Messages in this thread | | | Date | Mon, 12 Dec 2005 16:54:22 -0800 | From | George Anzinger <> | Subject | Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs |
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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?
-- George Anzinger george@mvista.com HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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