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In defence of swap: common misconceptions

tl;dr: Having swap is a reasonably important part of a well functioning system. Without it, sane memory management becomes harder to achieve.

This is a statement that I still see being batted around with relative frequency in recent years, and I've had many discussions with colleagues, friends, and industry peers to help them understand why swap is still a useful concept on modern computers with significantly more physical memory available than in the past. While these are either trivial to dispel, or discussion around them has become more nuanced in recent years, the myth of "useless" swap is much more grounded in heuristics and arcana rather than something that can be explained by simple analogy, and requires somewhat more understanding of memory management to reason about. That said, this is still too late to be really useful – the OOM killer is only invoked at moments of severe starvation, and relying on this method for such behaviour would be better replaced with more opportunistic killing of processes as memory contention is reached in the first place.

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