Optimizing MiniMax M3 Sparse Attention on NVIDIA Blackwell

What this post added

This post details the engineering effort to optimize the MiniMax M3 sparse attention mechanism on NVIDIA Blackwell GPUs. It introduces a KV-stationary execution path, analyzes the performance trade-offs between Q-outer and KV-outer approaches, and describes specific optimizations for the attention store and load balancing. The resulting kernel achieves significant throughput improvements and speedups over existing baselines.