linux-kernel - Re: [RFC PATCH 2/3 v3] perf: Implement Nehalem uncore pmu

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Date:	Mon, 17 Jan 2011 09:29:29 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3 v3] perf: Implement Nehalem uncore pmu

On Fri, 2011-01-14 at 01:14 +0800, Stephane Eranian wrote:
> Lin,

Hi, Stephane, 

Sorry for late response, I'm just back from vacation.

> 
> On Thu, Dec 2, 2010 at 6:20 AM, Lin Ming <ming.m.lin@...el.com> wrote:
> > +static void uncore_pmu_enable_all(int nmi_core)
> > +{
> > +       u64 ctrl;
> > +
> > +       ctrl = ((1 << UNCORE_NUM_GENERAL_COUNTERS) - 1) | MSR_UNCORE_PERF_GLOBAL_CTRL_EN_FC0;
> > +
> > +       /* Route all interrupts to the first core that accesses uncore */
> > +       ctrl |= 1ULL << (48 + nmi_core);
> > +
> > +       wrmsrl(MSR_UNCORE_PERF_GLOBAL_CTRL, ctrl);
> > +}
> 
> Are you sure nmi_core is always between 0-3 on a 4-core system and 0-5
> on a 6-core system?
> In other words, is that what topology_core_id(raw_smp_processor_id()) returns?

I just have a look at a 6-core system, the core id is not 0-5

$ cat /proc/cpuinfo |grep "core id"
core id		: 0
core id		: 1
core id		: 2
core id		: 8
core id		: 9
core id		: 10

So we'd better route all the interrupts to the first core of the socket.

Thanks for the catch.
Lin Ming

> 
> Note that, unfortunately, I have not seen documentation that says on
> 6-core system
> UNC_GLOBAL_CTRL has 6 interrupt target bits, but it would make sense.
> 
> 
> Otherwise, you will get a kernel panic when you wrmsr UNC_GLOBAL_CTRL.
> 
> > +
> > +       if (uncore->n_events == 1) {
> > +               nmi_core = topology_core_id(raw_smp_processor_id());
> > +               uncore->nmi_core = nmi_core;
> > +               uncore_pmu_enable_all(nmi_core);
> > +       }


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