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

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Date:   Thu, 24 May 2018 10:47:54 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     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 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 ?



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