On Tuesday, January 10, 2012 09:28:12 AM Jeremy Jongepier did opine:
On 01/10/12 01:07, Diego Simak wrote:
If that kernel is not suitable for you (I mean,
you get a lot of
xruns), then you can use the PREEMPT or RT Kernels that are included
in the Official Ubuntu Repositories (which are configured in the apt
sources automatically) and see how it works before going to a manual
kernel compillation.
10.04 does have a real-time kernel in the repos, 2.6.31-rt.
This isn't exactly realtime, where latencies measured in small numbers of
microseconds count big time. Over on the emc list, where we depend on
being able to feed stepper motors with very steady heartbeats to keep them
running smoothly at high speeds, we have found a motherboard with extremely
low latencies, like 7 microseconds without resorting to the use of the
isolcpus= boot param, and with it, figures in the 5 microsecond range have
been seen.
This is on a dirt cheap intel D-525 motherboard, with a dual core 1.8 ghz
atom cpu on it, doesn't even need a fan! I just bought the whole box with
2Gb of ram, a 250Gb Sata HD and a sata dvd writer for $246 delivered to my
front deck.
Because emc is a special build, running only on an RTAI enabled kernel, we
are stuck with a 2.6.32 kernel that comes with ubuntu-10.04 LTS, but I just
saw where next LTS is already committed to a 3.2 kernel.
But the
2.6.33 real-time kernel from Tango Studio is superior. At least, I
didn't have a lot of success with the real-time kernel from the Ubuntu
repos while the one from Tango Studios is still going strong.
Later versions of Ubuntu do not have a real-time kernel available
anymore, only via PPA's. But indeed, with the whole IRQ threading thing
being merged in the mainline kernel you could ask yourself, do I really
need a real-time kernel. In my case I dare to say yes, haven't done any
A-B testing with a low-latency kernel but I get the feeling that I can
get the most out of a real-time kernel. That's why I'm thinking about
switching to Arch but unfortunately the 3.0 real-time kernel is not
stable enough (it crashes on any plug-in that uses the Juce framework,
need to file a bugreport).
Get it filed then. The quicker its filed, the quicker it will get fixed
(if its not Juce's fault that is.)
Best,
Jeremy
Cheers, Gene
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
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There's got to be more to life than compile-and-go.