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5 Fun Projects for LLM Inference Engineering

🔗 https://www.kdnuggets.com/5-fun-projects-for-llm-inference-engineering

📌 從零重建 Mini-vLLM:5 個推理工程實作題

TL;DR:想搞懂 LLM 為何能跑得快,就自己動手重建 KV cache、FlashAttention、量化與推測解碼。

訓練 LLM 的文章滿天飛,但模型訓練完成只是開始。真正決定使用者體感的,是模型上線後能不能用更少的記憶體、更低的延遲,從同一批 GPU 擠出更多 tokens——而這套工程學問,最好的學法不是讀論文,是自己動手拆。

🤔 KV cache、batching、量化:推理工程的七大武器

LLM inference engineering 的核心目標是降低延遲、提高吞吐量、減少記憶體用量,並從手上的硬體擠出更多產出。涵蓋的技術包括 KV caching、continuous batching、quantization、prefix caching、speculative decoding、優化過的 attention kernel,以及分散式推理。作者認為,逐一讀懂這些名詞不如直接動手建構一個系統,看它在哪裡卡住、哪裡變快。

🧩 五個專案,從陽春生成到生產級服務

  1. 從零重建 Mini-vLLM:以 Nano-vLLM(一個教育用、程式碼量小到能完整讀完的 vLLM 風格推理引擎,內建排程、KV-cache block 管理、prefix caching、tensor parallelism、CUDA graphs,使用真實的 Qwen 模型)為基礎。不要直接跑現成範例,而是先寫最樸素的 autoregressive generation,再依序加上 KV cache、batching、以 block 為單位的 KV-cache 配置,每加一項就測一次 tokens/sec,藉此體會 PagedAttention 與 continuous batching 的真正作用。

  2. 用 Triton 寫一個 FlashAttention kernel:一般的 attention 實作要在 GPU 的高頻寬記憶體(HBM)與晶片內的高速快取(SRAM)之間反覆搬動大矩陣,FlashAttention 透過重新安排計算順序減少這些資料搬移量。可以參考 Triton 官方教學裡的 fused attention kernel 實作,也有對應影片從 HBM 與 SRAM 的差異、arithmetic intensity、tiling、online softmax 一路講到把 kernel 整合進推理引擎。這個專案最直接的收穫是:讓模型變快,不一定是減少運算量,而是減少搬動的資料量。

  3. 打造一個 LLM 量化實驗室:拿同一個小型開源模型,分別跑出 FP16、INT8、4-bit 等版本,量測模型大小、峰值記憶體、模型載入時間、Time to First Token(TTFT)、tokens/sec,以及在小型評測集上的品質。Hugging Face 支援 AWQ、GPTQ、bitsandbytes 的 8-bit/4-bit 載入等多種量化方式;llama.cpp 則支援多種低位元格式,可跑在 CPU、Apple Silicon、NVIDIA GPU 等多種硬體上。進階挑戰是同時量化 weights 與 KV cache,觀察位元數減少是否真的總能帶來更低延遲。

  4. 實作推測解碼(speculative decoding):讓一個小型 draft model 先一次提議多個候選 token,再由昂貴的 target model 一次性驗證這些候選,而不是逐 token 跑完整個生成。先寫出樸素的逐 token decoding 作為 baseline,再加上 draft-and-verify 迴圈,追蹤 tokens/sec 之外,也要記錄 acceptance rate(draft token 被 target model 接受的比例),並實驗一次 draft 2、4、6、8 個 token 的差異。可參考 Columbia 的高效能機器學習專案,該專案以 Llama 系列模型評估延遲、吞吐量、perplexity 與程式碼生成品質。有趣的延伸是換不同工作負載測試:程式碼、重複性文字、事實問答、創意寫作的 draft acceptance 行為可能差異很大。

  5. 打造自己的生產級 LLM 推理服務:把前四個專案整合成一個 capstone。從一個 OpenAI 相容的推理端點開始,部署到 GPU 上,加入 streaming,接著做 load testing,並量測 TTFT 與逐 token 生成延遲。再疊加量化、實驗推測解碼、加入 prefix caching,最後把並發請求數一路推高,看看系統在哪裡先出問題。可參考 Time to First Token 專案的 roadmap,它以「持續改進同一套推理服務」而非一堆零散練習為主軸。更進階的延伸是加入一個 request router,依佇列長度、預期生成長度或延遲需求,決定該由哪個模型或哪張 GPU 處理請求。

💡 變快的關鍵不是算得少,而是搬得少

這五個專案串起來的共同主題是:真正困難的問題往往不是訓練模型本身,而是記憶體配置、排程、batching、caching、kernel 最佳化、網路與負載測試,以及如何讓非常昂貴的硬體保持忙碌。

🎯 拆開 vLLM 的黑箱,自己重建一次

對工程師而言,從陽春的逐 token 生成開始,一路加上 KV cache、batching、分頁式 KV-cache、量化、推測解碼、自寫 kernel,最後包成一個 API 並拿負載測試轟炸它——走完這條路之後,vLLM、SGLang 之類的工具就不再是黑箱,而是你已經親手重建過的縮小版。

🔗 來源

#LLM #InferenceEngineering #vLLM #FlashAttention #Quantization #SpeculativeDecoding #Triton #GPU #MachineLearning #MLOps

原始資料 KDnuggets · 收集於 2026-10-14
來源原標題
5 Fun Projects for LLM Inference Engineering
作者
Kanwal Mehreen
原始連結
https://www.kdnuggets.com/5-fun-projects-for-llm-inference-engineering

摘要原文

5 Fun Projects for LLM Inference Engineering Want to understand what makes LLMs fast? Build the systems yourself. By Kanwal Mehreen , KDnuggets Technical Editor & Content Specialist on October 14, 2026 in Artificial Intelligence Training large language models gets most of the attention, but once a model is trained, another engineering problem begins: how do you serve it quickly and efficiently? LLM inference engineering focuses on reducing latency, increasing throughput, lowering memory consumption, and getting more useful work from the available hardware. This involves techniques such as KV caching, continuous batching, quantization, prefix caching, speculative decoding, optimized attention kernels, and distributed inference. The best way to learn these concepts is not by reading about them individually — it is by building something and seeing what happens. In this article, we will look at 5 projects that progressively introduce the most important ideas behind modern LLM inference systems . 1. Building a Mini-vLLM From Scratch If you want one project that exposes you to almost the entire inference stack, this is probably the best place to start. Nano-vLLM is a small educational implementation of a vLLM -style inference engine, with its core implementation small enough to actually read. It includes scheduling, KV-cache block management, prefix caching, tensor parallelism, CUDA graphs, and other optimizations while using a real Qwen model. Instead of simply cloning it and running the example, rebuild one component at a time: first perform normal autoregressive generation, then add KV caching, then batching, then block-based KV-cache allocation. Benchmark tokens per second after every addition. By the end, you will understand concepts like PagedAttention and continuous batching in a much better way. 2. Writing Your Own FlashAttention Kernel With Triton A normal attention implementation uses large matrices and repeatedly moves data between GPU memory and fast on-chip memory. FlashAttention restructures the computation to reduce that memory traffic. Triton's official tutorial provides an implementation of a FlashAttention-style fused attention kernel, making it a great starting point for learning kernel-level optimization. This video also builds FlashAttention from scratch while explaining HBM versus SRAM, arithmetic intensity, tiling, online softmax, benchmarking, and finally integrating the kernel into an inference engine. I would recommend it to those who prefer video-based learning. This project teaches you that making an LLM faster is not always about doing fewer mathematical operations. Sometimes it is about moving less data . 3. Building an LLM Quantization Lab Take one small open model and run several versions — for example FP16, INT8, and 4-bit. Measure model size, peak memory, model-load time, time to first token (TTFT), tokens per second, and quality on a small evaluation set. Hugging Face supports multiple quantization approaches, including AWQ, GPTQ, bitsandbytes-based 8-bit and 4-bit loading, and several newer formats. llama.cpp also supports a wide range of low-bit quantization formats and runs across CPUs, Apple Silicon, NVIDIA GPUs, and several other hardware backends. For an extra challenge, quantize both the weights and KV cache and see whether using fewer bits always improves latency or not. 4. Implementing Speculative Decoding Speculative decoding is one of the most enjoyable inference optimizations to implement. Instead of asking the expensive target model to generate every token sequentially, a smaller draft model proposes several candidate tokens. The target model then verifies those candidates together. Choose a small target/draft pair, implement normal autoregressive decoding as the baseline, and then build the draft-and-verify loop. Track not only tokens per second but also acceptance rate — which is the percentage of draft tokens accepted by the target model. Then experiment with drafting 2, 4, 6, or 8 tokens at a time. The Columbia high-performance machine learning project experiments with both speculative decoding and quantization using the Llama model family while evaluating latency, throughput, perplexity, and code-generation quality. An interesting extension is to test different workloads. Code, repetitive text, factual question-answering, and creative writing can produce very different draft acceptance behavior. 5. Building Your Own Production LLM Inference Service The final project is a capstone where we combine KV caching, quantization, batching, and benchmarking into a single system. Start with a basic OpenAI-compatible inference endpoint. Deploy it on a GPU. Add streaming. Add load testing. Instrument TTFT and token-generation latency. Introduce quantization. Experiment with speculative decoding. Add prefix caching. Push concurrency higher and identify what breaks first. The Time to First Token project provides an interesting structure for doing this. Its roadmap revolves around continuously improving one inference service rather than completing disconnected exercises. It covers deployment, instrumentation, heavy concurrency testing, quantization, speculative decoding, routing, and reproducible benchmarking. For an even harder extension, add a request router that decides which model or GPU should process each request based on queue length, expected generation length, or latency requirements. Wrapping Up You need enough machine learning knowledge to understand transformers and attention, but many of the hardest problems have surprisingly little to do with training models. They involve memory allocation, scheduling, batching, caching, kernel optimization, networking, load testing, and figuring out how to keep very expensive hardware busy. This is why building projects is such a good way to learn the field. Start by generating one token inefficiently. Add a KV cache. Batch several users together. Break the cache into pages. Quantize the weights. Let a smaller model speculate about future tokens. Write a GPU kernel. Then put everything behind an API and bombard it with requests. By the time you finish, tools such as vLLM and SGLang will no longer feel like black boxes. You will have built smaller versions of many of the ideas that make them fast. Kanwal Mehreen is a machine learning engineer and a technical writer with a profound passion for data science and the intersection of AI with medicine. She co-authored the ebook "Maximizing Productivity with ChatGPT". As a Google Generation Scholar 2022 for APAC, she champions diversity and academic excellence. She's also recognized as a Teradata Diversity in Tech Scholar, Mitacs Globalink Research Scholar, and Harvard WeCode Scholar. Kanwal is an ardent advocate for change, having founded FEMCodes to empower women in STEM fields. <= Previous post Next post =>

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