Adds code_and_metadata_size statistics when collecting v8 heap statis…

…tics.

To measure the overall size of code along with its metadata, we add
a new category called code_and_metadata_size. This data is collected by
scanning the heap for code/bytecode objects. V8 exposes an explicit API
to obtain this data. It should be used with caution as it could be slow.
It involves scanning the heap to collect this data. This data is collected
only when memory-infra.v8.code_stats is enabled.

BUG=v8:4280
LOG=N

Review-Url: https://codereview.chromium.org/1929523002
Cr-Commit-Position: refs/heads/master@{#397706}

gin/v8_isolate_memory_dump_provider.cc

@@ -44,6 +44,43 @@ bool V8IsolateMemoryDumpProvider::OnMemoryDump(
   return true;
 }
 
+namespace {
+
+// Dump statistics related to code/bytecode when memory-infra.v8.code_stats is
+// enabled.
+void DumpCodeStatistics(
+    base::trace_event::MemoryAllocatorDump* heap_spaces_dump,
+    IsolateHolder* isolate_holder) {
+  // Collecting code statistics is an expensive operation (~10 ms) when
+  // compared to other v8 metrics (< 1 ms). So, dump them only when
+  // memory-infra.v8.code_stats is enabled.
+  // TODO(primiano): This information should be plumbed through TraceConfig.
+  // See crbug.com/616441.
+  bool dump_code_stats = false;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(
+      TRACE_DISABLED_BY_DEFAULT("memory-infra.v8.code_stats"),
+      &dump_code_stats);
+  if (!dump_code_stats)
+    return;
+
+  v8::HeapCodeStatistics code_statistics;
+  if (!isolate_holder->isolate()->GetHeapCodeAndMetadataStatistics(
+          &code_statistics)) {
+    return;
+  }
+
+  heap_spaces_dump->AddScalar(
+      "code_and_metadata_size",
+      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+      code_statistics.code_and_metadata_size());
+  heap_spaces_dump->AddScalar(
+      "bytecode_and_metadata_size",
+      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+      code_statistics.bytecode_and_metadata_size());
+}
+
+}  // namespace anonymous
+
 void V8IsolateMemoryDumpProvider::DumpHeapStatistics(
     const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* process_memory_dump) {
@@ -131,6 +168,11 @@ void V8IsolateMemoryDumpProvider::DumpHeapStatistics(
                                           system_allocator_name);
   }
 
+  // Add an empty row for the heap_spaces. This is to keep the shape of the
+  // dump stable, whether code stats are enabled or not.
+  auto heap_spaces_dump =
+      process_memory_dump->CreateAllocatorDump(space_name_prefix);
+
   // Dump object statistics only for detailed dumps.
   if (args.level_of_detail !=
       base::trace_event::MemoryDumpLevelOfDetail::DETAILED) {
@@ -179,8 +221,11 @@ void V8IsolateMemoryDumpProvider::DumpHeapStatistics(
   if (did_dump_object_stats) {
     process_memory_dump->AddOwnershipEdge(
         process_memory_dump->CreateAllocatorDump(object_name_prefix)->guid(),
-        process_memory_dump->CreateAllocatorDump(space_name_prefix)->guid());
+        heap_spaces_dump->guid());
   }
+
+  // Dump statistics related to code and bytecode if requested.
+  DumpCodeStatistics(heap_spaces_dump, isolate_holder_);
 }
 
 }  // namespace gin