From: Stefano Garzarella <sgarzare@redhat.com>
To: "Jiang Wang ." <jiang.wang@bytedance.com>
Cc: cong.wang@bytedance.com,
Xiongchun Duan <duanxiongchun@bytedance.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
cohuck@redhat.com, virtualization@lists.linux-foundation.org,
xieyongji@bytedance.com, Stefan Hajnoczi <stefanha@redhat.com>,
Arseny Krasnov <arseny.krasnov@kaspersky.com>
Subject: Re: [RFC v2] virtio-vsock: add description for datagram type
Date: Fri, 14 May 2021 17:17:01 +0200 [thread overview]
Message-ID: <20210514151701.6fp27qanjseom4tl@steredhat> (raw)
In-Reply-To: <CAP_N_Z94Pi4k8Dv6cHR0CZ9RTLJeQ3VWQoQgLTCWE4k+A01xbg@mail.gmail.com>
On Thu, May 13, 2021 at 04:26:03PM -0700, Jiang Wang . wrote:
>On Mon, May 10, 2021 at 7:52 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>> On Fri, May 07, 2021 at 09:53:19AM -0700, Jiang Wang . wrote:
[...]
>I was thinking if we don't add two new virtqueues, then maybe we don't
>need to add new feature bit too? If the other end does not support
>dgram, then the packets will be just dropped. What do you think? Do
>we still need to add dgram feature bits? I can have a feature bit for
>mergeable buffer.
With seqpacket, where we reuse stream queues, we decided to add the new
feature bit, so I guess we should do the same for dgram.
In this way the driver knows if the protocol is supported and we can
avoid for example to open a listening socket.
Without the feature bit this would not be possible. I mean, the sender
will get an error, but the receiver will never know if it can receive or
not.
>> >What do you guys think? I remember Stefano mentioned that we should
>> >add
>> >two new virtqueues for dgram. Stefano, do you have some specific reasons
>> >for that? Could we just keep using existing virtqueues? Thanks.
>>
>> My biggest concern was about the credit mechanism for datagrams. I mean
>> avoiding datagrams from crowding the queue without limits, preventing
>> streams from communicating.
>>
>> If you've found a way to limit datagram traffic, then maybe it's doable.
>
>I see. I will add some limit to dgram packets. Also, when the virtqueues
>are shared between stream and dgram, both of them need to grab a lock
>before using the virtqueue, so one will not completely block another one.
I'm not worried about the concurrent access that we definitely need to
handle with a lock, but more about the uncontrolled packet sending that
dgram might have, flooding the queues and preventing others from
communicating.
So having 2 dedicated queues could avoid a credit mechanism at all for
connection-less sockets, and simply the receiver discards packets that
it can't handle.
Thanks,
Stefano
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next prev parent reply other threads:[~2021-05-14 15:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 4:36 [RFC v2] virtio-vsock: add description for datagram type jiang.wang
2021-04-12 13:50 ` Stefan Hajnoczi
2021-04-12 14:21 ` Stefano Garzarella
2021-04-12 22:42 ` Jiang Wang .
2021-04-13 12:58 ` Stefano Garzarella
2021-04-13 13:16 ` Michael S. Tsirkin
2021-04-13 13:38 ` Stefano Garzarella
2021-04-13 13:50 ` Michael S. Tsirkin
2021-04-13 14:03 ` Stefano Garzarella
2021-04-13 19:58 ` Michael S. Tsirkin
2021-04-13 22:00 ` Jiang Wang .
2021-04-14 7:07 ` Stefano Garzarella
2021-04-14 6:57 ` Stefano Garzarella
2021-04-14 7:20 ` Michael S. Tsirkin
2021-04-14 9:38 ` Stefano Garzarella
2021-04-15 3:15 ` Jiang Wang .
2021-05-04 3:40 ` Jiang Wang .
2021-05-04 16:16 ` Stefano Garzarella
2021-05-04 17:06 ` Jiang Wang .
2021-05-05 10:49 ` Stefano Garzarella
2021-05-05 16:58 ` Jiang Wang .
2021-05-07 16:53 ` Jiang Wang .
2021-05-10 14:50 ` Stefano Garzarella
2021-05-13 23:26 ` Jiang Wang .
2021-05-14 15:17 ` Stefano Garzarella [this message]
2021-05-14 18:55 ` Jiang Wang .
2021-05-17 11:02 ` Stefano Garzarella
2021-05-18 6:33 ` Jiang Wang .
2021-05-18 13:02 ` Stefano Garzarella
2021-05-19 4:59 ` Jiang Wang .
2021-06-09 4:31 ` Jiang Wang .
2021-06-09 7:40 ` Stefano Garzarella
2021-04-12 22:39 ` [External] " Jiang Wang .
2021-05-13 14:57 ` Stefan Hajnoczi
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