linux-kernel - Re: [patch v8 4/9] sched: fix slept time double counting in enqueue entity

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Message-ID: <51C3BCE1.1080405@gmail.com>
Date:	Fri, 21 Jun 2013 10:39:29 +0800
From:	Alex Shi <seakeel@...il.com>
To:	Lei Wen <adrian.wenl@...il.com>
CC:	Paul Turner <pjt@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	Jason Low <jason.low2@...com>,
	Changlong Xie <changlongx.xie@...el.com>, sgruszka@...hat.com,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [patch v8 4/9] sched: fix slept time double counting in enqueue
 entity

On 06/21/2013 10:30 AM, Lei Wen wrote:
> Hi Alex,
> 
> On Thu, Jun 20, 2013 at 10:59 PM, Alex Shi <seakeel@...il.com> wrote:
>> On 06/20/2013 10:46 AM, Lei Wen wrote:
>>>
>>>
>>> But here I have a question, there is another usage of __synchronzie_entity_decay
>>> in current kernel, in the switched_from_fair function.
>>>
>>> If task being frequently switched between rt and fair class, would it
>>> also bring the
>>> redundant issue? Do we need patch like below?
>>>
>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>> index b5408e1..9640c66 100644
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -5856,7 +5856,7 @@ static void switched_from_fair(struct rq *rq,
>>> struct task_struct *p)
>>>         */
>>>         if (p->se.avg.decay_count) {
>>>                 struct cfs_rq *cfs_rq = cfs_rq_of(&p->se);
>>> -               se->avg.last_runnable_update +=
>>> +               p->se.avg.last_runnable_update +=
>>
>> what tree does this patch base on?
> 
> I create the patch based on v3.9 kernel.
> If it is ok, I could create a formal one based on latest kernel.

In the linus tree, the first commit which introduced
__synchronize_entity_decay(&p->se) here is
9ee474f55664ff63111c843099d365e7ecffb56f
+
+#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
+       /*
+       * Remove our load from contribution when we leave sched_fair
+       * and ensure we don't carry in an old decay_count if we
+       * switch back.
+       */
+       if (p->se.avg.decay_count) {
+               struct cfs_rq *cfs_rq = cfs_rq_of(&p->se);
+               __synchronize_entity_decay(&p->se);
+               subtract_blocked_load_contrib(cfs_rq,
+                               p->se.avg.load_avg_contrib);
+       }
+#endif
 }

And it is never changed from then on. So your code must based on a
incorrect kernel. please do a double check.
> 
> Thanks,
> Lei
> 
>>>                                 __synchronize_entity_decay(&p->se);
>>>                 subtract_blocked_load_contrib(cfs_rq,
>>>                                 p->se.avg.load_avg_contrib);
>>
>>
>> --
>> Thanks
>>     Alex


-- 
Thanks
    Alex
--
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