Function min_rows 

pub fn min_rows() -> usize

Effective threshold: CMF_GPU_MIN_ROWS overrides. Defaults differ by device class: on a DISCRETE card VRAM bandwidth pays off even for FFN/QKV-class matrices (4096), on unified memory only lm_head-class is worth the dispatch/readback (65536). Field case behind this: a 35B model on an RTX 4090 saw ~0 offload because every layer matrix sat below the old universal 65536.