What is EDF?  Earliest Deadline First?

On Sun, Aug 12, 2012 at 4:10 AM, mansooreh mollaie <[email protected]>wrote:

> Hi,
> I want to use EDF in Tinyos 2.1.1!
> I change TinySchedulerTaskC.nc and relate file!
>


> when i define a task with parameter it error me 'Mytask' declared as a
> task with parameters!
> How I should pass deadline parameter to it?
>

You are missing a number of key concepts.

Tasks are supposed to be simple short run to completion snippets of code.
Passing a deadline parameter to it runs a foul of a number of things.

First, tasks don't have parameters.   Changing this would be a significant
issue.

And then passing a deadline parameter to a task implies that this task is
keeping track of how long it is running which implies that it is running
for a while.  That is yucky in other ways, because it means that task is
hogging the cpu.   Balancing cpu usage in TinyOS is adhoc and relies on
tasks being short.

If you want to do deadline scheduling this should be handled by the
scheduler but also has issues because tinyos tasks are non-preemptive so
what do you do when a deadline approaches.   A reasonable approach is to
use deadlines to select the task with the closest deadline to schedule next.


> please help me!
> Thanks
>
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-- 
Eric B. Decker
Senior (over 50 :-) Researcher
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