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