Commit-ID: b0cff9d88ce2f3030f73138078c5b1019f17e1cc
Gitweb: http://git.kernel.org/tip/b0cff9d88ce2f3030f73138078c5b1019f17e1cc
Author: Joonsoo Kim <iamjoonsoo....@lge.com>
AuthorDate: Tue, 10 Sep 2013 15:54:49 +0900
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Tue, 10 Sep 2013 09:20:42 +0200
sched: Fix load balancing performance regression in should_we_balance()
Commit 23f0d20 ("sched: Factor out code to should_we_balance()")
introduces the should_we_balance() function. This function should
return 1 if this cpu is appropriate for balancing. But the newly
introduced code doesn't do so, it returns 0 instead of 1.
This introduces performance regression, reported by Dave Chinner:
v4 filesystem v5 filesystem
3.11+xfsdev: 220k files/s 225k files/s
3.12-git 180k files/s 185k files/s
3.12-git-revert 245k files/s 247k files/s
You can find more detailed information at:
https://lkml.org/lkml/2013/9/10/1
This patch corrects the return value of should_we_balance()
function as orignally intended.
With this patch, Dave Chinner reports that the regression is gone:
v4 filesystem v5 filesystem
3.11+xfsdev: 220k files/s 225k files/s
3.12-git 180k files/s 185k files/s
3.12-git-revert 245k files/s 247k files/s
3.12-git-fix 249k files/s 248k files/s
Reported-by: Dave Chinner <dchin...@redhat.com>
Tested-by: Dave Chinner <dchin...@redhat.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
Cc: Paul Turner <p...@google.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Dave Chinner <da...@fromorbit.com>
Link: http://lkml.kernel.org/r/20130910065448.ga20...@lge.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7f0a5e6..9b3fe1c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5151,7 +5151,7 @@ static int should_we_balance(struct lb_env *env)
* First idle cpu or the first cpu(busiest) in this sched group
* is eligible for doing load balancing at this and above domains.
*/
- return balance_cpu != env->dst_cpu;
+ return balance_cpu == env->dst_cpu;
}
/*
--
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