linux-kernel - [tip:sched/core] sched/Documentation/sched-rt-group: Fix incorrect example

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Message-ID: <tip-3a09b8d45b3c05d49e581831de626927c37599f8@git.kernel.org>
Date:   Sun, 22 Jan 2017 02:14:52 -0800
From:   tip-bot for Zhou Chengming <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, peterz@...radead.org, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, zhouchengming1@...wei.com,
        mingo@...nel.org, tglx@...utronix.de
Subject: [tip:sched/core] sched/Documentation/sched-rt-group: Fix incorrect
 example

Commit-ID:  3a09b8d45b3c05d49e581831de626927c37599f8
Gitweb:     http://git.kernel.org/tip/3a09b8d45b3c05d49e581831de626927c37599f8
Author:     Zhou Chengming <zhouchengming1@...wei.com>
AuthorDate: Sun, 22 Jan 2017 15:22:35 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
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 <zhouchengming1@...wei.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: corbet@....net
Cc: iamyooon@...il.com
Cc: linux-doc@...r.kernel.org
Cc: lizefan@...wei.com
Link: http://lkml.kernel.org/r/1485069755-44287-1-git-send-email-zhouchengming1@huawei.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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