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Diffstat (limited to 'ext/ffi/README.md')
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diff --git a/ext/ffi/README.md b/ext/ffi/README.md index cc2d81cd2..5f7f1cb9f 100644 --- a/ext/ffi/README.md +++ b/ext/ffi/README.md @@ -1,3 +1,25 @@ # deno_ffi This crate implements dynamic library ffi. + +## Performance + +Deno FFI calls have extremely low overhead (~1ns on M1 16GB RAM) and perform on +par with native code. Deno leverages V8 fast api calls and JIT compiled bindings +to achieve these high speeds. + +`Deno.dlopen` generates an optimized and a fallback path. Optimized paths are +triggered when V8 decides to optimize the function, hence call through the Fast +API. Fallback paths handle types like function callbacks and implement proper +error handling for unexpected types, that is not supported in Fast calls. + +Optimized calls enter a JIT compiled function "trampoline" that translates Fast +API values directly for symbol calls. JIT compilation itself is super fast, +thanks to `tinycc`. Currently, the optimized path is only supported on Linux and +MacOS. + +To run benchmarks: + +```bash +target/release/deno bench --allow-ffi --allow-read --unstable ./test_ffi/tests/bench.js +``` |