Cache Test

test2.c

//gcc -DPAD=0 -o test2_0 test2.c -lpthread;time ./test2_0 -- 6.5s
//gcc -DPAD=0x0C38 -o test2_0C38 test2.c -lpthread;time ./test2_0C38  -- 15s

#include <stdio.h>
#include <pthread.h>
#include <sys/time.h>

// very suprise, when PAD = 0x0C38, the speed is slow down
typedef struct _Block
{
        unsigned char pad1[PAD];
        unsigned int flag1;
#ifdef CacheLinePadding
        long int padding[8];
#endif
        unsigned int flag2;
} Block;

Block block __attribute__((aligned(0x1000)));

unsigned LOOP = 0x80000000;

void MyThread(unsigned int* arg)
{
        struct timeval oStart1, oEnd1;
        gettimeofday( &oStart1 , NULL );
        while( *arg < LOOP) {
                (*arg)++;
        }
        gettimeofday( &oEnd1 , NULL );
        printf("arg = %p, used time:%lums\n", arg, (oEnd1.tv_sec-oStart1.tv_sec)*1000 + (oEnd1.tv_usec-oStart1.tv_usec) / 1000);
        //printf("used time:%lums\n", (oEnd1.tv_sec-oStart1.tv_sec)*1000 + (oEnd1.tv_usec-oStart1.tv_usec) / 1000);
}

int main(int argc, char **argv)
{
        pthread_t tid[2];

        printf("block = %p size = %d\n", &block, sizeof(block));
        block.flag1 = block.flag2 = 0;
        MyThread( &block.flag1);

        printf("\nrunning 2 thread now\n");

        block.flag1 = block.flag2 = 0;
        pthread_create( &tid[0], NULL, (void*)MyThread, &block.flag1);
        pthread_create( &tid[1], NULL, (void*)MyThread, &block.flag2);

        pthread_join(tid[0], NULL);
        pthread_join(tid[1], NULL);

        return 0;
}