Re: [PATCH RFC net-next v5 00/14] virtio/vsock: support datagrams

Bobby Eshleman
2023-07-26T18:02:06Z

On Wed, Jul 19, 2023 at 12:50:04AM +0000, Bobby Eshleman wrote:
> 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@bytedance.com/
>
> 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.
>
> Another aside, the v4 of the series has only been mildly tested with a
> run of tools/testing/vsock/vsock_test. Some code likely needs cleaning
> up, but I'm hoping to get some of the design choices agreed upon before
> spending too much time making it pretty.

Stale from v4 cover, sorry.

>
> This series first supports datagrams in a basic form for virtio, and
> then optimizes the sendpath for all datagram 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

Also stale. After dropping the lockless sendpath patch and deferring it
to later, this data does not apply to the series anymore.

>
> 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.
>
> As discussed previously, this series introduces datagrams and defers
> fairness to future work. See discussion in v2 for more context around
> datagrams, fairness, and this implementation.
>
> Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
> ---
> Changes in v5:
> - teach vhost to drop dgram when a datagram exceeds the receive buffer
> - now uses MSG_ERRQUEUE and depends on Arseniy's zerocopy patch:
> "vsock: read from socket's error queue"
> - replace multiple ->dgram_* callbacks with single ->dgram_addr_init()
> callback
> - refactor virtio dgram skb allocator to reduce conflicts w/ zerocopy series
> - add _fallback/_FALLBACK suffix to dgram transport variables/macros
> - add WARN_ONCE() for table_size / VSOCK_HASH issue
> - add static to vsock_find_bound_socket_common
> - dedupe code in vsock_dgram_sendmsg() using module_got var
> - drop concurrent sendmsg() for dgram and defer to future series
> - Add more tests
> - test EHOSTUNREACH in errqueue
> - test stream + dgram address collision
> - improve clarity of dgram msg bounds test code
> - Link to v4: https://lore.kernel.org/r/20230413-b4-vsock-dgram-v4-0-0cebbb2ae899@bytedance.com
>
> Changes in v4:
> - style changes
> - vsock: use sk_vsock(vsk) in vsock_dgram_recvmsg instead of
> &sk->vsk
> - vsock: fix xmas tree declaration
> - vsock: fix spacing issues
> - virtio/vsock: virtio_transport_recv_dgram returns void because err
> unused
> - sparse analysis warnings/errors
> - virtio/vsock: fix unitialized skerr on destroy
> - virtio/vsock: fix uninitialized err var on goto out
> - vsock: fix declarations that need static
> - vsock: fix __rcu annotation order
> - bugs
> - vsock: fix null ptr in remote_info code
> - vsock/dgram: make transport_dgram a fallback instead of first
> priority
> - vsock: remove redundant rcu read lock acquire in getname()
> - tests
> - add more tests (message bounds and more)
> - add vsock_dgram_bind() helper
> - add vsock_dgram_connect() helper
>
> Changes in v3:
> - Support multi-transport dgram, changing logic in connect/bind
> to support VMCI case
> - Support per-pkt transport lookup for sendto() case
> - Fix dgram_allow() implementation
> - Fix dgram feature bit number (now it is 3)
> - Fix binding so dgram and connectible (cid,port) spaces are
> non-overlapping
> - RCU protect transport ptr so connect() calls never leave
> a lockless read of the transport and remote_addr are always
> in sync
> - Link to v2: https://lore.kernel.org/r/20230413-b4-vsock-dgram-v2-0-079cc7cee62e@bytedance.com
>
> ---
> Bobby Eshleman (13):
> af_vsock: generalize vsock_dgram_recvmsg() to all transports
> af_vsock: refactor transport lookup code
> af_vsock: support multi-transport datagrams
> af_vsock: generalize bind table functions
> af_vsock: use a separate dgram bind table
> virtio/vsock: add VIRTIO_VSOCK_TYPE_DGRAM
> virtio/vsock: add common datagram send path
> af_vsock: add vsock_find_bound_dgram_socket()
> virtio/vsock: add common datagram recv path
> virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit
> vhost/vsock: implement datagram support
> vsock/loopback: implement datagram support
> virtio/vsock: implement datagram support
>
> Jiang Wang (1):
> test/vsock: add vsock dgram tests
>
> drivers/vhost/vsock.c | 64 ++-
> include/linux/virtio_vsock.h | 10 +-
> include/net/af_vsock.h | 14 +-
> include/uapi/linux/virtio_vsock.h | 2 +
> net/vmw_vsock/af_vsock.c | 281 ++++++++++---
> net/vmw_vsock/hyperv_transport.c | 13 -
> net/vmw_vsock/virtio_transport.c | 26 +-
> net/vmw_vsock/virtio_transport_common.c | 190 +++++++--
> net/vmw_vsock/vmci_transport.c | 60 +--
> net/vmw_vsock/vsock_loopback.c | 10 +-
> tools/testing/vsock/util.c | 141 ++++++-
> tools/testing/vsock/util.h | 6 +
> tools/testing/vsock/vsock_test.c | 680 ++++++++++++++++++++++++++++++++
> 13 files changed, 1320 insertions(+), 177 deletions(-)
> ---
> base-commit: 37cadc266ebdc7e3531111c2b3304fa01b2131e8
> change-id: 20230413-b4-vsock-dgram-3b6eba6a64e5
>
> Best regards,
> --
> Bobby Eshleman <bobby.eshleman@bytedance.com>
>