Published on Thursday was the latest patch by AMD's Christian König that adds large PTE support for their most recent GPUs -- the Northern Islands (HD 6000 series) through Southern/Sea Islands (HD 7000 series and newer; GCN hardware).
Christian explained in the patch contents:
This patch implements support for VRAM page table entry compression. PTE construction is enhanced to identify physically contiguous page ranges and mark them in the PTE fragment field. L1 TLB and L2 cache support is enabled for 64KB (SI/CIK) and 256KB (NI) PTE fragments, significantly improving TLB utilization for VRAM allocations.
Linear store bandwidth is improved from 60GB/s to 125GB/s on Pitcairn. Unigine Heaven 3.0 sees an average improvement from 24.7 to 27.7 FPS on default settings at 1920x1200 resolution with vsync disabled.
This patch wasn't part of the latest Radeon DRM fixes for Linux 3.15; hopefully this performance enhancing patch will be applied for the Linux 3.16 kernel. Of course, when it is mainlined, you can surely bet that it will be benchmarked on Phoronix. In case you missed it, we posted some Radeon Linux 3.14 vs. 3.15 benchmarks yesterday.