在Ubuntu 16.04.1 LTS上测试Linux AIO功能实录

朴灿烈づ我的快乐病毒、 2022-06-09 08:12 319阅读 0赞

我们知道nginx中有libaio这项功能，为了研究AIO的一些常用接口用法，在网上找到一个例子，异步IO读取本地文件，亲自实践了一把，记录如下：

安装依赖库

在Ubuntu 16.04上需要事先安装

apt-cache search aio

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sudo apt-get install libaio1 libaio-dev

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如果是CentOS，需要执行下面的命令先查询再安装

yum search libaio

yum -y install libaio libaio-devel

下面时源码例子

//description: 测试Linux的原生AIO功能演示
    //refer: http://blog.chinaunix.net/uid-16979052-id-3840266.html
    //dependence:
    //  sudo apt-get install libaio1 libaio-dev (Ubuntu 16.04.1)
    //  yum -y install libaio libaio-devel (CentOS 6.x)
    //compile: gcc -g epoll_aio.c -o epoll_aio -laio
    //run: ./epoll_aio
    //
    
    #define _GNU_SOURCE
    #define __STDC_FORMAT_MACROS
    
    #include <stdio.h>
    #include <stdlib.h>
    #include <stdint.h>
    #include <unistd.h>
    #include <errno.h>
    #include <libaio.h>
    #include <sys/eventfd.h>
    #include <sys/epoll.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <inttypes.h>
    
    //为简单起见，需要事先从网上下载一个文件，并存放在当前目录下面，
    //并设置它的大小，这里选择”http://news.sohu.com/“，存为aio_sample.html
    #define TEST_FILE   "aio_sample.html"
    #define TEST_FILE_SIZE  239576
    
    #define NUM_EVENTS  128
    #define ALIGN_SIZE  512
    #define RD_WR_SIZE  1024
    
    struct custom_iocb {
        struct iocb iocb;
        int nth_request;
    };
    
    void
    aio_callback(io_context_t ctx, struct iocb *iocb, long res, long res2)
    {
        struct custom_iocb *iocbp = (struct custom_iocb *) iocb;
        printf
    	("nth_request: %d, request_type: %s, offset: %lld, length: %lu, res: %ld, res2: %ld\n",
    	 iocbp->nth_request,
    	 (iocb->aio_lio_opcode == IO_CMD_PREAD) ? "READ" : "WRITE",
    	 iocb->u.c.offset, iocb->u.c.nbytes, res, res2);
    }
    
    int
    main(int argc, char *argv[])
    {
        int efd, fd, epfd;
        io_context_t ctx;
        struct timespec tms;
        struct io_event events[NUM_EVENTS];
        struct custom_iocb iocbs[NUM_EVENTS];
        struct iocb *iocbps[NUM_EVENTS];
        struct custom_iocb *iocbp;
        struct epoll_event epevent;
        int i, j, r;
        void *buf;
    
        efd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
        if (efd == -1)
        {
    	perror("eventfd");
    	return 2;
        }
    
        //打开本地测试文件
        fd = open(TEST_FILE, O_RDWR | O_CREAT | O_DIRECT, 0644);
        if (fd == -1)
        {
    	perror("open");
    	return 3;
        }
        //截断到指定大小
        ftruncate(fd, TEST_FILE_SIZE);
    
        ctx = 0;
        if (io_setup(8192, &ctx))
        {
    	perror("io_setup");
    	return 4;
        }
    
        if (posix_memalign(&buf, ALIGN_SIZE, RD_WR_SIZE))
        {
    	perror("posix_memalign");
    	return 5;
        }
        printf("buf: %p\n", buf);
    
        for (i = 0, iocbp = iocbs; i < NUM_EVENTS; ++i, ++iocbp)
        {
    	iocbps[i] = &iocbp->iocb;
    	io_prep_pread(&iocbp->iocb, fd, buf, RD_WR_SIZE, i * RD_WR_SIZE);
    	io_set_eventfd(&iocbp->iocb, efd);
    	io_set_callback(&iocbp->iocb, aio_callback);
    	iocbp->nth_request = i + 1;
        }
    
        if (io_submit(ctx, NUM_EVENTS, iocbps) != NUM_EVENTS)
        {
    	perror("io_submit");
    	return 6;
        }
    
        epfd = epoll_create(1);
        if (epfd == -1)
        {
    	perror("epoll_create");
    	return 7;
        }
    
        epevent.events = EPOLLIN | EPOLLET;
        epevent.data.ptr = NULL;
        if (epoll_ctl(epfd, EPOLL_CTL_ADD, efd, &epevent))
        {
    	perror("epoll_ctl");
    	return 8;
        }
    
        i = 0;
        while (i < NUM_EVENTS)
        {
    	uint64_t finished_aio;
    
    	if (epoll_wait(epfd, &epevent, 1, -1) != 1)
    	{
    	    perror("epoll_wait");
    	    return 9;
    	}
    
    	if (read(efd, &finished_aio, sizeof (finished_aio)) !=
    	    sizeof (finished_aio))
    	{
    	    perror("read");
    	    return 10;
    	}
    
    	printf("finished io number: %" PRIu64 "\n", finished_aio);
    
    	while (finished_aio > 0)
    	{
    	    tms.tv_sec = 0;
    	    tms.tv_nsec = 0;
    	    r = io_getevents(ctx, 1, NUM_EVENTS, events, &tms);
    	    if (r > 0)
    	    {
    		for (j = 0; j < r; ++j)
    		{
    		    ((io_callback_t) (events[j].data)) (ctx, events[j].obj,
    							events[j].res,
    							events[j].res2);
    		}
    		i += r;
    		finished_aio -= r;
    	    }
    	}
        }
    
        close(epfd);
        free(buf);
        io_destroy(ctx);
        close(fd);
        close(efd);
        remove(TEST_FILE);
    
        return 0;
    }

下面是演示结果

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参考文献

[http://blog.chinaunix.net/uid-16979052-id-3840266.html][http_blog.chinaunix.net_uid-16979052-id-3840266.html]

[Center]: /images/20220609/1e4798249dbb42068bc8fcf2df1c409a.png
[Center 1]: /images/20220609/c46c9aa1ec514e80be6aa02504f112ab.png
[Center 2]: /images/20220609/36a62b690aa648c7bad6ba3f82019e67.png
[http_blog.chinaunix.net_uid-16979052-id-3840266.html]: http://blog.chinaunix.net/uid-16979052-id-3840266.html