MEMORY PROXMOX 9.0

[Felipe Aleixo]

Hi everyone,
some time ago I updated my Proxmox host and noticed a strange behavior related to memory usage.


Even when using VirtIO (balloon/IO), the host shows the memory as almost fully used, while inside the VM the memory usage does not exceed 30%.


Has anyone experienced this issue or knows how to fix this memory behavior?


Would upgrading to Proxmox 9.1 solve this memory reporting/management issue?

 

[Impact]

It can be normal. Depends on a lot of things. Please share qm config 4140.

 

[aaron]

https://pve.proxmox.com/wiki/Upgrade_from_8_to_9#VM_Memory_Consumption_Shown_is_Higher

If this is a Windows machine, make sure that the Balloon Device is enabled (Hardware -> Memory, in the advanced part) and that the driver for that device as well as the "Balloon Service" is installed and running. Only then can Proxmox VE know the usage from within the VM.

And while I am at it, you should install the VirtIO drivers and the guest agent. https://pve.proxmox.com/wiki/Windows_VirtIO_Drivers
Then you can also enable the guest agent in the Options panels of the VM.

 

[Lithilion]

It can be normal. Depends on a lot of things. Please share qm config 4140.

I have the same behaviour. Do you know of a documentation or known limitations link for that?

 

[Felipe Aleixo]

I understand. I have another VM that I installed recently, and everything seems to be configured correctly, including the drivers and the guest agent enabled. However, it still shows the memory as fully used . I’ll try upgrading to version 9.1 to see if this resolves the issue.

 

[aaron]

According to the last screenshot, the ballooning device is disabled.
Memory consumption is not queried via the guest agent, but via the ballooning device, and for Windows, the Balloon Service. Other operating systems handle that communication via the balloon device directly in the kernel (e.g. Linux).

To post a VMs config, run the command qm config XXX on the CLI/Shell of the host and copy and paste the output within [code][/code] tags in the forum. Or use the buttons at the top of the editor (</>) to format the output correctly. That makes it a lot easier to check the config of the VM

 

[Impact]

I have the same behaviour. Do you know of a documentation or known limitations link for that?

No but it depends on OS, ballooning, PCI passthrough, etc. For example linux guests usually report cache as used memory. Windows usually reports what you see in the Task Manager if configured properly but it sometimes zeroes all the memory (check with RAMMap) making it show as fully used. With PVE 9 you now also have information about Host Memory Usage. Many variables. Much potential for confusion.

 

[Lithilion]

Is there a known solution for an OPNsense? (FreeBSD)

 

[jsterr]

No but it depends on OS, ballooning, PCI passthrough, etc. For example linux guests usually report cache as used memory. Windows usually reports what you see in the Task Manager if configured properly but it sometimes zeroes all the memory (check with RAMMap) making it show as fully used. With PVE 9 you now also have information about Host Memory Usage. Many variables. Much potential for confusion.

Hello Impact. Do you know if Balloon = 1 is ok, when memory max and min memory have the same value (so no actual "ballooning" is done) regarding PCI-PT?

• https://pve.proxmox.com/wiki/Dynamic_Memory_Management#Ballooning says Ballooning should not be used, but it does not say if this means balloon = 0 or if balloon = 1 is ok when Memory-Values are the same (memory = min-memory).
  
  
• https://forum.proxmox.com/threads/pcie-passthrough-breaks-display-of-memory-usage.142444/ this says, thats PCI-PT Devices like GPUs always allocate 100% of its ram, is this true?

So basically it does not matter, because aslong as PCI-PT is used, each VM uses 100% of its ram no matter if balloon = 1 or balloon = 0. Which is typically used to report correct memory values to pve via guest-os?

 

[leesteken]

PCI(e) passthrough requires all VM memory (which can be a little over 100%) to be pinned into actual host RAM (due to device DMA). Ballooning cannot give memory back to the Proxmox host, but the ballooning device can (for some operating systems) report on how much memory the operating system inside the VM says/thinks it actually uses.

 

[jsterr]

PCI(e) passthrough requires all VM memory (which can be a little over 100%) to be pinned into actual host RAM (due to device DMA). Ballooning cannot give memory back to the Proxmox host, but the ballooning device can (for some operating systems) report on how much memory the operating system inside the VM says/thinks it actually uses.

Thanks! Pinned to actual host-ram means the vm also uses 100% on vm-summary? Or is it "only" reserved on host summary, so vm could theoretically only show 50% memory usage, although it reserves 100% on hypervisor-level?

 

[leesteken]

Thanks! Pinned to actual host-ram means the vm also uses 100% on vm-summary? Or is it "only" reserved on host summary, so vm could theoretically only show 50% memory usage, although it reserves 100% on hypervisor-level?

It depends, and it depends what you look at in the Proxmox web GUI. Total and Host Memory Usage are now at least 100% in the graphs for VMs with passthrough. The Used (and the Memory usage bar at the top) depends on what the ballooning driver reports, which depends on the operating system and balloon driver support. Please just try this out for your particular VM yourself, as I cannot give guarantees one way or the other.

https://pve.proxmox.com/wiki/Upgrade_from_8_to_9#VM_Memory_Consumption_Shown_is_Higher