Re: [PATCH 2/2] perf_events: add event constraints support for Intel processors

Peter Zijlstra
2009-10-06T16:29:38Z

On Tue, 2009-10-06 at 16:42 +0200, Stephane Eranian wrote:

> This patch changes the event to counter assignment logic to take
> into account event constraints for Intel P6, Core and Nehalem
> processors. There is no contraints on Intel Atom. There are
> constraints on Intel Yonah (Core Duo) but they are not provided
> in this patch given that this processor is not yet supported by
> perf_events.

I don't think there's much missing for that, right?

I don't actually have that hardware, so I can't test it.

> As a result of the constraints, it is possible for some event groups
> to never actually be loaded onto the PMU if they contain two events
> which can only be measured on a single counter. That situation can be
> detected with the scaling information extracted with read().

Right, that's a pre existing bug in the x86 code (we can create groups
larger than the PMU) and should be fixed.

Patch looks nice though.