Re: [PATCH v4 07/22] perf jevents: Add br metric group for branch statistics on Intel

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

On 2024-09-26 1:50 p.m., Ian Rogers wrote:
> The br metric group for branches itself comprises metric groups for
> total, taken, conditional, fused and far metric groups using json
> events. Conditional taken and not taken metrics are specific to
> Icelake and later generations, so the presence of the event is used to
> determine whether the metric should exist.
> > Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/pmu-events/intel_metrics.py | 138 +++++++++++++++++++++++++
>  1 file changed, 138 insertions(+)
> 
> diff --git a/tools/perf/pmu-events/intel_metrics.py b/tools/perf/pmu-events/intel_metrics.py
> index 58e243695f0a..09f7b7159e7c 100755
> --- a/tools/perf/pmu-events/intel_metrics.py
> +++ b/tools/perf/pmu-events/intel_metrics.py
> @@ -123,6 +123,143 @@ def Tsx() -> Optional[MetricGroup]:
>    ], description="Breakdown of transactional memory statistics")
>  
>  
> +def IntelBr():
> +  ins = Event("instructions")
> +
> +  def Total() -> MetricGroup:
> +    br_all = Event ("BR_INST_RETIRED.ALL_BRANCHES", "BR_INST_RETIRED.ANY")
> +    br_m_all = Event("BR_MISP_RETIRED.ALL_BRANCHES",
> +                     "BR_INST_RETIRED.MISPRED",
> +                     "BR_MISP_EXEC.ANY")
> +    br_clr = None
> +    try:
> +      br_clr = Event("BACLEARS.ANY", "BACLEARS.ALL")
> +    except:
> +      pass

There is no guarantee to the event name. It could be changed later.
The renaming already occurred several times, even for architectural events.

I think we should test all events' presence, not just a few of them.

There could be some effort in the future to sync with the event list for
each new generation and check if there is a renaming.

Thanks,
Kan
> +
> +    br_r = d_ratio(br_all, interval_sec)
> +    ins_r = d_ratio(ins, br_all)
> +    misp_r = d_ratio(br_m_all, br_all)
> +    clr_r = d_ratio(br_clr, interval_sec) if br_clr else None
> +
> +    return MetricGroup("br_total", [
> +        Metric("br_total_retired",
> +               "The number of branch instructions retired per second.", br_r,
> +               "insn/s"),
> +        Metric(
> +            "br_total_mispred",
> +            "The number of branch instructions retired, of any type, that were "
> +            "not correctly predicted as a percentage of all branch instrucions.",
> +            misp_r, "100%"),
> +        Metric("br_total_insn_between_branches",
> +               "The number of instructions divided by the number of branches.",
> +               ins_r, "insn"),
> +        Metric("br_total_insn_fe_resteers",
> +               "The number of resync branches per second.", clr_r, "req/s"
> +               ) if clr_r else None
> +    ])
> +
> +  def Taken() -> MetricGroup:
> +    br_all = Event("BR_INST_RETIRED.ALL_BRANCHES", "BR_INST_RETIRED.ANY")
> +    br_m_tk = None
> +    try:
> +      br_m_tk = Event("BR_MISP_RETIRED.NEAR_TAKEN",
> +                      "BR_MISP_RETIRED.TAKEN_JCC",
> +                      "BR_INST_RETIRED.MISPRED_TAKEN")
> +    except:
> +      pass
> +    br_r = d_ratio(br_all, interval_sec)
> +    ins_r = d_ratio(ins, br_all)
> +    misp_r = d_ratio(br_m_tk, br_all) if br_m_tk else None
> +    return MetricGroup("br_taken", [
> +        Metric("br_taken_retired",
> +               "The number of taken branches that were retired per second.",
> +               br_r, "insn/s"),
> +        Metric(
> +            "br_taken_mispred",
> +            "The number of retired taken branch instructions that were "
> +            "mispredicted as a percentage of all taken branches.", misp_r,
> +            "100%") if misp_r else None,
> +        Metric(
> +            "br_taken_insn_between_branches",
> +            "The number of instructions divided by the number of taken branches.",
> +            ins_r, "insn"),
> +    ])
> +
> +  def Conditional() -> Optional[MetricGroup]:
> +    try:
> +      br_cond = Event("BR_INST_RETIRED.COND",
> +                      "BR_INST_RETIRED.CONDITIONAL",
> +                      "BR_INST_RETIRED.TAKEN_JCC")
> +      br_m_cond = Event("BR_MISP_RETIRED.COND",
> +                        "BR_MISP_RETIRED.CONDITIONAL",
> +                        "BR_MISP_RETIRED.TAKEN_JCC")
> +    except:
> +      return None
> +
> +    br_cond_nt = None
> +    br_m_cond_nt = None
> +    try:
> +      br_cond_nt = Event("BR_INST_RETIRED.COND_NTAKEN")
> +      br_m_cond_nt = Event("BR_MISP_RETIRED.COND_NTAKEN")
> +    except:
> +      pass
> +    br_r = d_ratio(br_cond, interval_sec)
> +    ins_r = d_ratio(ins, br_cond)
> +    misp_r = d_ratio(br_m_cond, br_cond)
> +    taken_metrics = [
> +        Metric("br_cond_retired", "Retired conditional branch instructions.",
> +               br_r, "insn/s"),
> +        Metric("br_cond_insn_between_branches",
> +               "The number of instructions divided by the number of conditional "
> +               "branches.", ins_r, "insn"),
> +        Metric("br_cond_mispred",
> +               "Retired conditional branch instructions mispredicted as a "
> +               "percentage of all conditional branches.", misp_r, "100%"),
> +    ]
> +    if not br_m_cond_nt:
> +      return MetricGroup("br_cond", taken_metrics)
> +
> +    br_r = d_ratio(br_cond_nt, interval_sec)
> +    ins_r = d_ratio(ins, br_cond_nt)
> +    misp_r = d_ratio(br_m_cond_nt, br_cond_nt)
> +
> +    not_taken_metrics = [
> +        Metric("br_cond_retired", "Retired conditional not taken branch instructions.",
> +               br_r, "insn/s"),
> +        Metric("br_cond_insn_between_branches",
> +               "The number of instructions divided by the number of not taken conditional "
> +               "branches.", ins_r, "insn"),
> +        Metric("br_cond_mispred",
> +               "Retired not taken conditional branch instructions mispredicted as a "
> +               "percentage of all not taken conditional branches.", misp_r, "100%"),
> +    ]
> +    return MetricGroup("br_cond", [
> +        MetricGroup("br_cond_nt", not_taken_metrics),
> +        MetricGroup("br_cond_tkn", taken_metrics),
> +    ])
> +
> +  def Far() -> Optional[MetricGroup]:
> +    try:
> +      br_far = Event("BR_INST_RETIRED.FAR_BRANCH")
> +    except:
> +      return None
> +
> +    br_r = d_ratio(br_far, interval_sec)
> +    ins_r = d_ratio(ins, br_far)
> +    return MetricGroup("br_far", [
> +        Metric("br_far_retired", "Retired far control transfers per second.",
> +               br_r, "insn/s"),
> +        Metric(
> +            "br_far_insn_between_branches",
> +            "The number of instructions divided by the number of far branches.",
> +            ins_r, "insn"),
> +    ])
> +
> +  return MetricGroup("br", [Total(), Taken(), Conditional(), Far()],
> +                     description="breakdown of retired branch instructions")
> +
> +
>  def main() -> None:
>    global _args
>  
> @@ -150,6 +287,7 @@ def main() -> None:
>        Rapl(),
>        Smi(),
>        Tsx(),
> +      IntelBr(),
>    ])
>  
>