Fix overflow in allocation throughput calculation.

src/heap/gc-tracer.cc

 // Copyright 2014 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.
 
 #include "src/v8.h"
 
 #include "src/heap/gc-tracer.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 597 matching lines @@
     durations += iter->duration_;
     ++iter;
   }
 
   if (durations == 0.0) return 0;
 
   return static_cast<size_t>(bytes / durations + 0.5);
 }
 
 
-size_t GCTracer::AllocatedBytesInLast(double time_ms) const {
+size_t GCTracer::AllocationThroughputInBytesPerMillisecond(
+    double time_ms) const {
   size_t bytes = new_space_allocation_in_bytes_since_gc_ +
                  old_generation_allocation_in_bytes_since_gc_;
   double durations = allocation_duration_since_gc_;
   AllocationEventBuffer::const_iterator iter = allocation_events_.begin();
   const size_t max_bytes = static_cast<size_t>(-1);
   while (iter != allocation_events_.end() && bytes < max_bytes - bytes &&
          durations < time_ms) {
     bytes += iter->allocation_in_bytes_;
     durations += iter->duration_;
     ++iter;
   }
 
   if (durations == 0.0) return 0;
 
-  bytes = static_cast<size_t>(bytes * (time_ms / durations) + 0.5);
-  // Return at least 1 since 0 means "no data".
-  return std::max<size_t>(bytes, 1);
+  return static_cast<size_t>(bytes / durations + 0.5);
 }
 
 
 size_t GCTracer::CurrentAllocationThroughputInBytesPerMillisecond() const {
   static const double kThroughputTimeFrame = 5000;
-  size_t allocated_bytes = AllocatedBytesInLast(kThroughputTimeFrame);
-  if (allocated_bytes == 0) return 0;
-  return static_cast<size_t>((allocated_bytes / kThroughputTimeFrame) + 1);
+  return AllocationThroughputInBytesPerMillisecond(kThroughputTimeFrame);
 }
 
 
 double GCTracer::ContextDisposalRateInMilliseconds() const {
   if (context_disposal_events_.size() < kRingBufferMaxSize) return 0.0;
 
   double begin = base::OS::TimeCurrentMillis();
   double end = 0.0;
   ContextDisposalEventBuffer::const_iterator iter =
       context_disposal_events_.begin();
@@ skipping 21 matching lines @@
 
 
 bool GCTracer::SurvivalEventsRecorded() const {
   return survival_events_.size() > 0;
 }
 
 
 void GCTracer::ResetSurvivalEvents() { survival_events_.reset(); }
 }
 }  // namespace v8::internal