Message-ID: <ufohkq4g3v6mzpmheftdac5rtuy36ocvc4mczuhwc6fv456kmh@kyttvegsdxva>
Date: Tue, 23 Jul 2024 16:38:33 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Amery Hung <ameryhung@...il.com>
Cc: stefanha@...hat.com, mst@...hat.com, jasowang@...hat.com, 
	xuanzhuo@...ux.alibaba.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org, 
	decui@...rosoft.com, bryantan@...are.com, vdasa@...are.com, pv-drivers@...are.com, 
	dan.carpenter@...aro.org, simon.horman@...igine.com, oxffffaa@...il.com, 
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	bpf@...r.kernel.org, bobby.eshleman@...edance.com, jiang.wang@...edance.com, 
	amery.hung@...edance.com, xiyou.wangcong@...il.com
Subject: Re: [RFC PATCH net-next v6 00/14] virtio/vsock: support datagrams

Hi Amery,

On Wed, Jul 10, 2024 at 09:25:41PM GMT, Amery Hung 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/

Cool! Thanks for restarting this work!

>
>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.

What are the main points where you would like an agreement?

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

What kind of optimization?

>
>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

Nice!

I have not tested because the series does not compile as has already 
been pointed out, I will test the next version.

>
>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.

So IIUC we are re-using the same virtqueues used by stream/seqpacket, 
right?

I did a fast review, there's something to fix, but it looks like this 
can work well, so I'd start to discuss virtio spec changes ASAP.

Thanks,
Stefano

>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>Signed-off-by: Amery Hung <amery.hung@...edance.com>
>---
>Changes in v6:
>- allow empty transport in datagram vsock
>- add empty transport checks in various paths
>- transport layer now saves source cid and port to control buffer of skb
>  to remove the dependency of transport in recvmsg()
>- fix virtio dgram_enqueue() by looking up the transport to be used when
>  using sendto(2)
>- fix skb memory leaks in two places
>- add dgram auto-bind test
>- Link to v5: https://lore.kernel.org/r/20230413-b4-vsock-dgram-v5-0-581bd37fdb26@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 (14):
>  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
>  test/vsock: add vsock dgram tests
>
> drivers/vhost/vsock.c                   |   62 +-
> include/linux/virtio_vsock.h            |    9 +-
> include/net/af_vsock.h                  |   24 +-
> include/uapi/linux/virtio_vsock.h       |    2 +
> net/vmw_vsock/af_vsock.c                |  343 ++++++--
> net/vmw_vsock/hyperv_transport.c        |   13 -
> net/vmw_vsock/virtio_transport.c        |   24 +-
> net/vmw_vsock/virtio_transport_common.c |  188 ++++-
> net/vmw_vsock/vmci_transport.c          |   61 +-
> net/vmw_vsock/vsock_loopback.c          |    9 +-
> tools/testing/vsock/util.c              |  177 +++-
> tools/testing/vsock/util.h              |   10 +
> tools/testing/vsock/vsock_test.c        | 1032 ++++++++++++++++++++---
> 13 files changed, 1638 insertions(+), 316 deletions(-)
>
>-- 
>2.20.1
>

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