KV Cache-Aware Routing and P/D Disaggregation on Kubernetes — Yuchen Fama & Ashish Kamra, Red Hat
This talk details advanced strategies for optimizing LLM inference in complex agentic workloads, moving beyond the limitations of steady-state public benchmarks. The focus is on two critical levers: KV Cache-Aware Routing and Prefill/Decode (P/D) Disaggregation. Implementing these techniques—using frameworks like LLMD—significantly improves latency and throughput by managing volatile cache usage and separating compute-bound prefill from memory-bandwidth-hungry decode phases, particularly in the middle concurrency band.
Key takeaways
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Agentic Workloads vs. Benchmarks
5:29
Real-world agentic workloads exhibit chaotic multi-turn interactions (up to 3,000 turns) with high cache hit rates (>90%) and massive input/output ratios (often >100:1), which standard public benchmarks fail to capture [0:00], [3:29].
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KV Cache Routing Optimization
10:28
Implementing KV cache-aware routing (via Endpoint Picker) is a cost-effective optimization, as the token cost difference between cached and uncached tokens can be as high as 10x [5:12]. This helps solve Time to First Token (TTFT) issues.
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P/D Disaggregation Benefits
15:28
Separating prefill and decode into independent, scalable pods prevents 'phase interference'—where a long prefill stalls token generation (decode)—leading to drastically reduced P99 Inter Token Latency (ITL) from ~900ms down to ~100ms [9:28], [10:46].
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Prerequisites for PD
17:26
Effective P/D disaggregation requires an advanced, high-speed network fabric like RDMA or RoCE to facilitate the transfer of KV caches between prefill and decode workers [10:46]. If such a fabric is unavailable, aggregated serving may be preferable.
