[PATCH 0/2] perf vendor events arm64: AmpereOne/AmpereOneX: Add a new errata and fix metrics calculations

[PATCH 0/2] perf vendor events arm64: AmpereOne/AmpereOneX: Add a new errata and fix metrics calculations

[Ilkka Koskinen]

Add an errata reference to a impacted event and fix metrics calculation
caused by a scaling issue.

Ilkka Koskinen (2):
  perf vendor events arm64: AmpereOne/AmpereOneX: Mark LD_RETIRED
    impacted by errata
  perf vendor events arm64 AmpereOneX: Fix frontend_bound calculation

 .../pmu-events/arch/arm64/ampere/ampereone/memory.json |  4 +++-
 .../arch/arm64/ampere/ampereonex/memory.json           |  4 +++-
 .../arch/arm64/ampere/ampereonex/metrics.json          | 10 +++++-----
 3 files changed, 11 insertions(+), 7 deletions(-)

-- 
2.47.0

[PATCH 1/2] perf vendor events arm64: AmpereOne/AmpereOneX: Mark LD_RETIRED impacted by errata

[Ilkka Koskinen]

Atomic instructions are both memory-reading and memory-writing
instructions and so should be counted by both LD_RETIRED and ST_RETIRED
performance monitoring events. However LD_RETIRED does not count atomic
instructions.

Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
---
 tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json | 4 +++-
 .../perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json  | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
index 0711782bfa6b..13382d29b25f 100644
--- a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
+++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
@@ -1,6 +1,8 @@
 [
     {
-        "ArchStdEvent": "LD_RETIRED"
+        "ArchStdEvent": "LD_RETIRED",
+        "Errata": "Errata AC03_CPU_52",
+        "BriefDescription": "Instruction architecturally executed, condition code check pass, load. Impacted by errata -"
     },
     {
         "ArchStdEvent": "MEM_ACCESS_RD"
diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json
index a211d94aacde..6c06bc928415 100644
--- a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json
+++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json
@@ -1,6 +1,8 @@
 [
     {
-        "ArchStdEvent": "LD_RETIRED"
+        "ArchStdEvent": "LD_RETIRED",
+        "Errata": "Errata AC04_CPU_21",
+        "BriefDescription": "Instruction architecturally executed, condition code check pass, load. Impacted by errata -"
     },
     {
         "ArchStdEvent": "MEM_ACCESS_RD"
-- 
2.47.0

Re: [PATCH 1/2] perf vendor events arm64: AmpereOne/AmpereOneX: Mark LD_RETIRED impacted by errata

[James Clark]

On 13/03/2025 8:15 pm, Ilkka Koskinen wrote:
> Atomic instructions are both memory-reading and memory-writing
> instructions and so should be counted by both LD_RETIRED and ST_RETIRED
> performance monitoring events. However LD_RETIRED does not count atomic
> instructions.
> 
> Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
> ---
>   tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json | 4 +++-
>   .../perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json  | 4 +++-
>   2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
> index 0711782bfa6b..13382d29b25f 100644
> --- a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
> +++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
> @@ -1,6 +1,8 @@
>   [
>       {
> -        "ArchStdEvent": "LD_RETIRED"
> +        "ArchStdEvent": "LD_RETIRED",
> +        "Errata": "Errata AC03_CPU_52",
> +        "BriefDescription": "Instruction architecturally executed, condition code check pass, load. Impacted by errata -"

I think this could also have a 'Fixes:' tag, either way:

Reviewed-by: James Clark <james.clark@linaro.org>

Re: [PATCH 1/2] perf vendor events arm64: AmpereOne/AmpereOneX: Mark LD_RETIRED impacted by errata

[Ilkka Koskinen]

Hi James,

On Tue, 18 Mar 2025, James Clark wrote:
> On 13/03/2025 8:15 pm, Ilkka Koskinen wrote:
>> Atomic instructions are both memory-reading and memory-writing
>> instructions and so should be counted by both LD_RETIRED and ST_RETIRED
>> performance monitoring events. However LD_RETIRED does not count atomic
>> instructions.
>> 
>> Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
>> ---
>>   tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json | 4 +++-
>>   .../perf/pmu-events/arch/arm64/ampere/ampereonex/memory.json  | 4 +++-
>>   2 files changed, 6 insertions(+), 2 deletions(-)
>> 
>> diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json 
>> b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
>> index 0711782bfa6b..13382d29b25f 100644
>> --- a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
>> +++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/memory.json
>> @@ -1,6 +1,8 @@
>>   [
>>       {
>> -        "ArchStdEvent": "LD_RETIRED"
>> +        "ArchStdEvent": "LD_RETIRED",
>> +        "Errata": "Errata AC03_CPU_52",
>> +        "BriefDescription": "Instruction architecturally executed, 
>> condition code check pass, load. Impacted by errata -"
>
> I think this could also have a 'Fixes:' tag, either way:
>
> Reviewed-by: James Clark <james.clark@linaro.org>

Yeah, that's true. I guess, I was thinking about using 'Fixes' more on 
broken patches rather than when adding a patch dealing with a new hw 
errata. Well, given you're find with this, I don't think I'll resubmit it
with a Fixes tag this time.

Cheers, Ilkka

[PATCH 2/2] perf vendor events arm64 AmpereOneX: Fix frontend_bound calculation

[Ilkka Koskinen]

frontend_bound metrics was miscalculated due to different scaling in
a couple of metrics it depends on. Change the scaling to match with
AmpereOne.

Fixes: 16438b652b46 ("perf vendor events arm64 AmpereOneX: Add core PMU events and metrics")
Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
---
 .../arch/arm64/ampere/ampereonex/metrics.json          | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
index c5d1d22bd034..5228f94a793f 100644
--- a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
+++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
@@ -229,19 +229,19 @@
     },
     {
         "MetricName": "slots_lost_misspeculation_fraction",
-        "MetricExpr": "(OP_SPEC - OP_RETIRED) / (CPU_CYCLES * #slots)",
+        "MetricExpr": "100 * (OP_SPEC - OP_RETIRED) / (CPU_CYCLES * #slots)",
         "BriefDescription": "Fraction of slots lost due to misspeculation",
         "DefaultMetricgroupName": "TopdownL1",
         "MetricGroup": "Default;TopdownL1",
-        "ScaleUnit": "100percent of slots"
+        "ScaleUnit": "1percent of slots"
     },
     {
         "MetricName": "retired_fraction",
-        "MetricExpr": "OP_RETIRED / (CPU_CYCLES * #slots)",
+        "MetricExpr": "100 * OP_RETIRED / (CPU_CYCLES * #slots)",
         "BriefDescription": "Fraction of slots retiring, useful work",
         "DefaultMetricgroupName": "TopdownL1",
         "MetricGroup": "Default;TopdownL1",
-        "ScaleUnit": "100percent of slots"
+        "ScaleUnit": "1percent of slots"
     },
     {
         "MetricName": "backend_core",
@@ -266,7 +266,7 @@
     },
     {
         "MetricName": "frontend_bandwidth",
-        "MetricExpr": "frontend_bound - frontend_latency",
+        "MetricExpr": "frontend_bound - 100 * frontend_latency",
         "BriefDescription": "Fraction of slots the CPU did not dispatch at full bandwidth - able to dispatch partial slots only (1, 2, or 3 uops)",
         "MetricGroup": "TopdownL2",
         "ScaleUnit": "1percent of slots"
-- 
2.47.0

Re: [PATCH 2/2] perf vendor events arm64 AmpereOneX: Fix frontend_bound calculation

[James Clark]

On 13/03/2025 8:15 pm, Ilkka Koskinen wrote:
> frontend_bound metrics was miscalculated due to different scaling in
> a couple of metrics it depends on. Change the scaling to match with
> AmpereOne.
> 
> Fixes: 16438b652b46 ("perf vendor events arm64 AmpereOneX: Add core PMU events and metrics")
> Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
> ---
>   .../arch/arm64/ampere/ampereonex/metrics.json          | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
> index c5d1d22bd034..5228f94a793f 100644
> --- a/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
> +++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereonex/metrics.json
> @@ -229,19 +229,19 @@
>       },
>       {
>           "MetricName": "slots_lost_misspeculation_fraction",
> -        "MetricExpr": "(OP_SPEC - OP_RETIRED) / (CPU_CYCLES * #slots)",
> +        "MetricExpr": "100 * (OP_SPEC - OP_RETIRED) / (CPU_CYCLES * #slots)",
>           "BriefDescription": "Fraction of slots lost due to misspeculation",
>           "DefaultMetricgroupName": "TopdownL1",
>           "MetricGroup": "Default;TopdownL1",
> -        "ScaleUnit": "100percent of slots"
> +        "ScaleUnit": "1percent of slots"
>       },
>       {
>           "MetricName": "retired_fraction",
> -        "MetricExpr": "OP_RETIRED / (CPU_CYCLES * #slots)",
> +        "MetricExpr": "100 * OP_RETIRED / (CPU_CYCLES * #slots)",
>           "BriefDescription": "Fraction of slots retiring, useful work",
>           "DefaultMetricgroupName": "TopdownL1",
>           "MetricGroup": "Default;TopdownL1",
> -        "ScaleUnit": "100percent of slots"
> +        "ScaleUnit": "1percent of slots"

I never considered that ScaleUnit could be an issue when the metric was 
included in other metrics with different scales. Seems like an easy trap.

Reviewed-by: James Clark <james.clark@linaro.org>

Re: [PATCH 0/2] perf vendor events arm64: AmpereOne/AmpereOneX: Add a new errata and fix metrics calculations

[Namhyung Kim]

On Thu, 13 Mar 2025 20:15:57 +0000, Ilkka Koskinen wrote:
> Add an errata reference to a impacted event and fix metrics calculation
> caused by a scaling issue.
> 
> Ilkka Koskinen (2):
>   perf vendor events arm64: AmpereOne/AmpereOneX: Mark LD_RETIRED
>     impacted by errata
>   perf vendor events arm64 AmpereOneX: Fix frontend_bound calculation
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung