From b3fdea6ecb55c3ceea866ff66486927e51a982b3 Mon Sep 17 00:00:00 2001 From: Dylan Yudaken Date: Thu, 30 Jun 2022 02:12:29 -0700 Subject: [PATCH] io_uring: multishot recv Support multishot receive for io_uring. Typical server applications will run a loop where for each recv CQE it requeues another recv/recvmsg. This can be simplified by using the existing multishot functionality combined with io_uring's provided buffers. The API is to add the IORING_RECV_MULTISHOT flag to the SQE. CQEs will then be posted (with IORING_CQE_F_MORE flag set) when data is available and is read. Once an error occurs or the socket ends, the multishot will be removed and a completion without IORING_CQE_F_MORE will be posted. The benefit to this is that the recv is much more performant. * Subsequent receives are queued up straight away without requiring the application to finish a processing loop. * If there are more data in the socket (sat the provided buffer size is smaller than the socket buffer) then the data is immediately returned, improving batching. * Poll is only armed once and reused, saving CPU cycles Signed-off-by: Dylan Yudaken Link: https://lore.kernel.org/r/20220630091231.1456789-11-dylany@fb.com Signed-off-by: Jens Axboe --- include/uapi/linux/io_uring.h | 5 ++ io_uring/net.c | 102 +++++++++++++++++++++++++++++----- 2 files changed, 94 insertions(+), 13 deletions(-) diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index cf95354198a3..499679134961 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -263,8 +263,13 @@ enum io_uring_op { * or receive and arm poll if that yields an * -EAGAIN result, arm poll upfront and skip * the initial transfer attempt. + * + * IORING_RECV_MULTISHOT Multishot recv. Sets IORING_CQE_F_MORE if + * the handler will continue to report + * CQEs on behalf of the same SQE. */ #define IORING_RECVSEND_POLL_FIRST (1U << 0) +#define IORING_RECV_MULTISHOT (1U << 1) /* * accept flags stored in sqe->ioprio diff --git a/io_uring/net.c b/io_uring/net.c index e1eaf902f3b2..cb08a4b62840 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -389,6 +389,8 @@ int io_recvmsg_prep_async(struct io_kiocb *req) return ret; } +#define RECVMSG_FLAGS (IORING_RECVSEND_POLL_FIRST | IORING_RECV_MULTISHOT) + int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) { struct io_sr_msg *sr = io_kiocb_to_cmd(req); @@ -399,13 +401,22 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr)); sr->len = READ_ONCE(sqe->len); sr->flags = READ_ONCE(sqe->ioprio); - if (sr->flags & ~IORING_RECVSEND_POLL_FIRST) + if (sr->flags & ~(RECVMSG_FLAGS)) return -EINVAL; sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL; if (sr->msg_flags & MSG_DONTWAIT) req->flags |= REQ_F_NOWAIT; if (sr->msg_flags & MSG_ERRQUEUE) req->flags |= REQ_F_CLEAR_POLLIN; + if (sr->flags & IORING_RECV_MULTISHOT) { + if (!(req->flags & REQ_F_BUFFER_SELECT)) + return -EINVAL; + if (sr->msg_flags & MSG_WAITALL) + return -EINVAL; + if (req->opcode == IORING_OP_RECV && sr->len) + return -EINVAL; + req->flags |= REQ_F_APOLL_MULTISHOT; + } #ifdef CONFIG_COMPAT if (req->ctx->compat) @@ -415,6 +426,48 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) return 0; } +static inline void io_recv_prep_retry(struct io_kiocb *req) +{ + struct io_sr_msg *sr = io_kiocb_to_cmd(req); + + sr->done_io = 0; + sr->len = 0; /* get from the provided buffer */ +} + +/* + * Finishes io_recv and io_recvmsg. + * + * Returns true if it is actually finished, or false if it should run + * again (for multishot). + */ +static inline bool io_recv_finish(struct io_kiocb *req, int *ret, unsigned int cflags) +{ + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) { + io_req_set_res(req, *ret, cflags); + *ret = IOU_OK; + return true; + } + + if (*ret > 0) { + if (io_post_aux_cqe(req->ctx, req->cqe.user_data, *ret, + cflags | IORING_CQE_F_MORE, false)) { + io_recv_prep_retry(req); + return false; + } + /* + * Otherwise stop multishot but use the current result. + * Probably will end up going into overflow, but this means + * we cannot trust the ordering anymore + */ + } + + io_req_set_res(req, *ret, cflags); + + if (req->flags & REQ_F_POLLED) + *ret = IOU_STOP_MULTISHOT; + return true; +} + int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) { struct io_sr_msg *sr = io_kiocb_to_cmd(req); @@ -424,6 +477,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) unsigned flags; int ret, min_ret = 0; bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; + size_t len = sr->len; sock = sock_from_file(req->file); if (unlikely(!sock)) @@ -442,16 +496,17 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) (sr->flags & IORING_RECVSEND_POLL_FIRST)) return io_setup_async_msg(req, kmsg); +retry_multishot: if (io_do_buffer_select(req)) { void __user *buf; - buf = io_buffer_select(req, &sr->len, issue_flags); + buf = io_buffer_select(req, &len, issue_flags); if (!buf) return -ENOBUFS; kmsg->fast_iov[0].iov_base = buf; - kmsg->fast_iov[0].iov_len = sr->len; + kmsg->fast_iov[0].iov_len = len; iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->fast_iov, 1, - sr->len); + len); } flags = sr->msg_flags; @@ -463,8 +518,15 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) kmsg->msg.msg_get_inq = 1; ret = __sys_recvmsg_sock(sock, &kmsg->msg, sr->umsg, kmsg->uaddr, flags); if (ret < min_ret) { - if (ret == -EAGAIN && force_nonblock) - return io_setup_async_msg(req, kmsg); + if (ret == -EAGAIN && force_nonblock) { + ret = io_setup_async_msg(req, kmsg); + if (ret == -EAGAIN && (req->flags & IO_APOLL_MULTI_POLLED) == + IO_APOLL_MULTI_POLLED) { + io_kbuf_recycle(req, issue_flags); + return IOU_ISSUE_SKIP_COMPLETE; + } + return ret; + } if (ret == -ERESTARTSYS) ret = -EINTR; if (ret > 0 && io_net_retry(sock, flags)) { @@ -491,8 +553,11 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) cflags = io_put_kbuf(req, issue_flags); if (kmsg->msg.msg_inq) cflags |= IORING_CQE_F_SOCK_NONEMPTY; - io_req_set_res(req, ret, cflags); - return IOU_OK; + + if (!io_recv_finish(req, &ret, cflags)) + goto retry_multishot; + + return ret; } int io_recv(struct io_kiocb *req, unsigned int issue_flags) @@ -505,6 +570,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags) unsigned flags; int ret, min_ret = 0; bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; + size_t len = sr->len; if (!(req->flags & REQ_F_POLLED) && (sr->flags & IORING_RECVSEND_POLL_FIRST)) @@ -514,16 +580,17 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags) if (unlikely(!sock)) return -ENOTSOCK; +retry_multishot: if (io_do_buffer_select(req)) { void __user *buf; - buf = io_buffer_select(req, &sr->len, issue_flags); + buf = io_buffer_select(req, &len, issue_flags); if (!buf) return -ENOBUFS; sr->buf = buf; } - ret = import_single_range(READ, sr->buf, sr->len, &iov, &msg.msg_iter); + ret = import_single_range(READ, sr->buf, len, &iov, &msg.msg_iter); if (unlikely(ret)) goto out_free; @@ -543,8 +610,14 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags) ret = sock_recvmsg(sock, &msg, flags); if (ret < min_ret) { - if (ret == -EAGAIN && force_nonblock) + if (ret == -EAGAIN && force_nonblock) { + if ((req->flags & IO_APOLL_MULTI_POLLED) == IO_APOLL_MULTI_POLLED) { + io_kbuf_recycle(req, issue_flags); + return IOU_ISSUE_SKIP_COMPLETE; + } + return -EAGAIN; + } if (ret == -ERESTARTSYS) ret = -EINTR; if (ret > 0 && io_net_retry(sock, flags)) { @@ -570,8 +643,11 @@ out_free: cflags = io_put_kbuf(req, issue_flags); if (msg.msg_inq) cflags |= IORING_CQE_F_SOCK_NONEMPTY; - io_req_set_res(req, ret, cflags); - return IOU_OK; + + if (!io_recv_finish(req, &ret, cflags)) + goto retry_multishot; + + return ret; } int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)