Re: [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu

[Peter Zijlstra]

On Mon, 2011-07-04 at 23:57 +0200, Andi Kleen wrote:
> > > There are no NMIs without sampling, so at least the comment seems bogus.
> > > Perhaps the code could be a bit simplified now without atomics.
> > 
> > I'm not sure if uncore PMU interrupt need to be enabled for counting
> > only. What do you think?
> 
> Only for overflow handling to accumulate into a larger counter, but it doesn't 
> need to be an NMI for that.

Uncore is hooked into the regular PMI, and since we wire that to the NMI
the uncore will always be NMI too.

>   But it's not strictly required I would say, 
> 44(?) bits are probably enough for near all use cases.

44bits is in the hours range for pure cycle counts, which is so-so. I
bet you're going to be very annoyed when you find your counters are
wrecked after your 5 hour test run finishes.
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