NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     The system is driven by hardclock(9) interrupts, which occur
at hz frequency,
 and are used to keep track of real time.

     On  systems where another independent clock is available, it
is set at
     stathz frequency, and  used  to  gather  timing  statistics.
Ideally, it
     would  be  better to drive stathz with a slightly randomized
clock, that is
     still a fixed number on average, as this would prevent malicious processes
  from  working around the scheduler.  If a separate clock
is not available,
 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 must be a multiple of
stathz.  This
     will give higher resolution profiling information.

     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,
 but by no more than ten times tickadj.

     Those systems variables are available as a struct  clockinfo
from
     sysctl(3).

SEE ALSO    [Toc]    [Back]

     adjtime(2), clock_getres(2), sysctl(3), hardclock(9), microtime(9)

OpenBSD     3.6                         August      31,      1999