2021-08-06 17:28:10 -04:00
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# deno_ffi
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This crate implements dynamic library ffi.
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2022-07-11 21:03:05 -04:00
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## Performance
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Deno FFI calls have extremely low overhead (~1ns on M1 16GB RAM) and perform on
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par with native code. Deno leverages V8 fast api calls and JIT compiled bindings
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to achieve these high speeds.
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`Deno.dlopen` generates an optimized and a fallback path. Optimized paths are
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triggered when V8 decides to optimize the function, hence call through the Fast
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API. Fallback paths handle types like function callbacks and implement proper
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error handling for unexpected types, that is not supported in Fast calls.
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Optimized calls enter a JIT compiled function "trampoline" that translates Fast
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API values directly for symbol calls. JIT compilation itself is super fast,
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thanks to `tinycc`. Currently, the optimized path is only supported on Linux and
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MacOS.
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To run benchmarks:
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```bash
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target/release/deno bench --allow-ffi --allow-read --unstable ./test_ffi/tests/bench.js
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```
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