So I somehow got about 20-40% depending on type of load in performance extra CPU throughput with following flags set. This is on top of default host flags.
flags +invtsc;+topoext;+host-cache-info;-hypervisor
It seems for the performance boost HyperV should be left enabled in bcdedit.
The host CPU is a AMD 5600G, and all optional flags in the UI are on default.
There is one issue, all chromium web browsers have instability, the main process doesnt crash, but random stack break's instead on rendering processes, even spamming f12 for dev tools will cause crashes.
If I remove the -hypervisor flag, the crashes go away, likewise if I disable HyperV in bcdedit, the crashes go away. But these also both lose the performance boost, like as removing any of the custom flags removes the performance boost, its quite a delicate combination of flags.
The flags in this thread yield a gain of about 10% without instability, I dont care for live migrations. So I will probably leave at that given, there seems no way forward on the bigger gain, but I welcome any thoughts on discoveries in regards to CPU flags and performance in Windows guests.
flags +invtsc;+topoext;+host-cache-info;-hypervisor
It seems for the performance boost HyperV should be left enabled in bcdedit.
The host CPU is a AMD 5600G, and all optional flags in the UI are on default.
There is one issue, all chromium web browsers have instability, the main process doesnt crash, but random stack break's instead on rendering processes, even spamming f12 for dev tools will cause crashes.
If I remove the -hypervisor flag, the crashes go away, likewise if I disable HyperV in bcdedit, the crashes go away. But these also both lose the performance boost, like as removing any of the custom flags removes the performance boost, its quite a delicate combination of flags.
The flags in this thread yield a gain of about 10% without instability, I dont care for live migrations. So I will probably leave at that given, there seems no way forward on the bigger gain, but I welcome any thoughts on discoveries in regards to CPU flags and performance in Windows guests.
Attached is a file with benchmark results for several Hyper-V enlightenment combinations for qemu/kvm. Below is a summary of my findings compared to the Proxmox defaults. Those are based on a Windows 10 Pro VM with q35-8.0 system and host CPU based on 13th Gen Raptor Lake Intel Core i7-13700T...great, would be interesting which one of the hv flags makes the real difference (instead of using the catchall hv_passthrough) so we could maybe enable it for future machine types (in combination with pci passthrough)
but i understand if you don't have the time to test all from the list
