From: Stefano Garzarella <sgarzare@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Jiang Wang ." <jiang.wang@bytedance.com>,
virtualization@lists.linux-foundation.org,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Arseny Krasnov" <arseny.krasnov@kaspersky.com>,
jhansen@vmware.comments, cong.wang@bytedance.com,
"Xiongchun Duan" <duanxiongchun@bytedance.com>,
"Yongji Xie" <xieyongji@bytedance.com>,
柴稳 <chaiwen.cc@bytedance.com>,
"David S. Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Colin Ian King" <colin.king@canonical.com>,
"Jorgen Hansen" <jhansen@vmware.com>,
"Andra Paraschiv" <andraprs@amazon.com>,
"Norbert Slusarek" <nslusarek@gmx.net>,
"Lu Wei" <luwei32@huawei.com>,
"Alexander Popov" <alex.popov@linux.com>,
kvm@vger.kernel.org, Networking <netdev@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC v1 0/6] virtio/vsock: introduce SOCK_DGRAM support
Date: Thu, 10 Jun 2021 09:23:58 +0200 [thread overview]
Message-ID: <20210610072358.3fuvsahxec2sht4y@steredhat> (raw)
In-Reply-To: <ac0c241c-1013-1304-036f-504d0edc5fd7@redhat.com>
On Thu, Jun 10, 2021 at 12:02:35PM +0800, Jason Wang wrote:
>
>在 2021/6/10 上午11:43, Jiang Wang . 写道:
>>On Wed, Jun 9, 2021 at 6:51 PM Jason Wang <jasowang@redhat.com> wrote:
>>>
>>>在 2021/6/10 上午7:24, Jiang Wang 写道:
>>>>This patchset implements support of SOCK_DGRAM for virtio
>>>>transport.
>>>>
>>>>Datagram sockets are connectionless and unreliable. To avoid unfair contention
>>>>with stream and other sockets, add two more virtqueues and
>>>>a new feature bit to indicate if those two new queues exist or not.
>>>>
>>>>Dgram does not use the existing credit update mechanism for
>>>>stream sockets. When sending from the guest/driver, sending packets
>>>>synchronously, so the sender will get an error when the virtqueue is
>>>>full.
>>>>When sending from the host/device, send packets asynchronously
>>>>because the descriptor memory belongs to the corresponding QEMU
>>>>process.
>>>
>>>What's the use case for the datagram vsock?
>>>
>>One use case is for non critical info logging from the guest
>>to the host, such as the performance data of some applications.
>
>
>Anything that prevents you from using the stream socket?
>
>
>>
>>It can also be used to replace UDP communications between
>>the guest and the host.
>
>
>Any advantage for VSOCK in this case? Is it for performance (I guess
>not since I don't exepct vsock will be faster).
I think the general advantage to using vsock are for the guest agents
that potentially don't need any configuration.
>
>An obvious drawback is that it breaks the migration. Using UDP you can
>have a very rich features support from the kernel where vsock can't.
>
Thanks for bringing this up!
What features does UDP support and datagram on vsock could not support?
>
>>
>>>>The virtio spec patch is here:
>>>>https://www.spinics.net/lists/linux-virtualization/msg50027.html
>>>
>>>Have a quick glance, I suggest to split mergeable rx buffer into an
>>>separate patch.
>>Sure.
>>
>>>But I think it's time to revisit the idea of unifying the virtio-net
>>>and
>>>virtio-vsock. Otherwise we're duplicating features and bugs.
>>For mergeable rxbuf related code, I think a set of common helper
>>functions can be used by both virtio-net and virtio-vsock. For other
>>parts, that may not be very beneficial. I will think about more.
>>
>>If there is a previous email discussion about this topic, could you
>>send me
>>some links? I did a quick web search but did not find any related
>>info. Thanks.
>
>
>We had a lot:
>
>[1]
>https://patchwork.kernel.org/project/kvm/patch/5BDFF537.3050806@huawei.com/
>[2]
>https://lists.linuxfoundation.org/pipermail/virtualization/2018-November/039798.html
>[3] https://www.lkml.org/lkml/2020/1/16/2043
>
When I tried it, the biggest problem that blocked me were all the
features strictly related to TCP/IP stack and ethernet devices that
vsock device doesn't know how to handle: TSO, GSO, checksums, MAC, napi,
xdp, min ethernet frame size, MTU, etc.
So in my opinion to unify them is not so simple, because vsock is not
really an ethernet device, but simply a socket.
But I fully agree that we shouldn't duplicate functionality and code, so
maybe we could find those common parts and create helpers to be used by
both.
Thanks,
Stefano
next prev parent reply other threads:[~2021-06-10 7:24 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 23:24 [RFC v1 0/6] virtio/vsock: introduce SOCK_DGRAM support Jiang Wang
2021-06-09 23:24 ` [RFC v1 1/6] virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit Jiang Wang
2021-06-18 9:39 ` Stefano Garzarella
2021-06-21 17:24 ` [External] " Jiang Wang .
2021-06-22 10:50 ` Stefano Garzarella
2021-06-09 23:24 ` [RFC v1 2/6] virtio/vsock: add support for virtio datagram Jiang Wang
2021-06-18 9:52 ` Stefano Garzarella
2021-06-18 10:11 ` Stefano Garzarella
2021-06-09 23:24 ` [RFC v1 3/6] vhost/vsock: add support for vhost dgram Jiang Wang
2021-06-18 10:13 ` Stefano Garzarella
2021-06-21 17:32 ` [External] " Jiang Wang .
2021-06-09 23:24 ` [RFC v1 4/6] vsock_test: add tests for vsock dgram Jiang Wang
2021-06-09 23:24 ` [RFC v1 5/6] vhost/vsock: add kconfig for vhost dgram support Jiang Wang
2021-06-18 9:54 ` Stefano Garzarella
2021-06-21 17:25 ` [External] " Jiang Wang .
2021-06-09 23:24 ` [RFC v1 6/6] virtio/vsock: add sysfs for rx buf len for dgram Jiang Wang
2021-06-18 10:04 ` Stefano Garzarella
2021-06-21 17:27 ` [External] " Jiang Wang .
2021-06-10 1:50 ` [RFC v1 0/6] virtio/vsock: introduce SOCK_DGRAM support Jason Wang
2021-06-10 3:43 ` Jiang Wang .
2021-06-10 4:02 ` Jason Wang
2021-06-10 7:23 ` Stefano Garzarella [this message]
2021-06-10 7:46 ` Jason Wang
2021-06-10 9:51 ` Stefano Garzarella
2021-06-10 16:44 ` Jiang Wang .
2021-06-18 9:35 ` Stefano Garzarella
2021-06-21 17:21 ` [External] " Jiang Wang .
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