SCHED_OTHER can be used at only static priority 0 (i.e. The POSIX standards thus allow different processes to have different time slice values, but as that same man page states: 'POSIX does not specify any mechanism for controlling the size of the round-robin time quantum.' This might be the reason why there is no known way to set the round-robin time slice value per process or thread in Linux. SCHED_OTHER: Default Linux time-sharing scheduling Than the time quantum, it will be put at the end of the list for its SCHED_RR thread has been running for a time period equal to or longer In Round Robin 2, each process is allotted CPU for given time slice to. Everything described above for SCHED_FIFO also applies to SCHED_RR, except thatĮach thread is allowed to run only for a maximum time quantum. In this document we planned a new methodology to finding quantum time in each. SCHED_RR is a simple enhancement of SCHED_FIFO. Will always immediately preempt any currently running SCHED_OTHER, SCHED_FIFO can be used only with static priorities higher than 0, which means that when a SCHED_FIFO threads becomes runnable, it SCHED_FIFO: First in-first out scheduling
ROUND ROBIN QUANTUM TIMESLICE NEW MANUAL
Here is the differences between SCHED_OTHER, SCHED_FIFO and SCHED_RR based on Linux Manual ()
ROUND ROBIN QUANTUM TIMESLICE NEW UPDATE
Update 2: since Linux 4.13, SCHED_DEADLINE has replaced CBS with the Greedy Reclamation of Unused Bandwidth (GRUB) algorithm. The best resource describing this algorithm is Deadline scheduling in the Linux kernel. Each task under this policy is assigned a deadline, and the earliest-deadline task is executed. This policy implements the Constant Bandwidth Server (CBS) algorithm on top of Earliest Deadline First queues.
Update: since Linux 3.14, there is an additional policy called SCHED_DEADLINE. SCHED_OTHER is the common round-robin time-sharing scheduling policy that schedules a task for a certain timeslice depending on the other tasks running in the system. The difference between SCHED_FIFO and SCHED_RR is that among tasks with the same priority, SCHED_RR performs a round-robin with a certain timeslice SCHED_FIFO, instead, needs the task to explicitly yield the processor. Tasks with these policies preempt every other task, which can thus easily go into starvation (if they don't release the CPU). They implement the fixed-priority real-time scheduling specified by the POSIX standard. SCHED_FIFO and SCHED_RR are so called "real-time" policies.
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