linux-kernel - Re: [RFC][PATCH 02/11] sched: SCHED

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Date:	Tue, 13 Apr 2010 20:22:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Raistlin <raistlin@...ux.it>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Henrik Austad <henrik@...tad.us>,
	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 <t.cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...il.com>,
	Luca Abeni <luca.abeni@...tn.it>
Subject: Re: [RFC][PATCH 02/11] sched: SCHED_DEADLINE policy implementation.

On Sun, 2010-02-28 at 20:17 +0100, Raistlin wrote:
> +/*
> + * Pure Earliest Deadline First (EDF) scheduling does not deal with the
> + * possibility of a task lasting more than what it declared, and thus
> + * exhausting its runtime.
> + *
> + * Here we are interested in making runtime overrun possible, but we do
> + * not want a task which is misbehaving to affect the scheduling of all
> + * other tasks.
> + * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
> + * is used, in order to confine each task within its own bandwidth.
> + *
> + * This function deals exactly with that, and ensures that when the runtime
> + * of a task is replenished, its deadline is also postponed. That results
> + * in "priority unboosting" for the overrunning task, and makes it impossible
> + * for it to cause unexpected interfere to other tasks in the system.
> + */ 

This is not about lock/inheritance related overrun, right? But simply a
task that got its WCET wrong.


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