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Capture instructions to narrow a flamegraph #460

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Sep 26, 2023
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Capture instructions to narrow a flamegraph #460

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Expand Up @@ -104,6 +104,21 @@ Processed 5116 samples and lost 35.01%!
$ export RAYON_NUM_THREADS=16
```

### Focused flames

https://blog.anp.lol/rust/2016/07/24/profiling-rust-perf-flamegraph/ offers examples of filtering flamegraphs. This
is very useful when you want to zoom in on a specific operation. For example, to dig into fea-rs:

```shell
# Generate a perf.data
# You can also use perf record but cargo flamegraph seems to have nice capture settings for Rust rigged
$ rm -rf build/ perf.data && cargo flamegraph -p fontc -- --source ../OswaldFont/sources/Oswald.glyphs --emit-ir false

# ^ produced flamegraph.svg but it's very noisy, lets narrow our focus
# Example assumes https://github.com/brendangregg/FlameGraph is cloned in a sibling directory to fontc
$ perf script | ../FlameGraph/stackcollapse-perf.pl | grep fea_rs | ../FlameGraph/flamegraph.pl > fea-flame.svg
```

## Contributing

We have included a few git hooks that you may choose to use to ensure that
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