Questions about the implementation of RMS on rtems

[yuanbin zhou]

Sorry for late reply because of paper reading, taking courses and
 unimportant things.

>2. How to use the processor utilization rule and first deadline rule to
> >guarantee as more as possible tasks to run since the execution time of
> >each tasks cannot accurately know before the task run?
>
> This is in the users manual and in the original 1973 JACM paper referenced.
>
> It also includes the assumptions about the underlying OS and environment.

Recently I read the paper written by C.L.LIU(Scheduling Algorithms for
Multiprogramming in a Hard-Real-Time Environment), this paper talks about
the algorithm of RM Scheduling and the proof of it.But now what I am more
concerned about is how to  apply this rule to the analysis of real-time
system.Maybe the analysis of the schedulability of this this system should
be done by off-line tools before system start up.But the analysis of
worse-case execution time may not correct which may result in execution
overrun,so some papers put forward some resource reservation mechanisms to
solve this problem.So confused about the paper reading, so I want to know
 how to handle this situation in "rtems"since that I cannot figure out any
information from the user manual.


> >
> >3. Obey the rate monotonic scheduling algorithm, we can easily set the
> >priority of every periodic tasks. But in many applications, it consists
> >both periodic and aperiodic tasks(such as irregular interrupt which is
> >also essential task), so how to handle the priority setting for this
> >situation or just set the irregular task's priority by manual?
>
> You need to do some academic paper research. There are a number of papers
> describing how to address various task patterns


I read some papers about the handle of periodic tasks and aperiodic tasks.There
existed two kinds of method to solve this problem.
First:the system can schedule the aperiodic tasks by periodic server which
allocates a certain amount of budget for aperiodic execution in every
period time.
 second:there is no benefit for the periodic tasks to complete their tasks
much before their deadlines. So when the aperiodic task coming, it steals
the available slack from the periodic tasks and execute it as soon as
possible.
So can give more detail about the implementation of this in rtems which I
cannot find anything from the user manual and it is really complicated to
find the corresponding source file for all the source files located in only
one directory!
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