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doc/user.xml: example "ps" command for real-time scheduling check

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Max Kellermann 2018-02-17 01:07:06 +01:00
parent 420582ec5e
commit 8624d8c144
1 changed files with 28 additions and 0 deletions
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doc/user.xml
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@ -1399,6 +1399,34 @@ database {
<programlisting>zgrep ^CONFIG_RT_GROUP_SCHED /proc/config.gz</programlisting>
<para>
You can verify whether the real-time scheduler is active with
the <command>ps</command> command:
</para>
<programlisting># ps H -q `pidof -s mpd` -o 'pid,tid,cls,rtprio,comm'
PID TID CLS RTPRIO COMMAND
16257 16257 TS - mpd
16257 16258 TS - io
16257 16259 FF 50 rtio
16257 16260 TS - player
16257 16261 TS - decoder
16257 16262 FF 50 output:ALSA
16257 16263 IDL 0 update</programlisting>
<para>
The <varname>CLS</varname> column shows the CPU scheduler;
<parameter>TS</parameter> is the normal scheduler;
<parameter>FF</parameter> and <parameter>RR</parameter> are
real-time schedulers. In this example, two threads use the
real-time scheduler: the <command>output</command> thread and
the <command>rtio</command> (real-time I/O) thread; these two
are the important ones. The database update thread uses the
idle scheduler ("<parameter>IDL</parameter> in
<command>ps</command>), which only gets CPU when no other
process needs it.
</para>
<note>
<para>
There is a rumor that real-time scheduling improves audio