auto-revert-stop-on-user-input is a variable defined in `autorevert.el'.
Its value is

When non-nil, user input temporarily interrupts Auto-Revert Mode.
With this setting, Auto-Revert Mode checks for user input after
handling each buffer and does not process any further buffers
(until the next run of the timer) if user input is available.
When nil, Auto-Revert Mode checks files and reverts buffers,
with quitting disabled, without paying attention to user input.
Thus, with this setting, Emacs might be non-responsive at times.

You can customize this variable.