Message-ID: <1392975715.5451.118.camel@marge.simpson.net>
Subject: Re: [PATCH v3] sched: keep quiescent cpu out of idle balance loop
From: Mike Galbraith <bitbucket@online.de>
To: Lei Wen <leiwen@marvell.com>
Cc: Peter Zijlstra <peterz@infradead.org>, mingo@redhat.com,
        preeti.lkml@gmail.com, daniel.lezcano@linaro.org,
        viresh.kumar@linaro.org, xjian@marvell.com,
        linux-kernel@vger.kernel.org
Date: Fri, 21 Feb 2014 10:41:55 +0100
In-Reply-To: <1392974108-28778-1-git-send-email-leiwen@marvell.com>
References: <1392971691.5451.84.camel@marge.simpson.net>
	 <1392974108-28778-1-git-send-email-leiwen@marvell.com>
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On Fri, 2014-02-21 at 17:15 +0800, Lei Wen wrote:

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 235cfa7..af30b6a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6883,6 +6883,14 @@ void nohz_balance_enter_idle(int cpu)
>  	if (!cpu_active(cpu))
>  		return;
>  
> +	/*
> +	 * If this cpu is isolated, its rq's sd member would becomes NULL.
> +	 * Base on this observation, we could exclude this cpu from nohz
> +	 * idle balance, so that it would not be disturbed.
> +	 */
> +	if (!this_rq()->sd)
> +		return;
> +
>  	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
>  		return;

What about nohz_balance_exit_idle()?

I think Peter queued a patchlet to tell nohz balancing to go away.

-Mike

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