Re: [PATCH 1/4] Add clock_gettime_ns syscall

[Richard Cochran]

On Sun, Dec 25, 2011 at 08:51:00AM -0800, Andy Lutomirski wrote:
> 
> This interface intentionally does not support sub-nanosecond
> precision.  For one thing, light only travels about a foot per
> nanosecond, so nanoseconds are really pretty good for networking
> purposes.  For another, 2^64 picoseconds (say) is a short enough
> interval to be inconvenient.  If anyone needs sub-nanosecond
> precision for anything other than profiling, they're welcome to
> figure out an appropriate interface.  For very precise profiling,
> "what time is it" is the wrong question, anyway -- modern CPUs can
> reorder things across time scales much longer than a nanosecond.

This paragraph probably should be updated, since you did add a padding
field for future sub-nanosecond reporting.

Also, on re-reading this, it seems silly to be to introduce a function
called "clock_gettime_ns" and then to say that this function cannot
answer the question, what time is it?

If the interface is a profiling only interface, then the name should
reflect this fact.

Thanks,
Richard
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/