Windows 10 VM So Slow when cpu type is host

[jic5760]

Windows 10 VM is too slow on Proxmox.
Even dragging the window is too slow.

I have two VMs with similar settings.
But the second VM is not slow.
The difference is, slow VM's cpu type is host , while fast VM's cpu type is qemu64 .

VM1:

agent: 1
balloon: 0
bios: ovmf
boot: order=scsi0;ide2;net0;ide0
cores: 16
cpu: host,flags=+aes
efidisk0: nvme-datastore-01:vm-12211-disk-0,efitype=4m,pre-enrolled-keys=1,size=4M
ide0: none,media=cdrom
ide2: none,media=cdrom
machine: q35
memory: 40960
meta: creation-qemu=7.1.0,ctime=1676011167
name: vm-01
net0: ...
numa: 0
ostype: win10
scsi0: nvme-datastore-01:vm-12211-disk-0,cache=writeback,discard=on,iothread=1,size=128G,ssd=1
scsihw: virtio-scsi-single
smbios1: ...
sockets: 1
tpmstate0: pve-rack01-node05-datastore-01:vm-12211-disk-1,size=4M,version=v2.0
vmgenid: ...

VM2:

agent: 1
bios: ovmf
boot: order=scsi0;ide2;net0;ide0
cores: 8
cpu: qemu64,flags=+aes
efidisk0: local-lvm:vm-91001-disk-0,efitype=4m,pre-enrolled-keys=1,size=4M
hotplug: disk,network,usb,cpu
ide0: none,media=cdrom
ide2: none,media=cdrom
machine: q35
memory: 20480
meta: creation-qemu=7.1.0,ctime=1677130886
name: vm-02
net0: ...
numa: 0
ostype: win10
parent: clean_220223
scsi0: nvme-datastore-01:vm-91001-disk-0,backup=0,cache=writethrough,discard=on,iothread=1,size=100G,ssd=1
scsihw: virtio-scsi-single
smbios1: ...
sockets: 1
tpmstate0: local-lvm:vm-91001-disk-1,size=4M,version=v2.0
vmgenid: ...

https://forum.proxmox.com/threads/my-windows-vm-is-very-slow.119271/#post-517435
In this post, it is said that the slow speed was improved after setting the cpu type to host.
But i rather host is slower.
Since vm-01 requires nested virtualization, I set it as host.

 

[nunner]

Hi,

generally, setting "host" as the CPU type should be the fastest option. We have a guide on Windows 10 best practices here [1], did you look into that already? Can you confirm that the performance problems actually stem form the CPU, and not some other factors? (like the ones quoted in the post that you linked)

[1] https://pve.proxmox.com/wiki/Windows_10_guest_best_practices

 

[jic5760]

I have already read and followed that article.

Both VMs have the same Windows Revision and same virtio drivers installed.

As you can see in the configuration file, virtio scsi single is used.

 

[ronaldhix]

In another proxmox forum post (https://forum.proxmox.com/threads/windows-10-debian-vms-slow.109072/post-468972), mira suggests using the default cpu setting, which for me is usually kvm64 on a windows 10 vm. Switching from host to kvm64 made a dramatic difference in my case (Intel Xeon E5-2690v2). I still need to try it on my other windows 10 vm with gpu passthrough.

 

[SamFredo]

I've had the same experience as well.
Simulated CPU performs a magnitude faster than Host.

Yet, it's not clear to me why/how this could happen. But I've learnt a new thing the hard way.

 

[toomanylogins]

Turn mitigations off if you can ie pve is not connected to internet. Also are both disks on the same storage ? WIn10 is faster with lvm-yhin than qcow2.