
487 }
488 }
489
490 if (PageDirty(page)) {
491 if (referenced)
492 goto keep_locked;
493 if (!may_enter_fs)
494 goto keep_locked;
495 if (laptop_mode && !sc->may_writepage)
496 goto keep_locked;
497
498 /* Page is dirty, try to write it out here */
499 switch(pageout(page, mapping)) {
500 case PAGE_KEEP:
501 goto keep_locked;
502 case PAGE_ACTIVATE:
503 goto activate_locked;
504 case PAGE_SUCCESS:
505 if (PageWriteback(page) || PageDirty(page))
506 goto keep;
507 /*
508 * A synchronous write - probably a ramdisk. Go
509 * ahead and try to reclaim the page.
510 */
511 if (TestSetPageLocked(page))
512 goto keep;
513 if (PageDirty(page) || PageWriteback(page))
514 goto keep_locked;
515 mapping = page_mapping(page);
516 case PAGE_CLEAN:
517 ; /* try to free the page below */
518 }
519 }
520
521 /*
522 * If the page has buffers, try to free the buffer mappings
523 * associated with this page. If we succeed we try to free
524 * the page as well.
525 *
526 * We do this even if the page is PageDirty().
527 * try_to_release_page() does not perform I/O, but it is
528 * possible for a page to have PageDirty set, but it is actually
529 * clean (all its buffers are clean). This happens if the
530 * buffers were written out directly, with submit_bh(). ext3
531 * will do this, as well as the blockdev mapping.
532 * try_to_release_page() will discover that cleanness and will
533 * drop the buffers and mark the page clean - it can be freed.
534 *
535 * Rarely, pages can have buffers and no ->mapping. These are
536 * the pages which were not successfully invalidated in
537 * truncate_complete_page(). We try to drop those buffers here
538 * and if that worked, and the page is no longer mapped into
539 * process address space (page_count == 1) it can be freed.
540 * Otherwise, leave the page on the LRU so it is swappable.
541 */
542 if (PagePrivate(page)) {
543 if (!try_to_release_page(page, sc->gfp_mask))
544 goto activate_locked;
545 if (!mapping && page_count(page) == 1)
546 goto free_it;
547 }
548
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800549 if (!remove_mapping(mapping, page))
550 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551
552free_it:
553 unlock_page(page);
554 reclaimed++;
555 if (!pagevec_add(&freed_pvec, page))
556 __pagevec_release_nonlru(&freed_pvec);
557 continue;
558
559activate_locked:
560 SetPageActive(page);
561 pgactivate++;
562keep_locked:
563 unlock_page(page);
564keep:
565 list_add(&page->lru, &ret_pages);
566 BUG_ON(PageLRU(page));
567 }
568 list_splice(&ret_pages, page_list);
569 if (pagevec_count(&freed_pvec))
570 __pagevec_release_nonlru(&freed_pvec);
571 mod_page_state(pgactivate, pgactivate);
572 sc->nr_reclaimed += reclaimed;
573 return reclaimed;
574}
575
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800576#ifdef CONFIG_MIGRATION
Christoph Lameter8419c312006-01-08 01:00:52 -0800577static inline void move_to_lru(struct page *page)
578{
579 list_del(&page->lru);
580 if (PageActive(page)) {
581 /*
582 * lru_cache_add_active checks that
583 * the PG_active bit is off.
584 */
585 ClearPageActive(page);
586 lru_cache_add_active(page);
587 } else {
588 lru_cache_add(page);
589 }
590 put_page(page);
591}
592
593/*
Nick Piggin053837f2006-01-18 17:42:27 -0800594 * Add isolated pages on the list back to the LRU.
Christoph Lameter8419c312006-01-08 01:00:52 -0800595 *
596 * returns the number of pages put back.
597 */
598int putback_lru_pages(struct list_head *l)
599{
600 struct page *page;
601 struct page *page2;
602 int count = 0;
603
604 list_for_each_entry_safe(page, page2, l, lru) {
605 move_to_lru(page);
606 count++;
607 }
608 return count;
609}
610
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611/*
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800612 * swapout a single page
613 * page is locked upon entry, unlocked on exit
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800614 */
615static int swap_page(struct page *page)
616{
617 struct address_space *mapping = page_mapping(page);
618
619 if (page_mapped(page) && mapping)
620 if (try_to_unmap(page) != SWAP_SUCCESS)
621 goto unlock_retry;
622
623 if (PageDirty(page)) {
624 /* Page is dirty, try to write it out here */
625 switch(pageout(page, mapping)) {
626 case PAGE_KEEP:
627 case PAGE_ACTIVATE:
628 goto unlock_retry;
629
630 case PAGE_SUCCESS:
631 goto retry;
632
633 case PAGE_CLEAN:
634 ; /* try to free the page below */
635 }
636 }
637
638 if (PagePrivate(page)) {
639 if (!try_to_release_page(page, GFP_KERNEL) ||
640 (!mapping && page_count(page) == 1))
641 goto unlock_retry;
642 }
643
644 if (remove_mapping(mapping, page)) {
645 /* Success */
646 unlock_page(page);
647 return 0;
648 }
649
650unlock_retry:
651 unlock_page(page);
652
653retry:
Christoph Lameterd0d96322006-01-08 01:00:55 -0800654 return -EAGAIN;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800655}
656/*
657 * migrate_pages
658 *
659 * Two lists are passed to this function. The first list
660 * contains the pages isolated from the LRU to be migrated.
661 * The second list contains new pages that the pages isolated
662 * can be moved to. If the second list is NULL then all
663 * pages are swapped out.
664 *
665 * The function returns after 10 attempts or if no pages
666 * are movable anymore because t has become empty
667 * or no retryable pages exist anymore.
668 *
669 * SIMPLIFIED VERSION: This implementation of migrate_pages
670 * is only swapping out pages and never touches the second
671 * list. The direct migration patchset
672 * extends this function to avoid the use of swap.
Christoph Lameterd0d96322006-01-08 01:00:55 -0800673 *
674 * Return: Number of pages not migrated when "to" ran empty.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800675 */
Christoph Lameterd4984712006-01-08 01:00:55 -0800676int migrate_pages(struct list_head *from, struct list_head *to,
677 struct list_head *moved, struct list_head *failed)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800678{
679 int retry;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800680 int nr_failed = 0;
681 int pass = 0;
682 struct page *page;
683 struct page *page2;
684 int swapwrite = current->flags & PF_SWAPWRITE;
Christoph Lameterd0d96322006-01-08 01:00:55 -0800685 int rc;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800686
687 if (!swapwrite)
688 current->flags |= PF_SWAPWRITE;
689
690redo:
691 retry = 0;
692
Christoph Lameterd4984712006-01-08 01:00:55 -0800693 list_for_each_entry_safe(page, page2, from, lru) {
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800694 cond_resched();
695
Christoph Lameterd0d96322006-01-08 01:00:55 -0800696 rc = 0;
697 if (page_count(page) == 1)
Christoph Lameteree274972006-01-08 01:00:54 -0800698 /* page was freed from under us. So we are done. */
Christoph Lameterd0d96322006-01-08 01:00:55 -0800699 goto next;
700
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800701 /*
702 * Skip locked pages during the first two passes to give the
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800703 * functions holding the lock time to release the page. Later we
704 * use lock_page() to have a higher chance of acquiring the
705 * lock.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800706 */
Christoph Lameterd0d96322006-01-08 01:00:55 -0800707 rc = -EAGAIN;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800708 if (pass > 2)
709 lock_page(page);
710 else
711 if (TestSetPageLocked(page))
Christoph Lameterd0d96322006-01-08 01:00:55 -0800712 goto next;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800713
714 /*
715 * Only wait on writeback if we have already done a pass where
716 * we we may have triggered writeouts for lots of pages.
717 */
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800718 if (pass > 0) {
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800719 wait_on_page_writeback(page);
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800720 } else {
Christoph Lameterd0d96322006-01-08 01:00:55 -0800721 if (PageWriteback(page))
722 goto unlock_page;
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800723 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800724
Christoph Lameterd0d96322006-01-08 01:00:55 -0800725 /*
726 * Anonymous pages must have swap cache references otherwise
727 * the information contained in the page maps cannot be
728 * preserved.
729 */
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800730 if (PageAnon(page) && !PageSwapCache(page)) {
Christoph Lameter1480a542006-01-08 01:00:53 -0800731 if (!add_to_swap(page, GFP_KERNEL)) {
Christoph Lameterd0d96322006-01-08 01:00:55 -0800732 rc = -ENOMEM;
733 goto unlock_page;
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800734 }
735 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800736
737 /*
738 * Page is properly locked and writeback is complete.
739 * Try to migrate the page.
740 */
Christoph Lameterd0d96322006-01-08 01:00:55 -0800741 rc = swap_page(page);
742 goto next;
743
744unlock_page:
745 unlock_page(page);
746
747next:
748 if (rc == -EAGAIN) {
749 retry++;
750 } else if (rc) {
751 /* Permanent failure */
752 list_move(&page->lru, failed);
753 nr_failed++;
754 } else {
755 /* Success */
Christoph Lameterd4984712006-01-08 01:00:55 -0800756 list_move(&page->lru, moved);
Christoph Lameterd4984712006-01-08 01:00:55 -0800757 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800758 }
759 if (retry && pass++ < 10)
760 goto redo;
761
762 if (!swapwrite)
763 current->flags &= ~PF_SWAPWRITE;
764
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800765 return nr_failed + retry;
766}
Christoph Lameter8419c312006-01-08 01:00:52 -0800767
Christoph Lameter8419c312006-01-08 01:00:52 -0800768/*
769 * Isolate one page from the LRU lists and put it on the
Nick Piggin053837f2006-01-18 17:42:27 -0800770 * indicated list with elevated refcount.
Christoph Lameter8419c312006-01-08 01:00:52 -0800771 *
772 * Result:
773 * 0 = page not on LRU list
774 * 1 = page removed from LRU list and added to the specified list.
Christoph Lameter8419c312006-01-08 01:00:52 -0800775 */
776int isolate_lru_page(struct page *page)
777{
Nick Piggin053837f2006-01-18 17:42:27 -0800778 int ret = 0;
Christoph Lameter8419c312006-01-08 01:00:52 -0800779
Nick Piggin053837f2006-01-18 17:42:27 -0800780 if (PageLRU(page)) {
781 struct zone *zone = page_zone(page);
782 spin_lock_irq(&zone->lru_lock);
783 if (TestClearPageLRU(page)) {
784 ret = 1;
785 get_page(page);
786 if (PageActive(page))
787 del_page_from_active_list(zone, page);
788 else
789 del_page_from_inactive_list(zone, page);
790 }
791 spin_unlock_irq(&zone->lru_lock);
Christoph Lameter8419c312006-01-08 01:00:52 -0800792 }
Nick Piggin053837f2006-01-18 17:42:27 -0800793
794 return ret;
Christoph Lameter8419c312006-01-08 01:00:52 -0800795}
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800796#endif
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800797
798/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700799 * zone->lru_lock is heavily contended. Some of the functions that
800 * shrink the lists perform better by taking out a batch of pages
801 * and working on them outside the LRU lock.
802 *
803 * For pagecache intensive workloads, this function is the hottest
804 * spot in the kernel (apart from copy_*_user functions).
805 *
806 * Appropriate locks must be held before calling this function.
807 *
808 * @nr_to_scan: The number of pages to look through on the list.
809 * @src: The LRU list to pull pages off.
810 * @dst: The temp list to put pages on to.
811 * @scanned: The number of pages that were scanned.
812 *
813 * returns how many pages were moved onto *@dst.
814 */
815static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
816 struct list_head *dst, int *scanned)
817{
818 int nr_taken = 0;
819 struct page *page;
820 int scan = 0;
821
822 while (scan++ < nr_to_scan && !list_empty(src)) {
823 page = lru_to_page(src);
824 prefetchw_prev_lru_page(page, src, flags);
825
Nick Piggin053837f2006-01-18 17:42:27 -0800826 if (!TestClearPageLRU(page))
Christoph Lameter21eac812006-01-08 01:00:45 -0800827 BUG();
Nick Piggin053837f2006-01-18 17:42:27 -0800828 list_del(&page->lru);
829 if (get_page_testone(page)) {
830 /*
831 * It is being freed elsewhere
832 */
833 __put_page(page);
834 SetPageLRU(page);
835 list_add(&page->lru, src);
836 continue;
837 } else {
838 list_add(&page->lru, dst);
839 nr_taken++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700840 }
841 }
842
843 *scanned = scan;
844 return nr_taken;
845}
846
847/*
848 * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
849 */
850static void shrink_cache(struct zone *zone, struct scan_control *sc)
851{
852 LIST_HEAD(page_list);
853 struct pagevec pvec;
854 int max_scan = sc->nr_to_scan;
855
856 pagevec_init(&pvec, 1);
857
858 lru_add_drain();
859 spin_lock_irq(&zone->lru_lock);
860 while (max_scan > 0) {
861 struct page *page;
862 int nr_taken;
863 int nr_scan;
864 int nr_freed;
865
866 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
867 &zone->inactive_list,
868 &page_list, &nr_scan);
869 zone->nr_inactive -= nr_taken;
870 zone->pages_scanned += nr_scan;
871 spin_unlock_irq(&zone->lru_lock);
872
873 if (nr_taken == 0)
874 goto done;
875
876 max_scan -= nr_scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 nr_freed = shrink_list(&page_list, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878
Nick Piggina74609f2006-01-06 00:11:20 -0800879 local_irq_disable();
880 if (current_is_kswapd()) {
881 __mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
882 __mod_page_state(kswapd_steal, nr_freed);
883 } else
884 __mod_page_state_zone(zone, pgscan_direct, nr_scan);
885 __mod_page_state_zone(zone, pgsteal, nr_freed);
886
887 spin_lock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 /*
889 * Put back any unfreeable pages.
890 */
891 while (!list_empty(&page_list)) {
892 page = lru_to_page(&page_list);
893 if (TestSetPageLRU(page))
894 BUG();
895 list_del(&page->lru);
896 if (PageActive(page))
897 add_page_to_active_list(zone, page);
898 else
899 add_page_to_inactive_list(zone, page);
900 if (!pagevec_add(&pvec, page)) {
901 spin_unlock_irq(&zone->lru_lock);
902 __pagevec_release(&pvec);
903 spin_lock_irq(&zone->lru_lock);
904 }
905 }
906 }
907 spin_unlock_irq(&zone->lru_lock);
908done:
909 pagevec_release(&pvec);
910}
911
912/*
913 * This moves pages from the active list to the inactive list.
914 *
915 * We move them the other way if the page is referenced by one or more
916 * processes, from rmap.
917 *
918 * If the pages are mostly unmapped, the processing is fast and it is
919 * appropriate to hold zone->lru_lock across the whole operation. But if
920 * the pages are mapped, the processing is slow (page_referenced()) so we
921 * should drop zone->lru_lock around each page. It's impossible to balance
922 * this, so instead we remove the pages from the LRU while processing them.
923 * It is safe to rely on PG_active against the non-LRU pages in here because
924 * nobody will play with that bit on a non-LRU page.
925 *
926 * The downside is that we have to touch page->_count against each page.
927 * But we had to alter page->flags anyway.
928 */
929static void
930refill_inactive_zone(struct zone *zone, struct scan_control *sc)
931{
932 int pgmoved;
933 int pgdeactivate = 0;
934 int pgscanned;
935 int nr_pages = sc->nr_to_scan;
936 LIST_HEAD(l_hold); /* The pages which were snipped off */
937 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
938 LIST_HEAD(l_active); /* Pages to go onto the active_list */
939 struct page *page;
940 struct pagevec pvec;
941 int reclaim_mapped = 0;
942 long mapped_ratio;
943 long distress;
944 long swap_tendency;
945
946 lru_add_drain();
947 spin_lock_irq(&zone->lru_lock);
948 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
949 &l_hold, &pgscanned);
950 zone->pages_scanned += pgscanned;
951 zone->nr_active -= pgmoved;
952 spin_unlock_irq(&zone->lru_lock);
953
954 /*
955 * `distress' is a measure of how much trouble we're having reclaiming
956 * pages. 0 -> no problems. 100 -> great trouble.
957 */
958 distress = 100 >> zone->prev_priority;
959
960 /*
961 * The point of this algorithm is to decide when to start reclaiming
962 * mapped memory instead of just pagecache. Work out how much memory
963 * is mapped.
964 */
965 mapped_ratio = (sc->nr_mapped * 100) / total_memory;
966
967 /*
968 * Now decide how much we really want to unmap some pages. The mapped
969 * ratio is downgraded - just because there's a lot of mapped memory
970 * doesn't necessarily mean that page reclaim isn't succeeding.
971 *
972 * The distress ratio is important - we don't want to start going oom.
973 *
974 * A 100% value of vm_swappiness overrides this algorithm altogether.
975 */
976 swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
977
978 /*
979 * Now use this metric to decide whether to start moving mapped memory
980 * onto the inactive list.
981 */
982 if (swap_tendency >= 100)
983 reclaim_mapped = 1;
984
985 while (!list_empty(&l_hold)) {
986 cond_resched();
987 page = lru_to_page(&l_hold);
988 list_del(&page->lru);
989 if (page_mapped(page)) {
990 if (!reclaim_mapped ||
991 (total_swap_pages == 0 && PageAnon(page)) ||
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800992 page_referenced(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700993 list_add(&page->lru, &l_active);
994 continue;
995 }
996 }
997 list_add(&page->lru, &l_inactive);
998 }
999
1000 pagevec_init(&pvec, 1);
1001 pgmoved = 0;
1002 spin_lock_irq(&zone->lru_lock);
1003 while (!list_empty(&l_inactive)) {
1004 page = lru_to_page(&l_inactive);
1005 prefetchw_prev_lru_page(page, &l_inactive, flags);
1006 if (TestSetPageLRU(page))
1007 BUG();
1008 if (!TestClearPageActive(page))
1009 BUG();
1010 list_move(&page->lru, &zone->inactive_list);
1011 pgmoved++;
1012 if (!pagevec_add(&pvec, page)) {
1013 zone->nr_inactive += pgmoved;
1014 spin_unlock_irq(&zone->lru_lock);
1015 pgdeactivate += pgmoved;
1016 pgmoved = 0;
1017 if (buffer_heads_over_limit)
1018 pagevec_strip(&pvec);
1019 __pagevec_release(&pvec);
1020 spin_lock_irq(&zone->lru_lock);
1021 }
1022 }
1023 zone->nr_inactive += pgmoved;
1024 pgdeactivate += pgmoved;
1025 if (buffer_heads_over_limit) {
1026 spin_unlock_irq(&zone->lru_lock);
1027 pagevec_strip(&pvec);
1028 spin_lock_irq(&zone->lru_lock);
1029 }
1030
1031 pgmoved = 0;
1032 while (!list_empty(&l_active)) {
1033 page = lru_to_page(&l_active);
1034 prefetchw_prev_lru_page(page, &l_active, flags);
1035 if (TestSetPageLRU(page))
1036 BUG();
1037 BUG_ON(!PageActive(page));
1038 list_move(&page->lru, &zone->active_list);
1039 pgmoved++;
1040 if (!pagevec_add(&pvec, page)) {
1041 zone->nr_active += pgmoved;
1042 pgmoved = 0;
1043 spin_unlock_irq(&zone->lru_lock);
1044 __pagevec_release(&pvec);
1045 spin_lock_irq(&zone->lru_lock);
1046 }
1047 }
1048 zone->nr_active += pgmoved;
Nick Piggina74609f2006-01-06 00:11:20 -08001049 spin_unlock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050
Nick Piggina74609f2006-01-06 00:11:20 -08001051 __mod_page_state_zone(zone, pgrefill, pgscanned);
1052 __mod_page_state(pgdeactivate, pgdeactivate);
1053 local_irq_enable();
1054
1055 pagevec_release(&pvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056}
1057
1058/*
1059 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1060 */
1061static void
1062shrink_zone(struct zone *zone, struct scan_control *sc)
1063{
1064 unsigned long nr_active;
1065 unsigned long nr_inactive;
1066
Martin Hicks53e9a612005-09-03 15:54:51 -07001067 atomic_inc(&zone->reclaim_in_progress);
1068
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 /*
1070 * Add one to `nr_to_scan' just to make sure that the kernel will
1071 * slowly sift through the active list.
1072 */
1073 zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
1074 nr_active = zone->nr_scan_active;
1075 if (nr_active >= sc->swap_cluster_max)
1076 zone->nr_scan_active = 0;
1077 else
1078 nr_active = 0;
1079
1080 zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
1081 nr_inactive = zone->nr_scan_inactive;
1082 if (nr_inactive >= sc->swap_cluster_max)
1083 zone->nr_scan_inactive = 0;
1084 else
1085 nr_inactive = 0;
1086
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087 while (nr_active || nr_inactive) {
1088 if (nr_active) {
1089 sc->nr_to_scan = min(nr_active,
1090 (unsigned long)sc->swap_cluster_max);
1091 nr_active -= sc->nr_to_scan;
1092 refill_inactive_zone(zone, sc);
1093 }
1094
1095 if (nr_inactive) {
1096 sc->nr_to_scan = min(nr_inactive,
1097 (unsigned long)sc->swap_cluster_max);
1098 nr_inactive -= sc->nr_to_scan;
1099 shrink_cache(zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 }
1101 }
1102
1103 throttle_vm_writeout();
Martin Hicks53e9a612005-09-03 15:54:51 -07001104
1105 atomic_dec(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106}
1107
1108/*
1109 * This is the direct reclaim path, for page-allocating processes. We only
1110 * try to reclaim pages from zones which will satisfy the caller's allocation
1111 * request.
1112 *
1113 * We reclaim from a zone even if that zone is over pages_high. Because:
1114 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1115 * allocation or
1116 * b) The zones may be over pages_high but they must go *over* pages_high to
1117 * satisfy the `incremental min' zone defense algorithm.
1118 *
1119 * Returns the number of reclaimed pages.
1120 *
1121 * If a zone is deemed to be full of pinned pages then just give it a light
1122 * scan then give up on it.
1123 */
1124static void
1125shrink_caches(struct zone **zones, struct scan_control *sc)
1126{
1127 int i;
1128
1129 for (i = 0; zones[i] != NULL; i++) {
1130 struct zone *zone = zones[i];
1131
Con Kolivasf3fe6512006-01-06 00:11:15 -08001132 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133 continue;
1134
Paul Jackson9bf22292005-09-06 15:18:12 -07001135 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136 continue;
1137
1138 zone->temp_priority = sc->priority;
1139 if (zone->prev_priority > sc->priority)
1140 zone->prev_priority = sc->priority;
1141
1142 if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
1143 continue; /* Let kswapd poll it */
1144
1145 shrink_zone(zone, sc);
1146 }
1147}
1148
1149/*
1150 * This is the main entry point to direct page reclaim.
1151 *
1152 * If a full scan of the inactive list fails to free enough memory then we
1153 * are "out of memory" and something needs to be killed.
1154 *
1155 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1156 * high - the zone may be full of dirty or under-writeback pages, which this
1157 * caller can't do much about. We kick pdflush and take explicit naps in the
1158 * hope that some of these pages can be written. But if the allocating task
1159 * holds filesystem locks which prevent writeout this might not work, and the
1160 * allocation attempt will fail.
1161 */
Al Viro6daa0e22005-10-21 03:18:50 -04001162int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163{
1164 int priority;
1165 int ret = 0;
1166 int total_scanned = 0, total_reclaimed = 0;
1167 struct reclaim_state *reclaim_state = current->reclaim_state;
1168 struct scan_control sc;
1169 unsigned long lru_pages = 0;
1170 int i;
1171
1172 sc.gfp_mask = gfp_mask;
1173 sc.may_writepage = 0;
Christoph Lameterf1fd1062006-01-18 17:42:30 -08001174 sc.may_swap = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175
1176 inc_page_state(allocstall);
1177
1178 for (i = 0; zones[i] != NULL; i++) {
1179 struct zone *zone = zones[i];
1180
Paul Jackson9bf22292005-09-06 15:18:12 -07001181 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 continue;
1183
1184 zone->temp_priority = DEF_PRIORITY;
1185 lru_pages += zone->nr_active + zone->nr_inactive;
1186 }
1187
1188 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1189 sc.nr_mapped = read_page_state(nr_mapped);
1190 sc.nr_scanned = 0;
1191 sc.nr_reclaimed = 0;
1192 sc.priority = priority;
1193 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001194 if (!priority)
1195 disable_swap_token();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196 shrink_caches(zones, &sc);
1197 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
1198 if (reclaim_state) {
1199 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1200 reclaim_state->reclaimed_slab = 0;
1201 }
1202 total_scanned += sc.nr_scanned;
1203 total_reclaimed += sc.nr_reclaimed;
1204 if (total_reclaimed >= sc.swap_cluster_max) {
1205 ret = 1;
1206 goto out;
1207 }
1208
1209 /*
1210 * Try to write back as many pages as we just scanned. This
1211 * tends to cause slow streaming writers to write data to the
1212 * disk smoothly, at the dirtying rate, which is nice. But
1213 * that's undesirable in laptop mode, where we *want* lumpy
1214 * writeout. So in laptop mode, write out the whole world.
1215 */
1216 if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -07001217 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218 sc.may_writepage = 1;
1219 }
1220
1221 /* Take a nap, wait for some writeback to complete */
1222 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
1223 blk_congestion_wait(WRITE, HZ/10);
1224 }
1225out:
1226 for (i = 0; zones[i] != 0; i++) {
1227 struct zone *zone = zones[i];
1228
Paul Jackson9bf22292005-09-06 15:18:12 -07001229 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230 continue;
1231
1232 zone->prev_priority = zone->temp_priority;
1233 }
1234 return ret;
1235}
1236
1237/*
1238 * For kswapd, balance_pgdat() will work across all this node's zones until
1239 * they are all at pages_high.
1240 *
1241 * If `nr_pages' is non-zero then it is the number of pages which are to be
1242 * reclaimed, regardless of the zone occupancies. This is a software suspend
1243 * special.
1244 *
1245 * Returns the number of pages which were actually freed.
1246 *
1247 * There is special handling here for zones which are full of pinned pages.
1248 * This can happen if the pages are all mlocked, or if they are all used by
1249 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1250 * What we do is to detect the case where all pages in the zone have been
1251 * scanned twice and there has been zero successful reclaim. Mark the zone as
1252 * dead and from now on, only perform a short scan. Basically we're polling
1253 * the zone for when the problem goes away.
1254 *
1255 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1256 * zones which have free_pages > pages_high, but once a zone is found to have
1257 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1258 * of the number of free pages in the lower zones. This interoperates with
1259 * the page allocator fallback scheme to ensure that aging of pages is balanced
1260 * across the zones.
1261 */
1262static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
1263{
1264 int to_free = nr_pages;
1265 int all_zones_ok;
1266 int priority;
1267 int i;
1268 int total_scanned, total_reclaimed;
1269 struct reclaim_state *reclaim_state = current->reclaim_state;
1270 struct scan_control sc;
1271
1272loop_again:
1273 total_scanned = 0;
1274 total_reclaimed = 0;
1275 sc.gfp_mask = GFP_KERNEL;
1276 sc.may_writepage = 0;
Christoph Lameterf1fd1062006-01-18 17:42:30 -08001277 sc.may_swap = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278 sc.nr_mapped = read_page_state(nr_mapped);
1279
1280 inc_page_state(pageoutrun);
1281
1282 for (i = 0; i < pgdat->nr_zones; i++) {
1283 struct zone *zone = pgdat->node_zones + i;
1284
1285 zone->temp_priority = DEF_PRIORITY;
1286 }
1287
1288 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1289 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1290 unsigned long lru_pages = 0;
1291
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001292 /* The swap token gets in the way of swapout... */
1293 if (!priority)
1294 disable_swap_token();
1295
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296 all_zones_ok = 1;
1297
1298 if (nr_pages == 0) {
1299 /*
1300 * Scan in the highmem->dma direction for the highest
1301 * zone which needs scanning
1302 */
1303 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1304 struct zone *zone = pgdat->node_zones + i;
1305
Con Kolivasf3fe6512006-01-06 00:11:15 -08001306 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 continue;
1308
1309 if (zone->all_unreclaimable &&
1310 priority != DEF_PRIORITY)
1311 continue;
1312
1313 if (!zone_watermark_ok(zone, order,
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001314 zone->pages_high, 0, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001315 end_zone = i;
1316 goto scan;
1317 }
1318 }
1319 goto out;
1320 } else {
1321 end_zone = pgdat->nr_zones - 1;
1322 }
1323scan:
1324 for (i = 0; i <= end_zone; i++) {
1325 struct zone *zone = pgdat->node_zones + i;
1326
1327 lru_pages += zone->nr_active + zone->nr_inactive;
1328 }
1329
1330 /*
1331 * Now scan the zone in the dma->highmem direction, stopping
1332 * at the last zone which needs scanning.
1333 *
1334 * We do this because the page allocator works in the opposite
1335 * direction. This prevents the page allocator from allocating
1336 * pages behind kswapd's direction of progress, which would
1337 * cause too much scanning of the lower zones.
1338 */
1339 for (i = 0; i <= end_zone; i++) {
1340 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001341 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342
Con Kolivasf3fe6512006-01-06 00:11:15 -08001343 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 continue;
1345
1346 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1347 continue;
1348
1349 if (nr_pages == 0) { /* Not software suspend */
1350 if (!zone_watermark_ok(zone, order,
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001351 zone->pages_high, end_zone, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 all_zones_ok = 0;
1353 }
1354 zone->temp_priority = priority;
1355 if (zone->prev_priority > priority)
1356 zone->prev_priority = priority;
1357 sc.nr_scanned = 0;
1358 sc.nr_reclaimed = 0;
1359 sc.priority = priority;
1360 sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001361 atomic_inc(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362 shrink_zone(zone, &sc);
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001363 atomic_dec(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001365 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1366 lru_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1368 total_reclaimed += sc.nr_reclaimed;
1369 total_scanned += sc.nr_scanned;
1370 if (zone->all_unreclaimable)
1371 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001372 if (nr_slab == 0 && zone->pages_scanned >=
1373 (zone->nr_active + zone->nr_inactive) * 4)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 zone->all_unreclaimable = 1;
1375 /*
1376 * If we've done a decent amount of scanning and
1377 * the reclaim ratio is low, start doing writepage
1378 * even in laptop mode
1379 */
1380 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1381 total_scanned > total_reclaimed+total_reclaimed/2)
1382 sc.may_writepage = 1;
1383 }
1384 if (nr_pages && to_free > total_reclaimed)
1385 continue; /* swsusp: need to do more work */
1386 if (all_zones_ok)
1387 break; /* kswapd: all done */
1388 /*
1389 * OK, kswapd is getting into trouble. Take a nap, then take
1390 * another pass across the zones.
1391 */
1392 if (total_scanned && priority < DEF_PRIORITY - 2)
1393 blk_congestion_wait(WRITE, HZ/10);
1394
1395 /*
1396 * We do this so kswapd doesn't build up large priorities for
1397 * example when it is freeing in parallel with allocators. It
1398 * matches the direct reclaim path behaviour in terms of impact
1399 * on zone->*_priority.
1400 */
1401 if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
1402 break;
1403 }
1404out:
1405 for (i = 0; i < pgdat->nr_zones; i++) {
1406 struct zone *zone = pgdat->node_zones + i;
1407
1408 zone->prev_priority = zone->temp_priority;
1409 }
1410 if (!all_zones_ok) {
1411 cond_resched();
1412 goto loop_again;
1413 }
1414
1415 return total_reclaimed;
1416}
1417
1418/*
1419 * The background pageout daemon, started as a kernel thread
1420 * from the init process.
1421 *
1422 * This basically trickles out pages so that we have _some_
1423 * free memory available even if there is no other activity
1424 * that frees anything up. This is needed for things like routing
1425 * etc, where we otherwise might have all activity going on in
1426 * asynchronous contexts that cannot page things out.
1427 *
1428 * If there are applications that are active memory-allocators
1429 * (most normal use), this basically shouldn't matter.
1430 */
1431static int kswapd(void *p)
1432{
1433 unsigned long order;
1434 pg_data_t *pgdat = (pg_data_t*)p;
1435 struct task_struct *tsk = current;
1436 DEFINE_WAIT(wait);
1437 struct reclaim_state reclaim_state = {
1438 .reclaimed_slab = 0,
1439 };
1440 cpumask_t cpumask;
1441
1442 daemonize("kswapd%d", pgdat->node_id);
1443 cpumask = node_to_cpumask(pgdat->node_id);
1444 if (!cpus_empty(cpumask))
1445 set_cpus_allowed(tsk, cpumask);
1446 current->reclaim_state = &reclaim_state;
1447
1448 /*
1449 * Tell the memory management that we're a "memory allocator",
1450 * and that if we need more memory we should get access to it
1451 * regardless (see "__alloc_pages()"). "kswapd" should
1452 * never get caught in the normal page freeing logic.
1453 *
1454 * (Kswapd normally doesn't need memory anyway, but sometimes
1455 * you need a small amount of memory in order to be able to
1456 * page out something else, and this flag essentially protects
1457 * us from recursively trying to free more memory as we're
1458 * trying to free the first piece of memory in the first place).
1459 */
Christoph Lameter930d9152006-01-08 01:00:47 -08001460 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461
1462 order = 0;
1463 for ( ; ; ) {
1464 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001465
1466 try_to_freeze();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467
1468 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1469 new_order = pgdat->kswapd_max_order;
1470 pgdat->kswapd_max_order = 0;
1471 if (order < new_order) {
1472 /*
1473 * Don't sleep if someone wants a larger 'order'
1474 * allocation
1475 */
1476 order = new_order;
1477 } else {
1478 schedule();
1479 order = pgdat->kswapd_max_order;
1480 }
1481 finish_wait(&pgdat->kswapd_wait, &wait);
1482
1483 balance_pgdat(pgdat, 0, order);
1484 }
1485 return 0;
1486}
1487
1488/*
1489 * A zone is low on free memory, so wake its kswapd task to service it.
1490 */
1491void wakeup_kswapd(struct zone *zone, int order)
1492{
1493 pg_data_t *pgdat;
1494
Con Kolivasf3fe6512006-01-06 00:11:15 -08001495 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496 return;
1497
1498 pgdat = zone->zone_pgdat;
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001499 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 return;
1501 if (pgdat->kswapd_max_order < order)
1502 pgdat->kswapd_max_order = order;
Paul Jackson9bf22292005-09-06 15:18:12 -07001503 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001505 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001506 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001507 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508}
1509
1510#ifdef CONFIG_PM
1511/*
1512 * Try to free `nr_pages' of memory, system-wide. Returns the number of freed
1513 * pages.
1514 */
1515int shrink_all_memory(int nr_pages)
1516{
1517 pg_data_t *pgdat;
1518 int nr_to_free = nr_pages;
1519 int ret = 0;
1520 struct reclaim_state reclaim_state = {
1521 .reclaimed_slab = 0,
1522 };
1523
1524 current->reclaim_state = &reclaim_state;
1525 for_each_pgdat(pgdat) {
1526 int freed;
1527 freed = balance_pgdat(pgdat, nr_to_free, 0);
1528 ret += freed;
1529 nr_to_free -= freed;
1530 if (nr_to_free <= 0)
1531 break;
1532 }
1533 current->reclaim_state = NULL;
1534 return ret;
1535}
1536#endif
1537
1538#ifdef CONFIG_HOTPLUG_CPU
1539/* It's optimal to keep kswapds on the same CPUs as their memory, but
1540 not required for correctness. So if the last cpu in a node goes
1541 away, we get changed to run anywhere: as the first one comes back,
1542 restore their cpu bindings. */
1543static int __devinit cpu_callback(struct notifier_block *nfb,
1544 unsigned long action,
1545 void *hcpu)
1546{
1547 pg_data_t *pgdat;
1548 cpumask_t mask;
1549
1550 if (action == CPU_ONLINE) {
1551 for_each_pgdat(pgdat) {
1552 mask = node_to_cpumask(pgdat->node_id);
1553 if (any_online_cpu(mask) != NR_CPUS)
1554 /* One of our CPUs online: restore mask */
1555 set_cpus_allowed(pgdat->kswapd, mask);
1556 }
1557 }
1558 return NOTIFY_OK;
1559}
1560#endif /* CONFIG_HOTPLUG_CPU */
1561
1562static int __init kswapd_init(void)
1563{
1564 pg_data_t *pgdat;
1565 swap_setup();
1566 for_each_pgdat(pgdat)
1567 pgdat->kswapd
1568 = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
1569 total_memory = nr_free_pagecache_pages();
1570 hotcpu_notifier(cpu_callback, 0);
1571 return 0;
1572}
1573
1574module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08001575
1576#ifdef CONFIG_NUMA
1577/*
1578 * Zone reclaim mode
1579 *
1580 * If non-zero call zone_reclaim when the number of free pages falls below
1581 * the watermarks.
1582 *
1583 * In the future we may add flags to the mode. However, the page allocator
1584 * should only have to check that zone_reclaim_mode != 0 before calling
1585 * zone_reclaim().
1586 */
1587int zone_reclaim_mode __read_mostly;
1588
1589/*
1590 * Mininum time between zone reclaim scans
1591 */
1592#define ZONE_RECLAIM_INTERVAL HZ/2
1593/*
1594 * Try to free up some pages from this zone through reclaim.
1595 */
1596int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
1597{
1598 int nr_pages = 1 << order;
1599 struct task_struct *p = current;
1600 struct reclaim_state reclaim_state;
1601 struct scan_control sc = {
1602 .gfp_mask = gfp_mask,
1603 .may_writepage = 0,
1604 .may_swap = 0,
1605 .nr_mapped = read_page_state(nr_mapped),
1606 .nr_scanned = 0,
1607 .nr_reclaimed = 0,
1608 .priority = 0
1609 };
1610
1611 if (!(gfp_mask & __GFP_WAIT) ||
1612 zone->zone_pgdat->node_id != numa_node_id() ||
1613 zone->all_unreclaimable ||
1614 atomic_read(&zone->reclaim_in_progress) > 0)
1615 return 0;
1616
1617 if (time_before(jiffies,
1618 zone->last_unsuccessful_zone_reclaim + ZONE_RECLAIM_INTERVAL))
1619 return 0;
1620
1621 disable_swap_token();
1622
1623 if (nr_pages > SWAP_CLUSTER_MAX)
1624 sc.swap_cluster_max = nr_pages;
1625 else
1626 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
1627
1628 cond_resched();
1629 p->flags |= PF_MEMALLOC;
1630 reclaim_state.reclaimed_slab = 0;
1631 p->reclaim_state = &reclaim_state;
1632 shrink_zone(zone, &sc);
1633 p->reclaim_state = NULL;
1634 current->flags &= ~PF_MEMALLOC;
1635
1636 if (sc.nr_reclaimed == 0)
1637 zone->last_unsuccessful_zone_reclaim = jiffies;
1638
1639 return sc.nr_reclaimed > nr_pages;
1640}
1641#endif
1642