High Memory Usage On VM With PCI Passthrough

[trademarkej]

I recently installed an Intel Arc A380 into my Proxmox 8.2.2 node to perform transcoding tasks on a VM running Ubuntu 24.04 LTS with PCI passthrough verified as working.

Previously the VM used between between 6-12GB of RAM but the mere act of adding the PCI device shows it's now using ~93% of available RAM. I have tested increasing the VM to 24, 32 and 64GB of RAM and regardless Proxmox reports the VM is using ~93% of it's available RAM. If I remove the PCI devices but leave all other settings the same, the memory usage drops down to the previously acceptable range. Is this normal behavior or am I missing something?

agent: enabled=1
balloon: 0
boot: c
bootdisk: scsi0
ciuser: ubuntu
cores: 4
hostpci0: 0000:09:00,pcie=1
hostpci1: 0000:0a:00,pcie=1
ide2: local-lvm:vm-235-cloudinit,media=cdrom,size=4M
ipconfig0: ip=##.##.##.##/24,gw=##.##.##.##
machine: q35
memory: 1638
name: rke2-agent-02
net0: virtio=D2:89:16:D4:38:57,bridge=vmbr0
numa: 0
ostype: l26
scsi0: local-lvm:vm-235-disk-0,discard=on,size=20992M,ssd=1
scsi1: local-lvm:vm-235-disk-1,discard=on,size=2G,ssd=1
scsihw: virtio-scsi-pci
serial0: socket
sockets: 1
vga: serial0

 

[leesteken]

Because PCI(e) devices can de Direct Memory Access at any time, all VM memory must be pinned into actual host RAM when using PCI(e) passthrough. So this is normal and the VM cannot use less than the chosen amount of memory.

 

[trademarkej]

Because PCI(e) devices can de Direct Memory Access at any time, all VM memory must be pinned into actual host RAM when using PCI(e) passthrough. So this is normal and the VM cannot use less than the chosen amount of memory.

Ok good to know. Thanks for your quick response!