Messages in this thread | | | Date | Thu, 1 Dec 2022 19:08:33 +0800 | Subject | Re: [PATCH v3 5/6] perf vendor events arm64: Add PE utilization metrics for neoverse-n2 | From | Jing Zhang <> |
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在 2022/12/1 上午2:58, Ian Rogers 写道: > On Thu, Nov 24, 2022 at 9:15 AM Jing Zhang <renyu.zj@linux.alibaba.com> wrote: >> >> Add PE utilization related metrics. >> >> Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com> >> --- >> .../arch/arm64/arm/neoverse-n2/metrics.json | 45 ++++++++++++++++++++++ >> 1 file changed, 45 insertions(+) >> >> diff --git a/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json b/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json >> index 23c7d62..7b54819 100644 >> --- a/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json >> +++ b/tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json >> @@ -189,5 +189,50 @@ >> "MetricGroup": "Branch", >> "MetricName": "branch_miss_pred_rate", >> "ScaleUnit": "100%" >> + }, >> + { >> + "MetricExpr": "instructions / CPU_CYCLES", >> + "PublicDescription": "The average number of instructions executed for each cycle.", >> + "BriefDescription": "Instructions per cycle", >> + "MetricGroup": "PEutilization", >> + "MetricName": "ipc" >> + }, > > A related useful metric is percentage of peak, so if the peak IPC is 8 > (usually a constant related to the number of functional units) then > you can just compute the ratio of IPC with this. >
Glad to discuss these with you. The peak ipc value of neoverse-n2 is 5. Maybe I should add an ipc_rate metric?
>> + { >> + "MetricExpr": "INST_RETIRED / CPU_CYCLES", >> + "PublicDescription": "Architecturally executed Instructions Per Cycle (IPC)", >> + "BriefDescription": "Architecturally executed Instructions Per Cycle (IPC)", > > > The duplicated descriptions are unnecessary. Drop the public one for > consistency with what we do for Intel: > https://github.com/intel/perfmon/blob/main/scripts/create_perf_json.py#L299 >
Sounds good, will do.
>> + "MetricGroup": "PEutilization", >> + "MetricName": "retired_ipc" >> + }, >> + { >> + "MetricExpr": "INST_SPEC / CPU_CYCLES", >> + "PublicDescription": "Speculatively executed Instructions Per Cycle (IPC)", >> + "BriefDescription": "Speculatively executed Instructions Per Cycle (IPC)", >> + "MetricGroup": "PEutilization", >> + "MetricName": "spec_ipc" >> + }, >> + { >> + "MetricExpr": "OP_RETIRED / OP_SPEC", >> + "PublicDescription": "Fraction of operations retired", >> + "BriefDescription": "Fraction of operations retired", > > Would instructions be clearer than operations here? >
operation and instruction are different. OP_RETIRED counts any operation (not instruction) that has been architecturally executed, For example, speculatively executed operations that have been abandoned for a branch mispredict will not be counted. So I think operation might be more accurate.
>> + "MetricGroup": "PEutilization", >> + "MetricName": "retired_rate", >> + "ScaleUnit": "100%" >> + }, >> + { >> + "MetricExpr": "1 - OP_RETIRED / OP_SPEC", > > Should OP_RETIRED be greater than OP_SPEC? In which case won't this > metric be negative? >
OP_RETIRED will not be greater than OP_SPEC. OP_SPEC counts any operation that has been speculatively executed. OP_SPEC is a superset of the OP_RETIRED event. There is a description about OP_SPEC and OP_RETIRED in this neoverse-n2 document. Link: https://documentation-service.arm.com/static/62cfe21e31ea212bb6627393?token=
>> + "PublicDescription": "Fraction of operations wasted", >> + "BriefDescription": "Fraction of operations wasted", >> + "MetricGroup": "PEutilization", >> + "MetricName": "wasted_rate", >> + "ScaleUnit": "100%" >> + }, >> + { >> + "MetricExpr": "OP_RETIRED / OP_SPEC * (1 - (STALL_SLOT - CPU_CYCLES) / (CPU_CYCLES * 5))", >> + "PublicDescription": "Utilization of CPU", >> + "BriefDescription": "Utilization of CPU", > > Some more detail in the description would be useful. >
Ok, I'll describe it in more detail. CPU_utilization reflects the truly effective ratio of operation executed by the CPU, which means that misprediction and stall are not included. Note that stall_slot minus cpu_cycles is a correction to the stall_slot error count.
>> + "MetricGroup": "PEutilization", >> + "MetricName": "cpu_utilization", >> + "ScaleUnit": "100%" >> } >> ] >> -- >> 1.8.3.1 >>
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