Hi Nigel,

see below

Florian Schmidt wrote: 
On Thursday 04 October 2007, Nigel Henry wrote:

  
Ok, you have not done any irq priority tuning.. Try setting the IRQ-10
process [your emu10k1] to prio 90..
        
I'm not sure what I'm doing here. I presume I need to use chrt to change
the priority, but am not sure of the correct syntax. The current pid for
IRQ10 is 940.

Could you give me a line that will work for this pid, as the man page is
pretty hopeless with no examples, and about 3 hrs of googling turned up
virtually nothing.

Many thanks.

Nigel.

      
Flo
        
Bad to reply to my own post, but I've resolved the problem.
    

I never quite understood what was supposed to be bad about replying to one's 
own post.. :)

  
One xrun after 6m 33secs of 0.253 msecs, which is what I'm getting on
Fedora 7.
    

With soundcard irq prio at 90 [not shared with any other device], Jack prio at 
70 and all other irq prios at default 51?

Then it's either an application bug [are you running any applications]? Or a 
bug in the emu10k1 driver. Or in jackd, though i suppose that's rather 
unlikely..

  
Will that change of priority I've made for the soundcard on the current
pid, hold after a reboot?
    

Nope.. It will be started with the default prio again. Have a look at the 
rtirq script or fiddle your own initscript. Most distros have some "local" 
init script where you put that command..

Flo
Nigel,

This will tell you which IRQ your sound card is on:
cat /proc/interrupts | grep -i emu10k1

Then use this line to set the rtprio value (90 in this example) of that IRQ (obviously, replace the xx with your actual IRQ value).   Assuming this IRQ is stable across reboots, put this line in /etc/rc.local on Fedora systems.  Been working well here for a long time.
chrt -f -p 90 `pidof "IRQ-xx"`

If some shell scripting guru wants to jump in, I'm sure there is a way to connect these two lines so that the emu10k IRQ is found at boot time (so this removes the requirement that your sound card always gets the same IRQ).

HTH,
Rick