It's been a while since last comparing the performance of the Windows and Linux Intel Haswell OpenGL graphics drivers. Last year when we looked at the Intel "Haswell" HD Graphics 4600 performance the driver speeds under Ubuntu Linux and Windows 8.1 were almost neck-and-neck, but since then it seems the rate of performance optimizations and improvements within the Intel Windows driver has outpaced the open-source Intel Linux graphics driver.
The results being posted today are of a comparison between Ubuntu 14.04 LTS and Windows 8.1 with all available updates at the time of testing on 16 May. On the Linux side we were running Ubuntu 14.04 but had upgraded to the Linux 3.15 Git kernel and for the user-space Intel components had loaded the Oibaf PPA to provide the xf86-video-intel 2.99.911 DDX driver and Mesa 10.3.0-devel. Our Intel Windows 8 Haswell-compatible driver was versioned Intel 10.18.10.3574 Beta driver from late April.
For benchmarking we used a variety of cross-platform OpenGL games that are known to be of similar quality under Windows and Linux. The same hardware was used under the Windows and Linux testing with a Intel Core i7 4770K Haswell CPU with HD Graphics 4600, 16GB of RAM, and 120GB Samsung SSD 840. All benchmarking under Windows 8.1 Pro x64 and Ubuntu 14.04 LTS x86_64 was done via the Phoronix Test Suite for complete automation and reproducibility.