linux-kernel - [BUG ?] oom with empty nodes.

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Message-Id: <20061221161608.27f81383.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 21 Dec 2006 16:16:08 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Christoph Lameter <clameter@...r.sgi.com>, npiggin@...e.de,
	Andrew Morton <akpm@...l.org>, GOTO <y-goto@...fujitsu.com>
Subject: [BUG ?] oom with empty nodes.

On some system, there are memory-less-nodes. (IOW, cpu-only-node)
Then,there are online nodes which has no memory.

Now, below code is used to detect the context where oom happens.

===
static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
{
#ifdef CONFIG_NUMA
        struct zone **z;
        nodemask_t nodes = node_online_map;

        for (z = zonelist->zones; *z; z++)
                if (cpuset_zone_allowed_softwall(*z, gfp_mask))
                        node_clear(zone_to_nid(*z), nodes);
                else
                        return CONSTRAINT_CPUSET;

        if (!nodes_empty(nodes))
                return CONSTRAINT_MEMORY_POLICY;
#endif

        return CONSTRAINT_NONE;
}
==
Because the zonelist never incldues memory-less-zone, above nodemask cannot be
empty if there is a memoly-less-node, never returns CONSTRAINT_NONE.

It looks select_bad_process() and panic_on_oom is checked only when
above function returns CONSTRAINT_NONE. This means current dies every time.

Does anyone have good idea for fix this ?

-Kame


 

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