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Subject: Re: Performance counter API review was [patch] Performance
 Counters for Linux, v3
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Mackerras <paulus@samba.org>
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Date: Wed, 04 Feb 2009 11:51:44 +0100
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On Wed, 2009-02-04 at 21:47 +1100, Paul Mackerras wrote:
> Peter Zijlstra writes:
> 
> > How is smp_call_function() going to help here? You still need to pull
> > all that data through that one FD. That's a cacheline bounce fest.
> 
> Well, let's put this into perspective.  We would be collecting 8 bytes
> of data from each CPU.  Hardly a "cacheline bounce fest". :)

Ah, I was thinking more of the event triggered profiling, like NMI time,
cachemiss or pagefault profiling.

In those cases you'd get a continuous stream of data for each cpu, at
possibly quite high speeds.