What is CFS in Linux?

What is CFS in Linux?

The Completely Fair Scheduler (CFS) is a process scheduler that was merged into the 2.6. 23 (October 2007) release of the Linux kernel and is the default scheduler of the tasks of the SCHED_NORMAL class (i.e., tasks that have no real-time execution constraints).

How does Linux kernel scheduler work?

A scheduler chooses the next task to be run, and maintains the order, which all the processes on the system should be run in, as well. In the same way as most operating systems out there, Linux implements preemptive multitasking. Meaning, the scheduler decides when one process ceases running and the other begins.

What is a time slice in computing?

A short interval of time allotted to each user or program in a multitasking or timesharing system. Time slices are typically in milliseconds.

Does Linux still use CFS?

Completely fair Scheduler (CFS) and Brain Fuck Scheduler (BFS) are two different process schedulers currently used in Linux. As any program is loaded as process in RAM and then CPU executes the process according to the priority of the process….1. Completely fair Scheduler (CFS) :

How scheduling works in Linux?

Linux uses a Completely Fair Scheduling (CFS) algorithm, which is an implementation of weighted fair queueing (WFQ). Imagine a single CPU system to start with: CFS time-slices the CPU among running threads. There is a fixed time interval during which each thread in the system must run at least once.

What scheduling algorithm is used in Linux?

The Round Robin algorithm is generally used in time sharing environments. The algorithm used by Linux scheduler is a complex scheme with combination of preemptive priority and biased time slicing. It assigns longer time quantum to higher priority tasks and shorter time quantum to lower priority tasks.

How long is a time slice?

A typical time slice today is between 10-100 milliseconds, with a context switch time of 0.1 to 1 millisecond.

What will happen if the chosen time quantum for RR scheduling is too long?

1 Answer. In Round Robin Scheduling the time quantum is fixed and then processes are scheduled such that no process get CPU time more than one time quantum in one go. If time quantum is too large, the response time of the processes is too much which may not be tolerated in interactive environment.