Lavapipe: Dragged Into The Future

Some time ago I teased a new Mesa project that involved both features and perf. At last, it’s time to unveil the goods: a complete rewrite of all descriptor handling in Lavapipe thanks to one of RADV’s raytracing tamers, Konstantin Seurer.

It’s a feature that’s been confounding developers and users everywhere for years, but thanks to Konstantin’s tireless efforts over the past ETOOLONG, at last everyone will have the features they crave.

Was It Really That Difficult?

Yes.

In short, the work required rewriting all the LLVM-based JIT to dynamically generate all the image/buffer access code instead of being able to use a more fixed-function style of JIT. As the MR shows, the diff here is massive, and work is still ongoing to make it work everywhere.

It’s a truly Herculean effort by Konstantin that was only hindered by my goalpost-moving to fingerpaint in support for EXT_descriptor_buffer and EXT_mutable_descriptor_type.

What Does This Mean?

Primarily it means that Lavapipe should start to be able to work with VKD3D-PROTON and play (haha) real games. This has more uses in CI purposes as well, allowing broader coverage for all layered drivers that depend on EXT_descriptor_indexing.

And Perf?

Unfortunately, the added indirection is going to slightly reduce performance in some cases.

Work is ongoing to mitigate this, and I don’t have any benchmark results.