208.5日問題に関連してLinuxでrdtscを出力してみるサンプル gcc -o print_tsc print_tsc.c rdtscの値/(cps...一秒あたりのクロック数*60*60*24)で起動からの日数を概算

print_tsc.c

#include "rdtsc.h"
#include <stdio.h>

int main(void)
{
    unsigned long long start = rdtsc();
    printf("start time [clock] : %llu\n", start );

    int n = 5;

    unsigned long long looplog =rdtsc();
    while (n--) {
      sleep(1);
      unsigned long long loop = rdtsc();
      printf("check time [clock] : %llu\n", loop );
      printf("       cps [clock] : %llu\n", loop - looplog );
      looplog = loop;
    }

    unsigned long long stop = rdtsc();
    printf("stop  time [clock] : %llu\n", stop );

    printf("total time [clock] : %llu\n", stop - start);

    return 0;
}

rdtsc.h

#ifndef RDTSC_H_
#define RDTSC_H_

inline unsigned long long rdtsc() {
    unsigned long long ret;

    __asm__ __volatile__ ("cpuid" : : : "rax", "rbx", "rcx", "rdx");
    __asm__ __volatile__ ( \
        "rdtsc\n\t" \
        "shlq       $32, %%rdx\n\t" \
        "orq        %%rdx, %%rax\n\t" \
        "movq       %%rax, %0" : "=g" (ret) : : "rax", "rdx");
    
    return ret;
}

#endif /* RDTSC_H_ */