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Date: Thu, 25 Nov 2010 22:10:02 +0100
Message-ID: <AANLkTimb_DR+c7BJMdN4QgdT_7WwRMixQGXaOFEwqDDt@mail.gmail.com>
Subject: Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu
From: Stephane Eranian <eranian@google.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Lin Ming <ming.m.lin@intel.com>,
        Ingo Molnar <mingo@elte.hu>, lkml <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Arjan van de Ven <arjan@infradead.org>
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On Thu, Nov 25, 2010 at 7:20 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> Yep, I see no reason to dis-allow sampling. Sure its hard to make sense
>> of it, but since there are people who offline all but one cpu of a
>> package,
>
> Assuming they don't have any active PCI devices either.
>
Good point.

>> I bet there are people who will run just one task on a package
>> as well.
>
> In that case the sampling has a 1/NUM-CPU-THREADS-IN-PACKAGE chance
> to report the right task (or actually somewhat less because the measurement
> skew for uncore is much higher than for normal events)
>
> Really for per core measurements using the OFFCORE events is much better.
>
yes, OFFCORE_RESPONSE is much more useful.
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