[PATCH 03/10] mm, page_alloc: Remove unnecessary recalculations for dirty zone balancing

From: Mel Gorman
Date: Wed Aug 12 2015 - 06:45:46 EST


File-backed pages that will be immediately are balanced between zones but
it's 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@xxxxxxxxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/internal.h | 1 +
mm/page_alloc.c | 11 +++++++----
2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 36b23f1e2ca6..9331f802a067 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -129,6 +129,7 @@ struct alloc_context {
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 5e1f6f4370bc..94f2f6bdd6d5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2297,8 +2297,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
struct zoneref *z;
struct page *page = NULL;
struct zone *zone;
- bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
- (gfp_mask & __GFP_WRITE);
int nr_fair_skipped = 0;
bool zonelist_rescan;

@@ -2350,14 +2348,14 @@ 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];
@@ -2997,6 +2995,10 @@ __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, &ac.preferred_zone);
@@ -3014,6 +3016,7 @@ __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);
}
--
2.4.6

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/