linux-kernel - Re: [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking

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Date:   Mon, 31 Oct 2016 08:07:46 -0700
From:   Vikram Mulukutla <markivx@...eaurora.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Steve Muckle <steve.muckle@...aro.org>,
        Olav Haugan <ohaugan@...eaurora.org>,
        Syed Rameez Mustafa <rameezmustafa@...eaurora.org>,
        Joonwoo Park <joonwoop@...eaurora.org>,
        Pavankumar Kondeti <pkondeti@...eaurora.org>,
        Saravana Kannan <skannan@...eaurora.org>,
        Bryan Huntsman <bryanh@...eaurora.org>,
        Juri Lelli <juri.lelli@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Chris Redpath <chris.redpath@....com>,
        Robin Randhawa <robin.randhawa@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Todd Kjos <tkjos@...gle.com>,
        Srinath Sridharan <srinathsr@...gle.com>,
        Andres Oportus <andresoportus@...gle.com>,
        Leo Yan <leo.yan@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Vikram Mulukutla <markivx@...eauorora.org>
Subject: Re: [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking

On 2016-10-28 01:49, Peter Zijlstra wrote:
> On Fri, Oct 28, 2016 at 12:57:05AM -0700, Vikram Mulukutla wrote:
>> On 2016-10-28 00:49, Peter Zijlstra wrote:
>> >On Fri, Oct 28, 2016 at 12:10:39AM -0700, Vikram Mulukutla wrote:
>> >>This RFC patch has been tested on live X86 machines with the following
>> >>sanity
>> >>and benchmark results (thanks to Juri Lelli, Dietmar Eggeman, Patrick
>> >>Bellasi
>> >>for initial code reviews):
>> >>
>> >>(Tested on an Intel i7 2nd generation CPU, 8GB RAM, Nvidia GTX950Ti
>> >>graphics,
>> >>with the same frequency list as above. Running Ubuntu 16.04 on a v4.8.2
>> >>baseline. WALT window size was 10ms. Only deltas above 3% are considered
>> >>non-noise.Power measured with Intel RAPL counters)
>> >
>> >Was this comparison done using the use_walt_metric sysctl knob?
>> 
>> Yes, it was. You will want to see numbers against a pure 4.8.2 without 
>> any
>> of the WALT code, correct?
> 
> Yep, because with the sysctl we still run all the accounting code. So
> esp things like the hackbench run are meaningless (note that even the
> CONFIG thing doesn't take out everything).
> 
> Also, I think it makes sense to always (also) compare against the
> "performance" governor. That way you can see the drop in absolute
> performance etc..

Ok, here are some numbers. I should be able to get the rest during the 
week.
The averages are pretty close, so I figured I would include some 
percentile
numbers. PELT and WALT numbers are with schedutil. On average it seems 
we're
introducing about 0.5% overhead with the current additional accounting.

Test: perf bench sched messaging -g 50 -l 5000
+-------------+-------------+----------+----------+-----------+
| 4.8.2-walt  | Performance | Ondemand | PELT     | WALT(10ms)|
+-------------+-------------+----------+----------+---------- +
|             |             |          |          |           |
|  90th       | 17.077      | 17.088   | 17.088   | 17.159    |
|             |             |          |          |           |
|  96th       | 17.117      | 17.421   | 17.198   | 17.343    |
|             |             |          |          |           |
|  Average    | 16.910      | 16.916   | 16.937   | 16.962    |
|             |             |          |          |           |
+-------------+-------------+----------+----------+-----------+
| 4.8.2-raw   | Performance | Ondemand | PELT     | WALT(10ms)|
+-------------+-------------+----------+----------+-----------+
|             |             |          |          |           |
|  90th       | 16.919      | 17.1694  | 16.986   | 0         |
|             |             |          |          |           |
|  96th       | 16.980      | 17.364   | 17.052   | 0         |
|             |             |          |          |           |
|  Average    | 16.841      | 16.902   | 16.860   | 0         |
+-------------+-------------+----------+----------+-----------+