On Fri, Aug 26, 2016 at 4:10 PM, Mario Kleiner <mario.kleiner.de@xxxxxxxxx> wrote: > On 08/18/2016 09:21 PM, Marek Olšák wrote: >> >> On Thu, Aug 18, 2016 at 4:23 AM, Michel Dänzer <michel@xxxxxxxxxxx> wrote: >>> >>> Maybe the rasterization as two triangles results in bad PCIe bandwidth >>> utilization. Using the asynchronous DMA engine for these transfers would >>> probably be ideal, but having the 3D engine rasterize a single rectangle >>> (either using the rectangle primitive or a large triangle with scissor) >>> might already help. >> >> >> There is only one thing that's bad for PCIe when the surface is >> linear: the 3D engine. Disabling all but the first shader engine and >> all but the first 2 RBs should improve performance for blits from VRAM >> to GTT. The closed driver does that, but I don't remember if the >> destination must be linear, must be in GTT, or both. In any case, SDMA >> should still be the best for VRAM->GTT blits. >> >> Marek >> > > Friday evening education question: > > So if you have multiple render backends active they compete for PCIe bus > access and some kind of "trashing" happens in the arbitration, drastically > reducing the bandwidth? I think it has more to do with the access patterns. The requests can't be scheduled as efficiently compared to contiguous linear accesses. Alex _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
