Using "rdtsc" with gcc

Using the "rdtsc"

rdtsc is a time stamp counter that returns  the number of clock ticks from the time the system was last reset.
The rdtsc instruction returns the time stamp counter in EDX:EAX.

This instruction is useful when you want to measure the performance of a certain code or application in clock ticks, or compare the performance of two programs, which are too small to be counted in seconds.

Here is a sample C code that shows how you can make use of this instruction.



#include <stdlib.h> #include<stdio.h> #include <inttypes.h> #include<sys/time.h> #include<time.h> void example() { uint64_t tick1, tick2; //unsigned 64 bit quantity unsigned c,d; asm volatile("rdtsc" : "=a" (c), "=d" (d)); //assembly code running the instruction rdtsc tick1 = (((uint64_t)c) | (((uint64_t)d) << 32)); // calculating the tick value. printf("time %llu",tick1); }