vLLM hits 500K GPUs as co-founder Simon Mo makes the case for open models

Half a million GPUs are now running vLLM. That number, cited by the project’s own maintainers, is the kind of figure that stops a conversation cold. What vLLM actually is, and why it matters vLLM started at UC Berkeley’s Sky Computing Lab as a research project tackling one of inference’s most stubborn problems: GPU memory is expensive, and large language models waste a lot of it. The core innovation is something called PagedAttention. Think of it like virtual memory management for your laptop, but applied to the KV cache that language models use to track context. It lets a GPU serve far more requests simultaneously by being smarter about how it allocates memory on the fly. The project now supports over 500 model architectures and more than 200 accelerator types. In May 2025, it became a PyTorch Foundation project. The GitHub star count climbed into the tens of thousands rapidly. Simon Mo, Inferact, and the $150M bet on open inference Simon Mo, one of vLLM’s core maintainers, co-founded Inferact in 2025. The company raised a $150M seed round at an $800M valuation, led by a16z and Lightspeed. Mo has been vocal about why open-weight models deserve serious consideration for production ...