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| author | Shaohua Li <shaohua.li@intel.com> | 2011-07-19 08:49:26 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-19 22:09:31 -0700 |
| commit | 4746efded84d7c5a9c8d64d4c6e814ff0cf9fb42 (patch) | |
| tree | 174f400db27c1a1d9a66407931199aabfdce6bba /mm/vmscan.c | |
| parent | f7b88631a89757d70192044c9d9f2e8d2fc02f2c (diff) | |
| download | linux-4746efded84d7c5a9c8d64d4c6e814ff0cf9fb42.tar.bz2 | |
vmscan: fix a livelock in kswapd
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 <shaohua.li@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
| -rw-r--r-- | mm/vmscan.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 5ed24b94c5e6..d036e59d302b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2310,7 +2310,8 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 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? */ |