Fedora's Mesa Drivers Have Been Running Slower As They Were Accidentally Debug Builds

It turns out Fedora 29's Mesa 19.0 packages have recently been shipping in a "debug" mode since they switched to using the Meson build system and that has been leading to slower performance.

As is generally the case when building in a "debug" mode, various assertions and other extra validation paths are exposed and that can greatly influence the performance of the resulting binaries in code-bases like Mesa and their OpenGL/Vulkan drivers. Fedora 29 has mistakenly been shipping their production Mesa packages under a debug build when using the Meson build system.

Feral Interactive's Alex Smith spotted this issue and reported the problem. "It includes extra shader validation at pipeline creation time in RADV, which leads to extremely long loading times in Vulkan games...this Mesa bug report has a comment from a user reporting long loading times in Rise of the Tomb Raider on Fedora, and I am able to reproduce the same on the current Fedora 29 packages (takes 20 minutes to load the largest level in the game compared to 2 minutes on a release build that I have done myself)."

Initially the bug was closed as being an upstream issue with Mesa, but then it was pointed out the behavior of "buildtype=plain" and ultimately needing to add "-Db_ndebug=true" to the package to satisfy the no-debug scenario as should be the case for shipping Linux distribution packages. Since yesterday evening, an updates Mesa package for Fedora 29/30 are now available for testing and should soon be rolling out as stable updates. This should greatly improve the experience for using the Mesa 19.0 drivers on Fedora 29.