From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753778AbdKXP4S (ORCPT ); Fri, 24 Nov 2017 10:56:18 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:38501 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752261AbdKXP4R (ORCPT ); Fri, 24 Nov 2017 10:56:17 -0500 X-Google-Smtp-Source: AGs4zMacNuPY3FBTcYpQPYmYjpHqCISuOgmEWmuTmQJV69AkUSO1KiB5W23ZZk1XJhIRpOSBY8oQxA== Subject: Re: [PATCH] sched/deadline: comment update for constrained deadline tasks explanation To: Alessio Balsini , linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Luca Abeni , Tommaso Cucinotta References: <1511521941-26952-1-git-send-email-alessio.balsini@arm.com> From: Daniel Bristot de Oliveira Message-ID: Date: Fri, 24 Nov 2017 16:56:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1511521941-26952-1-git-send-email-alessio.balsini@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/24/2017 12:12 PM, Alessio Balsini wrote: > Remove the adjective "relative" associated to the period of a periodic > task, since the period is an absolute value. > > Rephrased the comment with the aim of making it even more clear. > > Signed-off-by: Alessio Balsini > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Juri Lelli > Cc: Daniel Bristot de Oliveira > Cc: Luca Abeni > Cc: Tommaso Cucinotta > Cc: linux-kernel@vger.kernel.org > --- > kernel/sched/deadline.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index f349f7e..902b2e0 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -770,9 +770,9 @@ update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq) > } > > /* > - * Regarding the deadline, a task with implicit deadline has a relative > - * deadline == relative period. A task with constrained deadline has a > - * relative deadline <= relative period. > + * Regarding periodic real-time tasks, a constrained deadline task has the Not only periodic, but also sporadic. Moreover, for sporadic it is not _period_, but _minimum inter-arrival time_... IMHO, it is not worth to add such level of details, not even on articles people do, it just turn the explanation more confuse. See this, in the page 5: http://www-users.cs.york.ac.uk/~robdavis/papers/MPSurveyv5.0.pdf There is no mention for the kind of period. > + * relative deadline <= period. An implicit deadline task is a particular case It is important to keep the "relative" to avoid confusion with the variable "period" which is the "absolute period." I put relative to helps with the ambiguity of the term "period." -- Daniel