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Subject: Re: [RFC 0/3] Introduce per-task latency_tolerance for scheduler
 hints
To:     Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org,
        patrick.bellasi@matbug.net, qais.yousef@arm.com, pavel@ucw.cz,
        dhaval.giani@oracle.com, qperret@qperret.net,
        David.Laight@ACULAB.COM, morten.rasmussen@arm.com, pjt@google.com,
        tj@kernel.org, viresh.kumar@linaro.org, rafael.j.wysocki@intel.com,
        daniel.lezcano@linaro.org
References: <20191125094618.30298-1-parth@linux.ibm.com>
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 <c26f7909-0e4e-a897-bf84-0aa9e5389a0d@arm.com>
 <838f233e-fa4c-d5a3-9b50-69e2e121edda@arm.com>
From:   Parth Shah <parth@linux.ibm.com>
Date:   Thu, 5 Dec 2019 22:43:44 +0530
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On 12/5/19 7:33 PM, Dietmar Eggemann wrote:
> On 05/12/2019 11:49, Valentin Schneider wrote:
>>  
>> On 05/12/2019 09:24, Dietmar Eggemann wrote:
>>> On 25/11/2019 10:46, Parth Shah wrote:
>>>> This patch series is based on the discussion started as the "Usecases for
>>>> the per-task latency-nice attribute"[1]
>>>>
>>>> This patch series introduces a new per-task attribute latency_tolerance to
>>>> provide the scheduler hints about the latency requirements of the task.
>>>
>>> I forgot but is there a chance to have this as a per-taskgroup attribute
>>> as well?
>>>
>>
>> Peter argued we should go for task attributes first, and then
>> cgroup/taskgroups later on:
>>
>> https://lore.kernel.org/lkml/20190905083127.GA2332@hirez.programming.kicks-ass.net/
> 
> OK, I went through this thread again. So Google or we have to provide
> the missing per-taskgroup API via cpu controller's attributes (like for
> uclamp) for the EAS usecase.

I suppose many others (including myself) will also be interested in having
per-taskgroup attribute via CPU controller.

> 
> After reading:
> 
> https://lore.kernel.org/r/20190905114030.GL2349@hirez.programming.kicks-ass.net
> 
> IMHO the following mapping of the existing Android (binary)
> latency_sensitive per-taskgroup flag makes sense:
> 
> latency_sensitive=1 -> latency_tolerance*[-20 .. -1] (less tolerant,
> more sensitive)
> 
> latency_sensitive=0 -> latency_tolerance[0 .. 19] (more tolerant, less
> sensitive)
> 
> Default value is 0 so not latency_sensitive.
> 
> * Since we use [-20 .. 19] as values for latency_tolerance we could name
> it latency_nice. It's shorter ... ?

I kept choosing appropriate name and possible values for this new attribute
in the separate thread. https://lkml.org/lkml/2019/9/30/215
From which discussion, looking at Patrick's comment
https://lkml.org/lkml/2019/9/18/678 I thought of picking latency_tolerance
as the appropriate name.
Still will be happy to change as per the community needs.

Thanks,
parth