What is issue efficiency?

Issue efficiency measures how effectively the warp scheduler keeps execution pipes busy by issuing instructions from eligible warps .

An issue efficiency of 100% means every scheduler issued an instruction on every cycle, indicating at least one eligible warp on each cycle. Values below 100 % signal that, during some cycles, all active warps were stalled - waiting on data, resources, or dependencies - so the scheduler sat idle and overall instruction throughput fell.