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Subject: Re: [PATCH 0/4] perf: Intel uncore pmu counting support
From: Lin Ming <ming.m.lin@intel.com>
To: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
        Andi Kleen <andi@firstfloor.org>,
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        linux-kernel <linux-kernel@vger.kernel.org>
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Date: Fri, 01 Jul 2011 13:49:14 +0800
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On Thu, 2011-06-30 at 20:10 +0800, Stephane Eranian wrote:
> On Thu, Jun 30, 2011 at 10:09 AM, Lin Ming <ming.m.lin@intel.com> wrote:
> > Hi, all
> >
> > I posted uncore patches months ago, but it was pended due to an uncore
> > interrupt problem.
> >
> > This series are cut to support uncore pmu counting only.
> > So uncore interrupt handling is not needed.
> >
> You're making the assumption that when counting, you can never construct
> a measurement that will cause a counter to overflow the 39 bits. If not, then
> you need interrupt handling even when counting.

Is it enough to get the delta when overflow like below?

        unsigned int a = 0xfffffffe;
        unsigned int b = 10;
        unsigned int delta = (int)b - (int)a;

> 
> 
> > The uncore pmu type is allocated dynamically and exported via sysfs.
> > $ cat /sys/bus/event_source/devices/uncore/type
> > 6
> >
> > You can count uncore raw events as below,
> > $ perf stat -e uncore:r0101 ls
> >
> > It reads uncore pmu type id from sysfs to setup perf_event_attr::type.
> >
> > Comments are appreciated.
> >
> > Thanks,
> > Lin Ming
> >
> >