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

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Message-ID: <CABPqkBTTUJZQJ3_Tte92DKopxZGYJVsaw2tdSea9ZcmpZbx=hA@mail.gmail.com>
Date:	Mon, 29 Oct 2012 16:39:42 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [Patch v1 04/10] perf/x86: add memory profiling via PEBS Load Latency

On Mon, Oct 29, 2012 at 4:35 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 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?
>
Let's add something in x86_pmu. We could, for instance, generalize
x86_pmu.er_flags into x86_pmu.flags. Instead of adding yet another
flag field.

> 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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