Release notes for GPU tracing (#2080)

Author: alice-i-cecile

release-content/0.16/release-notes/_release-notes.toml

@@ -134,6 +134,13 @@ contributors = []
 prs = [17953]
 file_name = "17953_Add_support_for_experimental_WESL_shader_source.md"
 
+[[release_notes]]
+title = "GPU timestamps in traces"
+authors = ["@JMS55"]
+contributors = []
+prs = [18490]
+file_name = "gpu_tracing.md"
+
 [[release_notes]]
 title = "Virtual Geometry Improvements"
 authors = ["@JMS55"]

release-content/0.16/release-notes/gpu_tracing.md

@@ -0,0 +1,26 @@
+If you wish to optimize something, you must first measure and understand it.
+When looking at the performance of applications, [tracy] is our tool of choice.
+It gives us a clear understanding of how long work takes, when it happens relative to other work each frame,
+and how various threads are used.
+Read our [profiling docs] to get started!
+
+But until now, it's had a critical limitation: work done on the GPU wasn't shown,
+forcing devs to pull up dedicated GPU-focused tools (like [NSight] or [RenderDoc]) and struggle to piece together an intuition for how it all fits together.
+
+In 0.16, we've connected the [rendering diagnostics added in Bevy 0.14] to [tracy], creating a cohesive picture of
+all of the work that's being done in a Bevy application in a single convenient place.
+
+That said, we've only instrumented a few of our passes so far.
+While we will improve this in the future, you will need to add spans to your own custom rendering code,
+and specialized GPU diagnostic tools will always be more powerful: capturing all GPU-related work done,
+and providing more detailed information.
+
+Special thanks to [@wumpf] for trailblazing this work in the excellent [wgpu-profiler] tool, and demonstrating how to wire [wgpu] and [tracy] together.
+
+[tracy]: https://github.com/wolfpld/tracy
+[profiling docs]: https://github.com/bevyengine/bevy/blob/main/docs/profiling.md
+[NSight]: https://developer.nvidia.com/nsight-systems
+[RenderDoc]: https://renderdoc.org/
+[@wumpf]: https://github.com/Wumpf
+[wgpu-profiler]: https://github.com/Wumpf/wgpu-profiler
+[rendering diagnostics added in Bevy 0.14]: https://bevyengine.org/news/bevy-0-14/#tools-for-profiling-gpu-performance