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Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs
From: Lin Ming <ming.m.lin@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Frederic Weisbecker <fweisbec@gmail.com>,
       "eranian@gmail.com" <eranian@gmail.com>,
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       Corey Ashford <cjashfor@linux.vnet.ibm.com>,
       "arjan@linux.intel.com" <arjan@linux.intel.com>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       Paul Mackerras <paulus@samba.org>,
       "David S. Miller" <davem@davemloft.net>,
       Russell King <rmk+kernel@arm.linux.org.uk>,
       Paul Mundt <lethal@linux-sh.org>, lkml <linux-kernel@vger.kernel.org>
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Date: Mon, 10 May 2010 18:11:53 +0800
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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

....

#cat /sys/devices/system/cpu/cpuN/pmu_id
0 1 2 3

> 
> That way we can simply extend it to things like:
> 
>  /sys/devices/system/cpu/cpuN/nodeN/pmu_id
>  /sys/devices/system/node/nodeN/pmi_id
> 
> Instead of having to add something like:
> 
>  /sys/devices/system/node/pmus/0..N
> 
>