RadeonSI Performance Improvement For DRI PRIME Offloading

Marek Olšák has managed to secure another performance win with his continued efforts to improve the RadeonSI Gallium3D driver performance.

Marek just published a set of eight patches for the RadeonSI driver and as part of that increases the performance for DRI PRIME offloading. The caveat though is the secondary GPU has to be a Sea Islands or Volcanic Islands graphics processor, just any conventional DRI PRIME offloading setup won't see a change from today's patches.

The patches by Marek enable SDMA support for CIK hardware as part of the series. Marek explained that SDMA is much faster for tiled to linear blits from vRAM to GTT. With his tests of an AMD Tonga GPU as the primary GPU and a Bonaire GPU secondary, the DRI PRIME performance was much faster with SDMA support. With glxgears as a lightweight test, the SDMA support with DRI PRIME offloading was 44% faster. Of course, most people won't be having a secondary AMD GPU they use for offloading so this might not be too relevant for a majority of the Linux gamers.

SDMA (System DMA) support was first introduced with AMD's CIK GPUs as new asynchronous DMA engines for compute and graphics. These latest RadeonSI patches can be found via the Mesa mailing list.