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Commit 4ff1ffb4 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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[PATCH] oom: reclaim_mapped on oom 



Potentially it takes several scans of the lru lists before we can even start
reclaiming pages.

mapped pages, with young ptes can take 2 passes on the active list + one on
the inactive list.  But reclaim_mapped may not always kick in instantly, so it
could take even more than that.

Raise the threshold for marking a zone as all_unreclaimable from a factor of 4
time the pages in the zone to 6.  Introduce a mechanism to force
reclaim_mapped if we've reached a factor 3 and still haven't made progress.

Previously, a customer doing stress testing was able to easily OOM the box
after using only a small fraction of its swap (~100MB).  After the patches, it
would only OOM after having used up all swap (~800MB).

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 408d8544

mm/vmscan.c

+10 −1
Original line number Diff line number Diff line
@@ -697,6 +697,11 @@ static unsigned long shrink_inactive_list(unsigned long max_scan, 
	return nr_reclaimed;

}



static inline int zone_is_near_oom(struct zone *zone)

{

	return zone->pages_scanned >= (zone->nr_active + zone->nr_inactive)*3;

}



/*

 * This moves pages from the active list to the inactive list.

 *
@@ -732,6 +737,9 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 
		long distress;

		long swap_tendency;



		if (zone_is_near_oom(zone))

			goto force_reclaim_mapped;



		/*

		 * `distress' is a measure of how much trouble we're having

		 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
@@ -767,6 +775,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 
		 * memory onto the inactive list.

		 */

		if (swap_tendency >= 100)

force_reclaim_mapped:

			reclaim_mapped = 1;

	}
@@ -1161,7 +1170,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order) 
			if (zone->all_unreclaimable)

				continue;

			if (nr_slab == 0 && zone->pages_scanned >=

				    (zone->nr_active + zone->nr_inactive) * 4)

				    (zone->nr_active + zone->nr_inactive) * 6)

				zone->all_unreclaimable = 1;

			/*

			 * If we've done a decent amount of scanning and