[gnyman]

Note though that if you don't have swap now, and enable it, you introduce the risk of thrashing [1]

If you have swap already it doesn't matter, but I've encountered enough thrashing that I now disable swap on almost all servers I work with.

It's rare but when it happens the server usually becomes completely unresponsive, so you have to hard reset it. I'd rather that the application trying to use too much memory is killed by the oom manager and I can ssh in and fix that.

[1] https://docs.redhat.com/en/documentation/red_hat_enterprise_...

[mnw21cam]

That's not true. Without swap, you already have the risk of thrashing. This is because Linux views all segments of code which your processes are running as clean and evictable from the cache, and therefore basically equivalent to swap, even when you have no swap. Under low-memory conditions, Linux will happily evict all clean pages, including the ones that the next process to be scheduled needs to execute from, causing thrashing. You can still get an unresponsive server under low memory conditions due to thrashing with no swap.

Setting swappiness to zero doesn't fix this. Disabling swap doesn't fix this. Disabling overcommit does fix this, but that might have unacceptable disadvantages if some of the processes you are running allocate much more RAM than they use. Installing earlyoom to prevent real low memory conditions does fix this, and is probably the best solution.

[k_bx]

Disabling swap on servers is de-facto standard for serious deployments.

The swap story needs a serious upgrade. I think /tmp in memory is a great idea, but I also think that particular /tmp needs a swap support (ideally with compression, ZSWAP), but not the main system.

[throw0101c]

> Disabling swap on servers is de-facto standard for serious deployments.

I guess I have not been deploying seriously over the last couple of decades because the (hardware) systems that I deploy all had some swap, even if it was only a file.

[ravetcofx]

Swap always seemed more meant for desktop use. Servers you need to give the real memory expected of the application stack.

[bmacho]

So the ideal behaviour would be:

  - for most processes no SWAP
  - for tmpfs, use RAM until a quota
  - for tmpfs, start using a swapfile above that quota

ChatGPT doesn't think it is achievable, though it thinks cgroup2 can achieve something similar.

[baq]

This is why I’m running with overcommit 2 and a different ratio per server purpose.

…though I’m not sure why we have to think about this in 2025 at all.

[worthless-trash]

I'm assuming that you monitor the service closely for OOM then adjust with demand ?