Dev compiler debugger related tweaks.

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

 // Copyright (c) 2015, 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 library defines runtime operations on objects used by the code
 /// generator.
 part of dart._runtime;
 
 class InvocationImpl extends Invocation {
   final Symbol memberName;
@@ skipping 346 matching lines @@
     (resolvedField) => _callMethod(obj, resolvedField, typeArgs, args, method));
 
 dsendRepl(obj, method, @rest args) => _callMethodRepl(obj, method, null, args);
 
 dgsendRepl(obj, typeArgs, method, @rest args) =>
     _callMethodRepl(obj, method, typeArgs, args);
 
 class _MethodStats {
   final String typeName;
   final String frame;
-  int count;
+  double count;

[Jacob, 2017/04/12 18:24:42]

Switch to a a random sampling profiler to make profiling less horribly slow.
Users should only worry about common dynamic calls rather than trying to
eliminate all dynamism from their programs.

 
   _MethodStats(this.typeName, this.frame) {
-    count = 0;
+    count = 0.0;
   }
 }
 
+class _CallMethodRecord {
+  var jsError;
+  var type;
+
+  _CallMethodRecord(this.jsError, this.type);
+}
+
 Map<String, _MethodStats> _callMethodStats = new Map();
 
+/// 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() {
   List<List<Object>> ret = [];
+  // 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.
 
+  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);
+      // Truncate the stacktrace as we are only interested in the top 3-4 frames.
+      var frames = stackStr.split('\n');
+      var src = '';
+      for (int i = 2; i < frames.length; ++i) {
+        var frame = frames[i];
+        var mappedFrame = _frameMappingCache.putIfAbsent(frame, () {
+          return stackTraceMapper('\n${frame}');
+        });
+        if (!mappedFrame.contains(
+            'dart:_internal/js_runtime/lib/ddc_runtime/operations.dart')) {
+          src = mappedFrame;
+          break;
+        }
+      }
+
+      var actualTypeName = typeName(record.type);
+      _callMethodStats
+          .putIfAbsent("$actualTypeName <$src>",
+              () => new _MethodStats(actualTypeName, src))
+          .count += recordRatio;
+    }
+
+    for (var k in _callMethodStats.keys.toList()) {
+      var stats = _callMethodStats[k];
+      // filter out all calls that did not occur at least _minCount times in the
+      // random sample.
+      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));
   for (var key in keys) {
     var stats = _callMethodStats[key];
-    ret.add([stats.typeName, stats.frame, stats.count]);
+    ret.add([stats.typeName, stats.frame, stats.count.round()]);
   }
 
   return ret;
 }
 
 clearDynamicStats() {
   _callMethodStats.clear();
+  _callMethodRecords.clear();
 }
 
 bool trackProfile = JS('bool', 'dart.global.trackDdcProfile');
 
 _trackCall(obj) {
   if (JS('bool', '!#', trackProfile)) return;
-
-  var actual = getReifiedType(obj);
-  String stackStr = JS('String', "new Error().stack");
-  var stack = stackStr.split('\n    at ');
-  var src = '';
-  for (int i = 2; i < stack.length; ++i) {
-    var frame = stack[i];
-    if (!frame.contains('dart_sdk.js')) {
-      src = frame;
-      break;
-    }
+  int index = -1;
+  _totalCallRecords++;
+  if (_callMethodRecords.length == _callRecordSampleSize) {
+    // 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 actualTypeName = typeName(actual);
-  _callMethodStats
-      .putIfAbsent(
-          "$actualTypeName <$src>", () => new _MethodStats(actualTypeName, src))
-      .count++;
+  var record =
+      new _CallMethodRecord(JS('', 'new Error()'), getReifiedType(obj));
+  if (index == -1) {
+    _callMethodRecords.add(record);
+  } else {
+    _callMethodRecords[index] = record;
+  }
 }
 
 /// Shared code for dsend, dindex, and dsetindex.
 _callMethod(obj, name, typeArgs, args, displayName) {
   var symbol = _canonicalMember(obj, name);
   if (symbol == null) {
     return noSuchMethod(
         obj, new InvocationImpl(displayName, args, isMethod: true));
   }
   var f = obj != null ? JS('', '#[#]', obj, symbol) : null;
@@ skipping 556 matching lines @@
     name = '+' + name;
   }
   return name;
 }
 
 /// Emulates the implicit "loadLibrary" function provided by a deferred library.
 ///
 /// Libraries are not actually deferred in DDC, so this just returns a future
 /// that completes immediately.
 Future loadLibrary() => new Future.value();