Messages in this thread | | | Date | Mon, 12 Dec 2005 19:48:36 -0800 | From | Nish Aravamudan <> | Subject | Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs |
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On 12/12/05, George Anzinger <george@mvista.com> wrote: > john stultz wrote: > > On Mon, 2005-12-12 at 20:00 +0000, Shailabh Nagar 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. > >>> > >>>There may be performance concerns as you have to access the clock > >>>hardware in getnstimeofday(), but there really is no other way for > >>>reliable finely grained monotonically increasing timestamps. > >>> > > > > > >>Thanks, that clarifies. I guess the other underlying concern here would be whether these > >>improvements (in resolution and reliability) should be going into getnstimeofday() > >>itself (rather than creating a new func for the same) ? Or is it better to leave > >>getnstimeofday as it is ? > > > > > > No, getnstimeofday() is very much needed to get a nanosecond grained > > wall-time clock, so a new function is needed for the monotonic clock. > > > > In my timeofday re-work I have used the name "get_monotonic_clock()" and > > "get_monotonic_clock_ts()" for basically the same functionality > > (providing a ktime and a timespec respectively). You might consider > > naming it as such, but resolving these naming collisions shouldn't be > > too difficult either way. > > Indeed. Lets use a name with "monotonic" in it, please. And, > possibly not "clock". How about get_nsmonotonic_time() or some such?
I agree -- personal preference, though, I prefer units at the end, i.e. get_monotonic_time_ns() or get_monotonic_time_nsecs().
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