Hi Ryan,
Thanks, no I haven't done that. I did add myself to the audio group, but
presumably this isn't sufficient? I don't see the priorities reported in htop
being any different for the various mix threads - although I've never quite
understood the difference between the priorities and niceness under linux.
In any case, I'll give this a go tonight.
Cheers,
Sam
From: RJ Ryan [mailto:rr...@mixxx.org]
Sent: 14 February 2013 15:45
To: Sam Martin
Cc: mixxx-devel@lists.sourceforge.net
Subject: Re: [Mixxx-devel] Linux latency performance
Hi Sam,
We do set thread priorities but if your user account doesn't have the
permissions to set them via /etc/security/limits.conf then these priority
changes do nothing. Have you made this change?
http://www.gentoo.org/proj/en/desktop/sound/realtime.xml
See the bit about 'rtprio'.
Thanks,
RJ
On Thu, Feb 14, 2013 at 10:10 AM, Sam Martin
<sam.mar...@geomerics.com<mailto:sam.mar...@geomerics.com>> wrote:
Hi everyone,
I've been looking at things that force my Ubuntu linux install of Mixx to miss
buffer updates (audio glitches). I have a low latency kernel installed with the
usual low latency linux tweaks, and a uca202 audio interface, but see glitches
even when running with large buffer sizes.
I had some success by using htop (a basic linux performance monitor) to monitor
cpu intensive applications, and boosting the 'niceness' of non-mixx
applications. Making metacity, x11 and other graphics-related apps nicer helps,
but it turns out the biggest glitches actually come from mixx itself.
I haven't studied the code yet, but it appears to launch a fairly large number
of threads which compete equally for cpu time. I've found that if I make the
main mixx thread nicer (effectively decreasing it's scheduling priority and
making it more likely to be pre-emptied), and identify and do the same to the
threads that seem to do analysis work when you first load a track, the vast
majority of glitches go away. I'm guessing the kernel is then doing a better
job at pre-empting these threads, allowing the time critical ones to run
promptly.
So, is mixx doing anything to hint about which of its threads are high/low
priority? Could it be setting the niceness of each thread (at least on linux)
based on context somehow?
If this sounds sensible, and someone can give me a few pointers to get started,
I'd be happy to consider making a patch.
Cheers,
Sam
p.s. great work btw!
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