Understanding the purpose of cgroups

Back in the days of single-core CPUs, resource management wasn't such a big deal. Servers generally came with anywhere from one to four single-core CPUs installed, so they were already limited in the number of services that could run simultaneously. All we needed for resource management back then were simple tools such as nice, renice, and ulimit.

Nowadays, it's an entirely different story. Servers now come with one or more multi-core CPUs and gobs of memory. (The current king-of-the-hill server CPU is the AMD Epyc, which now comes in a 64-core variety that can run 128 simultaneous threads. Yeah, that's enough to make us hard-core geeks salivate.) Although it might seem counter-intuitive, resource management on these beasts is more important than it was on the old systems. That's because one server can now run multiple services, multiple virtual machines, multiple containers, and multiple user accounts all at the same time...