Changes to improve the performance of reading a snapshot.

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 107 matching lines @@
   // invoke GC by itself.
   PageSpaceController(Heap* heap,
                       int heap_growth_ratio,
                       int heap_growth_max,
                       int garbage_collection_time_ratio);
   ~PageSpaceController();
 
   // Returns whether growing to 'after' should trigger a GC.
   // This method can be called before allocation (e.g., pretenuring) or after
   // (e.g., promotion), as it does not change the state of the controller.
-  bool NeedsGarbageCollection(SpaceUsage after) const;
+  bool NeedsGarbageCollection(intptr_t after_capacity_in_words) const;
 
   // Should be called after each collection to update the controller state.
   void EvaluateGarbageCollection(SpaceUsage before,
                                  SpaceUsage after,
                                  int64_t start, int64_t end);
 
   int64_t last_code_collection_in_us() { return last_code_collection_in_us_; }
   void set_last_code_collection_in_us(int64_t t) {
     last_code_collection_in_us_ = t;
   }
@@ skipping 56 matching lines @@
   };
 
   PageSpace(Heap* heap, intptr_t max_capacity_in_words);
   ~PageSpace();
 
   uword TryAllocate(intptr_t size,
                     HeapPage::PageType type = HeapPage::kData,
                     GrowthPolicy growth_policy = kControlGrowth);
 
   bool NeedsGarbageCollection() const {
-    return page_space_controller_.NeedsGarbageCollection(usage_) ||
-           NeedsExternalGC();
+    const bool needs_gc =
+        page_space_controller_.NeedsGarbageCollection(usage_.capacity_in_words);
+    return  needs_gc || NeedsExternalGC();
   }
 
   intptr_t UsedInWords() const { return usage_.used_in_words; }
   intptr_t CapacityInWords() const { return usage_.capacity_in_words; }
   intptr_t ExternalInWords() const {
     return usage_.external_in_words;
   }
   SpaceUsage GetCurrentUsage() const { return usage_; }
 
   bool Contains(uword addr) const;
@@ skipping 114 matching lines @@
   intptr_t collections_;
 
   friend class PageSpaceController;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_