Parallel GPU buffer writes

[aevyrie]

Objective

• After a series of optimizations making render and postupdate more parallel, write_batched_instance_buffers was regularly one of the largest spans with very low thread use, sitting at 4ms in 1 4ms frame. This makes it an ideal target to improve throughput. Note this screenshot doesn't include some visibility system optimizations:

Solution

• Spawn tasks for writing buffers to the GPU. This is especially helpful for current_input_buffer and previous_input_buffer, which take about the same time and are the longest buffer writes - moving these to tasks effectively halves the time spent in the system.

• In the 250k bevymark_3d stress test, this saves 1.7ms in the system, and 2.8ms in frame time

frametime

system

Testing

• cargo rer bevymark_3d --features=debug,trace_tracy -- --benchmark --waves 250 --per-wave 1000