ABKT: An Adaptive KV Cache Transfer Optimization Scheme for PD Separation Architecture

ABKT (Adaptive Bitrate KV Cache Transfer) is an adaptive bitrate KV cache transfer scheme optimized for large language model (LLM) inference in the PD (Prefill-Decode) separation architecture. Its core is to reduce communication overhead in distributed inference through mixed-precision quantization. Original author/maintainer: 354100117, Source platform: github, Original link: https://github.com/354100117/ABKT, Release time: 2026-06-03T09:45:22Z.

With the expansion of LLM scale, single-node inference can hardly meet the requirements of high concurrency and low latency, so the PD separation architecture emerged (prefill and decode stages are allocated to different nodes). However, in this architecture, KV cache needs to be transferred between nodes, and the large data volume in long-sequence and high-concurrency scenarios makes communication overhead a performance bottleneck.

The core mechanisms of ABKT include: 1. Adaptive mixed-precision quantization: Apply different quantization precisions to different layers, heads, and positions based on context importance (e.g., 8-bit for high-attention positions, 4/2-bit for less important ones); 2. PD separation optimization: Analyze KV cache characteristics during the prefill stage and select quantization strategies by predicting decoding needs; 3. Dynamic bitrate adjustment: Dynamically adjust quantization levels according to network bandwidth and latency (use high precision when bandwidth is sufficient, reduce precision to maintain throughput during congestion).

Quantization algorithms: Symmetric/asymmetric quantization (selected based on KV distribution), group quantization (reduce the impact of outliers), dynamic range scaling (adjust scale according to value range). Compression and transfer: Differential coding (utilize temporal locality), sparsity utilization (identify sparse patterns), pipeline transmission (hide latency).

Applicable scenarios of ABKT: 1. Distributed inference services: Reduce inter-node communication overhead and improve throughput of long-document/high-concurrency online services; 2. Edge computing: Ensure inference quality in bandwidth-constrained environments; 3. Cost optimization: Reduce data transmission to lower cloud service network costs.

ABKT reduces KV cache transfer overhead while maintaining model output quality through adaptive mixed-precision quantization, providing a direction for LLM inference optimization in PD separation architecture. Future explorations can include: integration with advanced architectures like MoE, finer-grained adaptive strategies, and deep optimization for specific hardware platforms.