MirOS Manual: hz(9), profhz(9), stathz(9), tick(9), tickadj(9)

HZ(9)                         BSD Kernel Manual                          HZ(9)

NAME

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

SYNOPSIS

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

DESCRIPTION

     The system is driven by hardclock(9) interrupts, which occur at hz fre-
     quency, 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 incre-
     ment, but by no more than ten times tickadj.

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

SEE ALSO

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

MirOS BSD #10-current          August 31, 1999                               1

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