Re: [linux-audio-dev] Re: POSIX caps/realtime/root processes - Linux-audio-dev

28 Nov 2003

Roger Larsson:
...
     So how is the
low-latency situation for 2.6? I did install 2.6 on
 my private machine, but was not able to get better performance
 than 2.4 with ll+pre (kicked out of jack-graph pretty soon with 128
 frames period). Is there a trick to get better lowlatency performance
 with 2.6 I don't know about? 
 Did you compile with CONFIG_PREEMPT enabled? 
 Yes. :) 
 echo 1 > /proc/sys/kernel/lowlatency ?
 If you have enabled "Control low latency with sysctl"
 I didnt know there were an option for lowlatency for 2.6?
However, I do remember there were no /proc/sys/kernel/lowlatency
file. Have to check when I get home.

...
  It might be possible that something like lock break is
needed...

 Lots of good stuff is available at:
 	http://www.tech9.net/rml/linux/
 But most are for 2.4 or early 2.5 kernels
 I couldn't find a lock-break patch for 2.6 there, and the other
one that might might have helped, the Scheduler Hints patch, was
not very updated. But I think I remember reading about setting
various kinds of scheduler-behaviour by using a kernel option?
Could that make the situation better?

This is a bit irritating, because in 2.4.23-pre8+ll+pre I can
run with a frame size of 32 in jack and run ardour for a very
long time without being kicked, and have very few xruns.
With 2.6.0-pre4 I cant even run with 128 for more than a minute or so,
and I get lots of xruns before that.

My machine is nforce2, xp2800, using the built in soundcard,
built-in gfx card, ps2 mouse+keyb., and no pci or agp slots used.

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