linux-kernel - [patch v2 for-4.0] mm, thp: really limit transparent hugepage allocation to local node

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Message-ID: <alpine.DEB.2.10.1502241522590.9480@chino.kir.corp.google.com>
Date:	Tue, 24 Feb 2015 15:24:54 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Greg Thelen <gthelen@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [patch v2 for-4.0] mm, thp: really limit transparent hugepage
 allocation to local node

From: Greg Thelen <gthelen@...gle.com>

Commit 077fcf116c8c ("mm/thp: allocate transparent hugepages on local
node") restructured alloc_hugepage_vma() with the intent of only
allocating transparent hugepages locally when there was not an effective
interleave mempolicy.

alloc_pages_exact_node() does not limit the allocation to the single
node, however, but rather prefers it.  This is because __GFP_THISNODE is
not set which would cause the node-local nodemask to be passed.  Without
it, only a nodemask that prefers the local node is passed.

Fix this by passing __GFP_THISNODE and falling back to small pages when
the allocation fails.

Fixes: 077fcf116c8c ("mm/thp: allocate transparent hugepages on local node")
Signed-off-by: Greg Thelen <gthelen@...gle.com>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 v2: GFP_THISNODE actually defers compaction and reclaim entirely based on
     the combination of gfp flags.  We want to try compaction and reclaim,
     so only set __GFP_THISNODE.  We still set __GFP_NOWARN to suppress 
     oom warnings in the kernel log when we can simply fallback to small
     pages.

 mm/mempolicy.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1985,7 +1985,10 @@ retry_cpuset:
 		nmask = policy_nodemask(gfp, pol);
 		if (!nmask || node_isset(node, *nmask)) {
 			mpol_cond_put(pol);
-			page = alloc_pages_exact_node(node, gfp, order);
+			page = alloc_pages_exact_node(node, gfp |
+							    __GFP_THISNODE |
+							    __GFP_NOWARN,
+						      order);
 			goto out;
 		}
 	}
--
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