Hello, > -----Original Message----- > From: Peter Xu [mailto:[email protected]] > Sent: Monday, May 6, 2024 11:18 PM > To: Gonglei (Arei) <[email protected]> > Cc: Daniel P. Berrangé <[email protected]>; Markus Armbruster > <[email protected]>; Michael Galaxy <[email protected]>; Yu Zhang > <[email protected]>; Zhijian Li (Fujitsu) <[email protected]>; Jinpu Wang > <[email protected]>; Elmar Gerdes <[email protected]>; > [email protected]; Yuval Shaia <[email protected]>; Kevin Wolf > <[email protected]>; Prasanna Kumar Kalever > <[email protected]>; Cornelia Huck <[email protected]>; > Michael Roth <[email protected]>; Prasanna Kumar Kalever > <[email protected]>; [email protected]; Paolo Bonzini > <[email protected]>; [email protected]; [email protected]; > Hanna Reitz <[email protected]>; Michael S. Tsirkin <[email protected]>; > Thomas Huth <[email protected]>; Eric Blake <[email protected]>; Song > Gao <[email protected]>; Marc-André Lureau > <[email protected]>; Alex Bennée <[email protected]>; > Wainer dos Santos Moschetta <[email protected]>; Beraldo Leal > <[email protected]>; Pannengyuan <[email protected]>; > Xiexiangyou <[email protected]> > 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/ > 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. Regards, -Gonglei
