Poor performance with Intel GVT-g

I wrote a post on using Intel GVT-g tech with Proxmox to share an iGPU between a Linux VM hosting Plex and a Windows VM hosting Blue Iris for my blog last month.

Unfortunately the performance is anywhere from 20-50% of what the iGPU is capable of. This is using an i5 8500 on Proxmox - here are the ‘conversion speeds’ I see when syncing a file for offline playback with Plex.

  • plex on bare metal with quicksync - 8-10x conversion speed
  • 1 virtual gvt-g gpu - v5_4 - 4x
  • 2 virtual gvt-g gpus - v5_8: 2x
  • purely software: 1x

4x is fine-ish but I’d really love to get closer to the full capabilities of Quicksync if possible. Are there any secrets that I’m missing out on the make the best of this?

I might be mistaken, but my understanding is that GVT-g splits the GPU’s processing capacity between the host and the guest, so these results make sense.