svn commit: r264384 - head/share/man/man4
brueffer at FreeBSD.org
Sat Apr 12 21:04:54 UTC 2014
Date: Sat Apr 12 21:04:53 2014
New Revision: 264384
mdoc and language improvements.
MFC after: 1 week
--- head/share/man/man4/timecounters.4 Sat Apr 12 20:51:38 2014 (r264383)
+++ head/share/man/man4/timecounters.4 Sat Apr 12 21:04:53 2014 (r264384)
@@ -31,20 +31,20 @@
.Nd kernel time counters subsystem
-Kernel uses several types of time-related devices, such as: real time clocks,
+The kernel uses several types of time-related devices, such as: real time clocks,
time counters and event timers.
-Real time clocks responsible for tracking real world time, mostly when system
+Real time clocks are responsible for tracking real world time, mostly when the system
-Time counters are responsible for tracking purposes, when system is running.
-Event timers are responsible for generating interrupts at specified time or
+Time counters are responsible for tracking purposes, when the system is running.
+Event timers are responsible for generating interrupts at a specified time or
periodically, to run different time-based events.
This page is about the second.
-Time counters are the lowest level of time tracking in kernel.
+Time counters are the lowest level of time tracking in the kernel.
They provide monotonically increasing timestamps with known width and
-They can overflow, drift, etc and so in raw form used only in very limited
-performance-critical places like process scheduler.
+They can overflow, drift, etc and so in raw form can be used only in very limited
+performance-critical places like the process scheduler.
More usable time is created by scaling the values read from the selected
time counter and combining it with some offset, regularly updated by
@@ -54,13 +54,14 @@ on
Different platforms provide different kinds of timer hardware.
-The goal of the time counters subsystem is to provide unified way to access
+The goal of the time counters subsystem is to provide a unified way to access
-Each driver implementing time counters, registers them at the subsystem.
-It is possible to see the list of present time counters, like this, via
+Each driver implementing time counters registers them with the subsystem.
+It is possible to see the list of present time counters, via the
+.Xr sysctl 8
kern.timecounter.choice: TSC-low(-100) HPET(950) i8254(0) ACPI-fast(900) dummy(-1000000)
@@ -81,7 +82,7 @@ kern.timecounter.tc.TSC-low.frequency: 1
+The output nodes are defined as follows:
.It Va kern.timecounter.tc. Ns Ar X Ns Va .mask
is a bitmask, defining valid counter bits,
@@ -90,13 +91,13 @@ is a present counter value,
.It Va kern.timecounter.tc. Ns Ar X Ns Va .frequency
is a counter update frequency,
.It Va kern.timecounter.tc. Ns Ar X Ns Va .quality
-is an integral value, defining how good is this time counter,
-comparing to others.
-Negative value means that this time counter is broken and should not be used.
+is an integral value, defining the quality of this time counter
+compared to others.
+A negative value means this time counter is broken and should not be used.
-Time management code of the kernel chooses one time counter from that list.
-Current choice can be read and affected via
+The time management code of the kernel chooses one time counter from that list.
+The current choice can be read and affected via the
.Sh SEE ALSO
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