Re: preemption and rwsems (was: Re: missing madvise functionality)
From: Ingo Molnar
Date: Thu Apr 05 2007 - 15:11:55 EST
* David Howells <dhowells@xxxxxxxxxx> 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
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