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Date: Fri, 26 Nov 2010 12:25:51 +0100
Message-ID: <AANLkTika3r2=gCh4nX-raRU3BoFpWMUEapn3w2bgyGAd@mail.gmail.com>
Subject: Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu
From: Stephane Eranian <eranian@google.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Lin Ming <lin@ming.vg>, Lin Ming <ming.m.lin@intel.com>,
        Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Arjan van de Ven <arjan@infradead.org>
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On Fri, Nov 26, 2010 at 12:24 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Fri, 2010-11-26 at 09:18 +0100, Stephane Eranian wrote:
>
>> In the perf_event model, given that any one of the 4 cores can be used
>> to program uncore events, you have no choice but to broadcast to all
>> 4 cores. Each has to demultiplex and figure out which of its counters
>> have overflowed.
>
> Not really, you can redirect all these events to the first online cpu of
> the node.
>
> You can re-write event->cpu in pmu::event_init(), and register cpu
> hotplug notifiers to migrate the state around.
>
I am sure you could. But then the user thinks the event is controlled
from CPUx when it's actually from CPUz. I am sure it can work but
that's confusing, especially interrupt-wise.
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