[pulseaudio-discuss] PulseAudio Painfully Slow

Clemens Eisserer linuxhippy at gmail.com
Tue Jul 15 11:35:58 PDT 2014


> Just a shot in the dark here, but Skype had an issue with PulseAudio 4
That has been fixed in the last release.

> According to the screenshot, the time is spent in the ppoll syscall.
> This rings a bell: your bug may be a duplicate of an already-fixed thing.
Thanks for the pointer.
Before I go through the trouble compiling upstream PA, the bug-report
mentions PA starts to poll in a spinning loop consuming 100% cpu -
while I see PA consuming 25-30% with 10% CPU load still available.

> First, the algorithms are more complex. Second, X server doesn't do much.
> 640x480 pixels * 30 fps * 2 bytes per pixel = 18.4 megabytes per second
> Add the fact that X server does just a memcpy in the worst case (and exactly nothing in the best case),

I don't know anybody who still uses a VGA 640x480 display with 16-bit
color depth - my display is 1920x1280x4 * 30fps = ~280mb/s at 30 fps.
Furthermore, X has to move the data over busses to vram and in the
worst case do a blit using the CPU.

>From my personal experience, compute-bound workload often tends to be
easier to handle than bandwidth-bound stuff where suddenly bottlenecks
are waiting all along the data paths (I do performance-tuning for VLIW
DSP chips as a living).

Anyway, in my profile I don't see any resampling. Either I am really
hitting that bug, or it is another inefficiency happening somewhere.

Regards, Clemens

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