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

Ilkka Koskinen
2025-03-13T20:12:49Z

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