In Chap. 1, we looked at some of the current research in operating system structure. In this and subsequent chapters, we will look at more narrowly focused research, starting with processes. As will become clear in time, some subjects are much more settled than others. Most of the research tends to be on the new topics, rather than ones that have been around for decades.

The concept of a process is an example of something that is fairly well settled. Almost every system has some notion of a process as a container for grouping together related resources such as an address space, threads, open files, protection permissions, and so on. Different systems do the grouping slightly differently, but these are just engineering differences. The basic idea is not very controversial any more, and there is little new research on the subject of processes.

Threads are a newer idea than processes, but they, too, have been chewed over quite a bit. Still, the occasional paper about threads appears from time to time, for example, about core-aware thread management (Qin et al., 2019), or on how well modern operating systems like Linux scale with many threads and many cores (Boyd-Wickizer, 2010).

Additionally, there is a lot of work trying to prove things do not break in the presence of concurrency, for instance in file systems (Chajed et al., 2019; and Zou et al., 2019) and other services (Setty et al., 2018; and Li et al., 2019). This is important work as researchers have shown that concurrency bugs are unfortunately extremely common (Li et al., 2019). As we have seen, locking is not just hard, but also expensive and operating systems have adopted RCU to avoid locking altogether (McKenney et al., 2013).

An active research area deals with recording and replaying a process’ execution (Viennot et al., 2013). Replaying helps developers track down hard-to-find bugs and security experts to investigate incidents.

Speaking of security, a major event in 2018 was the disclosure of a series of very serious security vulnerabilities in modern CPUs. They required changes everywhere: hardware, firmware, operating system, and even applications. For this chapter, the scheduling implications are especially relevant. For instance, Windows adopted a scheduling algorithm to prevent code in different security domains from sharing the same processor core (Microsoft, 2018).

Scheduling (both uniprocessor and multiprocessor) in general is still a topic near and dear to the heart of some researchers. Some topics being researched include scheduling in clusters for deep learning (Xiao et al., 2018), scheduling for microservices (Sriraman, 2018), and schedulability (Yang et al., 2018). All in all, processes, threads, and scheduling are not hot topics for research as they once were. The research has moved on to topics like power management, virtualization, clouds, and security.