self: super: {
  nsd = (super.nsd.override {
    mmap = true;
  }).overrideDerivation (attrs: {
    # DOC: https://www.raspberrypi.org/forums/viewtopic.php?t=223628
    configureFlags = attrs.configureFlags ++ [
      # Allow to listen on that number of addresses
      "--with-max-ips=8"
      # You can disable the radix tree and use the red-black
      # tree for the main lookups, the red-black tree uses
      # less memory, but uses some more CPU.
      #"--disable-radix-tree"
      # Enable packed structure alignment, uses less memory,
      # but unaligned reads.
      "--enable-packed"
    ];
  });
}