Add V8 heap statistics in a time-line manner in tracing.

content/renderer/v8_heap_statistics_monitor.cc

Index: content/renderer/v8_heap_statistics_monitor.cc
diff --git a/content/renderer/v8_heap_statistics_monitor.cc b/content/renderer/v8_heap_statistics_monitor.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8395b3e71221a800eeccd567ab73e0da9d39d682
--- /dev/null
+++ b/content/renderer/v8_heap_statistics_monitor.cc
@@ -0,0 +1,99 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/renderer/v8_heap_statistics_monitor.h"
+
+#include "base/debug/trace_event.h"
+#include "base/json/json_writer.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/single_thread_task_runner.h"
+
+namespace content {
+
+V8HeapStatisticsMonitor::V8HeapStatisticsMonitor(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
+    : dump_pending_(false),
+      task_runner_(task_runner),
+      weak_factory_(this) {
+  // Force the "v8_heap_statistics" category to show up in the trace viewer.
+  base::debug::TraceLog::GetCategoryGroupEnabled(
+      TRACE_DISABLED_BY_DEFAULT("v8_heap_statistics"));
+
+  // Allow this to be instantiated on unsupported platforms, but don't run.
+  base::debug::TraceLog::GetInstance()->AddEnabledStateObserver(this);
+}
+
+V8HeapStatisticsMonitor::~V8HeapStatisticsMonitor() {
+  if (dump_timer_.IsRunning())
+    StopProfiling();
+  base::debug::TraceLog::GetInstance()->RemoveEnabledStateObserver(this);
+}
+
+bool V8HeapStatisticsMonitor::IsMonitoring() const {
+  return dump_timer_.IsRunning();
+}
+
+void V8HeapStatisticsMonitor::OnTraceLogEnabled() {
+  // Check to see if system tracing is enabled.
+  bool enabled;
+
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(
+                                     "v8_heap_statistics"), &enabled);
+  if (!enabled)
+    return;
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&V8HeapStatisticsMonitor::StartProfiling,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void V8HeapStatisticsMonitor::OnTraceLogDisabled() {
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&V8HeapStatisticsMonitor::StopProfiling,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void V8HeapStatisticsMonitor::StartProfiling() {
+  // Watch for the tracing framework sending enabling more than once.
+  if (dump_timer_.IsRunning())
+    return;
+
+  dump_timer_.Start(FROM_HERE,
+                    base::TimeDelta::FromMilliseconds(2000),
+                    base::Bind(&V8HeapStatisticsMonitor::
+                               BeginDumpingHeapStats,
+                               weak_factory_.GetWeakPtr()));
+}
+
+// If system tracing is enabled, dumps a profile to the tracing system.
+void V8HeapStatisticsMonitor::BeginDumpingHeapStats() {
+  if (dump_pending_)
+    return;
+  dump_pending_ = V8HeapStatisticsCollector::Instance()->InitiateCollection(
+      base::Bind(&V8HeapStatisticsMonitor::FinalizeDumpOfHeapStats,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void V8HeapStatisticsMonitor::FinalizeDumpOfHeapStats(
+    const V8HeapStatisticsCollector::Statistics& stats) {
+  dump_pending_ = false;
+  // Keep trace buffer size down by only dumping changes.
+  if (stats.used_bytes == last_dumped_stats_.used_bytes &&
+      stats.total_bytes == last_dumped_stats_.total_bytes)
+    return;
+  last_dumped_stats_ = stats;
+  TRACE_COUNTER2(
+      TRACE_DISABLED_BY_DEFAULT("v8_heap_statistics"), "v8::Heap",
+      "used_bytes", stats.used_bytes,
+      "free_bytes", stats.total_bytes - stats.used_bytes);
+}
+
+void V8HeapStatisticsMonitor::StopProfiling() {
+  dump_timer_.Stop();
+}
+
+}  // namespace content