Re: [PATCH 0/2] perf jevents: Add NVIDIA Tegra410 uncore DDR and PCIe metrics

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Sep 28, 2026 at 10:51:25AM -0700, Chun-Tse Shao wrote:
> Add DDR bandwidth/latency and PCIe bandwidth metrics for the NVIDIA
> Tegra410 SoC to arm64_metrics.py. The metrics use the sysfs events of
> the Tegra410 UCF, CMEM latency and PCIE PMUs, and follow the formulas in
> Documentation/admin-guide/perf/nvidia-tegra410-pmu.rst.

Ian,

	Can you take a look and please provide your Reviewed-by?

Thanks,

- Arnaldo
 
> Patch 1 adds the DDR metrics and makes pmu-events/Build also run
> arm64_metrics.py for the nvidia vendor models. Patch 2 adds the PCIe
> metrics, in total and per PCIe Root Complex (RC).
> 
> Tested on a 2-socket Tegra410 system:
> 
>  - memcpy with multiload (from multichase) on socket 0 CPUs and memory:
>    lpm_ddr_bw is 740-744 GB/s at steady state (perf stat -I 2000),
>    multiload reports 708063 MiB/s (742 GB/s).
>  - Read only (stream-sum) and write only (memset) loads on socket 1:
>    lpm_ddr_rd_bw is 608 GB/s with 2.4 GB/s of writes, lpm_ddr_wr_bw is
>    628 GB/s with 1.1 GB/s of reads.
>  - memcpy on socket 0 CPUs with memory on socket 1: socket 0's
>    lpm_ddr_rem_rd_bw and socket 1's lpm_ddr_rd_bw count nearly the same
>    bytes (258.03 vs 258.73 GB).
>  - lpm_ddr_lat idle is 150 ns in the default aggregation, and 132 ns and
>    194 ns for socket 0 and 1 with --per-socket. Under the memcpy load it
>    is 555 ns by default and 563 ns for socket 0 with --per-socket, and
>    stays at 551-558 ns per interval with -I 1000.
>  - 8 GiB O_DIRECT dd read from an NVMe drive behind RC 0 of socket 0:
>    lpm_pcie_wr_bw_0 counts the 8 GiB at 8.7 GB/s (dd: 8.7 GB/s). With
>    the buffer on node 0 it shows up in lpm_pcie_loc_wr_bw_0, with the
>    buffer on node 1 in lpm_pcie_rem_wr_bw_0. With --per-socket, socket 0
>    shows the same and no metric of either socket is nan.
>  - With the nvidia_t410 metrics forced on a machine without these PMUs
>    (PERF_CPUID=0x000000004e0f0100 on an x86 JEVENTS_ARCH=all build), the
>    PCIe metrics read 0 rather than failing to parse, also with
>    --per-socket.
>  - "perf test 10" (PMU JSON event tests) passes on the Tegra410 system
>    and with the x86 JEVENTS_ARCH=all build.
> 
> Chun-Tse Shao (2):
>   perf jevents: Add NVIDIA Tegra410 uncore DDR metrics
>   perf jevents: Add NVIDIA Tegra410 uncore PCIe metrics
> 
>  tools/perf/pmu-events/Build            |   2 +-
>  tools/perf/pmu-events/arm64_metrics.py | 126 ++++++++++++++++++++++++-
>  tools/perf/pmu-events/metric.py        |   2 +-
>  3 files changed, 126 insertions(+), 4 deletions(-)
> 
> 
> base-commit: 0ae6fc78c5ce0dfd18d8712a50f0fd4602eff103
> --
> 2.56.0.rc1.315.gc6ed9934b7-goog