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

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index ec48b324479b6bd90b66fd5af7c728f03e5ac804..c8e40b00c5c2cd178f2f2962b9997ac32aeffe7a 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1283,16 +1283,18 @@ 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);
   }
 
   {
@@ -5575,6 +5577,23 @@ 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_) {
+    old_generation_allocation_limit_ = limit;
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(isolate_, "Dampen: old size: %" V8_PTR_PREFIX

[Hannes Payer (out of office), 2015/06/16 22:29:21]

old limit

[ulan, 2015/06/17 08:47:45]

Done.

+                             "d KB, new limit: %" V8_PTR_PREFIX "d KB (%.1f)\n",
+                   old_gen_size / KB, old_generation_allocation_limit_ / KB,
+                   factor);
+    }
+  }
+}
+
+
 void Heap::EnableInlineAllocation() {
   if (!inline_allocation_disabled_) return;
   inline_allocation_disabled_ = false;