mmap和write性能对比

#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <string.h>


#define TIMER(val) do{
        struct timeval tm;
        gettimeofday(&tm, NULL);
        val = tm.tv_sec * 1000 + tm.tv_usec/1000;
}
while(0)

int i = 0;

int create_tmp_file()
{
        char dir[100] = "/tmp/mmap";
        char file[100] = {0};
        snprintf(file, 100, "%s/%d", dir, i);
        i++;

        int fd = open(file, O_RDWR | O_CREAT);
        if(fd<0)
        {
                printf("errorn");
                exit(1);
        }
        return fd;
}

int create_tmp_file2()
{
        char dir[100] = "/tmp/mmap";
        char file[100] = {0};
        snprintf(file, 100, "%s/%d", dir, i);
        i++;

        int fd = open(file, O_CREAT | O_RDWR | O_APPEND);
        if(fd<0)
        {
                printf("errorn");
                exit(1);
        }
        return fd;
}

char *mmap_fd(int fd, int size)
{
        if(lseek(fd, size-1, SEEK_SET)==-1)
                printf("lseek errorn");
        if(write(fd, "0", 1)!=1)
                printf("write errorn");
        //if(fsync(fd)==-1)
        // printf("fsync errorn");
        char *p = (char *) mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
        if(p==MAP_FAILED)
        {
                perror("mmap");
                exit(1);
        }
        return p;
}

int main()
{
        long starttime, endtime;
        starttime = endtime = 0;

        int size = 1024 * 5;
        int count = 1000;
        char test_string[1024] = "lkjklsdjffffffffffffffffffffffffffffaelkjklgjiowejklgjkljaskldj";
        int test_string_len = strlen(test_string);

        //1. test mmap
        TIMER(starttime);
        int fd = create_tmp_file();
        char *p = mmap_fd(fd, size);
        char *tmp_p = p;

        int j =0;
        int size_sum = 0;

        for(; j<count; j++)
        {
                size_sum += test_string_len;
                if(size_sum > size)
                {
                        close(fd);
                        munmap(p, size);
                        fd = create_tmp_file();
                        p = mmap_fd(fd, size);
                        size_sum = test_string_len;
                        tmp_p = p;
                }

                memcpy(tmp_p, test_string, test_string_len);
                tmp_p += test_string_len;
        }
        close(fd);
        munmap(p, size);
        TIMER(endtime);
        printf("mmap duration: %ldn", endtime - starttime);

        //2. write
        size_sum = 0;
        TIMER(starttime);
        fd = create_tmp_file2();
        for(j=0; j<count; j++)
        {
                size_sum += test_string_len;
                if(size_sum > size)
                {
                        close(fd);
                        fd = create_tmp_file2();
                        size_sum = test_string_len;
                }
                write(fd, test_string, test_string_len);
        }
        close(fd);
        TIMER(endtime);
        printf("batch write duration: %ldn", endtime - starttime);

        //3. write
        TIMER(starttime);
        for(j=0; j<count; j++)
        {
                fd = create_tmp_file();
                write(fd, test_string, test_string_len);
                close(fd);
        }
        TIMER(endtime);
        printf("loop write duration: %ldn", endtime - starttime);

        //4. buffer write
        size_sum = 0;
        TIMER(starttime);
        int index = 0;
        char tmp_buffer[size];
        fd = create_tmp_file2();
        for(j=0; j<count; j++)
        {
                size_sum += test_string_len;
                if(size_sum > size)
                {
                        write(fd, tmp_buffer, size_sum-test_string_len);
                        close(fd);
                        fd = create_tmp_file2();
                        size_sum = test_string_len;
                }

                strncpy(tmp_buffer+size_sum-test_string_len, test_string, test_string_len);
        }
        write(fd, tmp_buffer, size_sum-test_string_len);
        close(fd);
        TIMER(endtime);
        printf("buffer write duration: %ldn", endtime - starttime);

        return 0;
}

gcc mmap-test.c -o mmaptest
./mmaptest

result:
    mmap duration: 3
    batch write duration: 8
    loop write duration: 77
    buffer write duration: 3