From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Ilya Maximets <i.maximets@ovn.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Cc: Chenbo Xia <chenbo.xia@intel.com>,
dev@dpdk.org, Adrian Moreno <amorenoz@redhat.com>,
Julia Suvorova <jusual@redhat.com>
Subject: Re: [dpdk-dev] [RFC 0/4] SocketPair Broker support for vhost and virtio-user.
Date: Wed, 24 Mar 2021 22:51:54 +0100 [thread overview]
Message-ID: <f92170bc-ee2f-c7c3-a2aa-fa4ed34d9bbe@redhat.com> (raw)
In-Reply-To: <d0534686-27f0-b56b-65d9-70a12e6d44d4@ovn.org>
On 3/24/21 10:39 PM, Ilya Maximets wrote:
> On 3/24/21 9:56 PM, Maxime Coquelin wrote:
>> Hi Ilya,
>>
>> On 3/19/21 5:45 PM, Ilya Maximets wrote:
>>> On 3/19/21 5:11 PM, Ilya Maximets wrote:
>>>> On 3/19/21 3:39 PM, Stefan Hajnoczi wrote:
>>>>> Hi Ilya,
>>>>> By the way, it's not clear to me why dpdkvhostuser is deprecated. If OVS
>>>>> is restarted then existing vhost-user connections drop with an error but
>>>>> QEMU could attempt to reconnect to the UNIX domain socket which the new
>>>>> OVS instance will set up.
>>>>>
>>>>> Why is it impossible to reconnect when OVS owns the listen socket?
>>>>
>>>> Well, AFAIK, qemu reconnects client connections only:
>>>>
>>>> ``reconnect`` sets the timeout for reconnecting on non-server
>>>> sockets when the remote end goes away. qemu will delay this many
>>>> seconds and then attempt to reconnect. Zero disables reconnecting,
>>>> and is the default.
>>>>
>>>> I'm not sure about exact reason. It was historically this way.
>>>> For me it doesn't make much sense. I mean, your right that it's
>>>> just a socket, so it should not matter who listens and who connects.
>>>> If reconnection is possible in one direction, it should be possible
>>>> in the opposite direction too.
>>>
>>> Sorry, my thought slipped. :) Yes, QEMU supports re-connection
>>> for client sockets. So, in theory, dpdkvhostuser ports should work
>>> after re-connection. And that would be nice. I don't remember
>>> right now why this doesn't work... Maybe vhost-user parts in QEMU
>>> doesn't handle this case. Need to dig some more into that and refresh
>>> my memory. It was so long ago...
>>>
>>> Maxime, do you remember?
>>
>> Sorry for the delay. I didn't remember, so I wanted to have a try.
>>
>> I can confirm reconnect works with QEMU as client and with Vhost PMD as
>> server with:
>>
>>
>> <interface type='vhostuser'>
>> <mac address='56:48:4f:53:54:01'/>
>> <source type='unix' path='/tmp/vhost-user1' mode='client'>
>> <reconnect enabled='yes' timeout='1'/>
>> </source>
>> <model type='virtio'/>
>> <driver name='vhost' rx_queue_size='256'/>
>> <address type='pci' domain='0x0000' bus='0x07' slot='0x00'
>> function='0x0'/>
>> </interface>
>
> Cool, thanks for checking. :)
> If it works with vhost PMD, it should probably work with OVS too.
>
> There is still a couple of problems:
>
> 1. OpenStack Nova doesn't support configuration of a 'reconnect'
> in libvirt xml (it only adds the 'source'):
> https://github.com/openstack/nova/blob/master/nova/virt/libvirt/config.py#L1834
>
> 2. 'reconnect' configuration supported only starting from libvirt 4.1.0.
> It's released in 2018, but still some systems are using older versions.
> e.g. Ubuntu 18.04 which will be supported until 2023 uses libvirt 4.0.0.
Is it really a problem? We can keep using OVS as client for OSP, and use
OVS as server for containers.
>>
>>>
>>>>
>>>> dpdkvhostuser was deprecated just to scare users and force them to
>>>> migrate to dpdkvhostuserclient and avoid constant bug reports like:
>>>>
>>>> "OVS service restarted and network is lost now".
>>>>
>>>> BTW, virtio-user ports in DPDK doesn't support re-connection in client
>>>> mode too.
>>>
>>> This is still true, though. virtio-user in client mode doesn't reconnect.
>>
>> That could be added, and it is maybe not as important for containers as
>> it is for VM to support it, given the ephemeral nature of containers?
>
> Well, restart of OVS should not require restarting of all the containers
> on the host even though they are "stateless".
>
> BTW, some infrastructure changes that I made in this series might be
> reused to implement client-side reconnection for virtio-user.
Great, I'll look at the series when we'll work on adding reconnect for
clients.
Thanks,
Maxime
>>
>> Regards,
>> Maxime
>>
>>>
>>>>
>>>> BTW2, with SocketPair Broker it might be cheaper to implement server
>>>> reconnection in QEMU because all connections in these case are client
>>>> connections, i.e. both ends will connect() to a broker.
>>>>
>>>> Bets regards, Ilya Maximets.
>>>>
>>>
>
next prev parent reply other threads:[~2021-03-24 21:53 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 20:25 Ilya Maximets
2021-03-17 20:25 ` [dpdk-dev] [PATCH 1/4] net/virtio: fix interrupt unregistering for listening socket Ilya Maximets
2021-03-25 8:32 ` Maxime Coquelin
2021-04-07 7:21 ` Xia, Chenbo
2021-03-17 20:25 ` [dpdk-dev] [RFC 2/4] vhost: add support for SocketPair Broker Ilya Maximets
2021-03-17 20:25 ` [dpdk-dev] [RFC 3/4] net/vhost: " Ilya Maximets
2021-03-17 20:25 ` [dpdk-dev] [RFC 4/4] net/virtio: " Ilya Maximets
2021-03-18 17:52 ` [dpdk-dev] [RFC 0/4] SocketPair Broker support for vhost and virtio-user Stefan Hajnoczi
2021-03-18 19:47 ` Ilya Maximets
2021-03-18 20:14 ` Ilya Maximets
2021-03-19 14:16 ` Stefan Hajnoczi
2021-03-19 15:37 ` Ilya Maximets
2021-03-19 16:01 ` Stefan Hajnoczi
2021-03-19 16:02 ` Marc-André Lureau
2021-03-19 8:51 ` Marc-André Lureau
2021-03-19 11:25 ` Ilya Maximets
2021-03-19 14:05 ` Stefan Hajnoczi
2021-03-19 15:29 ` Ilya Maximets
2021-03-19 17:21 ` Stefan Hajnoczi
2021-03-23 17:57 ` Adrian Moreno
2021-03-23 18:27 ` Ilya Maximets
2021-03-23 20:54 ` Billy McFall
2021-03-24 12:05 ` Stefan Hajnoczi
2021-03-24 13:11 ` Ilya Maximets
2021-03-24 15:07 ` Stefan Hajnoczi
2021-03-25 9:35 ` Stefan Hajnoczi
2021-03-25 11:00 ` Ilya Maximets
2021-03-25 16:43 ` Stefan Hajnoczi
2021-03-25 17:58 ` Ilya Maximets
2021-03-30 15:01 ` Stefan Hajnoczi
2021-03-19 14:39 ` Stefan Hajnoczi
2021-03-19 16:11 ` Ilya Maximets
2021-03-19 16:45 ` Ilya Maximets
2021-03-24 20:56 ` Maxime Coquelin
2021-03-24 21:39 ` Ilya Maximets
2021-03-24 21:51 ` Maxime Coquelin [this message]
2021-03-24 22:17 ` Ilya Maximets
2023-06-30 3:45 ` Stephen Hemminger
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