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Thu, 23 Apr 2026 12:44:33 -0700 (PDT) Date: Thu, 23 Apr 2026 12:43:58 -0700 In-Reply-To: <20260423194428.1846255-1-irogers@google.com> Mime-Version: 1.0 References: <20260423161006.1762700-1-irogers@google.com> <20260423194428.1846255-1-irogers@google.com> X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog Message-ID: <20260423194428.1846255-2-irogers@google.com> Subject: [PATCH v4 29/58] perf futex-contention: Port futex-contention to use python module From: Ian Rogers To: acme@kernel.org, adrian.hunter@intel.com, james.clark@linaro.org, leo.yan@linux.dev, namhyung@kernel.org, tmricht@linux.ibm.com Cc: alice.mei.rogers@gmail.com, dapeng1.mi@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, Ian Rogers Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260423_124435_503017_A65651F6 X-CRM114-Status: GOOD ( 16.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Rewrite tools/perf/scripts/python/futex-contention.py to use the python module and various style changes. By avoiding the overheads in the `perf script` execution the performance improves by more than 3.2x as shown in the following (with PYTHON_PATH and PERF_EXEC_PATH set as necessary): ``` $ perf record -e syscalls:sys_*_futex -a sleep 1 ... $ time perf script tools/perf/scripts/python/futex-contention.py Install the python-audit package to get syscall names. For example: # apt-get install python3-audit (Ubuntu) # yum install python3-audit (Fedora) etc. Press control+C to stop and show the summary aaa/4[2435653] lock 7f76b380c878 contended 1 times, 1099 avg ns [max: 1099 ns, min 1099 ns] ... 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 ``` Assisted-by: Gemini:gemini-3.1-pro-preview Signed-off-by: Ian Rogers --- v2: 1. Fixed Module Import Failure: Corrected the type annotations from [int, int] to Tuple[int, int] . The previous code would raise a TypeError at module import time because lists cannot be used as types in dictionary annotations. 2. Prevented Out-Of-Memory Crashes: Replaced the approach of storing every single duration in a list with a LockStats class that maintains running aggregates (count, total time, min, max). This ensures O(1) memory usage per lock/thread pair rather than unbounded memory growth. 3. Support for Custom Input Files: Added a -i / --input command-line argument to support processing arbitrarily named trace files, removing the hardcoded "perf.data" restriction. 4. Robust Process Lookup: Added a check to ensure session is initialized before calling session. process() , preventing potential NoneType attribute errors if events are processed during initialization. --- tools/perf/python/futex-contention.py | 87 +++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100755 tools/perf/python/futex-contention.py diff --git a/tools/perf/python/futex-contention.py b/tools/perf/python/futex-contention.py new file mode 100755 index 000000000000..7c5c3d0ca60a --- /dev/null +++ b/tools/perf/python/futex-contention.py @@ -0,0 +1,87 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0 +"""Measures futex contention.""" + +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_WAKE = 1 +FUTEX_PRIVATE_FLAG = 128 +FUTEX_CLOCK_REALTIME = 256 +FUTEX_CMD_MASK = ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME) + + +def process_event(sample: perf.sample_event) -> None: + """Process a single sample event.""" + def handle_start(tid: int, uaddr: int, op: int, start_time: int) -> None: + if (op & FUTEX_CMD_MASK) != FUTEX_WAIT: + return + if tid not in process_names: + try: + if session: + process = session.process(tid) + if process: + process_names[tid] = process.comm() + except (TypeError, AttributeError): + return + start_times[tid] = (uaddr, start_time) + + def handle_end(tid: int, end_time: int) -> None: + 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) + + event_name = str(sample.evsel) + if event_name == "evsel(syscalls:sys_enter_futex)": + uaddr = getattr(sample, "uaddr", 0) + op = getattr(sample, "op", 0) + handle_start(sample.sample_tid, uaddr, op, sample.sample_time) + elif event_name == "evsel(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() + + session = perf.session(perf.data(args.input), sample=process_event) + session.process_events() + + for ((t, u), stats) in sorted(durations.items()): + avg_ns = stats.avg() + print(f"{process_names.get(t, 'unknown')}[{t}] lock {u:x} contended {stats.count} times, " + f"{avg_ns:.0f} avg ns [max: {stats.max_time} ns, min {stats.min_time} ns]") -- 2.54.0.rc2.533.g4f5dca5207-goog