Sum total of memory assigned to all users

[Biglebowski]

Hi,

Is there an easy way if getting this other than lvectl list-user | awk etc ?

Apparently 20% - 30% of physical should be reserved for the system. As theres no practical way of ringfencing this, then presumably the sum total of user account ram shouldn't really exceed 70-80% without the risk of oom on busy systems?

Thanks

[bogdan.sh]

Hi,

The easiest way to use the 'free -m' and take the available column into consideration. In Linux you will always see 80-90% 'used' ram, but typically it is taken by cache which can be removed in case of memory is needed by other processes. Or reused as a shared space.

You would love this site which explains it in simple wording: https://www.linuxatemyram.com/

[Biglebowski]

Thanks Bogdan, very useful.

Any thoughts on the other part of my question please?

eg if Ive got a server with 100GB ram and i expect the system will use 40gb of it.
I can presumably then safely allocate 60Gb in total to all user accounts combined.

However the chance of all users using all of their allocation simultaneously and thereby causing a system level oom is unlikely.

So presumably in most cases ram is oversubscribed. The question is by how much. Is it common practice to oversubscribe twice or three times or more? And then just shed users ooming more often than others onto another server as problems occur?

I've got a similar question re cpu limit allocations however I'll open another thread,

[bogdan.sh]

Dude, this should totally work! But if you’re talking about the system itself, it’ll only need a few GBs of RAM. The Apache/PHP/MySQL stuff should be called user-related services per your wording

After running the services for a bit, you can check how things are doing and balance the RAM usage. Personally, I’d grab as much RAM as I can and tweak MySQL to use it since that’s usually the biggest memory hog and can be a bottleneck. 100Gb (128!) ram is pretty decent setup.