Messages in this thread | | | Subject | Re: Linux time code | From | john stultz <> | Date | Thu, 17 Aug 2006 15:32:44 -0700 |
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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: > > > On Wed, 16 Aug 2006, john stultz wrote: > > > > > For example there is a POSIX-like sys_clock_gettime() intended > > > > > to server the end-user directly, but there's no counterpart > > > > > do_clock_gettime() to server any in-kernel needs. > > > > > > > > Hmmm.. ktime_get(), ktime_get_ts() and ktime_get_real(), provide > > > > this info. Is there something missing here? > > > > > > 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).
Also the _HR clocks have always been out of tree, so there isn't the binary compatibility worry.
thanks -john
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