Measure time in NIOS application

[ZVere]

Hello,

I used the following code to measure 1usec in baremetal NIOS application. 

PERF_RESET (NIOS_PERFORMANCE_COUNTER_BASE);
PERF_START_MEASURING (NIOS_PERFORMANCE_COUNTER_BASE);
PERF_BEGIN (NIOS_PERFORMANCE_COUNTER_BASE,MY_PERF_ID);
usleep (1);
PERF_END (NIOS_PERFORMANCE_COUNTER_BASE,MY_PERF_ID);
time = perf_get_section_time (NIOS_PERFORMANCE_COUNTER_BASE, MY_PERF_ID);

 But according to the clock value, the time is ~2usec, not ~1. 

Can you please tell what is wrong in my code ?

Thank you in advance,

Zvika 

[EricMunYew_C_Intel]

The return value is clock cycle, not usec.

2 means your measured result is 2 clock cycles.

[ZVere]

Hello,

I'm aware the time is measured in clocks. 

After converting clocks to usec, the measured time is ~2usec. 

But the delay is exactly 1usec ( usleep(1) )

Is there an alternative for measuring the clock cycles ?

Thank you,

Zvika 

[EricMunYew_C_Intel]

Your code is measuring the number of clock cycles to finish execute usleep(1), not measuring the delay.

[ZVere]

Hello,

Thank you for your reply.

How can I measure exactly the time a specified code is running ? (in clocks) 

For example: If the code is usleep (1), I expect that NofClocks * Frequency ~ 1usec

Best regards,

Zvika 

[EricMunYew_C_Intel]

You may refer to Nios profiling below.

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/an/an391.pdf