The Linux process scheduler is a preemptive priority-based scheduler. The scheduler selects the next process to run based on its priority and other factors. The scheduler is implemented as a first-in, first-out (FIFO) queue.
The Linux process scheduler supports several scheduling algorithms:
The scheduler uses the following algorithm to select the next process to run:
Each process is assigned a priority. The priority is an integer value between -20 and 19. The lower the priority value, the higher the priority of the process. The default priority of a process is 0.
A process can be assigned a higher priority by using the nice
command. For example, to assign a priority of 10 to the firefox
process, you would use the following command:
$ nice -n 10 firefox
A process can be assigned a lower priority by using the renice
command. For example, to assign a priority of -10 to the firefox
process, you would use the following command:
$ renice -n -10 firefox
Processes are classified into one of the following scheduling classes:
Real-time processes have the highest priority. They are guaranteed to be scheduled.
Best-effort processes have a priority between 0 and 99. They are not guaranteed to be scheduled.
Idle processes have the lowest priority. They are only scheduled when there are no other processes to run.
Processes can be scheduled using one of the following policies:
FIFO is the simplest scheduling policy. It schedules processes in the order they are created.
RR is a more advanced scheduling policy. It schedules processes in a round-robin fashion.
SPP is a static priority scheduling policy. It schedules processes based on their static priority.
DPP is a dynamic priority scheduling policy. It schedules processes based on their dynamic priority.
MQS is a multiple queue scheduling policy. It schedules processes based on their queue.
CFS is a completely fair scheduling policy. It schedules processes based on their wait time.
The Linux process scheduler uses the following parameters to schedule processes:
nice
: The priority of the process.rt_priority
: The real-time priority of the process.policy
: The scheduling policy of the process.sched_latency
: The maximum time a process can be delayed before it is scheduled.sched_min_granularity
: The minimum time between schedulings of the process.sched_wakeup_granularity
: The time between schedulings of the process when it is woken up.The Linux process scheduler is a preemptive priority-based scheduler. The scheduler selects the next process to run based on its priority and other factors. The scheduler is implemented as a first-in, first-out (FIFO) queue.
The scheduler uses the following algorithm to select the next process to run:
Each process is assigned a priority. The priority is an integer value between -20 and 19. The lower the priority value, the higher the priority of the process.
Processes are classified into one of the following scheduling classes:
Real-time processes have the highest priority. They are guaranteed to be scheduled.
Best-effort processes have a priority between 0 and 99. They are not guaranteed to be scheduled.
Idle processes have the lowest priority. They are only scheduled when there are no other processes to run.
Processes can be scheduled using one of the following policies:
FIFO is the simplest scheduling policy. It schedules processes in the order they are created.
RR is a more advanced scheduling policy. It schedules processes in a round-robin fashion.
SPP is a static priority scheduling policy. It schedules processes based on their static priority.
DPP is a dynamic priority scheduling policy. It schedules processes based on their dynamic priority.
MQS is a multiple queue scheduling policy. It schedules processes based on their queue.
CFS is a completely fair scheduling policy. It schedules processes based on their wait time.
The Linux process scheduler uses the following parameters to schedule processes:
nice
: The priority of the process.rt_priority
: The real-time priority of the process.policy
: The scheduling policy of the process.sched_latency
: The maximum time a process can be delayed before it is scheduled.sched_min_granularity
: The minimum time between schedulings of the process.sched_wakeup_granularity
: The time between schedulings of the process when it is woken up.