[Bug 218525] Thunderbolt eGPU bad performance

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218525

kaukov.peter@pm.me changed:

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                 CC|                            |kaukov.peter@pm.me

--- Comment #3 from kaukov.peter@pm.me ---
I would also like to chime in regarding eGPUs on Linux. I'm using Nvidia and my
current setup uses an RTX 4090. I ran the Unigine Heaven Benchmark 4.0 on the
Extreme preset on both Windows 11 Pro and Gentoo with kernel 6.6.16 and
Nvidia's proprietary 550.54.14 drivers. I will attempt to attach both benchmark
results later.

The Windows benchmark scored 238 points higher and its minimum fps 21.2 higher,
while the maximum fps is 23.8 higher. The average fps is 9.4 higher on Windows.

The results seem ok, but the real-world performance is different.

On Nvidia, when opening a program that's hardware-accelerated, the whole system
stutters. I think this is an Nvidia-only bug so it can be dismissed.

Some native Linux games straight up crash or run very poorly on the eGPU. My
latest encounter is Last Epoch where I got ~20fps on the native port and
~50-60fps via DXVK.

The worst offenders are Unity3D Engine games and MMORPGs. The only game that
was able to achieve close to Windows performance was World of Warcraft and
that's after ticking or unticking the "Tripple Buffering" graphics option even
though vsync isn't used in-game. This somehow refreshes the game/renderer and
it starts rendering at high frames per second. FFXIV is stuck at 40-70 fps.
Guild Wars 2 struggles to go beyond 20fps even though the RTX3050Ti dGPU of the
same laptop manages to get 40-60fps.

Baldur's Gate 3 is also a prime example of the issue. On Linux, I get 35-40fps
on the character select screen and 2-12fps in-game. I can get 60-80fps on the
3050Ti dGPU. Both when running via DXVK.

The eGPU runs at the expected PCIe3.0x4 speed - LinkSta 8GT/s.

Wayland is completely unusable on the eGPU while perfectly fine on the dGPU.

I'll also try uploading dmesg and lspci logs here.

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