Re: [PATCH] perf/x86/intel: Extend the ref-cycles event to GP counters

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-09-27 12:47 a.m., Stephane Eranian wrote:
> On Mon, Sep 11, 2023 at 7:41 AM <kan.liang@linux.intel.com> wrote:
>>
>> From: Kan Liang <kan.liang@linux.intel.com>
>>
>> The current ref-cycles event is only available on the fixed counter 2.
>> Starting from the GLC and GRT core, the architectural UnHalted Reference
>> Cycles event (0x013c) which is available on general-purpose counters
>> can collect the exact same events as the fixed counter 2.
>>
>> Update the mapping of ref-cycles to 0x013c. So the ref-cycles can be
>> available on both fixed counter 2 and general-purpose counters.
>>
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>>  arch/x86/events/intel/core.c | 21 ++++++++++++++++++++-
>>  1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
>> index e1543d6dc48a..a08f794a0e79 100644
>> --- a/arch/x86/events/intel/core.c
>> +++ b/arch/x86/events/intel/core.c
>> @@ -211,6 +211,14 @@ static struct event_constraint intel_slm_event_constraints[] __read_mostly =
>>         EVENT_CONSTRAINT_END
>>  };
>>
>> +static struct event_constraint intel_grt_event_constraints[] __read_mostly = {
>> +       FIXED_EVENT_CONSTRAINT(0x00c0, 0), /* INST_RETIRED.ANY */
>> +       FIXED_EVENT_CONSTRAINT(0x003c, 1), /* CPU_CLK_UNHALTED.CORE */
>> +       FIXED_EVENT_CONSTRAINT(0x0300, 2), /* pseudo CPU_CLK_UNHALTED.REF */
>> +       FIXED_EVENT_CONSTRAINT(0x013c, 2), /* CPU_CLK_UNHALTED.REF_TSC_P */
>> +       EVENT_CONSTRAINT_END
>> +};
>> +
>>  static struct event_constraint intel_skl_event_constraints[] = {
>>         FIXED_EVENT_CONSTRAINT(0x00c0, 0),      /* INST_RETIRED.ANY */
>>         FIXED_EVENT_CONSTRAINT(0x003c, 1),      /* CPU_CLK_UNHALTED.CORE */
>> @@ -314,6 +322,7 @@ static struct event_constraint intel_glc_event_constraints[] = {
>>         FIXED_EVENT_CONSTRAINT(0x0100, 0),      /* INST_RETIRED.PREC_DIST */
>>         FIXED_EVENT_CONSTRAINT(0x003c, 1),      /* CPU_CLK_UNHALTED.CORE */
>>         FIXED_EVENT_CONSTRAINT(0x0300, 2),      /* CPU_CLK_UNHALTED.REF */
>> +       FIXED_EVENT_CONSTRAINT(0x013c, 2),      /* CPU_CLK_UNHALTED.REF_TSC_P */
> 
> I don't think that on SKL there is a REF_TSC_P. It only appears on
> SPR. The encoding exists on SKL
> but it counts REF_XCLK which I think counts something different. Please check.

Right, the patch is to update the event constraint to GLC
(intel_glc_event_constraints) for SPR, not SKL.

Thanks,
Kan

>>         FIXED_EVENT_CONSTRAINT(0x0400, 3),      /* SLOTS */
>>         METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_RETIRING, 0),
>>         METRIC_EVENT_CONSTRAINT(INTEL_TD_METRIC_BAD_SPEC, 1),
>> @@ -5983,6 +5992,12 @@ static __always_inline int intel_pmu_init_hybrid(enum hybrid_pmu_type pmus)
>>         return 0;
>>  }
>>
>> +static __always_inline void intel_pmu_ref_cycles_ext(void)
>> +{
>> +       if (!(x86_pmu.events_maskl & (INTEL_PMC_MSK_FIXED_REF_CYCLES >> INTEL_PMC_IDX_FIXED)))
>> +               intel_perfmon_event_map[PERF_COUNT_HW_REF_CPU_CYCLES] = 0x013c;
>> +}
>> +
>>  static __always_inline void intel_pmu_init_glc(struct pmu *pmu)
>>  {
>>         x86_pmu.late_ack = true;
>> @@ -6005,6 +6020,8 @@ static __always_inline void intel_pmu_init_glc(struct pmu *pmu)
>>         memcpy(hybrid_var(pmu, hw_cache_extra_regs), glc_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
>>         hybrid(pmu, event_constraints) = intel_glc_event_constraints;
>>         hybrid(pmu, pebs_constraints) = intel_glc_pebs_event_constraints;
>> +
>> +       intel_pmu_ref_cycles_ext();
>>  }
>>
>>  static __always_inline void intel_pmu_init_grt(struct pmu *pmu)
>> @@ -6021,9 +6038,11 @@ static __always_inline void intel_pmu_init_grt(struct pmu *pmu)
>>         memcpy(hybrid_var(pmu, hw_cache_event_ids), glp_hw_cache_event_ids, sizeof(hw_cache_event_ids));
>>         memcpy(hybrid_var(pmu, hw_cache_extra_regs), tnt_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
>>         hybrid_var(pmu, hw_cache_event_ids)[C(ITLB)][C(OP_READ)][C(RESULT_ACCESS)] = -1;
>> -       hybrid(pmu, event_constraints) = intel_slm_event_constraints;
>> +       hybrid(pmu, event_constraints) = intel_grt_event_constraints;
>>         hybrid(pmu, pebs_constraints) = intel_grt_pebs_event_constraints;
>>         hybrid(pmu, extra_regs) = intel_grt_extra_regs;
>> +
>> +       intel_pmu_ref_cycles_ext();
>>  }
>>
>>  __init int intel_pmu_init(void)
>> --
>> 2.35.1
>>