linux-kernel - Re: [PATCH v4] sched: fix wrong rq's runnable

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Date:	Wed, 10 Apr 2013 09:26:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Ingo Molnar <mingo@...nel.org>, Paul Turner <pjt@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH v4] sched: fix wrong rq's runnable_avg update with rt
 tasks

On Tue, 2013-04-09 at 11:06 +0200, Vincent Guittot wrote:
> >> +void idle_enter(struct rq *this_rq)
> >> +{
> >> +       update_rq_runnable_avg(this_rq, 1);
> >> +}

> >> +void idle_exit(struct rq *this_rq)
> >> +{
> >> +       update_rq_runnable_avg(this_rq, 0);
> >> +}
> >
> > These seem like fairly unfortunate names to expose to the global
> > namespace, why not expose update_rq_runnable_avg() instead?
> 
> Just to gather in one place all cfs actions that should be done when
> exiting idle even if we only have update_rq_runnable_avg right now. I
> have distinguished that from idle_balance because this sequence can't
> generate extra context switch like idle_balance and they would finally
> not be called in the same time

OK, but could we then please give then more scheduler specific names?
It just seems to me that idle_enter/idle_exit() are very obvious
function names for unrelated things.

How about calling it idle_{enter,exit}_fair; so that once other classes
grow hooks we can do something like:

static void pre_schedule_idle(struct rq *rq, struct task_struct *p)
{
	struct sched_class *class;

	for_each_class(class) {
		if (class->idle_enter)
			class->idle_enter(rq);
	}	
}

or whatnot..

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