Commit 3b8c0be4 authored Jul 28, 2016 by Mel Gorman Committed by Linus Torvalds Jul 28, 2016

mm: page_alloc: cache the last node whose dirty limit is reached

If a page is about to be dirtied then the page allocator attempts to
limit the total number of dirty pages that exists in any given zone.
The call to node_dirty_ok is expensive so this patch records if the last
pgdat examined hit the dirty limits.  In some cases, this reduces the
number of calls to node_dirty_ok().

Link: http://lkml.kernel.org/r/1467970510-21195-31-git-send-email-mgorman@techsingularity.net


Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e6cbd7f2

mm/page_alloc.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -2848,6 +2848,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
		{
		struct zoneref *z = ac->preferred_zoneref;
		struct zone *zone;
		struct pglist_data *last_pgdat_dirty_limit = NULL;

		/*
		* Scan zonelist, looking for a zone with enough free.
		* See also __cpuset_node_allowed() comment in kernel/cpuset.c.
		@@ -2880,8 +2882,15 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
		* will require awareness of nodes in the
		* dirty-throttling and the flusher threads.
		*/
		if (ac->spread_dirty_pages && !node_dirty_ok(zone->zone_pgdat))
		if (ac->spread_dirty_pages) {
		if (last_pgdat_dirty_limit == zone->zone_pgdat)
		continue;

		if (!node_dirty_ok(zone->zone_pgdat)) {
		last_pgdat_dirty_limit = zone->zone_pgdat;
		continue;
		}
		}

		mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
		if (!zone_watermark_fast(zone, order, mark,