linux-kernel - [PATCH] sched: Documentation: sched-rt-group: fix example error

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Message-ID: <1485069755-44287-1-git-send-email-zhouchengming1@huawei.com>
Date:   Sun, 22 Jan 2017 15:22:35 +0800
From:   Zhou Chengming <zhouchengming1@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>
CC:     <corbet@....net>, <iamyooon@...il.com>, <mingo@...hat.com>,
        <peterz@...radead.org>, <lizefan@...wei.com>,
        <zhouchengming1@...wei.com>
Subject: [PATCH] sched: Documentation: sched-rt-group: fix example error

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>
---
 Documentation/scheduler/sched-rt-group.txt |    8 ++++----
 1 files 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
-- 
1.7.7