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Date: Wed, 10 Oct 2018 13:08:22 -0400
From: Thara Gopinath <thara.gopinath@...aro.org>
To: Juri Lelli <juri.lelli@...il.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Cc: Quentin Perret <quentin.perret@....com>,
Ingo Molnar <mingo@...nel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Zhang Rui <rui.zhang@...el.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Amit Kachhap <amit.kachhap@...il.com>,
viresh kumar <viresh.kumar@...aro.org>,
Javi Merino <javi.merino@...nel.org>,
Eduardo Valentin <edubezval@...il.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
"open list:THERMAL" <linux-pm@...r.kernel.org>,
Ionela Voinescu <ionela.voinescu@....com>
Subject: Re: [RFC PATCH 0/7] Introduce thermal pressure
On 10/10/2018 09:34 AM, Juri Lelli wrote:
> On 10/10/18 15:08, Vincent Guittot wrote:
>> On Wed, 10 Oct 2018 at 14:50, Juri Lelli <juri.lelli@...il.com> wrote:
>>>
>>> On 10/10/18 14:34, Vincent Guittot wrote:
>>>> Hi Juri,
>>>>
>>>> On Wed, 10 Oct 2018 at 14:23, Juri Lelli <juri.lelli@...il.com> wrote:
>>>>>
>>>>> On 10/10/18 14:04, Vincent Guittot wrote:
>>>>>
>>>>> [...]
>>>>>
>>>>>> The problem was the same with RT, the cfs utilization was lower than
>>>>>> reality because RT steals soem cycle to CFS
>>>>>> So schedutil was selecting a lower frequency when cfs was running
>>>>>> whereas the CPU was fully used.
>>>>>> The same can happen with thermal:
>>>>>> cap the max freq because of thermal
>>>>>> the utilization with decrease.
>>>>>> remove the cap
>>>>>> the utilization is still low and you will select a low OPP because you
>>>>>> don't take into account cycle stolen by thermal like with RT
>>>>>
>>>>> What if we scale frequency component considering the capped temporary
>>>>> max?
>>>>
>>>> Do you mean using a kind of scale_thermal_capacity in accumulate_sum
>>>> when computing utilization ?
>>>
>>> Yeah, something like that I guess. So that we account for temporary
>>> "fake" 1024..
>>
>> But the utilization will not be invariant anymore across the system
>
> Mmm, I guess I might be wrong, but I was thinking we should be able to
> deal with this similarly to what we do with cpus with different max
> capacities. So, another factor? Because then, how do we handle other
> ways in which max freq can be restricted (e.g. from userspace as Javi
> was also mentioning)?
IMHO, user-space restrictions should be handled separately. It should
probably reflect as an update of capacity_orig and rebuilding of
scheduler structures as such a restriction is meant to stay for a long
duration.
Regards
Thara
>
--
Regards
Thara
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