Currently we update timestamps unconditionally when doing read or
write operations. This may slow things down on hardware where
reading timestamps is expensive (e.g. HPET, because of the default
vfs.timestamp_precision setting is nanosecond now) with limited
benefit.
A new sysctl variable, vfs.devfs.dotimes is added, which can be
set to non-zero value when the old behavior is desirable.
Differential Revision: https://reviews.freebsd.org/D2104
Reported by: Mike Tancsa <mike sentex net>
Reviewed by: kib
Relnotes: yes
Sponsored by: iXsystems, Inc.
MFC after: 2 weeks
4f9343fc7c