[LAU] RT patch not needed for new kernels (?)

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Wed Nov 26 18:45:45 EST 2008

On Thu, 2008-11-27 at 00:07 +0100, Grammostola Rosea wrote:
> Hi,
> There are some rumors about the lack of need for an RT patch with new 
> kernel, after 2.6.26.xx for making (realtime) music on GNU/Linux.
> What is true about this?

And were did you hear those "rumors"? Source? URL? etc?

As usual, it depends. What does "realtime" mean to you? 

Very low latencies?[*] Then you _will_ need the realtime preemption
patches or you will have to live with xruns. Not so low latencies?
Vanilla kernels > 2.6.26 will probably work just fine. 

It also depends on what hardware mixture you have on your computer and
how it is (or is not) tuned. 

A caveat is that the realtime preemption patches for 2.6.26.x don't seem
to work too well (midi problems when used with external controllers).
And for 2.6.27.x there is nothing even usable yet (last time I looked).
The latest "stable" preemption patches are for 2.6.24.x, which is
regretfully now too old for many hardware configurations (and even for
some software, like the newer X servers). 

In both cases you will need a working Jack and you will need to run it
with realtime priority (which has nothing to do with the realtime
preemption patches). 

Hmmm, so am I now perpetuating the rumor? :-)
-- Fernando

[*] 5-10 mSecs? There is no hard boundary...

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