Reland of "[heap] Switch to 500k pages"

src/heap/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 #include <memory>
 #include <unordered_set>
@@ skipping 217 matching lines @@
 class MemoryChunk {
  public:
   enum MemoryChunkFlags {
     IS_EXECUTABLE,
     POINTERS_TO_HERE_ARE_INTERESTING,
     POINTERS_FROM_HERE_ARE_INTERESTING,
     IN_FROM_SPACE,  // Mutually exclusive with IN_TO_SPACE.
     IN_TO_SPACE,    // All pages in new space has one of these two set.
     NEW_SPACE_BELOW_AGE_MARK,
     EVACUATION_CANDIDATE,
-    NEVER_EVACUATE,  // May contain immortal immutables.
+
+    // |NEVER_EVACUATE|: A page tagged with this flag will never be selected
+    // for evacuation. Typically used for immortal immovable pages.
+    NEVER_EVACUATE,
 
     // Large objects can have a progress bar in their page header. These object
     // are scanned in increments and will be kept black while being scanned.
     // Even if the mutator writes to them they will be kept black and a white
     // to grey transition is performed in the value.
     HAS_PROGRESS_BAR,
 
     // |PAGE_NEW_OLD_PROMOTION|: A page tagged with this flag has been promoted
     // from new to old space during evacuation.
     PAGE_NEW_OLD_PROMOTION,
@@ skipping 466 matching lines @@
       (1 << MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING) |
       (1 << MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 
   // Maximum object size that gets allocated into regular pages. Objects larger
   // than that size are allocated in large object space and are never moved in
   // memory. This also applies to new space allocation, since objects are never
   // migrated from new space to large object space. Takes double alignment into
   // account.
   // TODO(hpayer): This limit should be way smaller but we currently have
   // short living objects >256K.
-  static const int kMaxRegularHeapObjectSize = 600 * KB;
+  static const int kMaxRegularHeapObjectSize = 400 * KB;
 
   static inline Page* ConvertNewToOld(Page* old_page, PagedSpace* new_owner);
 
   // Returns the page containing a given address. The address ranges
   // from [page_addr .. page_addr + kPageSize[. This only works if the object
   // is in fact in a page.
   static Page* FromAddress(Address addr) {
     return reinterpret_cast<Page*>(OffsetFrom(addr) & ~kPageAlignmentMask);
   }
 
@@ skipping 80 matching lines @@
 
   bool is_anchor() { return IsFlagSet(Page::ANCHOR); }
 
   intptr_t wasted_memory() { return wasted_memory_.Value(); }
   void add_wasted_memory(intptr_t waste) { wasted_memory_.Increment(waste); }
   intptr_t available_in_free_list() { return available_in_free_list_.Value(); }
   void add_available_in_free_list(intptr_t available) {
     available_in_free_list_.Increment(available);
   }
 
+  size_t ShrinkToHighWaterMark();
+
 #ifdef DEBUG
   void Print();
 #endif  // DEBUG
 
  private:
   enum InitializationMode { kFreeMemory, kDoNotFreeMemory };
 
   template <InitializationMode mode = kFreeMemory>
   static inline Page* Initialize(Heap* heap, MemoryChunk* chunk,
                                  Executability executable, PagedSpace* owner);
@@ skipping 472 matching lines @@
   void ReportStatistics();
 #endif
 
   // Returns a MemoryChunk in which the memory region from commit_area_size to
   // reserve_area_size of the chunk area is reserved but not committed, it
   // could be committed later by calling MemoryChunk::CommitArea.
   MemoryChunk* AllocateChunk(intptr_t reserve_area_size,
                              intptr_t commit_area_size,
                              Executability executable, Space* space);
 
+  void ShrinkChunk(MemoryChunk* chunk, size_t bytes_to_shrink);
+
   Address ReserveAlignedMemory(size_t requested, size_t alignment,
                                base::VirtualMemory* controller);
   Address AllocateAlignedMemory(size_t reserve_size, size_t commit_size,
                                 size_t alignment, Executability executable,
                                 base::VirtualMemory* controller);
 
   bool CommitMemory(Address addr, size_t size, Executability executable);
 
   void FreeMemory(base::VirtualMemory* reservation, Executability executable);
   void PartialFreeMemory(MemoryChunk* chunk, Address start_free);
@@ skipping 861 matching lines @@
   FreeList* free_list() { return &free_list_; }
 
   base::Mutex* mutex() { return &space_mutex_; }
 
   inline void UnlinkFreeListCategories(Page* page);
   inline intptr_t RelinkFreeListCategories(Page* page);
 
   iterator begin() { return iterator(anchor_.next_page()); }
   iterator end() { return iterator(&anchor_); }
 
+  // Shrink immortal immovable pages of the space to be exactly the size needed
+  // using the high water mark.
+  void ShrinkImmortalImmovablePages();
+
  protected:
   // PagedSpaces that should be included in snapshots have different, i.e.,
   // smaller, initial pages.
   virtual bool snapshotable() { return true; }
 
   bool HasPages() { return anchor_.next_page() != &anchor_; }
 
   // Cleans up the space, frees all pages in this space except those belonging
   // to the initial chunk, uncommits addresses in the initial chunk.
   void TearDown();
@@ skipping 832 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_