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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c2aae33faf4sm173417566b.3.2026.09.23.11.40.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 11:40:10 -0700 (PDT) From: David Carlier To: netdev@vger.kernel.org Cc: sgarzare@redhat.com, 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, David Carlier Subject: [PATCH net-next v2 0/2] vsock: receive queue hint for io_uring Date: Wed, 23 Sep 2026 19:40:06 +0100 Message-ID: <20260923184008.153541-1-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit AF_VSOCK stream receives never fill msghdr.msg_inq. io_uring initialises the hint to -1 and treats that as "unknown", so it cannot set IORING_CQE_F_SOCK_NONEMPTY, and it speculatively retries a multishot receive after every completion, including when the queue is already empty. Patch 1 fills the hint at the common exit of __vsock_connectible_recvmsg(), reusing vsock_stream_has_data(), the transport callback that SIOCINQ already uses. Following tcp_inq_hint(), it reports a terminal hint of 1 once the connection is finished, so the caller still performs the receive that observes EOF. Patch 2 adds selftest coverage. Numbers come from a ping-pong over vsock loopback using io_uring multishot receive, 4 KiB messages, the queue drained between messages, with kernel receives counted by a kprobe. The baseline is the same tree with patch 1 reverted: entries per delivered message 1.97 -> 1.00 (5000 messages) receiver CPU time, median 1.640s -> 1.587s (-3.2%) receiver wall time, median 3.260s -> 3.183s (-2.4%) Timing is 25 runs of 50000 messages per kernel; CPU gives Mann-Whitney p=0.006, wall time does not separate from noise (p=0.12), as expected for a latency-bound workload. The hint is gated to SOCK_STREAM; seqpacket is untouched. SO_INQ and SCM_INQ are deliberately left out: they need their own per-socket state and ancillary-message semantics, and a byte-count contract would have to account for transports reporting less than the whole queue. That can follow. Testing: built and run under virtme-ng on loopback, where the new cases pass and vsock_test still passes 41 of 41 with a clean dmesg. Other transports were reviewed but not tested. Hyper-V reports the current packet rather than the whole queue and can return -EIO; an undercount only understates what is readable, and a negative result reports -1, the same "unknown" value io_uring presets. Changes in v2: - vsock: rename the helper to vsock_stream_inq_hint(), fold the NULL transport check into the finished check, drop the int cast, assign msg_inq directly, and document why only SOCK_STREAM reports a hint (Stefano) - vsock/test: move expect_res() to util.c, add uring to the SOCK_NONEMPTY helper name, skip instead of failing when SIOCINQ is not supported, and drop the redundant final barrier of the EOF test (Stefano) - vsock/test: queue two chunks before arming the multishot receive and check SOCK_NONEMPTY is set on the first completion and clear on the second, so the test fails without patch 1 (Bobby) - v1: https://lore.kernel.org/netdev/20260920194710.1114748-1-devnexen@gmail.com/ David Carlier (2): vsock: report pending receive data to io_uring vsock/test: cover receive queue hints net/vmw_vsock/af_vsock.c | 35 +++ tools/testing/vsock/util.c | 9 + tools/testing/vsock/util.h | 1 + tools/testing/vsock/vsock_uring_test.c | 391 +++++++++++++++++++++++++ 4 files changed, 436 insertions(+) base-commit: cea851523034d83dc61d882b1a6a3ad273480f7b -- 2.55.0