DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:date:message-id:subject:from:to
         :cc:content-type;
        b=MTpoNX6y6G9rqiVUEP8Gnyv9WHW+nkqA3FJIcCIlcNQeaP2HcIkiIyjhVMsIQVMWV9
         Up6Rw/r6B885FHNlbMTUddbAONPv/7tRsTrMwfMJZDGPeQvWiIsSwla1UcttTD4lj9QU
         Hdch+2R7lpARxuhdGD5+Tmv7jJ+NS4jczm4Gc=
MIME-Version: 1.0
In-Reply-To: <BANLkTinzsjTy6yA7N-ssy5beyJn5NQZX3w@mail.gmail.com>
References: <BANLkTikkeR_yf1HGhgq7WEO-kEvDGkV_tw@mail.gmail.com>
	<BANLkTim4n-WA_6nJpg4Nd99yuc3f+VWkcw@mail.gmail.com>
	<BANLkTikOecxhb8pZfAd19FLrPAPY4zacDQ@mail.gmail.com>
	<20110512120606.GA3639@zhy>
	<20110518013842.GD23940@home.goodmis.org>
	<BANLkTikOW9t6F8jvTJ0uPvyYDy+mpXh-DA@mail.gmail.com>
	<BANLkTikMdAG4HFmhiB9c3x97FH0N3PnpHA@mail.gmail.com>
	<1305725044.26849.11.camel@gandalf.stny.rr.com>
	<BANLkTinzsjTy6yA7N-ssy5beyJn5NQZX3w@mail.gmail.com>
Date: Thu, 19 May 2011 09:41:27 +0800
Message-ID: <BANLkTim0SKAya-S_1h_zvS5rHW5ZOMG7Ow@mail.gmail.com>
Subject: Re: [PATCH] sched: correct how RT task is picked
From: Yong Zhang <yong.zhang0@gmail.com>
To: Hillf Danton <dhillf@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <peterz@infradead.org>,
        Mike Galbraith <efault@gmx.de>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1345
Lines: 41

On Wed, May 18, 2011 at 10:46 PM, Hillf Danton <dhillf@gmail.com> wrote:
> On Wed, May 18, 2011 at 9:24 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
>> On Wed, 2011-05-18 at 21:19 +0800, Hillf Danton wrote:
>>
>>> Hi all
>>>
>>> The patch is prepared again, in which tests for both cpu and
>>> nr_cpus_allowed are dropped.
>>>
>>> The reason to drop nr_cpus_allowed is to make sure that the
>>> returned value is correct for both case that cpu == rq->cpu and
>>> case that cpu != rq->cpu.
>>
>> -ENOPARSE
>>
>> Why would we pick a task that can't migrate?
>>
> Hi Steven
>
> For migration, it is the case that cpu != rq->cpu, and
> if cpu is allowed by task's affinity, it is bug that task
> could not goto cpu because of nr_cpus_allowed since
> the nr_cpus_allowed is computed based on the cpus_allowed mask.

But for next_prio(), we just calculate the next highest migratible task
for a rq regardless on which cpu that task will run, say we let cpu=rq->cpu
to be second parameter of pick_next_highest_task_rt(), IOW, it has
the same effect as cpu = -1

Thanks,
Yong


-- 
Only stand for myself
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/