Kernel Optimization

Table of Contents Introduction Why Inference Optimization Matters The vLLM Architecture at a Glance 3.1 Dynamic Paging and Memory Management 3.2 Scheduler and Batch Fusion Identifying Bottlenecks in Standard LLM Serving Custom Kernel Development: When and How 5.1 Choosing the Right Kernel to Accelerate 5.2 CUDA Basics for LLM Engineers Hands‑On: Building a CUDA Kernel for Multi‑Head Attention 6.1 Reference Implementation in PyTorch 6.2 Porting to CUDA: Step‑by‑Step 6.3 Integrating the Kernel with vLLM Performance Evaluation 7.1 Benchmark Setup 7.2 Results and Analysis Production‑Ready Deployment Tips Future Directions & Community Roadmap Conclusion Resources Introduction Large language models (LLMs) have moved from research curiosities to production‑grade services that power chatbots, code assistants, and knowledge‑base search. While the training phase often dominates headlines, the inference phase is where cost, latency, and user experience converge. A single request to a 70‑billion‑parameter model can consume multiple gigabytes of GPU memory and stall a server for seconds if not carefully engineered. ...

Introduction The demand for real‑time machine‑learning inference has exploded across industries—from recommendation engines that serve millions of users per second to autonomous‑vehicle perception stacks that must make decisions within a few milliseconds. While training pipelines have long benefited from massive GPU clusters and sophisticated graph optimizers, production inference workloads present a different set of challenges: Latency guarantees – Many user‑facing services cannot tolerate more than a few tens of milliseconds of tail latency. Throughput pressure – A single model may need to process thousands of requests per second on a single node, let alone across a fleet. Heterogeneous hardware – Inference services often run on a mix of CPUs, GPUs, TPUs, and even specialized ASICs. Dynamic traffic – Request rates fluctuate dramatically throughout the day, requiring systems that can adapt on‑the‑fly. Two techniques have emerged as decisive levers for meeting these constraints: ...