[Tinyos-host-mote-wg] Re: [Tinyos-2.0wg] TinyOS Telecon Notes 8/31/05

[Philip Levis]

On Fri, 2005-09-02 at 12:08 +0200, Joe Polastre wrote:

> I've measured that the scheduler idle loop in TinyOS 1.x takes 30us,
> so the extra 20us to check the power state isn't that bad.  If you can
> get down that idle loop, then I'll buy the argument that the 20us is
> critical ;)
> 

A 40% reduction isn't worth pursuing? I'll also bet money that the 2.x
scheduler idle loop will be shorter than the 1.x. (If it isn't now, it
should be and I'll make it so.:) All those pointer operations in 1.x
really were expensive. )

> Phil, basically you're proposing that we keep the HPLPowerManagementM
> with adjustPower() where adjustPower() sets a dirty bit that is
> checked when the node goes to sleep.

If you take a look at the telecon notes, there's a bit more going on.
One issue brought up is the possible need to override this automagic
calculation, e.g., due to a desired minimum wakeup latency. There's also
the question of per-transition pin reconfiguration (Martin's comments on
the mica flash pins).

That being said, IIRC, this was actually Rob's suggestion. I'm of the
opinion that a fanout call to all HPL components to request their
minimum power state (with the combine function taking the highest power
level) is a better approach, for a bunch of reasons. Rob had some
reservations about the efficiency of such an approach, though, so
barring a good performance evaluation demonstrating that the callout
isn't an issue, we're continuing with the current single big mostly
omniscient function approach.

Phil


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