IEC functionality is divided into separate functional parts. Each functional part has a limitation on the number of worker threads that it can utilize. Conclusions concerning which functional part is under or over worked can be drawn based on how many percent of their threads they utilize.
The maximum number of threads for each functional part is a fixed value that will not be surpassed.
The threads page also display a peak length. This value is often equal to the maximum value. This allows IEC to quickly creates threads to cope with messages arriving in bursts. This is particularly true if no messages have been processed prior to IEC being started.
The best approach to get reliable information regarding functional parts thread utilization is to monitor that particular page in SAT while IEC is processing a relevant message load. If a functional part has a significantly higher thread use than the others, there are properties that control the maximum number threads that the functional part can use.