Current recv bundles are only supported for multishot receives, and
additionally they also always post at least 2 CQEs if more data is
available than what a buffer will hold. This happens because the initial
bundle recv will do a single buffer, and then do the rest of what is in
the socket as a followup receive. As shown in a test program, if 1k
buffers are available and 32k is available to receive in the socket,
you'd get the following completions:
bundle=1, mshot=0
cqe res 1024
cqe res 1024
[...]
cqe res 1024
bundle=1, mshot=1
cqe res 1024
cqe res 31744
where bundle=1 && mshot=0 will post 32 1k completions, and bundle=1 &&
mshot=1 will post a 1k completion and then a 31k completion.
To support bundle recv without multishot, it's possible to simply retry
the recv immediately and post a single completion, rather than split it
into two completions. With the below patch, the same test looks as
follows:
bundle=1, mshot=0
cqe res 32768
bundle=1, mshot=1
cqe res 32768
where mshot=0 works fine for bundles, and both of them post just a
single 32k completion rather than split it into separate completions.
Posting fewer completions is always a nice win, and not needing
multishot for proper bundle efficiency is nice for cases that can't
necessarily use multishot.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
diff --git a/io_uring/net.c b/io_uring/net.c
index 17852a6616ff..10344b3a6d89 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -76,6 +76,7 @@ struct io_sr_msg {
/* initialised and used only by !msg send variants */
u16 buf_group;
u16 buf_index;
+ bool retry;
void __user *msg_control;
/* used only for send zerocopy */
struct io_kiocb *notif;
@@ -187,6 +188,7 @@ static inline void io_mshot_prep_retry(struct io_kiocb *req,
req->flags &= ~REQ_F_BL_EMPTY;
sr->done_io = 0;
+ sr->retry = false;
sr->len = 0; /* get from the provided buffer */
req->buf_index = sr->buf_group;
}
@@ -402,6 +404,7 @@ int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
sr->done_io = 0;
+ sr->retry = false;
if (req->opcode != IORING_OP_SEND) {
if (sqe->addr2 || sqe->file_index)
@@ -785,6 +788,7 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
sr->done_io = 0;
+ sr->retry = false;
if (unlikely(sqe->file_index || sqe->addr2))
return -EINVAL;
@@ -833,6 +837,9 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return io_recvmsg_prep_setup(req);
}
+/* bits to clear in old and inherit in new cflags on bundle retry */
+#define CQE_F_MASK (IORING_CQE_F_SOCK_NONEMPTY|IORING_CQE_F_MORE)
+
/*
* Finishes io_recv and io_recvmsg.
*
@@ -852,9 +859,19 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret,
if (sr->flags & IORING_RECVSEND_BUNDLE) {
cflags |= io_put_kbufs(req, *ret, io_bundle_nbufs(kmsg, *ret),
issue_flags);
+ if (sr->retry)
+ cflags = req->cqe.flags | (cflags & CQE_F_MASK);
/* bundle with no more immediate buffers, we're done */
if (req->flags & REQ_F_BL_EMPTY)
goto finish;
+ /* if more is available, retry and append to this one */
+ if (!sr->retry && kmsg->msg.msg_inq > 0 && *ret > 0) {
+ req->cqe.flags = cflags & ~CQE_F_MASK;
+ sr->len = kmsg->msg.msg_inq;
+ sr->done_io += *ret;
+ sr->retry = true;
+ return false;
+ }
} else {
cflags |= io_put_kbuf(req, *ret, issue_flags);
}
@@ -1233,6 +1250,7 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
struct io_kiocb *notif;
zc->done_io = 0;
+ zc->retry = false;
req->flags |= REQ_F_POLL_NO_LAZY;
if (unlikely(READ_ONCE(sqe->__pad2[0]) || READ_ONCE(sqe->addr3)))
--
Jens Axboe
