We Talk Coding
In operating systems, what is the difference between execution time and period?
Much of the literature in real-time operating systems has equations with execution time and period as variables (see for example p6 of http://www.cs.colorado.edu/~nutt/CS5473/Papers/stankovic94implications.pdf). What is the difference between the two? The general impression I get is that execution time is the amount of time the actual execution takes, while the period is the rate at which the task executes, but how can you even talk about a period for a task that e.g. executes just once? Am I misunderstanding this? The formatting of the web address got messed up, here it is again: http://www.cs.colorado.edu/~nutt/CS5473/Papers/stankovic94implications.pdf
Public Comments
- This talks about a Real Time Operating Sstem (RTOS). RTOS applications generally work differently than the software you are thinking about. The general straucture of an application on an RTOS is: initialize application do while (1 == 1) { wait for a message/event/semaphore process the message/event/semaphore } There is no batch process or human to fire off a program one time. The programs are started when the computer is started and run until the computer is turned off. Depending on the scheduling algorithm used in the kernel the application will be allowed to run when they have something to process. Processor loading must be balanced by engineering the arrival of the events to not all occur at the same time. There are certainly exceptions to this rule - but they are exceptions. Real time proramming is different than other types of programs.
