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

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Date:   Tue, 26 Sep 2023 21:47:57 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, ak@...ux.intel.com
Subject: Re: [PATCH] perf/x86/intel: Extend the ref-cycles event to GP counters

On Mon, Sep 11, 2023 at 7:41 AM <kan.liang@...ux.intel.com> wrote:
>
> From: Kan Liang <kan.liang@...ux.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@...ux.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.

>         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
>