linux-kernel - Re: Tasks schedule/migration issue with CPU hotplug?

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Message-ID: <CAOwKts9kJGYke6xA6zrQ=h6T7KMAz6uruxC37+PCskNwn6iK2A@mail.gmail.com>
Date:	Thu, 15 Sep 2011 10:38:02 +0800
From:	TAO HU <tghk48@...orola.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, peterz@...radead.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-omap <linux-omap@...r.kernel.org>
Subject: Re: Tasks schedule/migration issue with CPU hotplug?

Hi, Yong

You're right. We figured out something is wrong (is negative) with
vruntime of certain processes.
Below link describes the same issue we observed.
http://lkml.indiana.edu/hypermail/linux/kernel/1101.2/00333.html

And the commite indicated by you is exactly the fix.

Appreciate it!.

On Thu, Sep 8, 2011 at 3:39 PM, Yong Zhang <yong.zhang0@...il.com> wrote:
> On Thu, Sep 08, 2011 at 03:28:01PM +0800, Yong Zhang wrote:
>> On Thu, Sep 08, 2011 at 02:47:08PM +0800, TAO HU wrote:
>> > Resend with linux-kernel mail list included.
>>
>> Hmm, could you give a try with commit da7a735e?
>>
>> Thanks,
>> Yong
>>
>> ---
>> commit da7a735e51f9622eb3e1672594d4a41da01d7e4f
>> Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Date:   Mon Jan 17 17:03:27 2011 +0100
>>
>>     sched: Fix switch_from_fair()
>>
>>     When a task is taken out of the fair class we must ensure the vruntime
>>     is properly normalized because when we put it back in it will assume
>>     to be normalized.
>>
>>     The case that goes wrong is when changing away from the fair class
>>     while sleeping. Sleeping tasks have non-normalized vruntime in order
>>     to make sleeper-fairness work. So treat the switch away from fair as a
>>     wakeup and preserve the relative vruntime.
>>
>>     Also update sysrq-n to call the ->switch_{to,from} methods.
>>
>>     Reported-by: Onkalo Samu <samu.p.onkalo@...ia.com>
>>     Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>>     LKML-Reference: <new-submission>
>>     Signed-off-by: Ingo Molnar <mingo@...e.hu>
>>
>> >
>> > On Wed, Sep 7, 2011 at 10:22 PM, TAO HU <tghk48@...orola.com> wrote:
>> > > <4>[ 6950.136230] cfs_rq[0]:/
>> > > <4>[ 6950.136230] ? .exec_clock ? ? ? ? ? ? ? ? ? ?: 6520265.283900
>> > > <4>[ 6950.136260] ? .MIN_vruntime ? ? ? ? ? ? ? ? ?: 2223057.428522
>> > > <4>[ 6950.136260] ? .min_vruntime ? ? ? ? ? ? ? ? ?: 2223057.428522
>> > > <4>[ 6950.136291] ? .max_vruntime ? ? ? ? ? ? ? ? ?: 2223114.709956
>> > > <4>[ 6950.136291] ? .spread ? ? ? ? ? ? ? ? ? ? ? ?: 57.281434
>> > > <4>[ 6950.136291] ? .spread0 ? ? ? ? ? ? ? ? ? ? ? : 0.000000
>> > > <4>[ 6950.136322] ? .nr_running ? ? ? ? ? ? ? ? ? ?: 212
>> > > <4>[ 6950.136322] ? .load ? ? ? ? ? ? ? ? ? ? ? ? ?: 217650
>> > > <4>[ 6950.136352] ? .nr_spread_over ? ? ? ? ? ? ? ?: 125034
>> > > <4>[ 6950.136352] ? .shares ? ? ? ? ? ? ? ? ? ? ? ?: 0
>> > > <4>[ 6950.136352]
>> > > <4>[ 6950.136566] runnable tasks:
>> > > <4>[ 6950.136566] ? ? ? ? ? ? task ? PID ? ? ? ? tree-key ?switches
>> > > prio ? ? exec-runtime ? ? ? ? sum-exec ? ? ? ?sum-sleep
>> > > <4>[ 6950.136596]
>> > > ----------------------------------------------------------------------------------------------------------
>> > > <4>[ 6950.136627] ? ? ?omap2_mcspi ? ?21 ? 2223062.886210 ?29451523
>
> The tree-key(2223062.886210) almost equals to cfs_rq.min_vruntime,
> so maybe you hit the bug which is cured by the mentioned commit.
>
> Thanks,
> Yong
>



-- 
Best Regards
Hu Tao
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