Messages in this thread Patch in this message | | | Date | Mon, 01 Aug 2011 16:19:10 -0700 | From | Greg KH <> | Subject | [55/70] vmscan: fix a livelock in kswapd |
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2.6.39-stable review patch. If anyone has any objections, please let us know.
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From: Shaohua Li <shaohua.li@intel.com>
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 <shaohua.li@intel.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- 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? */
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