linux-kernel - [PATCH 3/5] mm/memblock: reduce overhead in binary search

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Date:	Fri, 24 Aug 2012 22:33:38 +0800
From:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Subject: [PATCH 3/5] mm/memblock: reduce overhead in binary search

From: Wanpeng Li <liwanp@...ux.vnet.ibm.com>

When checking the indicated address belongs to the memory
or reserved region, the memory or reserved regions are checked
one by one through binary search, which would be a little
time consuming. If the indicated address isn't in memory
region, then we needn't do the time-sonsuming search. The
patch adds more check on the indicated address for that purpose.

Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
---
 mm/memblock.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 2feff8d..880e461 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -871,6 +871,10 @@ static int __init_memblock memblock_search(struct memblock_type *type, phys_addr
 {
 	unsigned int left = 0, right = type->cnt;
 
+	if (unlikely(addr < memblock_start_of_DRAM() ||
+		addr >= memblock_end_of_DRAM()))
+			return 0;
+
 	do {
 		unsigned int mid = (right + left) / 2;
 
-- 
1.7.5.4

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