For this case it doesn't matter how big the time slices are. For CPU bound tasks if you've got an extremely important task and thousands of unimportant tasks, then all those unimportant tasks cripple the performance of the important task. The history of Linux' schedulers is quite enlightening (and people have been reported to be sucked into hacking it, never to be seen again. The problem with round robin is that tasks aren't equal. Pabla's discussion of the Completely fair scheduler in Linux to get a feel of the problems to be solved.

The '80%' rule of thumb is just that, it works (most of the time, for most workloads, and probably makes very little practical difference if it is 60% or 90%). So sometimes (i.e., by time slice end) you will force it. You want to do this hopefully only when forced (the running program does a system call, which forces a context switch anyway a high-priority interruption arrives), but on the other hand you don't want any process to just monopolize the system by never yielding. When the time-slice length decreases, programs with larger CPU burst will. Using Multi-level queues (like 4-5 of them) the CPU combs out all the incoming. time quantum will be increased then the I/O utilization on a Round-Robin. The new method represents the time slice as a function of the burst time of the waiting process in the ready queue. Assume that context switch overhead is 0 and that new processes are added to the head of the queue except for FCFS, where they are added to the tail. The end of a time slice is costly (need to interrupt the running program, switch over to the kernel, stash away the running process context, restarting another process means loading it's context, cache contents of the processor are now useless and have to be reloaded). This new queue has higher time slice and ends up holding CPU bound processes. traditional round robin scheduling algorithm, by the proposed a new method. Show the scheduling order for these processes under 3 policies: First Come First Serve (FCFS), Shortest-Remaining-Time-First (SRTF), Round-Robin (RR) with time slice quantum 2. Round Robin (RR) CPU scheduling is a scheduling technique that allocate equal time slice known as quantum time (QT) to processes wanting to use the CPU.

Round robin quantum timeslice new