Here are some results comparing Ininiband with IPOIB TCP/IP migration to
Infiniband native RDMA migration:
http://nowlab.cse.ohio-state.edu/publications/conf-papers/2007/huang-clu
ster07.pdf
4 to 5 times quicker is about the average so it seems it could bring big
advantages for those that use Infiniband or IWarp NICs. Any chance of it
being considered for a future version?
Rob
-----Original Message-----
From: Ian Pratt [mailto:Ian.Pratt@xxxxxxxxxxxxx] 
Sent: 02 January 2009 12:07
To: Robert Dunkley; xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Ian Pratt
Subject: RE: [Xen-devel] RDMA based Live Migration
> I saw someone had done patches for this and run benchmarks a while ago
> but still no mention of support within Xen. Is support for RDMA based
> migration planned? (Or even better is it already present?)
I don't think I've seen any patches for doing live relocation using
RDMA, but it wouldn't be hard to create them.
However, the benefits may not actually be that great: when doing a live
relocation you're usually moving a VM from a loaded machine to a
less-loaded one, hence it's the sending machine that you care most about
CPU usage. Assuming the NIC you're using has TSO, it should be
relatively efficient to send the data over TCP. However, this could
definitely be optimized by adding a zero copy TX mechanism to avoid the
copy from user space to the kernel, and this would benefit all NICs, not
just RDMA. It requires a little bit of work to do this as sendfile isn't
a good fit and the foreign pages will likely need page structs which
isn't the case at present.
Ian
>
>
> Thanks,
>
> Rob
>
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