Back in early July was the initial work on Haswell's Resource Streamer. The resource streamer can accelerate commands that otherwise are on the CPU and take time to build-up until submitting to the GPU. For Haswell's resource streamer it can take the process of generating binding tables and constant buffers and offload all that work straight away to the resource streamer rather than the CPU.
The resource streamer has the potential to be of a performance benefit but in its initial form didn't provide much in the way of real-world performance benefits. The initial patches also caused random GPU lock-ups and were never merged.
Three months later to the day, Intel's Abdiel Janulgue has published his second version of the Haswell Resource Streamer patches for the Intel Mesa driver. This work requires sixteen Intel Mesa driver patches plus other Mesa and Linux kernel (Intel DRM) patches that were previously posted. The hard lock-ups should now be resolved and in acknowledging this as an experimental feature, the support is hidden behind a new environment variable "INTEL_RESOURCE_STREAMER=1" that must be set.
The latest Intel Haswell Resource Streamer patches can be found on the mesa-dev mailing list.