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Apr 15, 2025
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Add note about how to preserve debug symbols in Rust #21347

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Add note about how to preserve debug symbols in Rust
lukevalenta Apr 2, 2025
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Update src/content/docs/workers/observability/dev-tools/cpu-usage.mdx
lukevalenta Apr 14, 2025
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18 changes: 18 additions & 0 deletions src/content/docs/workers/observability/dev-tools/cpu-usage.mdx
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Expand Up @@ -32,6 +32,24 @@ To generate a CPU profile:

You now have a CPU profile.

:::note

For Rust Workers, add the following to your `Cargo.toml` to preserve [DWARF](https://dwarfstd.org/) debug symbols (from [this comment](https://github.com/rustwasm/wasm-pack/issues/1351#issuecomment-2100231587)):
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Hi @lukevalenta 👋 Is wasm an industry standard that we trust? It can be tricky to use external dependencies like that in the docs if it could be subject to change or even become malware. If not, is there some more general advice we can provide instead? Thanks!

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Hi @ToriLindsay, Web Assembly (wasm) is the the glue that allows us to run any compiled language (like Rust, Go, or C on Workers (see https://developers.cloudflare.com/workers/runtime-apis/webassembly/), so this PR isn't suggesting to add any external dependencies that aren't already present.

(cc @zebp or @irvinebroque)

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@lukevalenta Ah ok. I didn't recognize the acronym. Thanks for the clarification! I'll approve.


```toml title="wrangler.toml"
[package.metadata.wasm-pack.profile.dev.wasm-bindgen]
dwarf-debug-info = true
```

Then, update your `wrangler.toml` to configure wasm-pack (via worker-build) to use the `dev` [profile](https://rustwasm.github.io/docs/wasm-pack/commands/build.html#profile) to preserve debug symbols.

```toml title="Cargo.toml"
[build]
command = "cargo install -q worker-build && worker-build --dev"
```

:::

## An Example Profile

Let's look at an example to learn how to read a CPU profile. Imagine you have the following Worker:
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