It does not need it at all. I’ve run a million+ hosts with no swap. You need to be really disciplined about memory allocations (us cgroups) and ok with what happens if you run out (something in that cgroup dies). But there is no “housekeeping “ that requires it.

I have tried to forego swap because I had hoped that it would avoid swap thrashing, where performance goes into the toilet; I'd rather a process was killed but I could still access the system, than be unable to login to it.

But I've found that even with no/little swap, the system can get into high memory pressure situations (even easier because it can't swap out unused pages of libraries and the like), and still go into a sort of thrashing state even though it isn't swapping.

My main workstation is a Dell XPS15 with 32GB of RAM and I had 8GB of swap on it. About every month the system load would skyrocket even though it had plenty of mem+cache+swap available. If I killed off my browser and slack, load would return to normal, and I could use the system for a few more days or a week before it happened again.

I struggled with this for a year or more, before (for reason's I don't remember), I added another 8GB of swap. Within the next day 80% of the extra swap was used right up. I decided to swapoff that new file and create a 64GB swapfile and just see what happened. It got to around 20-30GB IIRC before it leveled off. And, more importantly, over the next 100+ days I never had that thrashing happen again.

That was with Ubuntu 22.04. I just recently (May-ish) switched over to a NixOS setup with 64GB of swapfile, and it's been very stable.

It does give you some more RAM for free, as Linux can park allocated but rarely accessed memory and use the freed space for other purposes.

Any tips on measuring the impact of not having swap? I never use it on my machines for similar reasons.