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Subject: Re: [PATCH v3 1/2] sched/fair: Introduce short duration task check
To:     Chen Yu <yu.c.chen@intel.com>
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From:   Yicong Yang <yangyicong@huawei.com>
Message-ID: <e0b20fe3-6528-41ca-f53f-d78e76cd122a@huawei.com>
Date:   Mon, 12 Dec 2022 19:22:48 +0800
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On 2022/12/7 22:24, Chen Yu wrote:
> Hi Josh,
> On 2022-12-06 at 18:23:47 -0800, Josh Don wrote:
>>> We don't want to add more dedicated knobs. So using
>>> sysctl_sched_min_granularity as you are doing in this patch looks ok
>>
>> If not a knob, then maybe at least a smaller hardcoded value? Several
>> milliseconds seems like too long for this optimization; the
>> opportunity cost of not doing the idle search likely doesn't make
>> sense if the waker is going to be active for several additional
>> milliseconds. I would have guessed something on the order of 100us.
>>
>> Chen, what is the run duration of tasks in your ping pong example?
> OK, I'll measure the duration of all the tests and summarize the data later.
> 

If we decide to use sysctl_sched_min_granularity as the threshold of a short
task, can we also export p->se.dur_avg (somewhere like /proc/[pid]/sched)?
It may be helpful to choose a proper value for sysctl_sched_min_granularity.

Thanks.