Re: [Qemu-devel] [PATCH v3] XBZRLE delta for live migration of large memory apps

[Anthony Liguori]

On 08/02/2011 09:01 AM, Alexander Graf wrote:
> On 02.08.2011, at 15:45, Shribman, Aidan wrote:
>
> > Subject: [PATCH v3] XBZRLE delta for live migration of large memory apps
> > From: Aidan Shribman<address@hidden>
> >
> > By using XBZRLE (Xor Binary Zero Run-Length-Encoding) we can reduce VM downtime
> > and total live-migration time for VMs running memory write intensive workloads
> > typical of large enterprise applications such as SAP ERP Systems, and generally
> > speaking for representative of any application with a sparse memory update 
> > pattern.
> >
> > On the sender side XBZRLE is used as a compact delta encoding of page updates,
> > retrieving the old page content from an LRU cache (default size of 64 MB). The
> > receiving side uses the existing page content and XBZRLE to decode the new page
> > content.
> >
> > Work was originally based on research results published VEE 2011: Evaluation of
> > Delta Compression Techniques for Efficient Live Migration of Large Virtual
> > Machines by Benoit, Svard, Tordsson and Elmroth. Additionally the delta encoder
> > XBRLE was improved further using XBZRLE instead.
> >
> > XBZRLE has a sustained bandwidth of 1.5-2.2 GB/s for typical workloads making it
> > ideal for in-line, real-time encoding such as is needed for live-migration.

How does this compare to just doing gzip compression for the same workload?

Regards,

Anthony Liguori