DeepInfer: What DeepSeek Open-Sourced, and What It Kept
DeepSeek's open-source engine runs one model on Blackwell and Ascend: why it came out, what the code shows, what was kept back, and what it means for vLLM users.
9 posts
DeepSeek's open-source engine runs one model on Blackwell and Ascend: why it came out, what the code shows, what was kept back, and what it means for vLLM users.
Why serving a big MoE model means spreading its experts over many GPUs, what dispatch and combine cost, and how DeepEP and its V2 redesign make it fast.
Inference servers in three groups: production engines and their stacks, local apps built on llama.cpp, and enthusiasts' specialized engines, with how to pick.
How engines split long prompts across steps, what the per-step token budget trades between time to first token and time per token, and how to set it.
How vLLM and SGLang guarantee valid JSON or a grammar: compiling a schema into a token mask, applying it at every step, and what it costs in latency and quality.
How a cheap guess and one verification pass produce several tokens per step, when it speeds things up and when it does not, measured.
Why a repeated prompt can cost almost nothing, how vLLM and SGLang find shared prefixes, what breaks a hit, and how to structure prompts for agents and chat.
Why production stacks run prefill and decode on separate GPUs, how NVIDIA Dynamo and llm-d move the KV cache between them, and when the split pays.
Real coding-agent turns replayed on a 27B model on one desk-side GPU: what the prefix cache saves, how many agents fit, how well it calls tools.