Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs

[George Anzinger]

Shailabh Nagar wrote:
> Jay Lan wrote:
>
> > john stultz wrote:
> >
> >
> > > On Mon, 2005-12-12 at 19:31 +0000, Shailabh Nagar wrote:
> > >
> > >
> > > > Christoph Lameter wrote:
> > > >
> > > >
> > > > > On Wed, 7 Dec 2005, Shailabh Nagar wrote:
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > +void getnstimestamp(struct timespec *ts)
> > > > >
> > > > >
> > > > >
> > > > > There is already getnstimeofday in the kernel.
> > > >
> > > > Yes, and that function is being used within the getnstimestamp()
> > > > being proposed.
> > > > However, John Stultz had advised that getnstimeofday could get
> > > > affected by calls to
> > > > settimeofday and had recommended adjusting the getnstimeofday value
> > > > with wall_to_monotonic.
> > > >
> > > > John, could you elaborate ?
> > >
> > >
> > >
> > > I think you pretty well have it covered.
> > > getnstimeofday + wall_to_monotonic should be higher-res and more
> > > reliable (then TSC based sched_clock(), for example) for getting a
> > > timestamp.
> >
> >
> > How is this proposed function different from
> > do_posix_clock_monotonic_gettime()?
> > It calls getnstimeofday(), it also adjusts with wall_to_monotinic.
> >
> > It seems to me we just need to EXPORT_SYMBOL_GPL the
> > do_posix_clock_monotonic_gettime()?
> >
> > Thanks,
> > - jay
>
>
> Hmmm. Looks like do_posix_clock_monotonic_gettime will suffice for this patch.
>
> Wonder why the clock parameter to do_posix_clock_monotonic_get is needed ?

Because it is called indirectly by the table driven posix clocks and 
timers code where the clock, usually, is needed.

> Doesn't seem to be used.
>
> Any possibility of these set of functions changing their behaviour ?

Always :), but things are pretty stable now.  Might want to add a 
comment that it is being used outside of the posix "box".


--
George Anzinger   george@xxxxxxxxxx
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/
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