By default TCP stacks delay sending acknowledgments (ACKs) to improve efficiency and utilization of a network link. Delayed ACKs also improve receive latency by ensuring that ACKs are not sent on the critical path. However, if the sender of TCP packets is using Nagle’s algorithm, receive latency will be impaired by using delayed ACKs.
Using the EF_DELACK_THRESH environment variable the user can specify how many TCP segments can be received before Onload will respond with a TCP ACK. Refer to the Parameter List for details of the Onload environment delayed TCP ACK variables.