[libvirt] [PATCH] qemu: Transfer inactive XML among cookie

Eric Blake eblake at redhat.com
Thu Sep 15 14:16:24 UTC 2011

On 09/15/2011 08:04 AM, Michal Privoznik wrote:
> If a domain has inactive XML we want to transfer it to destination
> when migrating with VIR_MIGRATE_PERSIST_DEST. In order to harm
> the migration protocol as least as possible, a optional cookie was
> chosen.
> ---
>   src/qemu/qemu_migration.c |   91 ++++++++++++++++++++++++++++++++++++++++----
>   1 files changed, 82 insertions(+), 9 deletions(-)

I haven't looked at the patch closely, but think you are on the right 
track.  At the high level, though, I'm wondering if our cookie is large 
enough - what limits does our RPC protocol already provide on the size 
of domain xml going over the wire?  We're basically doubling that size, 
by sending both a full domain xml and a cookie containing another domain 
xml.  For example, if the current RPC limit is 64k of data on one 
transaction, and we have a 33k domain xml, then we will fail to migrate 
unless we also bump RPC limits.  But since I don't know the current 
limits on RPC sizes, I may be worrying about nothing.

Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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