Bookkeeping for allocation site pretenuring

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1304 matching lines @@
   SetElementsKind(GetInitialFastElementsKind());
   set_nested_site(Smi::FromInt(0));
   set_memento_create_count(Smi::FromInt(0));
   set_memento_found_count(Smi::FromInt(0));
   set_pretenure_decision(Smi::FromInt(0));
   set_dependent_code(DependentCode::cast(GetHeap()->empty_fixed_array()),
                      SKIP_WRITE_BARRIER);
 }
 
 
+void AllocationSite::MarkZombie() {
+  ASSERT(!IsZombie());
+  set_pretenure_decision(Smi::FromInt(kZombie));
+  // Clear all non-smi fields
+  set_transition_info(Smi::FromInt(0));
+  set_dependent_code(DependentCode::cast(GetHeap()->empty_fixed_array()),
+                     SKIP_WRITE_BARRIER);
+}
+
+
 // Heuristic: We only need to create allocation site info if the boilerplate
 // elements kind is the initial elements kind.
 AllocationSiteMode AllocationSite::GetMode(
     ElementsKind boilerplate_elements_kind) {
   if (FLAG_track_allocation_sites &&
       IsFastSmiElementsKind(boilerplate_elements_kind)) {
     return TRACK_ALLOCATION_SITE;
   }
 
   return DONT_TRACK_ALLOCATION_SITE;
 }
 
 
 AllocationSiteMode AllocationSite::GetMode(ElementsKind from,
                                            ElementsKind to) {
   if (FLAG_track_allocation_sites &&
       IsFastSmiElementsKind(from) &&
       IsMoreGeneralElementsKindTransition(from, to)) {
     return TRACK_ALLOCATION_SITE;
   }
 
   return DONT_TRACK_ALLOCATION_SITE;
 }
 
 
 inline bool AllocationSite::CanTrack(InstanceType type) {
+  if (FLAG_allocation_site_pretenuring) {
+    return type == JS_ARRAY_TYPE || type == JS_OBJECT_TYPE;
+  }
   return type == JS_ARRAY_TYPE;
 }
 
 
 inline DependentCode::DependencyGroup AllocationSite::ToDependencyGroup(
     Reason reason) {
   switch (reason) {
     case TENURING:
       return DependentCode::kAllocationSiteTenuringChangedGroup;
       break;
     case TRANSITIONS:
       return DependentCode::kAllocationSiteTransitionChangedGroup;
       break;
   }
   UNREACHABLE();
   return DependentCode::kAllocationSiteTransitionChangedGroup;
 }
 
 
+inline void AllocationSite::IncrementMementoFoundCount() {
+  int value = memento_found_count()->value();
+  set_memento_found_count(Smi::FromInt(value + 1));
+}
+
+
+inline void AllocationSite::IncrementMementoCreateCount() {
+  ASSERT(FLAG_allocation_site_pretenuring);
+  int value = memento_create_count()->value();
+  set_memento_create_count(Smi::FromInt(value + 1));
+}
+
+
+inline bool AllocationSite::ShouldPretenure() {
+  ASSERT(FLAG_allocation_site_pretenuring);
+  int create_count = memento_create_count()->value();
+  int found_count = memento_found_count()->value();
+  double ratio = create_count > 0

[Hannes Payer (out of office), 2013/11/21 20:52:24]

We have to guard against the case where we just started emitting mementos before
a gc happend. In that state we cannot make a sane pretenuring decision.
Moreover, we do not want to pretenure non-interesting sites, i.e. sites that
just allocated one object. 

Let us add a constant. If the create count is smaller than this constant we
return false. A good value for that constant is hard to find, we have to look
into benchmarks for that but let us start with something reasonable like e.g.
kPretenureMinimumCreated = 100

[mvstanton, 2013/11/22 11:18:51]

Good advice. Done.

+      ? static_cast<double>(found_count) / create_count
+      : 0.0;
+  if (FLAG_trace_track_allocation_sites) {
+    PrintF("(%d, %d) ratio = %f\n", create_count, found_count, ratio);
+  }
+  return ratio >= 0.60;

[Hannes Payer (out of office), 2013/11/21 20:52:24]

This should be a constant in allocation site called e.g. kPretenureRatio.

[mvstanton, 2013/11/22 11:18:51]

Done. Awkwardly, it must be initialized in objects.cc because of the rules
around floating point constants.

+}
+
+
 void JSObject::EnsureCanContainHeapObjectElements(Handle<JSObject> object) {
   object->ValidateElements();
   ElementsKind elements_kind = object->map()->elements_kind();
   if (!IsFastObjectElementsKind(elements_kind)) {
     if (IsFastHoleyElementsKind(elements_kind)) {
       TransitionElementsKind(object, FAST_HOLEY_ELEMENTS);
     } else {
       TransitionElementsKind(object, FAST_ELEMENTS);
     }
   }
@@ skipping 5038 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_