Re: [RFC] Imprecise timers.

From: Arjan van de Ven
Date: Tue Jul 22 2008 - 08:54:44 EST

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.

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

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