vmscan.c 40.8 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69
/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/file.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>	/* for try_to_release_page(),
					buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/notifier.h>
#include <linux/rwsem.h>

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

#include <linux/swapops.h>

/* 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;

struct scan_control {
	/* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
	unsigned long nr_to_scan;

	/* Incremented by the number of inactive pages that were scanned */
	unsigned long nr_scanned;

	/* Incremented by the number of pages reclaimed */
	unsigned long nr_reclaimed;

	unsigned long nr_mapped;	/* From page_state */

	/* Ask shrink_caches, or shrink_zone to scan at this priority */
	unsigned int priority;

	/* This context's GFP mask */
A
Al Viro 已提交
70
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179

	int may_writepage;

	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
	 * In this context, it doesn't matter that we scan the
	 * whole list at once. */
	int swap_cluster_max;
};

/*
 * The list of shrinker callbacks used by to apply pressure to
 * ageable caches.
 */
struct shrinker {
	shrinker_t		shrinker;
	struct list_head	list;
	int			seeks;	/* seeks to recreate an obj */
	long			nr;	/* objs pending delete */
};

#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;
static long total_memory;

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

/*
 * Add a shrinker callback to be called from the vm
 */
struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
{
        struct shrinker *shrinker;

        shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
        if (shrinker) {
	        shrinker->shrinker = theshrinker;
	        shrinker->seeks = seeks;
	        shrinker->nr = 0;
	        down_write(&shrinker_rwsem);
	        list_add_tail(&shrinker->list, &shrinker_list);
	        up_write(&shrinker_rwsem);
	}
	return shrinker;
}
EXPORT_SYMBOL(set_shrinker);

/*
 * Remove one
 */
void remove_shrinker(struct shrinker *shrinker)
{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
	kfree(shrinker);
}
EXPORT_SYMBOL(remove_shrinker);

#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.
 *
 * If the vm encounted mapped pages on the LRU it increase the pressure on
 * 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.
180 181
 *
 * Returns the number of slab objects which we shrunk.
L
Linus Torvalds 已提交
182
 */
A
Andrew Morton 已提交
183
int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages)
L
Linus Torvalds 已提交
184 185
{
	struct shrinker *shrinker;
186
	int ret = 0;
L
Linus Torvalds 已提交
187 188 189 190 191

	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

	if (!down_read_trylock(&shrinker_rwsem))
192
		return 1;	/* Assume we'll be able to shrink next time */
L
Linus Torvalds 已提交
193 194 195 196

	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
197
		unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
L
Linus Torvalds 已提交
198 199

		delta = (4 * scanned) / shrinker->seeks;
200
		delta *= max_pass;
L
Linus Torvalds 已提交
201 202
		do_div(delta, lru_pages + 1);
		shrinker->nr += delta;
203 204 205 206 207 208 209 210 211 212 213 214 215
		if (shrinker->nr < 0) {
			printk(KERN_ERR "%s: nr=%ld\n",
					__FUNCTION__, shrinker->nr);
			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
216 217 218 219 220 221 222

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

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
223
			int nr_before;
L
Linus Torvalds 已提交
224

225
			nr_before = (*shrinker->shrinker)(0, gfp_mask);
L
Linus Torvalds 已提交
226 227 228
			shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
			if (shrink_ret == -1)
				break;
229 230
			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
L
Linus Torvalds 已提交
231 232 233 234 235 236 237 238 239
			mod_page_state(slabs_scanned, this_scan);
			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
240
	return ret;
L
Linus Torvalds 已提交
241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
}

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

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

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

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

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

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

static int may_write_to_queue(struct backing_dev_info *bdi)
{
271
	if (current->flags & PF_SWAPWRITE)
L
Linus Torvalds 已提交
272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333
		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
	return 0;
}

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

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

	if (clear_page_dirty_for_io(page)) {
		int res;
		struct writeback_control wbc = {
			.sync_mode = WB_SYNC_NONE,
			.nr_to_write = SWAP_CLUSTER_MAX,
			.nonblocking = 1,
			.for_reclaim = 1,
		};

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
361
		if (res == AOP_WRITEPAGE_ACTIVATE) {
L
Linus Torvalds 已提交
362 363 364 365 366 367 368 369 370 371 372 373 374 375
			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}

		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412
static int remove_mapping(struct address_space *mapping, struct page *page)
{
	if (!mapping)
		return 0;		/* truncate got there first */

	write_lock_irq(&mapping->tree_lock);

	/*
	 * The non-racy check for busy page.  It is critical to check
	 * PageDirty _after_ making sure that the page is freeable and
	 * not in use by anybody. 	(pagecache + us == 2)
	 */
	if (unlikely(page_count(page) != 2))
		goto cannot_free;
	smp_rmb();
	if (unlikely(PageDirty(page)))
		goto cannot_free;

	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
		write_unlock_irq(&mapping->tree_lock);
		swap_free(swap);
		__put_page(page);	/* The pagecache ref */
		return 1;
	}

	__remove_from_page_cache(page);
	write_unlock_irq(&mapping->tree_lock);
	__put_page(page);
	return 1;

cannot_free:
	write_unlock_irq(&mapping->tree_lock);
	return 0;
}

L
Linus Torvalds 已提交
413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449
/*
 * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
 */
static int shrink_list(struct list_head *page_list, struct scan_control *sc)
{
	LIST_HEAD(ret_pages);
	struct pagevec freed_pvec;
	int pgactivate = 0;
	int reclaimed = 0;

	cond_resched();

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

		cond_resched();

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

		if (TestSetPageLocked(page))
			goto keep;

		BUG_ON(PageActive(page));

		sc->nr_scanned++;
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

		if (PageWriteback(page))
			goto keep_locked;

450
		referenced = page_referenced(page, 1);
L
Linus Torvalds 已提交
451 452 453 454 455 456 457 458 459
		/* In active use or really unfreeable?  Activate it. */
		if (referenced && page_mapping_inuse(page))
			goto activate_locked;

#ifdef CONFIG_SWAP
		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
460
		if (PageAnon(page) && !PageSwapCache(page)) {
461
			if (!add_to_swap(page, GFP_ATOMIC))
L
Linus Torvalds 已提交
462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543
				goto activate_locked;
		}
#endif /* CONFIG_SWAP */

		mapping = page_mapping(page);
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		/*
		 * The page is mapped into the page tables of one or more
		 * processes. Try to unmap it here.
		 */
		if (page_mapped(page) && mapping) {
			switch (try_to_unmap(page)) {
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
			if (referenced)
				goto keep_locked;
			if (!may_enter_fs)
				goto keep_locked;
			if (laptop_mode && !sc->may_writepage)
				goto keep_locked;

			/* Page is dirty, try to write it out here */
			switch(pageout(page, mapping)) {
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
				if (PageWriteback(page) || PageDirty(page))
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
				if (TestSetPageLocked(page))
					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
		 * will do this, as well as the blockdev mapping. 
		 * try_to_release_page() will discover that cleanness and will
		 * drop the buffers and mark the page clean - it can be freed.
		 *
		 * Rarely, pages can have buffers and no ->mapping.  These are
		 * the pages which were not successfully invalidated in
		 * truncate_complete_page().  We try to drop those buffers here
		 * and if that worked, and the page is no longer mapped into
		 * process address space (page_count == 1) it can be freed.
		 * Otherwise, leave the page on the LRU so it is swappable.
		 */
		if (PagePrivate(page)) {
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
			if (!mapping && page_count(page) == 1)
				goto free_it;
		}

544 545
		if (!remove_mapping(mapping, page))
			goto keep_locked;
L
Linus Torvalds 已提交
546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570

free_it:
		unlock_page(page);
		reclaimed++;
		if (!pagevec_add(&freed_pvec, page))
			__pagevec_release_nonlru(&freed_pvec);
		continue;

activate_locked:
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
		BUG_ON(PageLRU(page));
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
		__pagevec_release_nonlru(&freed_pvec);
	mod_page_state(pgactivate, pgactivate);
	sc->nr_reclaimed += reclaimed;
	return reclaimed;
}

571
#ifdef CONFIG_MIGRATION
572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605
static inline void move_to_lru(struct page *page)
{
	list_del(&page->lru);
	if (PageActive(page)) {
		/*
		 * lru_cache_add_active checks that
		 * the PG_active bit is off.
		 */
		ClearPageActive(page);
		lru_cache_add_active(page);
	} else {
		lru_cache_add(page);
	}
	put_page(page);
}

/*
 * Add isolated pages on the list back to the LRU
 *
 * returns the number of pages put back.
 */
int putback_lru_pages(struct list_head *l)
{
	struct page *page;
	struct page *page2;
	int count = 0;

	list_for_each_entry_safe(page, page2, l, lru) {
		move_to_lru(page);
		count++;
	}
	return count;
}

606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648
/*
 * swapout a single page
 * page is locked upon entry, unlocked on exit
 */
static int swap_page(struct page *page)
{
	struct address_space *mapping = page_mapping(page);

	if (page_mapped(page) && mapping)
		if (try_to_unmap(page) != SWAP_SUCCESS)
			goto unlock_retry;

	if (PageDirty(page)) {
		/* Page is dirty, try to write it out here */
		switch(pageout(page, mapping)) {
		case PAGE_KEEP:
		case PAGE_ACTIVATE:
			goto unlock_retry;

		case PAGE_SUCCESS:
			goto retry;

		case PAGE_CLEAN:
			; /* try to free the page below */
		}
	}

	if (PagePrivate(page)) {
		if (!try_to_release_page(page, GFP_KERNEL) ||
		    (!mapping && page_count(page) == 1))
			goto unlock_retry;
	}

	if (remove_mapping(mapping, page)) {
		/* Success */
		unlock_page(page);
		return 0;
	}

unlock_retry:
	unlock_page(page);

retry:
649
	return -EAGAIN;
650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667
}
/*
 * migrate_pages
 *
 * Two lists are passed to this function. The first list
 * contains the pages isolated from the LRU to be migrated.
 * The second list contains new pages that the pages isolated
 * can be moved to. If the second list is NULL then all
 * pages are swapped out.
 *
 * The function returns after 10 attempts or if no pages
 * are movable anymore because t has become empty
 * or no retryable pages exist anymore.
 *
 * SIMPLIFIED VERSION: This implementation of migrate_pages
 * is only swapping out pages and never touches the second
 * list. The direct migration patchset
 * extends this function to avoid the use of swap.
668 669
 *
 * Return: Number of pages not migrated when "to" ran empty.
670
 */
671 672
int migrate_pages(struct list_head *from, struct list_head *to,
		  struct list_head *moved, struct list_head *failed)
673 674 675 676 677 678 679
{
	int retry;
	int nr_failed = 0;
	int pass = 0;
	struct page *page;
	struct page *page2;
	int swapwrite = current->flags & PF_SWAPWRITE;
680
	int rc;
681 682 683 684 685 686 687

	if (!swapwrite)
		current->flags |= PF_SWAPWRITE;

redo:
	retry = 0;

688
	list_for_each_entry_safe(page, page2, from, lru) {
689 690
		cond_resched();

691 692
		rc = 0;
		if (page_count(page) == 1)
693
			/* page was freed from under us. So we are done. */
694 695
			goto next;

696 697
		/*
		 * Skip locked pages during the first two passes to give the
698 699 700
		 * functions holding the lock time to release the page. Later we
		 * use lock_page() to have a higher chance of acquiring the
		 * lock.
701
		 */
702
		rc = -EAGAIN;
703 704 705 706
		if (pass > 2)
			lock_page(page);
		else
			if (TestSetPageLocked(page))
707
				goto next;
708 709 710 711 712

		/*
		 * Only wait on writeback if we have already done a pass where
		 * we we may have triggered writeouts for lots of pages.
		 */
713
		if (pass > 0) {
714
			wait_on_page_writeback(page);
715
		} else {
716 717
			if (PageWriteback(page))
				goto unlock_page;
718
		}
719

720 721 722 723 724
		/*
		 * Anonymous pages must have swap cache references otherwise
		 * the information contained in the page maps cannot be
		 * preserved.
		 */
725
		if (PageAnon(page) && !PageSwapCache(page)) {
726
			if (!add_to_swap(page, GFP_KERNEL)) {
727 728
				rc = -ENOMEM;
				goto unlock_page;
729 730 731 732 733 734 735
			}
		}

		/*
		 * Page is properly locked and writeback is complete.
		 * Try to migrate the page.
		 */
736 737 738 739 740 741 742 743 744 745 746 747 748 749 750
		rc = swap_page(page);
		goto next;

unlock_page:
		unlock_page(page);

next:
		if (rc == -EAGAIN) {
			retry++;
		} else if (rc) {
			/* Permanent failure */
			list_move(&page->lru, failed);
			nr_failed++;
		} else {
			/* Success */
751 752
			list_move(&page->lru, moved);
		}
753 754 755 756 757 758 759 760 761
	}
	if (retry && pass++ < 10)
		goto redo;

	if (!swapwrite)
		current->flags &= ~PF_SWAPWRITE;

	return nr_failed + retry;
}
762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803

static void lru_add_drain_per_cpu(void *dummy)
{
	lru_add_drain();
}

/*
 * Isolate one page from the LRU lists and put it on the
 * indicated list. Do necessary cache draining if the
 * page is not on the LRU lists yet.
 *
 * Result:
 *  0 = page not on LRU list
 *  1 = page removed from LRU list and added to the specified list.
 * -ENOENT = page is being freed elsewhere.
 */
int isolate_lru_page(struct page *page)
{
	int rc = 0;
	struct zone *zone = page_zone(page);

redo:
	spin_lock_irq(&zone->lru_lock);
	rc = __isolate_lru_page(page);
	if (rc == 1) {
		if (PageActive(page))
			del_page_from_active_list(zone, page);
		else
			del_page_from_inactive_list(zone, page);
	}
	spin_unlock_irq(&zone->lru_lock);
	if (rc == 0) {
		/*
		 * Maybe this page is still waiting for a cpu to drain it
		 * from one of the lru lists?
		 */
		rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
		if (rc == 0 && PageLRU(page))
			goto redo;
	}
	return rc;
}
804
#endif
805

L
Linus Torvalds 已提交
806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833
/*
 * 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.
 *
 * returns how many pages were moved onto *@dst.
 */
static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
			     struct list_head *dst, int *scanned)
{
	int nr_taken = 0;
	struct page *page;
	int scan = 0;

	while (scan++ < nr_to_scan && !list_empty(src)) {
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

834 835 836 837
		switch (__isolate_lru_page(page)) {
		case 1:
			/* Succeeded to isolate page */
			list_move(&page->lru, dst);
L
Linus Torvalds 已提交
838
			nr_taken++;
839 840 841 842 843 844 845
			break;
		case -ENOENT:
			/* Not possible to isolate */
			list_move(&page->lru, src);
			break;
		default:
			BUG();
L
Linus Torvalds 已提交
846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884
		}
	}

	*scanned = scan;
	return nr_taken;
}

/*
 * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
 */
static void shrink_cache(struct zone *zone, struct scan_control *sc)
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
	int max_scan = sc->nr_to_scan;

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
	while (max_scan > 0) {
		struct page *page;
		int nr_taken;
		int nr_scan;
		int nr_freed;

		nr_taken = isolate_lru_pages(sc->swap_cluster_max,
					     &zone->inactive_list,
					     &page_list, &nr_scan);
		zone->nr_inactive -= nr_taken;
		zone->pages_scanned += nr_scan;
		spin_unlock_irq(&zone->lru_lock);

		if (nr_taken == 0)
			goto done;

		max_scan -= nr_scan;
		nr_freed = shrink_list(&page_list, sc);

N
Nick Piggin 已提交
885 886 887 888 889 890 891 892 893
		local_irq_disable();
		if (current_is_kswapd()) {
			__mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
			__mod_page_state(kswapd_steal, nr_freed);
		} else
			__mod_page_state_zone(zone, pgscan_direct, nr_scan);
		__mod_page_state_zone(zone, pgsteal, nr_freed);

		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
			page = lru_to_page(&page_list);
			if (TestSetPageLRU(page))
				BUG();
			list_del(&page->lru);
			if (PageActive(page))
				add_page_to_active_list(zone, page);
			else
				add_page_to_inactive_list(zone, page);
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
  	}
	spin_unlock_irq(&zone->lru_lock);
done:
	pagevec_release(&pvec);
}

/*
 * 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.
 */
static void
refill_inactive_zone(struct zone *zone, struct scan_control *sc)
{
	int pgmoved;
	int pgdeactivate = 0;
	int pgscanned;
	int nr_pages = sc->nr_to_scan;
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
	LIST_HEAD(l_inactive);	/* Pages to go onto the inactive_list */
	LIST_HEAD(l_active);	/* Pages to go onto the active_list */
	struct page *page;
	struct pagevec pvec;
	int reclaim_mapped = 0;
	long mapped_ratio;
	long distress;
	long swap_tendency;

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
	pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
				    &l_hold, &pgscanned);
	zone->pages_scanned += pgscanned;
	zone->nr_active -= pgmoved;
	spin_unlock_irq(&zone->lru_lock);

	/*
	 * `distress' is a measure of how much trouble we're having reclaiming
	 * pages.  0 -> no problems.  100 -> great trouble.
	 */
	distress = 100 >> zone->prev_priority;

	/*
	 * The point of this algorithm is to decide when to start reclaiming
	 * mapped memory instead of just pagecache.  Work out how much memory
	 * is mapped.
	 */
	mapped_ratio = (sc->nr_mapped * 100) / total_memory;

	/*
	 * Now decide how much we really want to unmap some pages.  The mapped
	 * ratio is downgraded - just because there's a lot of mapped memory
	 * doesn't necessarily mean that page reclaim isn't succeeding.
	 *
	 * The distress ratio is important - we don't want to start going oom.
	 *
	 * A 100% value of vm_swappiness overrides this algorithm altogether.
	 */
	swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;

	/*
	 * Now use this metric to decide whether to start moving mapped memory
	 * onto the inactive list.
	 */
	if (swap_tendency >= 100)
		reclaim_mapped = 1;

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
		if (page_mapped(page)) {
			if (!reclaim_mapped ||
			    (total_swap_pages == 0 && PageAnon(page)) ||
998
			    page_referenced(page, 0)) {
L
Linus Torvalds 已提交
999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054
				list_add(&page->lru, &l_active);
				continue;
			}
		}
		list_add(&page->lru, &l_inactive);
	}

	pagevec_init(&pvec, 1);
	pgmoved = 0;
	spin_lock_irq(&zone->lru_lock);
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
		if (TestSetPageLRU(page))
			BUG();
		if (!TestClearPageActive(page))
			BUG();
		list_move(&page->lru, &zone->inactive_list);
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
			zone->nr_inactive += pgmoved;
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	zone->nr_inactive += pgmoved;
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}

	pgmoved = 0;
	while (!list_empty(&l_active)) {
		page = lru_to_page(&l_active);
		prefetchw_prev_lru_page(page, &l_active, flags);
		if (TestSetPageLRU(page))
			BUG();
		BUG_ON(!PageActive(page));
		list_move(&page->lru, &zone->active_list);
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
			zone->nr_active += pgmoved;
			pgmoved = 0;
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	zone->nr_active += pgmoved;
N
Nick Piggin 已提交
1055 1056 1057 1058 1059
	spin_unlock(&zone->lru_lock);

	__mod_page_state_zone(zone, pgrefill, pgscanned);
	__mod_page_state(pgdeactivate, pgdeactivate);
	local_irq_enable();
L
Linus Torvalds 已提交
1060

N
Nick Piggin 已提交
1061
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072
}

/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
static void
shrink_zone(struct zone *zone, struct scan_control *sc)
{
	unsigned long nr_active;
	unsigned long nr_inactive;

1073 1074
	atomic_inc(&zone->reclaim_in_progress);

L
Linus Torvalds 已提交
1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109
	/*
	 * Add one to `nr_to_scan' just to make sure that the kernel will
	 * slowly sift through the active list.
	 */
	zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
	nr_active = zone->nr_scan_active;
	if (nr_active >= sc->swap_cluster_max)
		zone->nr_scan_active = 0;
	else
		nr_active = 0;

	zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
	nr_inactive = zone->nr_scan_inactive;
	if (nr_inactive >= sc->swap_cluster_max)
		zone->nr_scan_inactive = 0;
	else
		nr_inactive = 0;

	while (nr_active || nr_inactive) {
		if (nr_active) {
			sc->nr_to_scan = min(nr_active,
					(unsigned long)sc->swap_cluster_max);
			nr_active -= sc->nr_to_scan;
			refill_inactive_zone(zone, sc);
		}

		if (nr_inactive) {
			sc->nr_to_scan = min(nr_inactive,
					(unsigned long)sc->swap_cluster_max);
			nr_inactive -= sc->nr_to_scan;
			shrink_cache(zone, sc);
		}
	}

	throttle_vm_writeout();
1110 1111

	atomic_dec(&zone->reclaim_in_progress);
L
Linus Torvalds 已提交
1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137
}

/*
 * This is the direct reclaim path, for page-allocating processes.  We only
 * try to reclaim pages from zones which will satisfy the caller's allocation
 * request.
 *
 * We reclaim from a zone even if that zone is over pages_high.  Because:
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
 * b) The zones may be over pages_high but they must go *over* pages_high to
 *    satisfy the `incremental min' zone defense algorithm.
 *
 * Returns the number of reclaimed pages.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
static void
shrink_caches(struct zone **zones, struct scan_control *sc)
{
	int i;

	for (i = 0; zones[i] != NULL; i++) {
		struct zone *zone = zones[i];

1138
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1139 1140
			continue;

1141
		if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
L
Linus Torvalds 已提交
1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167
			continue;

		zone->temp_priority = sc->priority;
		if (zone->prev_priority > sc->priority)
			zone->prev_priority = sc->priority;

		if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
			continue;	/* Let kswapd poll it */

		shrink_zone(zone, sc);
	}
}
 
/*
 * This is the main entry point to direct page reclaim.
 *
 * If a full scan of the inactive list fails to free enough memory then we
 * are "out of memory" and something needs to be killed.
 *
 * If the caller is !__GFP_FS then the probability of a failure is reasonably
 * high - the zone may be full of dirty or under-writeback pages, which this
 * caller can't do much about.  We kick pdflush and take explicit naps in the
 * hope that some of these pages can be written.  But if the allocating task
 * holds filesystem locks which prevent writeout this might not work, and the
 * allocation attempt will fail.
 */
A
Al Viro 已提交
1168
int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
L
Linus Torvalds 已提交
1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185
{
	int priority;
	int ret = 0;
	int total_scanned = 0, total_reclaimed = 0;
	struct reclaim_state *reclaim_state = current->reclaim_state;
	struct scan_control sc;
	unsigned long lru_pages = 0;
	int i;

	sc.gfp_mask = gfp_mask;
	sc.may_writepage = 0;

	inc_page_state(allocstall);

	for (i = 0; zones[i] != NULL; i++) {
		struct zone *zone = zones[i];

1186
		if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
L
Linus Torvalds 已提交
1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198
			continue;

		zone->temp_priority = DEF_PRIORITY;
		lru_pages += zone->nr_active + zone->nr_inactive;
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		sc.nr_mapped = read_page_state(nr_mapped);
		sc.nr_scanned = 0;
		sc.nr_reclaimed = 0;
		sc.priority = priority;
		sc.swap_cluster_max = SWAP_CLUSTER_MAX;
1199 1200
		if (!priority)
			disable_swap_token();
L
Linus Torvalds 已提交
1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221
		shrink_caches(zones, &sc);
		shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
		if (reclaim_state) {
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
			reclaim_state->reclaimed_slab = 0;
		}
		total_scanned += sc.nr_scanned;
		total_reclaimed += sc.nr_reclaimed;
		if (total_reclaimed >= sc.swap_cluster_max) {
			ret = 1;
			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.
		 */
		if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
1222
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
L
Linus Torvalds 已提交
1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233
			sc.may_writepage = 1;
		}

		/* Take a nap, wait for some writeback to complete */
		if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
			blk_congestion_wait(WRITE, HZ/10);
	}
out:
	for (i = 0; zones[i] != 0; i++) {
		struct zone *zone = zones[i];

1234
		if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
L
Linus Torvalds 已提交
1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295
			continue;

		zone->prev_priority = zone->temp_priority;
	}
	return ret;
}

/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
 * they are all at pages_high.
 *
 * If `nr_pages' is non-zero then it is the number of pages which are to be
 * reclaimed, regardless of the zone occupancies.  This is a software suspend
 * special.
 *
 * Returns the number of pages which were actually freed.
 *
 * There is special handling here for zones which are full of pinned pages.
 * This can happen if the pages are all mlocked, or if they are all used by
 * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
 * What we do is to detect the case where all pages in the zone have been
 * scanned twice and there has been zero successful reclaim.  Mark the zone as
 * dead and from now on, only perform a short scan.  Basically we're polling
 * the zone for when the problem goes away.
 *
 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
 * zones which have free_pages > pages_high, but once a zone is found to have
 * free_pages <= pages_high, we scan that zone and the lower zones regardless
 * of the number of free pages in the lower zones.  This interoperates with
 * the page allocator fallback scheme to ensure that aging of pages is balanced
 * across the zones.
 */
static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
{
	int to_free = nr_pages;
	int all_zones_ok;
	int priority;
	int i;
	int total_scanned, total_reclaimed;
	struct reclaim_state *reclaim_state = current->reclaim_state;
	struct scan_control sc;

loop_again:
	total_scanned = 0;
	total_reclaimed = 0;
	sc.gfp_mask = GFP_KERNEL;
	sc.may_writepage = 0;
	sc.nr_mapped = read_page_state(nr_mapped);

	inc_page_state(pageoutrun);

	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		zone->temp_priority = DEF_PRIORITY;
	}

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

1296 1297 1298 1299
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1300 1301 1302 1303 1304 1305 1306 1307 1308 1309
		all_zones_ok = 1;

		if (nr_pages == 0) {
			/*
			 * 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;

1310
				if (!populated_zone(zone))
L
Linus Torvalds 已提交
1311 1312 1313 1314 1315 1316 1317
					continue;

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

				if (!zone_watermark_ok(zone, order,
R
Rohit Seth 已提交
1318
						zone->pages_high, 0, 0)) {
L
Linus Torvalds 已提交
1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344
					end_zone = i;
					goto scan;
				}
			}
			goto out;
		} else {
			end_zone = pgdat->nr_zones - 1;
		}
scan:
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

			lru_pages += zone->nr_active + zone->nr_inactive;
		}

		/*
		 * 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;
1345
			int nr_slab;
L
Linus Torvalds 已提交
1346

1347
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1348 1349 1350 1351 1352 1353 1354
				continue;

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

			if (nr_pages == 0) {	/* Not software suspend */
				if (!zone_watermark_ok(zone, order,
R
Rohit Seth 已提交
1355
						zone->pages_high, end_zone, 0))
L
Linus Torvalds 已提交
1356 1357 1358 1359 1360 1361 1362 1363 1364
					all_zones_ok = 0;
			}
			zone->temp_priority = priority;
			if (zone->prev_priority > priority)
				zone->prev_priority = priority;
			sc.nr_scanned = 0;
			sc.nr_reclaimed = 0;
			sc.priority = priority;
			sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
1365
			atomic_inc(&zone->reclaim_in_progress);
L
Linus Torvalds 已提交
1366
			shrink_zone(zone, &sc);
1367
			atomic_dec(&zone->reclaim_in_progress);
L
Linus Torvalds 已提交
1368
			reclaim_state->reclaimed_slab = 0;
1369 1370
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
L
Linus Torvalds 已提交
1371 1372 1373 1374 1375
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
			total_reclaimed += sc.nr_reclaimed;
			total_scanned += sc.nr_scanned;
			if (zone->all_unreclaimable)
				continue;
1376 1377
			if (nr_slab == 0 && zone->pages_scanned >=
				    (zone->nr_active + zone->nr_inactive) * 4)
L
Linus Torvalds 已提交
1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463
				zone->all_unreclaimable = 1;
			/*
			 * 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 &&
			    total_scanned > total_reclaimed+total_reclaimed/2)
				sc.may_writepage = 1;
		}
		if (nr_pages && to_free > total_reclaimed)
			continue;	/* swsusp: need to do more work */
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
		if (total_scanned && priority < DEF_PRIORITY - 2)
			blk_congestion_wait(WRITE, HZ/10);

		/*
		 * 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.
		 */
		if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
			break;
	}
out:
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		zone->prev_priority = zone->temp_priority;
	}
	if (!all_zones_ok) {
		cond_resched();
		goto loop_again;
	}

	return total_reclaimed;
}

/*
 * The background pageout daemon, started as a kernel thread
 * from the init process. 
 *
 * This basically trickles out pages so that we have _some_
 * free memory available even if there is no other activity
 * that frees anything up. This is needed for things like routing
 * etc, where we otherwise might have all activity going on in
 * asynchronous contexts that cannot page things out.
 *
 * If there are applications that are active memory-allocators
 * (most normal use), this basically shouldn't matter.
 */
static int kswapd(void *p)
{
	unsigned long order;
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
	cpumask_t cpumask;

	daemonize("kswapd%d", pgdat->node_id);
	cpumask = node_to_cpumask(pgdat->node_id);
	if (!cpus_empty(cpumask))
		set_cpus_allowed(tsk, cpumask);
	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).
	 */
1464
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
L
Linus Torvalds 已提交
1465 1466 1467 1468

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1469 1470

		try_to_freeze();
L
Linus Torvalds 已提交
1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498

		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
		new_order = pgdat->kswapd_max_order;
		pgdat->kswapd_max_order = 0;
		if (order < new_order) {
			/*
			 * Don't sleep if someone wants a larger 'order'
			 * allocation
			 */
			order = new_order;
		} else {
			schedule();
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

		balance_pgdat(pgdat, 0, order);
	}
	return 0;
}

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

1499
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
1500 1501 1502
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
1503
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
1504 1505 1506
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
1507
	if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
L
Linus Torvalds 已提交
1508
		return;
1509
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
1510
		return;
1511
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578
}

#ifdef CONFIG_PM
/*
 * Try to free `nr_pages' of memory, system-wide.  Returns the number of freed
 * pages.
 */
int shrink_all_memory(int nr_pages)
{
	pg_data_t *pgdat;
	int nr_to_free = nr_pages;
	int ret = 0;
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};

	current->reclaim_state = &reclaim_state;
	for_each_pgdat(pgdat) {
		int freed;
		freed = balance_pgdat(pgdat, nr_to_free, 0);
		ret += freed;
		nr_to_free -= freed;
		if (nr_to_free <= 0)
			break;
	}
	current->reclaim_state = NULL;
	return ret;
}
#endif

#ifdef CONFIG_HOTPLUG_CPU
/* 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. */
static int __devinit cpu_callback(struct notifier_block *nfb,
				  unsigned long action,
				  void *hcpu)
{
	pg_data_t *pgdat;
	cpumask_t mask;

	if (action == CPU_ONLINE) {
		for_each_pgdat(pgdat) {
			mask = node_to_cpumask(pgdat->node_id);
			if (any_online_cpu(mask) != NR_CPUS)
				/* One of our CPUs online: restore mask */
				set_cpus_allowed(pgdat->kswapd, mask);
		}
	}
	return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */

static int __init kswapd_init(void)
{
	pg_data_t *pgdat;
	swap_setup();
	for_each_pgdat(pgdat)
		pgdat->kswapd
		= find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
	total_memory = nr_free_pagecache_pages();
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)