Oilpan: always shrink tail-allocated backing storage (reland.)

third_party/WebKit/Source/platform/heap/HeapPage.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 681 matching lines @@
 {
     // It's possible that Vector requests a smaller expanded size because
     // Vector::shrinkCapacity can set a capacity smaller than the actual payload
     // size.
     ASSERT(header->checkHeader());
     if (header->payloadSize() >= newSize)
         return true;
     size_t allocationSize = Heap::allocationSizeFromSize(newSize);
     ASSERT(allocationSize > header->size());
     size_t expandSize = allocationSize - header->size();
-    if (header->payloadEnd() == m_currentAllocationPoint && expandSize <= m_remainingAllocationSize) {
+    if (isObjectAllocatedLast(header) && expandSize <= m_remainingAllocationSize) {

[haraken, 2015/10/09 14:21:41]

isObjectAllocatedAtAllocationPoint ?

[sof, 2015/10/09 14:26:40]

A bit long, but why not; done.

         m_currentAllocationPoint += expandSize;
         m_remainingAllocationSize -= expandSize;
 
         // Unpoison the memory used for the object (payload).
         SET_MEMORY_ACCESSIBLE(header->payloadEnd(), expandSize);
         header->setSize(allocationSize);
         ASSERT(findPageFromAddress(header->payloadEnd() - 1));
         return true;
     }
     return false;
 }
 
 bool NormalPageHeap::shrinkObject(HeapObjectHeader* header, size_t newSize)
 {
     ASSERT(header->checkHeader());
     ASSERT(header->payloadSize() > newSize);
     size_t allocationSize = Heap::allocationSizeFromSize(newSize);
     ASSERT(header->size() > allocationSize);
     size_t shrinkSize = header->size() - allocationSize;
-    if (header->payloadEnd() == m_currentAllocationPoint) {
+    if (isObjectAllocatedLast(header)) {
         m_currentAllocationPoint -= shrinkSize;
         m_remainingAllocationSize += shrinkSize;
         SET_MEMORY_INACCESSIBLE(m_currentAllocationPoint, shrinkSize);
         header->setSize(allocationSize);
         return true;
     }
     ASSERT(shrinkSize >= sizeof(HeapObjectHeader));
     ASSERT(header->gcInfoIndex() > 0);
     Address shrinkAddress = header->payloadEnd() - shrinkSize;
     HeapObjectHeader* freedHeader = new (NotNull, shrinkAddress) HeapObjectHeader(shrinkSize, header->gcInfoIndex());
@@ skipping 1107 matching lines @@
 
     m_hasEntries = true;
     size_t index = hash(address);
     ASSERT(!(index & 1));
     Address cachePage = roundToBlinkPageStart(address);
     m_entries[index + 1] = m_entries[index];
     m_entries[index] = cachePage;
 }
 
 } // namespace blink