Re: preemption and rwsems (was: Re: missing madvise functionality)

Ingo Molnar
2007-04-05T19:11:40Z

* David Howells <dhowells@redhat.com> wrote:

> But short of recording the lock sequence, I don't think there's anyway
> to find out for sure. printk probably won't cut it as a recording
> mechanism because its overheads are too great.

getting a good trace of it is easy: pick up the latest -rt kernel from:

http://redhat.com/~mingo/realtime-preempt/

enable EVENT_TRACING in that kernel, run the workload
and do:

scripts/trace-it > to-ingo.txt

and send me the output. It will be large but interesting. That should
get us a whole lot closer to what happens. A (much!) more finegrained
result would be to also enable FUNCTION_TRACING and to do:

echo 1 > /proc/sys/kernel/mcount_enabled

before running trace-it.

Ingo