Re: Latency tests with 2.6.12-rc1

Ingo Molnar
2005-03-22T08:22:38Z

* Lee Revell <rlrevell@joe-job.com> wrote:

> [...] Next I tried the same test but with JACK running. The longest
> latency reported was only 200 usecs, and I did not get xruns.
>
> Then, right after I stopped JACK, the latency tracer shot up to 1645
> usecs.
>
> So there seems to be a bug in the latency tracer where the timer is
> not being reset on reschedule. If an RT task like JACK is running,
> the task does wakeup properly and the counter is reset. But if JACK
> is not running then long latencies will be reported.

hm, weird, and i have no solution for this yet. But i just found a
related bug in the -RT patch in that it reverted a latency breaker in
the ext3 path that your trace shows - affecting PREEMPT_DESKTOP. Could
you try the 40-03 patch i just uploaded (assuming it's stable for you
otherwise ...) and see whether you can still reproduce these latencies?
(if yes then please also send me a full trace via private mail, or bzip
-9 it in your public mail.)

Ingo