blob: eca70310adb26239e94c5435eaf2abf0271c89fa [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>
Andrew Mortone129b5c2006-09-27 01:50:00 -070022#include <linux/vmstat.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023#include <linux/file.h>
24#include <linux/writeback.h>
25#include <linux/blkdev.h>
26#include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28#include <linux/mm_inline.h>
29#include <linux/pagevec.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/notifier.h>
36#include <linux/rwsem.h>
Rafael J. Wysocki248a0302006-03-22 00:09:04 -080037#include <linux/delay.h>
Yasunori Goto3218ae12006-06-27 02:53:33 -070038#include <linux/kthread.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070039
40#include <asm/tlbflush.h>
41#include <asm/div64.h>
42
43#include <linux/swapops.h>
44
Nick Piggin0f8053a2006-03-22 00:08:33 -080045#include "internal.h"
46
Linus Torvalds1da177e2005-04-16 15:20:36 -070047struct scan_control {
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 /* Incremented by the number of inactive pages that were scanned */
49 unsigned long nr_scanned;
50
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040052 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54 int may_writepage;
55
Christoph Lameterf1fd1062006-01-18 17:42:30 -080056 /* Can pages be swapped as part of reclaim? */
57 int may_swap;
58
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
60 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
61 * In this context, it doesn't matter that we scan the
62 * whole list at once. */
63 int swap_cluster_max;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -070064
65 int swappiness;
Nick Piggin408d8542006-09-25 23:31:27 -070066
67 int all_unreclaimable;
Linus Torvalds1da177e2005-04-16 15:20:36 -070068};
69
70/*
71 * The list of shrinker callbacks used by to apply pressure to
72 * ageable caches.
73 */
74struct shrinker {
75 shrinker_t shrinker;
76 struct list_head list;
77 int seeks; /* seeks to recreate an obj */
78 long nr; /* objs pending delete */
79};
80
81#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
82
83#ifdef ARCH_HAS_PREFETCH
84#define prefetch_prev_lru_page(_page, _base, _field) \
85 do { \
86 if ((_page)->lru.prev != _base) { \
87 struct page *prev; \
88 \
89 prev = lru_to_page(&(_page->lru)); \
90 prefetch(&prev->_field); \
91 } \
92 } while (0)
93#else
94#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
95#endif
96
97#ifdef ARCH_HAS_PREFETCHW
98#define prefetchw_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 prefetchw(&prev->_field); \
105 } \
106 } while (0)
107#else
108#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
109#endif
110
111/*
112 * From 0 .. 100. Higher means more swappy.
113 */
114int vm_swappiness = 60;
Andrew Mortonbd1e22b2006-06-23 02:03:47 -0700115long vm_total_pages; /* The total number of pages which the VM controls */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
117static LIST_HEAD(shrinker_list);
118static DECLARE_RWSEM(shrinker_rwsem);
119
120/*
121 * Add a shrinker callback to be called from the vm
122 */
123struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
124{
125 struct shrinker *shrinker;
126
127 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
128 if (shrinker) {
129 shrinker->shrinker = theshrinker;
130 shrinker->seeks = seeks;
131 shrinker->nr = 0;
132 down_write(&shrinker_rwsem);
133 list_add_tail(&shrinker->list, &shrinker_list);
134 up_write(&shrinker_rwsem);
135 }
136 return shrinker;
137}
138EXPORT_SYMBOL(set_shrinker);
139
140/*
141 * Remove one
142 */
143void remove_shrinker(struct shrinker *shrinker)
144{
145 down_write(&shrinker_rwsem);
146 list_del(&shrinker->list);
147 up_write(&shrinker_rwsem);
148 kfree(shrinker);
149}
150EXPORT_SYMBOL(remove_shrinker);
151
152#define SHRINK_BATCH 128
153/*
154 * Call the shrink functions to age shrinkable caches
155 *
156 * Here we assume it costs one seek to replace a lru page and that it also
157 * takes a seek to recreate a cache object. With this in mind we age equal
158 * percentages of the lru and ageable caches. This should balance the seeks
159 * generated by these structures.
160 *
161 * If the vm encounted mapped pages on the LRU it increase the pressure on
162 * slab to avoid swapping.
163 *
164 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
165 *
166 * `lru_pages' represents the number of on-LRU pages in all the zones which
167 * are eligible for the caller's allocation attempt. It is used for balancing
168 * slab reclaim versus page reclaim.
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700169 *
170 * Returns the number of slab objects which we shrunk.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 */
Andrew Morton69e05942006-03-22 00:08:19 -0800172unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
173 unsigned long lru_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174{
175 struct shrinker *shrinker;
Andrew Morton69e05942006-03-22 00:08:19 -0800176 unsigned long ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177
178 if (scanned == 0)
179 scanned = SWAP_CLUSTER_MAX;
180
181 if (!down_read_trylock(&shrinker_rwsem))
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700182 return 1; /* Assume we'll be able to shrink next time */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
184 list_for_each_entry(shrinker, &shrinker_list, list) {
185 unsigned long long delta;
186 unsigned long total_scan;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800187 unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
189 delta = (4 * scanned) / shrinker->seeks;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800190 delta *= max_pass;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 do_div(delta, lru_pages + 1);
192 shrinker->nr += delta;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800193 if (shrinker->nr < 0) {
194 printk(KERN_ERR "%s: nr=%ld\n",
195 __FUNCTION__, shrinker->nr);
196 shrinker->nr = max_pass;
197 }
198
199 /*
200 * Avoid risking looping forever due to too large nr value:
201 * never try to free more than twice the estimate number of
202 * freeable entries.
203 */
204 if (shrinker->nr > max_pass * 2)
205 shrinker->nr = max_pass * 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206
207 total_scan = shrinker->nr;
208 shrinker->nr = 0;
209
210 while (total_scan >= SHRINK_BATCH) {
211 long this_scan = SHRINK_BATCH;
212 int shrink_ret;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700213 int nr_before;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700215 nr_before = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
217 if (shrink_ret == -1)
218 break;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700219 if (shrink_ret < nr_before)
220 ret += nr_before - shrink_ret;
Christoph Lameterf8891e52006-06-30 01:55:45 -0700221 count_vm_events(SLABS_SCANNED, this_scan);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222 total_scan -= this_scan;
223
224 cond_resched();
225 }
226
227 shrinker->nr += total_scan;
228 }
229 up_read(&shrinker_rwsem);
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700230 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231}
232
233/* Called without lock on whether page is mapped, so answer is unstable */
234static inline int page_mapping_inuse(struct page *page)
235{
236 struct address_space *mapping;
237
238 /* Page is in somebody's page tables. */
239 if (page_mapped(page))
240 return 1;
241
242 /* Be more reluctant to reclaim swapcache than pagecache */
243 if (PageSwapCache(page))
244 return 1;
245
246 mapping = page_mapping(page);
247 if (!mapping)
248 return 0;
249
250 /* File is mmap'd by somebody? */
251 return mapping_mapped(mapping);
252}
253
254static inline int is_page_cache_freeable(struct page *page)
255{
256 return page_count(page) - !!PagePrivate(page) == 2;
257}
258
259static int may_write_to_queue(struct backing_dev_info *bdi)
260{
Christoph Lameter930d9152006-01-08 01:00:47 -0800261 if (current->flags & PF_SWAPWRITE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 return 1;
263 if (!bdi_write_congested(bdi))
264 return 1;
265 if (bdi == current->backing_dev_info)
266 return 1;
267 return 0;
268}
269
270/*
271 * We detected a synchronous write error writing a page out. Probably
272 * -ENOSPC. We need to propagate that into the address_space for a subsequent
273 * fsync(), msync() or close().
274 *
275 * The tricky part is that after writepage we cannot touch the mapping: nothing
276 * prevents it from being freed up. But we have a ref on the page and once
277 * that page is locked, the mapping is pinned.
278 *
279 * We're allowed to run sleeping lock_page() here because we know the caller has
280 * __GFP_FS.
281 */
282static void handle_write_error(struct address_space *mapping,
283 struct page *page, int error)
284{
285 lock_page(page);
286 if (page_mapping(page) == mapping) {
287 if (error == -ENOSPC)
288 set_bit(AS_ENOSPC, &mapping->flags);
289 else
290 set_bit(AS_EIO, &mapping->flags);
291 }
292 unlock_page(page);
293}
294
Christoph Lameter04e62a22006-06-23 02:03:38 -0700295/* possible outcome of pageout() */
296typedef enum {
297 /* failed to write page out, page is locked */
298 PAGE_KEEP,
299 /* move page to the active list, page is locked */
300 PAGE_ACTIVATE,
301 /* page has been sent to the disk successfully, page is unlocked */
302 PAGE_SUCCESS,
303 /* page is clean and locked */
304 PAGE_CLEAN,
305} pageout_t;
306
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307/*
Andrew Morton1742f192006-03-22 00:08:21 -0800308 * pageout is called by shrink_page_list() for each dirty page.
309 * Calls ->writepage().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 */
Christoph Lameter04e62a22006-06-23 02:03:38 -0700311static pageout_t pageout(struct page *page, struct address_space *mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312{
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,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700356 .range_start = 0,
357 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 .nonblocking = 1,
359 .for_reclaim = 1,
360 };
361
362 SetPageReclaim(page);
363 res = mapping->a_ops->writepage(page, &wbc);
364 if (res < 0)
365 handle_write_error(mapping, page, res);
Zach Brown994fc28c2005-12-15 14:28:17 -0800366 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 ClearPageReclaim(page);
368 return PAGE_ACTIVATE;
369 }
370 if (!PageWriteback(page)) {
371 /* synchronous write or broken a_ops? */
372 ClearPageReclaim(page);
373 }
Andrew Mortone129b5c2006-09-27 01:50:00 -0700374 inc_zone_page_state(page, NR_VMSCAN_WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 return PAGE_SUCCESS;
376 }
377
378 return PAGE_CLEAN;
379}
380
Christoph Lameterb20a3502006-03-22 00:09:12 -0800381int remove_mapping(struct address_space *mapping, struct page *page)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800382{
Nick Piggin28e4d962006-09-25 23:31:23 -0700383 BUG_ON(!PageLocked(page));
384 BUG_ON(mapping != page_mapping(page));
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800385
386 write_lock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800387 /*
Nick Piggin0fd0e6b2006-09-27 01:50:02 -0700388 * The non racy check for a busy page.
389 *
390 * Must be careful with the order of the tests. When someone has
391 * a ref to the page, it may be possible that they dirty it then
392 * drop the reference. So if PageDirty is tested before page_count
393 * here, then the following race may occur:
394 *
395 * get_user_pages(&page);
396 * [user mapping goes away]
397 * write_to(page);
398 * !PageDirty(page) [good]
399 * SetPageDirty(page);
400 * put_page(page);
401 * !page_count(page) [good, discard it]
402 *
403 * [oops, our write_to data is lost]
404 *
405 * Reversing the order of the tests ensures such a situation cannot
406 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
407 * load is not satisfied before that of page->_count.
408 *
409 * Note that if SetPageDirty is always performed via set_page_dirty,
410 * and thus under tree_lock, then this ordering is not required.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800411 */
412 if (unlikely(page_count(page) != 2))
413 goto cannot_free;
414 smp_rmb();
415 if (unlikely(PageDirty(page)))
416 goto cannot_free;
417
418 if (PageSwapCache(page)) {
419 swp_entry_t swap = { .val = page_private(page) };
420 __delete_from_swap_cache(page);
421 write_unlock_irq(&mapping->tree_lock);
422 swap_free(swap);
423 __put_page(page); /* The pagecache ref */
424 return 1;
425 }
426
427 __remove_from_page_cache(page);
428 write_unlock_irq(&mapping->tree_lock);
429 __put_page(page);
430 return 1;
431
432cannot_free:
433 write_unlock_irq(&mapping->tree_lock);
434 return 0;
435}
436
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437/*
Andrew Morton1742f192006-03-22 00:08:21 -0800438 * shrink_page_list() returns the number of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 */
Andrew Morton1742f192006-03-22 00:08:21 -0800440static unsigned long shrink_page_list(struct list_head *page_list,
441 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442{
443 LIST_HEAD(ret_pages);
444 struct pagevec freed_pvec;
445 int pgactivate = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800446 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447
448 cond_resched();
449
450 pagevec_init(&freed_pvec, 1);
451 while (!list_empty(page_list)) {
452 struct address_space *mapping;
453 struct page *page;
454 int may_enter_fs;
455 int referenced;
456
457 cond_resched();
458
459 page = lru_to_page(page_list);
460 list_del(&page->lru);
461
462 if (TestSetPageLocked(page))
463 goto keep;
464
Nick Piggin725d7042006-09-25 23:30:55 -0700465 VM_BUG_ON(PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466
467 sc->nr_scanned++;
Christoph Lameter80e43422006-02-11 17:55:53 -0800468
469 if (!sc->may_swap && page_mapped(page))
470 goto keep_locked;
471
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 /* Double the slab pressure for mapped and swapcache pages */
473 if (page_mapped(page) || PageSwapCache(page))
474 sc->nr_scanned++;
475
476 if (PageWriteback(page))
477 goto keep_locked;
478
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800479 referenced = page_referenced(page, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 /* In active use or really unfreeable? Activate it. */
481 if (referenced && page_mapping_inuse(page))
482 goto activate_locked;
483
484#ifdef CONFIG_SWAP
485 /*
486 * Anonymous process memory has backing store?
487 * Try to allocate it some swap space here.
488 */
Christoph Lameter6e5ef1a2006-03-22 00:08:45 -0800489 if (PageAnon(page) && !PageSwapCache(page))
Christoph Lameter1480a542006-01-08 01:00:53 -0800490 if (!add_to_swap(page, GFP_ATOMIC))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 goto activate_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492#endif /* CONFIG_SWAP */
493
494 mapping = page_mapping(page);
495 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
496 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
497
498 /*
499 * The page is mapped into the page tables of one or more
500 * processes. Try to unmap it here.
501 */
502 if (page_mapped(page) && mapping) {
Christoph Lametera48d07a2006-02-01 03:05:38 -0800503 switch (try_to_unmap(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 case SWAP_FAIL:
505 goto activate_locked;
506 case SWAP_AGAIN:
507 goto keep_locked;
508 case SWAP_SUCCESS:
509 ; /* try to free the page below */
510 }
511 }
512
513 if (PageDirty(page)) {
514 if (referenced)
515 goto keep_locked;
516 if (!may_enter_fs)
517 goto keep_locked;
Christoph Lameter52a83632006-02-01 03:05:28 -0800518 if (!sc->may_writepage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 goto keep_locked;
520
521 /* Page is dirty, try to write it out here */
522 switch(pageout(page, mapping)) {
523 case PAGE_KEEP:
524 goto keep_locked;
525 case PAGE_ACTIVATE:
526 goto activate_locked;
527 case PAGE_SUCCESS:
528 if (PageWriteback(page) || PageDirty(page))
529 goto keep;
530 /*
531 * A synchronous write - probably a ramdisk. Go
532 * ahead and try to reclaim the page.
533 */
534 if (TestSetPageLocked(page))
535 goto keep;
536 if (PageDirty(page) || PageWriteback(page))
537 goto keep_locked;
538 mapping = page_mapping(page);
539 case PAGE_CLEAN:
540 ; /* try to free the page below */
541 }
542 }
543
544 /*
545 * If the page has buffers, try to free the buffer mappings
546 * associated with this page. If we succeed we try to free
547 * the page as well.
548 *
549 * We do this even if the page is PageDirty().
550 * try_to_release_page() does not perform I/O, but it is
551 * possible for a page to have PageDirty set, but it is actually
552 * clean (all its buffers are clean). This happens if the
553 * buffers were written out directly, with submit_bh(). ext3
554 * will do this, as well as the blockdev mapping.
555 * try_to_release_page() will discover that cleanness and will
556 * drop the buffers and mark the page clean - it can be freed.
557 *
558 * Rarely, pages can have buffers and no ->mapping. These are
559 * the pages which were not successfully invalidated in
560 * truncate_complete_page(). We try to drop those buffers here
561 * and if that worked, and the page is no longer mapped into
562 * process address space (page_count == 1) it can be freed.
563 * Otherwise, leave the page on the LRU so it is swappable.
564 */
565 if (PagePrivate(page)) {
566 if (!try_to_release_page(page, sc->gfp_mask))
567 goto activate_locked;
568 if (!mapping && page_count(page) == 1)
569 goto free_it;
570 }
571
Nick Piggin28e4d962006-09-25 23:31:23 -0700572 if (!mapping || !remove_mapping(mapping, page))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800573 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574
575free_it:
576 unlock_page(page);
Andrew Morton05ff5132006-03-22 00:08:20 -0800577 nr_reclaimed++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 if (!pagevec_add(&freed_pvec, page))
579 __pagevec_release_nonlru(&freed_pvec);
580 continue;
581
582activate_locked:
583 SetPageActive(page);
584 pgactivate++;
585keep_locked:
586 unlock_page(page);
587keep:
588 list_add(&page->lru, &ret_pages);
Nick Piggin725d7042006-09-25 23:30:55 -0700589 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 }
591 list_splice(&ret_pages, page_list);
592 if (pagevec_count(&freed_pvec))
593 __pagevec_release_nonlru(&freed_pvec);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700594 count_vm_events(PGACTIVATE, pgactivate);
Andrew Morton05ff5132006-03-22 00:08:20 -0800595 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596}
597
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800598/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 * zone->lru_lock is heavily contended. Some of the functions that
600 * shrink the lists perform better by taking out a batch of pages
601 * and working on them outside the LRU lock.
602 *
603 * For pagecache intensive workloads, this function is the hottest
604 * spot in the kernel (apart from copy_*_user functions).
605 *
606 * Appropriate locks must be held before calling this function.
607 *
608 * @nr_to_scan: The number of pages to look through on the list.
609 * @src: The LRU list to pull pages off.
610 * @dst: The temp list to put pages on to.
611 * @scanned: The number of pages that were scanned.
612 *
613 * returns how many pages were moved onto *@dst.
614 */
Andrew Morton69e05942006-03-22 00:08:19 -0800615static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
616 struct list_head *src, struct list_head *dst,
617 unsigned long *scanned)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618{
Andrew Morton69e05942006-03-22 00:08:19 -0800619 unsigned long nr_taken = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620 struct page *page;
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800621 unsigned long scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800623 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800624 struct list_head *target;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 page = lru_to_page(src);
626 prefetchw_prev_lru_page(page, src, flags);
627
Nick Piggin725d7042006-09-25 23:30:55 -0700628 VM_BUG_ON(!PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800629
Nick Piggin053837f2006-01-18 17:42:27 -0800630 list_del(&page->lru);
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800631 target = src;
632 if (likely(get_page_unless_zero(page))) {
Nick Piggin053837f2006-01-18 17:42:27 -0800633 /*
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800634 * Be careful not to clear PageLRU until after we're
635 * sure the page is not being freed elsewhere -- the
636 * page release code relies on it.
Nick Piggin053837f2006-01-18 17:42:27 -0800637 */
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800638 ClearPageLRU(page);
639 target = dst;
640 nr_taken++;
641 } /* else it is being freed elsewhere */
Nick Piggin46453a62006-03-22 00:07:58 -0800642
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800643 list_add(&page->lru, target);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644 }
645
646 *scanned = scan;
647 return nr_taken;
648}
649
650/*
Andrew Morton1742f192006-03-22 00:08:21 -0800651 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
652 * of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653 */
Andrew Morton1742f192006-03-22 00:08:21 -0800654static unsigned long shrink_inactive_list(unsigned long max_scan,
655 struct zone *zone, struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656{
657 LIST_HEAD(page_list);
658 struct pagevec pvec;
Andrew Morton69e05942006-03-22 00:08:19 -0800659 unsigned long nr_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800660 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661
662 pagevec_init(&pvec, 1);
663
664 lru_add_drain();
665 spin_lock_irq(&zone->lru_lock);
Andrew Morton69e05942006-03-22 00:08:19 -0800666 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 struct page *page;
Andrew Morton69e05942006-03-22 00:08:19 -0800668 unsigned long nr_taken;
669 unsigned long nr_scan;
670 unsigned long nr_freed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671
672 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
673 &zone->inactive_list,
674 &page_list, &nr_scan);
675 zone->nr_inactive -= nr_taken;
676 zone->pages_scanned += nr_scan;
677 spin_unlock_irq(&zone->lru_lock);
678
Andrew Morton69e05942006-03-22 00:08:19 -0800679 nr_scanned += nr_scan;
Andrew Morton1742f192006-03-22 00:08:21 -0800680 nr_freed = shrink_page_list(&page_list, sc);
Andrew Morton05ff5132006-03-22 00:08:20 -0800681 nr_reclaimed += nr_freed;
Nick Piggina74609f2006-01-06 00:11:20 -0800682 local_irq_disable();
683 if (current_is_kswapd()) {
Christoph Lameterf8891e52006-06-30 01:55:45 -0700684 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
685 __count_vm_events(KSWAPD_STEAL, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -0800686 } else
Christoph Lameterf8891e52006-06-30 01:55:45 -0700687 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
688 __count_vm_events(PGACTIVATE, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -0800689
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800690 if (nr_taken == 0)
691 goto done;
692
Nick Piggina74609f2006-01-06 00:11:20 -0800693 spin_lock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 /*
695 * Put back any unfreeable pages.
696 */
697 while (!list_empty(&page_list)) {
698 page = lru_to_page(&page_list);
Nick Piggin725d7042006-09-25 23:30:55 -0700699 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800700 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701 list_del(&page->lru);
702 if (PageActive(page))
703 add_page_to_active_list(zone, page);
704 else
705 add_page_to_inactive_list(zone, page);
706 if (!pagevec_add(&pvec, page)) {
707 spin_unlock_irq(&zone->lru_lock);
708 __pagevec_release(&pvec);
709 spin_lock_irq(&zone->lru_lock);
710 }
711 }
Andrew Morton69e05942006-03-22 00:08:19 -0800712 } while (nr_scanned < max_scan);
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800713 spin_unlock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714done:
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800715 local_irq_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 pagevec_release(&pvec);
Andrew Morton05ff5132006-03-22 00:08:20 -0800717 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718}
719
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700720static inline int zone_is_near_oom(struct zone *zone)
721{
722 return zone->pages_scanned >= (zone->nr_active + zone->nr_inactive)*3;
723}
724
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725/*
726 * This moves pages from the active list to the inactive list.
727 *
728 * We move them the other way if the page is referenced by one or more
729 * processes, from rmap.
730 *
731 * If the pages are mostly unmapped, the processing is fast and it is
732 * appropriate to hold zone->lru_lock across the whole operation. But if
733 * the pages are mapped, the processing is slow (page_referenced()) so we
734 * should drop zone->lru_lock around each page. It's impossible to balance
735 * this, so instead we remove the pages from the LRU while processing them.
736 * It is safe to rely on PG_active against the non-LRU pages in here because
737 * nobody will play with that bit on a non-LRU page.
738 *
739 * The downside is that we have to touch page->_count against each page.
740 * But we had to alter page->flags anyway.
741 */
Andrew Morton1742f192006-03-22 00:08:21 -0800742static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
743 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744{
Andrew Morton69e05942006-03-22 00:08:19 -0800745 unsigned long pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746 int pgdeactivate = 0;
Andrew Morton69e05942006-03-22 00:08:19 -0800747 unsigned long pgscanned;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 LIST_HEAD(l_hold); /* The pages which were snipped off */
749 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
750 LIST_HEAD(l_active); /* Pages to go onto the active_list */
751 struct page *page;
752 struct pagevec pvec;
753 int reclaim_mapped = 0;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800754
Christoph Lameter6e5ef1a2006-03-22 00:08:45 -0800755 if (sc->may_swap) {
Christoph Lameter2903fb12006-02-11 17:55:55 -0800756 long mapped_ratio;
757 long distress;
758 long swap_tendency;
759
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700760 if (zone_is_near_oom(zone))
761 goto force_reclaim_mapped;
762
Christoph Lameter2903fb12006-02-11 17:55:55 -0800763 /*
764 * `distress' is a measure of how much trouble we're having
765 * reclaiming pages. 0 -> no problems. 100 -> great trouble.
766 */
767 distress = 100 >> zone->prev_priority;
768
769 /*
770 * The point of this algorithm is to decide when to start
771 * reclaiming mapped memory instead of just pagecache. Work out
772 * how much memory
773 * is mapped.
774 */
Christoph Lameterf3dbd342006-06-30 01:55:36 -0700775 mapped_ratio = ((global_page_state(NR_FILE_MAPPED) +
776 global_page_state(NR_ANON_PAGES)) * 100) /
Christoph Lameterbf02cf42006-06-30 01:55:36 -0700777 vm_total_pages;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800778
779 /*
780 * Now decide how much we really want to unmap some pages. The
781 * mapped ratio is downgraded - just because there's a lot of
782 * mapped memory doesn't necessarily mean that page reclaim
783 * isn't succeeding.
784 *
785 * The distress ratio is important - we don't want to start
786 * going oom.
787 *
788 * A 100% value of vm_swappiness overrides this algorithm
789 * altogether.
790 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -0700791 swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800792
793 /*
794 * Now use this metric to decide whether to start moving mapped
795 * memory onto the inactive list.
796 */
797 if (swap_tendency >= 100)
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700798force_reclaim_mapped:
Christoph Lameter2903fb12006-02-11 17:55:55 -0800799 reclaim_mapped = 1;
800 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801
802 lru_add_drain();
803 spin_lock_irq(&zone->lru_lock);
804 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
805 &l_hold, &pgscanned);
806 zone->pages_scanned += pgscanned;
807 zone->nr_active -= pgmoved;
808 spin_unlock_irq(&zone->lru_lock);
809
Linus Torvalds1da177e2005-04-16 15:20:36 -0700810 while (!list_empty(&l_hold)) {
811 cond_resched();
812 page = lru_to_page(&l_hold);
813 list_del(&page->lru);
814 if (page_mapped(page)) {
815 if (!reclaim_mapped ||
816 (total_swap_pages == 0 && PageAnon(page)) ||
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800817 page_referenced(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 list_add(&page->lru, &l_active);
819 continue;
820 }
821 }
822 list_add(&page->lru, &l_inactive);
823 }
824
825 pagevec_init(&pvec, 1);
826 pgmoved = 0;
827 spin_lock_irq(&zone->lru_lock);
828 while (!list_empty(&l_inactive)) {
829 page = lru_to_page(&l_inactive);
830 prefetchw_prev_lru_page(page, &l_inactive, flags);
Nick Piggin725d7042006-09-25 23:30:55 -0700831 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800832 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700833 VM_BUG_ON(!PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -0800834 ClearPageActive(page);
835
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 list_move(&page->lru, &zone->inactive_list);
837 pgmoved++;
838 if (!pagevec_add(&pvec, page)) {
839 zone->nr_inactive += pgmoved;
840 spin_unlock_irq(&zone->lru_lock);
841 pgdeactivate += pgmoved;
842 pgmoved = 0;
843 if (buffer_heads_over_limit)
844 pagevec_strip(&pvec);
845 __pagevec_release(&pvec);
846 spin_lock_irq(&zone->lru_lock);
847 }
848 }
849 zone->nr_inactive += pgmoved;
850 pgdeactivate += pgmoved;
851 if (buffer_heads_over_limit) {
852 spin_unlock_irq(&zone->lru_lock);
853 pagevec_strip(&pvec);
854 spin_lock_irq(&zone->lru_lock);
855 }
856
857 pgmoved = 0;
858 while (!list_empty(&l_active)) {
859 page = lru_to_page(&l_active);
860 prefetchw_prev_lru_page(page, &l_active, flags);
Nick Piggin725d7042006-09-25 23:30:55 -0700861 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800862 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700863 VM_BUG_ON(!PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 list_move(&page->lru, &zone->active_list);
865 pgmoved++;
866 if (!pagevec_add(&pvec, page)) {
867 zone->nr_active += pgmoved;
868 pgmoved = 0;
869 spin_unlock_irq(&zone->lru_lock);
870 __pagevec_release(&pvec);
871 spin_lock_irq(&zone->lru_lock);
872 }
873 }
874 zone->nr_active += pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875
Christoph Lameterf8891e52006-06-30 01:55:45 -0700876 __count_zone_vm_events(PGREFILL, zone, pgscanned);
877 __count_vm_events(PGDEACTIVATE, pgdeactivate);
878 spin_unlock_irq(&zone->lru_lock);
Nick Piggina74609f2006-01-06 00:11:20 -0800879
880 pagevec_release(&pvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881}
882
883/*
884 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
885 */
Andrew Morton05ff5132006-03-22 00:08:20 -0800886static unsigned long shrink_zone(int priority, struct zone *zone,
887 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888{
889 unsigned long nr_active;
890 unsigned long nr_inactive;
Christoph Lameter86959492006-03-22 00:08:18 -0800891 unsigned long nr_to_scan;
Andrew Morton05ff5132006-03-22 00:08:20 -0800892 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893
Martin Hicks53e9a612005-09-03 15:54:51 -0700894 atomic_inc(&zone->reclaim_in_progress);
895
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896 /*
897 * Add one to `nr_to_scan' just to make sure that the kernel will
898 * slowly sift through the active list.
899 */
Christoph Lameter86959492006-03-22 00:08:18 -0800900 zone->nr_scan_active += (zone->nr_active >> priority) + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 nr_active = zone->nr_scan_active;
902 if (nr_active >= sc->swap_cluster_max)
903 zone->nr_scan_active = 0;
904 else
905 nr_active = 0;
906
Christoph Lameter86959492006-03-22 00:08:18 -0800907 zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 nr_inactive = zone->nr_scan_inactive;
909 if (nr_inactive >= sc->swap_cluster_max)
910 zone->nr_scan_inactive = 0;
911 else
912 nr_inactive = 0;
913
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914 while (nr_active || nr_inactive) {
915 if (nr_active) {
Christoph Lameter86959492006-03-22 00:08:18 -0800916 nr_to_scan = min(nr_active,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917 (unsigned long)sc->swap_cluster_max);
Christoph Lameter86959492006-03-22 00:08:18 -0800918 nr_active -= nr_to_scan;
Andrew Morton1742f192006-03-22 00:08:21 -0800919 shrink_active_list(nr_to_scan, zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 }
921
922 if (nr_inactive) {
Christoph Lameter86959492006-03-22 00:08:18 -0800923 nr_to_scan = min(nr_inactive,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700924 (unsigned long)sc->swap_cluster_max);
Christoph Lameter86959492006-03-22 00:08:18 -0800925 nr_inactive -= nr_to_scan;
Andrew Morton1742f192006-03-22 00:08:21 -0800926 nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
927 sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928 }
929 }
930
931 throttle_vm_writeout();
Martin Hicks53e9a612005-09-03 15:54:51 -0700932
933 atomic_dec(&zone->reclaim_in_progress);
Andrew Morton05ff5132006-03-22 00:08:20 -0800934 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935}
936
937/*
938 * This is the direct reclaim path, for page-allocating processes. We only
939 * try to reclaim pages from zones which will satisfy the caller's allocation
940 * request.
941 *
942 * We reclaim from a zone even if that zone is over pages_high. Because:
943 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
944 * allocation or
945 * b) The zones may be over pages_high but they must go *over* pages_high to
946 * satisfy the `incremental min' zone defense algorithm.
947 *
948 * Returns the number of reclaimed pages.
949 *
950 * If a zone is deemed to be full of pinned pages then just give it a light
951 * scan then give up on it.
952 */
Andrew Morton1742f192006-03-22 00:08:21 -0800953static unsigned long shrink_zones(int priority, struct zone **zones,
Andrew Morton05ff5132006-03-22 00:08:20 -0800954 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700955{
Andrew Morton05ff5132006-03-22 00:08:20 -0800956 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957 int i;
958
Nick Piggin408d8542006-09-25 23:31:27 -0700959 sc->all_unreclaimable = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960 for (i = 0; zones[i] != NULL; i++) {
961 struct zone *zone = zones[i];
962
Con Kolivasf3fe6512006-01-06 00:11:15 -0800963 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700964 continue;
965
Paul Jackson9bf22292005-09-06 15:18:12 -0700966 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967 continue;
968
Christoph Lameter86959492006-03-22 00:08:18 -0800969 zone->temp_priority = priority;
970 if (zone->prev_priority > priority)
971 zone->prev_priority = priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
Christoph Lameter86959492006-03-22 00:08:18 -0800973 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 continue; /* Let kswapd poll it */
975
Nick Piggin408d8542006-09-25 23:31:27 -0700976 sc->all_unreclaimable = 0;
977
Andrew Morton05ff5132006-03-22 00:08:20 -0800978 nr_reclaimed += shrink_zone(priority, zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979 }
Andrew Morton05ff5132006-03-22 00:08:20 -0800980 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700981}
982
983/*
984 * This is the main entry point to direct page reclaim.
985 *
986 * If a full scan of the inactive list fails to free enough memory then we
987 * are "out of memory" and something needs to be killed.
988 *
989 * If the caller is !__GFP_FS then the probability of a failure is reasonably
990 * high - the zone may be full of dirty or under-writeback pages, which this
991 * caller can't do much about. We kick pdflush and take explicit naps in the
992 * hope that some of these pages can be written. But if the allocating task
993 * holds filesystem locks which prevent writeout this might not work, and the
994 * allocation attempt will fail.
995 */
Andrew Morton69e05942006-03-22 00:08:19 -0800996unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997{
998 int priority;
999 int ret = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001000 unsigned long total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001001 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002 struct reclaim_state *reclaim_state = current->reclaim_state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001003 unsigned long lru_pages = 0;
1004 int i;
Andrew Morton179e9632006-03-22 00:08:18 -08001005 struct scan_control sc = {
1006 .gfp_mask = gfp_mask,
1007 .may_writepage = !laptop_mode,
1008 .swap_cluster_max = SWAP_CLUSTER_MAX,
1009 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001010 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001011 };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
Christoph Lameterf8891e52006-06-30 01:55:45 -07001013 count_vm_event(ALLOCSTALL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014
1015 for (i = 0; zones[i] != NULL; i++) {
1016 struct zone *zone = zones[i];
1017
Paul Jackson9bf22292005-09-06 15:18:12 -07001018 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019 continue;
1020
1021 zone->temp_priority = DEF_PRIORITY;
1022 lru_pages += zone->nr_active + zone->nr_inactive;
1023 }
1024
1025 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026 sc.nr_scanned = 0;
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001027 if (!priority)
1028 disable_swap_token();
Andrew Morton1742f192006-03-22 00:08:21 -08001029 nr_reclaimed += shrink_zones(priority, zones, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
1031 if (reclaim_state) {
Andrew Morton05ff5132006-03-22 00:08:20 -08001032 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 reclaim_state->reclaimed_slab = 0;
1034 }
1035 total_scanned += sc.nr_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001036 if (nr_reclaimed >= sc.swap_cluster_max) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 ret = 1;
1038 goto out;
1039 }
1040
1041 /*
1042 * Try to write back as many pages as we just scanned. This
1043 * tends to cause slow streaming writers to write data to the
1044 * disk smoothly, at the dirtying rate, which is nice. But
1045 * that's undesirable in laptop mode, where we *want* lumpy
1046 * writeout. So in laptop mode, write out the whole world.
1047 */
Andrew Morton179e9632006-03-22 00:08:18 -08001048 if (total_scanned > sc.swap_cluster_max +
1049 sc.swap_cluster_max / 2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -07001050 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051 sc.may_writepage = 1;
1052 }
1053
1054 /* Take a nap, wait for some writeback to complete */
1055 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
1056 blk_congestion_wait(WRITE, HZ/10);
1057 }
Nick Piggin408d8542006-09-25 23:31:27 -07001058 /* top priority shrink_caches still had more to do? don't OOM, then */
1059 if (!sc.all_unreclaimable)
1060 ret = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061out:
1062 for (i = 0; zones[i] != 0; i++) {
1063 struct zone *zone = zones[i];
1064
Paul Jackson9bf22292005-09-06 15:18:12 -07001065 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 continue;
1067
1068 zone->prev_priority = zone->temp_priority;
1069 }
1070 return ret;
1071}
1072
1073/*
1074 * For kswapd, balance_pgdat() will work across all this node's zones until
1075 * they are all at pages_high.
1076 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 * Returns the number of pages which were actually freed.
1078 *
1079 * There is special handling here for zones which are full of pinned pages.
1080 * This can happen if the pages are all mlocked, or if they are all used by
1081 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1082 * What we do is to detect the case where all pages in the zone have been
1083 * scanned twice and there has been zero successful reclaim. Mark the zone as
1084 * dead and from now on, only perform a short scan. Basically we're polling
1085 * the zone for when the problem goes away.
1086 *
1087 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1088 * zones which have free_pages > pages_high, but once a zone is found to have
1089 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1090 * of the number of free pages in the lower zones. This interoperates with
1091 * the page allocator fallback scheme to ensure that aging of pages is balanced
1092 * across the zones.
1093 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001094static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 int all_zones_ok;
1097 int priority;
1098 int i;
Andrew Morton69e05942006-03-22 00:08:19 -08001099 unsigned long total_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001100 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 struct reclaim_state *reclaim_state = current->reclaim_state;
Andrew Morton179e9632006-03-22 00:08:18 -08001102 struct scan_control sc = {
1103 .gfp_mask = GFP_KERNEL,
1104 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001105 .swap_cluster_max = SWAP_CLUSTER_MAX,
1106 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001107 };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108
1109loop_again:
1110 total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001111 nr_reclaimed = 0;
Christoph Lameterc0bbbc72006-06-11 15:22:26 -07001112 sc.may_writepage = !laptop_mode;
Christoph Lameterf8891e52006-06-30 01:55:45 -07001113 count_vm_event(PAGEOUTRUN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114
1115 for (i = 0; i < pgdat->nr_zones; i++) {
1116 struct zone *zone = pgdat->node_zones + i;
1117
1118 zone->temp_priority = DEF_PRIORITY;
1119 }
1120
1121 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1122 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1123 unsigned long lru_pages = 0;
1124
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001125 /* The swap token gets in the way of swapout... */
1126 if (!priority)
1127 disable_swap_token();
1128
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129 all_zones_ok = 1;
1130
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001131 /*
1132 * Scan in the highmem->dma direction for the highest
1133 * zone which needs scanning
1134 */
1135 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1136 struct zone *zone = pgdat->node_zones + i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001138 if (!populated_zone(zone))
1139 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001141 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1142 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001144 if (!zone_watermark_ok(zone, order, zone->pages_high,
1145 0, 0)) {
1146 end_zone = i;
1147 goto scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001150 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001151scan:
1152 for (i = 0; i <= end_zone; i++) {
1153 struct zone *zone = pgdat->node_zones + i;
1154
1155 lru_pages += zone->nr_active + zone->nr_inactive;
1156 }
1157
1158 /*
1159 * Now scan the zone in the dma->highmem direction, stopping
1160 * at the last zone which needs scanning.
1161 *
1162 * We do this because the page allocator works in the opposite
1163 * direction. This prevents the page allocator from allocating
1164 * pages behind kswapd's direction of progress, which would
1165 * cause too much scanning of the lower zones.
1166 */
1167 for (i = 0; i <= end_zone; i++) {
1168 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001169 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170
Con Kolivasf3fe6512006-01-06 00:11:15 -08001171 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172 continue;
1173
1174 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1175 continue;
1176
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001177 if (!zone_watermark_ok(zone, order, zone->pages_high,
1178 end_zone, 0))
1179 all_zones_ok = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 zone->temp_priority = priority;
1181 if (zone->prev_priority > priority)
1182 zone->prev_priority = priority;
1183 sc.nr_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001184 nr_reclaimed += shrink_zone(priority, zone, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001186 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1187 lru_pages);
Andrew Morton05ff5132006-03-22 00:08:20 -08001188 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001189 total_scanned += sc.nr_scanned;
1190 if (zone->all_unreclaimable)
1191 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001192 if (nr_slab == 0 && zone->pages_scanned >=
Nick Piggin4ff1ffb2006-09-25 23:31:28 -07001193 (zone->nr_active + zone->nr_inactive) * 6)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194 zone->all_unreclaimable = 1;
1195 /*
1196 * If we've done a decent amount of scanning and
1197 * the reclaim ratio is low, start doing writepage
1198 * even in laptop mode
1199 */
1200 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
Andrew Morton05ff5132006-03-22 00:08:20 -08001201 total_scanned > nr_reclaimed + nr_reclaimed / 2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202 sc.may_writepage = 1;
1203 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 if (all_zones_ok)
1205 break; /* kswapd: all done */
1206 /*
1207 * OK, kswapd is getting into trouble. Take a nap, then take
1208 * another pass across the zones.
1209 */
1210 if (total_scanned && priority < DEF_PRIORITY - 2)
1211 blk_congestion_wait(WRITE, HZ/10);
1212
1213 /*
1214 * We do this so kswapd doesn't build up large priorities for
1215 * example when it is freeing in parallel with allocators. It
1216 * matches the direct reclaim path behaviour in terms of impact
1217 * on zone->*_priority.
1218 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001219 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001220 break;
1221 }
1222out:
1223 for (i = 0; i < pgdat->nr_zones; i++) {
1224 struct zone *zone = pgdat->node_zones + i;
1225
1226 zone->prev_priority = zone->temp_priority;
1227 }
1228 if (!all_zones_ok) {
1229 cond_resched();
1230 goto loop_again;
1231 }
1232
Andrew Morton05ff5132006-03-22 00:08:20 -08001233 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234}
1235
1236/*
1237 * The background pageout daemon, started as a kernel thread
1238 * from the init process.
1239 *
1240 * This basically trickles out pages so that we have _some_
1241 * free memory available even if there is no other activity
1242 * that frees anything up. This is needed for things like routing
1243 * etc, where we otherwise might have all activity going on in
1244 * asynchronous contexts that cannot page things out.
1245 *
1246 * If there are applications that are active memory-allocators
1247 * (most normal use), this basically shouldn't matter.
1248 */
1249static int kswapd(void *p)
1250{
1251 unsigned long order;
1252 pg_data_t *pgdat = (pg_data_t*)p;
1253 struct task_struct *tsk = current;
1254 DEFINE_WAIT(wait);
1255 struct reclaim_state reclaim_state = {
1256 .reclaimed_slab = 0,
1257 };
1258 cpumask_t cpumask;
1259
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 cpumask = node_to_cpumask(pgdat->node_id);
1261 if (!cpus_empty(cpumask))
1262 set_cpus_allowed(tsk, cpumask);
1263 current->reclaim_state = &reclaim_state;
1264
1265 /*
1266 * Tell the memory management that we're a "memory allocator",
1267 * and that if we need more memory we should get access to it
1268 * regardless (see "__alloc_pages()"). "kswapd" should
1269 * never get caught in the normal page freeing logic.
1270 *
1271 * (Kswapd normally doesn't need memory anyway, but sometimes
1272 * you need a small amount of memory in order to be able to
1273 * page out something else, and this flag essentially protects
1274 * us from recursively trying to free more memory as we're
1275 * trying to free the first piece of memory in the first place).
1276 */
Christoph Lameter930d9152006-01-08 01:00:47 -08001277 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278
1279 order = 0;
1280 for ( ; ; ) {
1281 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001282
1283 try_to_freeze();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001284
1285 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1286 new_order = pgdat->kswapd_max_order;
1287 pgdat->kswapd_max_order = 0;
1288 if (order < new_order) {
1289 /*
1290 * Don't sleep if someone wants a larger 'order'
1291 * allocation
1292 */
1293 order = new_order;
1294 } else {
1295 schedule();
1296 order = pgdat->kswapd_max_order;
1297 }
1298 finish_wait(&pgdat->kswapd_wait, &wait);
1299
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001300 balance_pgdat(pgdat, order);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 }
1302 return 0;
1303}
1304
1305/*
1306 * A zone is low on free memory, so wake its kswapd task to service it.
1307 */
1308void wakeup_kswapd(struct zone *zone, int order)
1309{
1310 pg_data_t *pgdat;
1311
Con Kolivasf3fe6512006-01-06 00:11:15 -08001312 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001313 return;
1314
1315 pgdat = zone->zone_pgdat;
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001316 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317 return;
1318 if (pgdat->kswapd_max_order < order)
1319 pgdat->kswapd_max_order = order;
Paul Jackson9bf22292005-09-06 15:18:12 -07001320 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001322 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001324 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325}
1326
1327#ifdef CONFIG_PM
1328/*
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001329 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1330 * from LRU lists system-wide, for given pass and priority, and returns the
1331 * number of reclaimed pages
1332 *
1333 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1334 */
1335static unsigned long shrink_all_zones(unsigned long nr_pages, int pass,
1336 int prio, struct scan_control *sc)
1337{
1338 struct zone *zone;
1339 unsigned long nr_to_scan, ret = 0;
1340
1341 for_each_zone(zone) {
1342
1343 if (!populated_zone(zone))
1344 continue;
1345
1346 if (zone->all_unreclaimable && prio != DEF_PRIORITY)
1347 continue;
1348
1349 /* For pass = 0 we don't shrink the active list */
1350 if (pass > 0) {
1351 zone->nr_scan_active += (zone->nr_active >> prio) + 1;
1352 if (zone->nr_scan_active >= nr_pages || pass > 3) {
1353 zone->nr_scan_active = 0;
1354 nr_to_scan = min(nr_pages, zone->nr_active);
1355 shrink_active_list(nr_to_scan, zone, sc);
1356 }
1357 }
1358
1359 zone->nr_scan_inactive += (zone->nr_inactive >> prio) + 1;
1360 if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
1361 zone->nr_scan_inactive = 0;
1362 nr_to_scan = min(nr_pages, zone->nr_inactive);
1363 ret += shrink_inactive_list(nr_to_scan, zone, sc);
1364 if (ret >= nr_pages)
1365 return ret;
1366 }
1367 }
1368
1369 return ret;
1370}
1371
1372/*
1373 * Try to free `nr_pages' of memory, system-wide, and return the number of
1374 * freed pages.
1375 *
1376 * Rather than trying to age LRUs the aim is to preserve the overall
1377 * LRU order by reclaiming preferentially
1378 * inactive > active > active referenced > active mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 */
Andrew Morton69e05942006-03-22 00:08:19 -08001380unsigned long shrink_all_memory(unsigned long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381{
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001382 unsigned long lru_pages, nr_slab;
Andrew Morton69e05942006-03-22 00:08:19 -08001383 unsigned long ret = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001384 int pass;
1385 struct reclaim_state reclaim_state;
1386 struct zone *zone;
1387 struct scan_control sc = {
1388 .gfp_mask = GFP_KERNEL,
1389 .may_swap = 0,
1390 .swap_cluster_max = nr_pages,
1391 .may_writepage = 1,
1392 .swappiness = vm_swappiness,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001393 };
1394
1395 current->reclaim_state = &reclaim_state;
Andrew Morton69e05942006-03-22 00:08:19 -08001396
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001397 lru_pages = 0;
1398 for_each_zone(zone)
1399 lru_pages += zone->nr_active + zone->nr_inactive;
1400
Christoph Lameter972d1a72006-09-25 23:31:51 -07001401 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001402 /* If slab caches are huge, it's better to hit them first */
1403 while (nr_slab >= lru_pages) {
1404 reclaim_state.reclaimed_slab = 0;
1405 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1406 if (!reclaim_state.reclaimed_slab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 break;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001408
1409 ret += reclaim_state.reclaimed_slab;
1410 if (ret >= nr_pages)
1411 goto out;
1412
1413 nr_slab -= reclaim_state.reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001415
1416 /*
1417 * We try to shrink LRUs in 5 passes:
1418 * 0 = Reclaim from inactive_list only
1419 * 1 = Reclaim from active list but don't reclaim mapped
1420 * 2 = 2nd pass of type 1
1421 * 3 = Reclaim mapped (normal reclaim)
1422 * 4 = 2nd pass of type 3
1423 */
1424 for (pass = 0; pass < 5; pass++) {
1425 int prio;
1426
1427 /* Needed for shrinking slab caches later on */
1428 if (!lru_pages)
1429 for_each_zone(zone) {
1430 lru_pages += zone->nr_active;
1431 lru_pages += zone->nr_inactive;
1432 }
1433
1434 /* Force reclaiming mapped pages in the passes #3 and #4 */
1435 if (pass > 2) {
1436 sc.may_swap = 1;
1437 sc.swappiness = 100;
1438 }
1439
1440 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
1441 unsigned long nr_to_scan = nr_pages - ret;
1442
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001443 sc.nr_scanned = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001444 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
1445 if (ret >= nr_pages)
1446 goto out;
1447
1448 reclaim_state.reclaimed_slab = 0;
1449 shrink_slab(sc.nr_scanned, sc.gfp_mask, lru_pages);
1450 ret += reclaim_state.reclaimed_slab;
1451 if (ret >= nr_pages)
1452 goto out;
1453
1454 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
1455 blk_congestion_wait(WRITE, HZ / 10);
1456 }
1457
1458 lru_pages = 0;
Rafael J. Wysocki248a0302006-03-22 00:09:04 -08001459 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001460
1461 /*
1462 * If ret = 0, we could not shrink LRUs, but there may be something
1463 * in slab caches
1464 */
1465 if (!ret)
1466 do {
1467 reclaim_state.reclaimed_slab = 0;
1468 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1469 ret += reclaim_state.reclaimed_slab;
1470 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
1471
1472out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 current->reclaim_state = NULL;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001474
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475 return ret;
1476}
1477#endif
1478
1479#ifdef CONFIG_HOTPLUG_CPU
1480/* It's optimal to keep kswapds on the same CPUs as their memory, but
1481 not required for correctness. So if the last cpu in a node goes
1482 away, we get changed to run anywhere: as the first one comes back,
1483 restore their cpu bindings. */
Chandra Seetharaman9c7b2162006-06-27 02:54:07 -07001484static int __devinit cpu_callback(struct notifier_block *nfb,
Andrew Morton69e05942006-03-22 00:08:19 -08001485 unsigned long action, void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486{
1487 pg_data_t *pgdat;
1488 cpumask_t mask;
1489
1490 if (action == CPU_ONLINE) {
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -08001491 for_each_online_pgdat(pgdat) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492 mask = node_to_cpumask(pgdat->node_id);
1493 if (any_online_cpu(mask) != NR_CPUS)
1494 /* One of our CPUs online: restore mask */
1495 set_cpus_allowed(pgdat->kswapd, mask);
1496 }
1497 }
1498 return NOTIFY_OK;
1499}
1500#endif /* CONFIG_HOTPLUG_CPU */
1501
Yasunori Goto3218ae12006-06-27 02:53:33 -07001502/*
1503 * This kswapd start function will be called by init and node-hot-add.
1504 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
1505 */
1506int kswapd_run(int nid)
1507{
1508 pg_data_t *pgdat = NODE_DATA(nid);
1509 int ret = 0;
1510
1511 if (pgdat->kswapd)
1512 return 0;
1513
1514 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
1515 if (IS_ERR(pgdat->kswapd)) {
1516 /* failure at boot is fatal */
1517 BUG_ON(system_state == SYSTEM_BOOTING);
1518 printk("Failed to start kswapd on node %d\n",nid);
1519 ret = -1;
1520 }
1521 return ret;
1522}
1523
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524static int __init kswapd_init(void)
1525{
Yasunori Goto3218ae12006-06-27 02:53:33 -07001526 int nid;
Andrew Morton69e05942006-03-22 00:08:19 -08001527
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 swap_setup();
Yasunori Goto3218ae12006-06-27 02:53:33 -07001529 for_each_online_node(nid)
1530 kswapd_run(nid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531 hotcpu_notifier(cpu_callback, 0);
1532 return 0;
1533}
1534
1535module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08001536
1537#ifdef CONFIG_NUMA
1538/*
1539 * Zone reclaim mode
1540 *
1541 * If non-zero call zone_reclaim when the number of free pages falls below
1542 * the watermarks.
Christoph Lameter9eeff232006-01-18 17:42:31 -08001543 */
1544int zone_reclaim_mode __read_mostly;
1545
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08001546#define RECLAIM_OFF 0
1547#define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */
1548#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
1549#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
1550
Christoph Lameter9eeff232006-01-18 17:42:31 -08001551/*
Christoph Lametera92f7122006-02-01 03:05:32 -08001552 * Priority for ZONE_RECLAIM. This determines the fraction of pages
1553 * of a node considered for each zone_reclaim. 4 scans 1/16th of
1554 * a zone.
1555 */
1556#define ZONE_RECLAIM_PRIORITY 4
1557
Christoph Lameter9eeff232006-01-18 17:42:31 -08001558/*
Christoph Lameter96146342006-07-03 00:24:13 -07001559 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
1560 * occur.
1561 */
1562int sysctl_min_unmapped_ratio = 1;
1563
1564/*
Christoph Lameter0ff38492006-09-25 23:31:52 -07001565 * If the number of slab pages in a zone grows beyond this percentage then
1566 * slab reclaim needs to occur.
1567 */
1568int sysctl_min_slab_ratio = 5;
1569
1570/*
Christoph Lameter9eeff232006-01-18 17:42:31 -08001571 * Try to free up some pages from this zone through reclaim.
1572 */
Andrew Morton179e9632006-03-22 00:08:18 -08001573static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
Christoph Lameter9eeff232006-01-18 17:42:31 -08001574{
Christoph Lameter7fb2d462006-03-22 00:08:22 -08001575 /* Minimum pages needed in order to stay on node */
Andrew Morton69e05942006-03-22 00:08:19 -08001576 const unsigned long nr_pages = 1 << order;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001577 struct task_struct *p = current;
1578 struct reclaim_state reclaim_state;
Christoph Lameter86959492006-03-22 00:08:18 -08001579 int priority;
Andrew Morton05ff5132006-03-22 00:08:20 -08001580 unsigned long nr_reclaimed = 0;
Andrew Morton179e9632006-03-22 00:08:18 -08001581 struct scan_control sc = {
1582 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
1583 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
Andrew Morton69e05942006-03-22 00:08:19 -08001584 .swap_cluster_max = max_t(unsigned long, nr_pages,
1585 SWAP_CLUSTER_MAX),
Andrew Morton179e9632006-03-22 00:08:18 -08001586 .gfp_mask = gfp_mask,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001587 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001588 };
Christoph Lameter83e33a42006-09-25 23:31:53 -07001589 unsigned long slab_reclaimable;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001590
1591 disable_swap_token();
Christoph Lameter9eeff232006-01-18 17:42:31 -08001592 cond_resched();
Christoph Lameterd4f77962006-02-24 13:04:22 -08001593 /*
1594 * We need to be able to allocate from the reserves for RECLAIM_SWAP
1595 * and we also need to be able to write out pages for RECLAIM_WRITE
1596 * and RECLAIM_SWAP.
1597 */
1598 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001599 reclaim_state.reclaimed_slab = 0;
1600 p->reclaim_state = &reclaim_state;
Christoph Lameterc84db232006-02-01 03:05:29 -08001601
Christoph Lameter0ff38492006-09-25 23:31:52 -07001602 if (zone_page_state(zone, NR_FILE_PAGES) -
1603 zone_page_state(zone, NR_FILE_MAPPED) >
1604 zone->min_unmapped_pages) {
1605 /*
1606 * Free memory by calling shrink zone with increasing
1607 * priorities until we have enough memory freed.
1608 */
1609 priority = ZONE_RECLAIM_PRIORITY;
1610 do {
1611 nr_reclaimed += shrink_zone(priority, zone, &sc);
1612 priority--;
1613 } while (priority >= 0 && nr_reclaimed < nr_pages);
1614 }
Christoph Lameterc84db232006-02-01 03:05:29 -08001615
Christoph Lameter83e33a42006-09-25 23:31:53 -07001616 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
1617 if (slab_reclaimable > zone->min_slab_pages) {
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001618 /*
Christoph Lameter7fb2d462006-03-22 00:08:22 -08001619 * shrink_slab() does not currently allow us to determine how
Christoph Lameter0ff38492006-09-25 23:31:52 -07001620 * many pages were freed in this zone. So we take the current
1621 * number of slab pages and shake the slab until it is reduced
1622 * by the same nr_pages that we used for reclaiming unmapped
1623 * pages.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001624 *
Christoph Lameter0ff38492006-09-25 23:31:52 -07001625 * Note that shrink_slab will free memory on all zones and may
1626 * take a long time.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001627 */
Christoph Lameter0ff38492006-09-25 23:31:52 -07001628 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
Christoph Lameter83e33a42006-09-25 23:31:53 -07001629 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
1630 slab_reclaimable - nr_pages)
Christoph Lameter0ff38492006-09-25 23:31:52 -07001631 ;
Christoph Lameter83e33a42006-09-25 23:31:53 -07001632
1633 /*
1634 * Update nr_reclaimed by the number of slab pages we
1635 * reclaimed from this zone.
1636 */
1637 nr_reclaimed += slab_reclaimable -
1638 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001639 }
1640
Christoph Lameter9eeff232006-01-18 17:42:31 -08001641 p->reclaim_state = NULL;
Christoph Lameterd4f77962006-02-24 13:04:22 -08001642 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
Andrew Morton05ff5132006-03-22 00:08:20 -08001643 return nr_reclaimed >= nr_pages;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001644}
Andrew Morton179e9632006-03-22 00:08:18 -08001645
1646int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
1647{
1648 cpumask_t mask;
1649 int node_id;
1650
1651 /*
Christoph Lameter0ff38492006-09-25 23:31:52 -07001652 * Zone reclaim reclaims unmapped file backed pages and
1653 * slab pages if we are over the defined limits.
Christoph Lameter34aa1332006-06-30 01:55:37 -07001654 *
Christoph Lameter96146342006-07-03 00:24:13 -07001655 * A small portion of unmapped file backed pages is needed for
1656 * file I/O otherwise pages read by file I/O will be immediately
1657 * thrown out if the zone is overallocated. So we do not reclaim
1658 * if less than a specified percentage of the zone is used by
1659 * unmapped file backed pages.
Andrew Morton179e9632006-03-22 00:08:18 -08001660 */
Christoph Lameter34aa1332006-06-30 01:55:37 -07001661 if (zone_page_state(zone, NR_FILE_PAGES) -
Christoph Lameter0ff38492006-09-25 23:31:52 -07001662 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
1663 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
1664 <= zone->min_slab_pages)
Christoph Lameter96146342006-07-03 00:24:13 -07001665 return 0;
Andrew Morton179e9632006-03-22 00:08:18 -08001666
1667 /*
1668 * Avoid concurrent zone reclaims, do not reclaim in a zone that does
1669 * not have reclaimable pages and if we should not delay the allocation
1670 * then do not scan.
1671 */
1672 if (!(gfp_mask & __GFP_WAIT) ||
1673 zone->all_unreclaimable ||
1674 atomic_read(&zone->reclaim_in_progress) > 0 ||
1675 (current->flags & PF_MEMALLOC))
1676 return 0;
1677
1678 /*
1679 * Only run zone reclaim on the local zone or on zones that do not
1680 * have associated processors. This will favor the local processor
1681 * over remote processors and spread off node memory allocations
1682 * as wide as possible.
1683 */
Christoph Lameter89fa3022006-09-25 23:31:55 -07001684 node_id = zone_to_nid(zone);
Andrew Morton179e9632006-03-22 00:08:18 -08001685 mask = node_to_cpumask(node_id);
1686 if (!cpus_empty(mask) && node_id != numa_node_id())
1687 return 0;
1688 return __zone_reclaim(zone, gfp_mask, order);
1689}
Christoph Lameter9eeff232006-01-18 17:42:31 -08001690#endif