From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f197.google.com (mail-dy1-f197.google.com [74.125.82.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C93CA3AB288 for ; Sat, 26 Sep 2026 06:21:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790403720; cv=none; b=p42rSYP6mV/YT36eMcW7FpEt2ZCcSrWe4ucnfh1gO4t0+U709keDgGKSUwEx55mX7WeGjz/PZtDLuHBQThpS4SCKNGKrtYNdBde9O4c61qGh1YOlcWXJO1wDeoqrhoIIuGn3/NH0EbWPRjt+VybbKGVwCG/pF18eRiLUELLGRT8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790403720; c=relaxed/simple; bh=OdQaxxBWGVLFMntT6qyopuR+76jAtK0eaJUZ3r27fro=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=DPRAgX+eUyzbze82e232KXLIVKumB+5LkOzD4o0jNiZjXKBcqARdTf/Cr63+pHD7+wLvrLZSupXAuuKtKLx+03p6si6E+RZjDIQ6TSH4G8e/VJgeBSqCBWCk8p3FbcEyOzBhkBFMZ8z2pTuRjCl01ELEdYBGBRcvMih1dnPjYKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=W7TKOoy0; arc=none smtp.client-ip=74.125.82.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--irogers.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="W7TKOoy0" Received: by mail-dy1-f197.google.com with SMTP id 5a478bee46e88-33f01b74124so2244433eec.1 for ; Fri, 25 Sep 2026 23:21:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790403718; x=1791008518; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=kwitgM2dG+fjlRoMvxPwow02it5ysqWzTJNZ0m0HMOc=; b=W7TKOoy04eeYM9r4QPP7opk4e/shXlHJmNlUV+xVJ6ehjzbnfXkRQdpgBowMzdX6a7 yQMAgyLpNkBaktp1zRPMdJItArgyHlowLPYpMDkAFVtZp3tKCBoLnwTYTQAPlQ9B3ghZ xq9ZFWhY61k+RcAH1BR5IJuSr/RbsuRrF24WJ9ECM9p+4kUqd7w5UNvoFIqNUDl+mQr3 FhEe3t/JvkP6oz18lXNN0G1He3dZo9pycH7xESg8Fft0/UKYVBRuxxjhpEWNMImu4mN/ pX8ljZvcHwp/rqp30yTjXYCnpArtSocepUrL0y8YPOkuwNbEkwZJqDm8SSyNEhK7DLJR P/Ng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790403718; x=1791008518; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=kwitgM2dG+fjlRoMvxPwow02it5ysqWzTJNZ0m0HMOc=; b=lzooAZwUnJH2J227peLG6CmpFAHpptEnu8k8nYztVWjglWXzy/VjNT4APF7a65eboX aqExxUiXQyYJet5o9XPi+GfNQOm9T3BKzbbpnWZzf63oKLCadRMkDpMD+YD6Se7mLfaj 8mqYcgulGKZ+oBd39WpKTuVOr701SZoBQHfu68Cr6BLtJ/pb64/E8h68jhLy+wBwABVN 23Fwb9/c1XbPAtTqq6sgb+ImavWVGJw9lU2Tqi+vr+ZGyLjRuDi1u0v24f4fgOo5Xcbs v9EYL57jvOSikwy3L0onlfXaF2qd+qNw1Q25oBr2axrArgPRPA7c+mgPyLwfwSLNUM+U 3t6g== X-Forwarded-Encrypted: i=1; AKwUvByi5upplIVgzJ6dXRAy8/zuUEwByvLl7yUFjE16t/bdG9f4rl1M3TdmTdFekCtjAy6pjzKemY0uzvHCQlM=@vger.kernel.org X-Gm-Message-State: AFuF++k2oP8qMUshy116/0SpSG511m4UYqRZx93YcD1tLkRuA4VQeTF+ rGPdyUohAObaMcIOluIfGQ7t3tnJ2G3QKBPdnWbp1VgaBrKmG1lXekTKA32lHno8vQAs2o/qeG+ bcce7iKTTwQ== X-Received: from dybhi48.prod.google.com ([2002:a05:7301:29b0:b0:33c:382b:2d9c]) (user=irogers job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:fa9:b0:13c:e1e2:fc86 with SMTP id a92af1059eb24-146ce49209fmr2846765c88.4.1790403717599; Fri, 25 Sep 2026 23:21:57 -0700 (PDT) Date: Fri, 25 Sep 2026 23:19:57 -0700 In-Reply-To: <20260926062029.800743-1-irogers@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260923181213.3032038-1-irogers@google.com> <20260926062029.800743-1-irogers@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260926062029.800743-31-irogers@google.com> Subject: [PATCH v4 30/49] perf python: Port futex-contention to perf module From: Ian Rogers To: irogers@google.com, acme@kernel.org, alice.mei.rogers@gmail.com, james.clark@linaro.org, leo.yan@linux.dev, namhyung@kernel.org Cc: adrian.hunter@intel.com, dapeng1.mi@linux.intel.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, tmricht@linux.ibm.com Content-Type: text/plain; charset="UTF-8" Port tools/perf/scripts/python/futex-contention.py to a standalone script in tools/perf/python/ using the perf module. Avoiding the embedded interpreter overhead improves execution speed by ~3.2x: ``` $ perf record -e syscalls:sys_*_futex -a sleep 1 ... $ time perf script tools/perf/scripts/python/futex-contention.py ... real 0m1.007s user 0m0.935s sys 0m0.072s $ time python3 tools/perf/python/futex-contention.py ... real 0m0.314s user 0m0.259s sys 0m0.056s ``` Additional improvements compared to the legacy script: - Consolidate per-(tid, uaddr) contention count, total_time, min_time, and max_time into a single LockStats class instead of maintaining three separate dictionaries. - Validate that uaddr and op tracepoint attributes are present on syscalls:sys_enter_futex samples rather than silently attributing missing fields to uaddr=0, op=0 (FUTEX_WAIT). - Add -i/--input CLI option support via argparse and full type annotations. Add a shell test (test_futex_contention_python.sh) to verify the standalone script. Assisted-by: Antigravity:gemini-3.1-pro Signed-off-by: Ian Rogers --- tools/perf/python/futex-contention.py | 107 ++++++++++++++++ .../shell/test_futex_contention_python.sh | 115 ++++++++++++++++++ 2 files changed, 222 insertions(+) create mode 100755 tools/perf/python/futex-contention.py create mode 100755 tools/perf/tests/shell/test_futex_contention_python.sh 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 diff --git a/tools/perf/tests/shell/test_futex_contention_python.sh b/tools/perf/tests/shell/test_futex_contention_python.sh new file mode 100755 index 000000000000..26b13d263d20 --- /dev/null +++ b/tools/perf/tests/shell/test_futex_contention_python.sh @@ -0,0 +1,115 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# futex-contention python test + +set -e + +shelldir=$(dirname "$0") +# shellcheck source=lib/setup_python.sh +. "${shelldir}"/lib/setup_python.sh + +# If we don't have the perf python module, we can't test +if ! "$PYTHON" -c 'import perf' > /dev/null 2>&1; then + echo "Skipping test, perf python module not found" + exit 2 +fi + +script_dir="$(dirname "$0")/../../python" +script_path="${script_dir}/futex-contention.py" + +if ! perf check feature -q libtraceevent > /dev/null 2>&1; then + echo "Skipping test, libtraceevent is disabled" + exit 2 +fi + +if [ ! -f "$script_path" ]; then + echo "Skipping test, futex-contention.py not found at $script_path" + exit 2 +fi + +err=0 +temp_data="" +temp_out="" + +cleanup() { + rm -f "${temp_data}" "${temp_out}" +} + +trap 'cleanup' EXIT TERM INT + +temp_data=$(mktemp /tmp/perf.data.XXXXXX) +temp_out=$(mktemp /tmp/perf.out.XXXXXX) + +test_synthetic() { + echo "Testing futex-contention.py synthetic events..." + if ! "$PYTHON" - "$script_path" << 'EOF' +import importlib.util +import sys +from types import SimpleNamespace + +spec = importlib.util.spec_from_file_location("futex_contention", sys.argv[1]) +mod = importlib.util.module_from_spec(spec) +spec.loader.exec_module(mod) + +enter_sample = SimpleNamespace( + evsel="evsel(syscalls:sys_enter_futex:k)", + sample_pid=1234, + sample_tid=1234, + uaddr=0xdeadbeef, + op=mod.FUTEX_WAIT | mod.FUTEX_PRIVATE_FLAG, + sample_time=1000, +) +exit_sample = SimpleNamespace( + evsel="evsel(syscalls:sys_exit_futex:k)", + sample_pid=1234, + sample_tid=1234, + sample_time=2500, +) + +mod.process_event(enter_sample) +mod.process_event(exit_sample) + +stats = mod.durations.get((1234, 0xdeadbeef)) +assert stats is not None and stats.count == 1, f"Unexpected stats: {stats}" +assert stats.min_time == 1500 and stats.max_time == 1500 and stats.avg() == 1500.0 +line = (f"{mod.process_names.get(1234, 'unknown')}[1234] lock {0xdeadbeef:x} " + f"contended {stats.count} times, {stats.avg():.0f} avg ns " + f"[max: {stats.max_time} ns, min {stats.min_time} ns]") +expected = "unknown[1234] lock deadbeef contended 1 times, 1500 avg ns [max: 1500 ns, min 1500 ns]" +assert line == expected, line +EOF + then + echo "Synthetic test failed." + err=1 + else + echo "Synthetic test passed." + fi +} + +test_file_mode() { + echo "Testing futex-contention.py..." + # Some systems might not have syscalls:sys_enter_futex + if ! perf list | grep -q syscalls:sys_enter_futex; then + echo "Skipping file mode test, syscalls:sys_enter_futex not found" + return + fi + + # Generate some futex events + if ! perf record -e syscalls:sys_enter_futex,syscalls:sys_exit_futex -a -o "${temp_data}" \ + -- sleep 0.5 2>/dev/null; then + echo "Skipping file mode test (record failed)" + return + fi + + if ! "$PYTHON" "$script_path" -i "${temp_data}" > "${temp_out}"; then + echo "File mode test failed." + err=1 + else + echo "File mode test passed." + fi +} + +test_synthetic +test_file_mode + +exit $err -- 2.56.0.rc1.315.gc6ed9934b7-goog