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

[Anthony Liguori <anthony@codemonkey.ws>]

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<aidan.shribman@sap.com>
>>
>> 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