From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932090AbaHVIbT (ORCPT ); Fri, 22 Aug 2014 04:31:19 -0400 Received: from mail-we0-f178.google.com ([74.125.82.178]:45119 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755297AbaHVIbQ (ORCPT ); Fri, 22 Aug 2014 04:31:16 -0400 Date: Fri, 22 Aug 2014 10:31:11 +0200 From: Ingo Molnar To: Luca Abeni 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: <20140822083110.GB8771@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> <20140821164758.334a1cf7@luca-1225C> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140821164758.334a1cf7@luca-1225C> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Luca Abeni wrote: > 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: Looks good to me, with a few details: > " > 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. s/can not be able to respect/is unable to respect > 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). The parentheses are a bit confusing here - they come after a half finished sentence - which at the end turns out to have ended. How about something like: > Note that total utilisation is defined as the sum of the > utilisations WCET_i/P_i over all the real-time tasks in the > system. When considering multiple real-time tasks, the > parameters of the i-th task 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. How about: > Moreover, if the total utilisation is larger than M, then we > risk starving non- real-time tasks by real-time tasks. ? Thanks, Ingo