FreeRtos Interrupt Handling Mechanisim on NiosII

Hi

I`m trying to perform a benchmark to get an idea how much overhead FreeRTOS brings when compared to Altera library,roughly.

For this purpose i have implemented two tests which uses timer interrupts.

Test 1: uses alt_alarm_start to start an alarm timer and toggles a output pin when alt_avalon_timer_sc_irq enters. And timeout_pulse is enabled in fgpda hw desing so I know when interrupt occurs and when its handled. Measuring via scope yields 2.02us

Test 2: uses xTimerCreate start an timer and toggles a output pin when alt_irq_handler enters. It`s being called from port_asm.S. And timeout_pulse is enabled in fgpda hw desing so I know when interrupt occurs and when its handled. Measuring via scope yields 1.27us

Problem is I would expect that test1 would have significant smaller delta when compared to Test2 due to FreeRTOS overhead but apparently results do indicate opposite. So I thought may be alt_irq_handler is too late to start of measurement.

Do you have any idea where are interrupts first handled when FreeRtos is present ?

Thanks in advance