Subject: Re: [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline
 tasks
From: Peter Zijlstra <peterz@infradead.org>
To: Luca Abeni <luca.abeni@unitn.it>
Cc: Raistlin <raistlin@linux.it>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Chris Friesen <cfriesen@nortel.com>, oleg@redhat.com,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Darren Hart <darren@dvhart.com>, Johan Eker <johan.eker@ericsson.com>,
        "p.faure" <p.faure@akatech.ch>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Claudio Scordino <claudio@evidence.eu.com>,
        michael trimarchi <trimarchi@retis.sssup.it>,
        Fabio Checconi <fabio@gandalf.sssup.it>,
        Tommaso Cucinotta <cucinotta@sssup.it>,
        Juri Lelli <juri.lelli@gmail.com>,
        Nicola Manica <nicola.manica@disi.unitn.it>,
        Dhaval Giani <dhaval@retis.sssup.it>,
        Harald Gustafsson <hgu1972@gmail.com>,
        paulmck <paulmck@linux.vnet.ibm.com>
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Date: Fri, 12 Nov 2010 18:51:35 +0100
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On Fri, 2010-11-12 at 18:41 +0100, Luca Abeni wrote:
> > The problem the stochastic execution time model tries to address is the
> > WCET computation mess, WCET computation is hard and often overly
> > pessimistic, resulting in under-utilized systems.
> [...]
> BTW, sorry for the shameless plug, but even with the current 
> SCHED_DEADLINE you are not forced to dimension the runtime using the 
> WCET. 

Yes you are, it pushes the deadline back on overrun. The idea it to
maintain the deadline despite overrunning your budget (up to a point).

The paper we're all talking about is:

A. Mills and J. Anderson, " A Stochastic Framework for Multiprocessor
Soft Real-Time Scheduling", Proceedings of the 16th IEEE Real-Time and
Embedded Technology and Applications Symposium, pp. 311-320, April 2010.
http://www.cs.unc.edu/~anderson/papers/rtas10brevised.pdf

And I see they've got a new stochastic paper out:

A. Mills and J. Anderson, " Scheduling Stochastically-Executing Soft
Real-Time Tasks: A Multiprocessor Approach Without Worst-Case Execution
Times", in submission. 
http://www.cs.unc.edu/~anderson/papers/rtas11b.pdf


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