linux-kernel - [PATCH 2/2] mm: page_alloc: avoid slowpath for more than MAX

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Message-id: <1374492762-17735-1-git-send-email-pintu.k@samsung.com>
Date:	Mon, 22 Jul 2013 17:02:42 +0530
From:	Pintu Kumar <pintu.k@...sung.com>
To:	akpm@...ux-foundation.org, mgorman@...e.de, jiang.liu@...wei.com,
	minchan@...nel.org, cody@...ux.vnet.ibm.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc:	cpgs@...sung.com, pintu.k@...sung.com, pintu_agarwal@...oo.com
Subject: [PATCH 2/2] mm: page_alloc: avoid slowpath for more than MAX_ORDER
 allocation.

It was observed that if order is passed as more than MAX_ORDER
allocation in __alloc_pages_nodemask, it will unnecessarily go to
slowpath and then return failure.
Since we know that more than MAX_ORDER will anyways fail, we can
avoid slowpath by returning failure in nodemask itself.

Signed-off-by: Pintu Kumar <pintu.k@...sung.com>
---
 mm/page_alloc.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 202ab58..6d38e75 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1564,6 +1564,10 @@ __setup("fail_page_alloc=", setup_fail_page_alloc);
 
 static bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
+	if (order >= MAX_ORDER) {
+		WARN_ON(!(gfp_mask & __GFP_NOWARN));
+		return false;
+	}
 	if (order < fail_page_alloc.min_order)
 		return false;
 	if (gfp_mask & __GFP_NOFAIL)
-- 
1.7.9.5

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