1 files changed, 107 insertions, 0 deletions
diff --git a/tools/perf/python/futex-contention.py b/tools/perf/python/futex-contention.py
new file mode 100755
index 000000000000..097663d929b7
--- /dev/null
+++ b/tools/perf/python/futex-contention.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""Measures futex contention."""
+from __future__ import annotations
+
+import argparse
+from collections import defaultdict
+from typing import Dict, Tuple
+import perf
+
+class LockStats:
+    """Aggregate lock contention information."""
+    def __init__(self) -> None:
+        self.count = 0
+        self.total_time = 0
+        self.min_time = 0
+        self.max_time = 0
+
+    def add(self, duration: int) -> None:
+        """Add a new duration measurement."""
+        self.count += 1
+        self.total_time += duration
+        if self.count == 1:
+            self.min_time = duration
+            self.max_time = duration
+        else:
+            self.min_time = min(self.min_time, duration)
+            self.max_time = max(self.max_time, duration)
+
+    def avg(self) -> float:
+        """Return average duration."""
+        return self.total_time / self.count if self.count > 0 else 0.0
+
+process_names: Dict[int, str] = {}
+start_times: Dict[int, Tuple[int, int]] = {}
+session = None
+durations: Dict[Tuple[int, int], LockStats] = defaultdict(LockStats)
+
+FUTEX_WAIT = 0
+FUTEX_PRIVATE_FLAG = 128
+FUTEX_CLOCK_REALTIME = 256
+# Mask out FUTEX_PRIVATE_FLAG and FUTEX_CLOCK_REALTIME so variants such as
+# FUTEX_WAIT_PRIVATE (0 | 128) match the base FUTEX_WAIT command.
+FUTEX_CMD_MASK = ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
+
+
+def handle_start(pid: int, tid: int, uaddr: int, op: int, start_time: int) -> None:
+    """Handle a futex sys_enter event."""
+    if (op & FUTEX_CMD_MASK) != FUTEX_WAIT:
+        return
+    try:
+        if session:
+            process = session.find_thread(pid, tid)
+            if process:
+                process_names[tid] = process.comm() or "unknown"
+    except (TypeError, AttributeError):
+        pass
+    if tid not in process_names:
+        process_names[tid] = "unknown"
+
+    start_times[tid] = (uaddr, start_time)
+
+def handle_end(tid: int, end_time: int) -> None:
+    """Handle a futex sys_exit event."""
+    if tid not in start_times:
+        return
+    (uaddr, start_time) = start_times[tid]
+    del start_times[tid]
+    durations[(tid, uaddr)].add(end_time - start_time)
+
+def process_event(sample: perf.sample_event) -> None:
+    """Process a single sample event."""
+    event_name = str(sample.evsel)
+    if event_name.startswith("evsel(") and event_name.endswith(")"):
+        event_name = event_name[6:-1]
+    if event_name.startswith("syscalls:sys_enter_futex"):
+        uaddr = getattr(sample, "uaddr", None)
+        op = getattr(sample, "op", None)
+        if uaddr is None or op is None:
+            return  # Tracepoint fields missing, skip silent attribution to 0
+        handle_start(getattr(sample, "sample_pid", sample.sample_tid),
+                     sample.sample_tid, uaddr, op, sample.sample_time)
+    elif event_name.startswith("syscalls:sys_exit_futex"):
+        handle_end(sample.sample_tid, sample.sample_time)
+
+
+if __name__ == "__main__":
+    ap = argparse.ArgumentParser(description="Measure futex contention")
+    ap.add_argument("-i", "--input", default="perf.data", help="Input file name")
+    args = ap.parse_args()
+
+    try:
+        session = perf.session(perf.data(args.input), sample=process_event)
+        try:
+            session.process_events()
+        except KeyboardInterrupt:
+            pass
+
+        for ((t, u), stats) in sorted(durations.items()):
+            avg_ns = stats.avg()
+            print(f"{process_names.get(t, 'unknown')}[{t}] lock {u:x} contended "
+                  f"{stats.count} times, {avg_ns:.0f} avg ns "
+                  f"[max: {stats.max_time} ns, min {stats.min_time} ns]")
+    finally:
+        # Break the reference cycle between the global session and the
+        # process_event callback so the C perf.session object is freed.
+        session = None