EMA C++ Performace Tools Guide : 5 Interactive Provider Performance Tool : 5.4 Latency Measurement
 
5.4 Latency Measurement
EmaCppIProvPerf encodes the timestamp as part of its message payload. The timestamp is taken at the start of encoding and added as field TIM_TRK_1 (3902) for Update message, field TIM_TRK_2 (3903) for Post message, and field TIM_TRK_3 (3904) for Generic message. Latency is measured after ConsPerf completes decoding.
Interactive Provider Latency Measurement Sequence:
1. Get the current time (t1).
2. Encode the message, including time t1.
3. Pass the message to the API, which passes it to the underlying transport.
4. The consuming application receives the timestamp in the payload and compares it against the current time to calculate latency.