Re: [rc8] Regression: key repeats and skips in music during compilation

Ingo Molnar
2008-04-08T13:54:30Z

* Frans Pop <elendil@planet.nl> wrote:

> > and a more laborous way would be to trace such skipping:
> > http://people.redhat.com/mingo/sched-devel.git/howto-trace-latencies.txt
>
> Tried this too, but the problem is that the skips don't happen while
> tracing is enabled. Apparently the system overhead is so high that it
> changes the scheduling behavior. Attached one trace that was made
> immediately after a skip happened. Maybe it helps.

one way to reduce tracing overhead would be:

echo nostacktrace > /sys/kernel/debug/tracing/iter_ctrl
echo nosched-tree > /sys/kernel/debug/tracing/iter_ctrl

and making sure you only have CONFIG_CONTEXT_SWITCH_TRACER=y enabled,
not any of the other tracers.

but ... if there's a narrow wakeup race, even lightweight tracing could
make it go away.

Ingo