5 Oct
2007
5 Oct
'07
3:09 p.m.
On Thu, 2007-10-04 at 12:15 -0700, thomas fisher wrote:
I can supply no quantifications for the 32 bit
2.6.20-16-realtime kernel in
ubuntustudio other than no xruns have been observed. With the low latency
kernel, xruns were observed.
Do you remember by any chance which version of the rt patched kernel was
giving you trouble? There was a mainline kernel bug which created a lot
of problems from 2.6.18 onwards and was fixed in January 2007 (I could
not update to that one, or later versions till the problem was
fixed[*]).
Jack is the only app that has a -20 priority
assigned. The general workstation has been running without fault. The general
Debian / Ubuntu philosophy tends towards system stability.
If you found a setup that works by all means stick to it! The list below
is only indicative, I have found the rt patched kernel to be better but
I don't have the exact same setup you have. There are many things that
have to be just right for everything to work fine, and of course it also
depends on how low are the latencies used (I routinely work at 2x128 and
also 64x2 - the default Jack 1024x2 is less problematic of course).
-- Fernando
[*] http://lkml.org/lkml/2007/1/5/291
On Wednesday 03 October 2007 14:54:32 Fernando
Lopez-Lezcano wrote:
On Wed, 2007-10-03 at 18:39 +0200, Frank
Barknecht wrote:
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http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-user Hallo,
Matthias Schönborn hat gesagt: // Matthias Schönborn wrote:
To further clarify (or confuse?) the issue, how "low latency" the kernel
is also depends on how you configure the kernel build options before or
after patching the kernel with Ingo's patch. For Ingo's patch
CONFIG_PREEMPT_RT is the best option in terms of latency but there are
others (CONFIG_PREEMPT_DESKTOP) that have a more conservative approach
but have (relatively speaking) higher latencies. So from worst to best
it would be something like:
vanilla linuz + CONFIG_PREEMPT_NONE
vanilla + CONFIG_PREEMPT_VOLUNTARY (used by the stock Fedora kernel)
vanilla + Ingo + CONFIG_PREEMPT_DESKTOP
vanilla + Ingo + CONFIG_PREEMPT_RT (the one I use for Planet CCRMA)
(there's more granularity and options in the CONFIG_PREEMPT* world but
those are the ones that have the biggest impact as far as I can
remember)
-- Fernando
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http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-user I've just read that there's a difference
between a realtime-kernel and
the low-latency-kernel provided by ubuntustudio. The text in the german
wiki on ubuntuusers.de said, that a realtime-kernel is slightly better
than the lowlatencykernel (http://wiki.ubuntuusers.de/Echtzeitkernel) -
then why isn't it used in ubuntustudio? Or do I just mix something up?
I think, this wiki and maybe Ubuntustudio as well are using a very
confusing terminology.
Generally we have two kinds of kernels: The "vanilla" kernel as
downloadable on kernel.org and the same kernel, but patched with Ingo
Molnars RT-patches. The vanilla kernel, if configured properly with
CONFIG_PREEMPT etc., already gives very good performance in the low
latency department, enough for many users, even audio users. I run one
of these.
If you want more, then you can install a RT-patched kernel, as is
provided in the linux-rt or linux-realtime packages. I would call the
Ingo-Molnar-patched kernels Realtime-Kernels or Low-Latency-Kernels.