[linux-audio-user] 2x RME Multifaces, ALSA, JACK & Ardour -> XRUNS?

Hello LAU,

I've been battling with this problem for about a week now, have searched all
over the place and have still not found a solution. I'm hoping somebody on
this list can help me out...

Hardware is as follows:
Dell PE1800 Dual 2.8GHz EM64T w/1GB RAM
PERC4/SC RAID5 (configured with write-back caching - bonnie++ reports 50MB/s
block writes)
2x RME Multifaces (configured with Word clock sync/ADAT fiber cable for sync)

OS Specifics:
Gentoo Linux (fairly conservative CFLAGS=" -march=k8 -O3 -pipe")
Kernel version 2.6.12
XFS / filesystem

Goal:
Record 16 tracks using the 8 analogue inputs of the each of the two cards
simultaneously in ardour without any XRUNs.

Symptoms:
qjackctl reports hundreds of XRUNs when the system is sitting idle with
nothing more than the window manager (KDE 3.4.1) and Jack running. I can get
ardour to record if I tell it to ignore XRUNs, but that's obviously not what
I want. Strange thing is that jackd -v doesn't always report XRUNs that
ardour and qjackctl seem to complain about.

The different things I've tried:

1) Ingo Molnar's realtime-preempt-2.6.12-final-V0.7.51-06 patch (could only
get it to compile with full preempt on x86_64). I've tried this as well as
the standard Gentoo sources kernel without the patch - no apparent
difference.

2) With and without realtime-lsm (I tried using rtlimits too, but I'm not sure
that I had it setup correctly). The problem still occurs even if I run
everything as root - so I don't think it's a permissions/capabilities
problem. I've also tried various chrt -f priority levels for everything,
including using chrt -f -p 99 on the sound card IRQs. Strange thing is that
half of the KDE stuff (like kicker) also shows up with PR = RT in top, but
chrt reports SCHED_OTHER, priority 0 for all of these.

3) Synchronising the two multifaces with Word clock (at 48kHz) as well as ADAT
in (at both 48 and 96kHz). The problem is worse at 96kHz but it happens at
48kHz too - ultimately I would like to run a 96kHz configuration, but I
thought I'd try 48 too.

4) Various jackd settings (including various -R -P ? optional as well as all
-p options). Problem still occurs with -p 8192.

5) Various configurations in /etc/asound.conf for binding the two cards
together, but I must admit I don't really know what I'm doing here and
everything has been pieced together from examples on the web. I've attached
the current version of the file which has options for the 48 and 96kHz
configurations of the multifaces. I've also tried leaving the ADAT and SPDIF
channels out of the configuration, since I'm only interested in the analogue
inputs.

6) Tried jack and ardour without KDE running (under TWM) - no funny processes
with RT Priority in top, but problem still persists. I suspect it may only be
a bug in top tho', since chrt still shows sensible stuff.

7) I couldn't install Gentoo's media-sound/alsa-driver package against the
Ingo Molnar patched sources, but the problem is still there when I compile
alsa-driver separately (version 1.0.8 and 1.0.9b) using the standard gentoo
kernel sources.

8) With and without NPTL (I had NTPL enabled glibc installed until I read
about possible problems with it). I tried the LD_ASSUME_KERNEL work around
first and eventually even recompiled glibc with USE=-nptl.

9) Tried taking qjackctl out of the loop - running jackd manually - same
problem with ardour.

10) Recording all 18 channels with only one of the two multifaces configured
(tested both of them) works fine in all of the above configurations that I
tried it with - including without Ingo's RT patches.

I'm now totally lost. I've eliminated everything I can think of and don't know
what to try next. Any help would be greatly appreciated.

Thanks.

- Edwin

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