redis使用epoll

redis使用epoll的代码在ae_epoll.c文件中。

epoll_create：redis服务器在启动时，创建事件循环，调用epoll_create方法创建epoll实例。

static int aeApiCreate(aeEventLoop *eventLoop) {

    aeApiState *state = zmalloc(sizeof(aeApiState));

    if (!state) return -;

    state->events = zmalloc(sizeof(struct epoll_event)*eventLoop->setsize);

    if (!state->events) {

        zfree(state);

        return -;

    }

    state->epfd = epoll_create(); /* 1024 is just a hint for the kernel */

    if (state->epfd == -) {

        zfree(state->events);

        zfree(state);

        return -;

    }

    eventLoop->apidata = state;

    return ;

}

epoll_ctl：当有新的客户端连接时，把新的连接描述符注册到epoll实例。

static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {

    aeApiState *state = eventLoop->apidata;

    struct epoll_event ee = {}; /* avoid valgrind warning */

    /* If the fd was already monitored for some event, we need a MOD

     * operation. Otherwise we need an ADD operation. */

    int op = eventLoop->events[fd].mask == AE_NONE ?

            EPOLL_CTL_ADD : EPOLL_CTL_MOD;

    ee.events = ;

    mask |= eventLoop->events[fd].mask; /* Merge old events */

    if (mask & AE_READABLE) ee.events |= EPOLLIN;

    if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;

    ee.data.fd = fd;

    if (epoll_ctl(state->epfd,op,fd,&ee) == -) return -;

    return ;

}

epoll_wait：调用epoll_wait获取客户端产生的io事件。

static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {

    aeApiState *state = eventLoop->apidata;

    int retval, numevents = ;

    retval = epoll_wait(state->epfd,state->events,eventLoop->setsize,

            tvp ? (tvp->tv_sec* + tvp->tv_usec/) : -);

    if (retval > ) {

        int j;

        numevents = retval;

        for (j = ; j < numevents; j++) {

            int mask = ;

            struct epoll_event *e = state->events+j;

            if (e->events & EPOLLIN) mask |= AE_READABLE;

            if (e->events & EPOLLOUT) mask |= AE_WRITABLE;

            if (e->events & EPOLLERR) mask |= AE_WRITABLE;

            if (e->events & EPOLLHUP) mask |= AE_WRITABLE;

            eventLoop->fired[j].fd = e->data.fd;

            eventLoop->fired[j].mask = mask;

        }

    }

    return numevents;

}