[PATCH 05/15] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK

From: Mel Gorman
Date: Mon Feb 06 2012 - 18:04:26 EST

The reserve is proportionally distributed over all !highmem zones
in the system. So we need to allow an emergency allocation access to
all zones. In order to do that we need to break out of any mempolicy
boundaries we might have.

In my opinion that does not break mempolicies as those are user
oriented and not system oriented. That is, system allocations are
not guaranteed to be within mempolicy boundaries. For instance IRQs
do not even have a mempolicy.

So breaking out of mempolicy boundaries for 'rare' emergency
allocations, which are always system allocations (as opposed to user)
is ok.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
mm/page_alloc.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b462585..7c26962 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2256,6 +2256,13 @@ rebalance:

/* Allocate without watermarks if the context allows */
if (alloc_flags & ALLOC_NO_WATERMARKS) {
+ /*
+ * Ignore mempolicies if ALLOC_NO_WATERMARKS on the grounds
+ * the allocation is high priority and these type of
+ * allocations are system rather than user orientated
+ */
+ zonelist = node_zonelist(numa_node_id(), gfp_mask);
page = __alloc_pages_high_priority(gfp_mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);

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