linux-kernel - Re: [RFD] Add debugfs for cpuidle ?

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Date:   Thu, 30 Aug 2018 10:24:53 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [RFD] Add debugfs for cpuidle ?

On 30/08/2018 10:22, Ulf Hansson wrote:
> On 24 May 2018 at 10:47, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>> On 24/05/2018 10:28, Rafael J. Wysocki wrote:
>>> On Thursday, May 24, 2018 10:14:31 AM CEST Daniel Lezcano wrote:
>>>>
>>>> Hi all,
>>>
>>> Hi,
>>>
>>>> would it be interesting to add debugfs metrics for cpuidle in order
>>>> to read some statistics from there and investigate the behavior ?
>>>
>>> What exactly would you like to see in there?
>>
>> It could be interesting to have statistics on a per cpu and global basis
>> for:
>>
>> - prediction accuracy:
>>
>> /sys/kernel/debug/cpuidle/prediction/[good|over|under]
>> /sys/kernel/debug/cpuidle/cpu*/state*/prediction/[good|over|under]
>>
>>  - exit latency
>>
>> In addition, it is often the case the idle states values are dropped
>> randomly, it is interesting to see the average exit latency for the
>> states. That could give also an indication the cluster idle state success.
>>
>> /sys/kernel/debug/cpuidle/state*/latency/[min|max|avg|stddev]
>> /sys/kernel/debug/cpuidle/cpu*/state*/prediction/[min|max|avg|stddev]
>>
>> And perhaps more information like the tick stopped stat ?
>>
> 
> Daniel,
> 
> Any chance that you have some draft version of actual code implementing this?
> 
> I would be very interested to try then - or help out to implement
> this, in case you haven't started yet.

Yes, I have a draft version, a bit incomplete but easy to fill. I'm just
not fully convinced about the metrics we need yet.


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