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

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Message-ID: <4CE18C7E.2060202@unitn.it>
Date:	Mon, 15 Nov 2010 20:39:42 +0100
From:	Luca Abeni <luca.abeni@...tn.it>
To:	"James H. Anderson" <anderson@...unc.edu>
CC:	Raistlin <raistlin@...ux.it>,
	Peter Zijlstra <peterz@...radead.org>,
	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>,
	Bjoern Brandenburg <bbb@...il.unc.edu>
Subject: Re: [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline tasks

On 15/11/10 19:37, James H. Anderson wrote:
[...]
> If you're talking about our most recent "stochastic" paper, it is about
> supporting
> soft real-time task systems on a multiprocessor where resource
> reservations are
> used. The main result of the paper is that if you provision the
> reservation for a
> task slightly higher than it's average-case execution time
[...]
BTW, I think we are aligned on this.

I was a little bit surprised when Peter mentioned allocating a runtime 
equal to the average execution time (because of the meta-stability 
considerations that Tommaso also mentioned), but I fully agree that if 
the allocated runtime is higher than the average execution time then the 
queue is stable and it's possible to find a bound for the expected 
tardiness (or even its probability distribution... This is similar to my 
"probabilistic deadlines").


			Luca
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