[Tracing] Fix runtime call stats tracing for GC.

src/counters.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COUNTERS_H_
 #define V8_COUNTERS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/base/platform/elapsed-timer.h"
@@ skipping 792 matching lines @@
   std::unique_ptr<char[]> buffer_c_str_;
   size_t len_ = 0;
   // Counter to track recursive time events.
   RuntimeCallTimer* current_timer_ = NULL;
   // Used to track nested tracing scopes.
   bool in_use_;
 };
 
 #define TRACE_RUNTIME_CALL_STATS(isolate, counter_name)                  \
   do {                                                                   \
-    if (FLAG_runtime_call_stats) {                                       \
+    if (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED())) { \
+      RuntimeCallStats::CorrectCurrentCounterId(                         \
+          isolate->counters()->tracing_runtime_call_stats(),             \
+          &RuntimeCallStats::counter_name);                              \
+    } else if (FLAG_runtime_call_stats) {                                \
       RuntimeCallStats::CorrectCurrentCounterId(                         \
           isolate->counters()->runtime_call_stats(),                     \
           &RuntimeCallStats::counter_name);                              \
     }                                                                    \
-    if (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED())) { \
-      RuntimeCallStats::CorrectCurrentCounterId(                         \
-          isolate->counters()->tracing_runtime_call_stats(),             \
-          &RuntimeCallStats::counter_name);                              \
-    }                                                                    \
   } while (false)
 
 #define TRACE_HANDLER_STATS(isolate, counter_name) \
   TRACE_RUNTIME_CALL_STATS(isolate, Handler_##counter_name)
 
 #define HISTOGRAM_RANGE_LIST(HR)                                              \
   /* Generic range histograms */                                              \
   HR(detached_context_age_in_gc, V8.DetachedContextAgeInGC, 0, 20, 21)        \
   HR(gc_idle_time_allotted_in_ms, V8.GCIdleTimeAllottedInMS, 0, 10000, 101)   \
   HR(gc_idle_time_limit_overshot, V8.GCIdleTimeLimit.Overshot, 0, 10000, 101) \
@@ skipping 407 matching lines @@
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Counters);
 };
 
 // A RuntimeCallTimerScopes wraps around a RuntimeCallTimer to measure the
 // the time of C++ scope.
 class RuntimeCallTimerScope {
  public:
   inline RuntimeCallTimerScope(Isolate* isolate,
                                RuntimeCallStats::CounterId counter_id) {
-    if (V8_UNLIKELY(FLAG_runtime_call_stats)) {
+    if (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED())) {
+      isolate_ = isolate;
+      is_tracing_ = true;
+      RuntimeCallStats::Enter(
+          isolate_->counters()->tracing_runtime_call_stats(), &timer_,
+          counter_id);
+    } else if (V8_UNLIKELY(FLAG_runtime_call_stats)) {
       isolate_ = isolate;
       RuntimeCallStats::Enter(isolate_->counters()->runtime_call_stats(),
                               &timer_, counter_id);
     }
-    if (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED())) {
-      isolate_for_tracing_ = isolate;
-      RuntimeCallStats::Enter(
-          isolate_for_tracing_->counters()->tracing_runtime_call_stats(),
-          &trace_event_timer_, counter_id);
-    }
   }
   // This constructor is here just to avoid calling GetIsolate() when the
   // stats are disabled and the isolate is not directly available.
   inline RuntimeCallTimerScope(HeapObject* heap_object,
                                RuntimeCallStats::CounterId counter_id);

[Camillo Bruni, 2016/09/07 02:00:29]

nit: could you declare both constructors in the same file.
secondary nit: could you use a delegating constructor for the HeapObject
version, this would save some code duplication.

[lpy, 2016/09/07 16:48:09]

Done.

 
   inline ~RuntimeCallTimerScope() {
-    if (V8_UNLIKELY(FLAG_runtime_call_stats)) {
-      RuntimeCallStats::Leave(isolate_->counters()->runtime_call_stats(),
-                              &timer_);
-    }
-    if (V8_UNLIKELY(isolate_for_tracing_ != nullptr)) {
-      RuntimeCallStats::Leave(
-          isolate_for_tracing_->counters()->tracing_runtime_call_stats(),
-          &trace_event_timer_);
-      isolate_for_tracing_ = nullptr;
+    if (V8_UNLIKELY(isolate_ != nullptr)) {
+      if (is_tracing_) {
+        RuntimeCallStats::Leave(
+            isolate_->counters()->tracing_runtime_call_stats(), &timer_);
+      } else {
+        RuntimeCallStats::Leave(isolate_->counters()->runtime_call_stats(),
+                                &timer_);
+      }
     }
   }
 
  private:
-  Isolate* isolate_;
-  // TODO(lpy): --runtime-call-stats and tracing should be mutually exclusive
-  // with tracing taking precendence. We need to add checks, and use a single
-  // isolate reference and a timer for both.
-  Isolate* isolate_for_tracing_ = nullptr;
+  Isolate* isolate_ = nullptr;
+  bool is_tracing_ = false;
   RuntimeCallTimer timer_;
-  RuntimeCallTimer trace_event_timer_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_