国内重大新闻2021搜索引擎优化的名词解释

以下是参考的实现代码，IO_URING 操作必须要进行按页大小对齐（仅在O_DIRECT直接I/O下），不能是非对称的，一般大多数操作系统页大小为：4KB。

批量读取、writev 批量简写。 

                    static constexpr int MTU = ITap::Mtu;struct io_uring ring;memset(&ring, 0, sizeof(ring));struct iovec tun_write_iov_data[PPP_TUN_ENTRIES_PACKET_SIZE];Byte packets[PPP_TUN_ENTRIES_PACKET_SIZE][MTU];SsmtThreadLocalTls& tls = ssmt_tls_;tls.tun_write_iov_data = tun_write_iov_data;if (io_uring_queue_init(PPP_TUN_ENTRIES_PACKET_SIZE, &ring, 0) < 0) {Dispose();return false;}bool any = false;for (int i = 0; i < PPP_TUN_ENTRIES_PACKET_SIZE; i++) {struct io_uring_sqe* sqe = io_uring_get_sqe(&ring);if (NULL == sqe) {goto LABEL_exit;}io_uring_prep_read(sqe, tun_fd, packets[i], MTU, 0);sqe->user_data = (__u64)&packets[i][0];}io_uring_submit(&ring);while (!disposed_) {struct io_uring_cqe* cqes[PPP_TUN_ENTRIES_PACKET_SIZE];__u32 count = io_uring_peek_batch_cqe(&ring, cqes, PPP_TUN_ENTRIES_PACKET_SIZE);if (count == 0) {int err = io_uring_wait_cqe(&ring, &cqes[0]);if (err == -EINTR) {continue;}elif(err >= 0) {count = 1;}else {break;}}ssmt_tls_.tun_wirte_iov_size = 0;for (__u32 i = 0; i < count; i++) {struct io_uring_cqe* cqe = cqes[i];assert(NULL != cqe);Byte* packet = (Byte*)cqe->user_data;if (int bytes_transferred = cqe->res; bytes_transferred > 0) {PacketInputEventArgs e{ packet, bytes_transferred };tls.tun_fd_ = tun_fd;OnInput(e);}struct io_uring_sqe* sqe = io_uring_get_sqe(&ring);assert(NULL != sqe);io_uring_prep_read(sqe, tun_fd, packet, MTU, 0);sqe->user_data = (__u64)packet;io_uring_cqe_seen(&ring, cqe);}tls.tun_fd_ = -1;io_uring_submit(&ring);if (tls.tun_wirte_iov_size > 0) {int err = writev(tun_fd, tun_write_iov_data, tls.tun_wirte_iov_size);for (int i = 0; i < tls.tun_wirte_iov_size; i++) {struct iovec& iov = tls.tun_write_iov_data[i];Mfree(iov.iov_base);}tls.tun_wirte_iov_size = 0;if (err < 0) {break;}}}LABEL_exit:io_uring_queue_exit(&ring);Dispose();return any;

write 批量收集或超限写出：

        bool TapLinux::Output(const void* packet, int packet_size) noexcept {if (NULL == packet || packet_size < 1) {return false;}int disposed = disposed_.load();if (disposed != FALSE) {return false;}// https://man7.org/linux/man-pages/man2/write.2.htmlint tun = static_cast<int>(reinterpret_cast<std::intptr_t>(GetHandle()));if (Ssmt()) {SsmtThreadLocalTls& tls = ssmt_tls_;int fd = tls.tun_fd_;if (fd != -1) {tun = fd;#if defined(BOOST_ASIO_HAS_IO_URING)void* packet_copy = Malloc(packet_size);if (NULL == packet_copy) {return false;}struct iovec& iov = tls.tun_write_iov_data[tls.tun_wirte_iov_size++];memcpy(packet_copy, packet, packet_size);iov.iov_base = packet_copy;iov.iov_len = packet_size;if (tls.tun_wirte_iov_size >= PPP_TUN_ENTRIES_PACKET_SIZE) {int err = writev(fd, tls.tun_write_iov_data, tls.tun_wirte_iov_size);for (int i = 0; i < tls.tun_wirte_iov_size; i++) {struct iovec& iov = tls.tun_write_iov_data[i];Mfree(iov.iov_base);}tls.tun_wirte_iov_size = 0;if (err < 0) {return false;}}
#endif}}ssize_t bytes_transferred = ::write(tun, (void*)packet, (size_t)packet_size);return bytes_transferred > -1;}