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Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Lin Ming <ming.m.lin@intel.com>,
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Date: Tue, 11 May 2010 11:24:37 +0200
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On Tue, 2010-05-11 at 11:18 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > The new PMUs will use a dynamic range that starts at PERF_TYPE_MAX.
> 
> I dont think we should use a dynamic range of event sources - it's a 
> completely useless indirection that has no meaning to humans.
> 
> As far as machine interfaces go a much cleaner approach would be to allow an 
> open fd to a sysfs file to be passed to sys_perf_event_open() - this would 
> identify the event source. This needs a small extension of the ABI but we 
> could thus get rid of the 'type' enumeration altogether and express _all_ 
> event sources via fds to sysfs files.

Whatever, that's almost identical. What we can do is reserve
perf_event_attr::type with bit 31 set for fd's and use the fd->file
lookup instead of the type->pmu lookup.