[Fedora-music-list] Low Latency vs. Real Time Kernel - actual latencies ?

[Fernando Lopez-Lezcano]

On 02/16/2012 04:33 AM, David Timms wrote:
> On 15/02/12 16:49, Brian Monroe wrote:
>> On Tue, Feb 14, 2012 at 12:21 PM, Brendan Jones
>> <brendan.jones.it at gmail.com>wrote:
>>> Latency times are really relative things based on many factors. Have you
>>> been getting better latency times than ta
>>>
>> yeah.
>
> I would be good to see real numbers associated with claims like the
> above; also how it is measured..

Cyclictest is widely used for measuring latencies:
   https://rt.wiki.kernel.org/articles/c/y/c/Cyclictest.html

> Also, indicate those various kernel patches and or options they use or
> have tested.

The rt patches for the latest kernels (3.2 at this point) are here:
   http://www.kernel.org/pub/linux/kernel/projects/rt/3.2/

This is pretty much all I add to the rt patched kernels for Fedora (with 
the proper configuration options, of course, I'm attaching the extra 
options I'm currently using). To get the best performance in the Jack 
world you need to tune the irq kernel thread priorities, that is usually 
done using rtirq (http://www.rncbc.org/jack/#rtirq), and of course jackd 
should run with the proper rt priority as well.

-- Fernando
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