From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753422AbbERNFH (ORCPT ); Mon, 18 May 2015 09:05:07 -0400 Received: from mail2.unitn.it ([193.205.194.22]:51318 "EHLO mail2.unitn.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752626AbbERNEv (ORCPT ); Mon, 18 May 2015 09:04:51 -0400 From: Luca Abeni To: peterz@infradead.org Cc: henrik@austad.us, juri.lelli@gmail.com, raistlin@linux.it, mingo@kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Luca Abeni Subject: [PATCH 9/9] Documentation/scheduler/sched-deadline.txt: Split Section 3 Date: Mon, 18 May 2015 15:00:32 +0200 Message-Id: <1431954032-16473-10-git-send-email-luca.abeni@unitn.it> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1431954032-16473-1-git-send-email-luca.abeni@unitn.it> References: <1431954032-16473-1-git-send-email-luca.abeni@unitn.it> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce 4 subsections to make Section 3 more readable. Signed-off-by: Luca Abeni --- 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 ead13bcc..163675c 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) -- 1.7.9.5