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From: Ilya Maximets <i.maximets@ovn.org>
To: Ilya Maximets <i.maximets@ovn.org>,
	Stefan Hajnoczi <stefanha@redhat.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>,
	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: Fri, 19 Mar 2021 17:45:46 +0100	[thread overview]
Message-ID: <4f26e9a9-8dd1-f619-4337-dcecf35d9f3b@ovn.org> (raw)
In-Reply-To: <ee5e0d95-1684-c283-c48c-c45cc2bec57b@ovn.org>

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?

> 
> 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.

> 
> 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.
> 


  reply	other threads:[~2021-03-19 16:45 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 [this message]
2021-03-24 20:56       ` Maxime Coquelin
2021-03-24 21:39         ` Ilya Maximets
2021-03-24 21:51           ` Maxime Coquelin
2021-03-24 22:17             ` Ilya Maximets
2023-06-30  3:45 ` Stephen Hemminger

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