Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain supportto use NMI-safe methods

[Avi Kivity]

On 06/15/2009 10:10 PM, Peter Zijlstra wrote:
> > But one thing is sure: it is certainly going to be faster than the
> > INVLPG(s!) we have to do with the GUP solution.
> >      
>
> Sure, but we only pay that price when we do the callchain bit, not on
> every NMI.
>    

You can read cr2 on nmi entry and nmi exit, and only write it if it has 
changed (if it turns out that writing cr2 is expensive; ISTR that it isn't).

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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