[CentOS] low latency kernel?

Lamar Owen
Thu, 02 Apr 2015 15:16:59 -0000

On 04/02/2015 10:46 AM, Les Mikesell wrote:
> Someone recently posted on the x2go list that he had a problem with
> jerky videos playing remotely on Ubuntu, but solved it by installing a
> low latency kernel that was available as an alternative.  That made me
> curious as to whether CentOS has an equivalent - or a way to build
> something similar.
>
You want the kernel-rt package.  This is a part of the MRG packaging.
The source RPM for the latest version for EL6 is at
ftp://ftp.redhat.com/redhat/linux/enterprise/6Server/en/RHEMRG-RHEL6/SRPMS/kernel-rt-3.10.58-rt62.60.el6rt.src.rpm
(and while looking in this area, I found some very interesting things in
the 7 trees......).  I don't see a kernel-rt package in any of the C7
repos, but sources are in the kernel-rt git at git.centos.org.  Just
need to build it and its dependencies. Karanbir, Johnny, et al: are
there any plans to build this at some point?

And then you'll want to read
https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO as the RT
preemptable kernel has some differences in behaviors you need to be
aware of.

I have used the RT_PREEMPT kernel, when dealing with multitrack audio
setups where you need to do overdubbing and punchins/outs. Every
millisecond counts when you have a musician or vocalist listening to a
mix of 16 tracks, their own previously recorded track, and they need to
punch in and perform (with pre-roll) a new take of a section then punch
out to return to the previously recorded material.

Currently I use AVLinux for that task, but CentOS 7 plus the RT kernel
(with all the tools needed for said kernel) would be fantastic; the
software I use, Harrison Consoles' Mixbus (based on Ardour), runs very
well on C7, but the latency is a bit too high (and far too
nondeterministic thanks to clock scaling) for 16 channel overdubs with
punchins/outs.  AVLinux works well for this.

Years ago, the way to get this on Red Hat Linux and later Fedora and
CentOS was to install the kernel-rt from PlanetCCRMA; it's been a while
since I looked for it there.  But Red Hat has the MRG product.