linux-kernel - Re: On migrate_disable() and latencies

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Message-ID: <20110728055043.GA570@windriver.com>
Date:	Thu, 28 Jul 2011 13:50:43 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Carsten Emde <ce@...g.ch>,
	Clark Williams <williams@...hat.com>,
	Kumar Gala <galak@...e.crashing.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	rostedt <rostedt@...dmis.org>,
	Nicholas Mc Guire <der.herr@...r.at>
Subject: Re: On migrate_disable() and latencies

On Wed, Jul 27, 2011 at 11:30:08AM -0700, Paul E. McKenney wrote:
> o	Tasks awakening outside of migrate-disable regions will pick
> 	the CPU running the lowest-priority task, whether or not this
> 	task is in migrate-disable state.  (At least I don't see
> 	anything in 3.0-rt3 that looks like a scheduling decision
> 	based on ->migrate_disable, perhaps due to blindness.)

I'm also confused here, seems we just disable migration for RT task.
migrate_disable()
{
	...
		if (p->sched_class->set_cpus_allowed)
			p->sched_class->set_cpus_allowed(p, mask);
		p->rt.nr_cpus_allowed =	cpumask_weight(mask);
	...
}

Shouldn't we also forbid migration on !RT task?

Thanks,
Yong

-- 
Only stand for myself
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