-/* reserve inaccessible memory space without allocation any memory */
-static void *memory_map(size_t length)
+/*
+ * The allocation scheme used by the mmap based RCU hash table is to make a
+ * large unaccessible mapping to reserve memory without allocating it.
+ * Then smaller chunks are allocated by overlapping read/write mappings which
+ * do allocate memory. Deallocation is done by an overlapping unaccessible
+ * mapping.
+ *
+ * This scheme was tested on Linux, macOS and Solaris. However, on Cygwin the
+ * mmap wrapper is based on the Windows NtMapViewOfSection API which doesn't
+ * support overlapping mappings.
+ *
+ * An alternative to the overlapping mappings is to use mprotect to change the
+ * protection on chunks of the large mapping, read/write to allocate and none
+ * to deallocate. This works perfecty on Cygwin and Solaris but on Linux a
+ * call to madvise is also required to deallocate and it just doesn't work on
+ * macOS.
+ *
+ * For this reason, we keep to original scheme on all platforms except Cygwin.
+ */
+
+
+/* Reserve inaccessible memory space without allocating it */
+static
+void *memory_map(size_t length)