linux-kernel - Re: [RFC PATCH 4/5] sched/fair: Use EAS also when overutilized

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Message-ID: <Zv5VLXVr5oYsABED@google.com>
Date: Thu, 3 Oct 2024 08:26:21 +0000
From: Quentin Perret <qperret@...gle.com>
To: Lukasz Luba <lukasz.luba@....com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com,
	peterz@...radead.org, juri.lelli@...hat.com,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, rafael.j.wysocki@...el.com,
	linux-kernel@...r.kernel.org, qyousef@...alina.io,
	hongyan.xia2@....com
Subject: Re: [RFC PATCH 4/5] sched/fair: Use EAS also when overutilized

On Thursday 03 Oct 2024 at 09:15:31 (+0100), Lukasz Luba wrote:
> BTW, do you know that if you or anyone wants to improve the EAS/EM
> should be able to provide the power numbers?
> 
> W/o the power numbers the discussion is moot. Many times SW engineers
> have wrong assumptions about HW, therefore we have to test and
> measure. There are confidential power saving techniques in HW
> that can be missed and some ugly workaround created in SW for issues
> which don't exist.
> 
> That's why we have to discuss the power numbers.

And generally speaking +1 to the above, it would be nice to have power
numbers to motivate the series better. The hackbench results are nice to
show the limited overhead, but they obviously don't help evaluating the
patches against what they claim to do (making better energy decisions in
feec() and such).

Thanks,
Quentin