Comment on Help with understanding memory usage discrepancy
Shimitar@downonthestreet.eu 1 day ago
You actually WANT to be with low free memory. Provided that most of it is used by cache.
Free memory is a waste, when you could cache stuff for faster access.
That’s how Linux memory management works, and it make sense if you relflect on it. Better cache that page or that file that is used often, since free memory is just wasted. Cache can be freed and memory reclaimed in a fraction of a millisecond when needed.
So don’t bother too much. Unless your SWAP usage is high, don’t bother.
Also consider that Linux kernel will use your swap a bit even if you have lots of cache, because the kernel knows better than you how to improve your performances. Swapping out never used stuff is better than killing cached items.
Again, don’t oberthink memory on Linux, the best alarm is when swap is constantly happening, then yes you need more ram (or to kill that broken process that keeps hogging due to a bug)
a_fancy_kiwi@lemmy.world 1 day ago
This is why I’d like to know what tool shows the most useful number. If I only have 4GB out of 30GB left, is that 26GB difference mostly important processes or mostly closable cache? Like, is htop borked and not showing me useful info or is it saying 8GB of the 26GB used is important showstopping stuff?
rtxn@lemmy.world 1 day ago
The most useful is probably
cat /proc/meminfo. The first couple of lines tell you everything you need to know.MemTotalis the total useful memory.MemFreeis how much memory is not used by anything.Cachedis memory used by various caches, e.g. ZFS. This memory can be reallocated.MemAvailableis how much memory can be allocated, i.e.MemFree + Cached.a_fancy_kiwi@lemmy.world 1 day ago
You’re an angel. I don’t know what the fuck htop is doing showing 8GB in use. For anyone else who comes across this, this is what I have. This makes the situation seem a little more grim. I have ~2GB free, ~28GB in use, and only ~3GB is cache that can be closed. For reference, I’m using ZFS and roughly 27 docker containers. It doesn’t seem like there is much room for future services to selfhost.
rtxn@lemmy.world 1 day ago
You should also look at which processes use the largest amount of memory. ZFS is weird and might allocate its cache memory as “used” instead of “cached”. See here to set its limits: forum.proxmox.com/…/limit-zfs-memory.140803/
Voroxpete@sh.itjust.works 1 day ago
Most of those containers are probably grabbing more memory than they actually need. Consider applying some resource constraints to some of them.
Dozzle is an excellent addition to your docker setup, giving you live performance graphs for all your containers. It can help a lot with fine tuning your setup.