I'm Korean. Sorry to my awful English.
I was learned RMS Scheduling some days ago.
And, my professor explain these proof.
For example, there are two tasks
The second page that is 'Proof' is what I can't understand.
What is the T_n and C_n.
And what is the meaning of [T2/T1] in the Case(1). ( Obviously, next step in Case(2) )
plz, explain it. Thx.
A periodic task is a task that repeats its execution over and over again. Given a periodic task t there are two quantities associated to it:
TCThe period T measures the interval of time on which the task should be executed at least once. For instance, if T is 100 ms, the task t has to be executed at least once every 100 ms. This means that it has to be executed at least twice every 200 ms, and so on. In other words, after T units of time (e.g., ms) there is a new deadline for t and the goal is to have the task completing a new execution before that deadline expires.
Quantity C measures the maximum execution time of the task. This means that at every instance of its execution the task is guaranteed to complete within C units of time. For the sake of simplicity you can think of C as the constant execution time; just keep in mind that in some cases the execution might complete sooner.
Note that it wouldn't be possible to honor these constraints if C > T. That's why it is assumed that C < T. In the example above, C should be smaller than 100 ms, say C = 40 ms. The case C = T is not interesting either because you will only be able to re-execute t as soon as it completes without any time left for sharing the processor (e.g., the CPU) with other tasks.
The integer quotient [T/C] is the maximum number of times the task can be executed in a period. When this happens, the task will be using the processor a fraction U = C/T of its total processing time. In the example above, we have [T/C] = [100/40] = 2 and you will be able to repeat t at most twice every period of length T, which will allocate U = 40/100 = 0.4 or 40% of the total processing time. The quantity U is called utilization.
With these descriptions you should now be able to go to any online introduction to RMS and make sense of it. For example, you might want to take a look at this one.
