[counters] RuntimeStats: fix wrong bookkeeping when dynamically changing counters.

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/atomic-utils.h"
@@ skipping 488 matching lines @@
 // timers used for properly measuring the own time of a RuntimeCallCounter.
 class RuntimeCallTimer {
  public:
   RuntimeCallCounter* counter() { return counter_; }
   base::ElapsedTimer timer() { return timer_; }
   RuntimeCallTimer* parent() const { return parent_.Value(); }
 
  private:
   friend class RuntimeCallStats;
 
-  inline void Start(RuntimeCallCounter* counter, RuntimeCallTimer* parent) {
-    counter_ = counter;
-    parent_.SetValue(parent);
-    if (FLAG_runtime_stats !=
-        v8::tracing::TracingCategoryObserver::ENABLED_BY_SAMPLING) {
-      timer_.Start();
-    }
-  }
-
-  inline RuntimeCallTimer* Stop() {
-    if (!timer_.IsStarted()) return parent();
-    base::TimeDelta delta = timer_.Elapsed();
-    timer_.Stop();
-    counter_->count++;
-    counter_->time += delta;
-    if (parent()) {
-      // Adjust parent timer so that it does not include sub timer's time.
-      parent()->counter_->time -= delta;
-    }
-    return parent();
-  }
-
-  inline void Elapsed() {
-    base::TimeDelta delta = timer_.Elapsed();
-    counter_->time += delta;
-    if (parent()) {
-      parent()->counter_->time -= delta;
-      parent()->Elapsed();
-    }
-    timer_.Restart();
-  }
+  inline void Start(RuntimeCallCounter* counter, RuntimeCallTimer* parent);
+  inline RuntimeCallTimer* Stop();
+  inline void Elapsed();
+  inline void Subtract(base::TimeDelta delta);
 
   const char* name() { return counter_->name; }
 
   RuntimeCallCounter* counter_ = nullptr;
   base::AtomicValue<RuntimeCallTimer*> parent_;
   base::ElapsedTimer timer_;
 };
 
 #define FOR_EACH_API_COUNTER(V)                            \
   V(ArrayBuffer_Cast)                                      \
@@ skipping 335 matching lines @@
     if (V8_UNLIKELY(FLAG_runtime_stats)) {                               \
       RuntimeCallStats::CorrectCurrentCounterId(                         \
           runtime_call_stats, &RuntimeCallStats::counter_name);          \
     }                                                                    \
   } while (false)
 
 #define TRACE_HANDLER_STATS(isolate, counter_name)                          \
   CHANGE_CURRENT_RUNTIME_COUNTER(isolate->counters()->runtime_call_stats(), \
                                  Handler_##counter_name)
 
+// 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);
+  // 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);
+  inline RuntimeCallTimerScope(RuntimeCallStats* stats,
+                               RuntimeCallStats::CounterId counter_id);
+
+  inline ~RuntimeCallTimerScope() {
+    if (V8_UNLIKELY(stats_ != nullptr)) {
+      RuntimeCallStats::Leave(stats_, &timer_);
+    }
+  }
+
+ private:
+  V8_INLINE void Initialize(RuntimeCallStats* stats,
+                            RuntimeCallStats::CounterId counter_id) {
+    stats_ = stats;
+    RuntimeCallStats::Enter(stats_, &timer_, counter_id);
+  }
+
+  RuntimeCallStats* stats_ = nullptr;
+  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)   \
   HR(gc_idle_time_limit_overshot, V8.GCIdleTimeLimit.Overshot, 0, 10000, 101) \
   HR(gc_idle_time_limit_undershot, V8.GCIdleTimeLimit.Undershot, 0, 10000,    \
      101)                                                                     \
   HR(code_cache_reject_reason, V8.CodeCacheRejectReason, 1, 6, 6)             \
   HR(errors_thrown_per_context, V8.ErrorsThrownPerContext, 0, 200, 20)        \
   HR(debug_feature_usage, V8.DebugFeatureUsage, 1, 7, 7)                      \
@@ skipping 391 matching lines @@
 
   RuntimeCallStats runtime_call_stats_;
 
   friend class Isolate;
 
   explicit Counters(Isolate* isolate);
 
   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);
-  // 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);
-  inline RuntimeCallTimerScope(RuntimeCallStats* stats,
-                               RuntimeCallStats::CounterId counter_id);
-
-  inline ~RuntimeCallTimerScope() {
-    if (V8_UNLIKELY(stats_ != nullptr)) {
-      RuntimeCallStats::Leave(stats_, &timer_);
-    }
-  }
-
- private:
-  V8_INLINE void Initialize(RuntimeCallStats* stats,
-                            RuntimeCallStats::CounterId counter_id) {
-    stats_ = stats;
-    RuntimeCallStats::Enter(stats_, &timer_, counter_id);
-  }
-
-  RuntimeCallStats* stats_ = nullptr;
-  RuntimeCallTimer timer_;
-};
-
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_