linux-kernel - Re: [PATCH][mmotm] Sched fix stale value in average load per task

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Message-ID: <20081112113514.GB6372@elte.hu>
Date:	Wed, 12 Nov 2008 12:35:14 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Vaidyanathan S <svaidyan@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>
Subject: Re: [PATCH][mmotm] Sched fix stale value in average load per task


* Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> cpu_avg_load_per_task() returns a stale value when nr_running is 0. 
> It returns an older stale (caculated when nr_running was non zero) 
> value. This patch returns and sets rq->avg_load_per_task to zero 
> when nr_running is 0.
> 
> Compile and boot tested on a x86_64 box.
> 
> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
> ---
> 
>  kernel/sched.c |    2 ++
>  1 file changed, 2 insertions(+)

applied to tip/sched/urgent, thanks Balbir!

i'm wondering, have you observed load-balancer misbehavior due to this 
load-average imprecision bug, on some workload? (or have you found 
this via code review)

	Ingo
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