Extract function to compute mutator utilization.

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 4757 matching lines @@
   if (!IsHeapIterable()) {
     CollectAllGarbage(kMakeHeapIterableMask, "Heap::MakeHeapIterable");
   }
   if (mark_compact_collector()->sweeping_in_progress()) {
     mark_compact_collector()->EnsureSweepingCompleted();
   }
   DCHECK(IsHeapIterable());
 }
 
 
+static double ComputeMutatorUtilization(double mutator_speed, double gc_speed) {
+  const double kMinMutatorUtilization = 0.0;
+  if (mutator_speed == 0 || gc_speed == 0) return kMinMutatorUtilization;
+  // Derivation:
+  // mutator_utilization = mutator_time / (mutator_time + gc_time)
+  // mutator_time = 1 / mutator_speed
+  // 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());
+  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());
+  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;
+}
+
+
 bool Heap::HasLowYoungGenerationAllocationRate() {
   const double high_mutator_utilization = 0.993;
-  double mutator_speed = static_cast<double>(
-      tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond());
-  double gc_speed = static_cast<double>(
-      tracer()->ScavengeSpeedInBytesPerMillisecond(kForSurvivedObjects));
-  if (mutator_speed == 0 || gc_speed == 0) return false;
-  double mutator_utilization = gc_speed / (mutator_speed + gc_speed);
-  return mutator_utilization > high_mutator_utilization;
+  return YoungGenerationMutatorUtilization() > high_mutator_utilization;
 }
 
 
 bool Heap::HasLowOldGenerationAllocationRate() {
   const double high_mutator_utilization = 0.993;
-  double mutator_speed = static_cast<double>(
-      tracer()->OldGenerationAllocationThroughputInBytesPerMillisecond());
-  double gc_speed = static_cast<double>(
-      tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond());
-  if (mutator_speed == 0 || gc_speed == 0) return false;
-  double mutator_utilization = gc_speed / (mutator_speed + gc_speed);
-  return mutator_utilization > high_mutator_utilization;
+  return OldGenerationMutatorUtilization() > high_mutator_utilization;
 }
 
 
 bool Heap::HasLowAllocationRate() {
   return HasLowYoungGenerationAllocationRate() &&
          HasLowOldGenerationAllocationRate();
 }
 
 
 bool Heap::HasHighFragmentation() {
@@ skipping 2109 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