Introduce RuntimeCallStats::IsEnabled

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 787 matching lines @@
   // Leave a scope for a measured runtime function. This will properly add
   // the time delta to the current_counter and subtract the delta from its
   // parent.
   static void Leave(RuntimeCallStats* stats, RuntimeCallTimer* timer);
 
   // Set counter id for the innermost measurement. It can be used to refine
   // event kind when a runtime entry counter is too generic.
   static void CorrectCurrentCounterId(RuntimeCallStats* stats,
                                       CounterId counter_id);
 
+  // Returns true if RuntimeCallStats are enabled either through a flag or
+  // with tracing.
+  static bool IsEnabled() {

[fmeawad, 2016/10/28 21:54:25]

Wouldn't that add an extra call per check? Why a method and not a macro?

[Camillo Bruni, 2016/10/31 09:57:18]

From what I've seen so far is that clang inlines very aggressively, so I'm
pretty confident that this actually works as intended.

+    return V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED()) ||
+           FLAG_runtime_call_stats;

[Camillo Bruni, 2016/10/31 09:57:58]

nit: put the V8_UNLIKELY around the whole clause, we generally expect the
runtime stats to be disabled

+  }
+
   void Reset();
   void Print(std::ostream& os);
   V8_NOINLINE void Dump(v8::tracing::TracedValue* value);
 
   RuntimeCallStats() {
     Reset();
     in_use_ = false;
   }
 
   RuntimeCallTimer* current_timer() { return current_timer_; }
   bool InUse() { return in_use_; }
 
  private:
   // 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 (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED() || \
-                    FLAG_runtime_call_stats)) {                         \
-      RuntimeCallStats::CorrectCurrentCounterId(                        \
-          isolate->counters()->runtime_call_stats(),                    \
-          &RuntimeCallStats::counter_name);                             \
-    }                                                                   \
+#define TRACE_RUNTIME_CALL_STATS(isolate, counter_name) \
+  do {                                                  \
+    if (RuntimeCallStats::IsEnabled()) {                \
+      RuntimeCallStats::CorrectCurrentCounterId(        \
+          isolate->counters()->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 430 matching lines @@
   }
 
   Isolate* isolate_ = nullptr;
   RuntimeCallTimer timer_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_