On Wed, Sep 23, 2026 at 07:40:07PM +0100, David Carlier wrote: > AF_VSOCK stream receives never fill msghdr.msg_inq, so io_uring cannot set > IORING_CQE_F_SOCK_NONEMPTY and retries a multishot receive even after the > queue has been drained. > > Fill the hint at the common receive exit using the transport callback that > SIOCINQ already uses, and report 1 once the connection is finished so the > caller performs the receive which observes EOF, as TCP does after a FIN. > > A vsock loopback ping-pong with io_uring multishot receive drops entries > into __vsock_connectible_recvmsg from 1.97 to 1.00 per delivered message, > and receiver CPU time by about 3% (25 runs of 50000 messages, p=0.006). > > Signed-off-by: David Carlier <[email protected]> > --- > net/vmw_vsock/af_vsock.c | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c > index f840498b58af..20d6f9ca6a96 100644 > --- a/net/vmw_vsock/af_vsock.c > +++ b/net/vmw_vsock/af_vsock.c > @@ -2543,6 +2543,35 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, > struct msghdr *msg, > return err; > } > > +/* Bytes a following receive can consume, 1 if it would only see EOF, or -1 > + * if the transport cannot tell. > + * > + * Called under the socket lock after a nonnegative stream receive, so a NULL > + * transport implies SOCK_DONE. > + */ > +static int vsock_stream_inq_hint(struct sock *sk) > +{ > + struct vsock_sock *vsk = vsock_sk(sk); > + s64 data; > + > + if ((sk->sk_shutdown & RCV_SHUTDOWN) || !vsk->transport || > + (sock_flag(sk, SOCK_DONE) && sk->sk_state != TCP_ESTABLISHED)) > + return 1; > + > + data = vsock_stream_has_data(vsk); > + if (data < 0) > + return -1; > + if (data > 0) > + return min_t(s64, data, INT_MAX); > + > + /* Empty but finished: keep the caller reading so it sees EOF. */ > + if (sock_flag(sk, SOCK_DONE) || > + (READ_ONCE(vsk->peer_shutdown) & SEND_SHUTDOWN)) > + return 1; > + > + return 0; > +} > + > int > __vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t > len, > int flags) > @@ -2606,6 +2635,12 @@ __vsock_connectible_recvmsg(struct socket *sock, > struct msghdr *msg, size_t len, > err = __vsock_seqpacket_recvmsg(sk, msg, len, flags); > > out: > + /* Seqpacket has_data counts messages, while io_uring treats msg_inq as
Do you mean vsock_stream_has_data() on SOCK_SEQPACKET doesn't return bytes? IMO names are confusing, but it should return number of bytes, we should fix it, but of course not in this patch. LGTM: Reviewed-by: Stefano Garzarella <[email protected]> > + * a byte length when sizing retries, so only streams report a hint. > + */ > + if (msg->msg_get_inq && err >= 0 && sk->sk_type == SOCK_STREAM) > + msg->msg_inq = vsock_stream_inq_hint(sk); > + > release_sock(sk); > return err; > } > -- > 2.55.0 >
