[ardour-users] Ardour errors during mixing

Steven Chamberlain steven at pyro.eu.org
Thu May 3 21:39:01 PDT 2007

sara lidgey wrote:
> I can't play back the mix for more that 20 seconds without an
> error. Are there any adjustments I can make to improve performance?

I spent a long time fighting this.  Although Linux has so many wonderful
audio tools, I often come across all kinds of stumbling blocks that kill
my productivity.  But it's definitely moving forward!

The errors you're experiencing are some of many I've suffered from.  I
went as far as replacing hardware, with some success, but there are many
things done in software which seem to make a difference.  For me, I
think the biggest help there may have been trying many realtime kernels
(different versions+configs), setting priorities for interrupts
(softirqs) with 'rtnice', and replacing jackd with jackdmp.

Unfortunately it can be hard to tell whether changing something has made
things better or worse.  It helps to try and measure things as best you
can:  things of interest here might be scheduler latency and disk read
speeds.  Once you have numbers to look at, you might know what to
concentrate on or if something you changed had any positive effect.

The best existing tools I've come across for measuring different aspects
of a system's performance are cyclictest, hdparm, and the latency trace
that comes with Ingo's -rt patch (though recently I haven't been able to
get that to work).

Some other things to experiment with are hdparm's settings (like DMA or
whatever is relevant to SATA drives), different choices of filesystem
(eg. reiser4 was awkward for me, but reiserfs outperformed ext2/3,
others like XFS may be worth trying), and of course experiment with
basic things like jackd command line options.

One last thing, is maybe one or more LADSPA plugins are suffering from
denormal issues (you'd probably hear various 'glitches' and see your CPU
usage shoot up towards 100% before something dies).  If you suspect
this, try disabling some or all of the LADSPA plugins.

Hope some of this helps in whatever way!
Steven Chamberlain
steven at pyro.eu.org

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