Operating Systems: Linux Process Schedule Modifier

摘要

Linux operating system has multitasking and multiprocessing features. As in multiprogramming environment, many processes will reside in main memory and allocating the processor to these processes is a big job for operating systems. So, for any operating system, scheduler should be effective for achieving reasonable throughput.rnLinux classifies processes into two types as normal processes and real time processes. For real time processes, two scheduling algorithms FIFO and Round Robin are used. FIFO scheduler assigns processor to the process, which comes first. When the processes have same priority, Round Robin is adopted with fixed time slice for each process. After its time expires, it is taken out of the processor and kept at the end Round Robin queue.rnShortest Remaining Time Next preemptive scheduler achieves better throughput, possibly low average waiting time and turn- around time than FIFO and Round Robin, in which the scheduler always dispatches the ready process with shortest expected remaining time for completion. The dispatching decision is always made including a newly arrived processes.rnLinux kernel with above modification (SRTN) will reduce the response time of the processes and it will be very useful in Real time Environment.rn"Rewriting a Linux kernel suitable for effective Real Time Environment is in the hand of Process Scheduler"