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hardclock.9: Refine some details

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Refine mistakes from adaptaton of NetBSD's hardclock man page to
FreeBSD:
	o clarify what usermode means
	o clarify how often hardclock is called
	o remove Xr callout(9) since that's done elsewhere

Reviewed by:		mav@
Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D30982
This commit is contained in:
Warner Losh 2021-07-02 17:09:19 -06:00
parent b50a4dce18
commit 6329ca325e
1 changed files with 16 additions and 10 deletions
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26
share/man/man9/hardclock.9
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@ -27,7 +27,7 @@
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd March 25, 2010
.Dd July 1, 2021
.Dt HARDCLOCK 9
.Os
.Sh NAME
@ -39,19 +39,26 @@
.Sh DESCRIPTION
The
.Fn hardclock
function is called
.Xr hz 9
times per second.
It implements the real-time system clock.
The argument
function is called periodically based on pending work.
The rate ranges from
.Va hz
times per second on a very busy system, to twice a second on an idle system.
The
.Va cnt
is the estimated number of ticks since the last call to
.Fn hardclock .
argument reports an estimate of the number of ticks since the last call.
The sum of
.Va cnt
over a second averages
.Va hz
over the long haul.
See
.Xr hz 9
for important details over shorter time scales.
The argument
.Va usermode
is none-zero when
.Fn hardclock
is called from a user-mode context.
is called from an context that interrupted usermode execution.
.Pp
.Fn hardclock
may perform different tasks such as:
@ -96,5 +103,4 @@ processing.
.Xr ntp_adjtime 2 ,
.Xr signal 3 ,
.Xr ntpd 8 ,
.Xr callout 9 ,
.Xr hz 9