linux-kernel - [PATCH v2 1/4] mm/memblock: reduce overhead in binary search

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Date:	Sun, 26 Aug 2012 17:00:23 +0800
From:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan@...nel.org>,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Subject: [PATCH v2 1/4] mm/memblock: reduce overhead in binary search

"v1 -> v2": 
* move check from memblock_search to memblock_is_memory
* modify changelog

When checking the indicated address belongs to the memory region, the 
memory 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 |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 4d9393c..258e81d 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -888,6 +888,11 @@ int __init memblock_is_reserved(phys_addr_t addr)
 
 int __init_memblock memblock_is_memory(phys_addr_t addr)
 {
+
+	if (unlikely(addr < memblock_start_of_DRAM() ||
+		addr >= memblock_end_of_DRAM()))
+		return 0;
+
 	return memblock_search(&memblock.memory, addr) != -1;
 }
 
-- 
1.7.5.4

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