From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbdAVKPm (ORCPT ); Sun, 22 Jan 2017 05:15:42 -0500 Received: from terminus.zytor.com ([65.50.211.136]:60536 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751283AbdAVKPd (ORCPT ); Sun, 22 Jan 2017 05:15:33 -0500 Date: Sun, 22 Jan 2017 02:14:52 -0800 From: tip-bot for Zhou Chengming Message-ID: Cc: hpa@zytor.com, peterz@infradead.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, zhouchengming1@huawei.com, mingo@kernel.org, tglx@linutronix.de Reply-To: peterz@infradead.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, zhouchengming1@huawei.com, tglx@linutronix.de, mingo@kernel.org In-Reply-To: <1485069755-44287-1-git-send-email-zhouchengming1@huawei.com> References: <1485069755-44287-1-git-send-email-zhouchengming1@huawei.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/Documentation/sched-rt-group: Fix incorrect example Git-Commit-ID: 3a09b8d45b3c05d49e581831de626927c37599f8 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 Commit-ID: 3a09b8d45b3c05d49e581831de626927c37599f8 Gitweb: http://git.kernel.org/tip/3a09b8d45b3c05d49e581831de626927c37599f8 Author: Zhou Chengming AuthorDate: Sun, 22 Jan 2017 15:22:35 +0800 Committer: Ingo Molnar CommitDate: Sun, 22 Jan 2017 10:34:17 +0100 sched/Documentation/sched-rt-group: Fix incorrect example I feel that the example given in the document to show the possibility of task starvation of configurable period is wrong. The example says group A and B both have 50% bandwidth, and a while (1) loop in A will run for the full period of B and can starve B's tasks. So I think the runtime of group A should be 50000us, then the period and runtime of group B should be 50000us and 25000us. Signed-off-by: Zhou Chengming Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: corbet@lwn.net Cc: iamyooon@gmail.com Cc: linux-doc@vger.kernel.org Cc: lizefan@huawei.com Link: http://lkml.kernel.org/r/1485069755-44287-1-git-send-email-zhouchengming1@huawei.com Signed-off-by: Ingo Molnar --- Documentation/scheduler/sched-rt-group.txt | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt index a03f0d9..d8fce3e 100644 --- a/Documentation/scheduler/sched-rt-group.txt +++ b/Documentation/scheduler/sched-rt-group.txt @@ -158,11 +158,11 @@ as its prone to starvation without deadline scheduling. Consider two sibling groups A and B; both have 50% bandwidth, but A's period is twice the length of B's. -* group A: period=100000us, runtime=10000us - - this runs for 0.01s once every 0.1s +* group A: period=100000us, runtime=50000us + - this runs for 0.05s once every 0.1s -* group B: period= 50000us, runtime=10000us - - this runs for 0.01s twice every 0.1s (or once every 0.05 sec). +* group B: period= 50000us, runtime=25000us + - this runs for 0.025s twice every 0.1s (or once every 0.05 sec). This means that currently a while (1) loop in A will run for the full period of B and can starve B's tasks (assuming they are of lower priority) for a whole