Changeset 92092 in webkit

Timestamp:

Jul 31, 2011 4:48:27 PM (13 years ago)

Author:

fpizlo@apple.com

Message:

JSC GC lays out size classes under wrong assumptions about expected
object size.
​https://bugs.webkit.org/show_bug.cgi?id=65437

Reviewed by Oliver Hunt.

Changed the atom size - which is both the smallest allocation size and
the smallest possible stepping unit for size class spacing - from
8 bytes to 4 pointer-size words. This is a 1% win on SunSpider.

• heap/MarkedBlock.h:

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• heap/MarkedBlock.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2011-07-31  Filip Pizlo  <fpizlo@apple.com>
+
+        JSC GC lays out size classes under wrong assumptions about expected
+        object size.
+        https://bugs.webkit.org/show_bug.cgi?id=65437
+
+        Reviewed by Oliver Hunt.
+        
+        Changed the atom size - which is both the smallest allocation size and
+        the smallest possible stepping unit for size class spacing - from
+        8 bytes to 4 pointer-size words.  This is a 1% win on SunSpider.
+
+        * heap/MarkedBlock.h:
+
 2011-07-31  Filip Pizlo  <fpizlo@apple.com>
 

trunk/Source/JavaScriptCore/heap/MarkedBlock.h

@@ -43 +43 @@
         friend class WTF::DoublyLinkedListNode<MarkedBlock>;
     public:
-        static const size_t atomSize = sizeof(double); // Ensures natural alignment for all built-in types.
+        // Ensure natural alignment for native types whilst recognizing that the smallest
+        // object the heap will commonly allocate is four words.
+        static const size_t atomSize = 4 * sizeof(void*);
         static const size_t blockSize = 16 * KB;