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Subject: Re: [RFC][PATCH 02/22] sched: add extended scheduling interface
From: Steven Rostedt <rostedt@goodmis.org>
To: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Cc: Peter Zijlstra <peterz@infradead.org>, Raistlin <raistlin@linux.it>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        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>,
        Luca Abeni <luca.abeni@unitn.it>, Dhaval Giani <dhaval@retis.sssup.it>,
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Date: Fri, 12 Nov 2010 14:21:38 -0500
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On Fri, 2010-11-12 at 18:42 +0100, Tommaso Cucinotta wrote:
> Il 12/11/2010 17:38, Steven Rostedt ha scritto:
> > A while ago I implemented an EDF scheduler for a client (before working
> > with Red Hat), and one thing they asked about was having a "soft group",
> > which was basically: This group is guaranteed X runtime in Y period, but
> > if the system is idle, let the group run, even if it has exhausted its X
> > runtime.
> >
> > Is this supported?
> Actually, I know that Dario has an implementation of exactly this 
> feature (and it used to be implemented in our previous scheduler as 
> well, i.e., the old AQuoSA stuff):
> a per-task flag, when enabled, allows to put temporarily the task into 
> SCHED_OTHER when its budget is exhausted. Therefore, it will be allowed 
> to run for more than its budget but without breaking the temporal 
> isolation with the other SCHED_DEADLINE tasks. Furthermore, it won't 
> starve other SCHED_OTHER tasks, as it will compete with them for the CPU 
> during the budget-exhausted time windows.

Good to know, thanks!

-- Steve