Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755588AbbESH0l (ORCPT ); Tue, 19 May 2015 03:26:41 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60672 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755574AbbESH0h (ORCPT ); Tue, 19 May 2015 03:26:37 -0400 Date: Tue, 19 May 2015 00:26:06 -0700 From: tip-bot for Luca Abeni Message-ID: Cc: peterz@infradead.org, luca.abeni@unitn.it, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com, mingo@kernel.org Reply-To: peterz@infradead.org, torvalds@linux-foundation.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, luca.abeni@unitn.it, mingo@kernel.org, hpa@zytor.com In-Reply-To: <1431954032-16473-10-git-send-email-luca.abeni@unitn.it> References: <1431954032-16473-10-git-send-email-luca.abeni@unitn.it> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/dl/Documentation: Split Section 3 Git-Commit-ID: 6aaa10254dfe61c8c5e87c26e21be0664782a5b4 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3493 Lines: 85 Commit-ID: 6aaa10254dfe61c8c5e87c26e21be0664782a5b4 Gitweb: http://git.kernel.org/tip/6aaa10254dfe61c8c5e87c26e21be0664782a5b4 Author: Luca Abeni AuthorDate: Mon, 18 May 2015 15:00:32 +0200 Committer: Ingo Molnar CommitDate: Tue, 19 May 2015 08:39:21 +0200 sched/dl/Documentation: Split Section 3 Introduce 4 subsections to make Section 3 more readable. Signed-off-by: Luca Abeni Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: henrik@austad.us Cc: juri.lelli@gmail.com Cc: raistlin@linux.it Link: http://lkml.kernel.org/r/1431954032-16473-10-git-send-email-luca.abeni@unitn.it Signed-off-by: Ingo Molnar --- Documentation/scheduler/sched-deadline.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt index 2a924e1..e114513 100644 --- a/Documentation/scheduler/sched-deadline.txt +++ b/Documentation/scheduler/sched-deadline.txt @@ -8,6 +8,10 @@ CONTENTS 1. Overview 2. Scheduling algorithm 3. Scheduling Real-Time Tasks + 3.1 Definitions + 3.2 Schedulability Analysis for Uniprocessor Systems + 3.3 Schedulability Analysis for Multiprocessor Systems + 3.4 Relationship with SCHED_DEADLINE Parameters 4. Bandwidth management 4.1 System-wide settings 4.2 Task interface @@ -126,6 +130,9 @@ CONTENTS suited for periodic or sporadic real-time tasks that need guarantees on their timing behavior, e.g., multimedia, streaming, control applications, etc. +3.1 Definitions +------------------------ + A typical real-time task is composed of a repetition of computation phases (task instances, or jobs) which are activated on a periodic or sporadic fashion. @@ -166,6 +173,9 @@ CONTENTS is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum utilization[12]. +3.2 Schedulability Analysis for Uniprocessor Systems +------------------------ + If M=1 (uniprocessor system), or in case of partitioned scheduling (each real-time task is statically assigned to one and only one CPU), it is possible to formally check if all the deadlines are respected. @@ -204,6 +214,9 @@ CONTENTS time-consuming to be performed on-line. Hence, as explained in Section 4 Linux uses an admission test based on the tasks' utilizations. +3.3 Schedulability Analysis for Multiprocessor Systems +------------------------ + On multiprocessor systems with global EDF scheduling (non partitioned systems), a sufficient test for schedulability can not be based on the utilizations or densities: it can be shown that even if D_i = P_i task @@ -249,6 +262,9 @@ CONTENTS the total utilization is smaller or equal than M then the response times of the tasks are limited. +3.4 Relationship with SCHED_DEADLINE Parameters +------------------------ + Finally, it is important to understand the relationship between the SCHED_DEADLINE scheduling parameters described in Section 2 (runtime, deadline and period) and the real-time task parameters (WCET, D, P) -- 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/