Re: [patch] CFS scheduler, -v8

[Pavel Machek <pavel@ucw.cz>]

Hi!

> >>You say there is "no danger of overflow", and I mostly 
> >>agree that once
> >>we're talking about 64-bit values, the overflow issue 
> >>simply doesn't
> >>exist, and furthermore the difference between 63 and 
> >>64 bits is not really
> >>relevant, so there's no major reason to actively avoid 
> >>signed entries.
> >>
> >>So in that sense, it all sounds perfectly sane. And 
> >>I'm definitely not
> >>sure your "292 years after bootup" worry is really 
> >>worth even considering.
> >>
> >
> >I would hate to tell mission control for Mankind's 
> >first mission to another
> >star to reboot every 200 years because "there is no 
> >need to worry about it."
> >
> >As a matter of principle an OS should never need a 
> >reboot (with exception for upgrading). If you say you 
> >have to reboot every 200 years, why not every 100? 
> >Every 50? .... Every 45 days (you know what I am 
> >referring to :-) ?
> 
> There's always going to be an upper limit on the 
> representation of time. At least until we figure out 
>  how to implement infinity properly.

There's also upper limit on life time of this universe. 1000 bits is
certainly enough  to represent that in u-seconds.

Also notice that current cpus were not designed to work 300 years.
When we have hw designed for 50 years+, we can start to worry.

							Pavel
-- 
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