Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling

[Peter Xu]

On Tue, May 28, 2024 at 09:06:04AM +0000, Gonglei (Arei) wrote:
> Hi Peter,
> 
> > -----Original Message-----
> > From: Peter Xu [mailto:peterx@redhat.com]
> > Sent: Wednesday, May 22, 2024 6:15 AM
> > To: Yu Zhang <yu.zhang@ionos.com>
> > Cc: Michael Galaxy <mgalaxy@akamai.com>; Jinpu Wang
> > <jinpu.wang@ionos.com>; Elmar Gerdes <elmar.gerdes@ionos.com>;
> > zhengchuan <zhengchuan@huawei.com>; Gonglei (Arei)
> > <arei.gonglei@huawei.com>; Daniel P. Berrangé <berrange@redhat.com>;
> > Markus Armbruster <armbru@redhat.com>; Zhijian Li (Fujitsu)
> > <lizhijian@fujitsu.com>; 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>; Paolo Bonzini
> > <pbonzini@redhat.com>; qemu-block@nongnu.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>; Alex Bennée <alex.bennee@linaro.org>;
> > Wainer dos Santos Moschetta <wainersm@redhat.com>; Beraldo Leal
> > <bleal@redhat.com>; Pannengyuan <pannengyuan@huawei.com>;
> > Xiexiangyou <xiexiangyou@huawei.com>; Fabiano Rosas <farosas@suse.de>
> > Subject: Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling
> > 
> > On Fri, May 17, 2024 at 03:01:59PM +0200, Yu Zhang wrote:
> > > Hello Michael and Peter,
> > 
> > Hi,
> > 
> > >
> > > Exactly, not so compelling, as I did it first only on servers widely
> > > used for production in our data center. The network adapters are
> > >
> > > Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720
> > > 2-port Gigabit Ethernet PCIe
> > 
> > Hmm... I definitely thinks Jinpu's Mellanox ConnectX-6 looks more 
> > reasonable.
> > 
> > https://lore.kernel.org/qemu-devel/CAMGffEn-DKpMZ4tA71MJYdyemg0Zda15
> > wVAqk81vXtKzx-LfJQ@mail.gmail.com/
> > 
> > Appreciate a lot for everyone helping on the testings.
> > 
> > > InfiniBand controller: Mellanox Technologies MT27800 Family
> > > [ConnectX-5]
> > >
> > > which doesn't meet our purpose. I can choose RDMA or TCP for VM
> > > migration. RDMA traffic is through InfiniBand and TCP through Ethernet
> > > on these two hosts. One is standby while the other is active.
> > >
> > > Now I'll try on a server with more recent Ethernet and InfiniBand
> > > network adapters. One of them has:
> > > BCM57414 NetXtreme-E 10Gb/25Gb RDMA Ethernet Controller (rev 01)
> > >
> > > The comparison between RDMA and TCP on the same NIC could make more
> > sense.
> > 
> > It looks to me NICs are powerful now, but again as I mentioned I don't 
> > think it's
> > a reason we need to deprecate rdma, especially if QEMU's rdma migration has
> > the chance to be refactored using rsocket.
> > 
> > Is there anyone who started looking into that direction?  Would it make 
> > sense
> > we start some PoC now?
> > 
> 
> My team has finished the PoC refactoring which works well. 
> 
> Progress:
> 1.  Implement io/channel-rdma.c,
> 2.  Add unit test tests/unit/test-io-channel-rdma.c and verifying it is 
> successful,
> 3.  Remove the original code from migration/rdma.c,
> 4.  Rewrite the rdma_start_outgoing_migration and 
> rdma_start_incoming_migration logic,
> 5.  Remove all rdma_xxx functions from migration/ram.c. (to prevent RDMA live 
> migration from polluting the core logic of live migration),
> 6.  The soft-RoCE implemented by software is used to test the RDMA live 
> migration. It's successful.
> 
> We will be submit the patchset later.

That's great news, thank you!

-- 
Peter Xu