function byteLength(data) {
  if (!data) {
    return 0
  }

  if (data instanceof Buffer) {
    return data.length
  }

  return Buffer.byteLength(data, 'utf8')
}
FLN pretty much decided on his own recognizance that 64K was a good point
at which to compress a server response. There's only a loose consensus that
the threshold should probably be much higher than this, if only to keep the
load on the collector down.

FIXME: come up with a better heuristic

@param data