Re: [tip:perf/core] perf/x86: Use INST_RETIRED.PREC_DIST for cycles: ppp

From: Peter Zijlstra
Date: Tue Dec 08 2015 - 08:28:10 EST


On Tue, Dec 08, 2015 at 09:57:07AM +0100, Peter Zijlstra wrote:
> On Tue, Dec 08, 2015 at 09:50:26AM +0100, Peter Zijlstra wrote:
> > On Tue, Dec 08, 2015 at 06:36:04AM +0100, Ingo Molnar wrote:
> >
> > > So I checked my NHM box with your latest queue and it now works correctly. Do you
> > > have any idea what the difference is/was?
> >
> > Sadly, no clue :/
> >
> > I went over those patches and cannot find anything that should affect
> > NHM (or <=SNB in fact).
>
> Oh wait, I spoke too soon, the two new patches affect everything with
> PEBS. And esp. the latter one:
>
> lkml.kernel.org/r/1449177740-5422-2-git-send-email-andi@xxxxxxxxxxxxxx
>

If that is the patch that makes your NHM go again, then running 2
concurrent perf-top sessions should make it all go dark again.
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