Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752011Ab0GJHUg (ORCPT ); Sat, 10 Jul 2010 03:20:36 -0400 Received: from mail0.unitn.it ([193.205.206.51]:56867 "EHLO mail0.unitn.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751613Ab0GJHUf (ORCPT ); Sat, 10 Jul 2010 03:20:35 -0400 Subject: Re: periods and deadlines in SCHED_DEADLINE From: Luca Abeni To: Peter Zijlstra Cc: Raistlin , linux-kernel , Song Yuan , Dmitry Adamushko , Thomas Gleixner , Nicola Manica , Claudio Scordino , Harald Gustafsson , Bjoern Brandenburg , bastoni@cs.unc.edu, Giuseppe Lipari In-Reply-To: <1278685470.1900.206.camel@laptop> References: <1278682707.6083.227.camel@Palantir> <1278685470.1900.206.camel@laptop> Content-Type: text/plain Date: Sat, 10 Jul 2010 09:11:47 +0200 Message-Id: <1278745907.5248.18.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1081 Lines: 24 On Fri, 2010-07-09 at 16:24 +0200, Peter Zijlstra wrote: > On Fri, 2010-07-09 at 15:38 +0200, Raistlin wrote: > > Basically, from the scheduling point of view, what it could happen is > > that I'm still _NOT_ going to allow a task with runtime Q_i, deadline > > D_i and period P_i to use more bandwidth than Q_i/P_i, I'm still using D > > for scheduling but the passing of the simple in-kernel admission test > > Sum_i(Q_i/P_i)<1 won't guarantee that the task will always finish its > > jobs before D. > > But the tardiness would still be bounded, right? So its a valid Soft-RT > model? I think that if Sum_i(Q_i/P_i)<1 but Sum_i(Q_i/min{P_i,D_i})>=1 then you can have sporadic deadline misses, but it should still be possible to compute an upper bound for the tardiness. But this is just a feeling, I have no proof... :) Luca -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/