Heavy stuttering when running multiple VMs on 5.2-1

[patrik2991_]

Hi!
First of all

Spoiler: My PC specifications

Asrock Z170 Extreme6+
Intel Core i7 6700K
32GB G.Skill RAM
Nvidia Geforce GTX1060
Nvidia Geforce GTX1050Ti
Kingston UV500 240GB SSD disks

So i run Proxmox 5.0-30 on this rig, the hypervisor use the igpu, and the 2 VMs use 1-1 of the GPUs.
Everyting works flawlessly, but i have decided to upgrade to Proxmox 5.2-1, i don't like updates so i did a clean install on another SSD set, and set everything the same as my old setup.
Which means:
1. I installed Proxmox on an ssd
2. Created 2 seperate lvm-thin storage on 2 seperate SSDs (1 for each VM)
3. Followed the PCI Passthrough wiki

Spoiler: VM101.conf

balloon: 0
bios: ovmf
boot: cdn
bootdisk: virtio1
cores: 4
cpu: host
keyboard: hu
machine: q35
memory: 15360
name: Patrik-VPC
net0: e1000=6E:19:CE:88:3F:E5,bridge=vmbr0
numa: 0
onboot: 1
ostype: win10
scsihw: virtio-scsi-pci
smbios1: uuid=b1c0b65d-e647-425f-814e-d93595bf4c2b
sockets: 1
usb0: host=1-3
usb1: host=1-4
usb2: host=1-10
usb3: host=1-11
hostpci0: 01:00,pcie=1,x-vga=on
efidisk0: SATA_SSD1:vm-101-disk-1,size=128K
virtio1: SATA_SSD1:vm-101-disk-2,cache=writeback,size=200G

Spoiler: VM102.conf

balloon: 0
bios: ovmf
boot: cdn
bootdisk: virtio1
cores: 4
cpu: host
keyboard: hu
machine: q35
memory: 15360
name: Patrik-VPC2
net0: e1000=D6:E9:A7:41:2F:17,bridge=vmbr0
numa: 0
onboot: 1
ostype: win10
scsihw: virtio-scsi-pci
smbios1: uuid=bd0cd2fd-dbf3-4d08-a16d-3d88b1aee577
sockets: 1
usb0: host=1-1.4
usb1: host=1-2
usb2: host=1-6
usb3: host=1-7
usb4: host=1-7.4
hostpci0: 02:00,pcie=1,x-vga=on
efidisk0: SATA_SSD2:vm-102-disk-1,size=4M
virtio1: SATA_SSD2:vm-102-disk-2,cache=writeback,size=200G

Spoiler: Edit in the grub (updated)

GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on pcie_acs_override=downstream"

Spoiler: blacklist.conf

blacklist nvidia
blacklist nouveau

Spoiler: kvm.conf

options kvm ignore_msrs=1

Spoiler: vfio.conf

options vfio-pci ids=10de:1c03,10de:10f1,10de:1c82,10de:0fb9

Spoiler: modules

vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd

4. Installed Windows 10 with the virtio drivers
5. Installed the latest GPU driver, which runs on the old system, without any problem
6. Applied MSISupported regedit fix on both VMs to get rid of the sound stuttering.

After all these i have a strange problem which i didn't encountered on the old system. If i run the 2 VMs at the same time, it produce heavy stuttering on both VMs (graphics, sound, mouse movement) and if i try some heavy workload it complelty freezes them. If i run only one VM at a time, everything works flawlessly.
Have you got any idea what cause this issue on 5.2-1?

Cause i'm out of ideas i tried this install procedure on the new set of SSDs on 5.0-30 again to check i didn't missed anything, and it works flawlessly!

 

[dorinxev]

It could relate to TONS of things, as there is a bottleneck in storage, network, CPU - it's really hard to troubleshoot without knowing specifically whats going on.

 

[RolandK]

this post is 5 years old

the stuttering is most likely being cause by qemu locking, see https://bugzilla.proxmox.com/show_bug.cgi?id=1453

furthermore, many low-end consumer grade ssd can have very low write speed when there are longer periods of sustained write, that can even worsen the stuttering effect.