linux-kernel - Re: [PATCH RFC 0/6] Add metrics for neoverse-n2

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Date:   Sat, 19 Nov 2022 11:30:29 +0800
From:   Jing Zhang <renyu.zj@...ux.alibaba.com>
To:     James Clark <james.clark@....com>,
        nick Forrington <Nick.Forrington@....com>,
        Jumana MP <Jumana.MP@....com>,
        John Garry <john.garry@...wei.com>
Cc:     Will Deacon <will@...nel.org>, Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.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>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/6] Add metrics for neoverse-n2



在 2022/11/16 下午7:19, James Clark 写道:
> 
> 
> On 31/10/2022 11:11, Jing Zhang wrote:
>> This series add six metricgroups for neoverse-n2, among which, the
>> formula of topdown L1 is from the document:
>> https://documentation-service.arm.com/static/60250c7395978b529036da86?token=
>>
>> Since neoverse-n2 does not yet support topdown L2, metricgroups such
>> as Cache, TLB, Branch, InstructionsMix, and PEutilization are added to
>> help further analysis of performance bottlenecks.
>>
> 
> Hi Jing,
> 
> Thanks for working on this, these metrics look ok to me in general,
> although we're currently working on publishing standardised metrics
> across all new cores as part of a new project in Arm. This will include
> N2, and our ones are very similar (or almost identical) to yours,
> barring slightly different group names, metric names, and differences in
> things like outputting topdown metrics as percentages.
> 
> We plan to publish our standard metrics some time in the next 2 months.
> Would you consider holding off on merging this change so that we have
> consistant group names and units going forward? Otherwise N2 would be
> the odd one out. I will send you the metrics when they are ready, and we
> will have a script to generate perf jsons from them, so you can review.
> 
> We also have a slightly different forumula for one of the top down
> metrics which I think would be slightly more accurate. We don't have
> anything for your "PE utilization" metrics, which I can raise
> internally. It could always be added to perf on top of the standardised
> ones if we don't add it to our standard ones.
> 
> Thanks
> James
> 

Hi James,

Regarding the arm n2 standard metrics last time, is my understanding correct,
and does it meet your meaning? If so, may I ask when you will send me the
standards you formulate so that I can align with you in time over my patchset.
Please communicate this matter so that we can understand each other's schedule.

Thanks,
Jing


>> with this series on neoverse-n2:
>>
>> $./perf list metricgroup
>>
>> List of pre-defined events (to be used in -e):
>>
>>
>> Metric Groups:
>>
>> Branch
>> Cache
>> InstructionMix
>> PEutilization
>> TLB
>> TopDownL1
>>
>>
>> $./perf list
>>
>> ...
>> Metric Groups:
>>
>> Branch:
>>   branch_miss_pred_rate
>>        [The rate of branches mis-predited to the overall branches]
>>   branch_mpki
>>        [The rate of branches mis-predicted per kilo instructions]
>>   branch_pki
>>        [The rate of branches retired per kilo instructions]
>> Cache:
>>   l1d_cache_miss_rate
>>        [The rate of L1 D-Cache misses to the overall L1 D-Cache]
>>   l1d_cache_mpki
>>        [The rate of L1 D-Cache misses per kilo instructions]
>> ...
>>
>>
>> $sudo ./perf stat -a -M TLB sleep 1
>>
>>  Performance counter stats for 'system wide':
>>
>>         35,861,936      L1I_TLB                          #     0.00 itlb_walk_rate           (74.91%)
>>              5,661      ITLB_WALK                                                            (74.91%)
>>         97,279,240      INST_RETIRED                     #     0.07 itlb_mpki                (74.91%)
>>              6,851      ITLB_WALK                                                            (74.91%)
>>             26,391      DTLB_WALK                        #     0.00 dtlb_walk_rate           (75.07%)
>>         35,585,545      L1D_TLB                                                              (75.07%)
>>         85,923,244      INST_RETIRED                     #     0.35 dtlb_mpki                (75.11%)
>>             29,992      DTLB_WALK                                                            (75.11%)
>>
>>        1.003450755 seconds time elapsed
>>        
>>
>> Jing Zhang (6):
>>   perf vendor events arm64: Add topdown L1 metrics for neoverse-n2
>>   perf vendor events arm64: Add TLB metrics for neoverse-n2
>>   perf vendor events arm64: Add cache metrics for neoverse-n2
>>   perf vendor events arm64: Add branch metrics for neoverse-n2
>>   perf vendor events arm64: Add PE utilization metrics for neoverse-n2
>>   perf vendor events arm64: Add instruction mix metrics for neoverse-n2
>>
>>  .../arch/arm64/arm/neoverse-n2/metrics.json        | 247 +++++++++++++++++++++
>>  1 file changed, 247 insertions(+)
>>  create mode 100644 tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json
>>