microtime.9: rewrite description, miscellaneous cleanup

- Remove the bintime interfaces.  They should not be used outside of
  the timecounting layer.  Unsure whether they warrant a manpage of
  their own.
- In the SYNOPSIS, change the variable names for timespec interfaces
  from "tv" to "ts".
- Document the new-ish "nsec" interfaces.
- Rewrite the DESCRIPTION.  Describe every clock completely in its own
  paragraph.  Enumerate all the interfaces in tables.  Explicitly state
  the output format for each interface in said tables.  Add new vocab
  ("hardware", "timestamp") to clarify the differences between the
  "get" and non-"get" interfaces.
- Add the CONTEXT, RETURN VALUES, and ERRORS sections.
- Cross-reference clock_settime(2), timeradd(3), and tc_init(9).

Lots of input from schwarze@.

ok jmc@ schwarze@

1 files changed, 139 insertions, 74 deletions

diff --git a/share/man/man9/microtime.9 b/share/man/man9/microtime.9
index aef446f36fc..b2b0eb406ce 100644
--- a/share/man/man9/microtime.9
+++ b/share/man/man9/microtime.9
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: microtime.9,v 1.22 2020/06/26 18:48:31 cheloha Exp $
+.\"	$OpenBSD: microtime.9,v 1.23 2022/12/28 15:46:39 cheloha Exp $
 .\"     $NetBSD: microtime.9,v 1.2 1999/03/16 00:40:47 garbled Exp $
 .\"
 .\" Copyright (c) 1998 The NetBSD Foundation, Inc.
@@ -28,39 +28,30 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: June 26 2020 $
+.Dd $Mdocdate: December 28 2022 $
 .Dt MICROTIME 9
 .Os
 .Sh NAME
-.Nm microtime ,
-.Nm getmicrotime ,
 .Nm microuptime ,
 .Nm getmicrouptime ,
-.Nm microboottime ,
-.Nm nanotime ,
-.Nm getnanotime ,
 .Nm nanouptime ,
 .Nm getnanouptime ,
+.Nm nsecuptime ,
+.Nm getnsecuptime ,
+.Nm getuptime ,
 .Nm nanoruntime ,
-.Nm nanoboottime ,
-.Nm bintime ,
-.Nm binuptime ,
-.Nm binruntime ,
-.Nm binboottime ,
+.Nm getnsecruntime ,
+.Nm microtime ,
+.Nm getmicrotime ,
+.Nm nanotime ,
+.Nm getnanotime ,
 .Nm gettime ,
-.Nm getuptime
-.Nd system clocks
+.Nm microboottime ,
+.Nm nanoboottime
+.Nd get the time
 .Sh SYNOPSIS
 .In sys/time.h
 .Ft void
-.Fo microtime
-.Fa "struct timeval *tv"
-.Fc
-.Ft void
-.Fo getmicrotime
-.Fa "struct timeval *tv"
-.Fc
-.Ft void
 .Fo microuptime
 .Fa "struct timeval *tv"
 .Fc
@@ -69,86 +60,160 @@
 .Fa "struct timeval *tv"
 .Fc
 .Ft void
-.Fo microboottime
-.Fa "struct timeval *tv"
+.Fo nanouptime
+.Fa "struct timespec *ts"
 .Fc
 .Ft void
-.Fo nanotime
-.Fa "struct timespec *tv"
+.Fo getnanouptime
+.Fa "struct timespec *ts"
 .Fc
-.Ft void
-.Fo getnanotime
-.Fa "struct timespec *tv"
+.Ft uint64_t
+.Fo nsecuptime
+.Fa "void"
 .Fc
-.Ft void
-.Fo nanouptime
-.Fa "struct timespec *tv"
+.Ft uint64_t
+.Fo getnsecuptime
+.Fa "void"
 .Fc
-.Ft void
-.Fo getnanouptime
-.Fa "struct timespec *tv"
+.Ft time_t
+.Fo getuptime
+.Fa "void"
 .Fc
 .Ft void
 .Fo nanoruntime
-.Fa "struct timespec *tv"
+.Fa "struct timespec *ts"
 .Fc
-.Ft void
-.Fo nanoboottime
-.Fa "struct timespec *tv"
+.Ft uint64_t
+.Fo getnsecruntime
+.Fa "void"
 .Fc
 .Ft void
-.Fo bintime
-.Fa "struct bintime *tv"
+.Fo microtime
+.Fa "struct timeval *tv"
 .Fc
 .Ft void
-.Fo binuptime
-.Fa "struct bintime *tv"
+.Fo getmicrotime
+.Fa "struct timeval *tv"
 .Fc
 .Ft void
-.Fo binruntime
-.Fa "struct bintime *tv"
+.Fo nanotime
+.Fa "struct timespec *ts"
 .Fc
 .Ft void
-.Fo binboottime
-.Fa "struct bintime *tv"
+.Fo getnanotime
+.Fa "struct timespec *ts"
 .Fc
 .Ft time_t
 .Fo gettime
 .Fa "void"
 .Fc
-.Ft time_t
-.Fo getuptime
-.Fa "void"
+.Ft void
+.Fo microboottime
+.Fa "struct timeval *tv"
+.Fc
+.Ft void
+.Fo nanoboottime
+.Fa "struct timespec *ts"
 .Fc
 .Sh DESCRIPTION
-This family of functions return different system clocks in various formats.
-The "uptime" functions return the monotonically increasing time since boot.
-The "runtime" functions return the monotonically increasing time since boot,
-less any time spent suspended.
-The "boottime" functions return the UTC time at which the system booted.
-The "time" functions return the current UTC time.
-The various formats for the result are specified with:
-.Bl -tag -offset indent -width "micro"
-.It bin
-result in struct bintime containing seconds and 64-bit fractions of seconds.
-.It nano
-result in struct timespec containing seconds and nanoseconds
-.It micro
-result in struct timeval containing seconds and microseconds
+The kernel has three clocks and a variety of interfaces for reading them.
+.Pp
+The
+.Sy uptime
+clock measures the time elapsed since the system booted.
+It begins at zero and advances monotonically.
+The uptime clock may be read with the following functions:
+.Bl -column "getmicrouptimeX" "Output Format" "Source" -offset indent
+.It Em Name            Ta Em Output Format    Ta Em Source
+.It Fn microuptime     Ta Vt struct timeval   Ta hardware
+.It Fn getmicrouptime  Ta Vt struct timeval   Ta timestamp
+.It Fn nanouptime      Ta Vt struct timespec  Ta hardware
+.It Fn getnanouptime   Ta Vt struct timespec  Ta timestamp
+.It Fn nsecuptime      Ta Ft uint64_t         Ta hardware
+.It Fn getnsecuptime   Ta Ft uint64_t         Ta timestamp
+.It Fn getuptime       Ta Ft time_t           Ta timestamp
 .El
 .Pp
-The functions with the "get" prefix return a less precise result, but much
-faster.
-They should be used where a precision of 10 msec is acceptable and where
-performance is critical.
-The functions without the "get" prefix return the best timestamp that can
-be produced in the given format.
+The
+.Sy runtime
+clock measures the time elapsed since the system booted,
+less any time the system is suspended or hibernating.
+It begins at zero and normally advances monotonically,
+but pauses while the system is suspended or hibernating.
+The runtime clock may be read with the following functions:
+.Bl -column "getnsecruntimeX" "Output Format" "Source" -offset indent
+.It Em Name            Ta Em Output Format    Ta Em Source
+.It Fn nanoruntime     Ta Vt struct timespec  Ta hardware
+.It Fn getnsecruntime  Ta Ft uint64_t         Ta timestamp
+.El
+.Pp
+The
+.Sy UTC
+clock measures the time elapsed since Jan 1 1970 00:00:00
+.Pq the Unix Epoch .
+The clock normally advances monotonically,
+but jumps when a process calls
+.Xr clock_settime 2
+or
+.Xr settimeofday 2 .
+The UTC clock may be read with the following functions:
+.Bl -column "getmicrotimeX" "Output Format" "Source" -offset indent
+.It Em Name            Ta Em Output Format    Ta Em Source
+.It Fn microtime       Ta Vt struct timeval   Ta hardware
+.It Fn getmicrotime    Ta Vt struct timeval   Ta timestamp
+.It Fn nanotime        Ta Vt struct timespec  Ta hardware
+.It Fn getnanotime     Ta Vt struct timespec  Ta timestamp
+.It Fn gettime         Ta Ft time_t           Ta timestamp
+.El
+.Pp
+The kernel also maintains a
+.Sy boot timestamp .
+It is the moment on the UTC clock when the system booted.
+The timestamp jumps when a process calls
+.Xr clock_settime 2
+or
+.Xr settimeofday 2 .
+The boot timestamp may be read with the following functions:
+.Bl -column "microboottimeX" "Output Format" "Source" -offset indent
+.It Em Name            Ta Em Output Format    Ta Em Source
+.It Fn microboottime   Ta Vt struct timeval   Ta timestamp
+.It Fn nanoboottime    Ta Vt struct timespec  Ta timestamp
+.El
+.Pp
+Functions that source from the
+.Em hardware
+provide the most precise result possible.
+Functions that source from a
+.Em timestamp
+provide a far less precise result,
+but do so very quickly.
+On most platforms,
+timestamps are updated approximately 100 times per second.
+.Sh CONTEXT
+These functions may be called during autoconf,
+from process context,
+or from any interrupt context.
+.Sh RETURN VALUES
+.Fn nsecuptime ,
+.Fn getnsecuptime ,
+and
+.Fn getnsecruntime
+return a count of nanoseconds.
+.Pp
+.Fn getuptime
+and
+.Fn gettime
+return a count of seconds.
+.Sh ERRORS
+These functions are always successful,
+and no return value is reserved to indicate an error.
 .Sh CODE REFERENCES
-The implementation of these functions is partly machine dependent, but
-the bulk of the code is in the file
-.Pa sys/kern/kern_tc.c .
+.Pa sys/kern/kern_tc.c
 .Sh SEE ALSO
+.Xr clock_settime 2 ,
 .Xr settimeofday 2 ,
+.Xr timeradd 3 ,
 .Xr hardclock 9 ,
 .Xr hz 9 ,
-.Xr inittodr 9
+.Xr inittodr 9 ,
+.Xr tc_init 9