check-performance

check-performance

Role: review the shard against the project's performance targets.

Failure model: the code is correct but breaks a real-time or budget commitment, allocates on a hot path, or does work that grows worse than linearly with input the caller controls.

Performance targets are project-specific. Read the design docs and the descriptor for the project's budgets (frame time, callback latency, query cost, scan throughput) before sweeping. What follows is the sweep pattern, not the budget.

Look for

1. Allocation on hot paths. A real-time callback (audio, video, input) or a per-frame function that allocates on the steady path: no incidental allocation, no internal collection growth, no formatting inside the loop. A per-keystroke query path must not allocate per call beyond the result vector. Any allocation in these paths is a finding.
2. Locks on hot paths. A lock held across an unbounded operation on a real-time or per-frame path. Cross-thread communication on a hot path belongs on a lock-free queue or an atomic, not a mutex.
3. Arithmetic that defeats SIMD or the hardware. Inner loops over sampled data written as scalar code when the platform's vector type would do; mixed precision inside a hot loop that forces a conversion per iteration. Vectorization is not always the right answer; the choice must be deliberate, and a benchmark wins the argument.
4. Unbounded work from unbounded input. A scan that processes a whole set synchronously without yielding; a decode that loads the whole payload before streaming; an analysis whose runtime grows worse than linearly with input length; a layout that recomputes from scratch on every change.
5. Query and index efficiency. A query that scans the whole set when an index would do; a filter that re-realizes a lazy sequence on every access; a lookup that walks a list when a set or map would do; a sort or projection recomputed when the input has not changed.
6. Waste in a render or diff pipeline. A per-frame allocation in a diff path; a uniform or buffer update that re-uploads static data; a descriptor or command buffer rebuilt when a single binding changed.
7. Throughput on a scan or batch path. A scan that reads the whole payload to compute a value the header would yield; a batch that reworks items whose input has not changed (a content hash is the gate); a batch that holds a shared lock for its whole duration.