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Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs
From: Peter Zijlstra <peterz@infradead.org>
To: Lin Ming <ming.m.lin@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Frederic Weisbecker <fweisbec@gmail.com>,
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Date: Mon, 10 May 2010 12:18:28 +0200
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On Mon, 2010-05-10 at 18:11 +0800, Lin Ming wrote:
> On Mon, 2010-05-10 at 17:40 +0800, Peter Zijlstra wrote:
> > On Mon, 2010-05-10 at 17:27 +0800, Lin Ming wrote:
> > > Export pmus via sysfs /sys/devices/system/cpu/pmus/0...N
> > > The file name is the pmu id, ie, /sys/devices/system/cpu/pmus/N
> > > represents pmu id N.
> > > So perf tool can use it to initialize perf_event_attr. 
> > 
> > Why create a whole new directory, why not:
> > 
> >  /sys/devices/system/cpu/cpuN/pmu_id ?
> 
> 
> Do you mean /sys/devices/system/cpu/cpuN/pmu_id contain all ids?
> 
> For example, each cpu has 4 pmus and the file pmu_id shows something
> like,
> 
> #cat /sys/devices/system/cpu/cpu0/pmu_id
> 0 1 2 3

No, I'm assuming there is only 1 PMU per CPU. Corey is the expert on
crazy hardware though, but I think the sanest way is to extend the CPU
topology if there's more structure to it.

It simply doesn't make sense to have multiple PMU IDs on a single
topology entry, how would you choose?