From: Jinpu Wang <jinpu.wang@ionos.com>
To: Peter Xu <peterx@redhat.com>
Cc: "Yu Zhang" <yu.zhang@ionos.com>,
"Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com>,
"Elmar Gerdes" <elmar.gerdes@ionos.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Yuval Shaia" <yuval.shaia.ml@gmail.com>,
"Kevin Wolf" <kwolf@redhat.com>,
"Prasanna Kumar Kalever" <prasanna.kalever@redhat.com>,
"Cornelia Huck" <cohuck@redhat.com>,
"Michael Roth" <michael.roth@amd.com>,
"Prasanna Kumar Kalever" <prasanna4324@gmail.com>,
"integration@gluster.org" <integration@gluster.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>,
"Daniel P. Berrangé" <berrange@redhat.com>,
"devel@lists.libvirt.org" <devel@lists.libvirt.org>,
"Hanna Reitz" <hreitz@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Thomas Huth" <thuth@redhat.com>,
"Eric Blake" <eblake@redhat.com>,
"Song Gao" <gaosong@loongson.cn>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Wainer dos Santos Moschetta" <wainersm@redhat.com>,
"Beraldo Leal" <bleal@redhat.com>,
arei.gonglei@huawei.com, pannengyuan@huawei.com
Subject: Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling
Date: Mon, 8 Apr 2024 16:07:20 +0200 [thread overview]
Message-ID: <CAMGffE=i+hVCNaX_31h1D1VW7JGJBqoa9T0qEJe2CDcb9BPiAA@mail.gmail.com> (raw)
In-Reply-To: <Zgx3brrz8m0V7HS4@x1n>
Hi Peter,
On Tue, Apr 2, 2024 at 11:24 PM Peter Xu <peterx@redhat.com> wrote:
>
> On Mon, Apr 01, 2024 at 11:26:25PM +0200, Yu Zhang wrote:
> > Hello Peter und Zhjian,
> >
> > Thank you so much for letting me know about this. I'm also a bit surprised at
> > the plan for deprecating the RDMA migration subsystem.
>
> It's not too late, since it looks like we do have users not yet notified
> from this, we'll redo the deprecation procedure even if it'll be the final
> plan, and it'll be 2 releases after this.
>
> >
> > > IMHO it's more important to know whether there are still users and whether
> > > they would still like to see it around.
> >
> > > I admit RDMA migration was lack of testing(unit/CI test), which led to the a few
> > > obvious bugs being noticed too late.
> >
> > Yes, we are a user of this subsystem. I was unaware of the lack of test coverage
> > for this part. As soon as 8.2 was released, I saw that many of the
> > migration test
> > cases failed and came to realize that there might be a bug between 8.1
> > and 8.2, but
> > was unable to confirm and report it quickly to you.
> >
> > The maintenance of this part could be too costly or difficult from
> > your point of view.
>
> It may or may not be too costly, it's just that we need real users of RDMA
> taking some care of it. Having it broken easily for >1 releases definitely
> is a sign of lack of users. It is an implication to the community that we
> should consider dropping some features so that we can get the best use of
> the community resources for the things that may have a broader audience.
>
> One thing majorly missing is a RDMA tester to guard all the merges to not
> break RDMA paths, hopefully in CI. That should not rely on RDMA hardwares
> but just to sanity check the migration+rdma code running all fine. RDMA
> taught us the lesson so we're requesting CI coverage for all other new
> features that will be merged at least for migration subsystem, so that we
> plan to not merge anything that is not covered by CI unless extremely
> necessary in the future.
>
> For sure CI is not the only missing part, but I'd say we should start with
> it, then someone should also take care of the code even if only in
> maintenance mode (no new feature to add on top).
>
> >
> > My concern is, this plan will forces a few QEMU users (not sure how
> > many) like us
> > either to stick to the RDMA migration by using an increasingly older
> > version of QEMU,
> > or to abandon the currently used RDMA migration.
>
> RDMA doesn't get new features anyway, if there's specific use case for RDMA
> migrations, would it work if such a scenario uses the old binary? Is it
> possible to switch to the TCP protocol with some good NICs?
We have used rdma migration with HCA from Nvidia for years, our
experience is RDMA migration works better than tcp (over ipoib).
Switching back to TCP will lead us to the old problems which was
solved by RDMA migration.
>
> Per our best knowledge, RDMA users are rare, and please let anyone know if
> you are aware of such users. IIUC the major reason why RDMA stopped being
> the trend is because the network is not like ten years ago; I don't think I
> have good knowledge in RDMA at all nor network, but my understanding is
> it's pretty easy to fetch modern NIC to outperform RDMAs, then it may make
> little sense to maintain multiple protocols, considering RDMA migration
> code is so special so that it has the most custom code comparing to other
> protocols.
+cc some guys from Huawei.
I'm surprised RDMA users are rare, I guess maybe many are just
working with different code base.
>
> Thanks,
>
> --
> Peter Xu
Thx!
Jinpu Wang
>
next prev parent reply other threads:[~2024-04-08 14:08 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 13:02 [PATCH-for-9.1 v2 0/3] rdma: Remove RDMA subsystem and pvrdma device Philippe Mathieu-Daudé
2024-03-28 13:02 ` [PATCH-for-9.1 v2 1/3] hw/rdma: Remove pvrdma device and rdmacm-mux helper Philippe Mathieu-Daudé
2024-03-28 17:51 ` Thomas Huth
2024-03-28 13:02 ` [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling Philippe Mathieu-Daudé
2024-03-28 14:18 ` Fabiano Rosas
2024-03-28 15:01 ` Peter Xu
2024-03-28 15:22 ` Thomas Huth
2024-03-28 19:04 ` Peter Xu
2024-03-29 1:53 ` Zhijian Li (Fujitsu) via
2024-03-29 10:28 ` Philippe Mathieu-Daudé
2024-03-29 19:44 ` Daniel P. Berrangé
2024-04-01 7:55 ` Zhijian Li (Fujitsu) via
2024-04-01 21:26 ` Yu Zhang
2024-04-02 21:23 ` Peter Xu
2024-04-08 14:07 ` Jinpu Wang [this message]
2024-04-08 16:18 ` Peter Xu
2024-04-09 7:32 ` Jinpu Wang
2024-04-09 19:46 ` Peter Xu
2024-04-10 2:28 ` Zhijian Li (Fujitsu) via
2024-04-10 13:49 ` Peter Xu
2024-04-11 14:20 ` Peter Xu
2024-04-11 16:36 ` Yu Zhang
2024-04-12 14:04 ` Peter Xu
2024-04-29 13:08 ` Michael Galaxy
2024-04-29 14:56 ` Peter Xu
2024-04-29 20:45 ` Yu Zhang
2024-04-29 20:56 ` Michael Galaxy
2024-04-30 7:15 ` Markus Armbruster
2024-04-30 8:00 ` Daniel P. Berrangé
2024-05-01 15:31 ` Peter Xu
2024-05-01 15:59 ` Daniel P. Berrangé
2024-05-01 16:16 ` Peter Xu
2024-05-02 13:22 ` Michael Galaxy
2024-05-02 13:30 ` Jinpu Wang
2024-05-02 16:19 ` Peter Xu
2024-05-02 17:10 ` Jinpu Wang
2024-05-03 6:40 ` Jinpu Wang
2024-05-03 14:33 ` Peter Xu
2024-05-06 10:08 ` Jinpu Wang
2024-05-06 15:28 ` Peter Xu
2024-05-07 4:52 ` Jinpu Wang
2024-05-08 10:06 ` Daniel P. Berrangé
2024-05-06 2:06 ` Gonglei (Arei) via
2024-05-06 15:18 ` Peter Xu
2024-05-07 1:50 ` Gonglei (Arei) via
2024-05-07 16:28 ` Peter Xu
2024-05-09 8:58 ` Zheng Chuan via
2024-05-09 14:13 ` Peter Xu
2024-05-13 7:30 ` Jinpu Wang
2024-05-14 15:19 ` Yu Zhang
2024-05-16 17:29 ` Michael Galaxy
2024-05-17 13:01 ` Yu Zhang
2024-05-21 22:15 ` Peter Xu
2024-05-28 9:06 ` Gonglei (Arei) via
2024-05-28 9:11 ` Jinpu Wang
2024-05-28 15:54 ` Peter Xu
2024-05-29 2:43 ` Gonglei (Arei) via
2024-05-29 4:33 ` Jinpu Wang
2024-05-29 6:05 ` Greg Sword
2024-05-29 7:04 ` Jinpu Wang
2024-05-29 8:30 ` Gonglei (Arei) via
2024-05-29 9:17 ` Jinpu Wang
2024-05-29 9:34 ` Gonglei (Arei) via
2024-05-29 9:44 ` Jinpu Wang
2024-05-29 9:47 ` Gonglei (Arei) via
2024-05-29 11:13 ` Haris Iqbal
2024-05-30 18:23 ` Sean Hefty
2024-05-29 16:33 ` Peter Xu
2024-05-13 18:52 ` Michael Galaxy
2024-06-05 0:31 ` Dr. David Alan Gilbert
2024-06-05 14:10 ` Peter Xu
2024-06-05 14:59 ` Peter Xu
2024-06-05 20:48 ` Dr. David Alan Gilbert
2024-06-05 21:18 ` Peter Xu
2024-06-07 8:57 ` Gonglei (Arei) via
2024-04-11 14:42 ` Jinpu Wang
2024-04-09 9:00 ` Markus Armbruster
2024-03-28 13:02 ` [PATCH-for-9.1 v2 3/3] block/gluster: " Philippe Mathieu-Daudé
2024-03-28 17:54 ` Thomas Huth
2024-03-29 9:17 ` [PATCH-for-9.1 v2 0/3] rdma: Remove RDMA subsystem and pvrdma device Michael S. Tsirkin
2024-04-03 9:37 ` Philippe Mathieu-Daudé
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