Dampen old generation allocation limit after scavenge if allocation rate is low.

BUG=chromium:491907,chromium:499815
LOG=NO

Review URL: https://codereview.chromium.org/1180203003

Cr-Commit-Position: refs/heads/master@{#29072}

src/heap/heap.cc

@@ -1286,16 +1286,18 @@ bool Heap::PerformGarbageCollection(
   // Update relocatables.
   Relocatable::PostGarbageCollectionProcessing(isolate_);
 
+  double gc_speed = tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond();
+  double mutator_speed = static_cast<double>(
+      tracer()
+          ->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond());
+  intptr_t old_gen_size = PromotedSpaceSizeOfObjects();
   if (collector == MARK_COMPACTOR) {
     // Register the amount of external allocated memory.
     amount_of_external_allocated_memory_at_last_global_gc_ =
         amount_of_external_allocated_memory_;
-    double gc_speed = tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond();
-    double mutator_speed = static_cast<double>(
-        tracer()
-            ->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond());
-    intptr_t old_gen_size = PromotedSpaceSizeOfObjects();
     SetOldGenerationAllocationLimit(old_gen_size, gc_speed, mutator_speed);
+  } else if (HasLowYoungGenerationAllocationRate()) {
+    DampenOldGenerationAllocationLimit(old_gen_size, gc_speed, mutator_speed);
   }
 
   {
@@ -5578,6 +5580,24 @@ void Heap::SetOldGenerationAllocationLimit(intptr_t old_gen_size,
 }
 
 
+void Heap::DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
+                                              double gc_speed,
+                                              double mutator_speed) {
+  double factor = HeapGrowingFactor(gc_speed, mutator_speed);
+  intptr_t limit = CalculateOldGenerationAllocationLimit(factor, old_gen_size);
+  if (limit < old_generation_allocation_limit_) {
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(isolate_, "Dampen: old size: %" V8_PTR_PREFIX
+                             "d KB, old limit: %" V8_PTR_PREFIX "d KB, \n",
+                   "new limit: %" V8_PTR_PREFIX "d KB (%.1f)\n",
+                   old_gen_size / KB, old_generation_allocation_limit_ / KB,
+                   limit / KB, factor);
+    }
+    old_generation_allocation_limit_ = limit;
+  }
+}
+
+
 void Heap::EnableInlineAllocation() {
   if (!inline_allocation_disabled_) return;
   inline_allocation_disabled_ = false;

src/heap/heap.h

@@ -1177,6 +1177,12 @@ class Heap {
   void SetOldGenerationAllocationLimit(intptr_t old_gen_size, double gc_speed,
                                        double mutator_speed);
 
+  // Decrease the allocation limit if the new limit based on the given
+  // parameters is lower than the current limit.
+  void DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
+                                          double gc_speed,
+                                          double mutator_speed);
+
   // Indicates whether inline bump-pointer allocation has been disabled.
   bool inline_allocation_disabled() { return inline_allocation_disabled_; }