Make heap size estimation more accurate.

src/spaces.h

 // Copyright 2011 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 1451 matching lines @@
   // The bytes in the linear allocation area are not included in this total
   // because updating the stats would slow down allocation.  New pages are
   // immediately added to the free list so they show up here.
   intptr_t Available() { return free_list_.available(); }
 
   // Allocated bytes in this space.  Garbage bytes that were not found due to
   // lazy sweeping are counted as being allocated!  The bytes in the current
   // linear allocation area (between top and limit) are also counted here.
   virtual intptr_t Size() { return accounting_stats_.Size(); }
 
-  // As size, but the bytes in the current linear allocation area are not
-  // included.
-  virtual intptr_t SizeOfObjects() { return Size() - (limit() - top()); }
+  // As size, but the bytes in lazily swept pages are estimated and the bytes
+  // in the current linear allocation area are not included.
+  virtual intptr_t SizeOfObjects() {
+    ASSERT(!IsSweepingComplete() || (unswept_dead_bytes_ == 0));
+    return Size() - unswept_dead_bytes_ - (limit() - top());
+  }
 
   // Wasted bytes in this space.  These are just the bytes that were thrown away
   // due to being too small to use for allocation.  They do not include the
   // free bytes that were not found at all due to lazy sweeping.
   virtual intptr_t Waste() { return accounting_stats_.Waste(); }
 
   // Returns the allocation pointer in this space.
-  Address top() {
-    return allocation_info_.top;
-  }
+  Address top() { return allocation_info_.top; }
   Address limit() { return allocation_info_.limit; }
 
   // Allocate the requested number of bytes in the space if possible, return a
   // failure object if not.
   MUST_USE_RESULT inline MaybeObject* AllocateRaw(int size_in_bytes);
 
   virtual bool ReserveSpace(int bytes);
 
   // Give a block of memory to the space's free list.  It might be added to
   // the free list or accounted as waste.
@@ skipping 55 matching lines @@
 
   // Evacuation candidates are swept by evacuator.  Needs to return a valid
   // result before _and_ after evacuation has finished.
   static bool ShouldBeSweptLazily(Page* p) {
     return !p->IsEvacuationCandidate() &&
            !p->IsFlagSet(Page::RESCAN_ON_EVACUATION) &&
            !p->WasSweptPrecisely();
   }
 
   void SetPagesToSweep(Page* first) {
+    ASSERT(unswept_dead_bytes_ == 0);
     if (first == &anchor_) first = NULL;
     first_unswept_page_ = first;
   }
 
+  void MarkPageForLazySweep(Page* p) {
+    unswept_dead_bytes_ += (Page::kObjectAreaSize - p->LiveBytes());
+  }
+
   bool AdvanceSweeper(intptr_t bytes_to_sweep);
 
   bool IsSweepingComplete() {
     return !first_unswept_page_->is_valid();
   }
 
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
   // Returns zero for pages that have so little fragmentation that it is not
@@ skipping 66 matching lines @@
   AllocationInfo allocation_info_;
 
   // Bytes of each page that cannot be allocated.  Possibly non-zero
   // for pages in spaces with only fixed-size objects.  Always zero
   // for pages in spaces with variable sized objects (those pages are
   // padded with free-list nodes).
   int page_extra_;
 
   bool was_swept_conservatively_;
 
+  // The first page to be swept when the lazy sweeper advances. Is set
+  // to NULL when all pages have been swept.
   Page* first_unswept_page_;
 
+  // The number of dead bytes which could be reclaimed by advancing the
+  // lazy sweeper.  This is only an estimation because lazy sweeping is
+  // done conservatively.
+  intptr_t unswept_dead_bytes_;

[Vyacheslav Egorov (Chromium), 2012/01/11 10:16:49]

I would call them free not dead (I think object can be dead but not the byte).

[Michael Starzinger, 2012/01/11 10:34:00]

Done.

+
   // Expands the space by allocating a fixed number of pages. Returns false if
   // it cannot allocate requested number of pages from OS, or if the hard heap
   // size limit has been hit.
   bool Expand();
 
   // Generic fast case allocation function that tries linear allocation at the
   // address denoted by top in allocation_info_.
   inline HeapObject* AllocateLinearly(int size_in_bytes);
 
   // Slow path of AllocateRaw.  This function is space-dependent.
@@ skipping 968 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_