l1_l2_cache_size.cpp

// Program to calculate L1 / L2 cache size, compile in g++ -O1
// Platform : Intel Xeon(R) CPU E5-2667 0 @ 2.90GHz
// OS: Ubuntu 12.04
// Author : Yancy Chien

#include <iostream>
#include <string>
#include <sys/time.h>
#include <cstdlib>
using namespace std;

#define CACHE_LINE_SIZE (64)  // set to correct to mutiply the difference
#define ARRAY_SIZE  (128 * 1024 * 1024) // arbitary array size, must in 2^N to let module work

void access_array(char* arr, unsigned size)
{
    const int loop_cnt = 64 * 1024 * 1024;
    for (int i = 0; i < LOOP_CNT; i++)
    {
        arr[(i * CACHE_LINE_SIZE) & (size - 1)] += 10;
    }
}

int main(int argc, char** argv){
    double cpu_us_used;
    struct timeval  start, end;
    
    for(int size = CACHE_LINE_SIZE * 2 ; size <= ARRAY_SIZE ; size *= 2){
        char* arr = new char[size];
        
        gettimeofday(&start, NULL); // get start clock
        
        access_array(arr, size);
        
        gettimeofday(&end, NULL);   // get end clock
        
        cpu_us_used = 1000000 * (end.tv_sec - start.tv_sec) + (end.tv_usec - start.tv_usec);
          
        cout << size << " , " << cpu_us_used << endl;
        
        delete[] arr;
    }
    return 0;
}