linux-kernel - Re: [PATCH 1/1] perf/x86/intel: Add perf core PMU support for Intel Knights Landing

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Message-ID: <20151208083757.GD6356@twins.programming.kicks-ass.net>
Date:	Tue, 8 Dec 2015 09:37:57 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Harish Chegondi <harish.chegondi@...el.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com,
	Harish Chegondi <harish.chegondi@...il.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Kan Liang <kan.liang@...el.com>,
	Lukasz Anaczkowski <lukasz.anaczkowski@...el.com>
Subject: Re: [PATCH 1/1] perf/x86/intel: Add perf core PMU support for Intel
 Knights Landing

On Mon, Dec 07, 2015 at 02:28:18PM -0800, Harish Chegondi wrote:
> Knights Landing core is based on Silvermont core with several differences.
> Like Silvermont, Knights Landing has 8 pairs of LBR MSRs. However, the
> LBR MSRs addresses match those of the Xeon cores' first 8 pairs of LBR MSRs


> +/* Knights Landing */
> +void intel_pmu_lbr_init_knl(void)
> +{
> +	x86_pmu.lbr_nr	   = 8;
> +	x86_pmu.lbr_tos    = MSR_LBR_TOS;
> +	x86_pmu.lbr_from   = MSR_LBR_NHM_FROM;
> +	x86_pmu.lbr_to     = MSR_LBR_NHM_TO;
> +
> +	x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
> +	x86_pmu.lbr_sel_map  = snb_lbr_sel_map;

Also, unlike Silvermont, this thing seems to have hardware LBR filters.
So would it not be more accurate to say the KNL has a big core LBR
instead? (Note that this LBR setup isn't specific to Xeon's, all of the
Core chips have this, including the client parts).

> +	pr_cont("8-deep LBR, ");
> +}
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