Timekeeping [Was: Re: cvs commit: src/usr.bin/vmstat vmstat.c
src/usr.bin/w w.c]
Bruce Evans
bde at zeta.org.au
Fri Oct 21 07:31:45 PDT 2005
On Sat, 22 Oct 2005, Bruce Evans wrote:
> On Thu, 20 Oct 2005, Poul-Henning Kamp wrote:
>> In summary: CLOCK_MONOTONIC is our best estimate of how many SI
>> seconds the system have been runing [3].
>
> Actual testing shows that CLOCK_MONOTONIC, or possibly CLOCK_REALTIME
> less the boot time, gives a very bad estimate of how long the system has
> been running. The difference between these clocks was about 500 seconds
> on all systems tested:
>
> % sledge:
> % 1:03PM up 22:45, 1 user, load averages: 0.23, 0.08, 0.02
> % uptime 1 81900
> % uptime 2 82887
> ...
> A large fairly machdine-independent differece is hard to explain. I
> will reboot after sending this to see if one of the values is much
> larger than the uptime when the uptime is < 60 seconds.
Please ignore this. It was a stupid bug. After fixing the bug, there
were no differences.
Bruce
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