linux-kernel - [PATCH 1/3] percpu: stop the loop when a cpu belongs to a new group

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Date:	Mon, 21 Oct 2013 16:58:11 +0800
From:	Wei Yang <weiyang@...ux.vnet.ibm.com>
To:	tj@...nel.org, cl@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc:	weiyang@...ux.vnet.ibm.com
Subject: [PATCH 1/3] percpu: stop the loop when a cpu belongs to a new group

When a cpu belongs to a new group, there is no cpu has the same group id. This
means it can be assigned a new group id without checking with every others.

This patch does this optimiztion.

Signed-off-by: Wei Yang <weiyang@...ux.vnet.ibm.com>
---
 mm/percpu.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 8c8e08f..536ca4f 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1488,7 +1488,10 @@ static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
 			    (cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
 			     cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
 				group++;
-				nr_groups = max(nr_groups, group + 1);
+				if (group == nr_groups) {
+					nr_groups++;
+					break;
+				}
 				goto next_group;
 			}
 		}
-- 
1.7.5.4

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