Patchwork [12/32] mm: system wide ALLOC_NO_WATERMARK

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Submitter Peter Zijlstra
Date Oct. 2, 2008, 1:05 p.m.
Message ID <20081002131608.372668704@chello.nl>
Download mbox | patch
Permalink /patch/2387/
State Not Applicable
Delegated to: David Miller
Headers show

Comments

Peter Zijlstra - Oct. 2, 2008, 1:05 p.m.
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 don't 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@chello.nl>
---
 mm/page_alloc.c |    5 +++++
 1 file changed, 5 insertions(+)

Patch

Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -1533,6 +1533,11 @@  restart:
 rebalance:
 	if (alloc_flags & ALLOC_NO_WATERMARKS) {
 nofail_alloc:
+		/*
+		 * break out of mempolicy boundaries
+		 */
+		zonelist = node_zonelist(numa_node_id(), gfp_mask);
+
 		/* go through the zonelist yet again, ignoring mins */
 		page = get_page_from_freelist(gfp_mask, nodemask, order,
 				zonelist, high_zoneidx, ALLOC_NO_WATERMARKS);