Messages in this thread Patch in this message | | | Date | Tue, 10 Sep 2013 00:25:06 -0700 | From | tip-bot for Joonsoo Kim <> | Subject | [tip:sched/urgent] sched: Fix load balancing performance regression in should_we_balance() |
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Commit-ID: b0cff9d88ce2f3030f73138078c5b1019f17e1cc Gitweb: http://git.kernel.org/tip/b0cff9d88ce2f3030f73138078c5b1019f17e1cc Author: Joonsoo Kim <iamjoonsoo.kim@lge.com> AuthorDate: Tue, 10 Sep 2013 15:54:49 +0900 Committer: Ingo Molnar <mingo@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 <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> --- 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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