+/* Aligning our allocations to 64 has two advantages:
+ *
+ * 1. On x86 platforms, it means that they are cache-line aligned so we
+ * reduce the likelihood that one of our allocations shares a cache line
+ * with some other allocation.
+ *
+ * 2. It lets us use the bottom 6 bits of the pointer to store the tree level
+ * of the node so we can avoid some pointer indirections.
+ */
+#define NODE_ALLOC_ALIGN 64