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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
66 /* How many pages shrink_cache() should reclaim */
67 int nr_to_reclaim;
68
69 /* Ask shrink_caches, or shrink_zone to scan at this priority */
70 unsigned int priority;
71
72 /* This context's GFP mask */
73 unsigned int gfp_mask;
74
75 int may_writepage;
76
Martin Hicksbfbb38f2005-06-21 17:14:40 -070077 /* Can pages be swapped as part of reclaim? */
78 int may_swap;
79
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
81 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
82 * In this context, it doesn't matter that we scan the
83 * whole list at once. */
84 int swap_cluster_max;
85};
86
87/*
88 * The list of shrinker callbacks used by to apply pressure to
89 * ageable caches.
90 */
91struct shrinker {
92 shrinker_t shrinker;
93 struct list_head list;
94 int seeks; /* seeks to recreate an obj */
95 long nr; /* objs pending delete */
96};
97
98#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99
100#ifdef ARCH_HAS_PREFETCH
101#define prefetch_prev_lru_page(_page, _base, _field) \
102 do { \
103 if ((_page)->lru.prev != _base) { \
104 struct page *prev; \
105 \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetch(&prev->_field); \
108 } \
109 } while (0)
110#else
111#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
112#endif
113
114#ifdef ARCH_HAS_PREFETCHW
115#define prefetchw_prev_lru_page(_page, _base, _field) \
116 do { \
117 if ((_page)->lru.prev != _base) { \
118 struct page *prev; \
119 \
120 prev = lru_to_page(&(_page->lru)); \
121 prefetchw(&prev->_field); \
122 } \
123 } while (0)
124#else
125#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
126#endif
127
128/*
129 * From 0 .. 100. Higher means more swappy.
130 */
131int vm_swappiness = 60;
132static long total_memory;
133
134static LIST_HEAD(shrinker_list);
135static DECLARE_RWSEM(shrinker_rwsem);
136
137/*
138 * Add a shrinker callback to be called from the vm
139 */
140struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
141{
142 struct shrinker *shrinker;
143
144 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
145 if (shrinker) {
146 shrinker->shrinker = theshrinker;
147 shrinker->seeks = seeks;
148 shrinker->nr = 0;
149 down_write(&shrinker_rwsem);
150 list_add_tail(&shrinker->list, &shrinker_list);
151 up_write(&shrinker_rwsem);
152 }
153 return shrinker;
154}
155EXPORT_SYMBOL(set_shrinker);
156
157/*
158 * Remove one
159 */
160void remove_shrinker(struct shrinker *shrinker)
161{
162 down_write(&shrinker_rwsem);
163 list_del(&shrinker->list);
164 up_write(&shrinker_rwsem);
165 kfree(shrinker);
166}
167EXPORT_SYMBOL(remove_shrinker);
168
169#define SHRINK_BATCH 128
170/*
171 * Call the shrink functions to age shrinkable caches
172 *
173 * Here we assume it costs one seek to replace a lru page and that it also
174 * takes a seek to recreate a cache object. With this in mind we age equal
175 * percentages of the lru and ageable caches. This should balance the seeks
176 * generated by these structures.
177 *
178 * If the vm encounted mapped pages on the LRU it increase the pressure on
179 * slab to avoid swapping.
180 *
181 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
182 *
183 * `lru_pages' represents the number of on-LRU pages in all the zones which
184 * are eligible for the caller's allocation attempt. It is used for balancing
185 * slab reclaim versus page reclaim.
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700186 *
187 * Returns the number of slab objects which we shrunk.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188 */
189static int shrink_slab(unsigned long scanned, unsigned int gfp_mask,
190 unsigned long lru_pages)
191{
192 struct shrinker *shrinker;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700193 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194
195 if (scanned == 0)
196 scanned = SWAP_CLUSTER_MAX;
197
198 if (!down_read_trylock(&shrinker_rwsem))
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700199 return 1; /* Assume we'll be able to shrink next time */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
201 list_for_each_entry(shrinker, &shrinker_list, list) {
202 unsigned long long delta;
203 unsigned long total_scan;
204
205 delta = (4 * scanned) / shrinker->seeks;
206 delta *= (*shrinker->shrinker)(0, gfp_mask);
207 do_div(delta, lru_pages + 1);
208 shrinker->nr += delta;
209 if (shrinker->nr < 0)
210 shrinker->nr = LONG_MAX; /* It wrapped! */
211
212 total_scan = shrinker->nr;
213 shrinker->nr = 0;
214
215 while (total_scan >= SHRINK_BATCH) {
216 long this_scan = SHRINK_BATCH;
217 int shrink_ret;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700218 int nr_before;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700220 nr_before = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
222 if (shrink_ret == -1)
223 break;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700224 if (shrink_ret < nr_before)
225 ret += nr_before - shrink_ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 mod_page_state(slabs_scanned, this_scan);
227 total_scan -= this_scan;
228
229 cond_resched();
230 }
231
232 shrinker->nr += total_scan;
233 }
234 up_read(&shrinker_rwsem);
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700235 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236}
237
238/* Called without lock on whether page is mapped, so answer is unstable */
239static inline int page_mapping_inuse(struct page *page)
240{
241 struct address_space *mapping;
242
243 /* Page is in somebody's page tables. */
244 if (page_mapped(page))
245 return 1;
246
247 /* Be more reluctant to reclaim swapcache than pagecache */
248 if (PageSwapCache(page))
249 return 1;
250
251 mapping = page_mapping(page);
252 if (!mapping)
253 return 0;
254
255 /* File is mmap'd by somebody? */
256 return mapping_mapped(mapping);
257}
258
259static inline int is_page_cache_freeable(struct page *page)
260{
261 return page_count(page) - !!PagePrivate(page) == 2;
262}
263
264static int may_write_to_queue(struct backing_dev_info *bdi)
265{
266 if (current_is_kswapd())
267 return 1;
268 if (current_is_pdflush()) /* This is unlikely, but why not... */
269 return 1;
270 if (!bdi_write_congested(bdi))
271 return 1;
272 if (bdi == current->backing_dev_info)
273 return 1;
274 return 0;
275}
276
277/*
278 * We detected a synchronous write error writing a page out. Probably
279 * -ENOSPC. We need to propagate that into the address_space for a subsequent
280 * fsync(), msync() or close().
281 *
282 * The tricky part is that after writepage we cannot touch the mapping: nothing
283 * prevents it from being freed up. But we have a ref on the page and once
284 * that page is locked, the mapping is pinned.
285 *
286 * We're allowed to run sleeping lock_page() here because we know the caller has
287 * __GFP_FS.
288 */
289static void handle_write_error(struct address_space *mapping,
290 struct page *page, int error)
291{
292 lock_page(page);
293 if (page_mapping(page) == mapping) {
294 if (error == -ENOSPC)
295 set_bit(AS_ENOSPC, &mapping->flags);
296 else
297 set_bit(AS_EIO, &mapping->flags);
298 }
299 unlock_page(page);
300}
301
302/*
303 * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
304 */
305static pageout_t pageout(struct page *page, struct address_space *mapping)
306{
307 /*
308 * If the page is dirty, only perform writeback if that write
309 * will be non-blocking. To prevent this allocation from being
310 * stalled by pagecache activity. But note that there may be
311 * stalls if we need to run get_block(). We could test
312 * PagePrivate for that.
313 *
314 * If this process is currently in generic_file_write() against
315 * this page's queue, we can perform writeback even if that
316 * will block.
317 *
318 * If the page is swapcache, write it back even if that would
319 * block, for some throttling. This happens by accident, because
320 * swap_backing_dev_info is bust: it doesn't reflect the
321 * congestion state of the swapdevs. Easy to fix, if needed.
322 * See swapfile.c:page_queue_congested().
323 */
324 if (!is_page_cache_freeable(page))
325 return PAGE_KEEP;
326 if (!mapping) {
327 /*
328 * Some data journaling orphaned pages can have
329 * page->mapping == NULL while being dirty with clean buffers.
330 */
akpm@osdl.org323aca62005-04-16 15:24:06 -0700331 if (PagePrivate(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 if (try_to_free_buffers(page)) {
333 ClearPageDirty(page);
334 printk("%s: orphaned page\n", __FUNCTION__);
335 return PAGE_CLEAN;
336 }
337 }
338 return PAGE_KEEP;
339 }
340 if (mapping->a_ops->writepage == NULL)
341 return PAGE_ACTIVATE;
342 if (!may_write_to_queue(mapping->backing_dev_info))
343 return PAGE_KEEP;
344
345 if (clear_page_dirty_for_io(page)) {
346 int res;
347 struct writeback_control wbc = {
348 .sync_mode = WB_SYNC_NONE,
349 .nr_to_write = SWAP_CLUSTER_MAX,
350 .nonblocking = 1,
351 .for_reclaim = 1,
352 };
353
354 SetPageReclaim(page);
355 res = mapping->a_ops->writepage(page, &wbc);
356 if (res < 0)
357 handle_write_error(mapping, page, res);
358 if (res == WRITEPAGE_ACTIVATE) {
359 ClearPageReclaim(page);
360 return PAGE_ACTIVATE;
361 }
362 if (!PageWriteback(page)) {
363 /* synchronous write or broken a_ops? */
364 ClearPageReclaim(page);
365 }
366
367 return PAGE_SUCCESS;
368 }
369
370 return PAGE_CLEAN;
371}
372
373/*
374 * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
375 */
376static int shrink_list(struct list_head *page_list, struct scan_control *sc)
377{
378 LIST_HEAD(ret_pages);
379 struct pagevec freed_pvec;
380 int pgactivate = 0;
381 int reclaimed = 0;
382
383 cond_resched();
384
385 pagevec_init(&freed_pvec, 1);
386 while (!list_empty(page_list)) {
387 struct address_space *mapping;
388 struct page *page;
389 int may_enter_fs;
390 int referenced;
391
392 cond_resched();
393
394 page = lru_to_page(page_list);
395 list_del(&page->lru);
396
397 if (TestSetPageLocked(page))
398 goto keep;
399
400 BUG_ON(PageActive(page));
401
402 sc->nr_scanned++;
403 /* Double the slab pressure for mapped and swapcache pages */
404 if (page_mapped(page) || PageSwapCache(page))
405 sc->nr_scanned++;
406
407 if (PageWriteback(page))
408 goto keep_locked;
409
410 referenced = page_referenced(page, 1, sc->priority <= 0);
411 /* In active use or really unfreeable? Activate it. */
412 if (referenced && page_mapping_inuse(page))
413 goto activate_locked;
414
415#ifdef CONFIG_SWAP
416 /*
417 * Anonymous process memory has backing store?
418 * Try to allocate it some swap space here.
419 */
Martin Hicksbfbb38f2005-06-21 17:14:40 -0700420 if (PageAnon(page) && !PageSwapCache(page) && sc->may_swap) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421 if (!add_to_swap(page))
422 goto activate_locked;
423 }
424#endif /* CONFIG_SWAP */
425
426 mapping = page_mapping(page);
427 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
428 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
429
430 /*
431 * The page is mapped into the page tables of one or more
432 * processes. Try to unmap it here.
433 */
434 if (page_mapped(page) && mapping) {
435 switch (try_to_unmap(page)) {
436 case SWAP_FAIL:
437 goto activate_locked;
438 case SWAP_AGAIN:
439 goto keep_locked;
440 case SWAP_SUCCESS:
441 ; /* try to free the page below */
442 }
443 }
444
445 if (PageDirty(page)) {
446 if (referenced)
447 goto keep_locked;
448 if (!may_enter_fs)
449 goto keep_locked;
450 if (laptop_mode && !sc->may_writepage)
451 goto keep_locked;
452
453 /* Page is dirty, try to write it out here */
454 switch(pageout(page, mapping)) {
455 case PAGE_KEEP:
456 goto keep_locked;
457 case PAGE_ACTIVATE:
458 goto activate_locked;
459 case PAGE_SUCCESS:
460 if (PageWriteback(page) || PageDirty(page))
461 goto keep;
462 /*
463 * A synchronous write - probably a ramdisk. Go
464 * ahead and try to reclaim the page.
465 */
466 if (TestSetPageLocked(page))
467 goto keep;
468 if (PageDirty(page) || PageWriteback(page))
469 goto keep_locked;
470 mapping = page_mapping(page);
471 case PAGE_CLEAN:
472 ; /* try to free the page below */
473 }
474 }
475
476 /*
477 * If the page has buffers, try to free the buffer mappings
478 * associated with this page. If we succeed we try to free
479 * the page as well.
480 *
481 * We do this even if the page is PageDirty().
482 * try_to_release_page() does not perform I/O, but it is
483 * possible for a page to have PageDirty set, but it is actually
484 * clean (all its buffers are clean). This happens if the
485 * buffers were written out directly, with submit_bh(). ext3
486 * will do this, as well as the blockdev mapping.
487 * try_to_release_page() will discover that cleanness and will
488 * drop the buffers and mark the page clean - it can be freed.
489 *
490 * Rarely, pages can have buffers and no ->mapping. These are
491 * the pages which were not successfully invalidated in
492 * truncate_complete_page(). We try to drop those buffers here
493 * and if that worked, and the page is no longer mapped into
494 * process address space (page_count == 1) it can be freed.
495 * Otherwise, leave the page on the LRU so it is swappable.
496 */
497 if (PagePrivate(page)) {
498 if (!try_to_release_page(page, sc->gfp_mask))
499 goto activate_locked;
500 if (!mapping && page_count(page) == 1)
501 goto free_it;
502 }
503
504 if (!mapping)
505 goto keep_locked; /* truncate got there first */
506
507 write_lock_irq(&mapping->tree_lock);
508
509 /*
510 * The non-racy check for busy page. It is critical to check
511 * PageDirty _after_ making sure that the page is freeable and
512 * not in use by anybody. (pagecache + us == 2)
513 */
514 if (page_count(page) != 2 || PageDirty(page)) {
515 write_unlock_irq(&mapping->tree_lock);
516 goto keep_locked;
517 }
518
519#ifdef CONFIG_SWAP
520 if (PageSwapCache(page)) {
521 swp_entry_t swap = { .val = page->private };
522 __delete_from_swap_cache(page);
523 write_unlock_irq(&mapping->tree_lock);
524 swap_free(swap);
525 __put_page(page); /* The pagecache ref */
526 goto free_it;
527 }
528#endif /* CONFIG_SWAP */
529
530 __remove_from_page_cache(page);
531 write_unlock_irq(&mapping->tree_lock);
532 __put_page(page);
533
534free_it:
535 unlock_page(page);
536 reclaimed++;
537 if (!pagevec_add(&freed_pvec, page))
538 __pagevec_release_nonlru(&freed_pvec);
539 continue;
540
541activate_locked:
542 SetPageActive(page);
543 pgactivate++;
544keep_locked:
545 unlock_page(page);
546keep:
547 list_add(&page->lru, &ret_pages);
548 BUG_ON(PageLRU(page));
549 }
550 list_splice(&ret_pages, page_list);
551 if (pagevec_count(&freed_pvec))
552 __pagevec_release_nonlru(&freed_pvec);
553 mod_page_state(pgactivate, pgactivate);
554 sc->nr_reclaimed += reclaimed;
555 return reclaimed;
556}
557
558/*
559 * zone->lru_lock is heavily contended. Some of the functions that
560 * shrink the lists perform better by taking out a batch of pages
561 * and working on them outside the LRU lock.
562 *
563 * For pagecache intensive workloads, this function is the hottest
564 * spot in the kernel (apart from copy_*_user functions).
565 *
566 * Appropriate locks must be held before calling this function.
567 *
568 * @nr_to_scan: The number of pages to look through on the list.
569 * @src: The LRU list to pull pages off.
570 * @dst: The temp list to put pages on to.
571 * @scanned: The number of pages that were scanned.
572 *
573 * returns how many pages were moved onto *@dst.
574 */
575static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
576 struct list_head *dst, int *scanned)
577{
578 int nr_taken = 0;
579 struct page *page;
580 int scan = 0;
581
582 while (scan++ < nr_to_scan && !list_empty(src)) {
583 page = lru_to_page(src);
584 prefetchw_prev_lru_page(page, src, flags);
585
586 if (!TestClearPageLRU(page))
587 BUG();
588 list_del(&page->lru);
589 if (get_page_testone(page)) {
590 /*
591 * It is being freed elsewhere
592 */
593 __put_page(page);
594 SetPageLRU(page);
595 list_add(&page->lru, src);
596 continue;
597 } else {
598 list_add(&page->lru, dst);
599 nr_taken++;
600 }
601 }
602
603 *scanned = scan;
604 return nr_taken;
605}
606
607/*
608 * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
609 */
610static void shrink_cache(struct zone *zone, struct scan_control *sc)
611{
612 LIST_HEAD(page_list);
613 struct pagevec pvec;
614 int max_scan = sc->nr_to_scan;
615
616 pagevec_init(&pvec, 1);
617
618 lru_add_drain();
619 spin_lock_irq(&zone->lru_lock);
620 while (max_scan > 0) {
621 struct page *page;
622 int nr_taken;
623 int nr_scan;
624 int nr_freed;
625
626 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
627 &zone->inactive_list,
628 &page_list, &nr_scan);
629 zone->nr_inactive -= nr_taken;
630 zone->pages_scanned += nr_scan;
631 spin_unlock_irq(&zone->lru_lock);
632
633 if (nr_taken == 0)
634 goto done;
635
636 max_scan -= nr_scan;
637 if (current_is_kswapd())
638 mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
639 else
640 mod_page_state_zone(zone, pgscan_direct, nr_scan);
641 nr_freed = shrink_list(&page_list, sc);
642 if (current_is_kswapd())
643 mod_page_state(kswapd_steal, nr_freed);
644 mod_page_state_zone(zone, pgsteal, nr_freed);
645 sc->nr_to_reclaim -= nr_freed;
646
647 spin_lock_irq(&zone->lru_lock);
648 /*
649 * Put back any unfreeable pages.
650 */
651 while (!list_empty(&page_list)) {
652 page = lru_to_page(&page_list);
653 if (TestSetPageLRU(page))
654 BUG();
655 list_del(&page->lru);
656 if (PageActive(page))
657 add_page_to_active_list(zone, page);
658 else
659 add_page_to_inactive_list(zone, page);
660 if (!pagevec_add(&pvec, page)) {
661 spin_unlock_irq(&zone->lru_lock);
662 __pagevec_release(&pvec);
663 spin_lock_irq(&zone->lru_lock);
664 }
665 }
666 }
667 spin_unlock_irq(&zone->lru_lock);
668done:
669 pagevec_release(&pvec);
670}
671
672/*
673 * This moves pages from the active list to the inactive list.
674 *
675 * We move them the other way if the page is referenced by one or more
676 * processes, from rmap.
677 *
678 * If the pages are mostly unmapped, the processing is fast and it is
679 * appropriate to hold zone->lru_lock across the whole operation. But if
680 * the pages are mapped, the processing is slow (page_referenced()) so we
681 * should drop zone->lru_lock around each page. It's impossible to balance
682 * this, so instead we remove the pages from the LRU while processing them.
683 * It is safe to rely on PG_active against the non-LRU pages in here because
684 * nobody will play with that bit on a non-LRU page.
685 *
686 * The downside is that we have to touch page->_count against each page.
687 * But we had to alter page->flags anyway.
688 */
689static void
690refill_inactive_zone(struct zone *zone, struct scan_control *sc)
691{
692 int pgmoved;
693 int pgdeactivate = 0;
694 int pgscanned;
695 int nr_pages = sc->nr_to_scan;
696 LIST_HEAD(l_hold); /* The pages which were snipped off */
697 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
698 LIST_HEAD(l_active); /* Pages to go onto the active_list */
699 struct page *page;
700 struct pagevec pvec;
701 int reclaim_mapped = 0;
702 long mapped_ratio;
703 long distress;
704 long swap_tendency;
705
706 lru_add_drain();
707 spin_lock_irq(&zone->lru_lock);
708 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
709 &l_hold, &pgscanned);
710 zone->pages_scanned += pgscanned;
711 zone->nr_active -= pgmoved;
712 spin_unlock_irq(&zone->lru_lock);
713
714 /*
715 * `distress' is a measure of how much trouble we're having reclaiming
716 * pages. 0 -> no problems. 100 -> great trouble.
717 */
718 distress = 100 >> zone->prev_priority;
719
720 /*
721 * The point of this algorithm is to decide when to start reclaiming
722 * mapped memory instead of just pagecache. Work out how much memory
723 * is mapped.
724 */
725 mapped_ratio = (sc->nr_mapped * 100) / total_memory;
726
727 /*
728 * Now decide how much we really want to unmap some pages. The mapped
729 * ratio is downgraded - just because there's a lot of mapped memory
730 * doesn't necessarily mean that page reclaim isn't succeeding.
731 *
732 * The distress ratio is important - we don't want to start going oom.
733 *
734 * A 100% value of vm_swappiness overrides this algorithm altogether.
735 */
736 swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
737
738 /*
739 * Now use this metric to decide whether to start moving mapped memory
740 * onto the inactive list.
741 */
742 if (swap_tendency >= 100)
743 reclaim_mapped = 1;
744
745 while (!list_empty(&l_hold)) {
746 cond_resched();
747 page = lru_to_page(&l_hold);
748 list_del(&page->lru);
749 if (page_mapped(page)) {
750 if (!reclaim_mapped ||
751 (total_swap_pages == 0 && PageAnon(page)) ||
752 page_referenced(page, 0, sc->priority <= 0)) {
753 list_add(&page->lru, &l_active);
754 continue;
755 }
756 }
757 list_add(&page->lru, &l_inactive);
758 }
759
760 pagevec_init(&pvec, 1);
761 pgmoved = 0;
762 spin_lock_irq(&zone->lru_lock);
763 while (!list_empty(&l_inactive)) {
764 page = lru_to_page(&l_inactive);
765 prefetchw_prev_lru_page(page, &l_inactive, flags);
766 if (TestSetPageLRU(page))
767 BUG();
768 if (!TestClearPageActive(page))
769 BUG();
770 list_move(&page->lru, &zone->inactive_list);
771 pgmoved++;
772 if (!pagevec_add(&pvec, page)) {
773 zone->nr_inactive += pgmoved;
774 spin_unlock_irq(&zone->lru_lock);
775 pgdeactivate += pgmoved;
776 pgmoved = 0;
777 if (buffer_heads_over_limit)
778 pagevec_strip(&pvec);
779 __pagevec_release(&pvec);
780 spin_lock_irq(&zone->lru_lock);
781 }
782 }
783 zone->nr_inactive += pgmoved;
784 pgdeactivate += pgmoved;
785 if (buffer_heads_over_limit) {
786 spin_unlock_irq(&zone->lru_lock);
787 pagevec_strip(&pvec);
788 spin_lock_irq(&zone->lru_lock);
789 }
790
791 pgmoved = 0;
792 while (!list_empty(&l_active)) {
793 page = lru_to_page(&l_active);
794 prefetchw_prev_lru_page(page, &l_active, flags);
795 if (TestSetPageLRU(page))
796 BUG();
797 BUG_ON(!PageActive(page));
798 list_move(&page->lru, &zone->active_list);
799 pgmoved++;
800 if (!pagevec_add(&pvec, page)) {
801 zone->nr_active += pgmoved;
802 pgmoved = 0;
803 spin_unlock_irq(&zone->lru_lock);
804 __pagevec_release(&pvec);
805 spin_lock_irq(&zone->lru_lock);
806 }
807 }
808 zone->nr_active += pgmoved;
809 spin_unlock_irq(&zone->lru_lock);
810 pagevec_release(&pvec);
811
812 mod_page_state_zone(zone, pgrefill, pgscanned);
813 mod_page_state(pgdeactivate, pgdeactivate);
814}
815
816/*
817 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
818 */
819static void
820shrink_zone(struct zone *zone, struct scan_control *sc)
821{
822 unsigned long nr_active;
823 unsigned long nr_inactive;
824
Martin Hicks53e9a612005-09-03 15:54:51 -0700825 atomic_inc(&zone->reclaim_in_progress);
826
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827 /*
828 * Add one to `nr_to_scan' just to make sure that the kernel will
829 * slowly sift through the active list.
830 */
831 zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
832 nr_active = zone->nr_scan_active;
833 if (nr_active >= sc->swap_cluster_max)
834 zone->nr_scan_active = 0;
835 else
836 nr_active = 0;
837
838 zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
839 nr_inactive = zone->nr_scan_inactive;
840 if (nr_inactive >= sc->swap_cluster_max)
841 zone->nr_scan_inactive = 0;
842 else
843 nr_inactive = 0;
844
845 sc->nr_to_reclaim = sc->swap_cluster_max;
846
847 while (nr_active || nr_inactive) {
848 if (nr_active) {
849 sc->nr_to_scan = min(nr_active,
850 (unsigned long)sc->swap_cluster_max);
851 nr_active -= sc->nr_to_scan;
852 refill_inactive_zone(zone, sc);
853 }
854
855 if (nr_inactive) {
856 sc->nr_to_scan = min(nr_inactive,
857 (unsigned long)sc->swap_cluster_max);
858 nr_inactive -= sc->nr_to_scan;
859 shrink_cache(zone, sc);
860 if (sc->nr_to_reclaim <= 0)
861 break;
862 }
863 }
864
865 throttle_vm_writeout();
Martin Hicks53e9a612005-09-03 15:54:51 -0700866
867 atomic_dec(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868}
869
870/*
871 * This is the direct reclaim path, for page-allocating processes. We only
872 * try to reclaim pages from zones which will satisfy the caller's allocation
873 * request.
874 *
875 * We reclaim from a zone even if that zone is over pages_high. Because:
876 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
877 * allocation or
878 * b) The zones may be over pages_high but they must go *over* pages_high to
879 * satisfy the `incremental min' zone defense algorithm.
880 *
881 * Returns the number of reclaimed pages.
882 *
883 * If a zone is deemed to be full of pinned pages then just give it a light
884 * scan then give up on it.
885 */
886static void
887shrink_caches(struct zone **zones, struct scan_control *sc)
888{
889 int i;
890
891 for (i = 0; zones[i] != NULL; i++) {
892 struct zone *zone = zones[i];
893
894 if (zone->present_pages == 0)
895 continue;
896
Paul Jackson9bf22292005-09-06 15:18:12 -0700897 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 continue;
899
900 zone->temp_priority = sc->priority;
901 if (zone->prev_priority > sc->priority)
902 zone->prev_priority = sc->priority;
903
904 if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
905 continue; /* Let kswapd poll it */
906
907 shrink_zone(zone, sc);
908 }
909}
910
911/*
912 * This is the main entry point to direct page reclaim.
913 *
914 * If a full scan of the inactive list fails to free enough memory then we
915 * are "out of memory" and something needs to be killed.
916 *
917 * If the caller is !__GFP_FS then the probability of a failure is reasonably
918 * high - the zone may be full of dirty or under-writeback pages, which this
919 * caller can't do much about. We kick pdflush and take explicit naps in the
920 * hope that some of these pages can be written. But if the allocating task
921 * holds filesystem locks which prevent writeout this might not work, and the
922 * allocation attempt will fail.
923 */
Darren Hart1ad539b2005-06-21 17:14:53 -0700924int try_to_free_pages(struct zone **zones, unsigned int gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925{
926 int priority;
927 int ret = 0;
928 int total_scanned = 0, total_reclaimed = 0;
929 struct reclaim_state *reclaim_state = current->reclaim_state;
930 struct scan_control sc;
931 unsigned long lru_pages = 0;
932 int i;
933
934 sc.gfp_mask = gfp_mask;
935 sc.may_writepage = 0;
Martin Hicksbfbb38f2005-06-21 17:14:40 -0700936 sc.may_swap = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937
938 inc_page_state(allocstall);
939
940 for (i = 0; zones[i] != NULL; i++) {
941 struct zone *zone = zones[i];
942
Paul Jackson9bf22292005-09-06 15:18:12 -0700943 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 continue;
945
946 zone->temp_priority = DEF_PRIORITY;
947 lru_pages += zone->nr_active + zone->nr_inactive;
948 }
949
950 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
951 sc.nr_mapped = read_page_state(nr_mapped);
952 sc.nr_scanned = 0;
953 sc.nr_reclaimed = 0;
954 sc.priority = priority;
955 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
956 shrink_caches(zones, &sc);
957 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
958 if (reclaim_state) {
959 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
960 reclaim_state->reclaimed_slab = 0;
961 }
962 total_scanned += sc.nr_scanned;
963 total_reclaimed += sc.nr_reclaimed;
964 if (total_reclaimed >= sc.swap_cluster_max) {
965 ret = 1;
966 goto out;
967 }
968
969 /*
970 * Try to write back as many pages as we just scanned. This
971 * tends to cause slow streaming writers to write data to the
972 * disk smoothly, at the dirtying rate, which is nice. But
973 * that's undesirable in laptop mode, where we *want* lumpy
974 * writeout. So in laptop mode, write out the whole world.
975 */
976 if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700977 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978 sc.may_writepage = 1;
979 }
980
981 /* Take a nap, wait for some writeback to complete */
982 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
983 blk_congestion_wait(WRITE, HZ/10);
984 }
985out:
986 for (i = 0; zones[i] != 0; i++) {
987 struct zone *zone = zones[i];
988
Paul Jackson9bf22292005-09-06 15:18:12 -0700989 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990 continue;
991
992 zone->prev_priority = zone->temp_priority;
993 }
994 return ret;
995}
996
997/*
998 * For kswapd, balance_pgdat() will work across all this node's zones until
999 * they are all at pages_high.
1000 *
1001 * If `nr_pages' is non-zero then it is the number of pages which are to be
1002 * reclaimed, regardless of the zone occupancies. This is a software suspend
1003 * special.
1004 *
1005 * Returns the number of pages which were actually freed.
1006 *
1007 * There is special handling here for zones which are full of pinned pages.
1008 * This can happen if the pages are all mlocked, or if they are all used by
1009 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1010 * What we do is to detect the case where all pages in the zone have been
1011 * scanned twice and there has been zero successful reclaim. Mark the zone as
1012 * dead and from now on, only perform a short scan. Basically we're polling
1013 * the zone for when the problem goes away.
1014 *
1015 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1016 * zones which have free_pages > pages_high, but once a zone is found to have
1017 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1018 * of the number of free pages in the lower zones. This interoperates with
1019 * the page allocator fallback scheme to ensure that aging of pages is balanced
1020 * across the zones.
1021 */
1022static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
1023{
1024 int to_free = nr_pages;
1025 int all_zones_ok;
1026 int priority;
1027 int i;
1028 int total_scanned, total_reclaimed;
1029 struct reclaim_state *reclaim_state = current->reclaim_state;
1030 struct scan_control sc;
1031
1032loop_again:
1033 total_scanned = 0;
1034 total_reclaimed = 0;
1035 sc.gfp_mask = GFP_KERNEL;
1036 sc.may_writepage = 0;
Martin Hicksbfbb38f2005-06-21 17:14:40 -07001037 sc.may_swap = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038 sc.nr_mapped = read_page_state(nr_mapped);
1039
1040 inc_page_state(pageoutrun);
1041
1042 for (i = 0; i < pgdat->nr_zones; i++) {
1043 struct zone *zone = pgdat->node_zones + i;
1044
1045 zone->temp_priority = DEF_PRIORITY;
1046 }
1047
1048 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1049 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1050 unsigned long lru_pages = 0;
1051
1052 all_zones_ok = 1;
1053
1054 if (nr_pages == 0) {
1055 /*
1056 * Scan in the highmem->dma direction for the highest
1057 * zone which needs scanning
1058 */
1059 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1060 struct zone *zone = pgdat->node_zones + i;
1061
1062 if (zone->present_pages == 0)
1063 continue;
1064
1065 if (zone->all_unreclaimable &&
1066 priority != DEF_PRIORITY)
1067 continue;
1068
1069 if (!zone_watermark_ok(zone, order,
1070 zone->pages_high, 0, 0, 0)) {
1071 end_zone = i;
1072 goto scan;
1073 }
1074 }
1075 goto out;
1076 } else {
1077 end_zone = pgdat->nr_zones - 1;
1078 }
1079scan:
1080 for (i = 0; i <= end_zone; i++) {
1081 struct zone *zone = pgdat->node_zones + i;
1082
1083 lru_pages += zone->nr_active + zone->nr_inactive;
1084 }
1085
1086 /*
1087 * Now scan the zone in the dma->highmem direction, stopping
1088 * at the last zone which needs scanning.
1089 *
1090 * We do this because the page allocator works in the opposite
1091 * direction. This prevents the page allocator from allocating
1092 * pages behind kswapd's direction of progress, which would
1093 * cause too much scanning of the lower zones.
1094 */
1095 for (i = 0; i <= end_zone; i++) {
1096 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001097 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098
1099 if (zone->present_pages == 0)
1100 continue;
1101
1102 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1103 continue;
1104
1105 if (nr_pages == 0) { /* Not software suspend */
1106 if (!zone_watermark_ok(zone, order,
1107 zone->pages_high, end_zone, 0, 0))
1108 all_zones_ok = 0;
1109 }
1110 zone->temp_priority = priority;
1111 if (zone->prev_priority > priority)
1112 zone->prev_priority = priority;
1113 sc.nr_scanned = 0;
1114 sc.nr_reclaimed = 0;
1115 sc.priority = priority;
1116 sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001117 atomic_inc(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 shrink_zone(zone, &sc);
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001119 atomic_dec(&zone->reclaim_in_progress);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001120 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001121 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1122 lru_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001123 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1124 total_reclaimed += sc.nr_reclaimed;
1125 total_scanned += sc.nr_scanned;
1126 if (zone->all_unreclaimable)
1127 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001128 if (nr_slab == 0 && zone->pages_scanned >=
1129 (zone->nr_active + zone->nr_inactive) * 4)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130 zone->all_unreclaimable = 1;
1131 /*
1132 * If we've done a decent amount of scanning and
1133 * the reclaim ratio is low, start doing writepage
1134 * even in laptop mode
1135 */
1136 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1137 total_scanned > total_reclaimed+total_reclaimed/2)
1138 sc.may_writepage = 1;
1139 }
1140 if (nr_pages && to_free > total_reclaimed)
1141 continue; /* swsusp: need to do more work */
1142 if (all_zones_ok)
1143 break; /* kswapd: all done */
1144 /*
1145 * OK, kswapd is getting into trouble. Take a nap, then take
1146 * another pass across the zones.
1147 */
1148 if (total_scanned && priority < DEF_PRIORITY - 2)
1149 blk_congestion_wait(WRITE, HZ/10);
1150
1151 /*
1152 * We do this so kswapd doesn't build up large priorities for
1153 * example when it is freeing in parallel with allocators. It
1154 * matches the direct reclaim path behaviour in terms of impact
1155 * on zone->*_priority.
1156 */
1157 if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
1158 break;
1159 }
1160out:
1161 for (i = 0; i < pgdat->nr_zones; i++) {
1162 struct zone *zone = pgdat->node_zones + i;
1163
1164 zone->prev_priority = zone->temp_priority;
1165 }
1166 if (!all_zones_ok) {
1167 cond_resched();
1168 goto loop_again;
1169 }
1170
1171 return total_reclaimed;
1172}
1173
1174/*
1175 * The background pageout daemon, started as a kernel thread
1176 * from the init process.
1177 *
1178 * This basically trickles out pages so that we have _some_
1179 * free memory available even if there is no other activity
1180 * that frees anything up. This is needed for things like routing
1181 * etc, where we otherwise might have all activity going on in
1182 * asynchronous contexts that cannot page things out.
1183 *
1184 * If there are applications that are active memory-allocators
1185 * (most normal use), this basically shouldn't matter.
1186 */
1187static int kswapd(void *p)
1188{
1189 unsigned long order;
1190 pg_data_t *pgdat = (pg_data_t*)p;
1191 struct task_struct *tsk = current;
1192 DEFINE_WAIT(wait);
1193 struct reclaim_state reclaim_state = {
1194 .reclaimed_slab = 0,
1195 };
1196 cpumask_t cpumask;
1197
1198 daemonize("kswapd%d", pgdat->node_id);
1199 cpumask = node_to_cpumask(pgdat->node_id);
1200 if (!cpus_empty(cpumask))
1201 set_cpus_allowed(tsk, cpumask);
1202 current->reclaim_state = &reclaim_state;
1203
1204 /*
1205 * Tell the memory management that we're a "memory allocator",
1206 * and that if we need more memory we should get access to it
1207 * regardless (see "__alloc_pages()"). "kswapd" should
1208 * never get caught in the normal page freeing logic.
1209 *
1210 * (Kswapd normally doesn't need memory anyway, but sometimes
1211 * you need a small amount of memory in order to be able to
1212 * page out something else, and this flag essentially protects
1213 * us from recursively trying to free more memory as we're
1214 * trying to free the first piece of memory in the first place).
1215 */
1216 tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
1217
1218 order = 0;
1219 for ( ; ; ) {
1220 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001221
1222 try_to_freeze();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223
1224 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1225 new_order = pgdat->kswapd_max_order;
1226 pgdat->kswapd_max_order = 0;
1227 if (order < new_order) {
1228 /*
1229 * Don't sleep if someone wants a larger 'order'
1230 * allocation
1231 */
1232 order = new_order;
1233 } else {
1234 schedule();
1235 order = pgdat->kswapd_max_order;
1236 }
1237 finish_wait(&pgdat->kswapd_wait, &wait);
1238
1239 balance_pgdat(pgdat, 0, order);
1240 }
1241 return 0;
1242}
1243
1244/*
1245 * A zone is low on free memory, so wake its kswapd task to service it.
1246 */
1247void wakeup_kswapd(struct zone *zone, int order)
1248{
1249 pg_data_t *pgdat;
1250
1251 if (zone->present_pages == 0)
1252 return;
1253
1254 pgdat = zone->zone_pgdat;
1255 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0, 0))
1256 return;
1257 if (pgdat->kswapd_max_order < order)
1258 pgdat->kswapd_max_order = order;
Paul Jackson9bf22292005-09-06 15:18:12 -07001259 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001261 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001263 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264}
1265
1266#ifdef CONFIG_PM
1267/*
1268 * Try to free `nr_pages' of memory, system-wide. Returns the number of freed
1269 * pages.
1270 */
1271int shrink_all_memory(int nr_pages)
1272{
1273 pg_data_t *pgdat;
1274 int nr_to_free = nr_pages;
1275 int ret = 0;
1276 struct reclaim_state reclaim_state = {
1277 .reclaimed_slab = 0,
1278 };
1279
1280 current->reclaim_state = &reclaim_state;
1281 for_each_pgdat(pgdat) {
1282 int freed;
1283 freed = balance_pgdat(pgdat, nr_to_free, 0);
1284 ret += freed;
1285 nr_to_free -= freed;
1286 if (nr_to_free <= 0)
1287 break;
1288 }
1289 current->reclaim_state = NULL;
1290 return ret;
1291}
1292#endif
1293
1294#ifdef CONFIG_HOTPLUG_CPU
1295/* It's optimal to keep kswapds on the same CPUs as their memory, but
1296 not required for correctness. So if the last cpu in a node goes
1297 away, we get changed to run anywhere: as the first one comes back,
1298 restore their cpu bindings. */
1299static int __devinit cpu_callback(struct notifier_block *nfb,
1300 unsigned long action,
1301 void *hcpu)
1302{
1303 pg_data_t *pgdat;
1304 cpumask_t mask;
1305
1306 if (action == CPU_ONLINE) {
1307 for_each_pgdat(pgdat) {
1308 mask = node_to_cpumask(pgdat->node_id);
1309 if (any_online_cpu(mask) != NR_CPUS)
1310 /* One of our CPUs online: restore mask */
1311 set_cpus_allowed(pgdat->kswapd, mask);
1312 }
1313 }
1314 return NOTIFY_OK;
1315}
1316#endif /* CONFIG_HOTPLUG_CPU */
1317
1318static int __init kswapd_init(void)
1319{
1320 pg_data_t *pgdat;
1321 swap_setup();
1322 for_each_pgdat(pgdat)
1323 pgdat->kswapd
1324 = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
1325 total_memory = nr_free_pagecache_pages();
1326 hotcpu_notifier(cpu_callback, 0);
1327 return 0;
1328}
1329
1330module_init(kswapd_init)
Martin Hicks753ee722005-06-21 17:14:41 -07001331
1332
1333/*
1334 * Try to free up some pages from this zone through reclaim.
1335 */
1336int zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
1337{
1338 struct scan_control sc;
1339 int nr_pages = 1 << order;
1340 int total_reclaimed = 0;
1341
1342 /* The reclaim may sleep, so don't do it if sleep isn't allowed */
1343 if (!(gfp_mask & __GFP_WAIT))
1344 return 0;
1345 if (zone->all_unreclaimable)
1346 return 0;
1347
1348 sc.gfp_mask = gfp_mask;
1349 sc.may_writepage = 0;
1350 sc.may_swap = 0;
1351 sc.nr_mapped = read_page_state(nr_mapped);
1352 sc.nr_scanned = 0;
1353 sc.nr_reclaimed = 0;
1354 /* scan at the highest priority */
1355 sc.priority = 0;
1356
1357 if (nr_pages > SWAP_CLUSTER_MAX)
1358 sc.swap_cluster_max = nr_pages;
1359 else
1360 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
1361
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001362 /* Don't reclaim the zone if there are other reclaimers active */
Martin Hicks53e9a612005-09-03 15:54:51 -07001363 if (atomic_read(&zone->reclaim_in_progress) > 0)
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001364 goto out;
1365
Martin Hicks753ee722005-06-21 17:14:41 -07001366 shrink_zone(zone, &sc);
1367 total_reclaimed = sc.nr_reclaimed;
1368
Martin Hicks1e7e5a92005-06-21 17:14:43 -07001369 out:
Martin Hicks753ee722005-06-21 17:14:41 -07001370 return total_reclaimed;
1371}
1372
1373asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone,
1374 unsigned int state)
1375{
1376 struct zone *z;
1377 int i;
1378
Martin Hicksbce5f6ba2005-09-03 15:54:50 -07001379 if (!capable(CAP_SYS_ADMIN))
1380 return -EACCES;
1381
Martin Hicks753ee722005-06-21 17:14:41 -07001382 if (node >= MAX_NUMNODES || !node_online(node))
1383 return -EINVAL;
1384
1385 /* This will break if we ever add more zones */
1386 if (!(zone & (1<<ZONE_DMA|1<<ZONE_NORMAL|1<<ZONE_HIGHMEM)))
1387 return -EINVAL;
1388
1389 for (i = 0; i < MAX_NR_ZONES; i++) {
1390 if (!(zone & 1<<i))
1391 continue;
1392
1393 z = &NODE_DATA(node)->node_zones[i];
1394
1395 if (state)
1396 z->reclaim_pages = 1;
1397 else
1398 z->reclaim_pages = 0;
1399 }
1400
1401 return 0;
1402}