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

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Message-Id: <1309870119.2381.6.camel@localhost>
Date:	Tue, 05 Jul 2011 20:48:39 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu

On Tue, 2011-07-05 at 19:22 +0800, Peter Zijlstra wrote:
> 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.

I'll add the interrupt handling code back.


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