Besides the recent work to support OpenGL Geometry Shaders for Sandy Bridge in Mesa, users of Intel "Sandy Bridge" HD Graphics can also be thankful for the forthcoming Linux 3.17 kernel. Early testing of Linux 3.17 has revealed that for at least some Intel Sandy Bridge hardware are OpenGL performance improvements with the newer kernel code.
Earlier I covered the open-source Radeon graphics improvements in Linux 3.17 but for at least Intel HD Graphics 3000 series users there are also some performance optimizations packed into this kernel that's still weeks from its official debut. With Intel's Open-Source Technology Center being busy with advancing Haswell / Bay Trail support and finishing up Broadwell / Cherryview graphics support and even working towards Skylake graphics on Linux, it's a bit of a surprise seeing the faster Sandy Bridge graphics with Linux 3.17.
In carrying out fresh OS X vs. Linux graphics tests from a Sandy Bridge era Apple Mac Mini is when I discovered the greater performance between Linux 3.16 stable and Linux 3.17 Git. The Core i5-2415M Mac Mini with HD 3000 Graphics was running Ubuntu 14.04 64-bit and using the Oibaf PPA for Mesa 10.3-devel Git and other updated user-space components. This testing is strictly comparing Linux 3.16.0 stable vs. Linux 3.17 20140820 Git with no configuration or settings changes between the kernel upgrade. All of the benchmarking was carried out via the Phoronix Test Suite performance testing software. Tests are still being carried out on Linux 3.17 of other generations of Intel hardware.