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SubjectRe: [PATCH V6 07/14] perf/x86/intel: Generic support for hardware TopDown metrics
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On 7/20/2020 1:41 PM, Peter Zijlstra wrote:
> On Fri, Jul 17, 2020 at 07:05:47AM -0700, kan.liang@linux.intel.com wrote:
>
>> For the event mapping, a special 0x00 event code is used, which is
>> reserved for fake events. The metric events start from umask 0x10.
>
>> +#define INTEL_PMC_IDX_METRIC_BASE (INTEL_PMC_IDX_FIXED + 16)
>> +#define INTEL_PMC_IDX_TD_RETIRING (INTEL_PMC_IDX_METRIC_BASE + 0)
>> +#define INTEL_PMC_IDX_TD_BAD_SPEC (INTEL_PMC_IDX_METRIC_BASE + 1)
>> +#define INTEL_PMC_IDX_TD_FE_BOUND (INTEL_PMC_IDX_METRIC_BASE + 2)
>> +#define INTEL_PMC_IDX_TD_BE_BOUND (INTEL_PMC_IDX_METRIC_BASE + 3)
>
> So this is internal and we can change it around if/when needed, right?
>

Yes

>> +#define INTEL_PMC_IDX_METRIC_END INTEL_PMC_IDX_TD_BE_BOUND
>> +#define INTEL_PMC_MSK_TOPDOWN ((0xfull << INTEL_PMC_IDX_METRIC_BASE) | \
>> + INTEL_PMC_MSK_FIXED_SLOTS)
>> +
>> +/*
>> + * There is no event-code assigned to the TopDown events.
>> + *
>> + * For the slots event, use the pseudo code of the fixed counter 3.
>> + *
>> + * For the metric events, the pseudo event-code is 0x00.
>> + * The pseudo umask-code starts from 0x10.
>> + */
>> +#define INTEL_TD_SLOTS 0x0400 /* TOPDOWN.SLOTS */
>> +/* Level 1 metrics */
>> +#define INTEL_TD_METRIC_RETIRING 0x1000 /* Retiring metric */
>> +#define INTEL_TD_METRIC_BAD_SPEC 0x1100 /* Bad speculation metric */
>> +#define INTEL_TD_METRIC_FE_BOUND 0x1200 /* FE bound metric */
>> +#define INTEL_TD_METRIC_BE_BOUND 0x1300 /* BE bound metric */
>> +#define INTEL_TD_METRIC_MAX INTEL_TD_METRIC_BE_BOUND
>> +#define INTEL_TD_METRIC_NUM 4
>
> But this is ABI, once we merge this, it's stuck.
>
> Also, per how Fixed2 is 0x0300, should not Fixed16 (aka
> METRICS_RETIRING) be 0x1100 ?
>
> But aside of that, are we sure the hardware will never grow a Fixed16?
> Or do we want to be paranoid and move the metrics events up in the
> pseudo event space?
>

Right, we cannot guarantee that the number of fixed counters is always
less than 16.

I will move the metrics events to the middle of the pseudo event space.

+#define INTEL_TD_METRIC_RETIRING 0x8000 /* Retiring metric */
+#define INTEL_TD_METRIC_BAD_SPEC 0x8100 /* Bad speculation metric */
+#define INTEL_TD_METRIC_FE_BOUND 0x8200 /* FE bound metric */
+#define INTEL_TD_METRIC_BE_BOUND 0x8300 /* BE bound metric */

Thanks,
Kan

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