[linux-audio-user] alsa rme96 jack - 186 msec latency?

[Michael Rudolf]

On Friday 09 September 2005 03:10, Eric Dantan Rzewnicki wrote:  
> On Thu, Sep 08, 2005 at 08:01:16PM -0500, Reuben Martin wrote:
[..]
> > I've run jack with reduced number of periods without any problem.
> > You're output lookes like you have issues elsewhere though to fix
> > before worrying about the numer of periods you use. The xruns,
> > messages about interrupt delays, and driver messages suggest you have
> > problems that need fixed berfore jack will ever work well, reguardelss
> > of the number of periods you use.
[..]
> > I don't know enough to comment on h/w design or driver design, I just
> > know I've been able to use JACK with this driver at very low latencies
> > without X-Runs.
> > If I can help in providing specific info, let me know. :)
>
> And if there are any specific problems with the drivers, let me know as
> we have so many I'm sure management could be persuaded to let us spend
> some time testing, debugging and fixing stuff.

This mailing list is amazing. Thanks for all the info; it sounds promising.

This is my configuration again:
Sound Driver:3.8.1a-980706 (ALSA v1.0.9b emulation code)
Kernel: 2.6.12-oci2.mdk with realtime lsm module and 
PREEMPT/PREEMPT_BKL enabled. Distribution is PCLinuxOS P91 fully updated 
and with the Jack packages from thac 
(jackit-0.100.1-050708.1.pclo2005.thac).

>From what I have read by now, it seems that preempt and realtime is not 
enough; what I'd need would be "realtime preemption", as in a single patch 
by Ingo Molnar (http://people.redhat.com/mingo/realtime-preempt/). I also 
seem to be missing the "chrt" tool to change interrupt priorities, and 
don't know yet where to obtain that.

Eric and Reuben, are you both running 2.6.13 with said patch and the chrt 
tool?

Another point is shared memory; I have that enabled in the kernel, I have a 
tmpfs mounted on /dev/shm, and Jack is compiled with support ("JACK 
compiled with System V SHM support."), but I have read that Jack uses /tmp 
for pipes per default, and I can in fact see some 
in /tmp/jack-[uid]/default/. Now /tmp is a normal ext3 file system here, 
not a tmpfs. Could that alone be the problem?

Michael