0.12: Tracing Span Caching

content/news/2023-10-21-bevy-0.12/index.md

@@ -19,12 +19,22 @@ Since our last release a few months ago we've added a _ton_ of new features, bug
 
 <div class="release-feature-authors">authors: @author</div>
 
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+## Reduced Tracing Overhead
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+<div class="release-feature-authors">authors: @hymm, @james7132</div>
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+Bevy uses the [tracing](https://crates.io/crates/tracing) library to measure systems running time among other things. This is useful for determining where bottlenecks in frame time are and measuring performance improvements, and can be visualized using the [tracy](https://github.com/wolfpld/tracy) tool. However, using tracing's spans has a significant overhead to it. A large part of the per-span overhead is due to allocating the string description of the span. By caching the spans for systems, commands, and parallel iteration, we have significantly reduced the CPU time overhead when using tracing. In the PR that introduces caching the system spans, the many foxes stress test went from 5.35 ms to 4.54 ms. In the PR that adds caching for the parallel iteration spans, the many cubes stress test went from 8.89 ms to 6.8 ms.
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+![tracing overhead](tracing-overhead-reduction.png)
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 ## <a name="what-s-next"></a>What's Next?
 
 We have plenty of work that is pretty much finished and is therefore very likely to land in **Bevy 0.13**:
 
 Check out the [**Bevy 0.13 Milestone**](https://github.com/bevyengine/bevy/milestone/17) for an up-to-date list of current work being considered for **Bevy 0.13**.
 
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