← Lab
latencytail
confirmedC++ · llama.cppInference & servingJuly 6, 2026
the question
What does each concurrent request cost a local inference server?
what came out
Three regimes. Below the slot count, a batching tax -- per-token latency grows as the server decodes more active requests per step. Exactly at the slot count (C=4), a jitter spike: p99/p50 jumps to 2.24 (1.5B) and 2.67 (0.5B) versus ~1.2-1.3 elsewhere, the one concurrency where decode isn't smooth. Above it, queueing. Closed-loop C++ libcurl load generator.
method & receipts
- Result: confirmed
- Pre-registered — the prediction was written down and committed before the run.
- Reproducible — one script re-runs the whole thing from scratch.
- Independently reviewed — an adversarial review pass, kept in the repo.
- Machine-readable claims — every reported number, in a checkable file.
- Tested — a correctness/benchmark suite ships alongside the code.
→ read the code and re-run it
github.com/v-code01/latencytail