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bitbake: bitbake-user-manual: Added new description for BB_TASK_IONICE_LEVEL

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Added a new variable description here for this variable.

(Bitbake rev: 4e0da1ef4a58a7ba4b92d4e07ef79cf7bd90abf0)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2015-10-27 09:15:10 -07:00 committed by Richard Purdie
parent 183290a9d4
commit c8051c52a4
1 changed files with 50 additions and 0 deletions
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bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml
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@ -856,6 +856,56 @@
</glossdef>
</glossentry>
<glossentry id='var-BB_TASK_IONICE_LEVEL'><glossterm>BB_TASK_IONICE_LEVEL</glossterm>
<glossdef>
<para>
Allows adjustment of a task's Input/Output priority.
During Autobuilder testing, random failures can occur
for tasks due to I/O starvation.
These failures occur during various QEMU runtime timeouts.
You can use the <filename>BB_TASK_IONICE_LEVEL</filename>
variable to adjust the I/O priority of these tasks.
<note>
This variable works similarly to the
<link linkend='var-BB_TASK_NICE_LEVEL'><filename>BB_TASK_NICE_LEVEL</filename></link>
variable except with a task's I/O priorities.
</note>
</para>
<para>
Set the variable as follows:
<literallayout class='monospaced'>
BB_TASK_IONICE_LEVEL = "<replaceable>class</replaceable>.<replaceable>prio</replaceable>"
</literallayout>
For <replaceable>class</replaceable>, the default value is
"2", which is a best effort.
You can use "1" for realtime and "3" for idle.
If you want to use realtime, you must have superuser
privileges.
</para>
<para>
For <replaceable>prio</replaceable>, you can use any
value from "0", which is the highest priority, to "7",
which is the lowest.
The default value is "4".
You do not need any special privileges to use this range
of priority values.
<note>
In order for your I/O priority settings to take effect,
you need the Completely Fair Queuing (CFQ) Scheduler
selected for the backing block device.
To select the scheduler, use the following command form
where <replaceable>device</replaceable> is the device
(e.g. sda, sdb, and so forth):
<literallayout class='monospaced'>
$ sudo sh -c “echo cfq > /sys/block/<replaceable>device</replaceable>/queu/scheduler
</literallayout>
</note>
</para>
</glossdef>
</glossentry>
<glossentry id='var-BB_TASK_NICE_LEVEL'><glossterm>BB_TASK_NICE_LEVEL</glossterm>
<glossdef>
<para>