Add support for running perftools to use hardware performance counters when benchmarking.

integration_test/perf_benchmark_test.dart

@@ -0,0 +1,26 @@
+// Copyright 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:benchmark_harness/perf_benchmark_harness.dart';
+import 'package:test/test.dart';
+
+class PerfBenchmark extends PerfBenchmarkBase {
+  PerfBenchmark(super.name);
+  int runCount = 0;
+
+  @override
+  void run() {
+    runCount++;
+    for (final i in List.filled(1000, 7)) {
+      runCount += i - i;
+    }
+  }
+}
+
+void main() {
+  test('run is called', () async {
+    final benchmark = PerfBenchmark('ForLoop');
+    await benchmark.reportPerf();
+  });
+}

lib/benchmark_harness.dart

@@ -3,5 +3,5 @@
 // BSD-style license that can be found in the LICENSE file.
 
 export 'src/async_benchmark_base.dart';
-export 'src/benchmark_base.dart';
+export 'src/benchmark_base.dart' show BenchmarkBase;
 export 'src/score_emitter.dart';

lib/perf_benchmark_harness.dart

@@ -0,0 +1,7 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+export 'src/perf_benchmark_base_stub.dart'
+    if (dart.library.io) 'src/perf_benchmark_base.dart';
+export 'src/score_emitter.dart';

lib/src/benchmark_base.dart

@@ -6,7 +6,7 @@ import 'dart:math' as math;
 
 import 'score_emitter.dart';
 
-const int _minimumMeasureDurationMillis = 2000;
+const int minimumMeasureDurationMillis = 2000;
 
 class BenchmarkBase {
   final String name;
@@ -40,42 +40,19 @@ class BenchmarkBase {
 
   /// Measures the score for this benchmark by executing it enough times
   /// to reach [minimumMillis].
-  static _Measurement _measureForImpl(void Function() f, int minimumMillis) {
-    final minimumMicros = minimumMillis * 1000;
-    // If running a long measurement permit some amount of measurement jitter
-    // to avoid discarding results that are almost good, but not quite there.
-    final allowedJitter =
-        minimumMillis < 1000 ? 0 : (minimumMicros * 0.1).floor();
-    var iter = 2;
-    final watch = Stopwatch()..start();
-    while (true) {
-      watch.reset();
-      for (var i = 0; i < iter; i++) {
-        f();
-      }
-      final elapsed = watch.elapsedMicroseconds;
-      final measurement = _Measurement(elapsed, iter);
-      if (measurement.elapsedMicros >= (minimumMicros - allowedJitter)) {
-        return measurement;
-      }
-
-      iter = measurement.estimateIterationsNeededToReach(
-          minimumMicros: minimumMicros);
-    }
-  }
 
   /// Measures the score for this benchmark by executing it repeatedly until
   /// time minimum has been reached.
   static double measureFor(void Function() f, int minimumMillis) =>
-      _measureForImpl(f, minimumMillis).score;
+      measureForImpl(f, minimumMillis).score;
 
   /// Measures the score for the benchmark and returns it.
   double measure() {
     setup();
     // Warmup for at least 100ms. Discard result.
-    _measureForImpl(warmup, 100);
+    measureForImpl(warmup, 100);
     // Run the benchmark for at least 2000ms.
-    var result = _measureForImpl(exercise, _minimumMeasureDurationMillis);
+    var result = measureForImpl(exercise, minimumMeasureDurationMillis);
     teardown();
     return result.score;
   }
@@ -85,11 +62,40 @@ class BenchmarkBase {
   }
 }
 
-class _Measurement {
+/// Measures the score for this benchmark by executing it enough times
+/// to reach [minimumMillis].
+Measurement measureForImpl(void Function() f, int minimumMillis) {
+  final minimumMicros = minimumMillis * 1000;
+  // If running a long measurement permit some amount of measurement jitter
+  // to avoid discarding results that are almost good, but not quite there.
+  final allowedJitter =
+      minimumMillis < 1000 ? 0 : (minimumMicros * 0.1).floor();
+  var iter = 2;
+  var totalIterations = iter;
+  final watch = Stopwatch()..start();
+  while (true) {
+    watch.reset();
+    for (var i = 0; i < iter; i++) {
+      f();
+    }
+    final elapsed = watch.elapsedMicroseconds;
+    final measurement = Measurement(elapsed, iter, totalIterations);
+    if (measurement.elapsedMicros >= (minimumMicros - allowedJitter)) {
+      return measurement;
+    }
+
+    iter = measurement.estimateIterationsNeededToReach(
+        minimumMicros: minimumMicros);
+    totalIterations += iter;
+  }
+}
+
+class Measurement {
   final int elapsedMicros;
   final int iterations;
+  final int totalIterations;
 
-  _Measurement(this.elapsedMicros, this.iterations);
+  Measurement(this.elapsedMicros, this.iterations, this.totalIterations);
 
   double get score => elapsedMicros / iterations;
 

lib/src/perf_benchmark_base.dart

@@ -0,0 +1,128 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'benchmark_base.dart';
+import 'score_emitter.dart';
+
+class PerfBenchmarkBase extends BenchmarkBase {
+  PerfBenchmarkBase(super.name, {super.emitter = const PrintEmitter()});
+
+  late final Directory fifoDir;
+  late final String perfControlFifo;
+  late final RandomAccessFile openedFifo;
+  late final String perfControlAck;
+  late final RandomAccessFile openedAck;
+  late final Process perfProcess;
+  late final List<String> perfProcessArgs;
+
+  Future<void> _createFifos() async {
+    perfControlFifo = '${fifoDir.path}/perf_control_fifo';
+    perfControlAck = '${fifoDir.path}/perf_control_ack';
+
+    final fifoResult = await Process.run('mkfifo', [perfControlFifo]);
+    if (fifoResult.exitCode != 0) {
+      throw ProcessException('mkfifo', [perfControlFifo],
+          'Cannot create fifo: ${fifoResult.stderr}', fifoResult.exitCode);
+    }
+    final ackResult = await Process.run('mkfifo', [perfControlAck]);
+    if (ackResult.exitCode != 0) {
+      throw ProcessException('mkfifo', [perfControlAck],
+          'Cannot create fifo: ${ackResult.stderr}', ackResult.exitCode);
+    }
+  }
+
+  Future<void> _startPerfStat() async {
+    await _createFifos();
+    perfProcessArgs = [
+      'stat',
+      '--delay',
+      '-1',
+      '--control',
+      'fifo:$perfControlFifo,$perfControlAck',
+      '-j',
+      '-p',
+      '$pid',
+    ];
+    perfProcess = await Process.start('perf', perfProcessArgs);
+
+    openedFifo = File(perfControlFifo).openSync(mode: FileMode.writeOnly);
+
+    openedAck = File(perfControlAck).openSync();
+    openedFifo.writeStringSync('enable\n');
+    _waitForAck();
+  }
+
+  Future<void> _stopPerfStat(int totalIterations) async {
+    openedFifo.writeStringSync('disable\n');
+    openedFifo.closeSync();
+    _waitForAck();
+    openedAck.closeSync();
+    perfProcess.kill(ProcessSignal.sigint);
+    final lines =
+        utf8.decoder.bind(perfProcess.stderr).transform(const LineSplitter());
+    // Exit code from perf is -2 when terminated with SIGINT.
+    final exitCode = await perfProcess.exitCode;
+    if (exitCode != 0 && exitCode != -2) {
+      throw ProcessException(
+          'perf', perfProcessArgs, (await lines.toList()).join('\n'), exitCode);
+    }
+    final events = [
+      await for (final line in lines)
+        if (line.contains('"counter-value"'))
+          jsonDecode(line) as Map<String, dynamic>
+    ];
+    _reportPerfStats(events, totalIterations);
+  }
+
+  /// Measures the score for the benchmark and returns it.
+  Future<double> measurePerf() async {
+    Measurement result;
+    setup();
+    try {
+      fifoDir = await Directory.systemTemp.createTemp('fifo');
+      try {
+        // Warmup for at least 100ms. Discard result.
+        measureForImpl(warmup, 100);
+        await _startPerfStat();
+        // Run the benchmark for at least 2000ms.
+        result = measureForImpl(exercise, minimumMeasureDurationMillis);
+        await _stopPerfStat(result.totalIterations);
+      } finally {
+        await fifoDir.delete(recursive: true);
+      }
+    } finally {
+      teardown();
+    }
+    return result.score;
+  }
+
+  Future<void> reportPerf() async {
+    emitter.emit(name, await measurePerf());
+  }
+
+  void _waitForAck() {
+    // Perf writes 'ack\n\x00' to the acknowledgement fifo.
+    const ackLength = 'ack\n\x00'.length;
+    var ack = <int>[...openedAck.readSync(ackLength)];
+    while (ack.length < ackLength) {
+      ack.addAll(openedAck.readSync(ackLength - ack.length));
+    }
+  }
+
+  void _reportPerfStats(List<Map<String, dynamic>> events, int iterations) {
+    for (final {'event': String event, 'counter-value': String counterString}
+        in events) {
+      final metric =
+          {'cycles:u': 'CpuCycles', 'page-faults:u': 'MajorPageFaults'}[event];
+      if (metric != null) {
+        emitter.emit(
+            '$name($metric)', double.parse(counterString) / iterations);
+      }
+    }
+    emitter.emit('$name.totalIterations', iterations.toDouble());
+  }
+}

lib/src/perf_benchmark_base_stub.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'benchmark_base.dart';
+import 'score_emitter.dart';
+
+class PerfBenchmarkBase extends BenchmarkBase {
+  PerfBenchmarkBase(super.name, {super.emitter = const PrintEmitter()});
+
+  Future<double> measurePerf() async {
+    return super.measure();
+  }
+
+  Future<void> reportPerf() async {
+    super.report();
+  }
+}