linux-kernel - Re: [PATCH] sched: remove redundant check in select_task_rq

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Message-ID: <m3hb82aren.fsf@IBM-009124035060.in.ibm.com>
Date:	Tue, 07 Jun 2011 15:34:48 +0530
From:	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: remove redundant check in select_task_rq_fair

On Tue, 07 Jun 2011 11:53:34 +0200, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, 2011-06-07 at 15:18 +0530, Nikunj A. Dadhania wrote:
> > When balancing for wakeup affinity, a redundant check can removed.
> 
> Yes, tempting, but no, now you've got an extra call to wake_affine(),
> which is more expensive.
Ah, got that. How about this, it is more readable. Other options would
be to add a comment.

Signed-off-by: Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
---
 kernel/sched_fair.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 433491c..354e26b 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1753,7 +1753,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
 	}
 
 	if (affine_sd) {
-		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
+		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
 			prev_cpu = cpu;
--
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