linux-kernel - Re: [RFC PATCH v3 3/6] sched: pack small tasks

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Message-ID: <1364300782.5053.6.camel@laptop>
Date:	Tue, 26 Mar 2013 13:26:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, mingo@...nel.org,
	linux@....linux.org.uk, pjt@...gle.com, santosh.shilimkar@...com,
	morten.rasmussen@....com, chander.kashyap@...aro.org,
	cmetcalf@...era.com, tony.luck@...el.com, alex.shi@...el.com,
	preeti@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com,
	tglx@...utronix.de, len.brown@...el.com, arjan@...ux.intel.com,
	amit.kucheria@...aro.org, corbet@....net
Subject: Re: [RFC PATCH v3 3/6] sched: pack small tasks

On Fri, 2013-03-22 at 13:25 +0100, Vincent Guittot wrote:
> +static bool is_buddy_busy(int cpu)
> +{
> +       struct rq *rq = cpu_rq(cpu);
> +
> +       /*
> +        * A busy buddy is a CPU with a high load or a small load with
> a lot of
> +        * running tasks.
> +        */
> +       return (rq->avg.runnable_avg_sum >
> +                       (rq->avg.runnable_avg_period / (rq->nr_running
> + 2)));
> +}

Why does the comment talk about load but we don't see it in the
equation. Also, why does nr_running matter at all? I thought we'd
simply bother with utilization, if fully utilized we're done etc..

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