Switch to tab-separated output, update CHANGELOG and version number

The json output format is only in the most recent versions of perf stat.
Use the separated value output format instead.

Address review comments, ensure perf process is terminated if
failures occur.

CHANGELOG.md

@@ -1,6 +1,10 @@
-## 2.2.3-wip
+## 2.2.3
 
 - Require Dart 3.2.
+- Add `PerfBenchmarkBase` class which runs the 'perf stat' command from
+linux-tools on a benchmark and reports metrics from the hardware
+performance counters and the iteration count, as well as the run time
+measurement reported by `BenchmarkBase`.
 
 ## 2.2.2
 

lib/src/perf_benchmark_base.dart

@@ -2,15 +2,14 @@
 // 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:async';
 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;
@@ -19,37 +18,34 @@ class PerfBenchmarkBase extends BenchmarkBase {
   late final Process perfProcess;
   late final List<String> perfProcessArgs;
 
+  PerfBenchmarkBase(super.name, {super.emitter = const PrintEmitter()});
+
   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);
+    for (final path in [perfControlFifo, perfControlAck]) {
+      final fifoResult = await Process.run('mkfifo', [path]);
+      if (fifoResult.exitCode != 0) {
+        throw ProcessException('mkfifo', [path],
+            'Cannot create fifo: ${fifoResult.stderr}', fifoResult.exitCode);
+      }
     }
   }
 
   Future<void> _startPerfStat() async {
     await _createFifos();
     perfProcessArgs = [
       'stat',
-      '--delay',
-      '-1',
-      '--control',
-      'fifo:$perfControlFifo,$perfControlAck',
-      '-j',
-      '-p',
-      '$pid',
+      '--delay=-1',
+      '--control=fifo:$perfControlFifo,$perfControlAck',
+      '-x\\t',
+      '--pid=$pid',
     ];
     perfProcess = await Process.start('perf', perfProcessArgs);
-    openedFifo = File(perfControlFifo).openSync(mode: FileMode.writeOnly);
+  }
 
+  void _enablePerf() {
+    openedFifo = File(perfControlFifo).openSync(mode: FileMode.writeOnly);
     openedAck = File(perfControlAck).openSync();
     openedFifo.writeStringSync('enable\n');
     _waitForAck();
@@ -61,20 +57,36 @@ class PerfBenchmarkBase extends BenchmarkBase {
     _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.
+    unawaited(perfProcess.stdout.drain());
+    final lines = await perfProcess.stderr
+        .transform(utf8.decoder)
+        .transform(const LineSplitter())
+        .toList();
     final exitCode = await perfProcess.exitCode;
-    if (exitCode != 0 && exitCode != -2) {
+    // Exit code from perf is -SIGINT when terminated with SIGINT.
+    if (exitCode != 0 && exitCode != -ProcessSignal.sigint.signalNumber) {
       throw ProcessException(
-          'perf', perfProcessArgs, (await lines.toList()).join('\n'), exitCode);
+          'perf', perfProcessArgs, lines.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);
+
+    const metrics = {
+      'cycles': 'CpuCycles',
+      'page-faults': 'MajorPageFaults',
+    };
+    for (final line in lines) {
+      if (line.split('\t')
+          case [
+            String counter,
+            _,
+            String event && ('cycles' || 'page-faults'),
+            ...
+          ]) {
+        emitter.emit(name, double.parse(counter) / totalIterations,
+            metric: metrics[event]!);
+      }
+    }
+    emitter.emit('$name.totalIterations', totalIterations.toDouble(),
+        metric: 'Count');
   }
 
   /// Measures the score for the benchmark and returns it.
@@ -87,9 +99,15 @@ class PerfBenchmarkBase extends BenchmarkBase {
         // 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);
+        try {
+          _enablePerf();
+          // Run the benchmark for at least 2000ms.
+          result = measureForImpl(exercise, minimumMeasureDurationMillis);
+          await _stopPerfStat(result.totalIterations);
+        } catch (_) {
+          perfProcess.kill(ProcessSignal.sigkill);
+          rethrow;
+        }
       } finally {
         await fifoDir.delete(recursive: true);
       }
@@ -111,18 +129,4 @@ class PerfBenchmarkBase extends BenchmarkBase {
       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, double.parse(counterString) / iterations,
-            metric: metric);
-      }
-    }
-    emitter.emit('$name.totalIterations', iterations.toDouble(),
-        metric: 'Count');
-  }
 }

pubspec.yaml

@@ -1,5 +1,5 @@
 name: benchmark_harness
-version: 2.2.3-wip
+version: 2.2.3
 description: The official Dart project benchmark harness.
 repository: https://github.com/dart-lang/benchmark_harness