Re: [Qemu-devel] [PATCH v11 3/9] Add XBZRLE documentation

[Eric Blake <eblake@redhat.com>]

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On 05/22/2012 06:56 AM, Orit Wasserman wrote:
> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
> ---
>  docs/xbzrle.txt |  114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 114 insertions(+), 0 deletions(-)
>  create mode 100644 docs/xbzrle.txt
> 
> diff --git a/docs/xbzrle.txt b/docs/xbzrle.txt
> new file mode 100644
> index 0000000..16950d5
> --- /dev/null
> +++ b/docs/xbzrle.txt
> @@ -0,0 +1,114 @@
> +XBZRLE (Xor Based Zero Run Length Encoding)
> +===========================================
> +
> +Using XBZRLE (Xor Based Zero Run Length Encoding) allows for the reduction of VM
> +downtime and the total live-migration time of Virtual machines.
> +It is particularly useful for virtual machines running memory write intensive
> +workloads that are typical of large enterprise applications such as SAP ERP
> +Systems, and generally speaking for any application that uses a sparse memory
> +update pattern.
> +
> +Instead of sending the changed guest memory page this solution will send a
> +compressed version of the updates, thus reducing the amount of data sent during
> +live migration.
> +In order to be able to calculate the update, the previous memory pages needed to

s/needed/need/

> +be stored. Those pages are stored in a dedicated cache (hash table) and are

s/stored./stored on the source./

> +Format
> +=======
> +
> +The compression format uses the zero value, where zero represents an unchanged
> +value.

s/uses the zero value/performs an XOR between the previous and current
content of the page/

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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