linux rdtsc 纳秒级计时

部分代码

unsigned int ts,te;
unsigned int sdx,edx;
unsigned long long int clock_cycles;
unsigned int max=1<<31;
unsigned long long int max0=(unsigned long long int )max*2;

__asm__ __volatile__(
"rdtsc\n\t"
:"=a"(ts),"=d"(sdx));

//-------------some functions need to record time-----------//
b

__asm__ __volatile__(
"rdtsc\n\t"
:"=a"(te),"=d"(edx));


printf("tick ax start =%u tick end=%u \n",ts, te);
printf("tick dx start =%u tick end=%u \n",sdx, edx);
clock_cycles=(unsigned long long)(edx-sdx)*max0 te-ts;
//or clock_cycles=(unsigned long long)(edx-sdx)*0x0100000000l+ te-ts;
printf("ticks=%llu\n",clock_cycles);