From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753020AbaHUO6h (ORCPT ); Thu, 21 Aug 2014 10:58:37 -0400 Received: from mail3.unitn.it ([193.205.206.24]:54545 "EHLO mail3.unitn.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751552AbaHUO6f (ORCPT ); Thu, 21 Aug 2014 10:58:35 -0400 X-Greylist: delayed 623 seconds by postgrey-1.27 at vger.kernel.org; Thu, 21 Aug 2014 10:58:34 EDT Date: Thu, 21 Aug 2014 16:47:58 +0200 From: Luca Abeni To: Ingo Molnar Cc: Juri Lelli , peterz@infradead.org, rdunlap@infradead.org, mingo@redhat.com, henrik@austad.us, raistlin@linux.it, juri.lelli@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/4] Documentation/scheduler/sched-deadline.txt: improve and clarify AC bits Message-ID: <20140821164758.334a1cf7@luca-1225C> In-Reply-To: <20140821133836.GA29495@gmail.com> References: <1408611700-9420-1-git-send-email-juri.lelli@arm.com> <1408611700-9420-4-git-send-email-juri.lelli@arm.com> <20140821133836.GA29495@gmail.com> X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo, On Thu, 21 Aug 2014 15:38:37 +0200 Ingo Molnar wrote: [...] > > + If the total utilisation sum_i(WCET_i/P_i) (sum of the > > utilisations > > + WCET_i/P_i of all the tasks in the system - notice that when > > considering > > + multiple tasks, the parameters of the i-th one are indicated with > > the "_i" > > + suffix) is larger than M (with M equal to the number of CPUs), > > then the > > + system will surely not be able to respect all of the deadlines, > > and no > > + execution time is guaranteed for non real-time tasks, which risk > > to be > > + starved by real-time tasks. > > The last part doesn't really parse as correct English for me - > maybe also split this overly long sentence into two or three > sentences, to make it easier to understand? Sorry about this; after re-reading the sentence, I agree it looks confusing. What about: " If the total utilisation sum_i(WCET_i/P_i) is larger than M (with M equal to the number of CPUs), then the scheduler can not be able to respect all of the deadlines. Note that the total utilisation is defined as the sum of the utilisations WCET_i/P_i of all the real-time tasks in the system (when considering multiple real-time tasks, the parameters of the i-th one are indicated with the "_i" suffix). Moreover, if the total utilisation is larger than M, then non real-time tasks risk to be starved by real-time tasks. " Does this look more clear / acceptable? Thanks, Luca