Changeset 164742 in webkit for trunk/Source/WTF/wtf/FastMalloc.cpp

Timestamp:

Feb 26, 2014, 1:17:35 PM (11 years ago)

Author:

[email protected]

Message:

FastMalloc should use vm_page_shift intead of PAGE_SHIFT.
​https://bugs.webkit.org/show_bug.cgi?id=129370

Reviewed by Mark Rowe.

"Doesn't this lead to the page map using fewer bits than it was before?
It seems like this will cause some page addresses to no longer be
representable in the map when using 4K pages. Am I missing something?"

• wtf/FastMalloc.cpp:
  • bdash raises a valid point. This should make the TCMalloc_PageMap larger than absolutely necessary, rather than potentially too small.

File:

• trunk/Source/WTF/wtf/FastMalloc.cpp (modified) (4 diffs)

trunk/Source/WTF/wtf/FastMalloc.cpp

@@ -637 +637 @@
 // sense.  In particular, if kMaxSize increases, you may have to
 // increase kNumClasses as well.
+#define K_PAGE_SHIFT_MIN 12
 #define K_PAGE_SHIFT_MAX 14
 #define K_NUM_CLASSES_MAX 77
@@ -1665 +1666 @@
 template <int BITS> class MapSelector {
  public:
-  typedef TCMalloc_PageMap3<BITS-K_PAGE_SHIFT_MAX> Type;
+  typedef TCMalloc_PageMap3<BITS-K_PAGE_SHIFT_MIN> Type;
   typedef PackedCache<BITS, uint64_t> CacheType;
 };
@@ -1683 +1684 @@
 template <> class MapSelector<64> {
  public:
-  typedef TCMalloc_PageMap3<64 - K_PAGE_SHIFT_MAX - kBitsUnusedOn64Bit> Type;
+  typedef TCMalloc_PageMap3<64 - K_PAGE_SHIFT_MIN - kBitsUnusedOn64Bit> Type;
   typedef PackedCache<64, uint64_t> CacheType;
 };
@@ -1691 +1692 @@
 template <> class MapSelector<32> {
  public:
-  typedef TCMalloc_PageMap2<32 - K_PAGE_SHIFT_MAX> Type;
-  typedef PackedCache<32 - K_PAGE_SHIFT_MAX, uint16_t> CacheType;
+  typedef TCMalloc_PageMap2<32 - K_PAGE_SHIFT_MIN> Type;
+  typedef PackedCache<32 - K_PAGE_SHIFT_MIN, uint16_t> CacheType;
 };