Compute using the msr PMU the percentage of wallclock cycles where the
CPUs are in a low power state.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/pmu-events/amd_metrics.py | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/perf/pmu-events/amd_metrics.py b/tools/perf/pmu-events/amd_metrics.py
index fd420466b999..e069b95d6470 100755
--- a/tools/perf/pmu-events/amd_metrics.py
+++ b/tools/perf/pmu-events/amd_metrics.py
@@ -1,7 +1,8 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
-from metric import (d_ratio, has_event, Event, JsonEncodeMetric, JsonEncodeMetricGroupDescriptions,
-                    LoadEvents, Metric, MetricGroup, Select)
+from metric import (d_ratio, has_event, max, Event, JsonEncodeMetric,
+                    JsonEncodeMetricGroupDescriptions, LoadEvents, Metric,
+                    MetricGroup, Select)
 import argparse
 import json
 import math
@@ -12,6 +13,16 @@ _args = None
 
 interval_sec = Event("duration_time")
 
+def Idle() -> Metric:
+  cyc = Event("msr/mperf/")
+  tsc = Event("msr/tsc/")
+  low = max(tsc - cyc, 0)
+  return Metric(
+      "idle",
+      "Percentage of total wallclock cycles where CPUs are in low power state (C1 or deeper sleep state)",
+      d_ratio(low, tsc), "100%")
+
+
 def Rapl() -> MetricGroup:
   """Processor socket power consumption estimate.
 
@@ -55,6 +66,7 @@ def main() -> None:
   LoadEvents(directory)
 
   all_metrics = MetricGroup("", [
+      Idle(),
       Rapl(),
   ])
 
-- 
2.46.1.824.gd892dcdcdd-goog