linux-kernel - Re: [PATCH 2/2] x86, perf: Use INST_RETIRED.PREC

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Date:	Tue, 1 Dec 2015 15:55:57 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	mingo@...nel.org
Subject: Re: [PATCH 2/2] x86, perf: Use INST_RETIRED.PREC_DIST for cycles:ppp

On Tue, Dec 01, 2015 at 06:54:14AM -0800, Andi Kleen wrote:
> On Tue, Dec 01, 2015 at 02:41:51PM +0100, Peter Zijlstra wrote:
> > On Mon, Nov 30, 2015 at 04:28:09PM -0800, Andi Kleen wrote:
> > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> > > index 9dfbba5..ba41899 100644
> > > --- a/arch/x86/kernel/cpu/perf_event.c
> > > +++ b/arch/x86/kernel/cpu/perf_event.c
> > > @@ -482,6 +482,9 @@ int x86_pmu_hw_config(struct perf_event *event)
> > >  			/* Support for IP fixup */
> > >  			if (x86_pmu.lbr_nr || x86_pmu.intel_cap.pebs_format >= 2)
> > >  				precise++;
> > > +
> > > +			if (x86_pmu.pebs_aliases)
> > > +				precise++;
> > 
> > This is not accurate, it would allow :ppp for core2 for example, which
> > does not at all support PREC_DIST events.
> > 
> > Something like so on top?
> 
> Yes that's fine. Thanks.
> 
> Are you just applying it with that change, or should I resend a combined patch?

Yep, got it in. Thanks.
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