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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2014-10-09 15:26:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-09 22:25:51 -0400
commitad2c8144418c6a81cefe65379fd47bbe8344cef2 (patch)
tree639b73b65d11424da81b76afbaeb8020e39ca050 /mm
parentc9e16131d6e39bddd183f0b9d787ec0a62bf0eeb (diff)
topology: add support for node_to_mem_node() to determine the fallback node
Anton noticed (http://www.spinics.net/lists/linux-mm/msg67489.html) that on ppc LPARs with memoryless nodes, a large amount of memory was consumed by slabs and was marked unreclaimable. He tracked it down to slab deactivations in the SLUB core when we allocate remotely, leading to poor efficiency always when memoryless nodes are present. After much discussion, Joonsoo provided a few patches that help significantly. They don't resolve the problem altogether: - memory hotplug still needs testing, that is when a memoryless node becomes memory-ful, we want to dtrt - there are other reasons for going off-node than memoryless nodes, e.g., fully exhausted local nodes Neither case is resolved with this series, but I don't think that should block their acceptance, as they can be explored/resolved with follow-on patches. The series consists of: [1/3] topology: add support for node_to_mem_node() to determine the fallback node [2/3] slub: fallback to node_to_mem_node() node if allocating on memoryless node - Joonsoo's patches to cache the nearest node with memory for each NUMA node [3/3] Partial revert of 81c98869faa5 (""kthread: ensure locality of task_struct allocations") - At Tejun's request, keep the knowledge of memoryless node fallback to the allocator core. This patch (of 3): We need to determine the fallback node in slub allocator if the allocation target node is memoryless node. Without it, the SLUB wrongly select the node which has no memory and can't use a partial slab, because of node mismatch. Introduced function, node_to_mem_node(X), will return a node Y with memory that has the nearest distance. If X is memoryless node, it will return nearest distance node, but, if X is normal node, it will return itself. We will use this function in following patch to determine the fallback node. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Han Pingtian <hanpt@linux.vnet.ibm.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Anton Blanchard <anton@samba.org> Cc: Christoph Lameter <cl@linux.com> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_alloc.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eee961958021..f3bc59f2ed52 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -85,6 +85,7 @@ EXPORT_PER_CPU_SYMBOL(numa_node);
*/
DEFINE_PER_CPU(int, _numa_mem_); /* Kernel "local memory" node */
EXPORT_PER_CPU_SYMBOL(_numa_mem_);
+int _node_numa_mem_[MAX_NUMNODES];
#endif
/*