Timekeeping [Was: Re: cvs commit: src/usr.bin/vmstat vmstat.c src/usr.bin/w w.c]

[Marcel Moolenaar]

On Oct 21, 2005, at 9:05 AM, Poul-Henning Kamp wrote:

> In message <20051022011020.T5554 at delplex.bde.org>, Bruce Evans writes:
>
>
>
>> How do you resync laptops after suspending them for long enough for
>> the clock to drift?  Use ntpd and let it step, or use ntpd -x and let
>> it take hours to resync?  The right thing to do is step the clocks to
>> the current time immediately so that they are correct while the  
>> system
>> is actually being used.
>>
>
> Ahh, and now we get into interesting territory:  What _is_ the
> definition of uptime for a laptop which has been suspended ?

I don't think the definition has to change, but I don't know what
the *exact* definition of uptime is. Wikipedia says this:

"Uptime is a measure of the time a computer system has been up and
  running. It came into use to describe the opposite of downtime,
  times when a system was non-operational."

Given this, suspend is downtime and the uptime is therefore defined
as the amount of time since resume.

Doesn't seem unreasonable to me.

> Again, if you have been sitting in DDB, what exactly is the definition
> of "uptime" ?

Since the kernel is non-operational while in DDB, uptime is to
reset when leaving DDB. Again, according to the Wikipedia definition
of uptime. I'm having more problems finding this reasonable, but
it's not unacceptable.

The question therefore is: which definition of uptime do we try to
implement?

-- 
  Marcel Moolenaar         USPA: A-39004          marcel at xcllnt.net