linux-kernel - Re: [RFC 4/8] Improve the tracking of active utilisation

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Date:	Thu, 28 Jan 2016 14:08:39 +0100
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Luca Abeni <luca.abeni@...tn.it>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@....com>
Subject: Re: [RFC 4/8] Improve the tracking of active utilisation

Hi Luca,

On 27 January 2016 at 15:45, Luca Abeni <luca.abeni@...tn.it> wrote:
> Hi Peter,
>
> On Wed, 27 Jan 2016 15:39:46 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
>
>> On Wed, Jan 27, 2016 at 02:36:51PM +0100, Luca Abeni wrote:
>> > Ok, so I implemented this idea, and I am currently testing it...
>> > The first experiments seem to show that there are no problems, but I
>> > just tried some simple workload (rt-app, or some other periodic
>> > taskset scheduled by SCHED_DEADLINE). Do you have suggestions for
>> > more "interesting" (and meaningful) tests/experiments?
>>
>> rt-app is the workload generator, right?
>>
>> I think the most interesting part here is the switched_from path, so
>> you'd want the workload to include a !rt task that gets PI boosted to
>> deadline every so often.
>>
>> Also, does rt-app let tasks die? Or does it spawn N tasks and lets
>> them run jobs until the end? I think you want to put some effort in
>> task_dead_dl() as well.
>>
>> After that, just make sure rt-app generates a _lot_ of tasks such that
>> the migration thing gets used.
>
> Thanks; I'll check with Juri how to do all of this with rt-app (or how
> to modify rt-app to stress these functionalities).

This version of workload generator /rt-app can do all sequences you want:
https://git.linaro.org/power/rt-app.git/shortlog/refs/heads/master
The merge of these changes are ongoing but still not finished.

Let me know if you need help to use it and create some use cases

Regards,
Vincent

>
>
>                         Thanks,
>                                 Luca