Re: CVS commit: src/sys

[Paul Goyette <paul%whooppee.com@localhost>]

On Wed, 4 Jan 2017, Frank Kardel wrote:

> I would also suggest a 64 bit fraction like in struct bintime, which we 
> already have and use internally for timekeeping anyway along with the 
> timespec, timeval conversion functions.
> Thus collecting can be faster as we don't need to make the conversions when 
> collectiing. I deem converting at userlevel the least worry.
>
> For time stamp fetching see "man 9 microtime" or 
> kern/kern_tc.c:{get,}bin{,up}time(). "get"-versions are cheaper, but only 
> updated at hardclock(). The non-get ones are directly related
> to the current time counter.

Using bintime as the "native" timestamp representation would require
changes to the in-kernel structures, rather than just those used for
exporting the data to userland.  And if the in-kernel structures are
changed, then we'll have to be able to print them from within the
kernel.

For userland we could just do float- or double-divide to convert the
fraction to printable format; it's not clear how we could print these
values from within the kernel (where we're not allowed to use fp?).



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