Info VM Ram Usage

[Dexter23]

Question about VM RAM usage: Hi everyone, I wanted to understand why in Proxmox, in the "Summary" tab of the VMs, I always see RAM usage almost at the maximum, while if I check the RAM usage within the operating system, it is much less. I'll provide some screenshots:


Thanks.

 

[leesteken]

I expect that these threads answer your question about filesystem cache and memory usage (since it is asked every week): https://forum.proxmox.com/search/71...t=post&c[child_nodes]=1&c[nodes][0]=16&o=date

 

[Dexter23]

Hi
So is there a way to see in the summary tub the effective ram usage? or it's normal this situation?

 

[leesteken]

So is there a way to see in the summary tub the effective ram usage? or it's normal this situation?

It is showing the actual memory usage. The filesystem cache (orange in your screenshot) is using memory inside the VM. Why is this not normal? Why would you want to hide this? That memory cannot be used by Proxmox or other VMs, so it is really in use. Maybe read some of the threads or search for yourself for more discussion about this.

EDIT: What do you think is the "real memory used"? Filesystem cache is not magic, it needs real memory. Maybe someone else here can explain it better (like the people in all the other threads about this).

EDIT2: Please read about filesystem cache or read other threads about this that already explain all of this...

 

[Dexter23]

Basically because i monitor proxmox with zabbix with the template "Proxmox VE by HTTP" and he read the memory reserver by proxmox for that vm and not the real memory used by the guest operating system.

 

[B.Otto]

There is no way for the hypervisor to see actual RAM usage 'from outside'. All the hypervisor really sees is that ~14.85GB of the assigned virtual RAM has been touched by the operating system inside the VM. It cannot distinguish, which memory blocks are used for actual processes and which are used for system caching.

You need some way to see the RAM usage 'from inside', in your case likely by installing a Zabbix client inside the VM, or by configuring something like SNMP.

I do wanna note that the RAM number displayed in Proxmox is not actually wrong, it is what the VM is actually using. This is important, because it is the amount of Host RAM you actually need to provide to the VM, e.g. the sum of all 'Proxmox-displayed RAM' needs to be lower than the total physical RAM in your Proxmox machine.

 

[Dexter23]

There is no way for the hypervisor to see actual RAM usage 'from outside'. All the hypervisor really sees is that ~14.85GB of the assigned virtual RAM has been touched by the operating system inside the VM. It cannot distinguish, which memory blocks are used for actual processes and which are used for system caching.

You need some way to see the RAM usage 'from inside', in your case likely by installing a Zabbix client inside the VM, or by configuring something like SNMP.

I do wanna note that the RAM number displayed in Proxmox is not actually wrong, it is what the VM is actually using. This is important, because it is the amount of Host RAM you actually need to provide to the VM, e.g. the sum of all 'Proxmox-displayed RAM' needs to be lower than the total physical RAM in your Proxmox machine.

Hi otto
But this particula vm before has 8gb of ram assigned and proxmox "summary tab" the used ram is 95%-100% now i have assigned 16gb ram and is also take 95% of ram is that normal?

 

[gfngfn256]

But this particula vm before has 8gb of ram assigned and proxmox "summary tab" the used ram is 95%-100% now i have assigned 16gb ram and is also take 95% of ram is that normal?

Also perfectly normal behavior. Your VM is assigning RAM from what is available to it, so by increasing the VM RAM in Proxmox, the VM now has even more memory to "play" with. Your VM's filesystem cache has probably doubled now etc..

 

[Dexter23]

Ok so what should I base myself on when I assign the RAM to a virtual machine on the one that proxmox uses or on the one that the guest system uses?

 

[gfngfn256]

As a rule of thumb - the RAM you "hand-out" to the VM is potentially going to be used completely by the VM. This is also dependent on what OS the VM is running & how you have set up that running OS . There is something called balooning which (in certain circumstances) will actually share back the memory with the host. You may want to read up on the subject.

The easiest way to handle RAM allocation management, test the VM with various amounts of RAM (start small), & once you discover at what level of RAM the VM is happily chugging on - stick with that.