Re: FW: [RFC] A more general timeout specification

[Joe Korty <joe.korty@ccur.com>]

On Wed, Aug 31, 2005 at 03:20:03PM -0600, Christopher Friesen wrote:
> Perez-Gonzalez, Inaky wrote:
> >In this structure,
> >the user specifies:
> >    whether the time is absolute, or relative to 'now'.
> 
> 
> >Timeout_sleep has a return argument, endtime, which is also in
> >'struct timeout' format.  If the input time was relative, then
> >it is converted to absolute and returned through this argument.
> 
> Wouldn't it make more sense for the endtime to be returned in the same 
> format (relative/absolute) as the original timer was specified?  That 
> way an application can set a new timer for "timeout + SLEEPTIME" and on 
> average it will be reasonably accurate.
> 
> In the proposed method, for endtime to be useful the app needs to check 
> the current time, compare with the endtime, and figure out the delta. 
> If you're going to force the app to do all that work anyway, the app may 
> as well use absolute times.
> 
> Chris

The returned timeout struct has a bit used to mark the value as absolute.  Thus
the caller treats the returned timeout as a opaque cookie that can be
reapplied to the next (or more likely, the to-be restarted) timeout.

A general principle is, once a time has been converted to absolute, it
should never be converted back to relative time.  To do so means the
end-time starts to drift from the original end-time.

Regards,
Joe
--
"Money can buy bandwidth, but latency is forever" -- John Mashey