linux-kernel - RE: [RFC/RFT][PATCH v3 0/6] sched/cpuidle: Idle loop rework

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Date:   Sun, 11 Mar 2018 16:02:14 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Rafael J. Wysocki'" <rjw@...ysocki.net>
Cc:     "'Rik van Riel'" <riel@...riel.com>,
        "'Mike Galbraith'" <mgalbraith@...e.de>,
        "'Thomas Gleixner'" <tglx@...utronix.de>,
        "'Paul McKenney'" <paulmck@...ux.vnet.ibm.com>,
        "'Thomas Ilsche'" <thomas.ilsche@...dresden.de>,
        "'Frederic Weisbecker'" <fweisbec@...il.com>,
        "'Linux PM'" <linux-pm@...r.kernel.org>,
        "'Aubrey Li'" <aubrey.li@...ux.intel.com>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Doug Smythies'" <dsmythies@...us.net>
Subject: RE: [RFC/RFT][PATCH v3 0/6] sched/cpuidle: Idle loop rework

On 2018.03.11 08:52 Doug Smythies wrote:
> On 2018.03.11 03:22 Rafael J. Wysocki wrote:
>> On Sunday, March 11, 2018 8:43:02 AM CET Doug Smythies wrote:
>>> On 2018.03.10 15:55 Rafael J. Wysocki wrote: 
>>>> On Saturday, March 10, 2018 5:07:36 PM CET Doug Smythies wrote:
>>>>> On 2018.03.10 01:00 Rafael J. Wysocki wrote:
>>>
>>> ... [snip] ...
>>> 
>>>> The information that they often spend more time than a tick
>>>> period in state 0 in one go *is* relevant, though.
>>>>
>>>>
>>>> That issue can be dealt with in a couple of ways and the patch below is a
>>>> rather straightforward attempt to do that.  The idea, basically, is to discard
>>>> the result of governor prediction if the tick has been stopped alread and
>>>> the predicted idle duration is within the tick range.
>>>
>>>> Please try it on top of the v3 and tell me if you see an improvement.
>>> 
>>> It seems pretty good so far.
>>> See a new line added to the previous graph, "rjwv3plus".
>>> 
>>> http://fast.smythies.com/rjwv3plus_100.png
>>
>> OK, cool!
>>
>> Below is a respin of the last patch which also prevents shallow states from
>> being chosen due to interactivity_req when the tick is stopped.
>>
>> You may also add a poll_idle() fix I've just posted:
>>
>> https://patchwork.kernel.org/patch/10274595/
>>
>> on top of this.  It makes quite a bit of a difference for me. :-)
>
> I will add and test, but I already know from testing previous versions
> of this patch, from Rik van Riel and myself, that the results will be
> awesome.

And the results are indeed awesome.

A four hour 100% load on one CPU test was run, with trace, however
there is nothing to report, as everything is great.

The same graph as the last couple of days, with a new line added for
V3 + the respin of patch 7 of 6 + the poll-idle fix, called rjwv3pp,
is here:

http://fast.smythies.com/rjwv3pp_100.png

... Doug