Re: [PATCH v4 0/6] Add metrics for neoverse-n2

[Ian Rogers]

On Fri, Dec 23, 2022 at 4:39 AM Jing Zhang <renyu.zj@xxxxxxxxxxxxxxxxx> wrote:
>
> Changes since v3:
> - Add ipc_rate metric;
> - Drop the PublicDescription;
> - Describe PEutilization metrics in more detail;
> - Link: https://lore.kernel.org/all/1669310088-13482-1-git-send-email-renyu.zj@xxxxxxxxxxxxxxxxx/
>
> Changes since v2:
> - Correct the furmula of Branch metrics;
> - Add more PE utilization metrics;
> - Add more TLB metrics;
> - Add “ScaleUnit” for some metrics;
> - Add a newline at the end of the file;
> - Link: https://lore.kernel.org/all/1668411720-3581-1-git-send-email-renyu.zj@xxxxxxxxxxxxxxxxx/
>
> Changes since v1:
> - Corrected formula for topdown L1 due to wrong counts for stall_slot and
>   stall_slot_frontend;
> - Link: https://lore.kernel.org/all/1667214694-89839-1-git-send-email-renyu.zj@xxxxxxxxxxxxxxxxx/
>
>
> This series add six metricgroups for neoverse-n2, among which, the formula of
> topdown L1 is from ARM sbsa7.0 platform design document [0], D37-38.
>
> However, due to the wrong count of stall_slot and stall_slot_frontend on
> neoverse-n2, the real stall_slot and real stall_slot_frontend need to
> subtract cpu_cycles,  so correct the expression of topdown metrics.
> Reference from ARM neoverse-n2 errata notice [1], D117.
>
> 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. Reference from ARM PMU guide [2][3].
>
> [0] https://documentation-service.arm.com/static/60250c7395978b529036da86?token=
> [1] https://documentation-service.arm.com/static/636a66a64e6cf12278ad89cb?token=
> [2] https://documentation-service.arm.com/static/628f8fa3dfaf015c2b76eae8?token=
> [3] https://documentation-service.arm.com/static/62cfe21e31ea212bb6627393?token=
>
>
> $./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 -M TLB false_sharing 2
>
>  Performance counter stats for 'false_sharing 2':
>
>             31,561      L2D_TLB                          #     18.8 %  l2_tlb_miss_rate      (43.23%)
>              5,944      L2D_TLB_REFILL                                                       (43.23%)
>              2,248      L1I_TLB_REFILL                   #      0.1 %  l1i_tlb_miss_rate     (43.85%)
>          2,203,195      L1I_TLB                                                              (43.85%)
>        328,647,380      L1D_TLB                          #      0.0 %  l1d_tlb_miss_rate     (44.32%)
>             26,347      L1D_TLB_REFILL                                                       (44.32%)
>            747,319      L1I_TLB                          #      0.0 %  itlb_walk_rate        (43.74%)
>                310      ITLB_WALK                                                            (43.74%)
>        839,420,454      INST_RETIRED                     #     0.00 itlb_mpki                (42.77%)
>                212      ITLB_WALK                                                            (42.77%)
>                468      DTLB_WALK                        #      0.0 %  dtlb_walk_rate        (42.28%)
>        265,405,802      L1D_TLB                                                              (42.28%)
>        790,874,367      INST_RETIRED                     #     0.00 dtlb_mpki                (42.33%)
>                 23      DTLB_WALK                                                            (42.33%)
>
>        0.515904553 seconds time elapsed
>
>        1.410313000 seconds user
>        0.000000000 seconds sys
>
>
> $sudo ./perf stat -M TopDownL1 false_sharing 2
>
>  Performance counter stats for 'false_sharing 2':
>
>      4,310,905,590      cpu_cycles                       #      0.0 %  bad_speculation
>                                                   #      4.0 %  retiring              (66.87%)
>     25,009,763,735      stall_slot                                                           (66.87%)
>        855,659,327      op_spec                                                              (66.87%)
>        854,335,288      op_retired                                                           (66.87%)
>      4,330,308,058      cpu_cycles                       #     27.1 %  frontend_bound        (66.99%)
>     10,207,186,460      stall_slot_frontend                                                  (66.99%)
>      4,316,583,673      cpu_cycles                       #     69.4 %  backend_bound         (66.65%)
>     14,979,136,808      stall_slot_backend                                                   (66.65%)
>
>        0.572056818 seconds time elapsed
>
>        1.572143000 seconds user
>        0.004010000 seconds sys
>
>
> 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

Series:
Acked-by: Ian Rogers <irogers@xxxxxxxxxx>

The only observation I had is that the "per kilo instruction" in the
names (ie ending pki) could be moved into the ScaleUnit. Which may
make the names and the output a little cleaner.

Thanks!
Ian

>  .../arch/arm64/arm/neoverse-n2/metrics.json        | 277 +++++++++++++++++++++
>  1 file changed, 277 insertions(+)
>  create mode 100644 tools/perf/pmu-events/arch/arm64/arm/neoverse-n2/metrics.json
>
> --
> 1.8.3.1
>