Re: [RFC] Imprecise timers.

[Rene Herman]

On 22-07-08 14:54, Arjan van de Ven wrote:

> On Tue, 22 Jul 2008 09:19:02 +0200
> Rene Herman <rene.herman@xxxxxxxxxxxx> wrote:
>
> > On 22-07-08 05:02, David Woodhouse wrote:
> >
> > > Many users of timers don't really care too much about exactly when
> > > their timer fires -- and waking a CPU to satisfy such a timer is a
> > > waste of power. This patch implements a 'range' timer which will
> > > fire at a 'convenient' moment within given constraints.
> > >
> > > It's implemented by a deferrable timer at the beginning of the
> > > range, which will run some time later when the CPU happens to be
> > > awake. And a non-deferrable timer at the hard deadline, to ensure
> > > it really does happen by then.
> > Are there actually users for this (not just in theory)? The
> > deferrable timer sort of sounds like all I'd ever want if I, as you
> > say, wouldn't really care...
>
> there's a few; mostly around hardware timeout..For example Stephen want
> it for his drivers.

Hardware I've dealt with is (almost? can't remember anything else) 
exlusively minimal delays and as such this thing seemed like perhaps a 
bit over-apisized...

> EXT3 journal flushing is another one where we can easily say 
> "between 4 and 7 seconds" rather than "exactly at 5"

This a nice-ish example though. It might be considered necessary to make 
the current commit delay when set explicitly be the non-deferrable upper 
bound but almost none do I guess.

Rene.
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