Slightly increased load on disk or CPU causes freezes on USB IO devices

[jd_pve]

I'm using GPU pass through windows 11 machine as my work machine, but with almost any increased load (opening Bambu studio f.e.) on this VM, the USB IO devices starts to lag (mouse movement becomes patchy, audio devices start to crackle as if connecting and disconnecting). I've started to notice this problem about year ago, after updating from V 7.x to V 8.3. VMs were not migrated with this process and were created new. I might have had some configuration on that machine, that made it work fine, that I've done according few of those standard tutorials to making a gaming VM (currently not used for gaming).


I'm have another hard drive in the same machine, that I've tried booting bare metal windows 11 to eliminate the possibility of faulty hardware.

My hardware:
CPU: 13th Gen Intel(R) Core(TM) i9-13900K (1 Socket)
RAM: 128GB of DDDR4
Hard drives :

• 2TB NVME Samsung 980 EVO (This is what VMs are on)
• 2x SATA Seagate IronWolf 4TB CMR
• 1x Seagate Exos X20 20TB SATA
• 1x TB 1TB NVME Samsung 980
• 1x 1TB NVME Samsung 960 EVO (This is what I have the baremetal on)

GPU: MSI RTX 4080OC
Motherboard: ROG STRIX Z790-A GAMING WIFI D4

IO delay rarely gets above 0.5%

All the VMs currently use 20 cores (Which in my understanding leaves 12 to proxmox, if my understanding is correct and single core in GUI means a single thread)

Then I have PBS server connected to it, which is dedicated machine, running backups once every 24h.

These are the VM settings:

agent: 1
balloon: 0
bios: ovmf
boot: order=scsi0;ide0;ide2;net0
cores: 12
cpu: host
efidisk0: local-lvm:vm-104-disk-0,efitype=4m,pre-enrolled-keys=1,size=4M
hostpci0: 0000:01:00,pcie=1,x-vga=1
ide0: local:iso/virtio-win-0.1.266.iso,media=cdrom,size=707456K
ide2: local:iso/Win11_24H2_English_x64-auto.iso,media=cdrom,size=5669090K
machine: pc-q35-9.0
memory: 32768
meta: creation-qemu=9.0.2,ctime=1735404413
name: main
net0: virtio=XXXXXXXX,bridge=vmbr0,firewall=1
numa: 0
onboot: 1
ostype: win11
scsi0: local-lvm:vm-104-disk-1,cache=writeback,iothread=1,size=512G,ssd=1
scsi1: /dev/disk/by-id/XXXXXXF,backup=0,size=18627G
scsihw: virtio-scsi-single
smbios1: uuid=XXXXXXXXX
sockets: 1
tpmstate0: local-lvm:vm-104-disk-2,size=4M,version=v2.0
usb0: host=1-13.1,usb3=1
usb1: host=1-13.2,usb3=1
usb2: host=1-10.4,usb3=1
usb3: host=1-8,usb3=1
usb4: host=1-1,usb3=1
vga: virtio
vmgenid: XXXXXXXX

I'm finding similar issues on other VMs, where remote desktoping into them leads to horrible performance, with them having even less load and similar resources. As stated, I didn't have these problems earlier, so it's most likely a faulty setting somewhere, but I wasn't able to find a thread with similar problems, so I'm coming here for advice.

Further testing showed highest interrupt to process latency under normal use to be 5.6ms and highest DPC to be 12ms.

I have tried to troubleshoot this further with bare metal, where I've found out, that DPC latency is high even on that machine, it's just not that noticeable. Further research indicated, that this is an issue related to 13th gen of Intel CPUs.

 

[jd_pve]

Even though it's not the complete explanation, I'm getting high DPC even on baremetal. Further research indicates, that this is one of the issues with 13th gen of Intel chips.