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Date: Thu, 1 Dec 2022 19:08:33 +0800 From: Jing Zhang <renyu.zj@...ux.alibaba.com> To: Ian Rogers <irogers@...gle.com> Cc: John Garry <john.g.garry@...cle.com>, Xing Zhengjun <zhengjun.xing@...ux.intel.com>, Will Deacon <will@...nel.org>, James Clark <james.clark@....com>, Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...aro.org>, linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Andrew Kilroy <andrew.kilroy@....com>, Shuai Xue <xueshuai@...ux.alibaba.com>, Zhuo Song <zhuo.song@...ux.alibaba.com> Subject: Re: [PATCH v3 5/6] perf vendor events arm64: Add PE utilization metrics for neoverse-n2 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@...ux.alibaba.com> wrote: >> >> Add PE utilization related metrics. >> >> Signed-off-by: Jing Zhang <renyu.zj@...ux.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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