linux-kernel - [PATCH] mm: Remove unlikely from the current

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Message-ID: <51BF8860.7010909@gmail.com>
Date:	Tue, 18 Jun 2013 06:06:24 +0800
From:	Zhang Yanfei <zhangyanfei.yes@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	David Rientjes <rientjes@...gle.com>,
	Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm: Remove unlikely from the current_order test

From: Zhang Yanfei <zhangyanfei@...fujitsu.com>

In __rmqueue_fallback(), current_order loops down from MAX_ORDER - 1
to the order passed. MAX_ORDER is typically 11 and pageblock_order
is typically 9 on x86. Integer division truncates, so pageblock_order / 2
is 4.  For the first eight iterations, it's guaranteed that
current_order >= pageblock_order / 2 if it even gets that far!

So just remove the unlikely(), it's completely bogus.

Suggested-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
---
 mm/page_alloc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c3edb62..7b4f367 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1050,7 +1050,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
 			 * MIGRATE_CMA areas.
 			 */
 			if (!is_migrate_cma(migratetype) &&
-			    (unlikely(current_order >= pageblock_order / 2) ||
+			    (current_order >= pageblock_order / 2 ||
 			     start_migratetype == MIGRATE_RECLAIMABLE ||
 			     page_group_by_mobility_disabled)) {
 				int pages;
-- 
1.7.1
--
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