It's important to realize that the Linux kernel does not have just one algorithm that implements CPU scheduling; the fact is, the POSIX standard specifies a minimal three scheduling policies (algorithms, in effect) that a POSIX-compliant OS must adhere to. Linux goes above and beyond, implementing these three as well as more, with a powerful design called scheduling classes (more on this in the Understanding modular scheduling classes section later in this chapter).
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Again, information on the POSIX scheduling policies on Linux (and more) is covered in more detail in my earlier book, Hands-On System Programming with Linux, published by Packt in October 2018.Â
For now, let's just briefly summarize the POSIX scheduling policies and what effect they have in the following table:
| Scheduling policy | Key points | Priority scale |
|
SCHED_OTHER or  SCHED_NORMAL |
Always the default; threads with this policy are non... |
