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

[Gonglei (Arei)]

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.


Regards,
-Gonglei

> Thanks,
> 
> --
> Peter Xu