With tuning that means you can also try to set it via vm.swappiness kernel parameter. For example.
Comment on Why is my home server using so much RAM for cache + buffer?
notabot@piefed.social 6 days ago
Seeing high cache and buffer numbers is usually a good sign, as it means the system is making full use of the memory you have. It’ll automatically deallocate it if something actually needs the memory, but until then it’s using it to store data you might need.
Swap’s a funny one, and whilst you can tune it to an astonishing degree, the decisions the kernel makes aren’t always what you’d want. With this little actual memory usage, compared to the installed RAM, you might be able to run without swap at all, unless you want something like hibernate. If you want to test that, you can run (as root) swapoff -a, which should disable all swap devices, pushing needed pages back in to RAM, but only until you reboot. If it’s stable, you can consider removing the swap partition(s) later.
melroy@kbin.melroy.org 6 days ago
A9nWGzYt@lemmy.dbzer0.com 6 days ago
I agree with you that my server specs are a little bit excessive for my usual workload. I have disabled swap in the past with
swapoff -aand removed the partition from/etc/fstabunder a similar usage, and no issues were observed.I am just leaving it there now for the rare instance when I run the occasional lightweight local LLM model (on CPU) for light tasks such as spell checking, which might need some RAM and I don’t risk crashing due to OOM issues.
However, I still want to understand what is happening here to learn a little bit about my system. My intuition can be wrong here, but I find it strange that my laptop with similar specs and the same OS (but reasonably distinct workloads, to be fair) almost never swaps nor reaches those ridiculous levels of buffer + cache usage, so I think I might find one “offender” container to blame.
noahm@lemmy.world 6 days ago
Very basically, what’s happening is that every file that is read (including the binaries and libraries that make up the services you run, etc) is loaded into memory and stays there until that memory needs to be reclaimed for something else. It’s a good thing. It means that the next time that file is needed, it can be accessed directly in RAM rather than reaching out to the filesystem.
notabot@piefed.social 6 days ago
The cache usage being higher on a server than a laptop seems fairly likely as more disk accesses are occurring. When data is loaded from disk, the linux kernel will keep it in memory even after the original requester is done with it, on the principal that it might need it again. This is the cache you’re seeing. If the kernel detects high memory utilisation it will free cache pages before anything else, so you actually want to see near 100% memory utilisation all the time, as it means fewer accesses to disk.
The swap usage is harder to diagnose without more detailed diagnostic work, but you can see from the graph you posted that, even what swap is being used, you have a little free memory. This may well be the kernel preemptively moving little used memory pages to the swap cache so tgat they can be evicted from memory quickly if needed. You could investigate thus by adjusting the ‘swapiness’ value closer to 0, to see if that delays the swap usage and reduces the peak.