From: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Date: Wed, 26 Sep 2012 01:33:47 +0000 (+1000)
Subject: mm/memblock: reduce overhead in binary search
X-Git-Tag: next-20120926~2^2~248
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ecfef4cbb88b062fb1d40b5e69db4796bc87627b;p=karo-tx-linux.git

mm/memblock: reduce overhead in binary search

When checking that the indicated address belongs to the memory region, the
memory regions are checked one by one through a binary search, which will
be time consuming.

If the indicated address isn't in the memory region, then we needn't do
the time-consuming search.  Add a check on the indicated address for that
purpose.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/memblock.c b/mm/memblock.c
index 82aa349d2f7a..d48985e533eb 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;
 }