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PayPalOne thing currently a bit lacking on Linux is the performance of ray tracing with the open source Mesa RADV driver, but a big improvement is coming. And to no surprise, it's thanks to funding from Valve as they continue to improve Linux graphics drivers.
Developer Natalie Vock, who works as an independent contractor for Valve, has submitted a merge request on January 3rd that should give some nice improvements. To be clear though, this is code that has not yet been pulled into Mesa, it may still need some more work before it is.
As Vock said in it:
A looong time ago, in !26105 (merged), I discovered that unaligned dispatches with 8x4/8x8 workgroups and a dispatch height of 1 (1D dispatch) do not work well together and limit occupancy to 8 threads per wave, absolutely ruining perf.
The workaround in that MR worked on direct dispatches, fixing up the dispatch size to be >4 (or >8) threads in the Y dimension. Of course, fixing up the dispatch size is only possible for direct dispatches where the size is known at command recording time. Back then, I considered this edge case acceptable. After all, what are the chances that someone would ever dispatch an indirect TraceRays with a 1D dispatch size? Surely no one would ever do that, especially not one of the most ubiquitous high-fidelity game engines out there in their widely-adopted ray-traced global illumination solution...
This MR resolves the indirect RT edge case as well, by forgoing any hacks on CPU depending on the dispatch size. Instead, we dispatch 1D workgroups and move all swizzling logic to the RT prolog.
Implementing our own swizzling logic also allows us to be smarter about the swizzle pattern and arrage invocations in a Z-order curve.
Should provide a ~4x-8x speedup in UE5's HW Lumen passes, amounting to ~30% total FPS gain in my coarse measurements.
Benchmarks on whether the improved swizzling logic improves other RT workloads as well are welcome!
Those are some bold claims but there's no reason to doubt it, it's all public code anyone can test. So of course someone did get some early testing done. In the comments, a user posted their own benchmarks before applying the patch and after, and the results are quite a surprise to see. As they noted:
| Game | Before | After |
|---|---|---|
| Desordre | 51 FPS | 89 FPS |
| Layers of Fear (2023) | 75 FPS | 98 FPS |
| Oblivion Remastered | 45 FPS | 56 FPS |
| Silent Hill 2 Remake | 40 FPS | 60 FPS |
They don't list what computer specifications they have or what settings each game used, but it's still a nice win to see.
By the time the new Steam Machine launches later this year which will use the AMD RADV driver from Mesa, we will hopefully see some pretty great performance across a lot of games.
Source: Phoronix
Article taken from GamingOnLinux.com.
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You can also find comments for this article on social media: Surely no one would ever do that, especially not one of the most ubiquitous high-fidelity game engines out there in their widely-adopted ray-traced global illumination solution...That's some great snark there.
Last edited by Purple Library Guy on 7 Jan 2026 at 3:54 pm UTC
Although: that said, I'm not sure I notice/care that much about raytracing just in general. It makes things look SLIGHTLY just a tiny bit better at a huge frame cost? But maybe with this the frame cost will be minimal so that slightly better look will be okay?
This performance boost is great (:
Last edited by SlayerTheChikken on 8 Jan 2026 at 6:31 pm UTC
Quoting: JarmerNice! Gotta love these huge improvements for same hardware.Apparently some developers are mostly using ray tracing not to improve the visuals but as a crutch that allows them to not bother implementing lighting at all as they normally should, like iirc the latest Doom game doesn't work without ray tracing at all, although when you set it to low the performance is not as horrible as you may expect from ray tracing (but still pretty horrible)
Although: that said, I'm not sure I notice/care that much about raytracing just in general. It makes things look SLIGHTLY just a tiny bit better at a huge frame cost? But maybe with this the frame cost will be minimal so that slightly better look will be okay?
Gerarderloper 22 hours ago
Last edited by Stella on 8 Jan 2026 at 12:26 am UTC
yourpalsteve 18 hours ago
Quoting: JarmerApparently some developers are mostly using ray tracing not to improve the visuals but as a crutch that allows them to not bother implementing lighting at all as they normally should, like iirc the latest Doom game doesn't work without ray tracing at all, although when you set it to low the performance is not as horrible as you may expect from ray tracing (but still pretty horrible)This is a pretty unfair take IMO. Lighting the old way is one of the most time consuming things in game development right now. Ray tracing or path tracing would make lighting a game much much less time consuming.
The problem is that over the past decades devs have managed to get pretty close to replicating large parts of the look of raytraced lighting in traditional lighting models.
So now that raytraced lighting is here it only looks marginally better than what traditional lighting has offered. The only difference is that it's much less time consuming to implement. Which is not a crutch but a handy tool to keep dev times down while still making things look good.
I'm not sure when they're doing the freeze on new things.
Quoting: rustynailI mean, you've just repeated the same thing I said but made it sound positive. Of course it's cool that they don't have to spend time on it, and I guess since I could play Doom Dark Ages at almost 60 fps on my low-mid tier rx6600 after all and it's in theory should only get better in the future, it's probably worth itQuoting: JarmerApparently some developers are mostly using ray tracing not to improve the visuals but as a crutch that allows them to not bother implementing lighting at all as they normally should, like iirc the latest Doom game doesn't work without ray tracing at all, although when you set it to low the performance is not as horrible as you may expect from ray tracing (but still pretty horrible)This is a pretty unfair take IMO. Lighting the old way is one of the most time consuming things in game development right now. Ray tracing or path tracing would make lighting a game much much less time consuming.
The problem is that over the past decades devs have managed to get pretty close to replicating large parts of the look of raytraced lighting in traditional lighting models.
So now that raytraced lighting is here it only looks marginally better than what traditional lighting has offered. The only difference is that it's much less time consuming to implement. Which is not a crutch but a handy tool to keep dev times down while still making things look good.
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