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Commit c9ab0c4f authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm, page_alloc: remove unnecessary recalculations for dirty zone balancing 



File-backed pages that will be immediately written are balanced between
zones.  This heuristic tries to avoid having a single zone filled with
recently dirtied pages but the checks are unnecessarily expensive.  Move
consider_zone_balanced into the alloc_context instead of checking bitmaps
multiple times.  The patch also gives the parameter a more meaningful
name.

Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e2b19197

mm/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -129,6 +129,7 @@ struct alloc_context { 
	int classzone_idx;

	int migratetype;

	enum zone_type high_zoneidx;

	bool spread_dirty_pages;

};



/*

mm/page_alloc.c

+7 −4
Original line number Diff line number Diff line
@@ -2478,8 +2478,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, 
	nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */

	int zlc_active = 0;		/* set if using zonelist_cache */

	int did_zlc_setup = 0;		/* just call zlc_setup() one time */

	bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&

				(gfp_mask & __GFP_WRITE);

	int nr_fair_skipped = 0;

	bool zonelist_rescan;
@@ -2534,14 +2532,14 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, 
		 *

		 * XXX: For now, allow allocations to potentially

		 * exceed the per-zone dirty limit in the slowpath

		 * (ALLOC_WMARK_LOW unset) before going into reclaim,

		 * (spread_dirty_pages unset) before going into reclaim,

		 * which is important when on a NUMA setup the allowed

		 * zones are together not big enough to reach the

		 * global limit.  The proper fix for these situations

		 * will require awareness of zones in the

		 * dirty-throttling and the flusher threads.

		 */

		if (consider_zone_dirty && !zone_dirty_ok(zone))

		if (ac->spread_dirty_pages && !zone_dirty_ok(zone))

			continue;



		mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
@@ -3232,6 +3230,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, 


	/* We set it here, as __alloc_pages_slowpath might have changed it */

	ac.zonelist = zonelist;



	/* Dirty zone balancing only done in the fast path */

	ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);



	/* The preferred zone is used for statistics later */

	preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx,

				ac.nodemask ? : &cpuset_current_mems_allowed,
@@ -3250,6 +3252,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, 
		 * complete.

		 */

		alloc_mask = memalloc_noio_flags(gfp_mask);

		ac.spread_dirty_pages = false;



		page = __alloc_pages_slowpath(alloc_mask, order, &ac);

	}