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Commit bbdb396a authored by Martin Bligh's avatar Martin Bligh Committed by Linus Torvalds
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[PATCH] Use min of two prio settings in calculating distress for reclaim 



If try_to_free_pages / balance_pgdat are called with a gfp_mask specifying
GFP_IO and/or GFP_FS, they will reclaim the requisite number of pages, and the
reset prev_priority to DEF_PRIORITY (or to some other high (ie: unurgent)
value).

However, another reclaimer without those gfp_mask flags set (say, GFP_NOIO)
may still be struggling to reclaim pages.  The concurrent overwrite of
zone->prev_priority will cause this GFP_NOIO thread to unexpectedly cease
deactivating mapped pages, thus causing reclaim difficulties.

Fix this is to key the distress calculation not off zone->prev_priority, but
also take into account the local caller's priority by using
min(zone->prev_priority, sc->priority)

Signed-off-by: default avatarMartin J. Bligh <mbligh@google.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3bb1a852

mm/vmscan.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -760,7 +760,7 @@ static inline int zone_is_near_oom(struct zone *zone) 
 * But we had to alter page->flags anyway.

 * But we had to alter page->flags anyway.

 */

 */

static void shrink_active_list(unsigned long nr_pages, struct zone *zone,

static void shrink_active_list(unsigned long nr_pages, struct zone *zone,

				struct scan_control *sc)

				struct scan_control *sc, int priority)

{

{

	unsigned long pgmoved;

	unsigned long pgmoved;

	int pgdeactivate = 0;

	int pgdeactivate = 0;
@@ -784,7 +784,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 
		 * `distress' is a measure of how much trouble we're having

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

		 * reclaiming pages.  0 -> no problems.  100 -> great trouble.

		 * reclaiming pages.  0 -> no problems.  100 -> great trouble.

		 */

		 */

		distress = 100 >> zone->prev_priority;

		distress = 100 >> min(zone->prev_priority, priority);





		/*

		/*

		 * The point of this algorithm is to decide when to start

		 * The point of this algorithm is to decide when to start
@@ -936,7 +936,7 @@ static unsigned long shrink_zone(int priority, struct zone *zone, 
			nr_to_scan = min(nr_active,

			nr_to_scan = min(nr_active,

					(unsigned long)sc->swap_cluster_max);

					(unsigned long)sc->swap_cluster_max);

			nr_active -= nr_to_scan;

			nr_active -= nr_to_scan;

			shrink_active_list(nr_to_scan, zone, sc);

			shrink_active_list(nr_to_scan, zone, sc, priority);

		}

		}





		if (nr_inactive) {

		if (nr_inactive) {
@@ -1384,7 +1384,7 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int pass, 
			if (zone->nr_scan_active >= nr_pages || pass > 3) {

			if (zone->nr_scan_active >= nr_pages || pass > 3) {

				zone->nr_scan_active = 0;

				zone->nr_scan_active = 0;

				nr_to_scan = min(nr_pages, zone->nr_active);

				nr_to_scan = min(nr_pages, zone->nr_active);

				shrink_active_list(nr_to_scan, zone, sc);

				shrink_active_list(nr_to_scan, zone, sc, prio);

			}

			}

		}

		}