Performance

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Skuld achieves near-parity with hand-written evidence-passing CPS. Discounting BEAM try/catch overhead — irreducible and shared with all Elixir applications — the additional framework overhead is minimal.

Per-effect overhead

Progressive benchmarks starting from a bare CPS baseline and adding Skuld features one at a time (N=10,000, MIX_ENV=prod):

The largest single factor is BEAM try/catch frames (~0.163 µs/op for the first frame), not Skuld's own machinery. Three catch frames per loop iteration (call, bind, handler dispatch) account for most of the overhead relative to raw CPS.

Inline total+linear path

Effects implementing ITotalLinearHandler get an inline continuation path in comp do blocks:

# State is a total+linear handler — the comp macro emits inline
# continuations, skipping Comp.bind/2 closure allocation
comp do
  x <- State.get()
  y <- State.put(x + 1)
  y * 2
end

At N=10,000 this path is 1.5–1.8× faster than the nested-bind path and matches raw CPS within noise.

Per-tag operation optimisation

Tagged effects (e.g. State.get(:counter)) use per-tag module-atom signatures. The handler captures a precomputed state key at installation time, eliminating per-operation key computation and struct allocation:

The improvement collapses multiple overhead sources simultaneously: struct args, Change struct allocation, and state key computation are all reduced by the handler closing over precomputed values.

Data fetch benchmarks

Query batching benchmarks show FiberPool overhead at ~0.25 µs/op per fiber. For realistic workloads (database queries at ~1 ms), the overhead is noise. Automatic N+1 batching provides order-of-magnitude speedups for multi-fetch operations.

Where the overhead lives

The remaining vs-catch-baseline overhead (~2.1–2.3x) is composed of:

• Additional catch frames (~1.25x) — irreducible BEAM tax
• Struct argument allocation (~1.30x) — reduced by per-tag sigs
• Tuple state keys (~1.16x) — eliminated by per-tag sigs
• Env struct size and scoped machinery — negligible after inlining

Optimisation summary

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