[PATCH v2 0/9] perf: Add NVIDIA Tegra410 uncore PMU events and metrics
Ian Rogers
irogers at google.com
Fri Oct 30 21:17:56 PDT 2026
On Fri, Oct 30, 2026 at 3:19 PM Besar Wicaksono <bwicaksono at nvidia.com> wrote:
>
> > -----Original Message-----
> > From: Ian Rogers <irogers at google.com>
> > Sent: Friday, October 30, 2026 6:07 PM
> > To: Besar Wicaksono <bwicaksono at nvidia.com>
> > Cc: acme at kernel.org; namhyung at kernel.org; ctshao at google.com; linux-
> > tegra at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-perf-
> > users at vger.kernel.org; linux-kernel at vger.kernel.org; Vikram Sethi
> > <vsethi at nvidia.com>; Rich Wiley <rwiley at nvidia.com>; Sean Kelley
> > <skelley at nvidia.com>; Matt Ochs <mochs at nvidia.com>; Raj Joshi
> > <rajjoshi at nvidia.com>; Thierry Reding <treding at nvidia.com>; Jon Hunter
> > <jonathanh at nvidia.com>; john.garry at linux.dev; will at kernel.org;
> > james.clark at linaro.org; mike.leach at arm.com; leo.yan at linux.dev;
> > mark.rutland at arm.com; alexander.shishkin at linux.intel.com;
> > jolsa at kernel.org; adrian.hunter at intel.com
> > Subject: Re: [PATCH v2 0/9] perf: Add NVIDIA Tegra410 uncore PMU events
> > and metrics
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Fri, Oct 30, 2026 at 10:49 AM Besar Wicaksono
> > <bwicaksono at nvidia.com> wrote:
> > >
> > > Add event aliases and derived metrics for the NVIDIA Tegra410 uncore
> > > PMUs, and fix perf's aggregation of PMU instances that are numbered in
> > > more than one parts in their name.
> > >
> > > The series covers the UCF, PCIe, PCIe target, CPU memory latency, and
> > > chip-to-chip interconnect PMUs. It provides symbolic names for the raw
> > > event encodings and metrics for bandwidth, frequency, and average read
> > > latency.
> > >
> > > The PCIe and PCIe target PMUs are named
> > nvidia_pcie_pmu_<socket>_rc_<rc>
> > > and nvidia_pcie_tgt_pmu_<socket>_rc_<rc>. Their json Unit uses the
> > > existing comma-separated form ("nvidia_pcie_pmu_,rc_"), but perf only
> > > merged instances that differ in the trailing number, so these events and
> > > metrics gave one result per socket and were reported incorrectly (e.g.
> > > with --metric-only), as discussed in v1. Patches 6-9 fix this:
> > >
> > > - Patch 6 adds a check of the cpumasks of all merged PMU instances to the
> > > zero-count skip in perf stat, so a socket that counts nothing shows 0
> > > instead of having its row hidden.
> > > - Patch 7 merges PMU instances that match the same comma-separated
> > json
> > > Unit. This also applies to the HiSilicon hisi_sccl PMUs, which use the
> > > same json form; not tested on HiSilicon hardware.
> > > - Patch 8 labels a merged uncore counter after all of its PMUs, e.g.
> > > nvidia_pcie_pmu_*_rc_*/cycles/ or nvidia_ucf_pmu/cycles/, instead of
> > > after the first instance, such as nvidia_pcie_pmu_0_rc_0/cycles/.
> > > Output with --no-aggr is unchanged.
> > > - Patch 9 describes these PMU names in the ABI document.
> > >
> > > Changes in v2:
> > > - Move the uncore JSON out of the sys directory and remove the
> > > "Compat" fields. Thanks to Ian Rogers for the feedback.
> > > - Drop "perf jevents: Process model files before sys subdirectories",
> > > which this series no longer needs.
> > > - Add UCF SLC and memory bandwidth metrics from all sources to local
> > > CMEM (read, write and read+write) and from local sources to local
> > > CMEM and to remote memory, PCIe bandwidth metrics to local
> > > destinations, and read+write bandwidth metrics for UCF SLC, UCF
> > > memory and PCIe. Thanks to Chun-Tse Shao for the suggestion.
> > > - Add patches 6-9 to fix the PCIe instance aggregation. Thanks to Ian
> > > Rogers and Chun-Tse Shao for the pointers.
> > >
> > > v1: https://lore.kernel.org/all/20261019164241.403644-1-
> > bwicaksono at nvidia.com/
> >
> > Why don't we look to fix code in drivers/perf? This series introduces
> > PMU instances, overloads the meaning of aliases, and a bunch of other
> > silly complexity due to poor reviews and maintenance of drivers/perf -
> > specifically by not pointing out the ABI issues. Isn't this a
> > straightforward, whoops we did a bad suffix and here's the patch to
> > rename our PMU in the driver? Throwing more complexity at the problem
> > doesn't feel like the right fix.
>
> Hi Ian,
>
> My apologies for the names not following perf's PMU naming convention.
> I will be more careful about this in future.
>
> These names (nvidia_pcie_pmu_<socket>_rc_<root complex> and
> nvidia_pcie_tgt_pmu_<socket>_rc_<root complex>) have been upstream
> since v7.1, and several customers already rely on them. Renaming them in
> the driver would break their use case.
It only breaks their use case if they name the PMU with an event. You
have multiple naming conventions for the PMU and only those involving
multiple sockets have a broken suffix.
> Given that, what would you suggest as the next step? Would handling these
> names in perf, as in patch 7 and 8, be reasonable, or do you have another
> approach in mind?
So we don't need a new abstraction, I've been reducing aggregation
abstractions in the perf tool. As I pointed to previously, the suffix
is computed with pmu_name_len_no_suffix:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmus.c?h=perf-tools-next#n66
So you can do something like (untested):
```
size_t pmu_name_len_no_suffix(const char *str)
{
if (strstarts(str, "nvidia_") && strstr(str, "_rc_")) {
// nvidia PMU with a non-ABI suffix of nvidia_..._[0-9]+_rc_[0-9]+
const char *p = str + strlen(str);
int n = 3;
while(p > str && n > 0) {
if (*p-- == '_')
n--
}
return p - str;
}
// The rest of the existing pmu_name_len_no_suffix code.
...
}
```
I'd much rather we didn't add bespoke behavior to the tool for every
new PMU. This happened previously when PMUs were merged in
drivers/perf with hex instead of numeric suffixes. We already handle
certain PMUs specially due to their lack of hotplug support:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/arch/arm/util/pmu.c?h=perf-tools-next#n41
And due to event name fiascos:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/builtin-record.c?h=perf-tools-next#n1395
At some point, perf's internals become so forked due to mismatched
conventions that every code path will have a variant. This saddens me
as something that we've much improved this year is being able to say
`perf stat record` on one machine type and then `perf stat report` on
another.
Thanks,
Ian
> Will, do you have any comment on this?
>
> Thanks,
> Besar
>
> >
> > Thanks,
> > Ian
> >
> > > Besar Wicaksono (9):
> > > perf jevents: Add support for NVIDIA Tegra410 UCF PMU aliasing
> > > perf jevents: Add support for NVIDIA Tegra410 PCIE PMU aliasing
> > > perf jevents: Add support for NVIDIA Tegra410 PCIE-TGT PMU aliasing
> > > perf jevents: Add support for NVIDIA Tegra410 CPU Memory Latency
> > PMU
> > > aliasing
> > > perf jevents: Add support for NVIDIA Tegra410 C2C PMU aliasing
> > > perf stat: Check merged PMU instance's cpumasks when skipping zero
> > > counts
> > > perf pmu: Merge PMU instances that match the same comma-separated
> > json
> > > Unit
> > > perf evsel: Name a merged uncore counter after all of its PMUs
> > > perf Documentation: Describe PMU names numbered in more than one
> > place
> > >
> > > .../testing/sysfs-bus-event_source-devices | 14 +
> > > .../arm64/nvidia/t410/uncore-cpu_mem.json | 43 +
> > > .../arm64/nvidia/t410/uncore-nvclink.json | 67 ++
> > > .../arm64/nvidia/t410/uncore-nvdlink.json | 43 +
> > > .../arm64/nvidia/t410/uncore-nvlink_c2c.json | 115 +++
> > > .../arch/arm64/nvidia/t410/uncore-pcie.json | 249 ++++++
> > > .../arm64/nvidia/t410/uncore-pcie_tgt.json | 83 ++
> > > .../arch/arm64/nvidia/t410/uncore-ucf.json | 764
> > ++++++++++++++++++
> > > tools/perf/tests/pmu.c | 134 +++
> > > tools/perf/util/evlist.c | 2 +-
> > > tools/perf/util/evsel.c | 83 +-
> > > tools/perf/util/evsel.h | 2 +-
> > > tools/perf/util/parse-events.c | 2 +-
> > > tools/perf/util/pmu.c | 65 ++
> > > tools/perf/util/pmu.h | 9 +
> > > tools/perf/util/pmus.c | 47 ++
> > > tools/perf/util/pmus.h | 1 +
> > > tools/perf/util/stat-display.c | 20 +
> > > 18 files changed, 1737 insertions(+), 6 deletions(-)
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-cpu_mem.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-nvclink.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-nvdlink.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-nvlink_c2c.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-pcie.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-pcie_tgt.json
> > > create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/uncore-ucf.json
> > >
> > > --
> > > 2.43.0
> > >
More information about the linux-arm-kernel
mailing list