Topic: How from productivity samplings to delete wait time?

In a principal flow I launch 4 worker threads which fulfill the primary goal. The trouble consists that samplings by means of a command time and Vtune Amplifier include wait time of the main flow in the results (and when at me the flow for asynchronous performance of tasks, also its wait time also is launched):

QThread:: yieldCurrentThread ();

How to get rid of these unnecessary values which should be subtracted from an execution time mentally permanently?