hardclock.9: Refine some details
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
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@ -27,7 +27,7 @@
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 25, 2010
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.Dd July 1, 2021
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.Dt HARDCLOCK 9
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.Os
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.Sh NAME
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@ -39,19 +39,26 @@
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.Sh DESCRIPTION
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The
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.Fn hardclock
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function is called
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.Xr hz 9
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times per second.
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It implements the real-time system clock.
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The argument
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function is called periodically based on pending work.
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The rate ranges from
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.Va hz
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times per second on a very busy system, to twice a second on an idle system.
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The
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.Va cnt
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is the estimated number of ticks since the last call to
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.Fn hardclock .
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argument reports an estimate of the number of ticks since the last call.
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The sum of
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.Va cnt
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over a second averages
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.Va hz
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over the long haul.
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See
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.Xr hz 9
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for important details over shorter time scales.
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The argument
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.Va usermode
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is none-zero when
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.Fn hardclock
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is called from a user-mode context.
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is called from an context that interrupted usermode execution.
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.Pp
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.Fn hardclock
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may perform different tasks such as:
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@ -96,5 +103,4 @@ processing.
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.Xr ntp_adjtime 2 ,
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.Xr signal 3 ,
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.Xr ntpd 8 ,
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.Xr callout 9 ,
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.Xr hz 9
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