State change (draw call) overhead in wgpu is very high relative to vulkan

[alice-i-cecile]

Bevy users like @JMS55 and @HackerFoo have reported painfully high overhead costs paid by Bevy users due to our use of wgpu.

The "draw call overhead" issues are really more like state change overhead. In wgpu if you just call draw(), draw_indirect(), etc.. in an ultra tight loop, and don't do anything else in the loop, it's actually very fast. But if you do as much as bind a vertex and index buffer in that loop performance tanks relative to wgpu-hal or raw vulkan. And its something like the more bindings you change the more perf delta there is between wgpu and vulkan.

From @DGriffin91on Discord.

I'll be attempting to gather representative and/or minimal examples from the community: please link them here if you have any!

• extremely high draw call voxel game
• Caldera scene from a AAA game