Define an endpoint on HostTarget to capture frame timings (facebook#54672)

Summary:
Pull Request resolved: facebook#54672

# Changelog: [Internal]

Introduces an endpoint on `HostTarget` for capturing frame timings. This exposes a public API to Host, which could be called during active tracing session.

`Host` could be notified through tracing delegate in `HostTargetDelegate` about tracing state, this has been implemented below as part of this diff stack.

Reviewed By: sbuggay

Differential Revision: D87373807

fbshipit-source-id: 3ffc5f2b803164e4316ff6c3824672c842187ddd

Author: hoxyq

packages/react-native/ReactCommon/jsinspector-modern/HostTarget.h

@@ -20,6 +20,7 @@
 #include <set>
 #include <string>
 
+#include <jsinspector-modern/tracing/FrameTimingSequence.h>
 #include <jsinspector-modern/tracing/HostTracingProfile.h>
 #include <jsinspector-modern/tracing/TraceRecordingState.h>
 #include <jsinspector-modern/tracing/TracingCategory.h>
@@ -325,6 +326,7 @@ class JSINSPECTOR_EXPORT HostTarget : public EnableExecutorFromThis<HostTarget>
    */
   void sendCommand(HostCommand command);
 
+#pragma region Tracing
   /**
    * Creates a new HostTracingAgent.
    * This Agent is not owned by the HostTarget. The Agent will be destroyed at
@@ -363,6 +365,13 @@ class JSINSPECTOR_EXPORT HostTarget : public EnableExecutorFromThis<HostTarget>
    */
   void emitTracingProfileForFirstFuseboxClient(tracing::HostTracingProfile tracingProfile) const;
 
+  /**
+   * An endpoint for the Host to report frame timings that will be recorded if and only if there is currently an active
+   * tracing session.
+   */
+  void recordFrameTimings(tracing::FrameTimingSequence frameTimingSequence);
+#pragma endregion
+
  private:
   /**
    * Constructs a new HostTarget.
@@ -386,13 +395,22 @@ class JSINSPECTOR_EXPORT HostTarget : public EnableExecutorFromThis<HostTarget>
   std::unique_ptr<PerfMonitorUpdateHandler> perfMonitorUpdateHandler_;
   std::unique_ptr<HostRuntimeBinding> perfMetricsBinding_;
 
+#pragma region Tracing
   /**
    * Current pending trace recording, which encapsulates the configuration of
    * the tracing session and the state.
    *
    * Should only be allocated when there is an active tracing session.
    */
   std::unique_ptr<HostTargetTraceRecording> traceRecording_{nullptr};
+  /**
+   * Protects the state inside traceRecording_.
+   *
+   * Calls to tracing subsystem could happen from different threads, depending on the mode (Background or CDP) and
+   * the method: the Host could report frame timings from any arbitrary thread.
+   */
+  std::mutex tracingMutex_;
+#pragma endregion
 
   inline HostTargetDelegate &getDelegate()
   {

packages/react-native/ReactCommon/jsinspector-modern/HostTargetTracing.cpp

@@ -39,10 +39,17 @@ std::shared_ptr<HostTracingAgent> HostTarget::createTracingAgent(
 bool HostTarget::startTracing(
     tracing::Mode tracingMode,
     std::set<tracing::Category> enabledCategories) {
+  std::lock_guard lock(tracingMutex_);
+
   if (traceRecording_ != nullptr) {
     if (traceRecording_->isBackgroundInitiated() &&
         tracingMode == tracing::Mode::CDP) {
-      stopTracing();
+      if (auto tracingDelegate = delegate_.getTracingDelegate()) {
+        tracingDelegate->onTracingStopped();
+      }
+
+      traceRecording_->stop();
+      traceRecording_.reset();
     } else {
       return false;
     }
@@ -67,6 +74,8 @@ bool HostTarget::startTracing(
 }
 
 tracing::HostTracingProfile HostTarget::stopTracing() {
+  std::lock_guard lock(tracingMutex_);
+
   assert(traceRecording_ != nullptr && "No tracing in progress");
 
   if (auto tracingDelegate = delegate_.getTracingDelegate()) {
@@ -79,4 +88,17 @@ tracing::HostTracingProfile HostTarget::stopTracing() {
   return profile;
 }
 
+void HostTarget::recordFrameTimings(
+    tracing::FrameTimingSequence frameTimingSequence) {
+  std::lock_guard lock(tracingMutex_);
+
+  if (traceRecording_) {
+    traceRecording_->recordFrameTimings(frameTimingSequence);
+  } else {
+    assert(
+        false &&
+        "The HostTarget is not being profiled. Did you call recordFrameTimings() from the native Host side when there is no tracing in progress?");
+  }
+}
+
 } // namespace facebook::react::jsinspector_modern

packages/react-native/ReactCommon/jsinspector-modern/tests/TracingTest.cpp

@@ -56,4 +56,24 @@ TEST_F(TracingTest, EnablesSamplingProfilerOnlyCategoryIsSpecified) {
           AtJsonPtr("/cat", "disabled-by-default-v8.cpu_profiler"))));
 }
 
+TEST_F(TracingTest, RecordsFrameTimings) {
+  InSequence s;
+
+  page_->startTracing(tracing::Mode::Background, {tracing::Category::Timeline});
+
+  auto now = HighResTimeStamp::now();
+  auto frameTimingSequence = tracing::FrameTimingSequence(
+      1, // id
+      11, // threadId
+      now,
+      now + HighResDuration::fromNanoseconds(10),
+      now + HighResDuration::fromNanoseconds(50));
+
+  page_->recordFrameTimings(frameTimingSequence);
+
+  auto tracingProfile = page_->stopTracing();
+  EXPECT_EQ(tracingProfile.frameTimings.size(), 1u);
+  EXPECT_EQ(tracingProfile.frameTimings[0].id, frameTimingSequence.id);
+}
+
 } // namespace facebook::react::jsinspector_modern