Messages in this thread | | | Subject | Re: [ckrm-tech] Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs | From | Matt Helsley <> | Date | Tue, 13 Dec 2005 15:05:59 -0800 |
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On Tue, 2005-12-13 at 10:35 -0800, 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
Ah, yes. I should've searched for gettime rather than gettimeofday when I was looking for a suitable function.
Two minor differences exist:
1) getnstimestamp does not fetch an unused copy of jiffies_64 2) getnstimestamp uses and advertises an explicit maximum resolution
I don't think either of these really matter so I'll post a series of patches:
1) EXPORTing (_SYMBOL_GPL) do_posix_clock_monotonic_gettime() 2) using do_posix_clock_monotonic_gettime() as a timestamp 3) removing getnstimestamp()
Thanks, -Matt Helsley
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