Re: [PATCH 4/6] kvm tools: Add rwlock wrapper

Ingo Molnar
2011-05-27T11:24:59Z

* Ingo Molnar <mingo@elte.hu> wrote:

> Note that you do not want the context switch event, but the CPU
> migration event: that will notify user-space when it gets migrated
> to another CPU. This is the case that RCU really needs.

Also note that the main current use-case of perf events is
instrumentation, thus if you make use of this facility for user-space
RCU you need to check whether the events are all precise and arrive
in time to the target process, etc.

Statistical behavior isnt a big problem for instrumentation but it's
a showstopper for RCU, obviously! :-)

If you find such bugs then we want to fix them, so there's no
fundamental *desire* from us for these events to be statistical and
inaccurate anywhere.

Thanks,

Ingo