[pulseaudio-discuss] PA- Performance issue with PA read and CPU consumption in idle state

Radhakrishnan, Manjula (M.) rmanjula at visteon.com
Wed Feb 4 02:43:11 PST 2015

Hi ,

We are observing performance issue with Pulse Audio in our embedded infotainment platform.

To brief on the usage of PA in this platform , Pulse Audio is used for Audio routing from an Audio source provider to another Audio Source sink using Pulse Audio using the Null sink and Null sink.monitor.

The audio path is as below.
Audio source provider -> Pulse Audio Nullsink (eg. Route_test) -> Pulse Audio Null source (eg. Route_test.monitor) ->  Audio router to sink

There are two behavioral issues observed in the Pulse Audio , below is the description of the issues.

1.       The Audio source provider creates a Pulse stream and writes to the Pulse Audio Nullsink before the Audio router thread has opened the Pulse Stream for reading from nullsink.monitor . In this condition , from the application Audio router ,  PA reader thread opens the PA stream and  calls the PA read API , it is blocked for more than 1 sec inside PA read API before the first read is successful.

What could cause this delay in the first PA read ? Does the writer starting to write to PA first cause a delay/block on the reader when it eventually becomes active ?

2.       For the same issue above, on further debugging , On the PA reader side , the PA stream open is called and the stream is kept open always by the reader.  In this condition , the delay is no longer observed in the first PA read.  But this causes an impact on the CPU.

When the PA stream is always open and no reads are done ,significant CPU usage is observed , PA process consumes 21 - 23 % and the threaded-m1 consumes 5 - 7 % CPU even when there is no read/write happening in PA server.

Why is this high CPU observed and how to optimize the CPU , is there any configuration where the PA stream can be opened and still have low CPU consumption ?

Please provide your insights on the two queries.

Thanks & Regards

Manjula R
SME - Audio/DSP
Visteon Technical & Services Center , India
Phone: +91-44-49477829

[cid:image001.png at 01D0408C.C79CB740]<http://www.visteon.com/products/electronics/index.html>

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