Re: [RFC][PATCH 0/6] perf: x86 RDPMC and RDTSC support

[Peter Zijlstra]

On Wed, 2011-12-21 at 16:32 -0500, Vince Weaver wrote:

> * One, is it possible to detect at runtime that rdpmc() is supported?  
>   Maybe a field in the mmap'd buffer that can be read?

Ingo suggested a similar thing, will implement (although Christmas might
interfere with delivery timelines etc..).

> * Second, if I try a start / run 100M instructions / read
>   and measure retired instructions I get:
>       281474977711543 instructions
>   This is 0x10000000f45b7 which is 1<<48 + 100M.  I guess an artifact
>   of how the counters are set up?  Is it possible to have this start
>   at 0?  

Its supposed to be 0 based, clearly I messed up something and need to go
figure out what. Thanks for reporting.
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