linux-kernel - Re: [patch] CFS scheduler, -v14

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Message-ID: <20070531095337.GA8104@elte.hu>
Date:	Thu, 31 May 2007 11:53:37 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Li Yu <raise.sail@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [patch] CFS scheduler, -v14


* Li Yu <raise.sail@...il.com> wrote:

> static void distribute_fair_add(struct rq *rq, s64 delta)
> {
>    struct task_struct *curr = rq->curr;
>    s64 delta_fair = 0;
> 
>    if (!(sysctl_sched_load_smoothing & 32))
>        return;
> 
>    if (rq->nr_running) {
>        delta_fair = div64_s(delta, rq->nr_running);
>        /*
>         * The currently running task's next wait_runtime value does
>         * not depend on the fair_clock, so fix it up explicitly:
>         */
>        add_wait_runtime(rq, curr, -delta_fair);
>        rq->fair_clock -= delta_fair;
>    }
> }
> 
> See this line:
> 
>        delta_fair = div64_s(delta, rq->nr_running);
> 
> Ingo, should we be replace "rq->nr_running" with "rq->raw_load_weight" 
> here?

that would break the code. The handling of sleep periods is basically 
heuristics and using nr_running here appears to be 'good enough' in 
practice.

	Ingo
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