Examples of Multiple Synchronized Schedulers

Examples of Multiple Synchronized Schedulers

The example in /usr/react/src/examples/multi demonstrates the creation of three synchronized Frame Schedulers. The three use the cycle counter to establish a minor frame interval of 50 ms. All three Frame Schedulers use 20 minor frames per major frame, for a major frame rate of 1 Hz.

The following processes are scheduled in this example:

Processes A and D require a frequency of 20 Hz
Process B requires a frequency of 10 Hz and can consume up to 100 ms of execution time each time
Process C requires a frequence of 5 Hz and can consume up to 200 ms of execution time each time
Process E requires a frequency of 4 Hz and can consume up to 250 ms of execution time each time
Process F requires a frequency of 2 Hz and can consume up to 500 ms of execution time each time
Processes K1, K2 and K3 are background processes that should run as often as possible, when time is available.

The processes are assigned to processors as follows:

Scheduler 1 runs processes A (20 Hz) and K1 (background).
Scheduler 2 runs processes B (10 Hz), C (5 Hz), and K2 (background).
Scheduler 3 runs processes D (20Hz), E (4 Hz), F (2 Hz), and K3.

In order to simplify the coding of the example, all real-time processes use the same function body, process_skeleton(), which is parameterized with the process name, the address of the Frame Scheduler it is to join, and the address of the "real-time" action it is to execute. In the sample code, all real-time actions are empty function bodies (feel free to load them down with code).

The examples in /usr/react/src/examples/ext_intr, user_intr, and vsync_intr are all similar to multi, differing mainly in the time base used. The examples in complete and stop_resume are similar in operation, but more evolved and complex in the way they manage subprocesses.

Tip: It is helpful to use the xdiff program when comparing these similar programs--see the xdiff(1) reference page.