LXC eats all RAM but not listen in htop

[userarrayuser]

Hello,

I have a little problem to find what eats up memory inside LXC.
I created (on latest PVE) an Almalinux9 LC (starting with 1G RAM then I changed to 2G) and only installed rsync (to use as remote for a backup software with root) and nfs-utils (for attach nfs destination folder). finally EPEL/htop for diagnostics.
Everything works fine, except high RAM usage (when I do the same in a VM, everything is OK with RAM usage, only in LXC works strange)
When I run htop under LXC it shows the right RAM usage but there is no sign of RAM usage in process list so I read about it then I tried to find in host's htop, but with no luck, it's looks like a ghost RAM usage.
When add more RAM it's works OK for a while, then jump up to 95% usage, it looks like something is stucked. After reboot the same happens.

Does anyone have an idea what I should try?

Thank You

 

[UdoB]

Does anyone have an idea what I should try?

Not sure. I just have a very generic hint: https://www.linuxatemyram.com/

 

[waltar]

Use of filesystem cache which is the normal desired behavior (to eat all free mem and release in case of request by any application) to any linux kernel ?!

 

[userarrayuser]

Not sure. I just have a very generic hint: https://www.linuxatemyram.com/

Use of filesystem cache which is the normal desired behavior (to eat all free mem and release in case of request by any application) to any linux kernel ?!

I'm aware RAM utilizing is a normal thing but why VM uses fraction of RAM vs CT? It should be the opposite.
Plus why I can't find what consumes this much RAM?