So typically: swap off on servers. Do they have a server story?
Edit: I think that the use of ZFS for your /tmp would solve this. You get Error Corrected memory writing to an check-summed file system.
Second, the binaries of your processes are mapped in as named pages (because they come from the ELF file).
Named pages are generell not understood as "used" memory because they can be evicted and reclaimed, but if you have a service with a 150MB binary running, those 150MB of seemingly "free" memory are absolutely crucial for performance.
Running out of this 150MB of disk cache will result in the machine using up all I/O capacities to re-fetch the ELF from disk and likely become unresponsive. Having swap does significantly delay this lock-up by allowing anonymous pages to be evicted, so the same memory pressure will cause less stalls.
So until the OOM management on Linux gets fixed, you need swap.
Its less a bug but an understood problem, and there aren't any good solutions around yet.
> It uses journaling for guaranteeing write atomicity by default, which effectively halves the write speed.
That seems like a poor fit for swap IMO.
https://www.kernel.org/doc/html/latest/admin-guide/device-ma... says,
> There’s an alternate mode of operation where dm-integrity uses a bitmap instead of a journal. If a bit in the bitmap is 1, the corresponding region’s data and integrity tags are not synchronized - if the machine crashes, the unsynchronized regions will be recalculated. The bitmap mode is faster than the journal mode, because we don’t have to write the data twice, but it is also less reliable, because if data corruption happens when the machine crashes, it may not be detected.
It's not clear to me if that would be okay for swap (as long as you don't hibernate, maybe) or if it's sufficiently protected from corruption.
Although if you do swap on a server (and you should), the swap needs to be on a raid, otherwise your server will crash on a disk error.
Swap on a server is not meant for handling low memory issues, instead there's tons of data on a server that's almost never used, so instead swap that out and make more room for cache.