linux-kernel - RE: [PATCH] cpuidle/drivers/mobile: Add new governor for mobile/embedded systems

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Date:   Sun, 7 Jul 2019 10:02:29 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Daniel Lezcano'" <daniel.lezcano@...aro.org>
Cc:     <linux-kernel@...r.kernel.org>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
        "'Thomas Gleixner'" <tglx@...utronix.de>,
        "'Greg Kroah-Hartman'" <gregkh@...uxfoundation.org>,
        "'open list:CPU IDLE TIME MANAGEMENT FRAMEWORK'" 
        <linux-pm@...r.kernel.org>, <rafael@...nel.org>
Subject: RE: [PATCH] cpuidle/drivers/mobile: Add new governor for mobile/embedded systems

On 2019.07.03 12:12 Doug Smythies wrote:
> On 2019.07.03 08:16 Daniel Lezcano wrote:
>> On 03/07/2019 16:23, Doug Smythies wrote:
>>> On 2019.06.20 04:58 Daniel Lezcano wrote:

> ...
>>> Anyway, I did a bunch of tests and such, but have deleted
>>> most from this e-mail, because it's just noise. I'll
>>> include just one set:
>>> 
>>> For a work load that would normally result in a lot of use
>>> of shallow idle states (single core pipe-test * 2 cores).
>>
>> Can you share the tests and the command lines?
>
> Yes, give me a few days to repeat the tests and write
> it up properly. I am leaving town in an hour and for a day.

O.K. I re-did the tests and made a new web page with, I think,
everything I used.

...

>> The governor can be better by selecting the shallow states, the
>> scheduler has to interact with the governor to give clues about the
>> load, that is identified and will be the next step.
>>
>> Is it possible to check with the schedutil governor instead?
>
> Oh, I already have some data, just didn't include it before:
>
> Idle governor, teo; CPU frequency scaling: intel-cpufreq/schedutil;
> Processor package power: 40.4 watts; 4.9 uSec/loop
>
> Idle governor, mobile; CPU frequency scaling: intel-cpufreq/schedutil;
> Processor package power: 12.7 watts; 19.7 uSec/loop
>
> Idle governor, teo; CPU frequency scaling: intel-cpufreq/schedutil;
> Idle states 0-3 disabled (note: Idle state 4 is the deepest on my system)
> Processor package power: 36.9 watts; 8.3 uSec/loop
> In my notes I wrote: "Huh?? I do not understand this result, as I had
> expected more similar to the mobile governor". But I did not investigate.

The reason for the big difference was/is that with the "mobile"
governor the CPU frequency never scales up for this test. It can be
sluggish to scale up with the teo and the menu governors, but always
eventually does. I also tried the acpi-cpufreq driver with similar results.

> Anyway, the schedutil test is the one I'll repeat and write up better.

New summary (similar to old):

governor 		usec/loop	watts
mobile		19.8		12.67
teo			4.87		40.28
menu			4.85		40.25
teo-idle-0-3-dis	8.30		36.85

Graphs, details and source codes:
http://www.smythies.com/~doug/linux/idle/mobile/index.html

... Doug