Mastering Linux Kernel Development

Computing priorities and time slices under CFS

Priorities are assigned based on how long the process is waiting, how long the process ran, the process's historical behavior, and its nice value. Normally, schedulers engage complex algorithms to end up with the next best process to run.

In computing the timeslice every process gets, CFS not just relies on the nice value of the process but also looks at the load weight of the process. For every jump in the nice value of a process by 1, there will be a 10% reduction in the CPU timeslice, and for every decrease in the nice value by 1, there will be a 10% addition in the CPU timeslice, indicating that nice values are multiplicative by a 10% change for every jump. To compute the load weight for ...