Real-time execution trace toolkit for Labwindows/CVI code optimization

Hello,

I am trying to optimize a real-time code in LabWindows/CVI by minimizing the time each section of the code is taking and finding the bottlenecks in the code. I check this time using the real-time execution trace toolkit.

However, I just found that there seems to be some constant error when using the real-time execution trace toolkit.

When I put the traceviewer "start" and "stop" right after each other, I get around 9us time difference. It seems that the CPU goes into some idle mode after the trace starts, or maybe it is the communication delay or something. 

I would appreciate it if someone can give me an idea of why this is happening. The application time window for real time is very limited and I am trying to minimize the time as much as possible. Even the 9 us error is hard to spare.

 I used the following code :

TraceConfigure (1, 1, 0, 25000, NULL);
TraceStart ();
TraceStopAndSend (HOST_ADDRESS);

and this is a picture from the real time execution trace toolkit.

Thanks.