linux-kernel - Re: [PATCH v3 0/6] sched: Add new tracepoints required for EAS testing

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Message-ID: <20190605223343.r42pgngvs7myzfke@e107158-lin.cambridge.arm.com>
Date:   Wed, 5 Jun 2019 23:33:43 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Pavankumar Kondeti <pkondeti@...eaurora.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Uwe Kleine-Konig <u.kleine-koenig@...gutronix.de>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Quentin Perret <quentin.perret@....com>
Subject: Re: [PATCH v3 0/6] sched: Add new tracepoints required for EAS
 testing

On 06/04/19 23:17, Christoph Hellwig wrote:
> > The following patches add the bare minimum tracepoints required to perform EAS
> > testing in Lisa[1].
> 
> What is EAS?  Whhy is "Lisa" not part of the patch submission?
> submission.

EAS is Energy Aware Scheduling. It was merged in 5.0.

Lisa is a python based testing platform that has dependency on other binaries
like trace-cmd, rt-app, etc. It is not suitable for kernel submission.

Lisa, or any userspace based testing for that matter, requires to know what's
happening inside the scheduler to test its behavior. I don't know know of any
other scheduler centric testing framework. I didn't intend to specify Lisa as
the sole user and reason for these tracepoints, I know others are interested in
these tracepoints in general for anyone who wants to achieve a similar goal of
studying scheduler PELT behavior and how it affects some of the decisions it
makes.

We had a talk in OSPM a couple of weeks ago to cover this topic if you're
interested to learn more

	https://www.youtube.com/watch?v=I_MZ9XS3_zc

> 
> > It is done in this way because adding new TRACE_EVENTS() is no longer accepted
> > AFAIU.
> 
> Huh?  We keep adding trace events all the time.  And they actually
> are useful because they are testable.
> 
> This series on the other hand adds exports not used in tree, which is
> a big no-go.

I see that Peter has already covered this part.

Thanks

--
Qais Yousef