linux-kernel - Re: [patch V2 26/28] x86/perf/intel/rapl: Convert it to a per package facility

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Date:	Mon, 22 Feb 2016 17:04:36 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Borislav Petkov <bp@...en8.de>,
	Stephane Eranian <eranian@...gle.com>,
	Harish Chegondi <harish.chegondi@...el.com>,
	Kan Liang <kan.liang@...el.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [patch V2 26/28] x86/perf/intel/rapl: Convert it to a per
 package facility

On Mon, Feb 22, 2016 at 04:52:28PM +0100, Thomas Gleixner wrote:
> On Mon, 22 Feb 2016, Peter Zijlstra wrote:
> 
> > On Mon, Feb 22, 2016 at 11:07:02AM -0000, Thomas Gleixner wrote:
> > > +static inline struct rapl_pmu *cpu_to_rapl_pmu(unsigned int cpu)
> > > +{
> > > +	return rapl_pmus->pmus[topology_logical_package_id(cpu)];
> > > +}
> > 
> > > @@ -370,6 +378,7 @@ static int rapl_pmu_event_init(struct pe
> > >  		return -EINVAL;
> > >  
> > >  	/* must be done before validate_group */
> > > +	pmu = cpu_to_rapl_pmu(event->cpu);
> > >  	event->cpu = pmu->cpu;
> > >  	event->pmu_private = pmu;
> > 
> > This again looks like pmu_private is 'trivially' replacable with
> > something like:
> > 
> > static inline struct rapl_pmu *event_to_rapl_pmu(struct perf_event *event)
> > {
> > 	return cpu_to_rapl_pmu(event->cpu);
> > }
> 
> Yes, it is. But that's 3 loads versus 1 and we have that in the perf fastpath,
> so I prefer to keep the pmu_private add on.

OK, fair enough.