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Wasm optimization tips (#5443)
# Objective Add a section to the example's README on how to reduce generated wasm executable size. Add a `wasm-release` profile to bevy's `Cargo.toml` in order to use it when building bevy-website. Notes: - We do not recommend `strip = "symbols"` since it breaks bindgen - see https://github.com/bevyengine/bevy-website/pull/402
This commit is contained in:
Nicola Papale
parent
619c30c036
commit
a7f2120c9e
3 changed files with 166 additions and 2 deletions
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@ -1534,3 +1534,9 @@ target_sdk_version = 31
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[package.metadata.android.application]
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icon = "@mipmap/ic_launcher"
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label = "Bevy Example"
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[profile.wasm-release]
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inherits = "release"
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opt-level = "z"
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lto = "fat"
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codegen-units = 1
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@ -459,7 +459,9 @@ following commands.
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```sh
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cargo build --release --example lighting --target wasm32-unknown-unknown
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wasm-bindgen --out-name wasm_example --out-dir examples/wasm/target --target web target/wasm32-unknown-unknown/release/examples/lighting.wasm
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wasm-bindgen --out-name wasm_example \
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--out-dir examples/wasm/target \
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--target web target/wasm32-unknown-unknown/release/examples/lighting.wasm
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```
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The first command will build the example for the wasm target, creating a binary. Then,
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@ -480,6 +482,83 @@ python3 -m http.server --directory examples/wasm
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ruby -run -ehttpd examples/wasm
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```
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### Optimizing
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On the web, it's useful to reduce the size of the files that are distributed.
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With rust, there are many ways to improve your executable sizes.
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Here are some.
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#### 1. Tweak your `Cargo.toml`
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Add a new [profile](https://doc.rust-lang.org/cargo/reference/profiles.html)
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to your `Cargo.toml`:
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```toml
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[profile.wasm-release]
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# Use release profile as default values
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inherits = "release"
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# Optimize with size in mind, also try "s", sometimes it is better.
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# This doesn't increase compilation times compared to -O3, great improvements
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opt-level = "z"
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# Do a second optimization pass removing duplicate or unused code from dependencies.
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# Slows compile times, marginal improvements
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lto = "fat"
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# When building crates, optimize larger chunks at a time
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# Slows compile times, marginal improvements
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codegen-units = 1
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```
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Now, when building the final executable, use the `wasm-release` profile
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by replacing `--release` by `--profile wasm-release` in the cargo command.
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```sh
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cargo build --profile wasm-release --example lighting --target wasm32-unknown-unknown
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```
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Make sure your final executable size is smaller, some of those optimizations
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may not be worth keeping, due to compilation time increases.
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#### 2. Use `wasm-opt` from the binaryen package
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Binaryen is a set of tools for working with wasm. It has a `wasm-opt` CLI tool.
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First download the `binaryen` package,
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then locate the `.wasm` file generated by `wasm-bindgen`.
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It should be in the `--out-dir` you specified in the command line,
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the file name should end in `_bg.wasm`.
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Then run `wasm-opt` with the `-Oz` flag. Note that `wasm-opt` is _very slow_.
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Note that `wasm-opt` optimizations might not be as effective if you
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didn't apply the optimizations from the previous section.
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```sh
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wasm-opt -Oz --output optimized.wasm examples/wasm/target/lighting_bg.wasm
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mv optimized.wasm examples/wasm/target/lighting_bg.wasm
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```
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For a small project with a basic 3d model and two lights,
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the generated file sizes are, as of Jully 2022 as following:
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|profile | wasm-opt | no wasm-opt |
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|----------------------------------|----------|-------------|
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|Default | 8.5M | 13.0M |
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|opt-level = "z" | 6.1M | 12.7M |
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|"z" + lto = "thin" | 5.9M | 12M |
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|"z" + lto = "fat" | 5.1M | 9.4M |
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|"z" + "thin" + codegen-units = 1 | 5.3M | 11M |
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|"z" + "fat" + codegen-units = 1 | 4.8M | 8.5M |
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There are more advanced optimization options available,
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check the following pages for more info:
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- <https://rustwasm.github.io/book/reference/code-size.html>
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- <https://rustwasm.github.io/docs/wasm-bindgen/reference/optimize-size.html>
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- <https://rustwasm.github.io/book/game-of-life/code-size.html>
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### Loading Assets
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To load assets, they need to be available in the folder examples/wasm/assets. Cloning this
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@ -207,7 +207,9 @@ following commands.
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```sh
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cargo build --release --example lighting --target wasm32-unknown-unknown
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wasm-bindgen --out-name wasm_example --out-dir examples/wasm/target --target web target/wasm32-unknown-unknown/release/examples/lighting.wasm
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wasm-bindgen --out-name wasm_example \
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--out-dir examples/wasm/target \
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--target web target/wasm32-unknown-unknown/release/examples/lighting.wasm
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```
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The first command will build the example for the wasm target, creating a binary. Then,
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@ -228,6 +230,83 @@ python3 -m http.server --directory examples/wasm
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ruby -run -ehttpd examples/wasm
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```
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### Optimizing
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On the web, it's useful to reduce the size of the files that are distributed.
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With rust, there are many ways to improve your executable sizes.
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Here are some.
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#### 1. Tweak your `Cargo.toml`
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Add a new [profile](https://doc.rust-lang.org/cargo/reference/profiles.html)
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to your `Cargo.toml`:
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```toml
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[profile.wasm-release]
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# Use release profile as default values
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inherits = "release"
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# Optimize with size in mind, also try "s", sometimes it is better.
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# This doesn't increase compilation times compared to -O3, great improvements
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opt-level = "z"
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# Do a second optimization pass removing duplicate or unused code from dependencies.
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# Slows compile times, marginal improvements
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lto = "fat"
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# When building crates, optimize larger chunks at a time
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# Slows compile times, marginal improvements
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codegen-units = 1
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```
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Now, when building the final executable, use the `wasm-release` profile
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by replacing `--release` by `--profile wasm-release` in the cargo command.
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```sh
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cargo build --profile wasm-release --example lighting --target wasm32-unknown-unknown
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```
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Make sure your final executable size is smaller, some of those optimizations
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may not be worth keeping, due to compilation time increases.
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#### 2. Use `wasm-opt` from the binaryen package
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Binaryen is a set of tools for working with wasm. It has a `wasm-opt` CLI tool.
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First download the `binaryen` package,
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then locate the `.wasm` file generated by `wasm-bindgen`.
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It should be in the `--out-dir` you specified in the command line,
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the file name should end in `_bg.wasm`.
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Then run `wasm-opt` with the `-Oz` flag. Note that `wasm-opt` is _very slow_.
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Note that `wasm-opt` optimizations might not be as effective if you
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didn't apply the optimizations from the previous section.
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```sh
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wasm-opt -Oz --output optimized.wasm examples/wasm/target/lighting_bg.wasm
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mv optimized.wasm examples/wasm/target/lighting_bg.wasm
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```
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For a small project with a basic 3d model and two lights,
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the generated file sizes are, as of Jully 2022 as following:
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|profile | wasm-opt | no wasm-opt |
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|----------------------------------|----------|-------------|
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|Default | 8.5M | 13.0M |
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|opt-level = "z" | 6.1M | 12.7M |
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|"z" + lto = "thin" | 5.9M | 12M |
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|"z" + lto = "fat" | 5.1M | 9.4M |
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|"z" + "thin" + codegen-units = 1 | 5.3M | 11M |
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|"z" + "fat" + codegen-units = 1 | 4.8M | 8.5M |
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There are more advanced optimization options available,
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check the following pages for more info:
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- <https://rustwasm.github.io/book/reference/code-size.html>
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- <https://rustwasm.github.io/docs/wasm-bindgen/reference/optimize-size.html>
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- <https://rustwasm.github.io/book/game-of-life/code-size.html>
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### Loading Assets
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To load assets, they need to be available in the folder examples/wasm/assets. Cloning this
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