This is a note to let you know that I've just added the patch titled
vmscan: fix a livelock in kswapd
to the 2.6.39-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:
vmscan-fix-a-livelock-in-kswapd.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 4746efded84d7c5a9c8d64d4c6e814ff0cf9fb42 Mon Sep 17 00:00:00 2001
From: Shaohua Li <[email protected]>
Date: Tue, 19 Jul 2011 08:49:26 -0700
Subject: vmscan: fix a livelock in kswapd
From: Shaohua Li <[email protected]>
commit 4746efded84d7c5a9c8d64d4c6e814ff0cf9fb42 upstream.
I'm running a workload which triggers a lot of swap in a machine with 4
nodes. After I kill the workload, I found a kswapd livelock. Sometimes
kswapd3 or kswapd2 are keeping running and I can't access filesystem,
but most memory is free.
This looks like a regression since commit 08951e545918c159 ("mm: vmscan:
correct check for kswapd sleeping in sleeping_prematurely").
Node 2 and 3 have only ZONE_NORMAL, but balance_pgdat() will return 0
for classzone_idx. The reason is end_zone in balance_pgdat() is 0 by
default, if all zones have watermark ok, end_zone will keep 0.
Later sleeping_prematurely() always returns true. Because this is an
order 3 wakeup, and if classzone_idx is 0, both balanced_pages and
present_pages in pgdat_balanced() are 0. We add a special case here.
If a zone has no page, we think it's balanced. This fixes the livelock.
Signed-off-by: Shaohua Li <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/vmscan.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2245,7 +2245,8 @@ static bool pgdat_balanced(pg_data_t *pg
for (i = 0; i <= classzone_idx; i++)
present_pages += pgdat->node_zones[i].present_pages;
- return balanced_pages > (present_pages >> 2);
+ /* A special case here: if zone has no page, we think it's balanced */
+ return balanced_pages >= (present_pages >> 2);
}
/* is kswapd sleeping prematurely? */
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.39/vmscan-fix-a-livelock-in-kswapd.patch
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