El_Cubero
[Implemented guest buffer manager]
August 8, 2024August 11, 2024
What problem does this solve
Up until this point main branch used a host memory stream buffer for making all resources accessible to the GPU. This is because AMD hardware has very small alignment requirements for both uniform and storage buffers (only 4 bytes) while nvidia has 64/16 respectively. The device local-host visible part of memory is also too small for most systems to serve this purpose, and we probably need it for better things.
This adds a ton of overhead to GPU emulation as all buffer bindings need to memcpy a (sometime large) chunk of memory to the stream buffer. It was also slow as GPU is not using VRAM for fast access. It also didn’t work for storage buffers where the writes would be lost, as there was no way of preserving them in the volatile buffer.
This PR aims to solve most of the these issues by keeping a GPU side mirror of guest address space for the GPU to access. It uses write protection to track any modifications and will re-sync the ranges on demand when needed. It’s still a bit incomplete though in ways I will cover more below. Seems to fix flicker on RDR with AMD gpus, but it still persists on NVIDIA which needs more investigation.
https://shadps4.net/index.php/category/developing/
