线程上下文切换测试代码

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

int pipes[20][3];
char buffer[10];
int running = 1;

void inti()
{
    int i =20;
    while(i--)
    {
        if(pipe(pipes[i])<0)
            exit(1);
        pipes[i][2] = i;
    }
}

void distroy()
{
    int i =20;
    while(i--)
    {
        close(pipes[i][0]);
        close(pipes[i][1]);
    }
}

double self_test()
{
    int i =20000;
    struct timeval start, end;
    gettimeofday(&start, NULL);
    while(i--)
    {
        if(write(pipes[0][1],buffer,10)==-1)
            exit(1);
        read(pipes[0][0],buffer,10);
    }
    gettimeofday(&end, NULL);
    return (double)(1000000*(end.tv_sec-start.tv_sec)+ end.tv_usec-start.tv_usec)/20000;
}

void *_test(void *arg)
{
    int pos = ((int *)arg)[2];
    int in = pipes[pos][0];
    int to = pipes[(pos + 1)%20][1];
    while(running)
    {
        read(in,buffer,10);
        if(write(to,buffer,10)==-1)
            exit(1);
    }
}

double threading_test()
{
    int i = 20;
    struct timeval start, end;
    pthread_t tid;
    while(--i)
    {
        pthread_create(&tid,NULL,_test,(void *)pipes[i]);
    }
    i = 10000;
    gettimeofday(&start, NULL);
    while(i--)
    {
        if(write(pipes[1][1],buffer,10)==-1)
            exit(1);
        read(pipes[0][0],buffer,10);
    }
    gettimeofday(&end, NULL);
    running = 0;
    if(write(pipes[1][1],buffer,10)==-1)
        exit(1);
    return (double)(1000000*(end.tv_sec-start.tv_sec)+ end.tv_usec-start.tv_usec)/10000/20;
}


int main()
{
    inti();
    printf("%6.6f\n",self_test());
    printf("%6.6f\n",threading_test());
    distroy();
    exit(0);
}

-------------------------------------------------------------------------
Host                 OS  2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K  
                         ctxsw  ctxsw  ctxsw ctxsw  ctxsw   ctxsw   ctxsw  
--------- ------------- ------ ------ ------ ------ ------ ------- -------  
bjzw_46_7 Linux 2.6.32- 2.7800 2.7800 2.7000 4.3800 4.0400 4.75000 5.48000