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prefillcache
confirmedPython · llama.cppInference & servingJuly 5, 2026
the question
How much does prompt-prefix caching actually save, and how does the payoff scale with prefix length?
what came out
Warm prefill stays flat at ~8-11ms while cold grows linearly, so a reused shared prefix goes from an 8x speedup at 114 tokens to 81x at 1841 -- 88-99% of prefill eliminated, nearly free after the first request.
method & receipts
- Result: confirmed
- Reproducible — one script re-runs the whole thing from scratch.
- 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/prefillcache