Re: OOM-killer invoked but why ?

From: Andrew Morton
Date: Tue Feb 05 2008 - 05:07:57 EST


On Thu, 31 Jan 2008 13:53:05 +0100 Claude Frantz <r31dmaeu@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

> Hello !
>
> I'm faced to a problem where the OOM-killer is invoked but I cannot find
> the reason why. The machine is rather powerfull, the load is very moderate,
> the disk swap space is nearly unused. The only strange observation which
> appears to me is the slow but progressive decreasing of kbbuffers during
> many hours.
>
> Can you help me to diagnose the problem and to find a good solution ?
>
> ...
>
> Jan 28 03:50:49 toaster kernel: 177466 pages slab
> Jan 28 03:50:49 toaster kernel: 1915 pages pagetables
> Jan 28 03:50:49 toaster kernel: Out of memory: kill process 10859 (amavisd) score 36218 or a child
> Jan 28 03:50:49 toaster kernel: Killed process 19146 (amavisd)

slab. Maybe you've been bitten by the quicklist leak. If you're able to
patch your kernel then please try this fix:

commit 96990a4ae979df9e235d01097d6175759331e88c
Author: Christoph Lameter <clameter@xxxxxxx>
Date: Mon Jan 14 00:55:14 2008 -0800

quicklists: Only consider memory that can be used with GFP_KERNEL

Quicklists calculates the size of the quicklists based on the number of
free pages. This must be the number of free pages that can be allocated
with GFP_KERNEL. node_page_state() includes the pages in ZONE_HIGHMEM and
ZONE_MOVABLE which may lead the quicklists to become too large causing OOM.

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Tested-by: Dhaval Giani <dhaval@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

diff --git a/mm/quicklist.c b/mm/quicklist.c
index ae8189c..3f703f7 100644
--- a/mm/quicklist.c
+++ b/mm/quicklist.c
@@ -26,9 +26,17 @@ DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
static unsigned long max_pages(unsigned long min_pages)
{
unsigned long node_free_pages, max;
+ struct zone *zones = NODE_DATA(numa_node_id())->node_zones;
+
+ node_free_pages =
+#ifdef CONFIG_ZONE_DMA
+ zone_page_state(&zones[ZONE_DMA], NR_FREE_PAGES) +
+#endif
+#ifdef CONFIG_ZONE_DMA32
+ zone_page_state(&zones[ZONE_DMA32], NR_FREE_PAGES) +
+#endif
+ zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES);

- node_free_pages = node_page_state(numa_node_id(),
- NR_FREE_PAGES);
max = node_free_pages / FRACTION_OF_NODE_MEM;
return max(max, min_pages);
}


I note that this didn't have the stable@xxxxxxxxxx cc. Christoph, did we
deliberately decide not to backport?

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