linux-kernel - Re: periods and deadlines in SCHED

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Message-ID: <4C58E42B.40000@cs.unc.edu>
Date:	Tue, 03 Aug 2010 23:53:15 -0400
From:	Andrea Bastoni <bastoni@...unc.edu>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Bjoern Brandenburg <bbb@...il.unc.edu>,
	Raistlin <raistlin@...ux.it>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Song Yuan <song.yuan@...csson.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nicola Manica <nicola.manica@...i.unitn.it>,
	Luca Abeni <lucabe72@...il.it>,
	Claudio Scordino <claudio@...dence.eu.com>,
	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Giuseppe Lipari <lipari@...is.sssup.it>
Subject: Re: periods and deadlines in SCHED_DEADLINE

On 08/03/2010 05:46 AM, Peter Zijlstra wrote:
> On Sun, 2010-07-11 at 08:42 +0200, Bjoern Brandenburg wrote:
>> If you want to do G-EDF with limited and different budgets on each CPU
>> (e.g., G-EDF tasks may only run for 100 out of 1000 ms on CPU 0, but
>> for 400 out of 1000 ms on CPU 1), then you are entering the domain of
>> restricted-supply scheduling, which is significantly more complicated
>> to analyze (see [1,2]).
> 
> Would making the thing homogenious by assuming the worst for all cpus
> make the analysis easier? That is, in the above example, only allow the
> G-EDF scheduler to run for 100 out of 1000 ms on both cpus.

Both [1,2] (and also [4]) assumes a more general model than the one based on the worst for all
CPUs, therefore the analysis (based on these papers) will likely be more pessimistic, but not
necessarily easier.

- Andrea

[4] E. Bini, M. Bertogna, S. Baruah, Virtual Multiprocessor Platforms: Specification and Use. In
Proceedings of the 2009 30th IEEE Real-Time Systems Symposium, 437-446, 2009.

-- 
Andrea Bastoni
Visiting Ph.D. Student
Dept. of Computer Science
University of North Carolina at Chapel Hill
http://www.sprg.uniroma2.it/home/bastoni/
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