#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#define NPAD (64 - sizeof(void *))
#define ACCESSES (1 << 28)


inline void
clflush(volatile void *p)
{
    asm volatile ("clflush (%0)" :: "r"(p));
}

inline uint64_t
rdtsc()
{
    unsigned long a, d;
    asm volatile ("cpuid; rdtsc" : "=a" (a), "=d" (d) : : "ebx", "ecx");
    return a | ((uint64_t)d << 32);
}


struct l
{
    l    *next;
    char pad[NPAD];
};


l array[ (1 << 26) / sizeof(l) ];


void init_sequential(int bytes)
{
    int elems = bytes / sizeof(l);

    for (int i = 1; i < elems; i++)
    {
        array[i - 1].next = &array[i];
    }

    array[elems - 1].next = &array[0];
}

void measure_baseline( int accesses )
{
    volatile l *ptr = &array[0];

    while (accesses-- > 0)
        ptr = ptr->next;
}


int rangeArr[] = {16, 32, 64, 128, 256, 512, 1024, 2048, 3072, 4096, 6144, 8192, 10240, 12*1024, 14*1024, 16*1024};

inline void test()
{
    for (int i = 0; i < sizeof(rangeArr) / sizeof(rangeArr[0]); i++)
    {
        uint64_t start, end;
        int kilobytes = rangeArr[i];

        init_sequential( kilobytes * 1024 );

        start = rdtsc();
        measure_baseline( ACCESSES );
        end = rdtsc();
        double ticksPerAccess = 1.0 * (end - start) / ACCESSES;
        printf("%d kB took %lf ticks per access\n", kilobytes, ticksPerAccess);
    }
}

int
main(int ac, char **av)
{
    test();
    return 0;
}