arXiv:2511.00321cs.ARcs.AI2025-11被引 5

用CXL技术把大模型的缓存放到内存附近,突破GPU内存限制。

Scalable Processing-Near-Memory for 1M-Token LLM Inference: CXL-Enabled KV-Cache Management Beyond GPU Limits

  • 将缓存页选择移到CXL内存中的加速器,避免频繁数据调入
  • 支持100万词长上下文,吞吐提升21.9倍,每字节能耗降低60%
  • 适合超长文本生成、大模型部署等需要海量上下文的场景

大型语言模型(LLM)上下文窗口扩展至百万级令牌时,键值(KV)缓存管理带来严重的内存与计算瓶颈。尽管计算快速链接(CXL)可实现非淘汰机制,将完整KV缓存外置于可扩展的外部内存,但随着上下文长度增加,从外部内存召回非驻留令牌到有限的GPU内存仍导致高昂的数据传输开销。本文提出面向百万令牌推理的可扩展处理近内存(PNM)架构,基于CXL的KV缓存管理系统,实现内存与计算在GPU边界之外的协同。设计将令牌页选择任务卸载至CXL内存内的加速器,消除高成本召回,支持更大GPU批处理规模。进一步引入混合并行策略与稳定令牌选择机制,提升计算效率与可扩展性。基于先进的CXL-PNM系统实现,该方案对高达4050亿参数、100万令牌上下文的LLM表现一致性能提升。纯PNM卸载方案(PNM-KV)与GPU-PNM混合的稳定令牌执行方案(PnG-KV),相较基线实现最高21.9倍吞吐提升、60倍更低每令牌能耗、7.3倍更优总成本效率,证明了CXL-enabled多PNM架构可作为未来长上下文大模型推理的可扩展核心。

原文摘要 · Abstract (English)

The expansion of context windows in large language models (LLMs) to multi-million tokens introduces severe memory and compute bottlenecks, particularly in managing the growing Key-Value (KV) cache. While Compute Express Link (CXL) enables non-eviction frameworks that offload the full KV-cache to scalable external memory, these frameworks still suffer from costly data transfers when recalling non-resident KV tokens to limited GPU memory as context lengths increase. This work proposes scalable Processing-Near-Memory (PNM) for 1M-Token LLM Inference, a CXL-enabled KV-cache management system that coordinates memory and computation beyond GPU limits. Our design offloads token page selection to a PNM accelerator within CXL memory, eliminating costly recalls and enabling larger GPU batch sizes. We further introduce a hybrid parallelization strategy and a steady-token selection mechanism to enhance compute efficiency and scalability. Implemented atop a state-of-the-art CXL-PNM system, our solution delivers consistent performance gains for LLMs with up to 405B parameters and 1M-token contexts. Our PNM-only offloading scheme (PNM-KV) and GPU-PNM hybrid with steady-token execution (PnG-KV) achieve up to 21.9x throughput improvement, up to 60x lower energy per token, and up to 7.3x better total cost efficiency than the baseline, demonstrating that CXL-enabled multi-PNM architectures can serve as a scalable backbone for future long-context LLM inference.

大模型推理长上下文CXL内存优化

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