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

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Date:	Thu, 28 Jul 2011 15:10:15 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	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 Thu, Jul 28, 2011 at 09:01:23AM +0200, Thomas Gleixner wrote:
> We do. Just RT is the only sched class which has a set_cpus_allowed()
> callback implemented and want's an update to its rt.nr_cpus_allowed
> field.
> 
>        if (!p->migrate_disable) {
>                 if (p->sched_class && p->sched_class->set_cpus_allowed)
>                         p->sched_class->set_cpus_allowed(p, new_mask);
>                 p->rt.nr_cpus_allowed = cpumask_weight(new_mask);
>         }
> 
> The general part is here:
> 
>        cpumask_copy(&p->cpus_allowed, new_mask);
> 
> And tsk_cpus_allowed() does:
> {
>         if (p->migrate_disable)
>                 return cpumask_of(task_cpu(p));
> 
>         return &p->cpus_allowed;
> }

Hmmm, sched-use-task-allowed-accessor.patch is the preparation :)

Clear now, thanks Thomas.

-Yong

-- 
Only stand for myself
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