profiling

MBU is one division, and that is why it is so easy to get wrong. The answer defines both operands precisely on a real server and then shows six ways a dashboard can report a number 30 points off.

A 60% MBU number is a symptom, not a diagnosis. The answer rebuilds the floor from bytes, then splits the missing 40% into buckets a profiler can confirm and a team can own.

A 2.5x gap at batch 1 almost never comes from the GPU being slow. The answer sorts the suspects by what a single profiler trace shows and puts a millisecond figure on each.

Every kernel in the step can run near peak bandwidth while the step itself runs at two thirds of it. The answer reads the three rows of the timeline that tell you why, and turns the gaps into milliseconds.

FP8 halves the weight bytes, and the dashboard says the replica got slower. The answer computes what FP8 should have bought, splits the gap into kernel, scale and config terms with one profiler trace, and catches the regression that is not in the GPU at all.