[PATCH] powerpc/perf: Add json metric events to present CPI stall cycles in powerpc

[Ian Rogers]

On Wed, Feb 15, 2023 at 10:12 PM Athira Rajeev
<atrajeev at linux.vnet.ibm.com> wrote:
>
> Power10 Performance Monitoring Unit (PMU) provides events
> to understand stall cycles of different pipeline stages.
> These events along with completed instructions provides
> useful metrics for application tuning.
>
> Patch implements the json changes to collect counter statistics
> to present the high level CPI stall breakdown metrics. New metric
> group is named as "CPI_STALL_RATIO" and this new metric group
> presents these stall metrics:
> - DISPATCHED_CPI ( Dispatch stall cycles per insn )
> - ISSUE_STALL_CPI ( Issue stall cycles per insn )
> - EXECUTION_STALL_CPI ( Execution stall cycles per insn )
> - COMPLETION_STALL_CPI ( Completition stall cycles per insn )
>
> To avoid multipling of events, PM_RUN_INST_CMPL event has been
> modified to use PMC5(performance monitoring counter5) instead
> of PMC4. This change is needed, since completion stall event
> is using PMC4.
>
> Usage example:
>
>  ./perf stat --metric-no-group -M CPI_STALL_RATIO <workload>
>
>  Performance counter stats for 'workload':
>
>     63,056,817,982      PM_CMPL_STALL                    #     0.28 COMPLETION_STALL_CPI
>  1,743,988,038,896      PM_ISSUE_STALL                   #     7.73 ISSUE_STALL_CPI
>    225,597,495,030      PM_RUN_INST_CMPL                 #     6.18 DISPATCHED_CPI
>                                                   #    37.48 EXECUTION_STALL_CPI
>  1,393,916,546,654      PM_DISP_STALL_CYC
>  8,455,376,836,463      PM_EXEC_STALL
>
> "--metric-no-group" is used for forcing PM_RUN_INST_CMPL to be scheduled
> in all group for more accuracy.
>
> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>

Acked-by: Ian Rogers <irogers at google.com>

Thanks,
Ian

> ---
>  tools/perf/pmu-events/arch/powerpc/power10/metrics.json | 8 ++++----
>  tools/perf/pmu-events/arch/powerpc/power10/others.json  | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/pmu-events/arch/powerpc/power10/metrics.json b/tools/perf/pmu-events/arch/powerpc/power10/metrics.json
> index b57526fa44f2..6f53583a0c62 100644
> --- a/tools/perf/pmu-events/arch/powerpc/power10/metrics.json
> +++ b/tools/perf/pmu-events/arch/powerpc/power10/metrics.json
> @@ -15,7 +15,7 @@
>      {
>          "BriefDescription": "Average cycles per completed instruction when dispatch was stalled for any reason",
>          "MetricExpr": "PM_DISP_STALL_CYC / PM_RUN_INST_CMPL",
> -        "MetricGroup": "CPI",
> +        "MetricGroup": "CPI;CPI_STALL_RATIO",
>          "MetricName": "DISPATCHED_CPI"
>      },
>      {
> @@ -147,13 +147,13 @@
>      {
>          "BriefDescription": "Average cycles per completed instruction when the NTC instruction has been dispatched but not issued for any reason",
>          "MetricExpr": "PM_ISSUE_STALL / PM_RUN_INST_CMPL",
> -        "MetricGroup": "CPI",
> +        "MetricGroup": "CPI;CPI_STALL_RATIO",
>          "MetricName": "ISSUE_STALL_CPI"
>      },
>      {
>          "BriefDescription": "Average cycles per completed instruction when the NTC instruction is waiting to be finished in one of the execution units",
>          "MetricExpr": "PM_EXEC_STALL / PM_RUN_INST_CMPL",
> -        "MetricGroup": "CPI",
> +        "MetricGroup": "CPI;CPI_STALL_RATIO",
>          "MetricName": "EXECUTION_STALL_CPI"
>      },
>      {
> @@ -309,7 +309,7 @@
>      {
>          "BriefDescription": "Average cycles per completed instruction when the NTC instruction cannot complete because the thread was blocked",
>          "MetricExpr": "PM_CMPL_STALL / PM_RUN_INST_CMPL",
> -        "MetricGroup": "CPI",
> +        "MetricGroup": "CPI;CPI_STALL_RATIO",
>          "MetricName": "COMPLETION_STALL_CPI"
>      },
>      {
> diff --git a/tools/perf/pmu-events/arch/powerpc/power10/others.json b/tools/perf/pmu-events/arch/powerpc/power10/others.json
> index 7d0de1a2860b..a771e4b6bec5 100644
> --- a/tools/perf/pmu-events/arch/powerpc/power10/others.json
> +++ b/tools/perf/pmu-events/arch/powerpc/power10/others.json
> @@ -265,7 +265,7 @@
>      "BriefDescription": "Load Missed L1, counted at finish time."
>    },
>    {
> -    "EventCode": "0x400FA",
> +    "EventCode": "0x500FA",
>      "EventName": "PM_RUN_INST_CMPL",
>      "BriefDescription": "Completed PowerPC instructions gated by the run latch."
>    }
> --
> 2.31.1
>