linux-kernel - Re: [Patch v1 04/10] perf/x86: add memory profiling via PEBS Load Latency

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Date:	Mon, 29 Oct 2012 16:35:05 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, ak@...ux.intel.com,
	acme@...hat.com, jolsa@...hat.com, ming.m.lin@...el.com
Subject: Re: [Patch v1 04/10] perf/x86: add memory profiling via PEBS Load
 Latency

On Mon, 2012-10-29 at 16:15 +0100, Stephane Eranian wrote:
> +static u64 load_latency_data(u64 status)
> +{
> +       union intel_x86_pebs_dse dse;
> +       u64 val;
> +       int model = boot_cpu_data.x86_model;
> +       int fam = boot_cpu_data.x86;
> +
> +       dse.val = status;
> +
> +       /*
> +        * use the mapping table for bit 0-15
> +        */
> +       val = pebs_data_source[dse.ld_dse];
> +
> +       /*
> +        * Nehalem models do not support TLB, Lock infos
> +        */
> +       if (fam == 0x6 && (model == 26 || model == 30
> +           || model == 31 || model == 46)) {
> +               val |= P(TLB, NA) | P(LOCK, NA);
> +               return val;
> +       }

I'm so 100% sure we'll forget to add a nhm model number if we ever find
we missed one.

Could we either add a classification enum to x86_pmu that is set in the
big model switch on init, or do this with your new constraints flags,
where we have a different flag for NHM_LL vs SNB_LL or so?

Or if all else fails, add a quirk to the Intel Debugstore bits bitfield,
something like pebs_ll_nhm.

> +       /*
> +        * bit 4: TLB access
> +        * 0 = did not miss 2nd level TLB
> +        * 1 = missed 2nd level TLB
> +        */
> +       if (dse.ld_stlb_miss)
> +               val |= P(TLB, MISS) | P(TLB, L2);
> +       else
> +               val |= P(TLB, HIT) | P(TLB,L1) | P(TLB, L2);
> +
> +       /*
> +        * bit 5: locked prefix
> +        */
> +       if (dse.ld_locked)
> +               val |= P(LOCK, LOCKED);
> +
> +       return val;
> +} 
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