Uncommit and shrink semi-spaces only on low allocation rate.

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 592 matching lines @@
   double durations = new_space_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 < time_ms) return 0;
+  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);
 }
 
 
+size_t GCTracer::CurrentNewSpaceAllocationThroughputInBytesPerMillisecond()
+    const {
+  static const double kThroughputTimeFrame = 5000;
+  size_t allocated_bytes = NewSpaceAllocatedBytesInLast(kThroughputTimeFrame);
+  if (allocated_bytes == 0) return 0;
+  return static_cast<size_t>((allocated_bytes / kThroughputTimeFrame) + 1);
+}
+
+
 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();
   while (iter != context_disposal_events_.end()) {
     end = iter->time_;
     ++iter;
@@ skipping 18 matching lines @@
 
 
 bool GCTracer::SurvivalEventsRecorded() const {
   return survival_events_.size() > 0;
 }
 
 
 void GCTracer::ResetSurvivalEvents() { survival_events_.reset(); }
 }
 }  // namespace v8::internal