Chrome tracing for system-wide performance stats.

base/debug/trace_event_system_stats_monitor.cc

+// 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 "base/debug/trace_event_system_stats_monitor.h"
+
+#include "base/debug/leak_annotations.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/message_loop/message_loop.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/threading/thread_local_storage.h"
+
+namespace base {
+namespace debug {
+
+namespace {
+
+/////////////////////////////////////////////////////////////////////////////
+// Holds profiled system stats until the tracing system needs to serialize it.
+class SystemStatsHolder : public base::debug::ConvertableToTraceFormat {
+ public:
+  SystemStatsHolder() { }
+  virtual ~SystemStatsHolder() { }
+
+  // Fills system_metrics_ with profiled system memory and disk stats.
+  // Uses the previous stats to compute rates if this is not the first profile.
+  void GetSystemProfilingStats();
+
+  // base::debug::ConvertableToTraceFormat overrides:
+  virtual void AppendAsTraceFormat(std::string* out) const OVERRIDE {
+    AppendSystemProfileAsTraceFormat(system_stats_, out);
+  }
+
+ private:
+  SystemMetrics system_stats_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemStatsHolder);
+};
+
+void SystemStatsHolder::GetSystemProfilingStats() {
+  system_stats_ = SystemMetrics::Sample();

[darin (slow to review), 2013/09/12 20:51:15]

nit: insert new line before close of namespace.

[jwmak, 2013/09/13 20:57:11]

Done.

+}
+}  // namespace
+
+//////////////////////////////////////////////////////////////////////////////
+
+TraceEventSystemStatsMonitor::TraceEventSystemStatsMonitor(
+    scoped_refptr<MessageLoopProxy> message_loop_proxy)
+    : message_loop_proxy_(message_loop_proxy),
+      weak_factory_(this) {
+  // Force the "system_stats" category to show up in the trace viewer.
+  TraceLog::GetCategoryGroupEnabled(TRACE_DISABLED_BY_DEFAULT("system_stats"));
+
+  // Allow this to be instantiated on unsupported platforms, but don't run.
+  TraceLog::GetInstance()->AddEnabledStateObserver(this);
+}
+
+TraceEventSystemStatsMonitor::~TraceEventSystemStatsMonitor() {
+  if (dump_timer_.IsRunning())
+    StopProfiling();
+  TraceLog::GetInstance()->RemoveEnabledStateObserver(this);
+}
+
+void TraceEventSystemStatsMonitor::OnTraceLogEnabled() {
+  // Check to see if system tracing is enabled.
+  bool enabled;
+
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(
+                                     "system_stats"), &enabled);
+  if (!enabled)
+    return;
+  message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(&TraceEventSystemStatsMonitor::StartProfiling,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void TraceEventSystemStatsMonitor::OnTraceLogDisabled() {
+  message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(&TraceEventSystemStatsMonitor::StopProfiling,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void TraceEventSystemStatsMonitor::StartProfiling() {
+  // Watch for the tracing framework sending enabling more than once.
+  if (dump_timer_.IsRunning())
+    return;
+
+  dump_timer_.Start(FROM_HERE,
+                    TimeDelta::FromMilliseconds(TraceEventSystemStatsMonitor::
+                                                kSamplingIntervalMilliseconds),
+                    base::Bind(&TraceEventSystemStatsMonitor::
+                               DumpSystemStats,
+                               weak_factory_.GetWeakPtr()));
+}
+
+// If system tracing is enabled, dumps a profile to the tracing system.
+void TraceEventSystemStatsMonitor::DumpSystemStats() {
+  scoped_ptr<SystemStatsHolder> dump_holder(new SystemStatsHolder());
+  dump_holder->GetSystemProfilingStats();
+
+  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
+      TRACE_DISABLED_BY_DEFAULT("system_stats"),
+      "base::TraceEventSystemStatsMonitor::SystemStats",
+      this,
+      dump_holder.PassAs<base::debug::ConvertableToTraceFormat>());
+}
+
+void TraceEventSystemStatsMonitor::StopProfiling() {
+  dump_timer_.Stop();
+}
+
+bool TraceEventSystemStatsMonitor::IsTimerRunningForTest() const {
+  return dump_timer_.IsRunning();
+}
+
+void AppendSystemProfileAsTraceFormat(const SystemMetrics& system_metrics,
+                                      std::string* output) {
+  std::string tmp;
+  base::JSONWriter::Write(system_metrics.ToValue().get(), &tmp);
+  *output += tmp;
+}
+
+}  // namespace debug
+}  // namespace base