[tracing] Separate tracing implementations and add perfetto tests

Previously both tracing implementations would be run side-by-side when
perfetto was enabled with the V8_USE_PERFETTO build flag. This CL
makes them run separately.

Both implementations now use the trace file provided by the user in D8
or the default v8_trace.json.

Add tests for perfetto events (which must be tested differently
due to the proto output format).

Drive-by fix: Fix pass-by non-const ref in GetJSONStrings.

Remove the TraceEvent struct for testing; we can just store a copy of
the protobuf directly.

Bug: v8:8339
Change-Id: Id50003e0f96e44b99a63a26693da6bdaca989504
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1702619Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62810}

src/d8/d8.cc

@@ -3323,28 +3323,25 @@ int Shell::Main(int argc, char* argv[]) {
 
   std::unique_ptr<platform::tracing::TracingController> tracing;
   std::ofstream trace_file;
-#ifdef V8_USE_PERFETTO
-  std::ofstream perfetto_trace_file;
-#endif  // V8_USE_PERFETTO
   if (options.trace_enabled && !i::FLAG_verify_predictable) {
     tracing = base::make_unique<platform::tracing::TracingController>();
-
     trace_file.open(options.trace_path ? options.trace_path : "v8_trace.json");
     DCHECK(trace_file.good());
-    platform::tracing::TraceBuffer* trace_buffer =
-        platform::tracing::TraceBuffer::CreateTraceBufferRingBuffer(
-            platform::tracing::TraceBuffer::kRingBufferChunks,
-            platform::tracing::TraceWriter::CreateJSONTraceWriter(trace_file));
-    tracing->Initialize(trace_buffer);
 
 #ifdef V8_USE_PERFETTO
+    // Set up the in-process backend that the tracing controller will connect
+    // to.
     perfetto::TracingInitArgs init_args;
     init_args.backends = perfetto::BackendType::kInProcessBackend;
     perfetto::Tracing::Initialize(init_args);
 
-    perfetto_trace_file.open("v8_perfetto_trace.json");
-    DCHECK(trace_file.good());
-    tracing->InitializeForPerfetto(&perfetto_trace_file);
+    tracing->InitializeForPerfetto(&trace_file);
+#else
+    platform::tracing::TraceBuffer* trace_buffer =
+        platform::tracing::TraceBuffer::CreateTraceBufferRingBuffer(
+            platform::tracing::TraceBuffer::kRingBufferChunks,
+            platform::tracing::TraceWriter::CreateJSONTraceWriter(trace_file));
+    tracing->Initialize(trace_buffer);
 #endif  // V8_USE_PERFETTO
   }
 

src/libplatform/tracing/tracing-controller.cc

@@ -92,6 +92,7 @@ void TracingController::InitializeForPerfetto(std::ostream* output_stream) {
   output_stream_ = output_stream;
   DCHECK_NOT_NULL(output_stream);
   DCHECK(output_stream->good());
+  mutex_.reset(new base::Mutex());
 }
 
 void TracingController::SetTraceEventListenerForTesting(
@@ -146,7 +147,9 @@ void AddArgsToTraceProto(
       case TRACE_VALUE_TYPE_POINTER:
         arg->set_pointer_value(arg_value.as_uint);
         break;
-      // TODO(petermarshall): Treat copy strings specially.
+      // There is no difference between copy strings and regular strings for
+      // Perfetto; the set_string_value(const char*) API will copy the string
+      // into the protobuf by default.
       case TRACE_VALUE_TYPE_COPY_STRING:
       case TRACE_VALUE_TYPE_STRING:
         arg->set_string_value(arg_value.as_string);
@@ -216,7 +219,8 @@ uint64_t TracingController::AddTraceEventWithTimestamp(
       AddArgsToTraceProto(trace_event, num_args, arg_names, arg_types,
                           arg_values, arg_convertables);
     });
-#endif  // V8_USE_PERFETTO
+    return 0;
+#else
 
   uint64_t handle = 0;
   if (recording_.load(std::memory_order_acquire)) {
@@ -232,6 +236,7 @@ uint64_t TracingController::AddTraceEventWithTimestamp(
     }
   }
   return handle;
+#endif  // V8_USE_PERFETTO
 }
 
 void TracingController::UpdateTraceEventDuration(
@@ -251,11 +256,12 @@ void TracingController::UpdateTraceEventDuration(
     trace_event->set_process_id(base::OS::GetCurrentProcessId());
     trace_event->set_thread_timestamp(cpu_now_us);
   });
-#endif  // V8_USE_PERFETTO
+#else
 
   TraceObject* trace_object = trace_buffer_->GetEventByHandle(handle);
   if (!trace_object) return;
   trace_object->UpdateDuration(now_us, cpu_now_us);
+#endif  // V8_USE_PERFETTO
 }
 
 const char* TracingController::GetCategoryGroupName(
@@ -317,7 +323,6 @@ void TracingController::StopTracing() {
   if (!recording_.compare_exchange_strong(expected, false)) {
     return;
   }
-  DCHECK(trace_buffer_);
   UpdateCategoryGroupEnabledFlags();
   std::unordered_set<v8::TracingController::TraceStateObserver*> observers_copy;
   {
@@ -339,13 +344,14 @@ void TracingController::StopTracing() {
   if (listener_for_testing_) listener_for_testing_->ParseFromArray(trace);
 
   json_listener_.reset();
-
-#endif  // V8_USE_PERFETTO
+#else
 
   {
     base::MutexGuard lock(mutex_.get());
+    DCHECK(trace_buffer_);
     trace_buffer_->Flush();
   }
+#endif  // V8_USE_PERFETTO
 }
 
 void TracingController::UpdateCategoryGroupEnabledFlag(size_t category_index) {

src/tracing/trace-event.h

@@ -32,7 +32,9 @@ enum CategoryGroupEnabledFlags {
   kEnabledForETWExport_CategoryGroupEnabledFlags = 1 << 3,
 };
 
-// By default, const char* asrgument values are assumed to have long-lived scope
+// TODO(petermarshall): Remove with the old tracing implementation - Perfetto
+// copies const char* arguments by default.
+// By default, const char* argument values are assumed to have long-lived scope
 // and will not be copied. Use this macro to force a const char* to be copied.
 #define TRACE_STR_COPY(str) v8::internal::tracing::TraceStringWithCopy(str)
 

test/cctest/cctest.cc

@@ -306,6 +306,7 @@ int main(int argc, char* argv[]) {
   }
 
 #ifdef V8_USE_PERFETTO
+  // Set up the in-process backend that the tracing controller will connect to.
   perfetto::TracingInitArgs init_args;
   init_args.backends = perfetto::BackendType::kInProcessBackend;
   perfetto::Tracing::Initialize(init_args);