[counter] reducing the overhead of RuntimeCallTimerScope

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 474 matching lines @@
 
   const char* name;
   int64_t count = 0;
   base::TimeDelta time;
 };
 
 // RuntimeCallTimer is used to keep track of the stack of currently active
 // timers used for properly measuring the own time of a RuntimeCallCounter.
 class RuntimeCallTimer {
  public:
-  RuntimeCallTimer(RuntimeCallCounter* counter, RuntimeCallTimer* parent)
-      : counter_(counter), parent_(parent) {}
+  inline void Initialize(RuntimeCallCounter* counter,
+                         RuntimeCallTimer* parent) {
+    counter_ = counter;
+    parent_ = parent;
+  }
 
   inline void Start() {
     timer_.Start();
     counter_->count++;
   }
 
   inline RuntimeCallTimer* Stop() {
     base::TimeDelta delta = timer_.Elapsed();
     counter_->time += delta;
     if (parent_ != NULL) {
       parent_->AdjustForSubTimer(delta);
     }
     return parent_;
   }
 
-  void AdjustForSubTimer(base::TimeDelta delta) { counter_->time -= delta; }
+  inline void AdjustForSubTimer(base::TimeDelta delta) {
+    counter_->time -= delta;
+  }
 
  private:
   RuntimeCallCounter* counter_;
   RuntimeCallTimer* parent_;
   base::ElapsedTimer timer_;
 };
 
 struct RuntimeCallStats {
   // Dummy counter for the unexpected stub miss.
   RuntimeCallCounter UnexpectedStubMiss =
@@ skipping 27 matching lines @@
   void Reset();
   void Print(std::ostream& os);
 
   RuntimeCallStats() { Reset(); }
 };
 
 // A RuntimeCallTimerScopes wraps around a RuntimeCallTimer to measure the
 // the time of C++ scope.
 class RuntimeCallTimerScope {
  public:
-  explicit RuntimeCallTimerScope(Isolate* isolate, RuntimeCallCounter* counter);
-  ~RuntimeCallTimerScope();
+  inline explicit RuntimeCallTimerScope(Isolate* isolate,
+                                        RuntimeCallCounter* counter) {
+    if (FLAG_runtime_call_stats) Enter(isolate, counter);
+  }
+  inline ~RuntimeCallTimerScope() {
+    if (FLAG_runtime_call_stats) Leave();
+  }
+
+  void Enter(Isolate* isolate, RuntimeCallCounter* counter);
+  void Leave();
 
  private:
   Isolate* isolate_;
   RuntimeCallTimer timer_;
 };
 
 #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)   \
@@ skipping 391 matching lines @@
 
   explicit Counters(Isolate* isolate);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Counters);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_