[Bug 1193] New: Severe performance problems with Pulseaudio

[bugzilla-daemon at bugzilla.openmoko.org]

http://bugzilla.openmoko.org/cgi-bin/bugzilla/show_bug.cgi?id=1193

           Summary: Severe performance problems with Pulseaudio
           Product: OpenMoko
           Version: 2007.2
          Platform: Neo1973
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Host Software
        AssignedTo: buglog at lists.openmoko.org
        ReportedBy: mjr at iki.fi
                CC: buglog at lists.openmoko.org


Pulseaudio's behavior on my Neo has annoyed me for a while, and now I got around
to poking it a bit, with not much results but some. The visible issue is that
eg. when playing music with openmoko-mediaplayer, the pulseaudio server hogs up
25-30% of the CPU, which is enough to cause serious skipping of the audio (at
least my sample ogg tracks from Harvey Danger,
http://www.harveydanger.com/downloads/ ). This with no other clients playing
anything, of course, so no mixing required, just pushing bits from buffer to
sound driver.

ogg123, not going through pulseaudio, plays the same tracks quite well at around
80% CPU. Pulseaudio behavior is the same whether I use native ALSA or OSS sinks.

I straced pulseaudio a bit while playing music. Obviously, the strace emphasized
the skipping severely and quite possibly isn't useful for diagnosis due to
altering a lot of the timing, but some stuff was still going through.

Anyway, the thing that caught my eye was that between each write to the audio
device there were 16 pairs of alternating calls:
rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0

I presumed this to be threading-related, but apparently pulseaudio doesn't do
threads after all. Then I presumed it to be rabid syncing with the shared memory
area the client uses to communicate with it, but it seems to persist with
--disable-shm (as does the CPU hogging, whether it's related or not). Now I just
presume pulseaudio is on crack.

One should hopefully be able to have a decent mediaplayer experience without
waiting for GTA-02 in order to have more CPU to feed to the relentless
pulseaudio. Hopefully it's easily fixable to consume sane amounts of CPU
regardless.)



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