Hi Dave
One useful method is to activate SUPPORT_LOW_POWER in config.h and also define an output to MEASURE_LOW_POWER_ON() and MEASURE_LOW_POWER_OFF() [these are called in the fnLowPower() task and defined in app_hw_xxxx.h].
By monitoring the output you can see when the processor is sleeping and when it is working due to scheduling in progress.
Although it is seen when the scheduling runs due to interrupts, the actual interrupts are not visible. By adding other outputs in individual IRQs, or by using a code on several port bits it is then possible to monitor exactly when the CPU was scheduling, handling interrupts within a certain period of time. A logical analyser can capture this over this period and allow accurate analysis of the load and any critically long individual interrupt routines.
Regards
Mark