Each relay channel has one buffer per CPU, each buffer has one or more
sub-buffers. Messages are written to the first sub-buffer until it is
-too full to contain a new message, in which case it it is written to
+too full to contain a new message, in which case it is written to
the next (if available). Messages are never split across sub-buffers.
At this point, userspace can be notified so it empties the first
sub-buffer, while the kernel continues writing to the next.