Re: [PATCH 4/6] perf jevents: Add support for NVIDIA Tegra410 PCIE-TGT PMU aliasing

[Chun-Tse Shao]

On Tue, Oct 20, 2026 at 3:01 PM Besar Wicaksono <bwicaksono@xxxxxxxxxx> wrote:
>
>
>
> > -----Original Message-----
> > From: Ian Rogers <irogers@xxxxxxxxxx>
> > Sent: Monday, October 19, 2026 11:18 PM
> > To: Besar Wicaksono <bwicaksono@xxxxxxxxxx>
> > Cc: acme@xxxxxxxxxx; namhyung@xxxxxxxxxx; linux-tegra@xxxxxxxxxxxxxxx;
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-perf-users@xxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; Vikram Sethi <vsethi@xxxxxxxxxx>; Rich Wiley
> > <rwiley@xxxxxxxxxx>; Sean Kelley <skelley@xxxxxxxxxx>; Matt Ochs
> > <mochs@xxxxxxxxxx>; Raj Joshi <rajjoshi@xxxxxxxxxx>; Thierry Reding
> > <treding@xxxxxxxxxx>; Jon Hunter <jonathanh@xxxxxxxxxx>;
> > john.garry@xxxxxxxxx; will@xxxxxxxxxx; james.clark@xxxxxxxxxx;
> > mike.leach@xxxxxxx; leo.yan@xxxxxxxxx; mark.rutland@xxxxxxx;
> > alexander.shishkin@xxxxxxxxxxxxxxx; jolsa@xxxxxxxxxx;
> > adrian.hunter@xxxxxxxxx; ctshao@xxxxxxxxxx
> > Subject: Re: [PATCH 4/6] perf jevents: Add support for NVIDIA Tegra410
> > PCIE-TGT PMU aliasing
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Mon, Oct 19, 2026 at 9:45 AM Besar Wicaksono
> > <bwicaksono@xxxxxxxxxx> wrote:
> > >
> > > Add alias support for NVIDIA Tegra410 PCIE-TGT PMU events and metrics.
> > >
> > > Signed-off-by: Besar Wicaksono <bwicaksono@xxxxxxxxxx>
> > > ---
> > >  .../nvidia/t410/sys/uncore-pcie_tgt.json      | 93 +++++++++++++++++++
> > >  1 file changed, 93 insertions(+)
> > >  create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/sys/uncore-pcie_tgt.json
> > >
> > > diff --git a/tools/perf/pmu-events/arch/arm64/nvidia/t410/sys/uncore-
> > pcie_tgt.json b/tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/sys/uncore-pcie_tgt.json
> > > new file mode 100644
> > > index 000000000000..74786fc3d578
> > > --- /dev/null
> > > +++ b/tools/perf/pmu-events/arch/arm64/nvidia/t410/sys/uncore-
> > pcie_tgt.json
> > > @@ -0,0 +1,93 @@
> > > +[
> > > +    {
> > > +        "EventCode": "0x4",
> > > +        "EventName": "PCIE_TGT_CYCLES",
> > > +        "BriefDescription": "Counts cycles at the PCIe interface to the Tegra
> > SoC data fabric.",
> > > +        "PublicDescription": "Counts cycles at the PCIe interface to the Tegra
> > SoC data fabric.",
> > > +        "Compat": "1070036b",
> > > +        "Unit": "nvidia_pcie_tgt_pmu_,rc_"
> >
> > It looks like the PMU names are broken because of the _rc_ in their names:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /drivers/perf/arm_cspmu/nvidia_cspmu.c#n901
> > ```
> >    .name_pattern = "nvidia_pcie_pmu_%u_rc_%u",
> > ```
> > The convention is for either a numeric (preferable) or hexadecimal suffix:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /Documentation/ABI/testing/sysfs-bus-event_source-devices
> > Extra information about the PMU belongs in a caps file.
> >
>
> Hi Ian,
>
> Thanks for the pointers.
>
> My interpretation is the ABI document doesn’t prevent driver from naming
> the PMU with multiple numbering format. Other PMUs already did this,
> e.g. HiSilicon hisi_sccl<sccl>_ddrc<n>, Arm NI arm_ni_<ni>_cd_<cd> and
> Qualcomm l3cache_<x>_<y>.

Hi Besar,

The ABI only defines a single _<num> suffix, and that is all perf
supports. perf treats `nvidia_pcie_pmu_0_rc_*` and
`nvidia_pcie_pmu_1_rc_*` as two different PMUs, which is the root
cause of the reporting issues you listed. The hisi_sccl, arm_ni and
Qualcomm PMUs have the same problem.

We can always add a new naming format to the ABI and perf, but each
new format makes PMU name handling harder to maintain.

A PMU per rc, for example, `nvidia_pcie_pmu_<rc>` with one cpu per
socket in its `cpumask` (like Intel uncore_imc_<n>), works with perf
as is.

Thanks,
CT

>
> > By definition nothing can work with wildcard matching using the
> > existing PMU name, so please rename it. If a new suffix convention is
> > necessary then  you should update the ABI and perf tool suffix
> > matching logic like pmu_name_len_no_suffix:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /tools/perf/util/pmus.c#n65
> >
>
> The JSON "Unit" attribute takes a comma-separated form:
> "nvidia_pcie_pmu_,rc_", like HiSilicon's "hisi_sccl,ddrc", which
> perf_pmu__match_wildcard_uncore() matches against "socketX_pmunameY"
> names. The issues seem to be on the reporting side. The counting looks ok.
> I guess JSON "Unit" matching logic is not applied everywhere in perf.
>
> For example below is the counting from my 2-socket machine.
>
> Test workload: read 4 GiB from an NVMe on socket 0 RC 0 and 8 GiB from an NVMe
> on socket 1 RC 0, in parallel (dd ... of=/dev/null iflag=direct).
>
> Counting is correct with the wildcards:
>
> $ perf stat -a -e 'nvidia_pcie_pmu_0_rc*/PCIE_WR_BYTES/,nvidia_pcie_pmu_1_rc*/PCIE_WR_BYTES/' -- <workload>
>      4,362,223,228      nvidia_pcie_pmu_0_rc*/PCIE_WR_BYTES/
>      8,623,751,168      nvidia_pcie_pmu_1_rc*/PCIE_WR_BYTES/
>
> $ perf stat -a --per-socket -e 'nvidia_pcie_pmu_*_rc_0/PCIE_WR_BYTES/' -- <workload>
> S268435456    1      4,362,207,232      nvidia_pcie_pmu_0_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
> S285212672    1      8,724,414,784      nvidia_pcie_pmu_1_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>
> The reporting is where it goes wrong:
>
> 1) RC 0 of all sockets is not merged into one line, and the wildcard
>      ends up in the event name:
>
> $ perf stat -a -e 'nvidia_pcie_pmu_*_rc_0/PCIE_WR_BYTES/' -- <workload>
>      4,311,875,584      nvidia_pcie_pmu_0_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>      8,623,751,168      nvidia_pcie_pmu_1_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>
> 2) The json event is split per socket, and each line is labelled with
>       RC 0 although it is the sum of all RCs of that socket:
>
> $ perf stat -a -e PCIE_WR_BYTES -- <workload>
>      4,311,880,848      nvidia_pcie_pmu_0_rc_0/PCIE_WR_BYTES/
>      8,724,414,784      nvidia_pcie_pmu_1_rc_0/PCIE_WR_BYTES/
>
> 3) The metric is computed per socket, instead of total. With --metric-only both values
>      end up under one header, and the reader can't tell which socket is
>      which:
>
> $ perf stat -a -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
>  MB/s  pcie_avg_wr_bandwidth_to_all_dst
>                                 3113.5                                6227.0
>
> 4) With --per-socket, each row shows both copies: the other socket's
>    copy prints nan, and socket 1's counters is 0 instead of 6:
>
> $ perf stat -a --per-socket -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
>        MB/s  pcie_avg_wr_bandwidth_to_all_dst
> S268435456    6                                 3127.5                                   nan
> S285212672    0                                    nan                                6182.8
>
> $ perf stat -a --per-socket -j -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
> {"socket" : "S268435456", "counters" : 6, "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "3087.8", "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "none"}
> {"socket" : "S285212672", "counters" : 0, "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "none", "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "6247.8"}
>
> All of these, I think, come from perf treating nvidia_pcie_pmu_0_rc_* and
> nvidia_pcie_pmu_1_rc_* as two different PMUs instead of one PMU, i.e
> nvidia_pcie_pmu.
>
> I will investigate further and see if I can come up with a perf patch to fix this.
>
> Regards,
> Besar
>
> > Thanks,
> > Ian Rogers
> >
>

On Tue, Oct 20, 2026 at 3:01 PM Besar Wicaksono <bwicaksono@xxxxxxxxxx> wrote:
>
>
>
> > -----Original Message-----
> > From: Ian Rogers <irogers@xxxxxxxxxx>
> > Sent: Monday, October 19, 2026 11:18 PM
> > To: Besar Wicaksono <bwicaksono@xxxxxxxxxx>
> > Cc: acme@xxxxxxxxxx; namhyung@xxxxxxxxxx; linux-tegra@xxxxxxxxxxxxxxx;
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-perf-users@xxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; Vikram Sethi <vsethi@xxxxxxxxxx>; Rich Wiley
> > <rwiley@xxxxxxxxxx>; Sean Kelley <skelley@xxxxxxxxxx>; Matt Ochs
> > <mochs@xxxxxxxxxx>; Raj Joshi <rajjoshi@xxxxxxxxxx>; Thierry Reding
> > <treding@xxxxxxxxxx>; Jon Hunter <jonathanh@xxxxxxxxxx>;
> > john.garry@xxxxxxxxx; will@xxxxxxxxxx; james.clark@xxxxxxxxxx;
> > mike.leach@xxxxxxx; leo.yan@xxxxxxxxx; mark.rutland@xxxxxxx;
> > alexander.shishkin@xxxxxxxxxxxxxxx; jolsa@xxxxxxxxxx;
> > adrian.hunter@xxxxxxxxx; ctshao@xxxxxxxxxx
> > Subject: Re: [PATCH 4/6] perf jevents: Add support for NVIDIA Tegra410
> > PCIE-TGT PMU aliasing
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Mon, Oct 19, 2026 at 9:45 AM Besar Wicaksono
> > <bwicaksono@xxxxxxxxxx> wrote:
> > >
> > > Add alias support for NVIDIA Tegra410 PCIE-TGT PMU events and metrics.
> > >
> > > Signed-off-by: Besar Wicaksono <bwicaksono@xxxxxxxxxx>
> > > ---
> > >  .../nvidia/t410/sys/uncore-pcie_tgt.json      | 93 +++++++++++++++++++
> > >  1 file changed, 93 insertions(+)
> > >  create mode 100644 tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/sys/uncore-pcie_tgt.json
> > >
> > > diff --git a/tools/perf/pmu-events/arch/arm64/nvidia/t410/sys/uncore-
> > pcie_tgt.json b/tools/perf/pmu-
> > events/arch/arm64/nvidia/t410/sys/uncore-pcie_tgt.json
> > > new file mode 100644
> > > index 000000000000..74786fc3d578
> > > --- /dev/null
> > > +++ b/tools/perf/pmu-events/arch/arm64/nvidia/t410/sys/uncore-
> > pcie_tgt.json
> > > @@ -0,0 +1,93 @@
> > > +[
> > > +    {
> > > +        "EventCode": "0x4",
> > > +        "EventName": "PCIE_TGT_CYCLES",
> > > +        "BriefDescription": "Counts cycles at the PCIe interface to the Tegra
> > SoC data fabric.",
> > > +        "PublicDescription": "Counts cycles at the PCIe interface to the Tegra
> > SoC data fabric.",
> > > +        "Compat": "1070036b",
> > > +        "Unit": "nvidia_pcie_tgt_pmu_,rc_"
> >
> > It looks like the PMU names are broken because of the _rc_ in their names:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /drivers/perf/arm_cspmu/nvidia_cspmu.c#n901
> > ```
> >    .name_pattern = "nvidia_pcie_pmu_%u_rc_%u",
> > ```
> > The convention is for either a numeric (preferable) or hexadecimal suffix:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /Documentation/ABI/testing/sysfs-bus-event_source-devices
> > Extra information about the PMU belongs in a caps file.
> >
>
> Hi Ian,
>
> Thanks for the pointers.
>
> My interpretation is the ABI document doesn’t prevent driver from naming
> the PMU with multiple numbering format. Other PMUs already did this,
> e.g. HiSilicon hisi_sccl<sccl>_ddrc<n>, Arm NI arm_ni_<ni>_cd_<cd> and
> Qualcomm l3cache_<x>_<y>.
>
> > By definition nothing can work with wildcard matching using the
> > existing PMU name, so please rename it. If a new suffix convention is
> > necessary then  you should update the ABI and perf tool suffix
> > matching logic like pmu_name_len_no_suffix:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree
> > /tools/perf/util/pmus.c#n65
> >
>
> The JSON "Unit" attribute takes a comma-separated form:
> "nvidia_pcie_pmu_,rc_", like HiSilicon's "hisi_sccl,ddrc", which
> perf_pmu__match_wildcard_uncore() matches against "socketX_pmunameY"
> names. The issues seem to be on the reporting side. The counting looks ok.
> I guess JSON "Unit" matching logic is not applied everywhere in perf.
>
> For example below is the counting from my 2-socket machine.
>
> Test workload: read 4 GiB from an NVMe on socket 0 RC 0 and 8 GiB from an NVMe
> on socket 1 RC 0, in parallel (dd ... of=/dev/null iflag=direct).
>
> Counting is correct with the wildcards:
>
> $ perf stat -a -e 'nvidia_pcie_pmu_0_rc*/PCIE_WR_BYTES/,nvidia_pcie_pmu_1_rc*/PCIE_WR_BYTES/' -- <workload>
>      4,362,223,228      nvidia_pcie_pmu_0_rc*/PCIE_WR_BYTES/
>      8,623,751,168      nvidia_pcie_pmu_1_rc*/PCIE_WR_BYTES/
>
> $ perf stat -a --per-socket -e 'nvidia_pcie_pmu_*_rc_0/PCIE_WR_BYTES/' -- <workload>
> S268435456    1      4,362,207,232      nvidia_pcie_pmu_0_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
> S285212672    1      8,724,414,784      nvidia_pcie_pmu_1_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>
> The reporting is where it goes wrong:
>
> 1) RC 0 of all sockets is not merged into one line, and the wildcard
>      ends up in the event name:
>
> $ perf stat -a -e 'nvidia_pcie_pmu_*_rc_0/PCIE_WR_BYTES/' -- <workload>
>      4,311,875,584      nvidia_pcie_pmu_0_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>      8,623,751,168      nvidia_pcie_pmu_1_rc_0/nvidia_pcie_pmu_*_rc_0,PCIE_WR_BYTES/
>
> 2) The json event is split per socket, and each line is labelled with
>       RC 0 although it is the sum of all RCs of that socket:
>
> $ perf stat -a -e PCIE_WR_BYTES -- <workload>
>      4,311,880,848      nvidia_pcie_pmu_0_rc_0/PCIE_WR_BYTES/
>      8,724,414,784      nvidia_pcie_pmu_1_rc_0/PCIE_WR_BYTES/
>
> 3) The metric is computed per socket, instead of total. With --metric-only both values
>      end up under one header, and the reader can't tell which socket is
>      which:
>
> $ perf stat -a -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
>  MB/s  pcie_avg_wr_bandwidth_to_all_dst
>                                 3113.5                                6227.0
>
> 4) With --per-socket, each row shows both copies: the other socket's
>    copy prints nan, and socket 1's counters is 0 instead of 6:
>
> $ perf stat -a --per-socket -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
>        MB/s  pcie_avg_wr_bandwidth_to_all_dst
> S268435456    6                                 3127.5                                   nan
> S285212672    0                                    nan                                6182.8
>
> $ perf stat -a --per-socket -j -M pcie_avg_wr_bandwidth_to_all_dst --metric-only -- <workload>
> {"socket" : "S268435456", "counters" : 6, "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "3087.8", "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "none"}
> {"socket" : "S285212672", "counters" : 0, "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "none", "MB/s  pcie_avg_wr_bandwidth_to_all_dst" : "6247.8"}
>
> All of these, I think, come from perf treating nvidia_pcie_pmu_0_rc_* and
> nvidia_pcie_pmu_1_rc_* as two different PMUs instead of one PMU, i.e
> nvidia_pcie_pmu.
>
> I will investigate further and see if I can come up with a perf patch to fix this.
>
> Regards,
> Besar
>
> > Thanks,
> > Ian Rogers
> >
>