[PATCH] Use min of two prio settings in calculating distress for reclaim (bbdb396a) · Commits · 戴 / test

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:

Martin J. Bligh <mbligh@google.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: <stable@kernel.org> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

mm/vmscan.c

+4 −4

Original line number	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.
		*/
		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;
		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
		* 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
		@@ -936,7 +936,7 @@ static unsigned long shrink_zone(int priority, struct zone *zone,
		nr_to_scan = min(nr_active,
		(unsigned long)sc->swap_cluster_max);
		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) {
		@@ -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) {
		zone->nr_scan_active = 0;
		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);
		}
		}

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