should_send_immediately_ requires both should_try_send_immediately
flag AND batch_delay==0. Without setting batch_delay to 0, all
sends were falling back to the batch path.
Increase socket buffer to 16MB so benchmarks never hit WOULD_BLOCK
during an inner loop iteration. Remove per-iteration drain_socket
calls that were adding noise and causing the immediate path to
fall back to batching. Drain only between outer iterations.
Add benchmarks for the full send_sensor_state path covering both
immediate send and batch paths. This measures the end-to-end cost
of sending a sensor state update through an APIConnection including
entity field population, proto encode, framing, and TCP write.
J. Nick Koston