Pretenure some strings into bump-allocated block

runtime/vm/heap.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_HEAP_H_
 #define VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 15 matching lines @@
 DECLARE_FLAG(bool, verify_before_gc);
 DECLARE_FLAG(bool, verify_after_gc);
 DECLARE_FLAG(bool, gc_at_alloc);
 
 class Heap {
  public:
   enum Space {
     kNew,
     kOld,
     kCode,
+    kPretenured,
   };
 
   enum WeakSelector {
     kPeers = 0,
     kHashes,
     kNumWeakSelectors
   };
 
   enum ApiCallbacks {
     kIgnoreApiCallbacks,
@@ skipping 25 matching lines @@
       case kNew:
         // Do not attempt to allocate very large objects in new space.
         if (!IsAllocatableInNewSpace(size)) {
           return AllocateOld(size, HeapPage::kData);
         }
         return AllocateNew(size);
       case kOld:
         return AllocateOld(size, HeapPage::kData);
       case kCode:
         return AllocateOld(size, HeapPage::kExecutable);
+      case kPretenured:
+        return AllocatePretenured(size);
       default:
         UNREACHABLE();
     }
     return 0;
   }
 
   // Track external data.
   void AllocateExternal(intptr_t size, Space space);
   void FreeExternal(intptr_t size, Space space);
   // Move external size from new to old space. Does not by itself trigger GC.
@@ skipping 138 matching lines @@
 
   void PrintToJSONObject(Space space, JSONObject* object) const;
 
   // The heap map contains the sizes and class ids for the objects in each page.
   void PrintHeapMapToJSONStream(Isolate* isolate, JSONStream* stream) const {
     return old_space_->PrintHeapMapToJSONStream(isolate, stream);
   }
 
   Isolate* isolate() const { return isolate_; }
 
+  bool ShouldPretenure(intptr_t class_id) const;
+
  private:
   class GCStats : public ValueObject {
    public:
     GCStats() {}
     intptr_t num_;
     Heap::Space space_;
     Heap::GCReason reason_;
 
     class Data : public ValueObject {
      public:
@@ skipping 19 matching lines @@
   };
 
   static const intptr_t kNewAllocatableSize = 256 * KB;
 
   Heap(Isolate* isolate,
        intptr_t max_new_gen_semi_words,  // Max capacity of new semi-space.
        intptr_t max_old_gen_words);
 
   uword AllocateNew(intptr_t size);
   uword AllocateOld(intptr_t size, HeapPage::PageType type);
+  uword AllocatePretenured(intptr_t size);
 
   // GC stats collection.
   void RecordBeforeGC(Space space, GCReason reason);
   void RecordAfterGC();
   void PrintStats();
   void UpdateClassHeapStatsBeforeGC(Heap::Space space);
+  void UpdatePretenurePolicy();
 
   // If this heap is non-empty, updates start and end to the smallest range that
   // contains both the original [start, end) and the [lowest, highest) addresses
   // of this heap.
   void GetMergedAddressRange(uword* start, uword* end) const;
 
   Isolate* isolate_;
 
   // The different spaces used for allocation.
   Scavenger* new_space_;
   PageSpace* old_space_;
 
   WeakTable* new_weak_tables_[kNumWeakSelectors];
   WeakTable* old_weak_tables_[kNumWeakSelectors];
 
   // GC stats collection.
   GCStats stats_;
 
   // This heap is in read-only mode: No allocation is allowed.
   bool read_only_;
 
   // GC on the heap is in progress.
   bool gc_in_progress_;
 
+  int pretenure_policy_;
+
   friend class GCEvent;
   friend class GCTestHelper;
   DISALLOW_COPY_AND_ASSIGN(Heap);
 };
 
 
 class GCEvent {
  public:
   explicit GCEvent(const Heap::GCStats& stats)
       : stats_(stats) {}
@@ skipping 26 matching lines @@
   NoHeapGrowthControlScope();
   ~NoHeapGrowthControlScope();
  private:
   bool current_growth_controller_state_;
   DISALLOW_COPY_AND_ASSIGN(NoHeapGrowthControlScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_HEAP_H_