Dev compiler debugger related tweaks.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/profile.dart

+// Copyright (c) 2017, 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.
+
+/// This file supports profiling dynamic calls.
+part of dart._runtime;
+
+class _MethodStats {
+  final String typeName;
+  final String frame;
+  double count;
+
+  _MethodStats(this.typeName, this.frame) {
+    count = 0.0;
+  }
+}
+
+class _CallMethodRecord {
+  var jsError;
+  var type;
+
+  _CallMethodRecord(this.jsError, this.type);
+}
+
+/// Size for the random sample of dynamic calls.
+int _callRecordSampleSize = 5000;
+
+/// If the number of dynamic calls exceeds [_callRecordSampleSize] this list
+/// will represent a random sample of the dynamic calls made.
+List<_CallMethodRecord> _callMethodRecords = new List();
+
+/// If the number of dynamic calls exceeds [_callRecordSampleSize] this value
+/// will be greater than [_callMethodRecords.length].
+int _totalCallRecords = 0;
+
+/// Minimum number of samples to consider a profile entry relevant.
+/// This could be set a lot higher. We set this value so users are not
+/// confused into thinking that a dynamic call that occurred once but was
+/// randomly included in the sample is relevant.
+num _minCount = 2;
+
+/// Cache mapping from raw stack frames to source mapped stack frames to
+/// speedup lookup of source map frames when running the profiler.
+/// The number of source map entries looked up makes caching more important
+/// in this case than for typical source map use cases.
+Map<String, String> _frameMappingCache = new Map();
+
+List<List<Object>> getDynamicStats() {
+  // Process the accumulated method stats. This may be quite slow as processing
+  // stack traces is expensive. If there are performance blockers, we should
+  // switch to a sampling approach that caps the number of _callMethodRecords
+  // and uses random sampling to decide whether to add each additional record
+  // to the sample. Main change required is that we need to still show the total
+  // raw number of dynamic calls so that the magnitude of the dynamic call
+  // performance hit is clear to users.
+
+  Map<String, _MethodStats> callMethodStats = new Map();
+  if (_callMethodRecords.length > 0) {
+    // Ratio between total record count and sampled records count.
+    var recordRatio = _totalCallRecords / _callMethodRecords.length;
+    for (var record in _callMethodRecords) {
+      var stackStr = JS('String', '#.stack', record.jsError);
+      var frames = stackStr.split('\n');
+      var src = '';
+      // Skip first two lines as the first couple frames are from the dart
+      // runtime.
+      for (int i = 2; i < frames.length; ++i) {
+        var frame = frames[i];
+        var mappedFrame = _frameMappingCache.putIfAbsent(frame, () {
+          return stackTraceMapper('\n${frame}');
+        });
+        if (!mappedFrame.contains('dart:_runtime/operations.dart') &&
+            !mappedFrame.contains('dart:_runtime/profile.dart')) {
+          src = mappedFrame;
+          break;
+        }
+      }
+
+      var actualTypeName = typeName(record.type);
+      callMethodStats
+          .putIfAbsent("$actualTypeName <$src>",
+              () => new _MethodStats(actualTypeName, src))
+          .count += recordRatio;
+    }
+
+    // filter out all calls that did not occur at least _minCount times in the
+    // random sample if we are dealing with a random sample instead of a
+    // complete profile.
+    if (_totalCallRecords != _callMethodRecords.length) {
+      for (var k in callMethodStats.keys.toList()) {
+        var stats = callMethodStats[k];
+        var threshold = _minCount * recordRatio;
+        if (stats.count + 0.001 < threshold) {
+          callMethodStats.remove(k);
+        }
+      }
+    }
+  }
+  _callMethodRecords.clear();
+  _totalCallRecords = 0;
+  var keys = callMethodStats.keys.toList();
+
+  keys.sort(
+      (a, b) => callMethodStats[b].count.compareTo(callMethodStats[a].count));
+  List<List<Object>> ret = [];
+  for (var key in keys) {
+    var stats = callMethodStats[key];
+    ret.add([stats.typeName, stats.frame, stats.count.round()]);
+  }
+  return ret;
+}
+
+clearDynamicStats() {
+  _callMethodRecords.clear();
+}
+
+bool trackProfile = JS('bool', 'dart.global.trackDdcProfile');
+
+_trackCall(obj) {
+  if (JS('bool', '!#', trackProfile)) return;
+  int index = -1;
+  _totalCallRecords++;
+  if (_callMethodRecords.length == _callRecordSampleSize) {
+    // Ensure that each sample has an equal
+    // _callRecordSampleSize / _totalCallRecords chance of inclusion
+    // by choosing to include the new record in the sample the with the
+    // appropriate probability randomly evicting one of the existing records.
+    // Unfortunately we can't use the excellent Random.nextInt method defined
+    // by Dart from within this library.
+    index = JS('int', 'Math.floor(Math.random() * #)', _totalCallRecords);
+    if (index >= _callMethodRecords.length) return; // don't sample
+  }
+  var record =
+      new _CallMethodRecord(JS('', 'new Error()'), getReifiedType(obj));
+  if (index == -1) {
+    _callMethodRecords.add(record);
+  } else {
+    _callMethodRecords[index] = record;
+  }
+}