Performance

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ZeroAlloc.Resilience is designed so that the proxy adds zero heap allocation on the happy path for methods without [Timeout]. All benchmarks are measured with BenchmarkDotNet (.NET 10, Release mode, [MemoryDiagnoser]).

Results

Benchmark	Mean	Allocated
Direct call (no proxy)	~2 ns	0 B
Retry proxy — first attempt succeeds	~8 ns	0 B
CircuitBreaker proxy — Closed state	~12 ns	0 B
RateLimit proxy — token available	~18 ns	0 B
All-policies proxy — happy path	~35 ns	96 B †
CircuitBreaker proxy — Open (fast-reject)	~4 ns	0 B
RateLimit proxy — exhausted (fast-reject)	~3 ns	0 B
Retry proxy — 2 failures then success	~1.2 ms ‡	0 B

† The 96 B in the all-policies benchmark comes from the CancellationTokenSource created by [Timeout]. Without [Timeout], the proxy allocates 0 bytes.

‡ The 2-failure retry benchmark includes real Task.Delay(backoff) pauses (BackoffMs = 1). Mean reflects wall-clock delay, not CPU overhead.

What drives each result

Direct call — ValueTask.FromResult("ok") from the inner implementation. Baseline reference.

Retry — first attempt succeeds — enters the retry loop, runs the for iteration once, calls the inner method, returns. Zero allocation.

CircuitBreaker — Closed — CanExecute() is a Volatile.Read on a long field. Call passes through. Zero allocation.

RateLimit — token available — TryAcquire() is a Volatile.Read + Interlocked.CompareExchange. Token decremented, call passes through. Zero allocation.

All-policies — happy path — rate-limit check, CB check, CancellationTokenSource.CreateLinkedTokenSource (96 B), CancelAfter, per-attempt linked CTS (linked to total), inner call, OnSuccess, return. The 96 B is the CancellationTokenSource — unavoidable for timeout.

CB — Open (fast-reject) — CanExecute() returns false immediately. The check itself allocates nothing. The benchmark's catch block allocates the ResilienceException object — that allocation is the caller's, not the proxy check.

RateLimit — exhausted — TryAcquire() returns false after seeing zero tokens. Instantaneous reject. Zero allocation on the proxy path.

Design invariants

• No boxing — CircuitBreakerFsm and RateLimiter use long fields; enum values cast to/from long is a no-op at the CPU level.
• No closures, no delegates — the proxy is a concrete class with a concrete method. Nothing is captured.
• No LINQ on the hot path — branching is compiled into if checks and a for loop with literal values.
• CancellationTokenSource is the only unavoidable allocation — one per call when [Timeout] is configured. Methods without [Timeout] allocate nothing.

Running the benchmarks yourself

cd benchmarks/ZeroAlloc.Resilience.Benchmarks
dotnet run -c Release

To run a specific benchmark:

dotnet run -c Release --filter "*HappyPath*"