A 128-row chunk's attention ran 122 ms a layer as one graph and 62 ms split at
the stage boundaries (bench3 vs bench4); decode's 1-row graphs are faster
whole. split() now cuts when DEEPINFER_NEURON_REGION_SPLIT (default off now)
or, under DEEPINFER_NEURON_REGION_SPLIT_PREFILL (default on), when the step
has more than one row. Syncing after every region call (the queueing
hypothesis) did not help: 37.7 s TTFT at 512.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>