From 32c3006fd03172d190d70431e65e7b3003f29aeb Mon Sep 17 00:00:00 2001
From: Ali Ijaz Sheikh <ofrobots@google.com>
Date: Wed, 16 May 2018 15:22:56 -0700
Subject: [PATCH] src: trace_events: background thread events

V8 uses a thread pool provided by the host to schedule background tasks
for concurrent GC and compiation. Emit trace events to identify the
background threads. Ensure that the tracing infrastructure is started
before the thread pool is initialized.

PR-URL: https://github.com/nodejs/node/pull/20823
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 src/node.cc                                 | 10 ++++------
 src/node_platform.cc                        |  6 ++++--
 test/cctest/node_test_fixture.h             |  6 +++---
 test/parallel/test-trace-events-metadata.js |  3 +++
 4 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/node.cc b/src/node.cc
index 1edb87bf84f0ba..3f0fe28e98b1b8 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -288,11 +288,11 @@ static struct {
 #if NODE_USE_V8_PLATFORM
   void Initialize(int thread_pool_size) {
     tracing_agent_.reset(new tracing::Agent(trace_file_pattern));
-    platform_ = new NodePlatform(thread_pool_size,
-        tracing_agent_->GetTracingController());
+    auto controller = tracing_agent_->GetTracingController();
+    tracing::TraceEventHelper::SetTracingController(controller);
+    StartTracingAgent();
+    platform_ = new NodePlatform(thread_pool_size, controller);
     V8::InitializePlatform(platform_);
-    tracing::TraceEventHelper::SetTracingController(
-        tracing_agent_->GetTracingController());
   }
 
   void Dispose() {
@@ -4420,8 +4420,6 @@ int Start(int argc, char** argv) {
 #endif  // HAVE_OPENSSL
 
   v8_platform.Initialize(v8_thread_pool_size);
-  // Enable tracing when argv has --trace-events-enabled.
-  v8_platform.StartTracingAgent();
   V8::Initialize();
   performance::performance_v8_start = PERFORMANCE_NOW();
   v8_initialized = true;
diff --git a/src/node_platform.cc b/src/node_platform.cc
index b8f1344727cfd6..2885c72ed71213 100644
--- a/src/node_platform.cc
+++ b/src/node_platform.cc
@@ -16,8 +16,10 @@ using v8::Platform;
 using v8::Task;
 using v8::TracingController;
 
-static void BackgroundRunner(void* data) {
-  TaskQueue<Task>* background_tasks = static_cast<TaskQueue<Task>*>(data);
+static void BackgroundRunner(void *data) {
+  TRACE_EVENT_METADATA1("__metadata", "thread_name", "name",
+                        "BackgroundTaskRunner");
+  TaskQueue<Task> *background_tasks = static_cast<TaskQueue<Task> *>(data);
   while (std::unique_ptr<Task> task = background_tasks->BlockingPop()) {
     task->Run();
     background_tasks->NotifyOfCompletion();
diff --git a/test/cctest/node_test_fixture.h b/test/cctest/node_test_fixture.h
index e0740a47096460..f43cb56cd3a5b5 100644
--- a/test/cctest/node_test_fixture.h
+++ b/test/cctest/node_test_fixture.h
@@ -64,12 +64,12 @@ class NodeTestFixture : public ::testing::Test {
   v8::Isolate* isolate_;
 
   static void SetUpTestCase() {
-    platform.reset(new node::NodePlatform(4, nullptr));
     tracing_controller.reset(new v8::TracingController());
-    allocator.reset(v8::ArrayBuffer::Allocator::NewDefaultAllocator());
-    params.array_buffer_allocator = allocator.get();
     node::tracing::TraceEventHelper::SetTracingController(
         tracing_controller.get());
+    platform.reset(new node::NodePlatform(4, nullptr));
+    allocator.reset(v8::ArrayBuffer::Allocator::NewDefaultAllocator());
+    params.array_buffer_allocator = allocator.get();
     CHECK_EQ(0, uv_loop_init(&current_loop));
     v8::V8::InitializePlatform(platform.get());
     v8::V8::Initialize();
diff --git a/test/parallel/test-trace-events-metadata.js b/test/parallel/test-trace-events-metadata.js
index f8fcdcfe5bb788..eccec1ecf0f1a2 100644
--- a/test/parallel/test-trace-events-metadata.js
+++ b/test/parallel/test-trace-events-metadata.js
@@ -22,5 +22,8 @@ proc.once('exit', common.mustCall(() => {
     assert(traces.some((trace) =>
       trace.cat === '__metadata' && trace.name === 'thread_name' &&
         trace.args.name === 'JavaScriptMainThread'));
+    assert(traces.some((trace) =>
+      trace.cat === '__metadata' && trace.name === 'thread_name' &&
+        trace.args.name === 'BackgroundTaskRunner'));
   }));
 }));