i915 Passthrough sluggish perfomance

[sshaikh]

Although I have successfully passed through an 14700K using i915, I am finding that typical desktop performance (over XRDP) is actually worse with the VF passed though.

I know the iGPU is being passed through because webgl demo pages work without CPU load.

I'm not quite sure how to measure this lag and sluggishness objectively, I can only say that scrolling, selecting windows etc all feel like they come with a new latency that wasn't present before.

Could it be that the CPU is just that much more powerful than the iGPU, or is there an XRDP issue here?

[johntdavis84]

I use xrdp with UHD 770 passthrough in an older Ubuntu VM. It’s worked really well, but I think you should always expect some loss of performance to passthrough overhead with the i915 driver. But I haven’t experienced the lags or reduced performance you’re talking about. Maybe I can help. Which Linux does your VM use? What do `lsb_release -a` and `uname -a` say? Which `xrdp` are you using? Where did you download and install it from? The fork with the best GPU acceleration support for Intel is here, but it only supports Debian/Ubuntu, I think: neutrinolabs/xrdp#2383 There are instructions there to rip out any other version before installing that one. Do you have the `intel-gpu-tools` installed on the host and inside the VM? Depending on your machine, running `intel_gpu_top -d sriov` should show your iGPU working. (`Nvtop` will as well, but it works best if you’re using the Xe driver and is somewhat limited with i915.) As far as testing, are you seeing the expected FPS from https://testufo.com/ ? How far can you push https://webglsamples.org/aquarium/aquarium.html before you lose a 60 FPS lock?

[sshaikh]

Thank you for the comprehensive reply!

I am running Arch in the VMs, so no lsb_release. Otherwise:

❯ uname -a
Linux dev 6.19.12-arch1-1 #1 SMP PREEMPT_DYNAMIC Sat, 11 Apr 2026 22:36:29 +0000 x86_64 GNU/Linux

versions:

local/xorgxrdp-glamor 0.10.5-1
    Xorg drivers for xrdp, with glamor enabled. Only works on Intel and AMD GPUs.
local/xrdp 0.10.5-1
    An open source remote desktop protocol (RDP) server

xorgxrdp-glamor is a version of xorgxrdp compiled with the --glamor flag.

nvtop detects GPU usage (eg with testufo). I get the following error with intel:

❯ intel_gpu_top
Failed to detect engines! (No such file or directory)
(Kernel 4.16 or newer is required for i915 PMU support.)

Interestingly I get the following error on two of the VMs:

❯ vulkaninfo | grep GPU
ERROR at /usr/src/debug/vulkan-tools/Vulkan-Tools/vulkaninfo/./vulkaninfo.h:249:vkGetPhysicalDeviceDisplayPlanePropertiesKHR failed with ERROR_OUT_OF_HOST_MEMORY

But the third works okay. I think this is a red herring though.

❯ vulkaninfo | grep GPU
                GPU id = 0 (Intel(R) Graphics (RPL-S))
                GPU id = 0 (Intel(R) Graphics (RPL-S))
GPU id : 0 (Intel(R) Graphics (RPL-S)) [VK_KHR_xcb_surface, VK_KHR_xlib_surface]:
GPU0:
        deviceType        = PHYSICAL_DEVICE_TYPE_INTEGRATED_GPU

testufo gets me 60fps. 25k fish with aquarium, struggle at 30k.

I also looked at issue 2383:

❯ sudo cat /var/log/xrdp.log | grep encoder_create
[2026-04-23T21:33:44.884+0100] [INFO ] xrdp_encoder_create: starting h264 codec session gfx
[2026-04-23T21:33:44.886+0100] [INFO ] xrdp_encoder_create: using x264 for software encoder

❯ glxinfo | grep renderer
    GLX_MESA_copy_sub_buffer, GLX_MESA_gl_interop, GLX_MESA_query_renderer,
    GLX_MESA_copy_sub_buffer, GLX_MESA_gl_interop, GLX_MESA_query_renderer,
Extended renderer info (GLX_MESA_query_renderer):
OpenGL renderer string: Mesa Intel(R) Graphics (RPL-S)

❯ vainfo
Trying display: wayland
Trying display: x11
vainfo: VA-API version: 1.23 (libva 2.22.0)
vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 25.4.6 ()

I usually run using RFX instead of H.264, but tried the latter in case it was that. It didn't make a diff.

[sshaikh]

I just switched back to RFX:

[2026-04-26T17:03:30.690+0100] [INFO ] xrdp_encoder_create: starting gfx rfx pro codec session
[2026-04-26T17:03:30.692+0100] [INFO ] xrdp_encoder_create: using x264 for software encoder

And it is much better, however I now realise that a fresh VM (eg after reboot) is highly performant, and over time the latency degrades. I'm becoming better at objectively testing the lag so will confirm this over time. It may be an XRDP issue.