Very high CPU usage on MacOS

Summary

On MacOS, even simple Bevy apps cause very high CPU load; for example, even a blank app that just loads DefaultPlugins to render a blank window sits at ~50% CPU usage on an Apple Silicon M1. Add a couple of rendered meshes and postprocessing and it'll quickly go up to about ~90% CPU.

On Windows and Linux, the same app will comfortable sit below 1% (even with some light rendering.)

Additional notes:

• A MRP has been provided here.
• It uses the opt-level = 3 etc. trick from the docs.
• Compiling a --release build doesn't make a difference.
• In addition, when hiding the app, CPU load doubles, but I understand there have already been issues filed about this particular problem.

Bevy version

0.11.3 (but I also tried 66f72dd, the newest commit on main at the time.)

Relevant system information

• Rust 1.73.0
• MacOS Sonoma 14.0

AdapterInfo { name: "Apple M1", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
SystemInfo { os: "MacOS 14.0 ", kernel: "23.0.0", cpu: "Apple M1", core_count: "8", memory: "16.0 GiB" }

What you did

• Build a "blank" Bevy app (code available here)
• Compile and run it

What went wrong

Expected behavior: the app should cause CPU load in the single-digit percentage range, like it does on Windows (<1% CPU, on a Ryzen 7.)

Actual behavior: the app caused ~50% CPU load.