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Mon, 28 Sep 2026 08:00:21 -0700 (PDT) X-Received: by 2002:a05:6000:4b0a:b0:488:823d:507b with SMTP id ffacd0b85a97d-488823d5296mr15209714f8f.52.1790607620571; Mon, 28 Sep 2026 08:00:20 -0700 (PDT) Received: from sgarzare-redhat ([5.179.146.191]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4887a349731sm28558683f8f.12.2026.09.28.08.00.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 08:00:19 -0700 (PDT) Date: Mon, 28 Sep 2026 17:00:12 +0200 From: Stefano Garzarella To: David Carlier Cc: netdev@vger.kernel.org, bobbyeshleman@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2 1/2] vsock: report pending receive data to io_uring Message-ID: References: <20260923184008.153541-1-devnexen@gmail.com> <20260923184008.153541-2-devnexen@gmail.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260923184008.153541-2-devnexen@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 3dd9RwBZdwwlrOtID9njKOmMCOUCkIZ9_E-aFzoNIu8_1790607621 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 > --- > 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 > + * 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 >