Re: [PATCH] perf vendor events arm64: Add Tegra410 Olympus PMU events

On 30/01/2026 6:08 pm, Besar Wicaksono wrote:

Thank you James and Ian for the comments.
I will try to address the spelling mistakes on v2.

Please see my other comments inline.

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-----Original Message-----
From: James Clark <james.clark@linaro.org>
Sent: Wednesday, January 28, 2026 3:37 AM
To: Ian Rogers <irogers@google.com>; Besar Wicaksono
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Subject: Re: [PATCH] perf vendor events arm64: Add Tegra410 Olympus PMU
events

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On 28/01/2026 8:03 am, Ian Rogers wrote:

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On Tue, Jan 27, 2026 at 3:00 PM Besar Wicaksono

[off-list ref] wrote:

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Add JSON files for NVIDIA Tegra410 Olympus core PMU events.
Also updated the common-and-microarch.json.

Signed-off-by: Besar Wicaksono <redacted>
---
   .../arch/arm64/common-and-microarch.json      |  90 +++
   tools/perf/pmu-events/arch/arm64/mapfile.csv  |   1 +
   .../arch/arm64/nvidia/t410/branch.json        |  45 ++
   .../arch/arm64/nvidia/t410/brbe.json          |   6 +
   .../arch/arm64/nvidia/t410/bus.json           |  48 ++
   .../arch/arm64/nvidia/t410/exception.json     |  62 ++
   .../arch/arm64/nvidia/t410/fp_operation.json  |  78 ++
   .../arch/arm64/nvidia/t410/general.json       |  15 +
   .../arch/arm64/nvidia/t410/l1d_cache.json     | 122 +++
   .../arch/arm64/nvidia/t410/l1i_cache.json     | 114 +++
   .../arch/arm64/nvidia/t410/l2d_cache.json     | 134 ++++
   .../arch/arm64/nvidia/t410/ll_cache.json      | 107 +++
   .../arch/arm64/nvidia/t410/memory.json        |  46 ++
   .../arch/arm64/nvidia/t410/metrics.json       | 722

++++++++++++++++++

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   .../arch/arm64/nvidia/t410/misc.json          | 646 ++++++++++++++++
   .../arch/arm64/nvidia/t410/retired.json       |  94 +++
   .../arch/arm64/nvidia/t410/spe.json           |  42 +
   .../arm64/nvidia/t410/spec_operation.json     | 230 ++++++
   .../arch/arm64/nvidia/t410/stall.json         | 145 ++++
   .../arch/arm64/nvidia/t410/tlb.json           | 158 ++++
   20 files changed, 2905 insertions(+)
   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/branch.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/brbe.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/bus.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/exception.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/fp_operation.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/general.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/l1d_cache.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/l1i_cache.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/l2d_cache.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/ll_cache.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/memory.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/metrics.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/misc.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/retired.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/spe.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/spec_operation.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/stall.json

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   create mode 100644 tools/perf/pmu-

events/arch/arm64/nvidia/t410/tlb.json

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diff --git a/tools/perf/pmu-events/arch/arm64/common-and-

microarch.json b/tools/perf/pmu-events/arch/arm64/common-and-
microarch.json

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index 468cb085d879..6af15776ff17 100644

--- a/tools/perf/pmu-events/arch/arm64/common-and-microarch.json
+++ b/tools/perf/pmu-events/arch/arm64/common-and-microarch.json

@@ -179,6 +179,11 @@
           "EventName": "BUS_CYCLES",
           "BriefDescription": "Bus cycle"
       },
+    {
+        "EventCode": "0x001E",
+        "EventName": "CHAIN",
+        "BriefDescription": "Chain a pair of event counters."
+    },

Cool stuff :-)

For wider counters AMD does something similar, but should this be an
implementation detail rather than an exposed event? How does it
operate as an event?

CHAIN should be excluded from the json, it's used internally by the
driver when you want 64 bit counters. Userspace can't use it because it
can't control where counters are placed to make sure they're adjacent.

Sure, will address this in V2.

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[snip]

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diff --git a/tools/perf/pmu-events/arch/arm64/mapfile.csv

b/tools/perf/pmu-events/arch/arm64/mapfile.csv

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index bb3fa8a33496..7f0eaa702048 100644

--- a/tools/perf/pmu-events/arch/arm64/mapfile.csv
+++ b/tools/perf/pmu-events/arch/arm64/mapfile.csv

@@ -46,3 +46,4 @@
   0x00000000500f0000,v1,ampere/emag,core
   0x00000000c00fac30,v1,ampere/ampereone,core
   0x00000000c00fac40,v1,ampere/ampereonex,core
+0x000000004e0f0100,v1,nvidia/t410,core

diff --git a/tools/perf/pmu-events/arch/arm64/nvidia/t410/branch.json

b/tools/perf/pmu-events/arch/arm64/nvidia/t410/branch.json

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new file mode 100644
index 000000000000..532bc59dc573

--- /dev/null
+++ b/tools/perf/pmu-events/arch/arm64/nvidia/t410/branch.json

@@ -0,0 +1,45 @@
+[
+    {
+        "ArchStdEvent": "BR_MIS_PRED",
+        "PublicDescription": "The Event counts Branches which are

speculatively executed and mis-predicted."

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nit: The capitalization on Event and Branches, as well as other words,
is a little unusual.

If there's nothing specific to this CPU then the public description
could be left out entierly. The common strings already say the same
thing as this:

      {
          "PublicDescription": "Mispredicted or not predicted branch
                                speculatively executed",
          "EventCode": "0x10",
          "EventName": "BR_MIS_PRED",
          "BriefDescription": "Mispredicted or not predicted branch
                               speculatively executed"
      },

I will check on this and other events.

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[snip]

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diff --git a/tools/perf/pmu-events/arch/arm64/nvidia/t410/metrics.json

b/tools/perf/pmu-events/arch/arm64/nvidia/t410/metrics.json

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new file mode 100644
index 000000000000..18c2fd58ee9e

--- /dev/null
+++ b/tools/perf/pmu-events/arch/arm64/nvidia/t410/metrics.json

@@ -0,0 +1,722 @@
+[
+    {
+        "MetricName": "backend_bound",
+        "MetricExpr": "100 * (STALL_SLOT_BACKEND / CPU_SLOT)",
+        "BriefDescription": "This metric is the percentage of total slots that

were stalled due to resource constraints in the backend of the processor.",

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+        "ScaleUnit": "1percent of slots",
+        "MetricGroup": "TopdownL1"

Note, on x86 we place TopdownL1 in the Default metric group so it is
shown by `perf stat` when it isn't given events or metrics to compute.
Perhaps you want to do something similar?
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-

next.git/tree/tools/perf/pmu-events/arch/x86/icelake/icl-
metrics.json?h=tmp.perf-tools-next#n116

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Thanks,
Ian

That's currently true for the Arm topdown metrics in sbsa.json, but we
probably don't actually want this because there aren't enough counters
for the perf stat defaults plus topdown and it results in multiplexing
and bad results.

I was planning to change it but we also don't currently expose the
number of counters available either...

Agree with James, we may not be able to cover all the events in
Default + TopdownL1 group.

Ian, James, in general, is it fine to put some metrics in a same group because
they are actually correlating even though it may cause multiplexing?
For example, "Miss_Ratio" group in this patch provides miss ratio from L1, L2, TLB, etc.
It's convenient to have this and get the miss ratio from all cache levels.
There are many events needed for this group and it might not be accurate due to
multiplexing, but user can get a (rough) broad view in the beginning.

Thanks,
Besar

Yes I think it makes sense to put them all in the same group if they are 
the same feature. I suppose my point about possibly not wanting to open 
TopdownL1 by default is a separate issue to whether they should be in 
the group or not. I just thought it was a good time to mention it.