On Thu, 30 May 2002, Tony Finch wrote:
> On Wed, May 29, 2002 at 05:56:17AM +1000, Bruce Evans wrote:
> > On Tue, 28 May 2002, Tony Finch wrote:
> >
> > > I noticed that clock(3) currently violates a requirement of POSIX
> > > 2001 (that CLOCKS_PER_SEC is 1000000) and that the various archs
> > > are inconsistent and somtimes different from what is in clocks(7).
> >
> > That is only in a (broken) XSI extension. "Fixing" this would mainly
> > break binary compatibility since it would change from one historical
> > wrong value to another (128 -> 1000000). The first C standard got this
> ...
> Hmm, I've been thinking about this a bit more. Does FreeBSD actually
> keep the necessary statistics at that resolution? As far as I can
> tell it is done internally at microsecond resolution.
It does now, more or less. Process times are stored in struct bintime
in -current. struct bintime has a resolution of 2^-64 seconds. User,
sys and interrupt times are the process time split up statistically
(so their accuracy is much lower than the resolution). This only
affects getrusage() and similar interfaces. clock() could use
timecounters directly and get the 2^-64 resolution, but there is
currently no syscall for this. clock_gettime() is closest.
Bruce
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