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doc/user: section about real-time scheduling

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Max Kellermann 2015-10-27 10:31:50 +01:00
parent 5719207dfa
commit f901cd042b
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doc/user.xml
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@ -1190,6 +1190,58 @@ database {
plugin). plugin).
</para> </para>
</section> </section>
<section id="realtime">
<title>Real-Time Scheduling</title>
<para>
On Linux, <application>MPD</application> attempts to configure
<ulink
url="https://en.wikipedia.org/wiki/Real-time_computing">real-time
scheduling</ulink> for some threads that benefit from it.
</para>
<para>
This is only possible you allow <application>MPD</application>
to do it. This privilege is controlled by
<varname>RLIMIT_RTPRIO</varname>
<varname>RLIMIT_RTTIME</varname>. You can configure this
privilege with <command>ulimit</command> before launching
<application>MPD</application>:
</para>
<programlisting>ulimit -HS -r 50; mpd</programlisting>
<para>
Or you can use the <command>prlimit</command> program from the
<application>util-linux</application> package:
</para>
<programlisting>prlimit --rtprio=50 --rttime=unlimited mpd</programlisting>
<para>
The <application>systemd</application> service file shipped
with <application>MPD</application> comes with this setting.
</para>
<para>
This works only if the Linux kernel was compiled with
<varname>CONFIG_RT_GROUP_SCHED</varname> disabled. Use the
following command to check this option for your current
kernel:
</para>
<programlisting>zgrep ^CONFIG_RT_GROUP_SCHED /proc/config.gz</programlisting>
<note>
<para>
There is a rumor that real-time scheduling improves audio
quality. That is not true. All it does is reduce the
probability of skipping (audio buffer xruns) when the
computer is under heavy load.
</para>
</note>
</section>
</chapter> </chapter>
<chapter id="use"> <chapter id="use">