Memory reducer should use the current allocation rate instead of the overall allocation rate.

src/heap/heap.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 4739 matching lines @@
   // gc_time = 1 / gc_speed
   // mutator_utilization = (1 / mutator_speed) /
   //                       (1 / mutator_speed + 1 / gc_speed)
   // mutator_utilization = gc_speed / (mutator_speed + gc_speed)
   return gc_speed / (mutator_speed + gc_speed);
 }
 
 
 double Heap::YoungGenerationMutatorUtilization() {
   double mutator_speed = static_cast<double>(
-      tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond());
+      tracer()->CurrentNewSpaceAllocationThroughputInBytesPerMillisecond());
   double gc_speed = static_cast<double>(
       tracer()->ScavengeSpeedInBytesPerMillisecond(kForSurvivedObjects));
   double result = ComputeMutatorUtilization(mutator_speed, gc_speed);
   if (FLAG_trace_mutator_utilization) {
     PrintIsolate(isolate(),
                  "Young generation mutator utilization = %.3f ("
                  "mutator_speed=%.f, gc_speed=%.f)\n",
                  result, mutator_speed, gc_speed);
   }
   return result;
 }
 
 
 double Heap::OldGenerationMutatorUtilization() {
   double mutator_speed = static_cast<double>(
-      tracer()->OldGenerationAllocationThroughputInBytesPerMillisecond());
+      tracer()
+          ->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond());
   double gc_speed = static_cast<double>(
       tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond());
   double result = ComputeMutatorUtilization(mutator_speed, gc_speed);
   if (FLAG_trace_mutator_utilization) {
     PrintIsolate(isolate(),
                  "Old generation mutator utilization = %.3f ("
                  "mutator_speed=%.f, gc_speed=%.f)\n",
                  result, mutator_speed, gc_speed);
   }
   return result;
@@ skipping 2140 matching lines @@
     *object_type = "CODE_TYPE";                                                \
     *object_sub_type = "CODE_AGE/" #name;                                      \
     return true;
     CODE_AGE_LIST_COMPLETE(COMPARE_AND_RETURN_NAME)
 #undef COMPARE_AND_RETURN_NAME
   }
   return false;
 }
 }  // namespace internal
 }  // namespace v8