cputime.h

#ifndef __CPUTIME_H__
#define __CPUTIME_H__ 1

#include <stdint.h>

/*
 * Performance counter access.
 *
 * NB: Relative cycle counts and difference between two
 *     cpu-timestamps are meaningful ONLY when run on the _same_ CPU.
 */
#if defined(__i386__)

static inline uint64_t sys_cpu_timestamp(void)
{
    uint64_t x;
    __asm__ volatile ("rdtsc" : "=A" (x));
    return x;
}

#elif defined(__x86_64__)


static inline uint64_t sys_cpu_timestamp(void)
{
    uint64_t res;
    uint32_t hi, lo;
    __asm__ __volatile__ ("rdtsc" : "=a"(lo), "=d"(hi));

    res = hi;
    return (res << 32) | lo;
}

#else

#error "I don't know how to get CPU cycle counter for this machine!"

#endif /* x86, x86_64 */

#endif /* __CPUTIME_H__ */