This is a note to let you know that I've just added the patch titled
mm: page_alloc: fix zone allocation fairness on UP
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-fix-zone-allocation-fairness-on-up.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 abe5f972912d086c080be4bde67750630b6fb38b Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Date: Thu, 2 Oct 2014 16:21:10 -0700
Subject: mm: page_alloc: fix zone allocation fairness on UP
From: Johannes Weiner <hannes@xxxxxxxxxxx>
commit abe5f972912d086c080be4bde67750630b6fb38b upstream.
The zone allocation batches can easily underflow due to higher-order
allocations or spills to remote nodes. On SMP that's fine, because
underflows are expected from concurrency and dealt with by returning 0.
But on UP, zone_page_state will just return a wrapped unsigned long,
which will get past the <= 0 check and then consider the zone eligible
until its watermarks are hit.
Commit 3a025760fc15 ("mm: page_alloc: spill to remote nodes before
waking kswapd") already made the counter-resetting use
atomic_long_read() to accomodate underflows from remote spills, but it
didn't go all the way with it.
Make it clear that these batches are expected to go negative regardless
of concurrency, and use atomic_long_read() everywhere.
Fixes: 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy")
Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
Reported-by: Leon Romanovsky <leon@xxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.12+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1957,7 +1957,7 @@ zonelist_scan:
if (alloc_flags & ALLOC_FAIR) {
if (!zone_local(preferred_zone, zone))
continue;
- if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0)
+ if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0)
continue;
}
/*
@@ -5670,9 +5670,8 @@ static void __setup_per_zone_wmarks(void
zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1);
__mod_zone_page_state(zone, NR_ALLOC_BATCH,
- high_wmark_pages(zone) -
- low_wmark_pages(zone) -
- zone_page_state(zone, NR_ALLOC_BATCH));
+ high_wmark_pages(zone) - low_wmark_pages(zone) -
+ atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
setup_zone_migrate_reserve(zone);
spin_unlock_irqrestore(&zone->lock, flags);
Patches currently in stable-queue which might be from hannes@xxxxxxxxxxx are
queue-3.14/mm-memcontrol-do-not-iterate-uninitialized-memcgs.patch
queue-3.14/cgroup-kmemleak-add-kmemleak_free-for-cgroup-deallocations.patch
queue-3.14/mm-page_alloc-fix-zone-allocation-fairness-on-up.patch
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