Phoronix compared the GPU performance of Windows and Linux

Yesterday we shared benchmarks of the ATI R600 Gallium3D driver compared against the classic Mesa R600 driver and then the proprietary AMD Catalyst driver. The proprietary driver was much faster than the open-source drivers were, but the Gallium3D driver did possess higher performance in most of the tests than with the classic Mesa driver. This is similar to the R300 Gallium3D driver being faster than its now-deprecated R300 classic driver. Meanwhile though Intel continues to back only their classic Mesa DRI driver and there are no signs of them switching over to the Gallium3D architecture anytime soon. It is not as if Intel's current Mesa driver is feature-complete and performance-optimized as our tests from earlier this year show Intel's Linux graphics performance being far behind their Windows driver. In this article though we are seeing where the Intel Mesa performance is at when using the very latest DRM and Mesa code.

  Intel Windows vs. Linux GPU Performance Q4'2010