linux-kernel - Re: [Patch v6 1/7] sched/pelt.c: Add support to track thermal pressure

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Message-ID: <8a85f4c2-6ef8-314a-c56d-86c773d5ead0@arm.com>
Date:   Thu, 9 Jan 2020 13:24:23 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Quentin Perret <qperret@...gle.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Amit Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Amit Kucheria <amit.kucheria@...durent.com>
Subject: Re: [Patch v6 1/7] sched/pelt.c: Add support to track thermal
 pressure

On 08/01/2020 15:56, Thara Gopinath wrote:
> On Tue, 17 Dec 2019 at 07:54, Dietmar Eggemann <dietmar.eggemann@....com>
> wrote:
> 
>> On 12/12/2019 05:11, Thara Gopinath wrote:
>>
>> minor: in subject: s/sched/pelt.c/sched/pelt
>>
>> [...]
>>
>>> diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
>>> index a96db50..9aac3b7 100644
>>> --- a/kernel/sched/pelt.c
>>> +++ b/kernel/sched/pelt.c
>>> @@ -353,6 +353,28 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq,
>> int running)
>>>       return 0;
>>>  }
>>>
>>> +/*
>>> + * thermal:
>>> + *
>>> + *   load_sum = \Sum se->avg.load_sum
>>
>> Why not '\Sum rq->avg.load_sum' ?
>>
> Hi Dietmar,
> 
> The header for all other update_*_load_avg api use se->avg. and not rq->avg.

True but at least they (rt_rq, dl_rq, irq) also say 'but
se->avg.util_sum is not tracked'.

I guess this comment originally came from the
'__update_load_avg_blocked_se(), __update_load_avg_se(),
__update_load_avg_cfs_rq()' block:

* cfq_rq:
 *
 *   load_sum = \Sum se_weight(se) * se->avg.load_sum

but for rt_rq, dl_rq, irq and thermal we don't have a relationship like
between se and cfs_rq's so that's why this comment confuses me.