diff -up webkitgtk-2.19.91/Source/JavaScriptCore/heap/MarkedBlock.h.page_size webkitgtk-2.19.91/Source/JavaScriptCore/heap/MarkedBlock.h
--- webkitgtk-2.19.91/Source/JavaScriptCore/heap/MarkedBlock.h.page_size	2018-02-21 09:55:37.388754142 +0100
+++ webkitgtk-2.19.91/Source/JavaScriptCore/heap/MarkedBlock.h	2018-02-21 09:55:51.789690916 +0100
@@ -67,7 +67,7 @@ private:
     friend class Handle;
 public:
     static constexpr size_t atomSize = 16; // bytes
-    static constexpr size_t blockSize = 16 * KB;
+    static constexpr size_t blockSize = 64 * KB;
     static constexpr size_t blockMask = ~(blockSize - 1); // blockSize must be a power of two.
 
     static constexpr size_t atomsPerBlock = blockSize / atomSize;