vmscan.c 92.5 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
/*
 *  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>
16
#include <linux/gfp.h>
L
Linus Torvalds 已提交
17 18 19 20 21
#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
#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>
35
#include <linux/compaction.h>
L
Linus Torvalds 已提交
36 37
#include <linux/notifier.h>
#include <linux/rwsem.h>
38
#include <linux/delay.h>
39
#include <linux/kthread.h>
40
#include <linux/freezer.h>
41
#include <linux/memcontrol.h>
42
#include <linux/delayacct.h>
43
#include <linux/sysctl.h>
44
#include <linux/oom.h>
45
#include <linux/prefetch.h>
L
Linus Torvalds 已提交
46 47 48 49 50 51

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

#include <linux/swapops.h>

52 53
#include "internal.h"

54 55 56
#define CREATE_TRACE_POINTS
#include <trace/events/vmscan.h>

57
/*
58 59 60 61 62
 * reclaim_mode determines how the inactive list is shrunk
 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
 * RECLAIM_MODE_ASYNC:  Do not block
 * RECLAIM_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 64
 *			page from the LRU and reclaim all pages within a
 *			naturally aligned range
65
 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66
 *			order-0 pages and then compact the zone
67
 */
68 69 70 71 72 73
typedef unsigned __bitwise__ reclaim_mode_t;
#define RECLAIM_MODE_SINGLE		((__force reclaim_mode_t)0x01u)
#define RECLAIM_MODE_ASYNC		((__force reclaim_mode_t)0x02u)
#define RECLAIM_MODE_SYNC		((__force reclaim_mode_t)0x04u)
#define RECLAIM_MODE_LUMPYRECLAIM	((__force reclaim_mode_t)0x08u)
#define RECLAIM_MODE_COMPACTION		((__force reclaim_mode_t)0x10u)
74

L
Linus Torvalds 已提交
75 76 77 78
struct scan_control {
	/* Incremented by the number of inactive pages that were scanned */
	unsigned long nr_scanned;

79 80 81
	/* Number of pages freed so far during a call to shrink_zones() */
	unsigned long nr_reclaimed;

82 83 84
	/* How many pages shrink_list() should reclaim */
	unsigned long nr_to_reclaim;

85 86
	unsigned long hibernation_mode;

L
Linus Torvalds 已提交
87
	/* This context's GFP mask */
A
Al Viro 已提交
88
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
89 90 91

	int may_writepage;

92 93
	/* Can mapped pages be reclaimed? */
	int may_unmap;
94

95 96 97
	/* Can pages be swapped as part of reclaim? */
	int may_swap;

98
	int swappiness;
99

A
Andy Whitcroft 已提交
100
	int order;
101

102
	/*
103 104
	 * Intend to reclaim enough continuous memory rather than reclaim
	 * enough amount of memory. i.e, mode for high order allocation.
105
	 */
106
	reclaim_mode_t reclaim_mode;
107

108 109 110
	/* Which cgroup do we reclaim from */
	struct mem_cgroup *mem_cgroup;

111 112 113 114 115
	/*
	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
	 * are scanned.
	 */
	nodemask_t	*nodemask;
L
Linus Torvalds 已提交
116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151
};

#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;
152
long vm_total_pages;	/* The total number of pages which the VM controls */
L
Linus Torvalds 已提交
153 154 155 156

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

157
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
158
#define scanning_global_lru(sc)	(!(sc)->mem_cgroup)
159
#else
160
#define scanning_global_lru(sc)	(1)
161 162
#endif

163 164 165
static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
						  struct scan_control *sc)
{
166
	if (!scanning_global_lru(sc))
K
KOSAKI Motohiro 已提交
167 168
		return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);

169 170 171
	return &zone->reclaim_stat;
}

172 173
static unsigned long zone_nr_lru_pages(struct zone *zone,
				struct scan_control *sc, enum lru_list lru)
174
{
175
	if (!scanning_global_lru(sc))
176 177
		return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);

178 179 180 181
	return zone_page_state(zone, NR_LRU_BASE + lru);
}


L
Linus Torvalds 已提交
182 183 184
/*
 * Add a shrinker callback to be called from the vm
 */
185
void register_shrinker(struct shrinker *shrinker)
L
Linus Torvalds 已提交
186
{
187 188 189 190
	shrinker->nr = 0;
	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
L
Linus Torvalds 已提交
191
}
192
EXPORT_SYMBOL(register_shrinker);
L
Linus Torvalds 已提交
193 194 195 196

/*
 * Remove one
 */
197
void unregister_shrinker(struct shrinker *shrinker)
L
Linus Torvalds 已提交
198 199 200 201 202
{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
203
EXPORT_SYMBOL(unregister_shrinker);
L
Linus Torvalds 已提交
204 205 206 207 208 209 210 211 212 213

#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
214
 * If the vm encountered mapped pages on the LRU it increase the pressure on
L
Linus Torvalds 已提交
215 216 217 218 219 220 221
 * 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.
222 223
 *
 * Returns the number of slab objects which we shrunk.
L
Linus Torvalds 已提交
224
 */
225 226
unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
			unsigned long lru_pages)
L
Linus Torvalds 已提交
227 228
{
	struct shrinker *shrinker;
229
	unsigned long ret = 0;
L
Linus Torvalds 已提交
230 231 232 233

	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

234 235 236 237 238
	if (!down_read_trylock(&shrinker_rwsem)) {
		/* Assume we'll be able to shrink next time */
		ret = 1;
		goto out;
	}
L
Linus Torvalds 已提交
239 240 241 242

	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
243
		unsigned long max_pass;
L
Linus Torvalds 已提交
244

245
		max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
L
Linus Torvalds 已提交
246
		delta = (4 * scanned) / shrinker->seeks;
247
		delta *= max_pass;
L
Linus Torvalds 已提交
248 249
		do_div(delta, lru_pages + 1);
		shrinker->nr += delta;
250
		if (shrinker->nr < 0) {
251 252 253
			printk(KERN_ERR "shrink_slab: %pF negative objects to "
			       "delete nr=%ld\n",
			       shrinker->shrink, shrinker->nr);
254 255 256 257 258 259 260 261 262 263
			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
264 265 266 267 268 269 270

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

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
271
			int nr_before;
L
Linus Torvalds 已提交
272

273 274 275
			nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
								gfp_mask);
L
Linus Torvalds 已提交
276 277
			if (shrink_ret == -1)
				break;
278 279
			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
280
			count_vm_events(SLABS_SCANNED, this_scan);
L
Linus Torvalds 已提交
281 282 283 284 285 286 287 288
			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
289 290
out:
	cond_resched();
291
	return ret;
L
Linus Torvalds 已提交
292 293
}

294
static void set_reclaim_mode(int priority, struct scan_control *sc,
295 296
				   bool sync)
{
297
	reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
298 299

	/*
300 301 302
	 * Initially assume we are entering either lumpy reclaim or
	 * reclaim/compaction.Depending on the order, we will either set the
	 * sync mode or just reclaim order-0 pages later.
303
	 */
304
	if (COMPACTION_BUILD)
305
		sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
306
	else
307
		sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
308 309

	/*
310 311 312
	 * Avoid using lumpy reclaim or reclaim/compaction if possible by
	 * restricting when its set to either costly allocations or when
	 * under memory pressure
313 314
	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
315
		sc->reclaim_mode |= syncmode;
316
	else if (sc->order && priority < DEF_PRIORITY - 2)
317
		sc->reclaim_mode |= syncmode;
318
	else
319
		sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
320 321
}

322
static void reset_reclaim_mode(struct scan_control *sc)
323
{
324
	sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
325 326
}

L
Linus Torvalds 已提交
327 328
static inline int is_page_cache_freeable(struct page *page)
{
329 330 331 332 333
	/*
	 * A freeable page cache page is referenced only by the caller
	 * that isolated the page, the page cache radix tree and
	 * optional buffer heads at page->private.
	 */
334
	return page_count(page) - page_has_private(page) == 2;
L
Linus Torvalds 已提交
335 336
}

337 338
static int may_write_to_queue(struct backing_dev_info *bdi,
			      struct scan_control *sc)
L
Linus Torvalds 已提交
339
{
340
	if (current->flags & PF_SWAPWRITE)
L
Linus Torvalds 已提交
341 342 343 344 345
		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
346 347 348 349

	/* lumpy reclaim for hugepage often need a lot of write */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		return 1;
L
Linus Torvalds 已提交
350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367
	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)
{
J
Jens Axboe 已提交
368
	lock_page(page);
369 370
	if (page_mapping(page) == mapping)
		mapping_set_error(mapping, error);
L
Linus Torvalds 已提交
371 372 373
	unlock_page(page);
}

374 375 376 377 378 379 380 381 382 383 384 385
/* 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
386
/*
A
Andrew Morton 已提交
387 388
 * pageout is called by shrink_page_list() for each dirty page.
 * Calls ->writepage().
L
Linus Torvalds 已提交
389
 */
390
static pageout_t pageout(struct page *page, struct address_space *mapping,
391
			 struct scan_control *sc)
L
Linus Torvalds 已提交
392 393 394 395 396 397 398 399
{
	/*
	 * 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.
	 *
400
	 * If this process is currently in __generic_file_aio_write() against
L
Linus Torvalds 已提交
401 402 403 404 405 406 407 408 409 410 411 412 413 414 415
	 * 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.
	 */
	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.
		 */
416
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
417 418
			if (try_to_free_buffers(page)) {
				ClearPageDirty(page);
419
				printk("%s: orphaned page\n", __func__);
L
Linus Torvalds 已提交
420 421 422 423 424 425 426
				return PAGE_CLEAN;
			}
		}
		return PAGE_KEEP;
	}
	if (mapping->a_ops->writepage == NULL)
		return PAGE_ACTIVATE;
427
	if (!may_write_to_queue(mapping->backing_dev_info, sc))
L
Linus Torvalds 已提交
428 429 430 431 432 433 434
		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,
435 436
			.range_start = 0,
			.range_end = LLONG_MAX,
L
Linus Torvalds 已提交
437 438 439 440 441 442 443
			.for_reclaim = 1,
		};

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
444
		if (res == AOP_WRITEPAGE_ACTIVATE) {
L
Linus Torvalds 已提交
445 446 447
			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
448 449 450 451 452 453

		/*
		 * 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.
		 */
454
		if (PageWriteback(page) &&
455
		    (sc->reclaim_mode & RECLAIM_MODE_SYNC))
456 457
			wait_on_page_writeback(page);

L
Linus Torvalds 已提交
458 459 460 461
		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
462
		trace_mm_vmscan_writepage(page,
463
			trace_reclaim_flags(page, sc->reclaim_mode));
464
		inc_zone_page_state(page, NR_VMSCAN_WRITE);
L
Linus Torvalds 已提交
465 466 467 468 469 470
		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

471
/*
N
Nick Piggin 已提交
472 473
 * Same as remove_mapping, but if the page is removed from the mapping, it
 * gets returned with a refcount of 0.
474
 */
N
Nick Piggin 已提交
475
static int __remove_mapping(struct address_space *mapping, struct page *page)
476
{
477 478
	BUG_ON(!PageLocked(page));
	BUG_ON(mapping != page_mapping(page));
479

N
Nick Piggin 已提交
480
	spin_lock_irq(&mapping->tree_lock);
481
	/*
N
Nick Piggin 已提交
482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504
	 * 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.
505
	 */
N
Nick Piggin 已提交
506
	if (!page_freeze_refs(page, 2))
507
		goto cannot_free;
N
Nick Piggin 已提交
508 509 510
	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
	if (unlikely(PageDirty(page))) {
		page_unfreeze_refs(page, 2);
511
		goto cannot_free;
N
Nick Piggin 已提交
512
	}
513 514 515 516

	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
N
Nick Piggin 已提交
517
		spin_unlock_irq(&mapping->tree_lock);
518
		swapcache_free(swap, page);
N
Nick Piggin 已提交
519
	} else {
520 521 522 523
		void (*freepage)(struct page *);

		freepage = mapping->a_ops->freepage;

524
		__delete_from_page_cache(page);
N
Nick Piggin 已提交
525
		spin_unlock_irq(&mapping->tree_lock);
526
		mem_cgroup_uncharge_cache_page(page);
527 528 529

		if (freepage != NULL)
			freepage(page);
530 531 532 533 534
	}

	return 1;

cannot_free:
N
Nick Piggin 已提交
535
	spin_unlock_irq(&mapping->tree_lock);
536 537 538
	return 0;
}

N
Nick Piggin 已提交
539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558
/*
 * 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
559 560 561 562 563 564 565 566 567 568 569 570 571
/**
 * 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.
 */
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
572
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
573 574 575 576 577 578 579 580 581 582 583 584 585

	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.
		 */
586
		lru = active + page_lru_base_type(page);
L
Lee Schermerhorn 已提交
587 588 589 590 591 592 593 594
		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);
595 596 597 598 599 600 601 602 603 604
		/*
		 * When racing with an mlock clearing (page is
		 * unlocked), make sure that if the other thread does
		 * not observe our setting of PG_lru and fails
		 * isolation, we see PG_mlocked cleared below and move
		 * the page back to the evictable list.
		 *
		 * The other side is TestClearPageMlocked().
		 */
		smp_mb();
L
Lee Schermerhorn 已提交
605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622
	}

	/*
	 * 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.
		 */
	}

623 624 625 626 627
	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
628 629 630
	put_page(page);		/* drop ref from isolate */
}

631 632 633
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
634
	PAGEREF_KEEP,
635 636 637 638 639 640
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
641
	int referenced_ptes, referenced_page;
642 643
	unsigned long vm_flags;

644 645
	referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
	referenced_page = TestClearPageReferenced(page);
646 647

	/* Lumpy reclaim - ignore references */
648
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
649 650 651 652 653 654 655 656 657
		return PAGEREF_RECLAIM;

	/*
	 * Mlock lost the isolation race with us.  Let try_to_unmap()
	 * move the page to the unevictable list.
	 */
	if (vm_flags & VM_LOCKED)
		return PAGEREF_RECLAIM;

658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681
	if (referenced_ptes) {
		if (PageAnon(page))
			return PAGEREF_ACTIVATE;
		/*
		 * All mapped pages start out with page table
		 * references from the instantiating fault, so we need
		 * to look twice if a mapped file page is used more
		 * than once.
		 *
		 * Mark it and spare it for another trip around the
		 * inactive list.  Another page table reference will
		 * lead to its activation.
		 *
		 * Note: the mark is set for activated pages as well
		 * so that recently deactivated but used pages are
		 * quickly recovered.
		 */
		SetPageReferenced(page);

		if (referenced_page)
			return PAGEREF_ACTIVATE;

		return PAGEREF_KEEP;
	}
682 683

	/* Reclaim if clean, defer dirty pages to writeback */
684
	if (referenced_page && !PageSwapBacked(page))
685 686 687
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
688 689
}

690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707
static noinline_for_stack void free_page_list(struct list_head *free_pages)
{
	struct pagevec freed_pvec;
	struct page *page, *tmp;

	pagevec_init(&freed_pvec, 1);

	list_for_each_entry_safe(page, tmp, free_pages, lru) {
		list_del(&page->lru);
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
	}

	pagevec_free(&freed_pvec);
}

L
Linus Torvalds 已提交
708
/*
A
Andrew Morton 已提交
709
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
710
 */
A
Andrew Morton 已提交
711
static unsigned long shrink_page_list(struct list_head *page_list,
712
				      struct zone *zone,
713
				      struct scan_control *sc)
L
Linus Torvalds 已提交
714 715
{
	LIST_HEAD(ret_pages);
716
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
717
	int pgactivate = 0;
718 719
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
720
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
721 722 723 724

	cond_resched();

	while (!list_empty(page_list)) {
725
		enum page_references references;
L
Linus Torvalds 已提交
726 727 728 729 730 731 732 733 734
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;

		cond_resched();

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

N
Nick Piggin 已提交
735
		if (!trylock_page(page))
L
Linus Torvalds 已提交
736 737
			goto keep;

N
Nick Piggin 已提交
738
		VM_BUG_ON(PageActive(page));
739
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
740 741

		sc->nr_scanned++;
742

N
Nick Piggin 已提交
743 744
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
745

746
		if (!sc->may_unmap && page_mapped(page))
747 748
			goto keep_locked;

L
Linus Torvalds 已提交
749 750 751 752
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

753 754 755 756 757 758 759 760 761 762 763 764
		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.
			 */
765
			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
766
			    may_enter_fs)
767
				wait_on_page_writeback(page);
768 769 770 771
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
772
		}
L
Linus Torvalds 已提交
773

774 775 776
		references = page_check_references(page, sc);
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
777
			goto activate_locked;
778 779
		case PAGEREF_KEEP:
			goto keep_locked;
780 781 782 783
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
784 785 786 787 788

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
789
		if (PageAnon(page) && !PageSwapCache(page)) {
790 791
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
792
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
793
				goto activate_locked;
794
			may_enter_fs = 1;
N
Nick Piggin 已提交
795
		}
L
Linus Torvalds 已提交
796 797 798 799 800 801 802 803

		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) {
804
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
805 806 807 808
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
809 810
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
811 812 813 814 815 816
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
817 818
			nr_dirty++;

819
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
820
				goto keep_locked;
821
			if (!may_enter_fs)
L
Linus Torvalds 已提交
822
				goto keep_locked;
823
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
824 825 826
				goto keep_locked;

			/* Page is dirty, try to write it out here */
827
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
828
			case PAGE_KEEP:
829
				nr_congested++;
L
Linus Torvalds 已提交
830 831 832 833
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
834 835 836
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
837
					goto keep;
838

L
Linus Torvalds 已提交
839 840 841 842
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
843
				if (!trylock_page(page))
L
Linus Torvalds 已提交
844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
					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
863
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
864 865 866 867 868 869 870 871 872 873
		 * 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.
		 */
874
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
875 876
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892
			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
893 894
		}

N
Nick Piggin 已提交
895
		if (!mapping || !__remove_mapping(mapping, page))
896
			goto keep_locked;
L
Linus Torvalds 已提交
897

N
Nick Piggin 已提交
898 899 900 901 902 903 904 905
		/*
		 * 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
906
free_it:
907
		nr_reclaimed++;
908 909 910 911 912 913

		/*
		 * Is there need to periodically free_page_list? It would
		 * appear not as the counts should be low
		 */
		list_add(&page->lru, &free_pages);
L
Linus Torvalds 已提交
914 915
		continue;

N
Nick Piggin 已提交
916
cull_mlocked:
917 918
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
919 920
		unlock_page(page);
		putback_lru_page(page);
921
		reset_reclaim_mode(sc);
N
Nick Piggin 已提交
922 923
		continue;

L
Linus Torvalds 已提交
924
activate_locked:
925 926
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
927
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
928
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
929 930 931 932 933
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
934
		reset_reclaim_mode(sc);
935
keep_lumpy:
L
Linus Torvalds 已提交
936
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
937
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
938
	}
939

940 941 942 943 944 945
	/*
	 * Tag a zone as congested if all the dirty pages encountered were
	 * backed by a congested BDI. In this case, reclaimers should just
	 * back off and wait for congestion to clear because further reclaim
	 * will encounter the same problem
	 */
K
KAMEZAWA Hiroyuki 已提交
946
	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
947 948
		zone_set_flag(zone, ZONE_CONGESTED);

949 950
	free_page_list(&free_pages);

L
Linus Torvalds 已提交
951
	list_splice(&ret_pages, page_list);
952
	count_vm_events(PGACTIVATE, pgactivate);
953
	return nr_reclaimed;
L
Linus Torvalds 已提交
954 955
}

A
Andy Whitcroft 已提交
956 957 958 959 960 961 962 963 964 965
/*
 * 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.
 */
966
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
967 968 969 970 971 972 973 974 975 976 977 978 979 980 981
{
	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;

982
	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
983 984
		return ret;

L
Lee Schermerhorn 已提交
985 986 987 988 989 990 991 992
	/*
	 * 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
993
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
994

A
Andy Whitcroft 已提交
995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007
	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;
	}

	return ret;
}

L
Linus Torvalds 已提交
1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021
/*
 * 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
1022 1023
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
1024
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
1025 1026 1027
 *
 * returns how many pages were moved onto *@dst.
 */
1028 1029
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1030
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
1031
{
1032
	unsigned long nr_taken = 0;
1033 1034 1035
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1036
	unsigned long scan;
L
Linus Torvalds 已提交
1037

1038
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1039 1040 1041 1042 1043 1044
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1045 1046 1047
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1048
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1049

1050
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1051 1052
		case 0:
			list_move(&page->lru, dst);
1053
			mem_cgroup_del_lru(page);
1054
			nr_taken += hpage_nr_pages(page);
A
Andy Whitcroft 已提交
1055 1056 1057 1058 1059
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
1060
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
1061
			continue;
1062

A
Andy Whitcroft 已提交
1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074
		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
L
Lucas De Marchi 已提交
1075
		 * as the mem_map is guaranteed valid out to MAX_ORDER,
A
Andy Whitcroft 已提交
1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094
		 * 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);
1095

A
Andy Whitcroft 已提交
1096 1097
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1098
				break;
1099 1100 1101 1102 1103 1104 1105

			/*
			 * If we don't have enough swap space, reclaiming of
			 * anon page which don't already have a swap slot is
			 * pointless.
			 */
			if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1106 1107
			    !PageSwapCache(cursor_page))
				break;
1108

1109
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
1110
				list_move(&cursor_page->lru, dst);
1111
				mem_cgroup_del_lru(cursor_page);
1112
				nr_taken += hpage_nr_pages(page);
1113 1114 1115
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1116
				scan++;
1117
			} else {
1118 1119 1120 1121
				/* the page is freed already. */
				if (!page_count(cursor_page))
					continue;
				break;
A
Andy Whitcroft 已提交
1122 1123
			}
		}
1124 1125 1126 1127

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1128 1129 1130
	}

	*scanned = scan;
1131 1132 1133 1134 1135 1136

	trace_mm_vmscan_lru_isolate(order,
			nr_to_scan, scan,
			nr_taken,
			nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
			mode);
L
Linus Torvalds 已提交
1137 1138 1139
	return nr_taken;
}

1140 1141 1142 1143
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
1144
					int active, int file)
1145
{
1146
	int lru = LRU_BASE;
1147
	if (active)
1148 1149 1150 1151
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1152
								mode, file);
1153 1154
}

A
Andy Whitcroft 已提交
1155 1156 1157 1158
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1159 1160
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1161 1162
{
	int nr_active = 0;
1163
	int lru;
A
Andy Whitcroft 已提交
1164 1165
	struct page *page;

1166
	list_for_each_entry(page, page_list, lru) {
1167
		int numpages = hpage_nr_pages(page);
1168
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1169
		if (PageActive(page)) {
1170
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1171
			ClearPageActive(page);
1172
			nr_active += numpages;
A
Andy Whitcroft 已提交
1173
		}
1174
		if (count)
1175
			count[lru] += numpages;
1176
	}
A
Andy Whitcroft 已提交
1177 1178 1179 1180

	return nr_active;
}

1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
/**
 * 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
1192 1193 1194
 * 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.
1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209
 *
 * 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;

1210 1211
	VM_BUG_ON(!page_count(page));

1212 1213 1214 1215
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
1216
		if (PageLRU(page)) {
L
Lee Schermerhorn 已提交
1217
			int lru = page_lru(page);
1218
			ret = 0;
1219
			get_page(page);
1220
			ClearPageLRU(page);
1221 1222

			del_page_from_lru_list(zone, page, lru);
1223 1224 1225 1226 1227 1228
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253
/*
 * Are there way too many processes in the direct reclaim path already?
 */
static int too_many_isolated(struct zone *zone, int file,
		struct scan_control *sc)
{
	unsigned long inactive, isolated;

	if (current_is_kswapd())
		return 0;

	if (!scanning_global_lru(sc))
		return 0;

	if (file) {
		inactive = zone_page_state(zone, NR_INACTIVE_FILE);
		isolated = zone_page_state(zone, NR_ISOLATED_FILE);
	} else {
		inactive = zone_page_state(zone, NR_INACTIVE_ANON);
		isolated = zone_page_state(zone, NR_ISOLATED_ANON);
	}

	return isolated > inactive;
}

1254 1255 1256 1257
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1258
putback_lru_pages(struct zone *zone, struct scan_control *sc,
1259 1260 1261 1262 1263
				unsigned long nr_anon, unsigned long nr_file,
				struct list_head *page_list)
{
	struct page *page;
	struct pagevec pvec;
1264
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282

	pagevec_init(&pvec, 1);

	/*
	 * Put back any unfreeable pages.
	 */
	spin_lock(&zone->lru_lock);
	while (!list_empty(page_list)) {
		int lru;
		page = lru_to_page(page_list);
		VM_BUG_ON(PageLRU(page));
		list_del(&page->lru);
		if (unlikely(!page_evictable(page, NULL))) {
			spin_unlock_irq(&zone->lru_lock);
			putback_lru_page(page);
			spin_lock_irq(&zone->lru_lock);
			continue;
		}
1283
		SetPageLRU(page);
1284
		lru = page_lru(page);
1285
		add_page_to_lru_list(zone, page, lru);
1286 1287
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1288 1289
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303
		}
		if (!pagevec_add(&pvec, page)) {
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);

	spin_unlock_irq(&zone->lru_lock);
	pagevec_release(&pvec);
}

1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334
static noinline_for_stack void update_isolated_counts(struct zone *zone,
					struct scan_control *sc,
					unsigned long *nr_anon,
					unsigned long *nr_file,
					struct list_head *isolated_list)
{
	unsigned long nr_active;
	unsigned int count[NR_LRU_LISTS] = { 0, };
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);

	nr_active = clear_active_flags(isolated_list, count);
	__count_vm_events(PGDEACTIVATE, nr_active);

	__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]);

	*nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
	*nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);

	reclaim_stat->recent_scanned[0] += *nr_anon;
	reclaim_stat->recent_scanned[1] += *nr_file;
}

1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354
/*
 * Returns true if the caller should wait to clean dirty/writeback pages.
 *
 * If we are direct reclaiming for contiguous pages and we do not reclaim
 * everything in the list, try again and wait for writeback IO to complete.
 * This will stall high-order allocations noticeably. Only do that when really
 * need to free the pages under high memory pressure.
 */
static inline bool should_reclaim_stall(unsigned long nr_taken,
					unsigned long nr_freed,
					int priority,
					struct scan_control *sc)
{
	int lumpy_stall_priority;

	/* kswapd should not stall on sync IO */
	if (current_is_kswapd())
		return false;

	/* Only stall on lumpy reclaim */
1355
	if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375
		return false;

	/* If we have relaimed everything on the isolated list, no stall */
	if (nr_freed == nr_taken)
		return false;

	/*
	 * For high-order allocations, there are two stall thresholds.
	 * High-cost allocations stall immediately where as lower
	 * order allocations such as stacks require the scanning
	 * priority to be much higher before stalling.
	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		lumpy_stall_priority = DEF_PRIORITY;
	else
		lumpy_stall_priority = DEF_PRIORITY / 3;

	return priority <= lumpy_stall_priority;
}

L
Linus Torvalds 已提交
1376
/*
A
Andrew Morton 已提交
1377 1378
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1379
 */
1380 1381 1382
static noinline_for_stack unsigned long
shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1383 1384
{
	LIST_HEAD(page_list);
1385
	unsigned long nr_scanned;
1386
	unsigned long nr_reclaimed = 0;
1387 1388 1389
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1390

1391
	while (unlikely(too_many_isolated(zone, file, sc))) {
1392
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1393 1394 1395 1396 1397 1398

		/* We are about to die and free our memory. Return now. */
		if (fatal_signal_pending(current))
			return SWAP_CLUSTER_MAX;
	}

1399
	set_reclaim_mode(priority, sc, false);
L
Linus Torvalds 已提交
1400 1401
	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1402

1403 1404 1405
	if (scanning_global_lru(sc)) {
		nr_taken = isolate_pages_global(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1406
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1407
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418
			zone, 0, file);
		zone->pages_scanned += nr_scanned;
		if (current_is_kswapd())
			__count_zone_vm_events(PGSCAN_KSWAPD, zone,
					       nr_scanned);
		else
			__count_zone_vm_events(PGSCAN_DIRECT, zone,
					       nr_scanned);
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1419
			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1420
					ISOLATE_BOTH : ISOLATE_INACTIVE,
1421 1422 1423 1424 1425 1426 1427
			zone, sc->mem_cgroup,
			0, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
	}
1428

1429 1430 1431 1432
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1433

1434
	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1435

1436
	spin_unlock_irq(&zone->lru_lock);
1437

1438
	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1439

1440 1441
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1442
		set_reclaim_mode(priority, sc, true);
1443
		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1444
	}
1445

1446 1447 1448 1449
	local_irq_disable();
	if (current_is_kswapd())
		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
N
Nick Piggin 已提交
1450

1451
	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1452 1453 1454 1455 1456

	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
1457
		trace_shrink_flags(file, sc->reclaim_mode));
1458
	return nr_reclaimed;
L
Linus Torvalds 已提交
1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477
}

/*
 * 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.
 */
1478

1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496
static void move_active_pages_to_lru(struct zone *zone,
				     struct list_head *list,
				     enum lru_list lru)
{
	unsigned long pgmoved = 0;
	struct pagevec pvec;
	struct page *page;

	pagevec_init(&pvec, 1);

	while (!list_empty(list)) {
		page = lru_to_page(list);

		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);

		list_move(&page->lru, &zone->lru[lru].list);
		mem_cgroup_add_lru_list(page, lru);
1497
		pgmoved += hpage_nr_pages(page);
1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510

		if (!pagevec_add(&pvec, page) || list_empty(list)) {
			spin_unlock_irq(&zone->lru_lock);
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	if (!is_active_lru(lru))
		__count_vm_events(PGDEACTIVATE, pgmoved);
}
1511

A
Andrew Morton 已提交
1512
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1513
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1514
{
1515
	unsigned long nr_taken;
1516
	unsigned long pgscanned;
1517
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1518
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1519
	LIST_HEAD(l_active);
1520
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1521
	struct page *page;
1522
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1523
	unsigned long nr_rotated = 0;
L
Linus Torvalds 已提交
1524 1525 1526

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1527
	if (scanning_global_lru(sc)) {
1528 1529 1530 1531
		nr_taken = isolate_pages_global(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						1, file);
1532
		zone->pages_scanned += pgscanned;
1533 1534 1535 1536 1537 1538 1539 1540 1541
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						sc->mem_cgroup, 1, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
1542
	}
1543

1544
	reclaim_stat->recent_scanned[file] += nr_taken;
1545

1546
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1547
	if (file)
1548
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1549
	else
1550
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1551
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1552 1553 1554 1555 1556 1557
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1558

L
Lee Schermerhorn 已提交
1559 1560 1561 1562 1563
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1564
		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1565
			nr_rotated += hpage_nr_pages(page);
1566 1567 1568 1569 1570 1571 1572 1573 1574
			/*
			 * Identify referenced, file-backed active pages and
			 * give them one more trip around the active list. So
			 * that executable code get better chances to stay in
			 * memory under moderate memory pressure.  Anon pages
			 * are not likely to be evicted by use-once streaming
			 * IO, plus JVM can create lots of anon VM_EXEC pages,
			 * so we ignore them here.
			 */
1575
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1576 1577 1578 1579
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1580

1581
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1582 1583 1584
		list_add(&page->lru, &l_inactive);
	}

1585
	/*
1586
	 * Move pages back to the lru list.
1587
	 */
1588
	spin_lock_irq(&zone->lru_lock);
1589
	/*
1590 1591 1592 1593
	 * Count referenced pages from currently used mappings as rotated,
	 * even though only some of them are actually re-activated.  This
	 * helps balance scan pressure between file and anonymous pages in
	 * get_scan_ratio.
1594
	 */
1595
	reclaim_stat->recent_rotated[file] += nr_rotated;
1596

1597 1598 1599 1600
	move_active_pages_to_lru(zone, &l_active,
						LRU_ACTIVE + file * LRU_FILE);
	move_active_pages_to_lru(zone, &l_inactive,
						LRU_BASE   + file * LRU_FILE);
K
KOSAKI Motohiro 已提交
1601
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1602
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1603 1604
}

1605
#ifdef CONFIG_SWAP
1606
static int inactive_anon_is_low_global(struct zone *zone)
1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618
{
	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;
}

1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630
/**
 * 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;

1631 1632 1633 1634 1635 1636 1637
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1638
	if (scanning_global_lru(sc))
1639 1640
		low = inactive_anon_is_low_global(zone);
	else
1641
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1642 1643
	return low;
}
1644 1645 1646 1647 1648 1649 1650
#else
static inline int inactive_anon_is_low(struct zone *zone,
					struct scan_control *sc)
{
	return 0;
}
#endif
1651

1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687
static int inactive_file_is_low_global(struct zone *zone)
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_FILE);
	inactive = zone_page_state(zone, NR_INACTIVE_FILE);

	return (active > inactive);
}

/**
 * inactive_file_is_low - check if file pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * When the system is doing streaming IO, memory pressure here
 * ensures that active file pages get deactivated, until more
 * than half of the file pages are on the inactive list.
 *
 * Once we get to that situation, protect the system's working
 * set from being evicted by disabling active file page aging.
 *
 * This uses a different ratio than the anonymous pages, because
 * the page cache uses a use-once replacement algorithm.
 */
static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

	if (scanning_global_lru(sc))
		low = inactive_file_is_low_global(zone);
	else
		low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
	return low;
}

1688 1689 1690 1691 1692 1693 1694 1695 1696
static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
				int file)
{
	if (file)
		return inactive_file_is_low(zone, sc);
	else
		return inactive_anon_is_low(zone, sc);
}

1697
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1698 1699
	struct zone *zone, struct scan_control *sc, int priority)
{
1700 1701
	int file = is_file_lru(lru);

1702 1703 1704
	if (is_active_lru(lru)) {
		if (inactive_list_is_low(zone, sc, file))
		    shrink_active_list(nr_to_scan, zone, sc, priority, file);
1705 1706 1707
		return 0;
	}

R
Rik van Riel 已提交
1708
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1709 1710
}

1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730
/*
 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
 * until we collected @swap_cluster_max pages to scan.
 */
static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
				       unsigned long *nr_saved_scan)
{
	unsigned long nr;

	*nr_saved_scan += nr_to_scan;
	nr = *nr_saved_scan;

	if (nr >= SWAP_CLUSTER_MAX)
		*nr_saved_scan = 0;
	else
		nr = 0;

	return nr;
}

1731 1732 1733 1734 1735 1736
/*
 * 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.
 *
1737
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1738
 */
1739 1740
static void get_scan_count(struct zone *zone, struct scan_control *sc,
					unsigned long *nr, int priority)
1741 1742 1743 1744
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1745
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757
	u64 fraction[2], denominator;
	enum lru_list l;
	int noswap = 0;

	/* If we have no swap space, do not bother scanning anon pages. */
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
		noswap = 1;
		fraction[0] = 0;
		fraction[1] = 1;
		denominator = 1;
		goto out;
	}
1758

1759 1760 1761 1762
	anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1763

1764
	if (scanning_global_lru(sc)) {
1765 1766 1767
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1768
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1769 1770 1771 1772
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1773
		}
1774 1775
	}

1776 1777 1778 1779 1780 1781 1782
	/*
	 * 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;

1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793
	/*
	 * 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]
	 */
1794
	spin_lock_irq(&zone->lru_lock);
1795 1796 1797
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1798 1799
	}

1800 1801 1802
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1803 1804 1805
	}

	/*
1806 1807 1808
	 * 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.
1809
	 */
1810 1811
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1812

1813 1814
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1815
	spin_unlock_irq(&zone->lru_lock);
1816

1817 1818 1819 1820 1821 1822 1823
	fraction[0] = ap;
	fraction[1] = fp;
	denominator = ap + fp + 1;
out:
	for_each_evictable_lru(l) {
		int file = is_file_lru(l);
		unsigned long scan;
1824

1825 1826 1827 1828 1829 1830 1831 1832
		scan = zone_nr_lru_pages(zone, sc, l);
		if (priority || noswap) {
			scan >>= priority;
			scan = div64_u64(scan * fraction[file], denominator);
		}
		nr[l] = nr_scan_try_batch(scan,
					  &reclaim_stat->nr_saved_scan[l]);
	}
1833
}
1834

1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850
/*
 * Reclaim/compaction depends on a number of pages being freed. To avoid
 * disruption to the system, a small number of order-0 pages continue to be
 * rotated and reclaimed in the normal fashion. However, by the time we get
 * back to the allocator and call try_to_compact_zone(), we ensure that
 * there are enough free pages for it to be likely successful
 */
static inline bool should_continue_reclaim(struct zone *zone,
					unsigned long nr_reclaimed,
					unsigned long nr_scanned,
					struct scan_control *sc)
{
	unsigned long pages_for_compaction;
	unsigned long inactive_lru_pages;

	/* If not in reclaim/compaction mode, stop */
1851
	if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1852 1853
		return false;

1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875
	/* Consider stopping depending on scan and reclaim activity */
	if (sc->gfp_mask & __GFP_REPEAT) {
		/*
		 * For __GFP_REPEAT allocations, stop reclaiming if the
		 * full LRU list has been scanned and we are still failing
		 * to reclaim pages. This full LRU scan is potentially
		 * expensive but a __GFP_REPEAT caller really wants to succeed
		 */
		if (!nr_reclaimed && !nr_scanned)
			return false;
	} else {
		/*
		 * For non-__GFP_REPEAT allocations which can presumably
		 * fail without consequence, stop if we failed to reclaim
		 * any pages from the last SWAP_CLUSTER_MAX number of
		 * pages that were scanned. This will return to the
		 * caller faster at the risk reclaim/compaction and
		 * the resulting allocation attempt fails
		 */
		if (!nr_reclaimed)
			return false;
	}
1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = (2UL << sc->order);
	inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
				zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
	if (sc->nr_reclaimed < pages_for_compaction &&
			inactive_lru_pages > pages_for_compaction)
		return true;

	/* If compaction would go ahead or the allocation would succeed, stop */
	switch (compaction_suitable(zone, sc->order)) {
	case COMPACT_PARTIAL:
	case COMPACT_CONTINUE:
		return false;
	default:
		return true;
	}
}

L
Linus Torvalds 已提交
1898 1899 1900
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1901
static void shrink_zone(int priority, struct zone *zone,
1902
				struct scan_control *sc)
L
Linus Torvalds 已提交
1903
{
1904
	unsigned long nr[NR_LRU_LISTS];
1905
	unsigned long nr_to_scan;
1906
	enum lru_list l;
1907
	unsigned long nr_reclaimed, nr_scanned;
1908
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1909

1910 1911
restart:
	nr_reclaimed = 0;
1912
	nr_scanned = sc->nr_scanned;
1913
	get_scan_count(zone, sc, nr, priority);
L
Linus Torvalds 已提交
1914

1915 1916
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1917
		for_each_evictable_lru(l) {
1918
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
1919 1920
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
1921
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1922

1923 1924
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1925
			}
L
Linus Torvalds 已提交
1926
		}
1927 1928 1929 1930 1931 1932 1933 1934
		/*
		 * 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.
		 */
1935
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1936
			break;
L
Linus Torvalds 已提交
1937
	}
1938
	sc->nr_reclaimed += nr_reclaimed;
1939

1940 1941 1942 1943
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1944
	if (inactive_anon_is_low(zone, sc))
1945 1946
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1947 1948 1949 1950 1951
	/* reclaim/compaction might need reclaim to continue */
	if (should_continue_reclaim(zone, nr_reclaimed,
					sc->nr_scanned - nr_scanned, sc))
		goto restart;

1952
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1953 1954 1955 1956 1957 1958 1959
}

/*
 * 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.
 *
1960 1961
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
1962 1963
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
1964 1965 1966
 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
 *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
 *    zone defense algorithm.
L
Linus Torvalds 已提交
1967 1968 1969 1970
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1971
static void shrink_zones(int priority, struct zonelist *zonelist,
1972
					struct scan_control *sc)
L
Linus Torvalds 已提交
1973
{
1974
	struct zoneref *z;
1975
	struct zone *zone;
1976

1977 1978
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
1979
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1980
			continue;
1981 1982 1983 1984
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1985
		if (scanning_global_lru(sc)) {
1986 1987
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
1988
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1989 1990
				continue;	/* Let kswapd poll it */
		}
1991

1992
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1993
	}
1994 1995 1996 1997 1998 1999 2000
}

static bool zone_reclaimable(struct zone *zone)
{
	return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
}

2001
/* All zones in zonelist are unreclaimable? */
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
static bool all_unreclaimable(struct zonelist *zonelist,
		struct scan_control *sc)
{
	struct zoneref *z;
	struct zone *zone;

	for_each_zone_zonelist_nodemask(zone, z, zonelist,
			gfp_zone(sc->gfp_mask), sc->nodemask) {
		if (!populated_zone(zone))
			continue;
		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
			continue;
2014 2015
		if (!zone->all_unreclaimable)
			return false;
2016 2017
	}

2018
	return true;
L
Linus Torvalds 已提交
2019
}
2020

L
Linus Torvalds 已提交
2021 2022 2023 2024 2025 2026 2027 2028
/*
 * 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
2029 2030 2031 2032
 * caller can't do much about.  We kick the writeback threads 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.
2033 2034 2035
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2036
 */
2037
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2038
					struct scan_control *sc)
L
Linus Torvalds 已提交
2039 2040
{
	int priority;
2041
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2042
	struct reclaim_state *reclaim_state = current->reclaim_state;
2043
	struct zoneref *z;
2044
	struct zone *zone;
2045
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
2046

2047
	get_mems_allowed();
2048 2049
	delayacct_freepages_start();

2050
	if (scanning_global_lru(sc))
2051
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2052 2053

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2054
		sc->nr_scanned = 0;
2055 2056
		if (!priority)
			disable_swap_token();
2057
		shrink_zones(priority, zonelist, sc);
2058 2059 2060 2061
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
2062
		if (scanning_global_lru(sc)) {
2063
			unsigned long lru_pages = 0;
2064 2065
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2066 2067 2068 2069 2070 2071
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

2072
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
2073
			if (reclaim_state) {
2074
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2075 2076
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2077
		}
2078
		total_scanned += sc->nr_scanned;
2079
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2080 2081 2082 2083 2084 2085 2086 2087 2088
			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.
		 */
2089 2090
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2091
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2092
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2093 2094 2095
		}

		/* Take a nap, wait for some writeback to complete */
2096
		if (!sc->hibernation_mode && sc->nr_scanned &&
2097 2098 2099 2100
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2101 2102
						&cpuset_current_mems_allowed,
						&preferred_zone);
2103 2104
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2105
	}
2106

L
Linus Torvalds 已提交
2107
out:
2108
	delayacct_freepages_end();
2109
	put_mems_allowed();
2110

2111 2112 2113
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

2114 2115 2116 2117 2118 2119 2120 2121
	/*
	 * As hibernation is going on, kswapd is freezed so that it can't mark
	 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
	 * check.
	 */
	if (oom_killer_disabled)
		return 0;

2122
	/* top priority shrink_zones still had more to do? don't OOM, then */
2123
	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2124 2125 2126
		return 1;

	return 0;
L
Linus Torvalds 已提交
2127 2128
}

2129
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2130
				gfp_t gfp_mask, nodemask_t *nodemask)
2131
{
2132
	unsigned long nr_reclaimed;
2133 2134 2135
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2136
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2137
		.may_unmap = 1,
2138
		.may_swap = 1,
2139 2140 2141
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
2142
		.nodemask = nodemask,
2143 2144
	};

2145 2146 2147 2148 2149 2150 2151 2152 2153
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2154 2155
}

2156
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2157

2158 2159 2160
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						unsigned int swappiness,
2161
						struct zone *zone)
2162 2163
{
	struct scan_control sc = {
2164
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2165 2166 2167 2168 2169 2170 2171 2172 2173
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.swappiness = swappiness,
		.order = 0,
		.mem_cgroup = mem,
	};
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2174 2175 2176 2177 2178

	trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
						      sc.may_writepage,
						      sc.gfp_mask);

2179 2180 2181 2182 2183 2184 2185 2186
	/*
	 * NOTE: Although we can get the priority field, using it
	 * here is not a good idea, since it limits the pages we can scan.
	 * if we don't reclaim here, the shrink_zone from balance_pgdat
	 * will pick up pages from other mem cgroup's as well. We hack
	 * the priority and make it zero.
	 */
	shrink_zone(0, zone, &sc);
2187 2188 2189

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2190 2191 2192
	return sc.nr_reclaimed;
}

2193
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
2194 2195 2196
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
2197
{
2198
	struct zonelist *zonelist;
2199
	unsigned long nr_reclaimed;
2200 2201
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2202
		.may_unmap = 1,
2203
		.may_swap = !noswap,
2204
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
2205
		.swappiness = swappiness,
2206 2207
		.order = 0,
		.mem_cgroup = mem_cont,
2208
		.nodemask = NULL, /* we don't care the placement */
2209 2210
	};

2211 2212 2213
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2214 2215 2216 2217 2218 2219 2220 2221 2222 2223

	trace_mm_vmscan_memcg_reclaim_begin(0,
					    sc.may_writepage,
					    sc.gfp_mask);

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2224 2225 2226
}
#endif

2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237
/*
 * pgdat_balanced is used when checking if a node is balanced for high-order
 * allocations. Only zones that meet watermarks and are in a zone allowed
 * by the callers classzone_idx are added to balanced_pages. The total of
 * balanced pages must be at least 25% of the zones allowed by classzone_idx
 * for the node to be considered balanced. Forcing all zones to be balanced
 * for high orders can cause excessive reclaim when there are imbalanced zones.
 * The choice of 25% is due to
 *   o a 16M DMA zone that is balanced will not balance a zone on any
 *     reasonable sized machine
 *   o On all other machines, the top zone must be at least a reasonable
L
Lucas De Marchi 已提交
2238
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254
 *     would need to be at least 256M for it to be balance a whole node.
 *     Similarly, on x86-64 the Normal zone would need to be at least 1G
 *     to balance a node on its own. These seemed like reasonable ratios.
 */
static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
						int classzone_idx)
{
	unsigned long present_pages = 0;
	int i;

	for (i = 0; i <= classzone_idx; i++)
		present_pages += pgdat->node_zones[i].present_pages;

	return balanced_pages > (present_pages >> 2);
}

2255
/* is kswapd sleeping prematurely? */
2256 2257
static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
					int classzone_idx)
2258
{
2259
	int i;
2260 2261
	unsigned long balanced = 0;
	bool all_zones_ok = true;
2262 2263 2264

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2265
		return true;
2266

2267
	/* Check the watermark levels */
2268 2269 2270 2271 2272 2273
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2274 2275 2276 2277 2278 2279 2280 2281
		/*
		 * balance_pgdat() skips over all_unreclaimable after
		 * DEF_PRIORITY. Effectively, it considers them balanced so
		 * they must be considered balanced here as well if kswapd
		 * is to sleep
		 */
		if (zone->all_unreclaimable) {
			balanced += zone->present_pages;
2282
			continue;
2283
		}
2284

2285
		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2286
							classzone_idx, 0))
2287 2288 2289
			all_zones_ok = false;
		else
			balanced += zone->present_pages;
2290
	}
2291

2292 2293 2294 2295 2296 2297
	/*
	 * For high-order requests, the balanced zones must contain at least
	 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
	 * must be balanced
	 */
	if (order)
2298
		return !pgdat_balanced(pgdat, balanced, classzone_idx);
2299 2300
	else
		return !all_zones_ok;
2301 2302
}

L
Linus Torvalds 已提交
2303 2304
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2305
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2306
 *
2307
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2308 2309 2310 2311 2312 2313 2314 2315 2316 2317
 *
 * 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
2318 2319 2320 2321 2322
 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
 * found to have free_pages <= high_wmark_pages(zone), 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.
L
Linus Torvalds 已提交
2323
 */
2324
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2325
							int *classzone_idx)
L
Linus Torvalds 已提交
2326 2327
{
	int all_zones_ok;
2328
	unsigned long balanced;
L
Linus Torvalds 已提交
2329 2330
	int priority;
	int i;
2331
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2332
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2333
	struct reclaim_state *reclaim_state = current->reclaim_state;
2334 2335
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2336
		.may_unmap = 1,
2337
		.may_swap = 1,
2338 2339 2340 2341 2342
		/*
		 * kswapd doesn't want to be bailed out while reclaim. because
		 * we want to put equal scanning pressure on each zone.
		 */
		.nr_to_reclaim = ULONG_MAX,
2343
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
2344
		.order = order,
2345
		.mem_cgroup = NULL,
2346
	};
L
Linus Torvalds 已提交
2347 2348
loop_again:
	total_scanned = 0;
2349
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2350
	sc.may_writepage = !laptop_mode;
2351
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2352 2353 2354

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		unsigned long lru_pages = 0;
2355
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2356

2357 2358 2359 2360
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
2361
		all_zones_ok = 1;
2362
		balanced = 0;
L
Linus Torvalds 已提交
2363

2364 2365 2366 2367 2368 2369
		/*
		 * 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
2370

2371 2372
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2373

2374
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2375
				continue;
L
Linus Torvalds 已提交
2376

2377 2378 2379 2380
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2381
			if (inactive_anon_is_low(zone, &sc))
2382 2383 2384
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

2385
			if (!zone_watermark_ok_safe(zone, order,
2386
					high_wmark_pages(zone), 0, 0)) {
2387
				end_zone = i;
2388
				*classzone_idx = i;
A
Andrew Morton 已提交
2389
				break;
L
Linus Torvalds 已提交
2390 2391
			}
		}
A
Andrew Morton 已提交
2392 2393 2394
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2395 2396 2397
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2398
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411
		}

		/*
		 * 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;
2412
			int nr_slab;
2413
			unsigned long balance_gap;
L
Linus Torvalds 已提交
2414

2415
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2416 2417
				continue;

2418
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2419 2420 2421
				continue;

			sc.nr_scanned = 0;
2422 2423 2424 2425 2426

			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 * For now we ignore the return value
			 */
2427 2428
			mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);

2429
			/*
2430 2431 2432 2433 2434 2435
			 * We put equal pressure on every zone, unless
			 * one zone has way too many pages free
			 * already. The "too many pages" is defined
			 * as the high wmark plus a "gap" where the
			 * gap is either the low watermark or 1%
			 * of the zone, whichever is smaller.
2436
			 */
2437 2438 2439 2440
			balance_gap = min(low_wmark_pages(zone),
				(zone->present_pages +
					KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
				KSWAPD_ZONE_BALANCE_GAP_RATIO);
2441
			if (!zone_watermark_ok_safe(zone, order,
2442 2443
					high_wmark_pages(zone) + balance_gap,
					end_zone, 0))
2444
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
2445
			reclaim_state->reclaimed_slab = 0;
2446 2447
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
2448
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
2449
			total_scanned += sc.nr_scanned;
2450

2451
			if (zone->all_unreclaimable)
L
Linus Torvalds 已提交
2452
				continue;
2453
			if (nr_slab == 0 &&
2454
			    !zone_reclaimable(zone))
2455
				zone->all_unreclaimable = 1;
L
Linus Torvalds 已提交
2456 2457 2458 2459 2460 2461
			/*
			 * 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 &&
2462
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2463
				sc.may_writepage = 1;
2464

2465
			if (!zone_watermark_ok_safe(zone, order,
2466 2467 2468 2469 2470 2471 2472
					high_wmark_pages(zone), end_zone, 0)) {
				all_zones_ok = 0;
				/*
				 * We are still under min water mark.  This
				 * means that we have a GFP_ATOMIC allocation
				 * failure risk. Hurry up!
				 */
2473
				if (!zone_watermark_ok_safe(zone, order,
2474 2475
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2476 2477 2478 2479 2480 2481 2482 2483 2484
			} else {
				/*
				 * If a zone reaches its high watermark,
				 * consider it to be no longer congested. It's
				 * possible there are dirty pages backed by
				 * congested BDIs but as pressure is relieved,
				 * spectulatively avoid congestion waits
				 */
				zone_clear_flag(zone, ZONE_CONGESTED);
2485
				if (i <= *classzone_idx)
2486
					balanced += zone->present_pages;
2487
			}
2488

L
Linus Torvalds 已提交
2489
		}
2490
		if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
L
Linus Torvalds 已提交
2491 2492 2493 2494 2495
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2496 2497 2498 2499 2500 2501
		if (total_scanned && (priority < DEF_PRIORITY - 2)) {
			if (has_under_min_watermark_zone)
				count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
			else
				congestion_wait(BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2502 2503 2504 2505 2506 2507 2508

		/*
		 * 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.
		 */
2509
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2510 2511 2512
			break;
	}
out:
2513 2514 2515

	/*
	 * order-0: All zones must meet high watermark for a balanced node
2516 2517
	 * high-order: Balanced zones must make up at least 25% of the node
	 *             for the node to be balanced
2518
	 */
2519
	if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
L
Linus Torvalds 已提交
2520
		cond_resched();
2521 2522 2523

		try_to_freeze();

2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540
		/*
		 * 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
2541 2542 2543
		goto loop_again;
	}

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
	/*
	 * If kswapd was reclaiming at a higher order, it has the option of
	 * sleeping without all zones being balanced. Before it does, it must
	 * ensure that the watermarks for order-0 on *all* zones are met and
	 * that the congestion flags are cleared. The congestion flag must
	 * be cleared as kswapd is the only mechanism that clears the flag
	 * and it is potentially going to sleep here.
	 */
	if (order) {
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

			if (!populated_zone(zone))
				continue;

			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
				continue;

			/* Confirm the zone is balanced for order-0 */
			if (!zone_watermark_ok(zone, 0,
					high_wmark_pages(zone), 0, 0)) {
				order = sc.order = 0;
				goto loop_again;
			}

			/* If balanced, clear the congested flag */
			zone_clear_flag(zone, ZONE_CONGESTED);
		}
	}

2574 2575 2576 2577 2578 2579
	/*
	 * Return the order we were reclaiming at so sleeping_prematurely()
	 * makes a decision on the order we were last reclaiming at. However,
	 * if another caller entered the allocator slow path while kswapd
	 * was awake, order will remain at the higher level
	 */
2580
	*classzone_idx = end_zone;
2581
	return order;
L
Linus Torvalds 已提交
2582 2583
}

2584
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594
{
	long remaining = 0;
	DEFINE_WAIT(wait);

	if (freezing(current) || kthread_should_stop())
		return;

	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

	/* Try to sleep for a short interval */
2595
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2596 2597 2598 2599 2600 2601 2602 2603 2604
		remaining = schedule_timeout(HZ/10);
		finish_wait(&pgdat->kswapd_wait, &wait);
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
	}

	/*
	 * After a short sleep, check if it was a premature sleep. If not, then
	 * go fully to sleep until explicitly woken up.
	 */
2605
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627
		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);

		/*
		 * vmstat counters are not perfectly accurate and the estimated
		 * value for counters such as NR_FREE_PAGES can deviate from the
		 * true value by nr_online_cpus * threshold. To avoid the zone
		 * watermarks being breached while under pressure, we reduce the
		 * per-cpu vmstat threshold while kswapd is awake and restore
		 * them before going back to sleep.
		 */
		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
		schedule();
		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
	} else {
		if (remaining)
			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
		else
			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
	}
	finish_wait(&pgdat->kswapd_wait, &wait);
}

L
Linus Torvalds 已提交
2628 2629
/*
 * The background pageout daemon, started as a kernel thread
2630
 * from the init process.
L
Linus Torvalds 已提交
2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643
 *
 * 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;
2644
	int classzone_idx;
L
Linus Torvalds 已提交
2645 2646
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
2647

L
Linus Torvalds 已提交
2648 2649 2650
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
2651
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2652

2653 2654
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2655
	if (!cpumask_empty(cpumask))
2656
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670
	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).
	 */
2671
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2672
	set_freezable();
L
Linus Torvalds 已提交
2673 2674

	order = 0;
2675
	classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2676 2677
	for ( ; ; ) {
		unsigned long new_order;
2678
		int new_classzone_idx;
2679
		int ret;
2680

L
Linus Torvalds 已提交
2681
		new_order = pgdat->kswapd_max_order;
2682
		new_classzone_idx = pgdat->classzone_idx;
L
Linus Torvalds 已提交
2683
		pgdat->kswapd_max_order = 0;
2684 2685
		pgdat->classzone_idx = MAX_NR_ZONES - 1;
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
2686 2687
			/*
			 * Don't sleep if someone wants a larger 'order'
2688
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
2689 2690
			 */
			order = new_order;
2691
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
2692
		} else {
2693
			kswapd_try_to_sleep(pgdat, order, classzone_idx);
L
Linus Torvalds 已提交
2694
			order = pgdat->kswapd_max_order;
2695
			classzone_idx = pgdat->classzone_idx;
2696 2697
			pgdat->kswapd_max_order = 0;
			pgdat->classzone_idx = MAX_NR_ZONES - 1;
L
Linus Torvalds 已提交
2698 2699
		}

2700 2701 2702 2703 2704 2705 2706 2707
		ret = try_to_freeze();
		if (kthread_should_stop())
			break;

		/*
		 * We can speed up thawing tasks if we don't call balance_pgdat
		 * after returning from the refrigerator
		 */
2708 2709
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2710
			order = balance_pgdat(pgdat, order, &classzone_idx);
2711
		}
L
Linus Torvalds 已提交
2712 2713 2714 2715 2716 2717 2718
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
2719
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
2720 2721 2722
{
	pg_data_t *pgdat;

2723
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2724 2725
		return;

2726
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2727
		return;
2728
	pgdat = zone->zone_pgdat;
2729
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
2730
		pgdat->kswapd_max_order = order;
2731 2732
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
2733
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2734
		return;
2735 2736 2737 2738
	if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
		return;

	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2739
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2740 2741
}

2742 2743 2744 2745 2746 2747 2748 2749
/*
 * The reclaimable count would be mostly accurate.
 * The less reclaimable pages may be
 * - mlocked pages, which will be moved to unevictable list when encountered
 * - mapped pages, which may require several travels to be reclaimed
 * - dirty pages, which is not "instantly" reclaimable
 */
unsigned long global_reclaimable_pages(void)
2750
{
2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774
	int nr;

	nr = global_page_state(NR_ACTIVE_FILE) +
	     global_page_state(NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += global_page_state(NR_ACTIVE_ANON) +
		      global_page_state(NR_INACTIVE_ANON);

	return nr;
}

unsigned long zone_reclaimable_pages(struct zone *zone)
{
	int nr;

	nr = zone_page_state(zone, NR_ACTIVE_FILE) +
	     zone_page_state(zone, NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += zone_page_state(zone, NR_ACTIVE_ANON) +
		      zone_page_state(zone, NR_INACTIVE_ANON);

	return nr;
2775 2776
}

2777
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2778
/*
2779
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2780 2781 2782 2783 2784
 * 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
2785
 */
2786
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
2787
{
2788 2789
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
2790 2791 2792
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
2793
		.may_writepage = 1,
2794 2795 2796 2797
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.swappiness = vm_swappiness,
		.order = 0,
L
Linus Torvalds 已提交
2798
	};
2799 2800 2801
	struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
2802

2803 2804 2805 2806
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2807

2808
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2809

2810 2811 2812
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
2813

2814
	return nr_reclaimed;
L
Linus Torvalds 已提交
2815
}
2816
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
2817 2818 2819 2820 2821

/* 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. */
2822
static int __devinit cpu_callback(struct notifier_block *nfb,
2823
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2824
{
2825
	int nid;
L
Linus Torvalds 已提交
2826

2827
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2828
		for_each_node_state(nid, N_HIGH_MEMORY) {
2829
			pg_data_t *pgdat = NODE_DATA(nid);
2830 2831 2832
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2833

2834
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2835
				/* One of our CPUs online: restore mask */
2836
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2837 2838 2839 2840 2841
		}
	}
	return NOTIFY_OK;
}

2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863
/*
 * 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;
}

2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874
/*
 * Called by memory hotplug when all memory in a node is offlined.
 */
void kswapd_stop(int nid)
{
	struct task_struct *kswapd = NODE_DATA(nid)->kswapd;

	if (kswapd)
		kthread_stop(kswapd);
}

L
Linus Torvalds 已提交
2875 2876
static int __init kswapd_init(void)
{
2877
	int nid;
2878

L
Linus Torvalds 已提交
2879
	swap_setup();
2880
	for_each_node_state(nid, N_HIGH_MEMORY)
2881
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2882 2883 2884 2885 2886
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896

#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;

2897
#define RECLAIM_OFF 0
2898
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2899 2900 2901
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2902 2903 2904 2905 2906 2907 2908
/*
 * 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

2909 2910 2911 2912 2913 2914
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2915 2916 2917 2918 2919 2920
/*
 * 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;

2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962
static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
{
	unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
	unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
		zone_page_state(zone, NR_ACTIVE_FILE);

	/*
	 * It's possible for there to be more file mapped pages than
	 * accounted for by the pages on the file LRU lists because
	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
	 */
	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
}

/* Work out how many page cache pages we can reclaim in this reclaim_mode */
static long zone_pagecache_reclaimable(struct zone *zone)
{
	long nr_pagecache_reclaimable;
	long delta = 0;

	/*
	 * If RECLAIM_SWAP is set, then all file pages are considered
	 * potentially reclaimable. Otherwise, we have to worry about
	 * pages like swapcache and zone_unmapped_file_pages() provides
	 * a better estimate
	 */
	if (zone_reclaim_mode & RECLAIM_SWAP)
		nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
	else
		nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);

	/* If we can't clean pages, remove dirty pages from consideration */
	if (!(zone_reclaim_mode & RECLAIM_WRITE))
		delta += zone_page_state(zone, NR_FILE_DIRTY);

	/* Watch for any possible underflows due to delta */
	if (unlikely(delta > nr_pagecache_reclaimable))
		delta = nr_pagecache_reclaimable;

	return nr_pagecache_reclaimable - delta;
}

2963 2964 2965
/*
 * Try to free up some pages from this zone through reclaim.
 */
2966
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2967
{
2968
	/* Minimum pages needed in order to stay on node */
2969
	const unsigned long nr_pages = 1 << order;
2970 2971
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2972
	int priority;
2973 2974
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2975
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2976
		.may_swap = 1,
2977 2978
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
2979
		.gfp_mask = gfp_mask,
2980
		.swappiness = vm_swappiness,
2981
		.order = order,
2982
	};
2983
	unsigned long nr_slab_pages0, nr_slab_pages1;
2984 2985

	cond_resched();
2986 2987 2988 2989 2990 2991
	/*
	 * 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;
2992
	lockdep_set_current_reclaim_state(gfp_mask);
2993 2994
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2995

2996
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2997 2998 2999 3000 3001 3002
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
3003
			shrink_zone(priority, zone, &sc);
3004
			priority--;
3005
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3006
	}
3007

3008 3009
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
3010
		/*
3011
		 * shrink_slab() does not currently allow us to determine how
3012 3013 3014 3015
		 * 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.
3016
		 *
3017 3018
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
3019
		 */
3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
			if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages))
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3033 3034 3035 3036 3037

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3038 3039 3040
		nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
		if (nr_slab_pages1 < nr_slab_pages0)
			sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3041 3042
	}

3043
	p->reclaim_state = NULL;
3044
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3045
	lockdep_clear_current_reclaim_state();
3046
	return sc.nr_reclaimed >= nr_pages;
3047
}
3048 3049 3050 3051

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3052
	int ret;
3053 3054

	/*
3055 3056
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3057
	 *
3058 3059 3060 3061 3062
	 * 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.
3063
	 */
3064 3065
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3066
		return ZONE_RECLAIM_FULL;
3067

3068
	if (zone->all_unreclaimable)
3069
		return ZONE_RECLAIM_FULL;
3070

3071
	/*
3072
	 * Do not scan if the allocation should not be delayed.
3073
	 */
3074
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3075
		return ZONE_RECLAIM_NOSCAN;
3076 3077 3078 3079 3080 3081 3082

	/*
	 * 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.
	 */
3083
	node_id = zone_to_nid(zone);
3084
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3085
		return ZONE_RECLAIM_NOSCAN;
3086 3087

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3088 3089
		return ZONE_RECLAIM_NOSCAN;

3090 3091 3092
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3093 3094 3095
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3096
	return ret;
3097
}
3098
#endif
L
Lee Schermerhorn 已提交
3099 3100 3101 3102 3103 3104 3105

/*
 * 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
3106 3107
 * 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
3108 3109
 *
 * Reasons page might not be evictable:
3110
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3111
 * (2) page is part of an mlocked VMA
3112
 *
L
Lee Schermerhorn 已提交
3113 3114 3115 3116
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

3117 3118 3119
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
3120 3121
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
3122 3123 3124

	return 1;
}
3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143

/**
 * 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)) {
3144
		enum lru_list l = page_lru_base_type(page);
3145

3146 3147
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
3148
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3149 3150 3151 3152 3153 3154 3155 3156
		__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
3157
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216
		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);
	}

}
3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228

/**
 * 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 */
3229
static void scan_zone_unevictable_pages(struct zone *zone)
3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270
{
	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.
 */
3271
static void scan_all_zones_unevictable_pages(void)
3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286
{
	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,
3287
			   void __user *buffer,
3288 3289
			   size_t *length, loff_t *ppos)
{
3290
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3291 3292 3293 3294 3295 3296 3297 3298

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

	scan_unevictable_pages = 0;
	return 0;
}

3299
#ifdef CONFIG_NUMA
3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345
/*
 * 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);
}
3346
#endif