Lowlatency kernel testing (Re: A feature for -lowlatency kernel?)

ailo ailo.at at gmail.com
Fri Apr 1 19:49:55 UTC 2011

I'm not sure how to catch the output.
I'm not getting any messages to the root shell. Am I supposed to?

I'm testing the 2.6.38-7 -generic, and it is in fact working better than
before. Almost as well as -lowlatency.

On 04/01/2011 03:36 AM, David Henningsson wrote:
> On 2011-03-25 05:21, ailo wrote:
>> I've been doing some testing on previous kernels together with a few
>> people, and the sum of my experience is, just use jack with a program
>> you like, try using the lowest latency you can.
> Hi ailo,
> I see you're the only one that has updated the wiki with info saying
> that lowlatency kernel actually gives you lower latency than the generic
> kernel.
> I'm a little curious as of what is causing this. Could you please try
> the following:
> - Start the latest generic kernel
> - Start your audio programs (jack etc) and verify that the latency is
> still not ok/optimal. Set your latency settings to the latency that you
> are able to achieve successfully with the lowlatency kernel, but gives
> you xruns in the generic kernel.
> - Run the following commands:
> sudo -s
> cd /sys/kernel/debug/tracing
> echo 0 > tracing_enabled
> echo wakeup_rt > current_tracer
> echo 1 > tracing_enabled
> - While in that root shell, wait for an xrun, then attach the output of
> the "trace" file here. For the trace file to be of the most use, it
> should contain a latency value of ms (as in milliseconds rather than
> microseconds), and the task should be "jackd".
> You can then
> echo nop > current_tracer
> ...to disable the tracer again, as it might take some additional CPU.
> Thanks!


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