[LAU] Are RT-patches needed anymore? (Was Re: >= 2.6.27 RT ETA?)

James Stone jamesmstone at gmail.com
Tue Jan 27 08:18:21 EST 2009


On Tue, Jan 27, 2009 at 1:06 PM, Peder Hedlund <peder at musikhuset.org> wrote:
> Quoting Ken Restivo <ken at restivo.org>:
>
>> And here is the next installment in the saga of trying to get Ingo
>> RT going on my Asus EEE.
>>
>> I successfully built and ran the 2.6.26.8-rt12 with the alsa_seq
>> patch. It ran.
>>
>> The problem is that neither the Ethernet (atl1e) or wireless
>> (rt2860sta) work. So I pretty much had to reboot back out of it
>> immediately.
>
> I've been running the standard kernel from openSUSE 11.0 on my Athlon
> 2000+ and can get down to at least 5.3ms latency on an Audiophile 2496
> using the limits.conf "trick".
>

limits.conf is just to give users access to realtime capabilities. As
I understand it, the rt patch makes changes to the kernel to give
lower realtime speeds through alterations in the way preemption is
handled (my very non-technical understanding). So, they are doing
different things.

That being said, I agree, for normal hobbyist computer music, I have
found a standard debian kernel to give perfectly adequate performance
(of course as long as the user has access to realtime capabilities).

I think it is possible to get a bit obsessional about getting the
lowest possible latency. IIRC I think I read that standard hardware
midi keyboards have a latency of around 10ms, and mechanical organs
can have even more latency?? So, I think it is more a matter of
technique.

With live recording, having a "blip" marker (very technical!! LOL) at
the beginning of each track to line up each recorded track post-hoc
seems to help too, even with very long latencies.

James



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