Re: [Qemu-devel] Tunneled Migration with Non-Shared Storage

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Paolo Bonzini (pbonzini@redhat.com) wrote:
> 
> 
> On 18/11/2014 21:28, Dr. David Alan Gilbert wrote:
> > This seems odd, since as far as I know the tunneling code is quite separate
> > to the migration code; I thought the only thing that the migration
> > code sees different is the file descriptors it gets past.
> > (Having said that, again I don't know storage stuff, so if this
> > is a storage special there may be something there...)
> 
> Tunnelled migration uses the old block-migration.c code.  Non-tunnelled
> migration uses the NBD server and block/mirror.c. 

OK, that explains that.  Is that because the tunneling code can't 
deal with tunneling the NBD server connection?

> The main problem with
> the old code is that uses a possibly unbounded amount of memory in
> mig_save_device_dirty and can have huge jitter if any serious workload
> is running in the guest.

So that's sending dirty blocks iteratively? Not that I can see
when the allocations get freed; but is the amount allocated there
related to total disk size (as Gary suggested) or to the amount
of dirty blocks?

Dave

> 
> Paolo
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK