Re: [Qemu-devel] [PATCH 0/5] Enable postcopy RDMA live migration

[Dr. David Alan Gilbert]

* Lidong Chen (address@hidden) wrote:
> Current Qemu RDMA communication does not support send and receive
> data at the same time, so when RDMA live migration with postcopy
> enabled, the source qemu return path thread get qemu file error.
> 
> Those patch add the postcopy support for RDMA live migration.

This description is a little misleading; it doesn't really
do RDMA during the postcopy phase - what it really does is disable
the RDMA page sending during the postcopy phase, relying on the 
RDMA codes stream emulation to send the page.

That's not necessarily a bad fix; you get the nice performance of RDMA
during the precopy phase, but how bad are you finding the performance
during the postcopy phase - the RDMA code we have was only really
designed for sending small commands over the stream?

Dave

> Lidong Chen (5):
>   migration: create a dedicated connection for rdma return path
>   migration: add the interface to set get_return_path
>   migration: implement the get_return_path for RDMA iochannel
>   migration: fix qemu carsh when RDMA live migration
>   migration: disable RDMA WRITR after postcopy started.
> 
>  migration/qemu-file-channel.c |  12 ++--
>  migration/qemu-file.c         |  13 +++-
>  migration/qemu-file.h         |   2 +-
>  migration/rdma.c              | 148 
> ++++++++++++++++++++++++++++++++++++++++--
>  4 files changed, 163 insertions(+), 12 deletions(-)
> 
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK