Messages in this thread | | | From | Jesse Barnes <> | Subject | Re: Linux time code | Date | Thu, 17 Aug 2006 15:50:28 -0700 |
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On Thursday, August 17, 2006 3:32 pm, john stultz wrote: > On Thu, 2006-08-17 at 15:11 -0700, Jesse Barnes wrote: > > On Thursday, August 17, 2006 2:58 pm, john stultz wrote: > > > On Thu, 2006-08-17 at 13:43 +0200, Roman Zippel wrote: > > > > What is missing is the abiltity to map a clock to a posix clock, > > > > so that you would have CLOCK_REALTIME/CLOCK_MONOTONIC as NTP > > > > controlled clocks and other CLOCK_* as the raw clock. > > > > > > Is there a use case for this (wanting non-NTP corrected time on a > > > system running NTPd) you have in mind? > > > > Isn't this what CLOCK_MONOTONIC[_HR] is for? It's not supposed to > > jump around at all, so the basic usage model is to use this source > > for timestamping purposes... > > Well, CLOCK_MONOTONIC is not affected by calls to settimeofday() so it > will never go backward, however it does get frequency correction if > provided by NTP (thus a second will be a correct second and you won't > accumulate error).
Hm, I guess that's ok for most of the timestamp applications I'm aware of as long as NTP won't cause the clock to stand still...
FWIW I think many other Unices provide a raw cycle counter via the POSIX clock routines. I don't imagine they're NTP corrected, since at least on IRIX the application is expected to handle even cycle counter wraparound.
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