Scheduler mod: dropping to low power...

[Matthew Percival <matthew@xxxxxxxxx>]

G'Day,

	I am looking to make a modification to the scheduler (2.6.14) for an
embedded system.  The basic idea is to drop into a lower power mode,
rather than scheduling an idle task, when there is no real work to be
done.  The plan is then to trigger a wake up on a counter interrupt, so
that it wakes just before the next timeslice is due.

	My first question is: `is this feasible?'  Would it be reasonable for
someone who is not the god of kernel hackers to make something like this
work, and work (reasonably) efficiently.  I think I have some idea about
how to do this, but am concerned I could be missing some points, and
only end up making a real mess of things.  To give some idea of my
relative skill, I have written a couple of drivers, and made a variety
of miscellaneous mods to the kernel before: lots of extensions and
alterations, but very little new ground.

	Secondly, I am thinking of doing this by replacing rq->idle with a task
which calls the sleep function (which will be added to the power
management file).  Is this a good idea, or should I instead call the
routine from a specific part of sched.c (eg somewhere in schedule())?
Replacing the idle function with my routine seems a logical way to do
things, but I have this nasty feeling that it would be the Wrong Thing.

	I am just a little concerned about touching the scheduler, and was
hoping for a little reassurance that I have the right idea before I jump
headlong into things.

	Thanks,

	Matthew


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