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authorDavid Rientjes <rientjes@google.com>2010-05-24 14:32:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-25 08:06:58 -0700
commite325c90ffc13b698fa2814102e05275b21c26bec (patch)
treedcb20cad204132e08476d3cb4da66f9a2e08b9fe
parent1a5cb81465b66b74bf3d6ad36e5382238de6a132 (diff)
mm: default to node zonelist ordering when nodes have only lowmem
There are two types of zonelist ordering methodologies: - node order, preferring allocations on a node to stay local to and - zone order, preferring allocations come from a higher zone to avoid allocating in lowmem zones even though they may not be local. The ordering technique used by the kernel is configurable on the command line, but also has some logic to determine what the default should be. This logic currently lacks knowledge of systems where a node may only have lowmem. For such systems, it is necessary to use node order so that GFP_KERNEL allocations may be satisfied by nodes consisting of only lowmem. If zone order is used, GFP_KERNEL allocations to such nodes are actually allocated on a node with local affinity that includes ZONE_NORMAL. This change defaults to node zonelist ordering if any node lacks ZONE_NORMAL. To force zone order, append 'numa_zonelist_order=zone' to the kernel command line. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f7da2a2934b7..cefe6fe8d991 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2606,7 +2606,7 @@ static int default_zonelist_order(void)
* ZONE_DMA and ZONE_DMA32 can be very small area in the system.
* If they are really small and used heavily, the system can fall
* into OOM very easily.
- * This function detect ZONE_DMA/DMA32 size and confgigures zone order.
+ * This function detect ZONE_DMA/DMA32 size and configures zone order.
*/
/* Is there ZONE_NORMAL ? (ex. ppc has only DMA zone..) */
low_kmem_size = 0;
@@ -2618,6 +2618,15 @@ static int default_zonelist_order(void)
if (zone_type < ZONE_NORMAL)
low_kmem_size += z->present_pages;
total_size += z->present_pages;
+ } else if (zone_type == ZONE_NORMAL) {
+ /*
+ * If any node has only lowmem, then node order
+ * is preferred to allow kernel allocations
+ * locally; otherwise, they can easily infringe
+ * on other nodes when there is an abundance of
+ * lowmem available to allocate from.
+ */
+ return ZONELIST_ORDER_NODE;
}
}
}

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