+/* Buffers start at INIT_ALLOC size, and roughly double each time we
+ go over the current allocation. MALLOC_OVERHEAD is a guess at the
+ system malloc overhead. We aim to not waste any memory in the
+ underlying page/chunk allocated by the system malloc. */
+#define MALLOC_OVERHEAD (2 * sizeof (size_t))
+#define INIT_ALLOC (64 - MALLOC_OVERHEAD - 1)
+