Re: nanosecond timestamp

[Darren Reed <darrenr () reed wattle id au>]

In some email I received from rick jones, sie wrote:
> > > BTW, where are you getting the nanosecond-resolution time stamps in
> > > Solaris?
> >
> > gethrtime
>
> there is such a thing in some of the other OSes as well - netperf will 
> use it for -DHISTOGRAM because it typically is lower overhead.
>
> however, my recollection of the manpages is that it is only good for 
> relative time, not clock time.  perhaps that is "ok" here but it will 
> be a semantic (right term?) difference from gettimeofday().

Perhaps, the man page says:

     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.

So something like "getimeofday(&foo, NULL); foohr = gethrtime()"
would approximately equate foohr with foo, such that you could
use the change in gethrtime() values returned to calculate the
current time with more accuracy than just gettimeofday() ?

Darren
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