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 b6cdeb4f09fe..f51a044b8005 100755
--- a/tools/perf/pmu-events/amd_metrics.py
+++ b/tools/perf/pmu-events/amd_metrics.py
@@ -3,8 +3,9 @@
 import argparse
 import math
 import os
-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)
 
 # Global command line arguments.
 _args = None
@@ -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(
+        "lpm_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.
 
@@ -57,6 +68,7 @@ def main() -> None:
     LoadEvents(directory)
 
     all_metrics = MetricGroup("", [
+        Idle(),
         Rapl(),
     ])
 
-- 
2.51.2.1041.gc1ab5b90ca-goog