This is a simple fix for a typo ("perfetch" rather than "prefetch")
in arc_summary3.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Jason Cohen <jwittlincohen@gmail.com>
Closes#8499