Pretenure some strings into bump-allocated block

runtime/vm/pages.h

 // Copyright (c) 2011, 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_PAGES_H_
 #define VM_PAGES_H_
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/ring_buffer.h"
@@ skipping 285 matching lines @@
                                is_protected, is_locked);
   }
 
   Monitor* tasks_lock() const { return tasks_lock_; }
   intptr_t tasks() const { return tasks_; }
   void set_tasks(intptr_t val) {
     ASSERT(val >= 0);
     tasks_ = val;
   }
 
+  // Attempt to allocate from bump block rather than normal freelist.
+  uword TryAllocateDataBump(intptr_t size, GrowthPolicy growth_policy);
+
  private:
   // Ids for time and data records in Heap::GCStats.
   enum {
     // Time
     kMarkObjects = 0,
     kResetFreeLists = 1,
     kSweepPages = 2,
     kSweepLargePages = 3,
     // Data
     kGarbageRatio = 0,
     kGCTimeFraction = 1,
     kPageGrowth = 2,
     kAllowedGrowth = 3
   };
 
   static const intptr_t kAllocatablePageSize = 64 * KB;
 
   uword TryAllocateInternal(intptr_t size,
                             HeapPage::PageType type,
                             GrowthPolicy growth_policy,
                             bool is_protected,
                             bool is_locked);
+  uword TryAllocateInFreshPage(intptr_t size,
+                               HeapPage::PageType type,
+                               GrowthPolicy growth_policy,
+                               bool is_locked);
   HeapPage* AllocatePage(HeapPage::PageType type);
   void FreePage(HeapPage* page, HeapPage* previous_page);
   HeapPage* AllocateLargePage(intptr_t size, HeapPage::PageType type);
   void TruncateLargePage(HeapPage* page, intptr_t new_object_size_in_bytes);
   void FreeLargePage(HeapPage* page, HeapPage* previous_page);
   void FreePages(HeapPage* pages);
   HeapPage* NextPageAnySize(HeapPage* page) const {
     ASSERT((pages_tail_ == NULL) || (pages_tail_->next() == NULL));
     ASSERT((exec_pages_tail_ == NULL) || (exec_pages_tail_->next() == NULL));
     if (page == pages_tail_) {
@@ skipping 13 matching lines @@
 
   Heap* heap_;
 
   Mutex* pages_lock_;
   HeapPage* pages_;
   HeapPage* pages_tail_;
   HeapPage* exec_pages_;
   HeapPage* exec_pages_tail_;
   HeapPage* large_pages_;
 
+  // A block of memory in a data page, managed by bump allocation. The remainder
+  // is kept formatted as a FreeListElement, but is not in any freelist.
+  uword bump_top_;
+  uword bump_end_;
+
   // Various sizes being tracked for this generation.
   intptr_t max_capacity_in_words_;
   SpaceUsage usage_;
 
   // Keep track of running MarkSweep tasks.
   Monitor* tasks_lock_;
   intptr_t tasks_;
 
   PageSpaceController page_space_controller_;
 
   int64_t gc_time_micros_;
   intptr_t collections_;
 
   friend class PageSpaceController;
   friend class SweeperTask;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_