linux-kernel - Re: [PATCH v4 3/5] sched/fair: Skip detach sched avgs for new task when changing task groups

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Date:	Mon, 6 Jun 2016 11:58:40 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org, bsegall@...gle.com,
	pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com
Subject: Re: [PATCH v4 3/5] sched/fair: Skip detach sched avgs for new task
 when changing task groups

On Mon, Jun 06, 2016 at 08:20:39AM +0800, Yuyang Du wrote:
> +static void task_move_group_fair(struct task_struct *p, bool fork)
>  {
> -	detach_task_cfs_rq(p);
> +	/*
> +	 * Newly forked task should not be removed from any cfs_rq

That's a pointless comment; that's exactly what the code _does_.
Comments should explain the code, not restate it.

So a comment like:

	 * Newly forked tasks are not attached yet.

Is entirely more useful.

> +	 */
> +	if (!fork)
> +		detach_task_cfs_rq(p);
>  	set_task_rq(p, task_cpu(p));
>  	attach_task_cfs_rq(p);
>  	/*