Diagnosing vLLM KV-Cache Fragmentation, CUDA OOM, and PCIe P2P Bottlenecks on 4x L40S Nodes
Why tensor-parallel LLM serving crashes with torch.OutOfMemoryError at 74% VRAM utilization when ACS PCIe routing forces NCCL all-reduce traffic through the host CPU root complex?봞nd how to fix it.