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35 .Nd various system timers
40 is not part of the application interface in
43 There are many different real and virtual (timekeeping) clocks with
44 different frequencies:
48 This is a real clock with frequency that happens to be 100.
49 It is not available to applications.
52 This is a real clock with frequency that happens to be 128.
53 It is not directly available to applications.
57 This is a virtual clock with a frequency that happens to be 128.
58 Its actual frequency is given by the macro
62 may be floating point.
67 It is feeble compared with
72 It is implemented by calling
74 and throwing away information and resolution.
78 This is a virtual clock with a frequency that happens to be 128.
79 Its actual frequency is given by the macro
81 (deprecated; do not use) and by
82 .Fn sysconf _SC_CLK_TCK
85 Note that its frequency may be different from
91 It is feeble compared with
98 It is implemented by calling
102 and throwing away information and resolution.
105 This is a real clock with frequency 1024.
110 Applications should determine its actual frequency using
112 or by reading it from the header in the profiling data file.
115 This is a real clock with a nominal frequency of 32768.
116 It is divided down to give the statistic clock and the profiling clock.
117 It is not available to applications.
119 The microseconds clock.
120 This is a virtual clock with frequency 1000000.
121 It is used for most timekeeping in
123 and is exported to applications in
129 This is the clock that should normally be used by
134 This is a real clock/timer with a nominal frequency of 1193182.
135 It has three independent time counters to be used.
136 It is divided down to give the scheduling clock.
137 It is not available to applications.
139 The TSC clock (64-bit register) on fifth-generation or later x86 systems.
140 This is a real clock with a frequency that is equivalent to the number of
141 cycles per second of the CPU(s).
142 Its frequency can be found using the
144 sysctl, if it is available.
145 It is used to interpolate between values of the scheduling clock.
146 It can be accessed using the
152 This is a real clock/timer with a nominal frequency of 3579545.
153 It is accessed via a 24 or 32 bit register.
154 Unlike the TSC clock, it maintains a constant tick rate even when the CPU
155 sleeps or its clock rate changes.
156 It is not available to applications.
161 is not 1000000 then the application is probably using the wrong clock.
164 .Xr clock_gettime 2 ,
174 This manual page was written by
176 after a description posted by