[Fedora-music-list] CCRMA kernel in FC5?

[Callum Lerwick]

On Sat, 2006-05-20 at 20:56 -0700, thewade wrote:
> As far as I know the realtime kernel module, sometimes called the LSM 
> module, is not a part of the mainline Fedora Core kernel(s). Is it now? 
> It used to require a PAM patch and I think a rebuild of the kernel.

From what I remember reading in Kernel Traffic, upstream didn't like the
LSM approach. They came up with the rlimit approach instead, which has
been merged upstream and is supported in FC5. That's what we're using in
jack's README.Fedora.

> If I wasn't doing realtime stuff then I would probably agree with you.

How low do you need to go?

On my Athlon 64 3000+ system, I can run jack reliably at a period size
of 256, on the motherboard's cheezy onboard sound. Any lower and it
overruns like mad. Which makes sense, according to qjackcontrol that's a
latency of 10.7ms at 48khz. Given the stock kernel has a 250hz timer,
that gives you a nyquist scheduling frequency of 125hz, which is a
period of 8ms. With a stock kernel I don't think we can go any lower
than 8ms.

I think that's probably good enough for most users. Maybe CCRMA can
continue to supply kernels for those who demand more. Now if only I
could get Rosegarden to stop complaining...

Packaging alternative kernels in Extras is a can of worms I don't think
anyone is in a rush to open. But as far as I know its not yet totally
out of the question...
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