Hey all! This series introduces support for datagrams to virtio/vsock. It is a spin-off (and smaller version) of this series from the summer: https://lore.kernel.org/all/cover.1660362668.git.bobby.eshleman@xxxxxxxxxxxxx/ Please note that this is an RFC and should not be merged until associated changes are made to the virtio specification, which will follow after discussion from this series. This series first supports datagrams in a basic form for virtio, and then optimizes the sendpath for all transports. The result is a very fast datagram communication protocol that outperforms even UDP on multi-queue virtio-net w/ vhost on a variety of multi-threaded workload samples. For those that are curious, some summary data comparing UDP and VSOCK DGRAM (N=5): vCPUS: 16 virtio-net queues: 16 payload size: 4KB Setup: bare metal + vm (non-nested) UDP: 287.59 MB/s VSOCK DGRAM: 509.2 MB/s Some notes about the implementation... This datagram implementation forces datagrams to self-throttle according to the threshold set by sk_sndbuf. It behaves similar to the credits used by streams in its effect on throughput and memory consumption, but it is not influenced by the receiving socket as credits are. The device drops packets silently. There is room for improvement by building into the device and driver some intelligence around how to reduce frequency of kicking the virtqueue when packet loss is high. I think there is a good discussion to be had on this. In this series I am also proposing that fairness be reexamined as an issue separate from datagrams, which differs from my previous series that coupled these issues. After further testing and reflection on the design, I do not believe that these need to be coupled and I do not believe this implementation introduces additional unfairness or exacerbates pre-existing unfairness. I attempted to characterize vsock fairness by using a pool of processes to stress test the shared resources while measuring the performance of a lone stream socket. Given unfair preference for datagrams, we would assume that a lone stream socket would degrade much more when a pool of datagram sockets was stressing the system than when a pool of stream sockets are stressing the system. The result, however, showed no significant difference between the degradation of throughput of the lone stream socket when using a pool of datagrams to stress the queue over using a pool of streams. The absolute difference in throughput actually favored datagrams as interfering least as the mean difference was +16% compared to using streams to stress test (N=7), but it was not statistically significant. Workloads were matched for payload size and buffer size (to approximate memory consumption) and process count, and stress workloads were configured to start before and last long after the lifetime of the "lone" stream socket flow to ensure that competing flows were continuously hot. Given the above data, I propose that vsock fairness be addressed independent of datagrams and to defer its implementation to a future series. Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx> --- Bobby Eshleman (3): virtio/vsock: support dgram virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit vsock: Add lockless sendmsg() support Jiang Wang (1): tests: add vsock dgram tests drivers/vhost/vsock.c | 17 +- include/net/af_vsock.h | 20 ++- include/uapi/linux/virtio_vsock.h | 2 + net/vmw_vsock/af_vsock.c | 287 ++++++++++++++++++++++++++++---- net/vmw_vsock/diag.c | 10 +- net/vmw_vsock/hyperv_transport.c | 15 +- net/vmw_vsock/virtio_transport.c | 10 +- net/vmw_vsock/virtio_transport_common.c | 221 ++++++++++++++++++++---- net/vmw_vsock/vmci_transport.c | 70 ++++++-- tools/testing/vsock/util.c | 105 ++++++++++++ tools/testing/vsock/util.h | 4 + tools/testing/vsock/vsock_test.c | 193 +++++++++++++++++++++ 12 files changed, 859 insertions(+), 95 deletions(-) --- base-commit: ed72bd5a6790a0c3747cb32b0427f921bd03bb71 change-id: 20230413-b4-vsock-dgram-3b6eba6a64e5 Best regards, -- Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
