While leaked slides indicate AMD was planning better gaming on Linux for Crimson, in the end they really didn't deliver. Even for their mentioned games, when testing various Linux OpenGL games on three different systems the performance was largely unchanged.
For the past six hours since the release of Radeon Software Crimson Edition for Linux, I've been busy running Linux gaming tests on a Radeon R9 290, R9 295, and R7 370 as a selection of modern graphics cards now that they dropped the pre-GCN graphics card support.
It was a bit sad to see with Crimson they didn't yet unify their new control panel but are still using the same AMDCCCLE control panel on Linux. However, that wasn't a confirmed feature of Crimson on Linux. With AMD slides having indicated "Linux performance improvements" from "112% to 155%", I was very excited to run benchmarks on this Radeon Software 15.11 for Linux release.
On the R9 285, R9 290, and R7 370 I ran tests from an Ubuntu 15.04 host system with Catalyst 15.9 (the previous stable release) and then compared them to today's Radeon Software Crimson Edition release.
All tests were facilitated via the open-source Phoronix Test Suite and all of the results are on the following pages.