Messages in this thread | | | Subject | Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs | From | john stultz <> | Date | Mon, 12 Dec 2005 11:49:22 -0800 |
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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 -john
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