Animating Materials performs poorly sometimes

[atlv24]

Bevy version

latest main

Relevant system information

Please include:

• rustc 1.75.0
• Windows 10

What's performing poorly?

Updating many materials per frame. Repro by pointing NSight in frame debugger mode at the binary built by cargo build --example animated_material --release once #11524 is merged.

It looks like material updates are making gargantuan amounts of buffer memory barriers interleaved with coherent buffer copies, but the exact number of them changes per run. Sometimes its way more than others, but always regular per-frame for any given run. Frametime varies, sometimes it hovers around 3.6ms, other times around 12-14ms.

I suspect a system ordering ambiguity may be causing the inconsistency of the performance issue.

A bad run looks like this in NSight:

A good run looks like this:

Notice the amount of orange interleaved vkCmdCopyBuffer + vkCmdPipelineBarriers.

[atlv24]

Fixed by #11383