[singron]

A specific process can use mlockall to keep all its mapped memory resident and prevent swapping or page cache eviction. That's what earlyoom does so that it can stay responsive when memory gets low. It's unfortunately underutilized in other infrastructure. It's also all-or-nothing: everything stays resident until it's munlocked regardless of how frequently it's used.

I had hoped that something like Linux Pressure Stall Information (PSI) would become more useful for low-memory scenarios. E.g. you could put critical processes in a cgroup that could rate-limit swap-outs/evictions so that it was always responsive. There are some cgroup knobs that affect reclamation, but you need a really good guess about how much memory something needs, which makes it hard to use.

https://docs.kernel.org/accounting/psi.html