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SubjectRe: [PATCH] sched: fix lose fair sleeper bonus in switch_to_fair()
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On 9/8/15 4:38 PM, Wanpeng Li wrote:
> On 9/8/15 4:22 PM, Byungchul Park wrote:
>> On Tue, Sep 08, 2015 at 04:04:49PM +0800, Wanpeng Li wrote:
>>>>> However, if se->vruntime -= cfs_rq->min_vruntime is positive, the
>>>>> behavior is different after your patch. e.g. se->vruntime(the
>>>>> relative vruntime in switched_to_fair()) < min_vruntime -
>>>>> sysctl_sched_latency/2
>>>>>
>>>>> before your patch:
>>>>>
>>>>> se->vruntime = min_vruntime - sysctl_sched_latency/2 (place_entity())
>>>> my patch is based on ff277d4 commit at tip/sched/core.
>>>>
>>>> there's no change between before and after.
>>>>
>>>> check it please.
>>>>
>>>> and this logic seems to be no problem to me. :(
>>> Your logic will lose fair sleeper bonus in the scenario which I
>>> pointed out.
>> i mean in ff277d4 commit:
>
> Please include the commit subject when you point out a commit, do you
> mean this one?
>
> commit ff277d4250fe715b6666219b1a3423b863418794
> Author: Andrea Parri <parri.andrea@gmail.com>
> Date: Wed Aug 5 15:56:19 2015 +0200
>
> sched/deadline: Fix comment in enqueue_task_dl()
>
> The "dl_boosted" flag is set by comparing *absolute* deadlines
> (c.f., rt_mutex_setprio()).
>
>
> What's the relationship w/ this patch?

I think you mean your commit:

commit 7855a35ac07a350e2cd26f09568a6d8e372be358
Author: Byungchul Park <byungchul.park@lge.com>
Date: Mon Aug 10 18:02:55 2015 +0900

sched: Ensure a task has a non-normalized vruntime when returning
back to CFS


However, that is wrong in the scenario which I mentioned.

Regards,
Wanpeng Li


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