[PATCH v1 51/58] perf wakeup-latency: Port wakeup-latency to use python module

[Ian Rogers]

Port the legacy Perl script wakeup-latency.pl to a python script using
the perf module in tools/perf/python.

The new script uses a class-based architecture and leverages the
perf.session API for event processing.

It measures wakeup latency by tracking timestamps of
sched:sched_wakeup and sched:sched_switch events.

Complications:
- Used min() and max() built-in functions instead of if blocks to
  satisfy pylint recommendations.
- pylint warns about the module name not being snake_case, but it is
  kept for consistency with the original script name.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/python/wakeup-latency.py | 85 +++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100755 tools/perf/python/wakeup-latency.py

diff --git a/tools/perf/python/wakeup-latency.py b/tools/perf/python/wakeup-latency.py
new file mode 100755
index 000000000000..109b751aefb3
--- /dev/null
+++ b/tools/perf/python/wakeup-latency.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+"""Display avg/min/max wakeup latency."""
+
+import argparse
+from collections import defaultdict
+import sys
+from typing import Optional, Dict
+import perf
+
+class WakeupLatency:
+    """Tracks and displays wakeup latency statistics."""
+    def __init__(self) -> None:
+        self.last_wakeup: Dict[int, int] = defaultdict(int)
+        self.max_wakeup_latency = 0
+        self.min_wakeup_latency = 1000000000
+        self.total_wakeup_latency = 0
+        self.total_wakeups = 0
+        self.unhandled: Dict[str, int] = defaultdict(int)
+        self.session: Optional[perf.session] = None
+
+    def process_event(self, sample: perf.sample_event) -> None:
+        """Process events."""
+        event_name = str(sample.evsel)
+        sample_time = sample.sample_time
+        cpu = sample.sample_cpu
+
+        if "sched:sched_wakeup" in event_name:
+            try:
+                target_cpu = sample.target_cpu
+                self.last_wakeup[target_cpu] = sample_time
+            except AttributeError:
+                pass
+        elif "sched:sched_switch" in event_name:
+            wakeup_ts = self.last_wakeup[cpu]
+            if wakeup_ts:
+                latency = sample_time - wakeup_ts
+                self.max_wakeup_latency = max(self.max_wakeup_latency, latency)
+                self.min_wakeup_latency = min(self.min_wakeup_latency, latency)
+                self.total_wakeup_latency += latency
+                self.total_wakeups += 1
+            self.last_wakeup[cpu] = 0
+        else:
+            self.unhandled[event_name] += 1
+
+    def print_totals(self) -> None:
+        """Print summary statistics."""
+        print("wakeup_latency stats:\n")
+        print(f"total_wakeups: {self.total_wakeups}")
+        if self.total_wakeups:
+            avg = self.total_wakeup_latency // self.total_wakeups
+            print(f"avg_wakeup_latency (ns): {avg}")
+        else:
+            print("avg_wakeup_latency (ns): N/A")
+        print(f"min_wakeup_latency (ns): {self.min_wakeup_latency}")
+        print(f"max_wakeup_latency (ns): {self.max_wakeup_latency}")
+
+        if self.unhandled:
+            print("\nunhandled events:\n")
+            print(f"{'event':<40s}  {'count':>10s}")
+            print(f"{'-'*40}  {'-'*10}")
+            for event_name, count in self.unhandled.items():
+                print(f"{event_name:<40s}  {count:10d}")
+
+    def run(self, input_file: str) -> None:
+        """Run the session."""
+        self.session = perf.session(perf.data(input_file), sample=self.process_event)
+        self.session.process_events()
+        self.print_totals()
+
+def main() -> None:
+    """Main function."""
+    parser = argparse.ArgumentParser(description="Trace wakeup latency")
+    parser.add_argument("-i", "--input", default="perf.data", help="Input file")
+    args = parser.parse_args()
+
+    analyzer = WakeupLatency()
+    try:
+        analyzer.run(args.input)
+    except IOError as e:
+        print(e, file=sys.stderr)
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()
-- 
2.54.0.rc1.513.gad8abe7a5a-goog