Commit bc6488e9 authored Jul 26, 2010 by Christoph Lameter Committed by Pekka Enberg Jul 29, 2010

slub numa: Fix rare allocation from unexpected node



The network developers have seen sporadic allocations resulting in objects
coming from unexpected NUMA nodes despite asking for objects from a
specific node.

This is due to get_partial() calling get_any_partial() if partial
slabs are exhausted for a node even if a node was specified and therefore
one would expect allocations only from the specified node.

get_any_partial() sporadically may return a slab from a foreign
node to gradually reduce the size of partial lists on remote nodes
and thereby reduce total memory use for a slab cache.

The behavior is controlled by the remote_defrag_ratio of each cache.

Strictly speaking this is permitted behavior since __GFP_THISNODE was
not specified for the allocation but it is certain surprising.

This patch makes sure that the remote defrag behavior only occurs
if no node was specified.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

parent 7adde04a

mm/slub.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1390,7 +1390,7 @@ static struct page get_partial(struct kmem_cache s, gfp_t flags, int node)
		int searchnode = (node == -1) ? numa_node_id() : node;

		page = get_partial_node(get_node(s, searchnode));
		if (page \|\| (flags & __GFP_THISNODE))
		if (page \|\| node != -1)
		return page;

		return get_any_partial(s, flags);

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