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: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/internal.h b/mm/internal.h
index d4b807d..ff0f1ad 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -129,6 +129,7 @@
int classzone_idx;
int migratetype;
enum zone_type high_zoneidx;
+ bool spread_dirty_pages;
};
/*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d73c346..6739098 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2478,8 +2478,6 @@
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 @@
*
* 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 @@
/* 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 @@
* complete.
*/
alloc_mask = memalloc_noio_flags(gfp_mask);
+ ac.spread_dirty_pages = false;
page = __alloc_pages_slowpath(alloc_mask, order, &ac);
}