Linux credit based algorithm and other scheduling algorithms

Question

Compare between Linux credit based algorithm and other scheduling algorithms?

Answer 1

For the conventional time, shared processes, Linux employ a prioritized, credit-based algorithm. Each process possesses assured number of scheduling credits; while a new task has to be selected to run, the process with most credits is chosen. Every time that a timer interrupt take place, the currently running process loses one credit; while its credits reaches zero, it is suspended and another process is selected. If no run able processes have any credits, then Linux carry out a recrediting operation, adding credits to every process in the system (instead of just to the runnable ones), according to the following rule:

Credits = credits/2 + priority

The above scheduling class is employed for time-shared process and the in Linux for the real-time scheduling is simpler it employs scheduling classes: first come, first served (FCFS), & round-robin (RR) .In both cases, each of the process has a priority in addition to its scheduling class. In time-sharing scheduling, though, processes of distinct priorities can still compete with one another to some extent; in real-time scheduling, the scheduler always runs the process along with the highest priority. Amongst processes of equal priority, it runs the process which has been waiting longest. The only difference among FCFS and RR scheduling is that FCFS processes continue to run till they either exit or block, while a round-robin process will be preempted after a while and will be moved to the end of the scheduling queue.