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Commit bc6488e9 authored by Christoph Lameter's avatar Christoph Lameter Committed by Pekka Enberg
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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: default avatarChristoph Lameter <cl@linux-foundation.org>
Signed-off-by: default avatarPekka 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);