linux-kernel - RE: [PATCH v2] cpuidle: Use nanoseconds as the unit of time

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Date:   Fri, 8 Nov 2019 09:04:33 -0800
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Rafael J. Wysocki'" <rafael@...nel.org>
Cc:     "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Daniel Lezcano'" <daniel.lezcano@...aro.org>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Giovanni Gherdovich'" <ggherdovich@...e.cz>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
        "'Linux PM'" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH v2] cpuidle: Use nanoseconds as the unit of time

On 2019.11.08 01:45 Rafael J. Wysocki wrote:
> On Fri, Nov 8, 2019 at 9:45 AM Doug Smythies <dsmythies@...us.net> wrote:
>
...
>> I have been running this v2 today, with both menu and teo
>> governors. Acquiring some baseline reference data to compare
>> to now. The menu governor response seems different (Supporting
>> information/graphs will come later).
>
> That may be good or bad, depending in what way it is different. :-)

My thinking was that the differences should be minimal between
the baseline (linux-next as of 2019.11.07) and plus your two patches.
Because this was a change of units, but not functionality.
Such is the case with the teo governor, but not the menu governor.
I have not tried the ladder or haltpoll governors, and don't intend to.

Now to attempt to isolate the issue in the code, which might take
considerable time.

The test in question was that sweep one developed during the
powernightmare stuff. It is a crude attempt to sweep through
a preference for all idle states. While not a great test, who cares
if it reveals something.

Reference:
http://www.smythies.com/~doug/linux/idle/nano-second-conversion/sweep/index.html

Legend:
teo-base : linux-next 2019.11.07
menu-base: linux-next 2019.11.07
teo-v2   : linux-next 2019.11.07 + cpuidle: Consolidate disabled state checks + this v2
menu-v2  : linux-next 2019.11.07 + cpuidle: Consolidate disabled state checks + this v2

Note: I only tossed the graphs there, without a way to navigate to the location
from the parent web pages.

... Doug