RAM reporting by Proxmox interface is incorrect

[balter]

Hi All,

I have 3 Ubuntu Server 18.04.3LTS virtual machines running in Proxmox 6.0-4. Everything runs perfectly however the RAM usage that is reported by each individual VM appears incorrect when compared to the htop output from within the VM... This is the case for all VMs, however the Proxmox node reports the same RAM usage in the dashboard as it does in htop. This is the only one that seems correct.

When setting up the VMs, I set the Memory and Minimum memory to the same value with ballooning device checked.

I have attached screenshots comparing the Proxmox dashboard with the htop output.

Thanks in advance!

 

[fabian]

from the outside (hypervisor view), used memory is used memory no matter for what it is used. from the inside (guest view), some usage types such as caches might not be counted as really used, even though they currently take up memory (e.g., for linux check https://www.linuxatemyram.com/ for a detailed explanation).

 

[balter]

Thanks Fabian, that makes sense but you’ll notice there is several GB difference. Could that really be used by cache? I’m certainly no pro when it comes to Linux, but that seems excessive...

Tim

 

[fabian]

Thanks Fabian, that makes sense but you’ll notice there is several GB difference. Could that really be used by cache? I’m certainly no pro when it comes to Linux, but that seems excessive...

Tim

yes. Linux will use memory that would otherwise be unused for caching since it increases performance "for free"

 

[LnxBil]

Thanks Fabian, that makes sense but you’ll notice there is several GB difference. Could that really be used by cache? I’m certainly no pro when it comes to Linux, but that seems excessive...

You have windows to blame for that. On windows, free memory includes caches. On Linux however, caches are explicitly not free and separately accounted for.