xruns running jackd -- should I be worried ?

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xruns running jackd -- should I be worried ?

Michael Gerdau
Hi list,

when I run the svn-version of jackd from the shell I get xruns (see
log further down). Now 20usec isn't really a lot and I'm not sure
whether I should be worried about it or not.

On the other hand if that's just ok then how do I get rid of those
(then to be ignored) xrun msgs ?

Anyway, here comes the log:
mgd@seneca:~> jackd -R -d alsa
no message buffer overruns
jackd 0.107.2
Copyright 2001-2005 Paul Davis and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
loading driver ..
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
control device hw:0
configuring for 48000Hz, period = 1024 frames, buffer = 2 periods
ALSA: final selected sample format for capture: 32bit little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit little-endian
ALSA: use 2 periods for playback


**** alsa_pcm: xrun of at least 0.019 msecs

**** alsa_pcm: xrun of at least 0.019 msecs

**** alsa_pcm: xrun of at least 0.019 msecs

**** alsa_pcm: xrun of at least 0.021 msecs

**** alsa_pcm: xrun of at least 0.020 msecs

**** alsa_pcm: xrun of at least 0.019 msecs

jack main caught signal 2
no message buffer overruns


Best,
Michael
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Re: xruns running jackd -- should I be worried ?

lars.luthman (Bugzilla)
On Tue, 2007-07-17 at 16:03 +0200, Michael Gerdau wrote:
> Hi list,
>
> when I run the svn-version of jackd from the shell I get xruns (see
> log further down). Now 20usec isn't really a lot and I'm not sure
> whether I should be worried about it or not.
>
> On the other hand if that's just ok then how do I get rid of those
> (then to be ignored) xrun msgs ?

When are those xruns occurring? If it's when you connect and disconnect
ports, then there is nothing to do about that - that's a limitation in
the current jackd.

If they happen when you're not touching the port connections at all,
then there is something wrong - either you are running at a too small
buffer size for your hardware (although 1024 should be plenty for almost
anything) or you are not running an RT-patched kernel. Some hardware
also have other quirks - if you are using an RT-patched kernel and still
get xruns you could try playing with the number of periods per buffer or
the --playback, --capture and --shorts options.

OT: Would it make sense to distribute a hardware database with JACK
where jackd could look up and use sensible default settings for the
installed hardware?


--ll

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Re: xruns running jackd -- should I be worried ?

Michael Gerdau
> When are those xruns occurring? If it's when you connect and disconnect
> ports, then there is nothing to do about that - that's a limitation in
> the current jackd.
>
> If they happen when you're not touching the port connections at all,
> then there is something wrong

I've just started jackd from a shell with no connections at all.

I'm running 2.6.22-cfs-v19 with CONFIG_PREEMPT=y. I'm member of @audio
and have these lines in my /etc/security/limits.conf:
@audio           -       rtprio          99
@audio           -       nice            -10
@audio           -       memlock         unlimited

I have pam 0.99.6.3 (as of openSUSE 10.2) installed.

Not sure what I'd have to do for a RT-patched kernel though.
You are not referring to running under 2.6.22.1-rt4, are you ?

CONFIG_HZ=250
Should I try CONFIG_HZ=1000 (or even higher values; applying Con Kolivas
patches to that end) ?

> - either you are running at a too small
> buffer size for your hardware (although 1024 should be plenty for almost
> anything) or you are not running an RT-patched kernel.

My HW is hda_intel (it is a Dell XPS M1710 with an Intel Core2 T7600
CPU which means it is not exactly undermuscled... ;-)

On an ancient system (P3 600MHz) I could run with a buffersize of
256 with RME HW under Woe32. Linux with ALSA on contemporary HW definitely
should be able to do with 1024 on my hda_intel !

Thank you for your response, best,
Michael
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Re: xruns running jackd -- should I be worried ?

lars.luthman (Bugzilla)
On Tue, 2007-07-17 at 23:06 +0200, Michael Gerdau wrote:

> > When are those xruns occurring? If it's when you connect and disconnect
> > ports, then there is nothing to do about that - that's a limitation in
> > the current jackd.
> >
> > If they happen when you're not touching the port connections at all,
> > then there is something wrong
>
> I've just started jackd from a shell with no connections at all.
>
> I'm running 2.6.22-cfs-v19 with CONFIG_PREEMPT=y. I'm member of @audio
> and have these lines in my /etc/security/limits.conf:
> @audio           -       rtprio          99
> @audio           -       nice            -10
> @audio           -       memlock         unlimited
>
> I have pam 0.99.6.3 (as of openSUSE 10.2) installed.
>
> Not sure what I'd have to do for a RT-patched kernel though.
> You are not referring to running under 2.6.22.1-rt4, are you ?
I am (if that means a kernel with Ingo Molnar's RT patch). Without that
(and preemption turned on) you almost certainly will get xruns now and
then even at large buffer sizes.

> CONFIG_HZ=250
> Should I try CONFIG_HZ=1000 (or even higher values; applying Con Kolivas
> patches to that end) ?

I don't think this matters.

> > - either you are running at a too small
> > buffer size for your hardware (although 1024 should be plenty for almost
> > anything) or you are not running an RT-patched kernel.
>
> My HW is hda_intel (it is a Dell XPS M1710 with an Intel Core2 T7600
> CPU which means it is not exactly undermuscled... ;-)

People have reported lots of problems with Intel HDA cards. I've never
tried any myself.


--ll

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Re: xruns running jackd -- should I be worried ?

Lee Revell
In reply to this post by Michael Gerdau
On 7/17/07, Michael Gerdau <[hidden email]> wrote:
> JACK compiled with System V SHM support.
> loading driver ..
> creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
> control device hw:0
> configuring for 48000Hz, period = 1024 frames, buffer = 2 periods

You must use 3 periods per buffer with HDA intel hardware.

Lee

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Re: xruns running jackd -- should I be worried ?

Michael Gerdau
> > JACK compiled with System V SHM support.
> > loading driver ..
> > creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
> > control device hw:0
> > configuring for 48000Hz, period = 1024 frames, buffer = 2 periods
>
> You must use 3 periods per buffer with HDA intel hardware.

Thanks a lot Lee, that worked like a charm.

After using 3 periods per buffer my xruns miraculously vanished. I could
even reduce the buffer size to 64 with xruns starting when the system is
under heavy load.

Best,
Michael
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Re: xruns running jackd -- should I be worried ?

Jussi Laako-2
In reply to this post by Michael Gerdau
Michael Gerdau wrote:
> I have pam 0.99.6.3 (as of openSUSE 10.2) installed.
>
> Not sure what I'd have to do for a RT-patched kernel though.
> You are not referring to running under 2.6.22.1-rt4, are you ?
>
> CONFIG_HZ=250
> Should I try CONFIG_HZ=1000 (or even higher values; applying Con Kolivas
> patches to that end) ?

To have reasonably well behaving kernel on SuSE, take the SuSE's
standard configuration as starting point and then

1) Set CPU optimization to your CPU
2) Have following config options enabled (I just diffed the configs):
        CONFIG_PREEMPT=y
        CONFIG_PREEMPT_BKL=y
        CONFIG_HZ_1000=y
        CONFIG_HZ=1000

I also have -rt patched kernel, but no rpm for it currently. For
multimedia desktop use, the above configuration works reasonably well.
For more serious use, I use the -rt kernel.


        - Jussi



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