Optimizing MiniMax M3 Sparse Attention on NVIDIA Blackwell

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.