I'm running the latest Ubuntu on Oracle VirtualBox. When I keep the window at default small size, it runs almost as smoothly as the Windows 10 host. However, when I maximize the window, the lag immediately becomes unbearable. I have 4K monitor, so could the big resolution affect performance so much?

Here are specs of my PC

  • Asus X370-PRO Motherboard
  • AMD Ryzen 7 1700 8 cores @ 3,75 Ghz
  • GeForce GTX 1060 OC 6 GB GDDR5
  • 16GB (2 x 8GB) G.Skill DDR4 2666MHz

I have enabled the processor virtualization mode in BIOS settings, and here are the settings I have assigned to the virtual machine

  • 4096 MB of Base Memory
  • Enable I/O APIC
  • 8 processors with 100% execution cap
  • Enable PAE/NX
  • Enable AMD-V
  • 128 MB of Video Memory (Max allowed by the VirtualBox UI)
  • Enable 3D Acceleration

I'm especially concerned about the maximum of 128 MB V-RAM allowed, regarding my GPU has 6 GB of memory. I'm sure with this stack the VM should run smoothly even at full screen 4K doing some heavy rendering, so something is obviously wrong. Have I misconfigured the VM or is the VirtualBox itself not supporting 4K well?

  • Virtualizing GPUs is still in its infancy. I suspect it has to do either the GPU not being utilized or under utilized putting the 4k rendering on your CPU. – Damon Nov 11 '17 at 15:37
  • I'm having a similar problem with a fast host (XPS, 32GB, i9 6CPU, SSD, Ubuntu 18.04.01) and well configured guest (8GB, 4CPU, Ubuntu 18.04.01 with correct version of extensions installed and running, 128GB Video, 3D passthrough, full-screen on 4k external monitor at 100%). Sometimes gets unusably laggy - e.g. 1 second to show key in terminal; 4 seconds to bring a terminal window to front. Rebooting the VM fixed it, but it goes bad again. Changing to window from full-screen might be initial cause? Maybe video driver memory leak? Guest Kubuntu 18.04 Plasma crashed permanently (similar cause?) – robocat Jan 23 at 1:22

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