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The paper introduces HierarchicalKV (HKV), a novel GPU hash table library that implements cache semantics for continuous online embedding storage, addressing the HBM limitations of traditional dictionary-semantic hash tables. HKV employs cache-line-aligned buckets, score-driven upsert, dynamic dual-bucket selection, and triple-group concurrency, along with tiered key-value separation for scaling beyond HBM capacity. Benchmarks on an NVIDIA H100 NVL GPU demonstrate HKV achieves up to 3.9 B-KV/s find throughput and outperforms existing dictionary-semantic baselines like WarpCore by up to 1.4x and indirection-based baselines by 2.6-9.4x.
Stop wasting precious GPU memory: this new cache-semantic hash table library achieves up to 3.9 billion key-value lookups per second, outperforming standard approaches by up to 9.4x.
Traditional GPU hash tables preserve every inserted key -- a dictionary assumption that wastes scarce High Bandwidth Memory (HBM) when embedding tables routinely exceed single-GPU capacity. We challenge this assumption with cache semantics, where policy-driven eviction is a first-class operation. We introduce HierarchicalKV (HKV), the first general-purpose GPU hash table library whose normal full-capacity operating contract is cache-semantic: each full-bucket upsert (update-or-insert) is resolved in place by eviction or admission rejection rather than by rehashing or capacity-induced failure. HKV co-designs four core mechanisms -- cache-line-aligned buckets, in-line score-driven upsert, score-based dynamic dual-bucket selection, and triple-group concurrency -- and uses tiered key-value separation as a scaling enabler beyond HBM. On an NVIDIA H100 NVL GPU, HKV achieves up to 3.9 billion key-value pairs per second (B-KV/s) find throughput, stable across load factors 0.50-1.00 (<5% variation), and delivers 1.4x higher find throughput than WarpCore (the strongest dictionary-semantic GPU baseline at lambda=0.50) and up to 2.6-9.4x over indirection-based GPU baselines. Since its open-source release in October 2022, HKV has been integrated into multiple open-source recommendation frameworks.