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ep:labs:07:contents:tasks:ex2 [2025/05/05 00:38] radu.mantu |
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| Add a [[https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html|destructor]] to the instrumentation callback library in which you will display these statistics when the program terminates. | Add a [[https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html|destructor]] to the instrumentation callback library in which you will display these statistics when the program terminates. | ||
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| + | <note tip> | ||
| + | If you are working natively on Linux, consider using the **rdtsc** macro from ''util.h''. This is a wrapper over the [[https://www.felixcloutier.com/x86/rdtsc|RDTSC]] instruction and it's the most efficient method of calculating the elapsed time. You can find a usage example [[https://github.com/RaduMantu/tsn-keysight/blob/master/src/slice.c#L22|here]]. Keep in mind that your CPU increments this timestamp counter a fixed number of times per second. This frequency is also the //base frequency// of your CPU. You can find it expressed in kHz in ''/sys/devices/system/cpu/cpu0/cpufreq/base_frequency''. | ||
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| + | If you are working inside a VM or simply don't want to use **rdtsc**, use [[https://linux.die.net/man/3/clock_gettime|clock_gettime()]] instead. Choose a //monotonic timer// that fits your needs. Check each timer's resolution and explain why it matters. | ||
| + | </note> | ||
