* Roman Zippel <[email protected]> wrote:
> > > It's rather simple:
> > > - "timer API" vs "timeout API": I got absolutely no acknowlegement that this
> > > might be a little confusing and in consequence "process timer" may be a
> > > better name.
> >
> > I agree with Thomas on this one. Maybe "timer" and "timeout" are too close,
> > but I think they are the most descriptive names.
> > - timeout is something used for a timeout. Timeouts only actually
> > expire infrequently, so they have a host of attributes associated
> > with that characteristic.
> > - timer is something used to time something. They almost always
> > expire as part of their normal behaviour. In the ktimer code they
> > have a host of attributes related to this characteristic.
>
> There is of course a difference, but is it big enough that they
> deserve different APIs? Just look into <linux/timer.h> it doesn't
> mention timeout once, but according to Thomas that's our "timeout
> API". Look at the description of mod_timer() in timer.c: "modify a
> timer's timeout". It seems I'm not only one who thinks that both are
> closely related.
this is one more area where there's no good substitute from 'walking the
walk', i.e. getting yourself dirty with actual code. I have been
involved with the following variants which were part of the -rt tree:
- we implemented both timeouts and timers with the same
timeout-optimized framework [i.e. with the 'wheel'] - it sucked.
- timers and timeouts with a timer-optimized framework [i.e. with a
binary tree] sucks too, due to the tree overhead.
- we in fact tried another variant too: a hybrid method where timers and
timeouts lived in the timer wheel and some time before (hr) timers
were about to time out they were put into a separate hr-list. This
hybrid solution sucked too.
so then we tried a separate API and subsystem for both of them, and
voila, many of the uglinesses went away, and things became robust.
Ingo
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