vmscan.c 72.7 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/highmem.h>
22
#include <linux/vmstat.h>
L
Linus Torvalds 已提交
23 24 25 26 27 28 29 30 31 32 33 34 35 36
#include <linux/file.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>	/* for try_to_release_page(),
					buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/notifier.h>
#include <linux/rwsem.h>
37
#include <linux/delay.h>
38
#include <linux/kthread.h>
39
#include <linux/freezer.h>
40
#include <linux/memcontrol.h>
41
#include <linux/delayacct.h>
42
#include <linux/sysctl.h>
L
Linus Torvalds 已提交
43 44 45 46 47 48

#include <asm/tlbflush.h>
#include <asm/div64.h>

#include <linux/swapops.h>

49 50
#include "internal.h"

L
Linus Torvalds 已提交
51 52 53 54
struct scan_control {
	/* Incremented by the number of inactive pages that were scanned */
	unsigned long nr_scanned;

55 56 57
	/* Number of pages freed so far during a call to shrink_zones() */
	unsigned long nr_reclaimed;

L
Linus Torvalds 已提交
58
	/* This context's GFP mask */
A
Al Viro 已提交
59
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
60 61 62

	int may_writepage;

63 64
	/* Can mapped pages be reclaimed? */
	int may_unmap;
65

L
Linus Torvalds 已提交
66 67 68 69 70
	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
	 * In this context, it doesn't matter that we scan the
	 * whole list at once. */
	int swap_cluster_max;
71 72

	int swappiness;
73 74

	int all_unreclaimable;
A
Andy Whitcroft 已提交
75 76

	int order;
77 78 79 80 81 82 83 84

	/* Which cgroup do we reclaim from */
	struct mem_cgroup *mem_cgroup;

	/* Pluggable isolate pages callback */
	unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
			unsigned long *scanned, int order, int mode,
			struct zone *z, struct mem_cgroup *mem_cont,
85
			int active, int file);
L
Linus Torvalds 已提交
86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
};

#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))

#ifdef ARCH_HAS_PREFETCH
#define prefetch_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetch(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

#ifdef ARCH_HAS_PREFETCHW
#define prefetchw_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetchw(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

/*
 * From 0 .. 100.  Higher means more swappy.
 */
int vm_swappiness = 60;
122
long vm_total_pages;	/* The total number of pages which the VM controls */
L
Linus Torvalds 已提交
123 124 125 126

static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);

127
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
128
#define scanning_global_lru(sc)	(!(sc)->mem_cgroup)
129
#else
130
#define scanning_global_lru(sc)	(1)
131 132
#endif

133 134 135
static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
						  struct scan_control *sc)
{
136
	if (!scanning_global_lru(sc))
K
KOSAKI Motohiro 已提交
137 138
		return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);

139 140 141
	return &zone->reclaim_stat;
}

142 143 144
static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc,
				   enum lru_list lru)
{
145
	if (!scanning_global_lru(sc))
146 147
		return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);

148 149 150 151
	return zone_page_state(zone, NR_LRU_BASE + lru);
}


L
Linus Torvalds 已提交
152 153 154
/*
 * Add a shrinker callback to be called from the vm
 */
155
void register_shrinker(struct shrinker *shrinker)
L
Linus Torvalds 已提交
156
{
157 158 159 160
	shrinker->nr = 0;
	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
L
Linus Torvalds 已提交
161
}
162
EXPORT_SYMBOL(register_shrinker);
L
Linus Torvalds 已提交
163 164 165 166

/*
 * Remove one
 */
167
void unregister_shrinker(struct shrinker *shrinker)
L
Linus Torvalds 已提交
168 169 170 171 172
{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
173
EXPORT_SYMBOL(unregister_shrinker);
L
Linus Torvalds 已提交
174 175 176 177 178 179 180 181 182 183

#define SHRINK_BATCH 128
/*
 * Call the shrink functions to age shrinkable caches
 *
 * Here we assume it costs one seek to replace a lru page and that it also
 * takes a seek to recreate a cache object.  With this in mind we age equal
 * percentages of the lru and ageable caches.  This should balance the seeks
 * generated by these structures.
 *
S
Simon Arlott 已提交
184
 * If the vm encountered mapped pages on the LRU it increase the pressure on
L
Linus Torvalds 已提交
185 186 187 188 189 190 191
 * slab to avoid swapping.
 *
 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
 *
 * `lru_pages' represents the number of on-LRU pages in all the zones which
 * are eligible for the caller's allocation attempt.  It is used for balancing
 * slab reclaim versus page reclaim.
192 193
 *
 * Returns the number of slab objects which we shrunk.
L
Linus Torvalds 已提交
194
 */
195 196
unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
			unsigned long lru_pages)
L
Linus Torvalds 已提交
197 198
{
	struct shrinker *shrinker;
199
	unsigned long ret = 0;
L
Linus Torvalds 已提交
200 201 202 203 204

	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

	if (!down_read_trylock(&shrinker_rwsem))
205
		return 1;	/* Assume we'll be able to shrink next time */
L
Linus Torvalds 已提交
206 207 208 209

	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
210
		unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
L
Linus Torvalds 已提交
211 212

		delta = (4 * scanned) / shrinker->seeks;
213
		delta *= max_pass;
L
Linus Torvalds 已提交
214 215
		do_div(delta, lru_pages + 1);
		shrinker->nr += delta;
216 217
		if (shrinker->nr < 0) {
			printk(KERN_ERR "%s: nr=%ld\n",
218
					__func__, shrinker->nr);
219 220 221 222 223 224 225 226 227 228
			shrinker->nr = max_pass;
		}

		/*
		 * Avoid risking looping forever due to too large nr value:
		 * never try to free more than twice the estimate number of
		 * freeable entries.
		 */
		if (shrinker->nr > max_pass * 2)
			shrinker->nr = max_pass * 2;
L
Linus Torvalds 已提交
229 230 231 232 233 234 235

		total_scan = shrinker->nr;
		shrinker->nr = 0;

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
236
			int nr_before;
L
Linus Torvalds 已提交
237

238 239
			nr_before = (*shrinker->shrink)(0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
L
Linus Torvalds 已提交
240 241
			if (shrink_ret == -1)
				break;
242 243
			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
244
			count_vm_events(SLABS_SCANNED, this_scan);
L
Linus Torvalds 已提交
245 246 247 248 249 250 251 252
			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
253
	return ret;
L
Linus Torvalds 已提交
254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283
}

/* Called without lock on whether page is mapped, so answer is unstable */
static inline int page_mapping_inuse(struct page *page)
{
	struct address_space *mapping;

	/* Page is in somebody's page tables. */
	if (page_mapped(page))
		return 1;

	/* Be more reluctant to reclaim swapcache than pagecache */
	if (PageSwapCache(page))
		return 1;

	mapping = page_mapping(page);
	if (!mapping)
		return 0;

	/* File is mmap'd by somebody? */
	return mapping_mapped(mapping);
}

static inline int is_page_cache_freeable(struct page *page)
{
	return page_count(page) - !!PagePrivate(page) == 2;
}

static int may_write_to_queue(struct backing_dev_info *bdi)
{
284
	if (current->flags & PF_SWAPWRITE)
L
Linus Torvalds 已提交
285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308
		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
	return 0;
}

/*
 * We detected a synchronous write error writing a page out.  Probably
 * -ENOSPC.  We need to propagate that into the address_space for a subsequent
 * fsync(), msync() or close().
 *
 * The tricky part is that after writepage we cannot touch the mapping: nothing
 * prevents it from being freed up.  But we have a ref on the page and once
 * that page is locked, the mapping is pinned.
 *
 * We're allowed to run sleeping lock_page() here because we know the caller has
 * __GFP_FS.
 */
static void handle_write_error(struct address_space *mapping,
				struct page *page, int error)
{
	lock_page(page);
309 310
	if (page_mapping(page) == mapping)
		mapping_set_error(mapping, error);
L
Linus Torvalds 已提交
311 312 313
	unlock_page(page);
}

314 315 316 317 318 319
/* Request for sync pageout. */
enum pageout_io {
	PAGEOUT_IO_ASYNC,
	PAGEOUT_IO_SYNC,
};

320 321 322 323 324 325 326 327 328 329 330 331
/* possible outcome of pageout() */
typedef enum {
	/* failed to write page out, page is locked */
	PAGE_KEEP,
	/* move page to the active list, page is locked */
	PAGE_ACTIVATE,
	/* page has been sent to the disk successfully, page is unlocked */
	PAGE_SUCCESS,
	/* page is clean and locked */
	PAGE_CLEAN,
} pageout_t;

L
Linus Torvalds 已提交
332
/*
A
Andrew Morton 已提交
333 334
 * pageout is called by shrink_page_list() for each dirty page.
 * Calls ->writepage().
L
Linus Torvalds 已提交
335
 */
336 337
static pageout_t pageout(struct page *page, struct address_space *mapping,
						enum pageout_io sync_writeback)
L
Linus Torvalds 已提交
338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362
{
	/*
	 * If the page is dirty, only perform writeback if that write
	 * will be non-blocking.  To prevent this allocation from being
	 * stalled by pagecache activity.  But note that there may be
	 * stalls if we need to run get_block().  We could test
	 * PagePrivate for that.
	 *
	 * If this process is currently in generic_file_write() against
	 * this page's queue, we can perform writeback even if that
	 * will block.
	 *
	 * If the page is swapcache, write it back even if that would
	 * block, for some throttling. This happens by accident, because
	 * swap_backing_dev_info is bust: it doesn't reflect the
	 * congestion state of the swapdevs.  Easy to fix, if needed.
	 * See swapfile.c:page_queue_congested().
	 */
	if (!is_page_cache_freeable(page))
		return PAGE_KEEP;
	if (!mapping) {
		/*
		 * Some data journaling orphaned pages can have
		 * page->mapping == NULL while being dirty with clean buffers.
		 */
363
		if (PagePrivate(page)) {
L
Linus Torvalds 已提交
364 365
			if (try_to_free_buffers(page)) {
				ClearPageDirty(page);
366
				printk("%s: orphaned page\n", __func__);
L
Linus Torvalds 已提交
367 368 369 370 371 372 373 374 375 376 377 378 379 380 381
				return PAGE_CLEAN;
			}
		}
		return PAGE_KEEP;
	}
	if (mapping->a_ops->writepage == NULL)
		return PAGE_ACTIVATE;
	if (!may_write_to_queue(mapping->backing_dev_info))
		return PAGE_KEEP;

	if (clear_page_dirty_for_io(page)) {
		int res;
		struct writeback_control wbc = {
			.sync_mode = WB_SYNC_NONE,
			.nr_to_write = SWAP_CLUSTER_MAX,
382 383
			.range_start = 0,
			.range_end = LLONG_MAX,
L
Linus Torvalds 已提交
384 385 386 387 388 389 390 391
			.nonblocking = 1,
			.for_reclaim = 1,
		};

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
392
		if (res == AOP_WRITEPAGE_ACTIVATE) {
L
Linus Torvalds 已提交
393 394 395
			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
396 397 398 399 400 401 402 403 404

		/*
		 * Wait on writeback if requested to. This happens when
		 * direct reclaiming a large contiguous area and the
		 * first attempt to free a range of pages fails.
		 */
		if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
			wait_on_page_writeback(page);

L
Linus Torvalds 已提交
405 406 407 408
		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
409
		inc_zone_page_state(page, NR_VMSCAN_WRITE);
L
Linus Torvalds 已提交
410 411 412 413 414 415
		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

416
/*
N
Nick Piggin 已提交
417 418
 * Same as remove_mapping, but if the page is removed from the mapping, it
 * gets returned with a refcount of 0.
419
 */
N
Nick Piggin 已提交
420
static int __remove_mapping(struct address_space *mapping, struct page *page)
421
{
422 423
	BUG_ON(!PageLocked(page));
	BUG_ON(mapping != page_mapping(page));
424

N
Nick Piggin 已提交
425
	spin_lock_irq(&mapping->tree_lock);
426
	/*
N
Nick Piggin 已提交
427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449
	 * The non racy check for a busy page.
	 *
	 * Must be careful with the order of the tests. When someone has
	 * a ref to the page, it may be possible that they dirty it then
	 * drop the reference. So if PageDirty is tested before page_count
	 * here, then the following race may occur:
	 *
	 * get_user_pages(&page);
	 * [user mapping goes away]
	 * write_to(page);
	 *				!PageDirty(page)    [good]
	 * SetPageDirty(page);
	 * put_page(page);
	 *				!page_count(page)   [good, discard it]
	 *
	 * [oops, our write_to data is lost]
	 *
	 * Reversing the order of the tests ensures such a situation cannot
	 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
	 * load is not satisfied before that of page->_count.
	 *
	 * Note that if SetPageDirty is always performed via set_page_dirty,
	 * and thus under tree_lock, then this ordering is not required.
450
	 */
N
Nick Piggin 已提交
451
	if (!page_freeze_refs(page, 2))
452
		goto cannot_free;
N
Nick Piggin 已提交
453 454 455
	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
	if (unlikely(PageDirty(page))) {
		page_unfreeze_refs(page, 2);
456
		goto cannot_free;
N
Nick Piggin 已提交
457
	}
458 459 460 461

	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
N
Nick Piggin 已提交
462
		spin_unlock_irq(&mapping->tree_lock);
463
		swap_free(swap);
N
Nick Piggin 已提交
464 465
	} else {
		__remove_from_page_cache(page);
N
Nick Piggin 已提交
466
		spin_unlock_irq(&mapping->tree_lock);
467 468 469 470 471
	}

	return 1;

cannot_free:
N
Nick Piggin 已提交
472
	spin_unlock_irq(&mapping->tree_lock);
473 474 475
	return 0;
}

N
Nick Piggin 已提交
476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495
/*
 * Attempt to detach a locked page from its ->mapping.  If it is dirty or if
 * someone else has a ref on the page, abort and return 0.  If it was
 * successfully detached, return 1.  Assumes the caller has a single ref on
 * this page.
 */
int remove_mapping(struct address_space *mapping, struct page *page)
{
	if (__remove_mapping(mapping, page)) {
		/*
		 * Unfreezing the refcount with 1 rather than 2 effectively
		 * drops the pagecache ref for us without requiring another
		 * atomic operation.
		 */
		page_unfreeze_refs(page, 1);
		return 1;
	}
	return 0;
}

L
Lee Schermerhorn 已提交
496 497 498 499 500 501 502 503 504 505 506 507 508 509
/**
 * putback_lru_page - put previously isolated page onto appropriate LRU list
 * @page: page to be put back to appropriate lru list
 *
 * Add previously isolated @page to appropriate LRU list.
 * Page may still be unevictable for other reasons.
 *
 * lru_lock must not be held, interrupts must be enabled.
 */
#ifdef CONFIG_UNEVICTABLE_LRU
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
510
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550

	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

	if (page_evictable(page, NULL)) {
		/*
		 * For evictable pages, we can use the cache.
		 * In event of a race, worst case is we end up with an
		 * unevictable page on [in]active list.
		 * We know how to handle that.
		 */
		lru = active + page_is_file_cache(page);
		lru_cache_add_lru(page, lru);
	} else {
		/*
		 * Put unevictable pages directly on zone's unevictable
		 * list.
		 */
		lru = LRU_UNEVICTABLE;
		add_page_to_unevictable_list(page);
	}

	/*
	 * page's status can change while we move it among lru. If an evictable
	 * page is on unevictable list, it never be freed. To avoid that,
	 * check after we added it to the list, again.
	 */
	if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
		if (!isolate_lru_page(page)) {
			put_page(page);
			goto redo;
		}
		/* This means someone else dropped this page from LRU
		 * So, it will be freed or putback to LRU again. There is
		 * nothing to do here.
		 */
	}

551 552 553 554 555
	if (was_unevictable && lru != LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGRESCUED);
	else if (!was_unevictable && lru == LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGCULLED);

L
Lee Schermerhorn 已提交
556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572
	put_page(page);		/* drop ref from isolate */
}

#else /* CONFIG_UNEVICTABLE_LRU */

void putback_lru_page(struct page *page)
{
	int lru;
	VM_BUG_ON(PageLRU(page));

	lru = !!TestClearPageActive(page) + page_is_file_cache(page);
	lru_cache_add_lru(page, lru);
	put_page(page);
}
#endif /* CONFIG_UNEVICTABLE_LRU */


L
Linus Torvalds 已提交
573
/*
A
Andrew Morton 已提交
574
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
575
 */
A
Andrew Morton 已提交
576
static unsigned long shrink_page_list(struct list_head *page_list,
577 578
					struct scan_control *sc,
					enum pageout_io sync_writeback)
L
Linus Torvalds 已提交
579 580 581 582
{
	LIST_HEAD(ret_pages);
	struct pagevec freed_pvec;
	int pgactivate = 0;
583
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
584 585 586 587 588 589 590 591 592 593 594 595 596 597 598

	cond_resched();

	pagevec_init(&freed_pvec, 1);
	while (!list_empty(page_list)) {
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;
		int referenced;

		cond_resched();

		page = lru_to_page(page_list);
		list_del(&page->lru);

N
Nick Piggin 已提交
599
		if (!trylock_page(page))
L
Linus Torvalds 已提交
600 601
			goto keep;

N
Nick Piggin 已提交
602
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
603 604

		sc->nr_scanned++;
605

N
Nick Piggin 已提交
606 607
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
608

609
		if (!sc->may_unmap && page_mapped(page))
610 611
			goto keep_locked;

L
Linus Torvalds 已提交
612 613 614 615
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

616 617 618 619 620 621 622 623 624 625 626 627 628 629
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
			/*
			 * Synchronous reclaim is performed in two passes,
			 * first an asynchronous pass over the list to
			 * start parallel writeback, and a second synchronous
			 * pass to wait for the IO to complete.  Wait here
			 * for any page for which writeback has already
			 * started.
			 */
			if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
				wait_on_page_writeback(page);
630
			else
631 632
				goto keep_locked;
		}
L
Linus Torvalds 已提交
633

634
		referenced = page_referenced(page, 1, sc->mem_cgroup);
L
Linus Torvalds 已提交
635
		/* In active use or really unfreeable?  Activate it. */
A
Andy Whitcroft 已提交
636 637
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
L
Linus Torvalds 已提交
638 639 640 641 642 643
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
644
		if (PageAnon(page) && !PageSwapCache(page)) {
645 646
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
647
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
648
				goto activate_locked;
649
			may_enter_fs = 1;
N
Nick Piggin 已提交
650
		}
L
Linus Torvalds 已提交
651 652 653 654 655 656 657 658

		mapping = page_mapping(page);

		/*
		 * The page is mapped into the page tables of one or more
		 * processes. Try to unmap it here.
		 */
		if (page_mapped(page) && mapping) {
659
			switch (try_to_unmap(page, 0)) {
L
Linus Torvalds 已提交
660 661 662 663
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
664 665
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
666 667 668 669 670 671
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
672
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
673
				goto keep_locked;
674
			if (!may_enter_fs)
L
Linus Torvalds 已提交
675
				goto keep_locked;
676
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
677 678 679
				goto keep_locked;

			/* Page is dirty, try to write it out here */
680
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
681 682 683 684 685
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
686
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
687 688 689 690 691
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
692
				if (!trylock_page(page))
L
Linus Torvalds 已提交
693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711
					goto keep;
				if (PageDirty(page) || PageWriteback(page))
					goto keep_locked;
				mapping = page_mapping(page);
			case PAGE_CLEAN:
				; /* try to free the page below */
			}
		}

		/*
		 * If the page has buffers, try to free the buffer mappings
		 * associated with this page. If we succeed we try to free
		 * the page as well.
		 *
		 * We do this even if the page is PageDirty().
		 * try_to_release_page() does not perform I/O, but it is
		 * possible for a page to have PageDirty set, but it is actually
		 * clean (all its buffers are clean).  This happens if the
		 * buffers were written out directly, with submit_bh(). ext3
L
Lee Schermerhorn 已提交
712
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
713 714 715 716 717 718 719 720 721 722 723 724 725
		 * try_to_release_page() will discover that cleanness and will
		 * drop the buffers and mark the page clean - it can be freed.
		 *
		 * Rarely, pages can have buffers and no ->mapping.  These are
		 * the pages which were not successfully invalidated in
		 * truncate_complete_page().  We try to drop those buffers here
		 * and if that worked, and the page is no longer mapped into
		 * process address space (page_count == 1) it can be freed.
		 * Otherwise, leave the page on the LRU so it is swappable.
		 */
		if (PagePrivate(page)) {
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741
			if (!mapping && page_count(page) == 1) {
				unlock_page(page);
				if (put_page_testzero(page))
					goto free_it;
				else {
					/*
					 * rare race with speculative reference.
					 * the speculative reference will free
					 * this page shortly, so we may
					 * increment nr_reclaimed here (and
					 * leave it off the LRU).
					 */
					nr_reclaimed++;
					continue;
				}
			}
L
Linus Torvalds 已提交
742 743
		}

N
Nick Piggin 已提交
744
		if (!mapping || !__remove_mapping(mapping, page))
745
			goto keep_locked;
L
Linus Torvalds 已提交
746

N
Nick Piggin 已提交
747 748 749 750 751 752 753 754
		/*
		 * At this point, we have no other references and there is
		 * no way to pick any more up (removed from LRU, removed
		 * from pagecache). Can use non-atomic bitops now (and
		 * we obviously don't have to worry about waking up a process
		 * waiting on the page lock, because there are no references.
		 */
		__clear_page_locked(page);
N
Nick Piggin 已提交
755
free_it:
756
		nr_reclaimed++;
N
Nick Piggin 已提交
757 758 759 760
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
761 762
		continue;

N
Nick Piggin 已提交
763
cull_mlocked:
764 765
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
766 767 768 769
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
770
activate_locked:
771 772
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
773
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
774
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
775 776 777 778 779 780
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
781
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
782 783 784
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
785
		__pagevec_free(&freed_pvec);
786
	count_vm_events(PGACTIVATE, pgactivate);
787
	return nr_reclaimed;
L
Linus Torvalds 已提交
788 789
}

A
Andy Whitcroft 已提交
790 791 792 793 794 795 796 797 798 799 800 801 802 803 804
/* LRU Isolation modes. */
#define ISOLATE_INACTIVE 0	/* Isolate inactive pages. */
#define ISOLATE_ACTIVE 1	/* Isolate active pages. */
#define ISOLATE_BOTH 2		/* Isolate both active and inactive pages. */

/*
 * Attempt to remove the specified page from its LRU.  Only take this page
 * if it is of the appropriate PageActive status.  Pages which are being
 * freed elsewhere are also ignored.
 *
 * page:	page to consider
 * mode:	one of the LRU isolation modes defined above
 *
 * returns 0 on success, -ve errno on failure.
 */
805
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
806 807 808 809 810 811 812 813 814 815 816 817 818 819 820
{
	int ret = -EINVAL;

	/* Only take pages on the LRU. */
	if (!PageLRU(page))
		return ret;

	/*
	 * When checking the active state, we need to be sure we are
	 * dealing with comparible boolean values.  Take the logical not
	 * of each.
	 */
	if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
		return ret;

821 822 823
	if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
		return ret;

L
Lee Schermerhorn 已提交
824 825 826 827 828 829 830 831
	/*
	 * When this function is being called for lumpy reclaim, we
	 * initially look into all LRU pages, active, inactive and
	 * unevictable; only give shrink_page_list evictable pages.
	 */
	if (PageUnevictable(page))
		return ret;

A
Andy Whitcroft 已提交
832
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
833

A
Andy Whitcroft 已提交
834 835 836 837 838 839 840 841
	if (likely(get_page_unless_zero(page))) {
		/*
		 * Be careful not to clear PageLRU until after we're
		 * sure the page is not being freed elsewhere -- the
		 * page release code relies on it.
		 */
		ClearPageLRU(page);
		ret = 0;
K
KAMEZAWA Hiroyuki 已提交
842
		mem_cgroup_del_lru(page);
A
Andy Whitcroft 已提交
843 844 845 846 847
	}

	return ret;
}

L
Linus Torvalds 已提交
848 849 850 851 852 853 854 855 856 857 858 859 860 861
/*
 * zone->lru_lock is heavily contended.  Some of the functions that
 * shrink the lists perform better by taking out a batch of pages
 * and working on them outside the LRU lock.
 *
 * For pagecache intensive workloads, this function is the hottest
 * spot in the kernel (apart from copy_*_user functions).
 *
 * Appropriate locks must be held before calling this function.
 *
 * @nr_to_scan:	The number of pages to look through on the list.
 * @src:	The LRU list to pull pages off.
 * @dst:	The temp list to put pages on to.
 * @scanned:	The number of pages that were scanned.
A
Andy Whitcroft 已提交
862 863
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
864
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
865 866 867
 *
 * returns how many pages were moved onto *@dst.
 */
868 869
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
870
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
871
{
872
	unsigned long nr_taken = 0;
873
	unsigned long scan;
L
Linus Torvalds 已提交
874

875
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
876 877 878 879 880 881
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
882 883 884
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
885
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
886

887
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
888 889
		case 0:
			list_move(&page->lru, dst);
890
			nr_taken++;
A
Andy Whitcroft 已提交
891 892 893 894 895 896
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
897

A
Andy Whitcroft 已提交
898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929
		default:
			BUG();
		}

		if (!order)
			continue;

		/*
		 * Attempt to take all pages in the order aligned region
		 * surrounding the tag page.  Only take those pages of
		 * the same active state as that tag page.  We may safely
		 * round the target page pfn down to the requested order
		 * as the mem_map is guarenteed valid out to MAX_ORDER,
		 * where that page is in a different zone we will detect
		 * it from its zone id and abort this block scan.
		 */
		zone_id = page_zone_id(page);
		page_pfn = page_to_pfn(page);
		pfn = page_pfn & ~((1 << order) - 1);
		end_pfn = pfn + (1 << order);
		for (; pfn < end_pfn; pfn++) {
			struct page *cursor_page;

			/* The target page is in the block, ignore it. */
			if (unlikely(pfn == page_pfn))
				continue;

			/* Avoid holes within the zone. */
			if (unlikely(!pfn_valid_within(pfn)))
				break;

			cursor_page = pfn_to_page(pfn);
930

A
Andy Whitcroft 已提交
931 932 933
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
934
			switch (__isolate_lru_page(cursor_page, mode, file)) {
A
Andy Whitcroft 已提交
935 936 937 938 939 940 941 942 943 944
			case 0:
				list_move(&cursor_page->lru, dst);
				nr_taken++;
				scan++;
				break;

			case -EBUSY:
				/* else it is being freed elsewhere */
				list_move(&cursor_page->lru, src);
			default:
L
Lee Schermerhorn 已提交
945
				break;	/* ! on LRU or wrong list */
A
Andy Whitcroft 已提交
946 947
			}
		}
L
Linus Torvalds 已提交
948 949 950 951 952 953
	}

	*scanned = scan;
	return nr_taken;
}

954 955 956 957 958
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
959
					int active, int file)
960
{
961
	int lru = LRU_BASE;
962
	if (active)
963 964 965 966 967
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
								mode, !!file);
968 969
}

A
Andy Whitcroft 已提交
970 971 972 973
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
974 975
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
976 977
{
	int nr_active = 0;
978
	int lru;
A
Andy Whitcroft 已提交
979 980
	struct page *page;

981 982
	list_for_each_entry(page, page_list, lru) {
		lru = page_is_file_cache(page);
A
Andy Whitcroft 已提交
983
		if (PageActive(page)) {
984
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
985 986 987
			ClearPageActive(page);
			nr_active++;
		}
988 989
		count[lru]++;
	}
A
Andy Whitcroft 已提交
990 991 992 993

	return nr_active;
}

994 995 996 997 998 999 1000 1001 1002 1003 1004
/**
 * isolate_lru_page - tries to isolate a page from its LRU list
 * @page: page to isolate from its LRU list
 *
 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
 * vmstat statistic corresponding to whatever LRU list the page was on.
 *
 * Returns 0 if the page was removed from an LRU list.
 * Returns -EBUSY if the page was not on an LRU list.
 *
 * The returned page will have PageLRU() cleared.  If it was found on
L
Lee Schermerhorn 已提交
1005 1006 1007
 * the active list, it will have PageActive set.  If it was found on
 * the unevictable list, it will have the PageUnevictable bit set. That flag
 * may need to be cleared by the caller before letting the page go.
1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027
 *
 * The vmstat statistic corresponding to the list on which the page was
 * found will be decremented.
 *
 * Restrictions:
 * (1) Must be called with an elevated refcount on the page. This is a
 *     fundamentnal difference from isolate_lru_pages (which is called
 *     without a stable reference).
 * (2) the lru_lock must not be held.
 * (3) interrupts must be enabled.
 */
int isolate_lru_page(struct page *page)
{
	int ret = -EBUSY;

	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
L
Lee Schermerhorn 已提交
1028
			int lru = page_lru(page);
1029 1030
			ret = 0;
			ClearPageLRU(page);
1031 1032

			del_page_from_lru_list(zone, page, lru);
1033 1034 1035 1036 1037 1038
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
1039
/*
A
Andrew Morton 已提交
1040 1041
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1042
 */
A
Andrew Morton 已提交
1043
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1044 1045
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1046 1047 1048
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1049
	unsigned long nr_scanned = 0;
1050
	unsigned long nr_reclaimed = 0;
1051
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1052 1053 1054 1055 1056

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1057
	do {
L
Linus Torvalds 已提交
1058
		struct page *page;
1059 1060 1061
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1062
		unsigned long nr_active;
1063
		unsigned int count[NR_LRU_LISTS] = { 0, };
R
Rik van Riel 已提交
1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076
		int mode = ISOLATE_INACTIVE;

		/*
		 * If we need a large contiguous chunk of memory, or have
		 * trouble getting a small set of contiguous pages, we
		 * will reclaim both active and inactive pages.
		 *
		 * We use the same threshold as pageout congestion_wait below.
		 */
		if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
			mode = ISOLATE_BOTH;
		else if (sc->order && priority < DEF_PRIORITY - 2)
			mode = ISOLATE_BOTH;
L
Linus Torvalds 已提交
1077

1078
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1079 1080 1081
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
		nr_active = clear_active_flags(&page_list, count);
1082
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1083

1084 1085 1086 1087 1088 1089 1090 1091 1092
		__mod_zone_page_state(zone, NR_ACTIVE_FILE,
						-count[LRU_ACTIVE_FILE]);
		__mod_zone_page_state(zone, NR_INACTIVE_FILE,
						-count[LRU_INACTIVE_FILE]);
		__mod_zone_page_state(zone, NR_ACTIVE_ANON,
						-count[LRU_ACTIVE_ANON]);
		__mod_zone_page_state(zone, NR_INACTIVE_ANON,
						-count[LRU_INACTIVE_ANON]);

1093
		if (scanning_global_lru(sc))
1094
			zone->pages_scanned += nr_scan;
K
KOSAKI Motohiro 已提交
1095 1096 1097 1098 1099 1100

		reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
		reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
		reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
		reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];

L
Linus Torvalds 已提交
1101 1102
		spin_unlock_irq(&zone->lru_lock);

1103
		nr_scanned += nr_scan;
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119
		nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);

		/*
		 * If we are direct reclaiming for contiguous pages and we do
		 * not reclaim everything in the list, try again and wait
		 * for IO to complete. This will stall high-order allocations
		 * but that should be acceptable to the caller
		 */
		if (nr_freed < nr_taken && !current_is_kswapd() &&
					sc->order > PAGE_ALLOC_COSTLY_ORDER) {
			congestion_wait(WRITE, HZ/10);

			/*
			 * The attempt at page out may have made some
			 * of the pages active, mark them inactive again.
			 */
1120
			nr_active = clear_active_flags(&page_list, count);
1121 1122 1123 1124 1125 1126
			count_vm_events(PGDEACTIVATE, nr_active);

			nr_freed += shrink_page_list(&page_list, sc,
							PAGEOUT_IO_SYNC);
		}

1127
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
1128 1129
		local_irq_disable();
		if (current_is_kswapd()) {
1130 1131
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
1132
		} else if (scanning_global_lru(sc))
1133
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1134

S
Shantanu Goel 已提交
1135
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1136

1137 1138 1139
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
1140
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1141 1142 1143 1144
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1145
			int lru;
L
Linus Torvalds 已提交
1146
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1147
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1148
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1149 1150 1151 1152 1153 1154 1155 1156 1157
			if (unlikely(!page_evictable(page, NULL))) {
				spin_unlock_irq(&zone->lru_lock);
				putback_lru_page(page);
				spin_lock_irq(&zone->lru_lock);
				continue;
			}
			SetPageLRU(page);
			lru = page_lru(page);
			add_page_to_lru_list(zone, page, lru);
K
KOSAKI Motohiro 已提交
1158
			if (PageActive(page)) {
1159
				int file = !!page_is_file_cache(page);
1160
				reclaim_stat->recent_rotated[file]++;
1161
			}
L
Linus Torvalds 已提交
1162 1163 1164 1165 1166 1167
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
1168
  	} while (nr_scanned < max_scan);
1169
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
1170
done:
1171
	local_irq_enable();
L
Linus Torvalds 已提交
1172
	pagevec_release(&pvec);
1173
	return nr_reclaimed;
L
Linus Torvalds 已提交
1174 1175
}

1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189
/*
 * We are about to scan this zone at a certain priority level.  If that priority
 * level is smaller (ie: more urgent) than the previous priority, then note
 * that priority level within the zone.  This is done so that when the next
 * process comes in to scan this zone, it will immediately start out at this
 * priority level rather than having to build up its own scanning priority.
 * Here, this priority affects only the reclaim-mapped threshold.
 */
static inline void note_zone_scanning_priority(struct zone *zone, int priority)
{
	if (priority < zone->prev_priority)
		zone->prev_priority = priority;
}

L
Linus Torvalds 已提交
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206
/*
 * This moves pages from the active list to the inactive list.
 *
 * We move them the other way if the page is referenced by one or more
 * processes, from rmap.
 *
 * If the pages are mostly unmapped, the processing is fast and it is
 * appropriate to hold zone->lru_lock across the whole operation.  But if
 * the pages are mapped, the processing is slow (page_referenced()) so we
 * should drop zone->lru_lock around each page.  It's impossible to balance
 * this, so instead we remove the pages from the LRU while processing them.
 * It is safe to rely on PG_active against the non-LRU pages in here because
 * nobody will play with that bit on a non-LRU page.
 *
 * The downside is that we have to touch page->_count against each page.
 * But we had to alter page->flags anyway.
 */
1207 1208


A
Andrew Morton 已提交
1209
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1210
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1211
{
1212
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1213
	int pgdeactivate = 0;
1214
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1215
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1216
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1217 1218
	struct page *page;
	struct pagevec pvec;
1219
	enum lru_list lru;
1220
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1221 1222 1223

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1224 1225
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
1226
					sc->mem_cgroup, 1, file);
1227 1228 1229 1230
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1231
	if (scanning_global_lru(sc)) {
1232
		zone->pages_scanned += pgscanned;
1233
	}
K
KOSAKI Motohiro 已提交
1234
	reclaim_stat->recent_scanned[!!file] += pgmoved;
1235

1236 1237 1238 1239
	if (file)
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
	else
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
L
Linus Torvalds 已提交
1240 1241
	spin_unlock_irq(&zone->lru_lock);

1242
	pgmoved = 0;
L
Linus Torvalds 已提交
1243 1244 1245 1246
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1247

L
Lee Schermerhorn 已提交
1248 1249 1250 1251 1252
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1253 1254 1255 1256 1257
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
		    page_referenced(page, 0, sc->mem_cgroup))
			pgmoved++;

L
Linus Torvalds 已提交
1258 1259 1260
		list_add(&page->lru, &l_inactive);
	}

1261 1262 1263 1264 1265 1266
	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);
	lru = LRU_BASE + file * LRU_FILE;

1267
	spin_lock_irq(&zone->lru_lock);
1268
	/*
1269 1270 1271 1272 1273
	 * Count referenced pages from currently used mappings as
	 * rotated, even though they are moved to the inactive list.
	 * This helps balance scan pressure between file and anonymous
	 * pages in get_scan_ratio.
	 */
K
KOSAKI Motohiro 已提交
1274
	reclaim_stat->recent_rotated[!!file] += pgmoved;
1275

1276
	pgmoved = 0;
L
Linus Torvalds 已提交
1277 1278 1279
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
N
Nick Piggin 已提交
1280
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1281
		SetPageLRU(page);
N
Nick Piggin 已提交
1282
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1283 1284
		ClearPageActive(page);

1285
		list_move(&page->lru, &zone->lru[lru].list);
K
KAMEZAWA Hiroyuki 已提交
1286
		mem_cgroup_add_lru_list(page, lru);
L
Linus Torvalds 已提交
1287 1288
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1289
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1290 1291 1292 1293 1294 1295 1296 1297 1298
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1299
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1300 1301 1302 1303 1304 1305
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}
1306 1307 1308
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
1309 1310
	if (vm_swap_full())
		pagevec_swap_free(&pvec);
L
Linus Torvalds 已提交
1311

N
Nick Piggin 已提交
1312
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1313 1314
}

1315
static int inactive_anon_is_low_global(struct zone *zone)
1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_ANON);
	inactive = zone_page_state(zone, NR_INACTIVE_ANON);

	if (inactive * zone->inactive_ratio < active)
		return 1;

	return 0;
}

1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

1340
	if (scanning_global_lru(sc))
1341 1342
		low = inactive_anon_is_low_global(zone);
	else
1343
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1344 1345 1346
	return low;
}

1347
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1348 1349
	struct zone *zone, struct scan_control *sc, int priority)
{
1350 1351
	int file = is_file_lru(lru);

1352 1353 1354 1355 1356
	if (lru == LRU_ACTIVE_FILE) {
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
		return 0;
	}

1357
	if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1358
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1359 1360
		return 0;
	}
R
Rik van Riel 已提交
1361
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378
}

/*
 * Determine how aggressively the anon and file LRU lists should be
 * scanned.  The relative value of each set of LRU lists is determined
 * by looking at the fraction of the pages scanned we did rotate back
 * onto the active list instead of evict.
 *
 * percent[0] specifies how much pressure to put on ram/swap backed
 * memory, while percent[1] determines pressure on the file LRUs.
 */
static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
					unsigned long *percent)
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1379
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1380 1381 1382 1383 1384 1385 1386 1387

	/* If we have no swap space, do not bother scanning anon pages. */
	if (nr_swap_pages <= 0) {
		percent[0] = 0;
		percent[1] = 100;
		return;
	}

1388 1389 1390 1391
	anon  = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1392

1393
	if (scanning_global_lru(sc)) {
1394 1395 1396 1397 1398 1399 1400 1401
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
		if (unlikely(file + free <= zone->pages_high)) {
			percent[0] = 100;
			percent[1] = 0;
			return;
		}
1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414
	}

	/*
	 * OK, so we have swap space and a fair amount of page cache
	 * pages.  We use the recently rotated / recently scanned
	 * ratios to determine how valuable each cache is.
	 *
	 * Because workloads change over time (and to avoid overflow)
	 * we keep these statistics as a floating average, which ends
	 * up weighing recent references more than old ones.
	 *
	 * anon in [0], file in [1]
	 */
1415
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1416
		spin_lock_irq(&zone->lru_lock);
1417 1418
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1419 1420 1421
		spin_unlock_irq(&zone->lru_lock);
	}

1422
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1423
		spin_lock_irq(&zone->lru_lock);
1424 1425
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436
		spin_unlock_irq(&zone->lru_lock);
	}

	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
	anon_prio = sc->swappiness;
	file_prio = 200 - sc->swappiness;

	/*
1437 1438 1439
	 * The amount of pressure on anon vs file pages is inversely
	 * proportional to the fraction of recently scanned pages on
	 * each list that were recently referenced and in active use.
1440
	 */
1441 1442
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1443

1444 1445
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1446 1447 1448 1449

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1450 1451
}

1452

L
Linus Torvalds 已提交
1453 1454 1455
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1456
static void shrink_zone(int priority, struct zone *zone,
1457
				struct scan_control *sc)
L
Linus Torvalds 已提交
1458
{
1459
	unsigned long nr[NR_LRU_LISTS];
1460
	unsigned long nr_to_scan;
1461
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1462
	enum lru_list l;
1463 1464
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
L
Linus Torvalds 已提交
1465

1466 1467
	get_scan_ratio(zone, sc, percent);

L
Lee Schermerhorn 已提交
1468
	for_each_evictable_lru(l) {
1469 1470
		int file = is_file_lru(l);
		int scan;
1471

1472
		scan = zone_nr_pages(zone, sc, l);
1473 1474 1475 1476
		if (priority) {
			scan >>= priority;
			scan = (scan * percent[file]) / 100;
		}
1477
		if (scanning_global_lru(sc)) {
1478
			zone->lru[l].nr_scan += scan;
1479
			nr[l] = zone->lru[l].nr_scan;
1480
			if (nr[l] >= swap_cluster_max)
1481 1482 1483
				zone->lru[l].nr_scan = 0;
			else
				nr[l] = 0;
1484 1485
		} else
			nr[l] = scan;
1486
	}
L
Linus Torvalds 已提交
1487

1488 1489
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1490
		for_each_evictable_lru(l) {
1491
			if (nr[l]) {
1492
				nr_to_scan = min(nr[l], swap_cluster_max);
1493
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1494

1495 1496
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1497
			}
L
Linus Torvalds 已提交
1498
		}
1499 1500 1501 1502 1503 1504 1505 1506
		/*
		 * On large memory systems, scan >> priority can become
		 * really large. This is fine for the starting priority;
		 * we want to put equal scanning pressure on each zone.
		 * However, if the VM has a harder time of freeing pages,
		 * with multiple processes reclaiming pages, the total
		 * freeing target can get unreasonably large.
		 */
1507
		if (nr_reclaimed > swap_cluster_max &&
1508 1509
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1510 1511
	}

1512 1513
	sc->nr_reclaimed = nr_reclaimed;

1514 1515 1516 1517
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1518
	if (inactive_anon_is_low(zone, sc))
1519 1520
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1521
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537
}

/*
 * This is the direct reclaim path, for page-allocating processes.  We only
 * try to reclaim pages from zones which will satisfy the caller's allocation
 * request.
 *
 * We reclaim from a zone even if that zone is over pages_high.  Because:
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
 * b) The zones may be over pages_high but they must go *over* pages_high to
 *    satisfy the `incremental min' zone defense algorithm.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1538
static void shrink_zones(int priority, struct zonelist *zonelist,
1539
					struct scan_control *sc)
L
Linus Torvalds 已提交
1540
{
1541
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1542
	struct zoneref *z;
1543
	struct zone *zone;
1544

1545
	sc->all_unreclaimable = 1;
1546
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1547
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1548
			continue;
1549 1550 1551 1552
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1553
		if (scanning_global_lru(sc)) {
1554 1555 1556
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1557

1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570
			if (zone_is_all_unreclaimable(zone) &&
						priority != DEF_PRIORITY)
				continue;	/* Let kswapd poll it */
			sc->all_unreclaimable = 0;
		} else {
			/*
			 * Ignore cpuset limitation here. We just want to reduce
			 * # of used pages by us regardless of memory shortage.
			 */
			sc->all_unreclaimable = 0;
			mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
							priority);
		}
1571

1572
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1573 1574
	}
}
1575

L
Linus Torvalds 已提交
1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587
/*
 * This is the main entry point to direct page reclaim.
 *
 * If a full scan of the inactive list fails to free enough memory then we
 * are "out of memory" and something needs to be killed.
 *
 * If the caller is !__GFP_FS then the probability of a failure is reasonably
 * high - the zone may be full of dirty or under-writeback pages, which this
 * caller can't do much about.  We kick pdflush and take explicit naps in the
 * hope that some of these pages can be written.  But if the allocating task
 * holds filesystem locks which prevent writeout this might not work, and the
 * allocation attempt will fail.
1588 1589 1590
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1591
 */
1592
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1593
					struct scan_control *sc)
L
Linus Torvalds 已提交
1594 1595
{
	int priority;
1596
	unsigned long ret = 0;
1597
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1598 1599
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1600
	struct zoneref *z;
1601
	struct zone *zone;
1602
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1603

1604 1605
	delayacct_freepages_start();

1606
	if (scanning_global_lru(sc))
1607 1608 1609 1610
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
1611
	if (scanning_global_lru(sc)) {
1612
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1613

1614 1615
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1616

1617
			lru_pages += zone_lru_pages(zone);
1618
		}
L
Linus Torvalds 已提交
1619 1620 1621
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1622
		sc->nr_scanned = 0;
1623 1624
		if (!priority)
			disable_swap_token();
1625
		shrink_zones(priority, zonelist, sc);
1626 1627 1628 1629
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1630
		if (scanning_global_lru(sc)) {
1631
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1632
			if (reclaim_state) {
1633
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1634 1635
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1636
		}
1637
		total_scanned += sc->nr_scanned;
1638 1639
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1640 1641 1642 1643 1644 1645 1646 1647 1648 1649
			goto out;
		}

		/*
		 * Try to write back as many pages as we just scanned.  This
		 * tends to cause slow streaming writers to write data to the
		 * disk smoothly, at the dirtying rate, which is nice.   But
		 * that's undesirable in laptop mode, where we *want* lumpy
		 * writeout.  So in laptop mode, write out the whole world.
		 */
1650 1651
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1652
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1653
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1654 1655 1656
		}

		/* Take a nap, wait for some writeback to complete */
1657
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1658
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1659
	}
1660
	/* top priority shrink_zones still had more to do? don't OOM, then */
1661
	if (!sc->all_unreclaimable && scanning_global_lru(sc))
1662
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1663
out:
1664 1665 1666 1667 1668 1669 1670 1671 1672
	/*
	 * Now that we've scanned all the zones at this priority level, note
	 * that level within the zone so that the next thread which performs
	 * scanning of this zone will immediately start out at this priority
	 * level.  This affects only the decision whether or not to bring
	 * mapped pages onto the inactive list.
	 */
	if (priority < 0)
		priority = 0;
L
Linus Torvalds 已提交
1673

1674
	if (scanning_global_lru(sc)) {
1675
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1676 1677 1678 1679 1680 1681 1682 1683

			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;

			zone->prev_priority = priority;
		}
	} else
		mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
L
Linus Torvalds 已提交
1684

1685 1686
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1687 1688 1689
	return ret;
}

1690 1691
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
								gfp_t gfp_mask)
1692 1693 1694 1695 1696
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
1697
		.may_unmap = 1,
1698 1699 1700 1701 1702 1703
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
	};

1704
	return do_try_to_free_pages(zonelist, &sc);
1705 1706
}

1707
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1708

1709
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
1710 1711 1712
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
1713 1714 1715
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
1716
		.may_unmap = 1,
1717
		.swap_cluster_max = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
1718
		.swappiness = swappiness,
1719 1720 1721 1722
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
	};
1723
	struct zonelist *zonelist;
1724

1725
	if (noswap)
1726
		sc.may_unmap = 0;
1727

1728 1729 1730 1731
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
	return do_try_to_free_pages(zonelist, &sc);
1732 1733 1734
}
#endif

L
Linus Torvalds 已提交
1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
 * they are all at pages_high.
 *
 * Returns the number of pages which were actually freed.
 *
 * There is special handling here for zones which are full of pinned pages.
 * This can happen if the pages are all mlocked, or if they are all used by
 * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
 * What we do is to detect the case where all pages in the zone have been
 * scanned twice and there has been zero successful reclaim.  Mark the zone as
 * dead and from now on, only perform a short scan.  Basically we're polling
 * the zone for when the problem goes away.
 *
 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
 * zones which have free_pages > pages_high, but once a zone is found to have
 * free_pages <= pages_high, we scan that zone and the lower zones regardless
 * of the number of free pages in the lower zones.  This interoperates with
 * the page allocator fallback scheme to ensure that aging of pages is balanced
 * across the zones.
 */
1756
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1757 1758 1759 1760
{
	int all_zones_ok;
	int priority;
	int i;
1761
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1762
	struct reclaim_state *reclaim_state = current->reclaim_state;
1763 1764
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
1765
		.may_unmap = 1,
1766 1767
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1768
		.order = order,
1769 1770
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1771
	};
1772 1773 1774 1775 1776
	/*
	 * temp_priority is used to remember the scanning priority at which
	 * this zone was successfully refilled to free_pages == pages_high.
	 */
	int temp_priority[MAX_NR_ZONES];
L
Linus Torvalds 已提交
1777 1778 1779

loop_again:
	total_scanned = 0;
1780
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1781
	sc.may_writepage = !laptop_mode;
1782
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1783

1784 1785
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1786 1787 1788 1789 1790

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
		unsigned long lru_pages = 0;

1791 1792 1793 1794
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1795 1796
		all_zones_ok = 1;

1797 1798 1799 1800 1801 1802
		/*
		 * Scan in the highmem->dma direction for the highest
		 * zone which needs scanning
		 */
		for (i = pgdat->nr_zones - 1; i >= 0; i--) {
			struct zone *zone = pgdat->node_zones + i;
L
Linus Torvalds 已提交
1803

1804 1805
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1806

1807 1808
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1809
				continue;
L
Linus Torvalds 已提交
1810

1811 1812 1813 1814
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
1815
			if (inactive_anon_is_low(zone, &sc))
1816 1817 1818
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

1819 1820 1821
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1822
				break;
L
Linus Torvalds 已提交
1823 1824
			}
		}
A
Andrew Morton 已提交
1825 1826 1827
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1828 1829 1830
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1831
			lru_pages += zone_lru_pages(zone);
L
Linus Torvalds 已提交
1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844
		}

		/*
		 * Now scan the zone in the dma->highmem direction, stopping
		 * at the last zone which needs scanning.
		 *
		 * We do this because the page allocator works in the opposite
		 * direction.  This prevents the page allocator from allocating
		 * pages behind kswapd's direction of progress, which would
		 * cause too much scanning of the lower zones.
		 */
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;
1845
			int nr_slab;
L
Linus Torvalds 已提交
1846

1847
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1848 1849
				continue;

1850 1851
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1852 1853
				continue;

1854 1855 1856
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1857
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1858
			sc.nr_scanned = 0;
1859
			note_zone_scanning_priority(zone, priority);
1860 1861 1862 1863 1864 1865
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
			if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
						end_zone, 0))
1866
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1867
			reclaim_state->reclaimed_slab = 0;
1868 1869
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1870
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1871
			total_scanned += sc.nr_scanned;
1872
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1873
				continue;
1874
			if (nr_slab == 0 && zone->pages_scanned >=
1875
						(zone_lru_pages(zone) * 6))
1876 1877
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1878 1879 1880 1881 1882 1883
			/*
			 * If we've done a decent amount of scanning and
			 * the reclaim ratio is low, start doing writepage
			 * even in laptop mode
			 */
			if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1884
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
1885 1886 1887 1888 1889 1890 1891 1892
				sc.may_writepage = 1;
		}
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
1893
		if (total_scanned && priority < DEF_PRIORITY - 2)
1894
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1895 1896 1897 1898 1899 1900 1901

		/*
		 * We do this so kswapd doesn't build up large priorities for
		 * example when it is freeing in parallel with allocators. It
		 * matches the direct reclaim path behaviour in terms of impact
		 * on zone->*_priority.
		 */
1902
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1903 1904 1905
			break;
	}
out:
1906 1907 1908 1909 1910
	/*
	 * Note within each zone the priority level at which this zone was
	 * brought into a happy state.  So that the next thread which scans this
	 * zone will start out at that priority level.
	 */
L
Linus Torvalds 已提交
1911 1912 1913
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1914
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
1915 1916 1917
	}
	if (!all_zones_ok) {
		cond_resched();
1918 1919 1920

		try_to_freeze();

1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937
		/*
		 * Fragmentation may mean that the system cannot be
		 * rebalanced for high-order allocations in all zones.
		 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
		 * it means the zones have been fully scanned and are still
		 * not balanced. For high-order allocations, there is
		 * little point trying all over again as kswapd may
		 * infinite loop.
		 *
		 * Instead, recheck all watermarks at order-0 as they
		 * are the most important. If watermarks are ok, kswapd will go
		 * back to sleep. High-order users can still perform direct
		 * reclaim if they wish.
		 */
		if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
			order = sc.order = 0;

L
Linus Torvalds 已提交
1938 1939 1940
		goto loop_again;
	}

1941
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
1942 1943 1944 1945
}

/*
 * The background pageout daemon, started as a kernel thread
1946
 * from the init process.
L
Linus Torvalds 已提交
1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965
 *
 * This basically trickles out pages so that we have _some_
 * free memory available even if there is no other activity
 * that frees anything up. This is needed for things like routing
 * etc, where we otherwise might have all activity going on in
 * asynchronous contexts that cannot page things out.
 *
 * If there are applications that are active memory-allocators
 * (most normal use), this basically shouldn't matter.
 */
static int kswapd(void *p)
{
	unsigned long order;
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
1966
	node_to_cpumask_ptr(cpumask, pgdat->node_id);
L
Linus Torvalds 已提交
1967

1968 1969
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
1970
	if (!cpumask_empty(cpumask))
1971
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
	current->reclaim_state = &reclaim_state;

	/*
	 * Tell the memory management that we're a "memory allocator",
	 * and that if we need more memory we should get access to it
	 * regardless (see "__alloc_pages()"). "kswapd" should
	 * never get caught in the normal page freeing logic.
	 *
	 * (Kswapd normally doesn't need memory anyway, but sometimes
	 * you need a small amount of memory in order to be able to
	 * page out something else, and this flag essentially protects
	 * us from recursively trying to free more memory as we're
	 * trying to free the first piece of memory in the first place).
	 */
1986
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1987
	set_freezable();
L
Linus Torvalds 已提交
1988 1989 1990 1991

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1992

L
Linus Torvalds 已提交
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
		new_order = pgdat->kswapd_max_order;
		pgdat->kswapd_max_order = 0;
		if (order < new_order) {
			/*
			 * Don't sleep if someone wants a larger 'order'
			 * allocation
			 */
			order = new_order;
		} else {
2003 2004 2005
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
2006 2007 2008 2009
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2010 2011 2012 2013 2014 2015
		if (!try_to_freeze()) {
			/* We can speed up thawing tasks if we don't call
			 * balance_pgdat after returning from the refrigerator
			 */
			balance_pgdat(pgdat, order);
		}
L
Linus Torvalds 已提交
2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
void wakeup_kswapd(struct zone *zone, int order)
{
	pg_data_t *pgdat;

2027
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2028 2029 2030
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
2031
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
2032 2033 2034
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2035
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2036
		return;
2037
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2038
		return;
2039
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2040 2041
}

2042 2043 2044 2045 2046 2047 2048 2049
unsigned long global_lru_pages(void)
{
	return global_page_state(NR_ACTIVE_ANON)
		+ global_page_state(NR_ACTIVE_FILE)
		+ global_page_state(NR_INACTIVE_ANON)
		+ global_page_state(NR_INACTIVE_FILE);
}

L
Linus Torvalds 已提交
2050 2051
#ifdef CONFIG_PM
/*
2052 2053 2054 2055 2056 2057
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
 * from LRU lists system-wide, for given pass and priority, and returns the
 * number of reclaimed pages
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
2058 2059
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
				      int pass, struct scan_control *sc)
2060 2061
{
	struct zone *zone;
2062
	unsigned long ret = 0;
2063 2064

	for_each_zone(zone) {
2065
		enum lru_list l;
2066 2067 2068

		if (!populated_zone(zone))
			continue;
2069
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2070 2071
			continue;

L
Lee Schermerhorn 已提交
2072
		for_each_evictable_lru(l) {
2073 2074 2075
			enum zone_stat_item ls = NR_LRU_BASE + l;
			unsigned long lru_pages = zone_page_state(zone, ls);

L
Lee Schermerhorn 已提交
2076
			/* For pass = 0, we don't shrink the active list */
2077 2078
			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
						l == LRU_ACTIVE_FILE))
2079 2080
				continue;

2081
			zone->lru[l].nr_scan += (lru_pages >> prio) + 1;
2082
			if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2083 2084
				unsigned long nr_to_scan;

2085
				zone->lru[l].nr_scan = 0;
2086
				nr_to_scan = min(nr_pages, lru_pages);
2087 2088 2089 2090
				ret += shrink_list(l, nr_to_scan, zone,
								sc, prio);
				if (ret >= nr_pages)
					return ret;
2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103
			}
		}
	}
	return ret;
}

/*
 * Try to free `nr_pages' of memory, system-wide, and return the number of
 * freed pages.
 *
 * Rather than trying to age LRUs the aim is to preserve the overall
 * LRU order by reclaiming preferentially
 * inactive > active > active referenced > active mapped
L
Linus Torvalds 已提交
2104
 */
2105
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2106
{
2107
	unsigned long lru_pages, nr_slab;
2108
	unsigned long ret = 0;
2109 2110 2111 2112
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2113
		.may_unmap = 0,
2114 2115
		.swap_cluster_max = nr_pages,
		.may_writepage = 1,
2116
		.isolate_pages = isolate_pages_global,
L
Linus Torvalds 已提交
2117 2118 2119
	};

	current->reclaim_state = &reclaim_state;
2120

2121
	lru_pages = global_lru_pages();
2122
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2123 2124 2125 2126 2127
	/* If slab caches are huge, it's better to hit them first */
	while (nr_slab >= lru_pages) {
		reclaim_state.reclaimed_slab = 0;
		shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
		if (!reclaim_state.reclaimed_slab)
L
Linus Torvalds 已提交
2128
			break;
2129 2130 2131 2132 2133 2134

		ret += reclaim_state.reclaimed_slab;
		if (ret >= nr_pages)
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2135
	}
2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148

	/*
	 * We try to shrink LRUs in 5 passes:
	 * 0 = Reclaim from inactive_list only
	 * 1 = Reclaim from active list but don't reclaim mapped
	 * 2 = 2nd pass of type 1
	 * 3 = Reclaim mapped (normal reclaim)
	 * 4 = 2nd pass of type 3
	 */
	for (pass = 0; pass < 5; pass++) {
		int prio;

		/* Force reclaiming mapped pages in the passes #3 and #4 */
2149
		if (pass > 2)
2150
			sc.may_unmap = 1;
2151 2152 2153 2154 2155 2156 2157 2158 2159 2160

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
			unsigned long nr_to_scan = nr_pages - ret;

			sc.nr_scanned = 0;
			ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (ret >= nr_pages)
				goto out;

			reclaim_state.reclaimed_slab = 0;
2161
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2162
					global_lru_pages());
2163 2164 2165 2166 2167
			ret += reclaim_state.reclaimed_slab;
			if (ret >= nr_pages)
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2168
				congestion_wait(WRITE, HZ / 10);
2169
		}
2170
	}
2171 2172 2173 2174 2175

	/*
	 * If ret = 0, we could not shrink LRUs, but there may be something
	 * in slab caches
	 */
2176
	if (!ret) {
2177 2178
		do {
			reclaim_state.reclaimed_slab = 0;
2179
			shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2180 2181
			ret += reclaim_state.reclaimed_slab;
		} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2182
	}
2183 2184

out:
L
Linus Torvalds 已提交
2185
	current->reclaim_state = NULL;
2186

L
Linus Torvalds 已提交
2187 2188 2189 2190 2191 2192 2193 2194
	return ret;
}
#endif

/* It's optimal to keep kswapds on the same CPUs as their memory, but
   not required for correctness.  So if the last cpu in a node goes
   away, we get changed to run anywhere: as the first one comes back,
   restore their cpu bindings. */
2195
static int __devinit cpu_callback(struct notifier_block *nfb,
2196
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2197
{
2198
	int nid;
L
Linus Torvalds 已提交
2199

2200
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2201
		for_each_node_state(nid, N_HIGH_MEMORY) {
2202 2203 2204
			pg_data_t *pgdat = NODE_DATA(nid);
			node_to_cpumask_ptr(mask, pgdat->node_id);

2205
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2206
				/* One of our CPUs online: restore mask */
2207
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2208 2209 2210 2211 2212
		}
	}
	return NOTIFY_OK;
}

2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234
/*
 * This kswapd start function will be called by init and node-hot-add.
 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
 */
int kswapd_run(int nid)
{
	pg_data_t *pgdat = NODE_DATA(nid);
	int ret = 0;

	if (pgdat->kswapd)
		return 0;

	pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
	if (IS_ERR(pgdat->kswapd)) {
		/* failure at boot is fatal */
		BUG_ON(system_state == SYSTEM_BOOTING);
		printk("Failed to start kswapd on node %d\n",nid);
		ret = -1;
	}
	return ret;
}

L
Linus Torvalds 已提交
2235 2236
static int __init kswapd_init(void)
{
2237
	int nid;
2238

L
Linus Torvalds 已提交
2239
	swap_setup();
2240
	for_each_node_state(nid, N_HIGH_MEMORY)
2241
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2242 2243 2244 2245 2246
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2247 2248 2249 2250 2251 2252 2253 2254 2255 2256

#ifdef CONFIG_NUMA
/*
 * Zone reclaim mode
 *
 * If non-zero call zone_reclaim when the number of free pages falls below
 * the watermarks.
 */
int zone_reclaim_mode __read_mostly;

2257
#define RECLAIM_OFF 0
2258
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2259 2260 2261
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2262 2263 2264 2265 2266 2267 2268
/*
 * Priority for ZONE_RECLAIM. This determines the fraction of pages
 * of a node considered for each zone_reclaim. 4 scans 1/16th of
 * a zone.
 */
#define ZONE_RECLAIM_PRIORITY 4

2269 2270 2271 2272 2273 2274
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2275 2276 2277 2278 2279 2280
/*
 * If the number of slab pages in a zone grows beyond this percentage then
 * slab reclaim needs to occur.
 */
int sysctl_min_slab_ratio = 5;

2281 2282 2283
/*
 * Try to free up some pages from this zone through reclaim.
 */
2284
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2285
{
2286
	/* Minimum pages needed in order to stay on node */
2287
	const unsigned long nr_pages = 1 << order;
2288 2289
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2290
	int priority;
2291 2292
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2293
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2294 2295
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2296
		.gfp_mask = gfp_mask,
2297
		.swappiness = vm_swappiness,
2298
		.isolate_pages = isolate_pages_global,
2299
	};
2300
	unsigned long slab_reclaimable;
2301 2302 2303

	disable_swap_token();
	cond_resched();
2304 2305 2306 2307 2308 2309
	/*
	 * We need to be able to allocate from the reserves for RECLAIM_SWAP
	 * and we also need to be able to write out pages for RECLAIM_WRITE
	 * and RECLAIM_SWAP.
	 */
	p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2310 2311
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2312

2313 2314 2315 2316 2317 2318 2319 2320 2321
	if (zone_page_state(zone, NR_FILE_PAGES) -
		zone_page_state(zone, NR_FILE_MAPPED) >
		zone->min_unmapped_pages) {
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2322
			note_zone_scanning_priority(zone, priority);
2323
			shrink_zone(priority, zone, &sc);
2324
			priority--;
2325
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2326
	}
2327

2328 2329
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2330
		/*
2331
		 * shrink_slab() does not currently allow us to determine how
2332 2333 2334 2335
		 * many pages were freed in this zone. So we take the current
		 * number of slab pages and shake the slab until it is reduced
		 * by the same nr_pages that we used for reclaiming unmapped
		 * pages.
2336
		 *
2337 2338
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2339
		 */
2340
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2341 2342
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2343
			;
2344 2345 2346 2347 2348

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2349
		sc.nr_reclaimed += slab_reclaimable -
2350
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2351 2352
	}

2353
	p->reclaim_state = NULL;
2354
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2355
	return sc.nr_reclaimed >= nr_pages;
2356
}
2357 2358 2359 2360

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2361
	int ret;
2362 2363

	/*
2364 2365
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2366
	 *
2367 2368 2369 2370 2371
	 * A small portion of unmapped file backed pages is needed for
	 * file I/O otherwise pages read by file I/O will be immediately
	 * thrown out if the zone is overallocated. So we do not reclaim
	 * if less than a specified percentage of the zone is used by
	 * unmapped file backed pages.
2372
	 */
2373
	if (zone_page_state(zone, NR_FILE_PAGES) -
2374 2375 2376
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2377
		return 0;
2378

2379 2380 2381
	if (zone_is_all_unreclaimable(zone))
		return 0;

2382
	/*
2383
	 * Do not scan if the allocation should not be delayed.
2384
	 */
2385
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2386 2387 2388 2389 2390 2391 2392 2393
			return 0;

	/*
	 * Only run zone reclaim on the local zone or on zones that do not
	 * have associated processors. This will favor the local processor
	 * over remote processors and spread off node memory allocations
	 * as wide as possible.
	 */
2394
	node_id = zone_to_nid(zone);
2395
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2396
		return 0;
2397 2398 2399 2400 2401 2402 2403

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
		return 0;
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

	return ret;
2404
}
2405
#endif
L
Lee Schermerhorn 已提交
2406 2407 2408 2409 2410 2411 2412 2413

#ifdef CONFIG_UNEVICTABLE_LRU
/*
 * page_evictable - test whether a page is evictable
 * @page: the page to test
 * @vma: the VMA in which the page is or will be mapped, may be NULL
 *
 * Test whether page is evictable--i.e., should be placed on active/inactive
N
Nick Piggin 已提交
2414 2415
 * lists vs unevictable list.  The vma argument is !NULL when called from the
 * fault path to determine how to instantate a new page.
L
Lee Schermerhorn 已提交
2416 2417
 *
 * Reasons page might not be evictable:
2418
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2419
 * (2) page is part of an mlocked VMA
2420
 *
L
Lee Schermerhorn 已提交
2421 2422 2423 2424
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2425 2426 2427
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2428 2429
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2430 2431 2432

	return 1;
}
2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452

/**
 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
 * @page: page to check evictability and move to appropriate lru list
 * @zone: zone page is in
 *
 * Checks a page for evictability and moves the page to the appropriate
 * zone lru list.
 *
 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
 * have PageUnevictable set.
 */
static void check_move_unevictable_page(struct page *page, struct zone *zone)
{
	VM_BUG_ON(PageActive(page));

retry:
	ClearPageUnevictable(page);
	if (page_evictable(page, NULL)) {
		enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2453

2454 2455
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2456
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2457 2458 2459 2460 2461 2462 2463 2464
		__inc_zone_state(zone, NR_INACTIVE_ANON + l);
		__count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		/*
		 * rotate unevictable list
		 */
		SetPageUnevictable(page);
		list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
K
KAMEZAWA Hiroyuki 已提交
2465
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524
		if (page_evictable(page, NULL))
			goto retry;
	}
}

/**
 * scan_mapping_unevictable_pages - scan an address space for evictable pages
 * @mapping: struct address_space to scan for evictable pages
 *
 * Scan all pages in mapping.  Check unevictable pages for
 * evictability and move them to the appropriate zone lru list.
 */
void scan_mapping_unevictable_pages(struct address_space *mapping)
{
	pgoff_t next = 0;
	pgoff_t end   = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
			 PAGE_CACHE_SHIFT;
	struct zone *zone;
	struct pagevec pvec;

	if (mapping->nrpages == 0)
		return;

	pagevec_init(&pvec, 0);
	while (next < end &&
		pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
		int i;
		int pg_scanned = 0;

		zone = NULL;

		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];
			pgoff_t page_index = page->index;
			struct zone *pagezone = page_zone(page);

			pg_scanned++;
			if (page_index > next)
				next = page_index;
			next++;

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irq(&zone->lru_lock);
				zone = pagezone;
				spin_lock_irq(&zone->lru_lock);
			}

			if (PageLRU(page) && PageUnevictable(page))
				check_move_unevictable_page(page, zone);
		}
		if (zone)
			spin_unlock_irq(&zone->lru_lock);
		pagevec_release(&pvec);

		count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
	}

}
2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536

/**
 * scan_zone_unevictable_pages - check unevictable list for evictable pages
 * @zone - zone of which to scan the unevictable list
 *
 * Scan @zone's unevictable LRU lists to check for pages that have become
 * evictable.  Move those that have to @zone's inactive list where they
 * become candidates for reclaim, unless shrink_inactive_zone() decides
 * to reactivate them.  Pages that are still unevictable are rotated
 * back onto @zone's unevictable list.
 */
#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2537
static void scan_zone_unevictable_pages(struct zone *zone)
2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578
{
	struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
	unsigned long scan;
	unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);

	while (nr_to_scan > 0) {
		unsigned long batch_size = min(nr_to_scan,
						SCAN_UNEVICTABLE_BATCH_SIZE);

		spin_lock_irq(&zone->lru_lock);
		for (scan = 0;  scan < batch_size; scan++) {
			struct page *page = lru_to_page(l_unevictable);

			if (!trylock_page(page))
				continue;

			prefetchw_prev_lru_page(page, l_unevictable, flags);

			if (likely(PageLRU(page) && PageUnevictable(page)))
				check_move_unevictable_page(page, zone);

			unlock_page(page);
		}
		spin_unlock_irq(&zone->lru_lock);

		nr_to_scan -= batch_size;
	}
}


/**
 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
 *
 * A really big hammer:  scan all zones' unevictable LRU lists to check for
 * pages that have become evictable.  Move those back to the zones'
 * inactive list where they become candidates for reclaim.
 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
 * and we add swap to the system.  As such, it runs in the context of a task
 * that has possibly/probably made some previously unevictable pages
 * evictable.
 */
2579
static void scan_all_zones_unevictable_pages(void)
2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653
{
	struct zone *zone;

	for_each_zone(zone) {
		scan_zone_unevictable_pages(zone);
	}
}

/*
 * scan_unevictable_pages [vm] sysctl handler.  On demand re-scan of
 * all nodes' unevictable lists for evictable pages
 */
unsigned long scan_unevictable_pages;

int scan_unevictable_handler(struct ctl_table *table, int write,
			   struct file *file, void __user *buffer,
			   size_t *length, loff_t *ppos)
{
	proc_doulongvec_minmax(table, write, file, buffer, length, ppos);

	if (write && *(unsigned long *)table->data)
		scan_all_zones_unevictable_pages();

	scan_unevictable_pages = 0;
	return 0;
}

/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

static ssize_t read_scan_unevictable_node(struct sys_device *dev,
					  struct sysdev_attribute *attr,
					  char *buf)
{
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

static ssize_t write_scan_unevictable_node(struct sys_device *dev,
					   struct sysdev_attribute *attr,
					const char *buf, size_t count)
{
	struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
	struct zone *zone;
	unsigned long res;
	unsigned long req = strict_strtoul(buf, 10, &res);

	if (!req)
		return 1;	/* zero is no-op */

	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
		if (!populated_zone(zone))
			continue;
		scan_zone_unevictable_pages(zone);
	}
	return 1;
}


static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
	return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
}

void scan_unevictable_unregister_node(struct node *node)
{
	sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
}

L
Lee Schermerhorn 已提交
2654
#endif