Disk Backlog slowing down server

[neofusion]

If you’re on 24.04.0 it could be related to this:

Dragonfish swap usage/high memory/memory leak issues

After deeper digging into the problem, it looks to me caused not only by increased ARC size, reduction which according to some people may not fix the problem, but also by Linux kernel update to 6.6, which enabled previously disabled Multi-Gen LRU code, written in a way that assumes that memory can not be significantly used by anything other than page cache (which does not include ZFS). My early tests show that disabling it as it was in Cobia with echo n >/sys/kernel/mm/lru_gen/enabled may fix t…