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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2013-09-10 15:54:49 +0900
committerIngo Molnar <mingo@kernel.org>2013-09-10 09:20:42 +0200
commitb0cff9d88ce2f3030f73138078c5b1019f17e1cc (patch)
treec99ab79be7b17494f22a66207bfc19e572a3dc17 /kernel
parent816434ec4a674fcdb3c2221a6dffdc8f34020550 (diff)
downloadlwn-b0cff9d88ce2f3030f73138078c5b1019f17e1cc.tar.gz
lwn-b0cff9d88ce2f3030f73138078c5b1019f17e1cc.zip
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 <dchinner@redhat.com> Tested-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Paul Turner <pjt@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Link: http://lkml.kernel.org/r/20130910065448.GA20368@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/fair.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7f0a5e6cdae0..9b3fe1cd8f40 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;
}
/*