[tracing] The CPU profiler should only be enabled for specific modes of tracing

src/profiler/tracing-cpu-profiler.cc

Index: src/profiler/tracing-cpu-profiler.cc
diff --git a/src/profiler/tracing-cpu-profiler.cc b/src/profiler/tracing-cpu-profiler.cc
index 8b3122590500925c312d2a4377d4ede4617d8cb8..49991376048261cf25970d65dc9d3f6a51a84b5a 100644
--- a/src/profiler/tracing-cpu-profiler.cc
+++ b/src/profiler/tracing-cpu-profiler.cc
@@ -8,8 +8,8 @@
 #include "src/tracing/trace-event.h"
 #include "src/v8.h"
 
-#define PROFILER_TRACE_CATEGORY_ENABLED(cat) \
-  (*TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(cat)))
+#define PROFILER_TRACE_CATEGORY_ENABLED(cat, ret) \

[alph, 2017/02/09 18:23:56]

Don't think this macro makes sense now. You can just directly use
TRACE_EVENT_CATEGORY_GROUP_ENABLED in those remaining two places.

[ssid, 2017/02/10 01:47:41]

Done.

+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(cat), ret)
 
 namespace v8 {
 
@@ -25,8 +25,9 @@ namespace internal {
 TracingCpuProfilerImpl::TracingCpuProfilerImpl(Isolate* isolate)
     : isolate_(isolate), profiling_enabled_(false) {
   // Make sure tracing system notices profiler categories.
-  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler");
-  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires");
+  TRACE_EVENT_WARMUP_CATEGORY(TRACE_DISABLED_BY_DEFAULT("v8.cpu_profiler"));
+  TRACE_EVENT_WARMUP_CATEGORY(
+      TRACE_DISABLED_BY_DEFAULT("v8.cpu_profiler.hires"));
   V8::GetCurrentPlatform()->AddTraceStateObserver(this);
 }
 
@@ -36,7 +37,9 @@ TracingCpuProfilerImpl::~TracingCpuProfilerImpl() {
 }
 
 void TracingCpuProfilerImpl::OnTraceEnabled() {
-  if (!PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler")) return;
+  bool enabled;
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler", &enabled);
+  if (!enabled) return;
   profiling_enabled_ = true;
   isolate_->RequestInterrupt(
       [](v8::Isolate*, void* data) {
@@ -59,8 +62,9 @@ void TracingCpuProfilerImpl::OnTraceDisabled() {
 void TracingCpuProfilerImpl::StartProfiling() {
   base::LockGuard<base::Mutex> lock(&mutex_);
   if (!profiling_enabled_ || profiler_) return;
-  int sampling_interval_us =
-      PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires") ? 100 : 1000;
+  bool enabled;
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires", &enabled);
+  int sampling_interval_us = enabled ? 100 : 1000;
   profiler_.reset(new CpuProfiler(isolate_));
   profiler_->set_sampling_interval(
       base::TimeDelta::FromMicroseconds(sampling_interval_us));