From 73f038b863dfe98acabc7c36c17342b84ad52e94 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Wed, 18 Dec 2013 17:08:47 -0800
Subject: [PATCH] mm: page_alloc: exclude unreclaimable allocations from zone
fairness policy
Dave Hansen noted a regression in a microbenchmark that loops around
open() and close() on an 8-node NUMA machine and bisected it down to
commit 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy").
That change forces the slab allocations of the file descriptor to spread
out to all 8 nodes, causing remote references in the page allocator and
slab.
The round-robin policy is only there to provide fairness among memory
allocations that are reclaimed involuntarily based on pressure in each
zone. It does not make sense to apply it to unreclaimable kernel
allocations that are freed manually, in this case instantly after the
allocation, and incur the remote reference costs twice for no reason.
Only round-robin allocations that are usually freed through page reclaim
or slab shrinking.
Bisected by Dave Hansen.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/page_alloc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 580a5f075ed0ab..f861d0257e9004 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1920,7 +1920,8 @@ zonelist_scan:
* back to remote zones that do not partake in the
* fairness round-robin cycle of this zonelist.
*/
- if (alloc_flags & ALLOC_WMARK_LOW) {
+ if ((alloc_flags & ALLOC_WMARK_LOW) &&
+ (gfp_mask & GFP_MOVABLE_MASK)) {
if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0)
continue;
if (zone_reclaim_mode &&
--
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