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authorJohannes Weiner <hannes@cmpxchg.org>2014-10-03 01:21:10 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-03 01:28:44 +0200
commitabe5f972912d086c080be4bde67750630b6fb38b (patch)
treea601d6b5a7cb3733492d7c1591df135b95c1f4bb /mm/page_alloc.c
parentperf: fix perf bug in fork() (diff)
downloadlinux-abe5f972912d086c080be4bde67750630b6fb38b.tar.xz
linux-abe5f972912d086c080be4bde67750630b6fb38b.zip
mm: page_alloc: fix zone allocation fairness on UP
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@suse.cz> Reported-by: Leon Romanovsky <leon@leon.nu> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: <stable@vger.kernel.org> [3.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/page_alloc.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 18cee0d4c8a2..eee961958021 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1612,7 +1612,7 @@ again:
}
__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
- if (zone_page_state(zone, NR_ALLOC_BATCH) == 0 &&
+ if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0 &&
!zone_is_fair_depleted(zone))
zone_set_flag(zone, ZONE_FAIR_DEPLETED);
@@ -5701,9 +5701,8 @@ 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);