我們知道nginx中有l(wèi)ibaio這項功能，為了研究AIO的一些常用接口用法，在網(wǎng)上找到一個例子，異步IO讀取本地文件，親自實踐了一把，記錄如下：

安裝依賴庫

在Ubuntu 16.04上需要事先安裝 apt-cache search aio
sudo apt-get install libaio1 libaio-dev
如果是CentOS，需要執(zhí)行下面的命令先查詢再安裝 yum search libaio yum -y install libaio libaio-devel
下面時源碼例子

//description: 測試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>//為簡單起見，需要事先從網(wǎng)上下載一個文件，并存放在當(dāng)前目錄下面，
//并設(shè)置它的大小，這里選擇”http://news.sohu.com/“，存為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  1024struct 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;}//打開本地測試文件fd = open(TEST_FILE, O_RDWR | O_CREAT | O_DIRECT, 0644);if (fd == -1){perror("open");return 3;}//截斷到指定大小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;
}

下面是演示結(jié)果

參考文獻(xiàn)

http://blog.chinaunix.net/uid-16979052-id-3840266.html

總結(jié)

以上是生活随笔為你收集整理的在Ubuntu 16.04.1 LTS上测试Linux AIO功能实录的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。