Add partitionAllocActualSize() for predicting actual size of allocation

Source/wtf/PartitionAlloc.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 508 matching lines @@
             page->nextPage = 0;
         }
     }
 
     bucket->activePagesHead = 0;
     return false;
 }
 
 static ALWAYS_INLINE void* partitionDirectMap(PartitionRootBase* root, int flags, size_t size)
 {
-    size += kSystemPageOffsetMask;
-    size &= kSystemPageBaseMask;
+    size = partitionDirectMapSize(size);
+
     // Because we need to fake looking like a super page, We need to allocate
     // a bunch of system pages more than "size":
     // - The first few system pages are the partition page in which the super
     // page metadata is stored. We fault just one system page out of a partition
     // page sized clump.
     // - We add a trailing guard page.
     size_t mapSize = size + kPartitionPageSize + kSystemPageSize;
     // Round up to the allocation granularity.
     mapSize += kPageAllocationGranularityOffsetMask;
     mapSize &= kPageAllocationGranularityBaseMask;
@@ skipping 63 matching lines @@
 void* partitionAllocSlowPath(PartitionRootBase* root, int flags, size_t size, PartitionBucket* bucket)
 {
     // The slow path is called when the freelist is empty.
     ASSERT(!bucket->activePagesHead->freelistHead);
 
     // For the partitionAllocGeneric API, we have a bunch of buckets marked
     // as special cases. We bounce them through to the slow path so that we
     // can still have a blazing fast hot path due to lack of corner-case
     // branches.
     bool returnNull = flags & PartitionAllocReturnNull;
-    if (UNLIKELY(!bucket->numSystemPagesPerSlotSpan)) {
+    if (UNLIKELY(partitionBucketIsDirectMapped(bucket))) {
         ASSERT(size > kGenericMaxBucketed);
         ASSERT(bucket == &PartitionRootBase::gPagedBucket);
-        if (size > INT_MAX - kSystemPageSize) {
+        if (size > kGenericMaxDirectMapped) {
             if (returnNull)
                 return 0;
             RELEASE_ASSERT(false);
         }
         return partitionDirectMap(root, flags, size);
     }
 
     // First, look for a usable page in the existing active pages list.
     // Change active page, accepting the current page as a candidate.
     if (LIKELY(partitionSetNewActivePage(bucket->activePagesHead))) {
@@ skipping 83 matching lines @@
     root->globalEmptyPageRingIndex = currentIndex;
 }
 
 void partitionFreeSlowPath(PartitionPage* page)
 {
     PartitionBucket* bucket = page->bucket;
     ASSERT(page != &PartitionRootGeneric::gSeedPage);
     ASSERT(bucket->activePagesHead != &PartitionRootGeneric::gSeedPage);
     if (LIKELY(page->numAllocatedSlots == 0)) {
         // Page became fully unused.
-        if (UNLIKELY(!bucket->numSystemPagesPerSlotSpan)) {
+        if (UNLIKELY(partitionBucketIsDirectMapped(bucket))) {
             partitionDirectUnmap(page);
             return;
         }
         // If it's the current page, attempt to change it. We'd prefer to leave
         // the page empty as a gentle force towards defragmentation.
         if (LIKELY(page == bucket->activePagesHead) && page->nextPage) {
             if (partitionSetNewActivePage(page->nextPage)) {
                 ASSERT(bucket->activePagesHead != page);
                 // Link the empty page back in after the new current page, to
                 // avoid losing a reference to it.
@@ skipping 123 matching lines @@
     printf("total live: %zu bytes\n", totalLive);
     printf("total resident: %zu bytes\n", totalResident);
     printf("total freeable: %zu bytes\n", totalFreeable);
     fflush(stdout);
 }
 
 #endif // !NDEBUG
 
 } // namespace WTF