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HiState gets up to 5.73x faster p99 time-to-first-token for agents, by keeping recurrent checkpoints on SSD

AspireAI community · arXiv
Hybrid models mix full-attention layers with recurrent linear layers, and their prefix caches inherit an awkward asymmetry: a prefix hit reuses every matching KV entry but only one recurrent checkpoint, and that checkpoint cannot be reconstructed for a shorter prefix. Agent workloads make this worse, because they edit and revisit earlier context, exposing reusable prefixes whose checkpoints were never saved or have already been evicted. HiState exploits the asymmetry by parking historical checkpoints on SSD while keeping KV entries in fast memory, and adds adaptive interval control plus unified eviction to balance checkpoint storage against recomputation. Built on vLLM and evaluated on two public coding-agent trace datasets, it reports up to 5.73x and 5.44x speedups in p99 time-to-first-token against vLLM-Marconi and SGLang-HiCache. The speedups come from the p99 tail on agent traces, which is the regime the work targets but also the one most sensitive to workload shape.
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