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Commit f7b7fd8f authored by Rik van Riel's avatar Rik van Riel Committed by Linus Torvalds
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[PATCH] temporarily disable swap token on memory pressure 



Some users (hi Zwane) have seen a problem when running a workload that
eats nearly all of physical memory - th system does an OOM kill, even
when there is still a lot of swap free.

The problem appears to be a very big task that is holding the swap
token, and the VM has a very hard time finding any other page in the
system that is swappable.

Instead of ignoring the swap token when sc->priority reaches 0, we could
simply take the swap token away from the memory hog and make sure we
don't give it back to the memory hog for a few seconds.

This patch resolves the problem Zwane ran into.

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a93a117e

include/linux/rmap.h

+2 −2
Original line number Diff line number Diff line
@@ -89,7 +89,7 @@ static inline void page_dup_rmap(struct page *page) 
/*

 * Called from mm/vmscan.c to handle paging out

 */

int page_referenced(struct page *, int is_locked, int ignore_token);

int page_referenced(struct page *, int is_locked);

int try_to_unmap(struct page *);



/*
@@ -109,7 +109,7 @@ unsigned long page_address_in_vma(struct page *, struct vm_area_struct *); 
#define anon_vma_prepare(vma)	(0)

#define anon_vma_link(vma)	do {} while (0)



#define page_referenced(page,l,i) TestClearPageReferenced(page)

#define page_referenced(page,l) TestClearPageReferenced(page)

#define try_to_unmap(page)	SWAP_FAIL



#endif	/* CONFIG_MMU */

include/linux/swap.h

+6 −0
Original line number Diff line number Diff line
@@ -239,6 +239,11 @@ static inline void put_swap_token(struct mm_struct *mm) 
		__put_swap_token(mm);

}



static inline void disable_swap_token(void)

{

	put_swap_token(swap_token_mm);

}



#else /* CONFIG_SWAP */



#define total_swap_pages			0
@@ -283,6 +288,7 @@ static inline swp_entry_t get_swap_page(void) 
#define put_swap_token(x) do { } while(0)

#define grab_swap_token()  do { } while(0)

#define has_swap_token(x) 0

#define disable_swap_token() do { } while(0)



#endif /* CONFIG_SWAP */

#endif /* __KERNEL__*/

mm/rmap.c

+10 −16
Original line number Diff line number Diff line
@@ -290,7 +290,7 @@ pte_t *page_check_address(struct page *page, struct mm_struct *mm, 
 * repeatedly from either page_referenced_anon or page_referenced_file.

 */

static int page_referenced_one(struct page *page,

	struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)

	struct vm_area_struct *vma, unsigned int *mapcount)

{

	struct mm_struct *mm = vma->vm_mm;

	unsigned long address;
@@ -311,7 +311,7 @@ static int page_referenced_one(struct page *page, 


	/* Pretend the page is referenced if the task has the

	   swap token and is in the middle of a page fault. */

	if (mm != current->mm && !ignore_token && has_swap_token(mm) &&

	if (mm != current->mm && has_swap_token(mm) &&

			rwsem_is_locked(&mm->mmap_sem))

		referenced++;
@@ -321,7 +321,7 @@ out: 
	return referenced;

}



static int page_referenced_anon(struct page *page, int ignore_token)

static int page_referenced_anon(struct page *page)

{

	unsigned int mapcount;

	struct anon_vma *anon_vma;
@@ -334,8 +334,7 @@ static int page_referenced_anon(struct page *page, int ignore_token) 


	mapcount = page_mapcount(page);

	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {

		referenced += page_referenced_one(page, vma, &mapcount,

							ignore_token);

		referenced += page_referenced_one(page, vma, &mapcount);

		if (!mapcount)

			break;

	}
@@ -354,7 +353,7 @@ static int page_referenced_anon(struct page *page, int ignore_token) 
 *

 * This function is only called from page_referenced for object-based pages.

 */

static int page_referenced_file(struct page *page, int ignore_token)

static int page_referenced_file(struct page *page)

{

	unsigned int mapcount;

	struct address_space *mapping = page->mapping;
@@ -392,8 +391,7 @@ static int page_referenced_file(struct page *page, int ignore_token) 
			referenced++;

			break;

		}

		referenced += page_referenced_one(page, vma, &mapcount,

							ignore_token);

		referenced += page_referenced_one(page, vma, &mapcount);

		if (!mapcount)

			break;

	}
@@ -410,13 +408,10 @@ static int page_referenced_file(struct page *page, int ignore_token) 
 * Quick test_and_clear_referenced for all mappings to a page,

 * returns the number of ptes which referenced the page.

 */

int page_referenced(struct page *page, int is_locked, int ignore_token)

int page_referenced(struct page *page, int is_locked)

{

	int referenced = 0;



	if (!swap_token_default_timeout)

		ignore_token = 1;



	if (page_test_and_clear_young(page))

		referenced++;
@@ -425,15 +420,14 @@ int page_referenced(struct page *page, int is_locked, int ignore_token) 


	if (page_mapped(page) && page->mapping) {

		if (PageAnon(page))

			referenced += page_referenced_anon(page, ignore_token);

			referenced += page_referenced_anon(page);

		else if (is_locked)

			referenced += page_referenced_file(page, ignore_token);

			referenced += page_referenced_file(page);

		else if (TestSetPageLocked(page))

			referenced++;

		else {

			if (page->mapping)

				referenced += page_referenced_file(page,

								ignore_token);

				referenced += page_referenced_file(page);

			unlock_page(page);

		}

	}

mm/thrash.c

+7 −3
Original line number Diff line number Diff line
@@ -57,14 +57,17 @@ void grab_swap_token(void) 
	/* We have the token. Let others know we still need it. */

	if (has_swap_token(current->mm)) {

		current->mm->recent_pagein = 1;

		if (unlikely(!swap_token_default_timeout))

			disable_swap_token();

		return;

	}



	if (time_after(jiffies, swap_token_check)) {



		/* Can't get swapout protection if we exceed our RSS limit. */

		// if (current->mm->rss > current->mm->rlimit_rss)

		//	return;

		if (!swap_token_default_timeout) {

			swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;

			return;

		}



		/* ... or if we recently held the token. */

		if (time_before(jiffies, current->mm->swap_token_time))
@@ -95,6 +98,7 @@ void __put_swap_token(struct mm_struct *mm) 
{

	spin_lock(&swap_token_lock);

	if (likely(mm == swap_token_mm)) {

		mm->swap_token_time = jiffies + SWAP_TOKEN_CHECK_INTERVAL;

		swap_token_mm = &init_mm;

		swap_token_check = jiffies;

	}

mm/vmscan.c

+9 −2
Original line number Diff line number Diff line
@@ -407,7 +407,7 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc) 
		if (PageWriteback(page))

			goto keep_locked;



		referenced = page_referenced(page, 1, sc->priority <= 0);

		referenced = page_referenced(page, 1);

		/* In active use or really unfreeable?  Activate it. */

		if (referenced && page_mapping_inuse(page))

			goto activate_locked;
@@ -756,7 +756,7 @@ refill_inactive_zone(struct zone *zone, struct scan_control *sc) 
		if (page_mapped(page)) {

			if (!reclaim_mapped ||

			    (total_swap_pages == 0 && PageAnon(page)) ||

			    page_referenced(page, 0, sc->priority <= 0)) {

			    page_referenced(page, 0)) {

				list_add(&page->lru, &l_active);

				continue;

			}
@@ -960,6 +960,8 @@ int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) 
		sc.nr_reclaimed = 0;

		sc.priority = priority;

		sc.swap_cluster_max = SWAP_CLUSTER_MAX;

		if (!priority)

			disable_swap_token();

		shrink_caches(zones, &sc);

		shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);

		if (reclaim_state) {
@@ -1056,6 +1058,10 @@ loop_again: 
		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */

		unsigned long lru_pages = 0;



		/* The swap token gets in the way of swapout... */

		if (!priority)

			disable_swap_token();



		all_zones_ok = 1;



		if (nr_pages == 0) {
@@ -1360,6 +1366,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
	sc.nr_reclaimed = 0;

	/* scan at the highest priority */

	sc.priority = 0;

	disable_swap_token();



	if (nr_pages > SWAP_CLUSTER_MAX)

		sc.swap_cluster_max = nr_pages;