[linux-audio-user] Trouble with 2.15.19/20 kernel

Bill Allen lau at ballen.fastmail.fm
Sat Apr 8 13:22:45 EDT 2006

Lee Revell wrote:
> On Fri, 2006-04-07 at 16:58 -0400, Bill Allen wrote:
>> I'll try to do as you suggest. As I understand it (which could be not
>> at all) Dapper doesn't support realtime-lsm in any of those kernel
>> builds. It uses Rlimits-Aware PAM. I've added myself to the audio
>> group and as I mentioned, jack works great in 2.6.15-18, but in *-19,
>> and *-20 it's miserable. 
> OK that's a kernel bug of some kind - can you please report it to
> Ubuntu?  There should not be too many changes between those point
> releases.
> Lee

I found that if I increase the number of periods to 3 that the xruns on 
startup don't happen. Thus, using:

/usr/bin/jackd -R -dalsa -dhw:0 -r44100 -p512 -n3

I was able to bring up qsynth and attach vkeybd and play some notes no 
problem. But, when I launched jack rack and loaded a rack with a couple 
of the CAPS amp/cabinet simulation plugins, all hell broke loose. Even 
with a buffersize of 2048 and 4 periods (-p2048 -n4), loading the rack 
caused way too many hard xruns.

On 2.6.15-18-686, I'm running jack with:

/usr/bin/jackd -R -dalsa -dhw:0 -r44100 -p512 -n2

with no problems at all.

I'm trying to think of what could have regressed in the newer kernel 
builds that would explain this behaviour?


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