Plan 9 /sys/man/9/seconds

NAME

seconds, ticks, fastticks, HZ, MS2HZ, MS2TK, TK2MS, TK2SEC – kernel times and time conversions

SYNOPSIS

long      seconds(void)
m–>ticksMACHP(0)–>ticks
vlong     fastticks(uvlong *hz)
#define HZ           ... #define MS2HZ(t)      ... #define TK2SEC(t)     ... #define TK2MS(t)      ... #define MS2TK(m)      ...

DESCRIPTION

Seconds returns the system's idea of the current time as the number of seconds since the start of the epoch (00:00:00 GMT, January 1, 1970).
The ticks field of the Mach structure pointed to by m returns the number of system–dependent clock ticks on the given processor since system boot. On a multiprocessor, MACHP(0) is sometimes used to provide a reference time, since the tick value might vary slightly across processors.
Fastticks returns the number of ticks since boot as measured by the fastest clock provided by the platform. The frequency of the clock, in ticks per second, is returned through hz, unless it is nil.
The system clock frequencies are platform–dependent. Several symbolic constants and macro functions are defined by the file mem.h to convert between different time units:
HZ          The number of clock ticks per second.
MS2HZ       Milliseconds per clock tick.
TK2SEC(t)   Convert t clock ticks to seconds and return the result (truncating not rounding).
TK2MS(t)    Convert t clock ticks to milliseconds and return the result.
MS2TK(m)    Convert m milliseconds to clock ticks and return the result (truncating).
The functions are often used to calculate delays for timing functions, for instance:

if(atactlrwait(dp–>cp, DHmagic, 0, MS2TK(100))){ ... }


	seconds, ticks, fastticks, HZ, MS2HZ, MS2TK, TK2MS, TK2SEC – kernel times and time conversions


	`/sys/src/9//mem.h /sys/src/9//clock.c /sys/src/9/port/tod.c`