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Man Page Of gethrtime
作者：eygle |【转载时请务必以超链接形式标明文章原始出处和作者信息及本声明】链接：http://www.eygle.com/archives/2004/11/man_page_gethrtime.html
题注:Man Page这里我辑录一些我在学习研究过程中关注过，应用过的，供自己参考，也希望可以见证自己的学习历程。
$ man gethrtimeStandard C Library Functions gethrtime(3C)
NAME
gethrtime, gethrvtime - get high resolution timeSYNOPSIS
#includehrtime_t gethrtime(void);
hrtime_t gethrvtime(void);
DESCRIPTION
The gethrtime() function returns the current high-resolution
real time. Time is expressed as nanoseconds since some arbi-
trary time in the past; it is not correlated in any way to
the time of day, and thus is not subject to resetting or
drifting by way of adjtime(2) or settimeofday(3C). The hi-
res timer is ideally suited to performance measurement
tasks, where cheap, accurate interval timing is required.The gethrvtime() function returns the current high-
resolution LWP virtual time, expressed as total nanoseconds
of execution time. This function requires that micro state
accounting be enabled with the ptime utility (see proc(1)).The gethrtime() and gethrvtime() functions both return an
hrtime_t, which is a 64-bit (long long) signed integer.EXAMPLES
The following code fragment measures the average cost of
getpid(2):hrtime_t start, end;
int i, iters = 100;start = gethrtime();
for (i = 0; i < iters; i++)
getpid();
end = gethrtime();printf("Avg getpid() time = %lld nsec\n", (end - start) / iters);
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|SunOS 5.8 Last change: 10 Apr 1997 1
Standard C Library Functions gethrtime(3C)
SEE ALSO
proc(1), adjtime(2), gettimeofday(3C), settimeofday(3C),
attributes(5)NOTES
Although the units of hi-res time are always the same
(nanoseconds), the actual resolution is hardware dependent.
Hi-res time is guaranteed to be monotonic (it won't go back-
ward, it won't periodically wrap) and linear (it won't occa-
sionally speed up or slow down for adjustment, like the time
of day can), but not necessarily unique: two sufficiently
proximate calls may return the same value.SunOS 5.8 Last change: 10 Apr 1997 2
By eygle on 2004-11-19 21:02 | Comments (0) | Posted to Unix&Linux | Edit |Pageviews:
