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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id o3-20020a655203000000b005f750f36968sm8702087pgp.42.2024.05.07.09.28.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 May 2024 09:28:14 -0700 (PDT) Date: Tue, 7 May 2024 12:28:08 -0400 From: Peter Xu To: "Gonglei (Arei)" Cc: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , Markus Armbruster , Michael Galaxy , Yu Zhang , "Zhijian Li (Fujitsu)" , Jinpu Wang , Elmar Gerdes , "qemu-devel@nongnu.org" , Yuval Shaia , Kevin Wolf , Prasanna Kumar Kalever , Cornelia Huck , Michael Roth , Prasanna Kumar Kalever , "integration@gluster.org" , Paolo Bonzini , "qemu-block@nongnu.org" , "devel@lists.libvirt.org" , Hanna Reitz , "Michael S. Tsirkin" , Thomas Huth , Eric Blake , Song Gao , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Alex =?utf-8?Q?Benn=C3=A9e?= , Wainer dos Santos Moschetta , Beraldo Leal , Pannengyuan , Xiexiangyou , zhengchuan Subject: Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling Message-ID: References: <46f5e323-632d-7bda-f2c5-3cfa7b1c6b68@akamai.com> <877cgfe2yw.fsf@pond.sub.org> <7e902e4e576a4e199e36d28f99bd55e5@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.581, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, May 07, 2024 at 01:50:43AM +0000, Gonglei (Arei) wrote: > Hello, > > > -----Original Message----- > > From: Peter Xu [mailto:peterx@redhat.com] > > Sent: Monday, May 6, 2024 11:18 PM > > To: Gonglei (Arei) > > Cc: Daniel P. Berrangé ; Markus Armbruster > > ; Michael Galaxy ; Yu Zhang > > ; Zhijian Li (Fujitsu) ; Jinpu Wang > > ; Elmar Gerdes ; > > qemu-devel@nongnu.org; Yuval Shaia ; Kevin Wolf > > ; Prasanna Kumar Kalever > > ; Cornelia Huck ; > > Michael Roth ; Prasanna Kumar Kalever > > ; integration@gluster.org; Paolo Bonzini > > ; qemu-block@nongnu.org; devel@lists.libvirt.org; > > Hanna Reitz ; Michael S. Tsirkin ; > > Thomas Huth ; Eric Blake ; Song > > Gao ; Marc-André Lureau > > ; Alex Bennée ; > > Wainer dos Santos Moschetta ; Beraldo Leal > > ; Pannengyuan ; > > Xiexiangyou > > Subject: Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling > > > > On Mon, May 06, 2024 at 02:06:28AM +0000, Gonglei (Arei) wrote: > > > Hi, Peter > > > > Hey, Lei, > > > > Happy to see you around again after years. > > > Haha, me too. > > > > RDMA features high bandwidth, low latency (in non-blocking lossless > > > network), and direct remote memory access by bypassing the CPU (As you > > > know, CPU resources are expensive for cloud vendors, which is one of > > > the reasons why we introduced offload cards.), which TCP does not have. > > > > It's another cost to use offload cards, v.s. preparing more cpu resources? > > > Software and hardware offload converged architecture is the way to go for all cloud vendors > (Including comprehensive benefits in terms of performance, cost, security, and innovation speed), > it's not just a matter of adding the resource of a DPU card. > > > > In some scenarios where fast live migration is needed (extremely short > > > interruption duration and migration duration) is very useful. To this > > > end, we have also developed RDMA support for multifd. > > > > Will any of you upstream that work? I'm curious how intrusive would it be > > when adding it to multifd, if it can keep only 5 exported functions like what > > rdma.h does right now it'll be pretty nice. We also want to make sure it works > > with arbitrary sized loads and buffers, e.g. vfio is considering to add IO loads to > > multifd channels too. > > > > In fact, we sent the patchset to the community in 2021. Pls see: > https://lore.kernel.org/all/20210203185906.GT2950@work-vm/T/ I wasn't aware of that for sure in the past.. Multifd has changed quite a bit in the last 9.0 release, that may not apply anymore. One thing to mention is please look at Dan's comment on possible use of rsocket.h: https://lore.kernel.org/all/ZjJm6rcqS5EhoKgK@redhat.com/ And Jinpu did help provide an initial test result over the library: https://lore.kernel.org/qemu-devel/CAMGffEk8wiKNQmoUYxcaTHGtiEm2dwoCF_W7T0vMcD-i30tUkA@mail.gmail.com/ It looks like we have a chance to apply that in QEMU. > > > > One thing to note that the question here is not about a pure performance > > comparison between rdma and nics only. It's about help us make a decision > > on whether to drop rdma, iow, even if rdma performs well, the community still > > has the right to drop it if nobody can actively work and maintain it. > > It's just that if nics can perform as good it's more a reason to drop, unless > > companies can help to provide good support and work together. > > > > We are happy to provide the necessary review and maintenance work for RDMA > if the community needs it. > > CC'ing Chuan Zheng. I'm not sure whether you and Jinpu's team would like to work together and provide a final solution for rdma over multifd. It could be much simpler than the original 2021 proposal if the rsocket API will work out. Thanks, -- Peter Xu