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

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Date:	Thu, 13 Jan 2011 18:14:19 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Lin Ming <ming.m.lin@...el.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

Lin,

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?

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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