This is a note to let you know that I've just added the patch titled
mm: page_alloc: take the ALLOC_NO_WATERMARK check out of the fast path
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-page_alloc-take-the-alloc_no_watermark-check-out-of-the-fast-path.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5dab29113ca56335c78be3f98bf5ddf2ef8eb6a6 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@xxxxxxx>
Date: Wed, 4 Jun 2014 16:10:14 -0700
Subject: mm: page_alloc: take the ALLOC_NO_WATERMARK check out of the fast path
From: Mel Gorman <mgorman@xxxxxxx>
commit 5dab29113ca56335c78be3f98bf5ddf2ef8eb6a6 upstream.
ALLOC_NO_WATERMARK is set in a few cases. Always by kswapd, always for
__GFP_MEMALLOC, sometimes for swap-over-nfs, tasks etc. Each of these
cases are relatively rare events but the ALLOC_NO_WATERMARK check is an
unlikely branch in the fast path. This patch moves the check out of the
fast path and after it has been determined that the watermarks have not
been met. This helps the common fast path at the cost of making the slow
path slower and hitting kswapd with a performance cost. It's a reasonable
tradeoff.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1959,9 +1959,6 @@ zonelist_scan:
(alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed_softwall(zone, gfp_mask))
continue;
- BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
- if (unlikely(alloc_flags & ALLOC_NO_WATERMARKS))
- goto try_this_zone;
/*
* Distribute pages in proportion to the individual
* zone size to ensure fair page aging. The zone a
@@ -2008,6 +2005,11 @@ zonelist_scan:
classzone_idx, alloc_flags)) {
int ret;
+ /* Checked here to keep the fast path fast */
+ BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
+ if (alloc_flags & ALLOC_NO_WATERMARKS)
+ goto try_this_zone;
+
if (IS_ENABLED(CONFIG_NUMA) &&
!did_zlc_setup && nr_online_nodes > 1) {
/*
Patches currently in stable-queue which might be from mgorman@xxxxxxx are
queue-3.14/mm-page_alloc-use-jump-labels-to-avoid-checking-number_of_cpusets.patch
queue-3.14/mm-page_alloc-do-not-treat-a-zone-that-cannot-be-used-for-dirty-pages-as-full.patch
queue-3.14/mm-non-atomically-mark-page-accessed-during-page-cache-allocation-where-possible.patch
queue-3.14/mm-page_alloc-convert-hot-cold-parameter-and-immediate-callers-to-bool.patch
queue-3.14/mm-page_alloc-only-check-the-zone-id-check-if-pages-are-buddies.patch
queue-3.14/mm-page_alloc-only-check-the-alloc-flags-and-gfp_mask-for-dirty-once.patch
queue-3.14/mm-page_alloc-do-not-update-zlc-unless-the-zlc-is-active.patch
queue-3.14/mm-swap.c-clean-up-lru_cache_add-functions.patch
queue-3.14/mm-page_alloc-take-the-alloc_no_watermark-check-out-of-the-fast-path.patch
queue-3.14/fs-buffer-do-not-use-unnecessary-atomic-operations-when-discarding-buffers.patch
queue-3.14/mm-do-not-use-atomic-operations-when-releasing-pages.patch
queue-3.14/mm-page_alloc-reduce-number-of-times-page_to_pfn-is-called.patch
queue-3.14/mm-page_alloc-use-unsigned-int-for-order-in-more-places.patch
queue-3.14/mm-shmem-avoid-atomic-operation-during-shmem_getpage_gfp.patch
queue-3.14/mm-do-not-use-unnecessary-atomic-operations-when-adding-pages-to-the-lru.patch
queue-3.14/include-linux-jump_label.h-expose-the-reference-count.patch
queue-3.14/mm-page_alloc-calculate-classzone_idx-once-from-the.patch
queue-3.14/mm-page_alloc-lookup-pageblock-migratetype-with-irqs-enabled-during-free.patch
--
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