cpu_initclocks(9) [netbsd man page]

CPU_INITCLOCKS(9)					   BSD Kernel Developer's Manual					 CPU_INITCLOCKS(9)

NAME

     cpu_initclocks -- machine-dependent clock setup interface

SYNOPSIS

     #include <sys/systm.h>

     void
     cpu_initclocks(void);

DESCRIPTION

     cpu_initclocks() is invoked by initclocks() during system bootstrap, immediately after autoconfiguration, to perform the machine-dependent
     initialization of clock frequencies and start the real-time and statistic clocks running.

CODE REFERENCES

     Machine-independent clock interface operations are performed within the file sys/kern/kern_clock.c.

SEE ALSO

     autoconf(9)

BSD
								   May 24, 2002 							       BSD

HZ(9)							   BSD Kernel Developer's Manual						     HZ(9)

NAME

     hz, tick, tickadj, stathz, profhz -- system time model

SYNOPSIS

     #include <sys/kernel.h>

     extern int hz;
     extern int tick;
     extern int tickadj;
     extern int stathz;
     extern int profhz;

DESCRIPTION

     The essential clock handling routines in NetBSD are written to operate with two timers that run independently of each other.  The main clock,
     running hz times per second, is used to keep track of real time.

     In another words, hz specifies the number of times the hardclock(9) timer ticks per second.  Normally hardclock(9) increments time by tick
     each time it is called.  If the system clock has drifted, adjtime(2) may be used to skew this increment based on the rate of tickadj.

     The second timer is used to gather timing statistics.  It also handles kernel and user profiling.	If the second timer is programmable, it is
     randomized to avoid aliasing between the two clocks.  The mean frequency of the second timer is stathz.  If a separate clock is not avail-
     able, stathz is set to hz.

     If profiling is enabled, the clock normally used to drive stathz may be run at a higher rate profhz, which is required to be a multiple of
     stathz.  This will give higher resolution profiling information.

     These system variables are also available as struct clockinfo from sysctl(3) and kern.clockrate from sysctl(8).  The hz is hardware-depen-
     dent; it can be overridden (if the machine dependent code supports this) by defining HZ in the kernel configuration file (see options(4)).
     Only override the default value if you really know what you are doing.

SEE ALSO

     adjtime(2), callout(9), hardclock(9), microtime(9), time_second(9)

BSD
								  March 25, 2010							       BSD