Date: Tue, 14 Jan 2014 17:51:19 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        "mingo@kernel.org" <mingo@kernel.org>,
        "markgross@thegnar.org" <markgross@thegnar.org>,
        "vincent.guittot@linaro.org" <vincent.guittot@linaro.org>,
        Catalin Marinas <Catalin.Marinas@arm.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [3/11] issue 3: No understanding of potential cpu capacity
Message-ID: <20140114165119.GJ7572@laptop.programming.kicks-ass.net>
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On Tue, Jan 14, 2014 at 04:39:54PM +0000, Morten Rasmussen wrote:
> Responsiveness is still very important. It is quite hard to control. CFS
> doesn't consider latency. The only way to get the best responsiveness is
> to go for best performance which comes at a high cost in energy.

The big problem is that the normal unix task model doesn't cover his at
all -- nice isn't much of a knob.

There's ways in which you can adapt CFS to include such a measure
(search for the EEVDF patches), but I was kinda hoping that tasks that
really desire responsiveness could be made to use SCHED_DEADLINE or
such.


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