linux-kernel - Re: [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline tasks

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Date:	Fri, 12 Nov 2010 18:51:35 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Luca Abeni <luca.abeni@...tn.it>
Cc:	Raistlin <raistlin@...ux.it>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>, oleg@...hat.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Claudio Scordino <claudio@...dence.eu.com>,
	michael trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...i.unitn.it>,
	Dhaval Giani <dhaval@...is.sssup.it>,
	Harald Gustafsson <hgu1972@...il.com>,
	paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline
 tasks

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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