Re: [Qemu-devel] [v3 01/13] docs: Add a doc about multiple thread compression

[Eric Blake <eblake@redhat.com>]

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On 12/11/2014 06:28 PM, Liang Li wrote:
> Give some details about the multiple compression threads and
> how to use it in live migration.
> 
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
> ---
>  docs/multi-thread-compression.txt | 141 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 141 insertions(+)
>  create mode 100644 docs/multi-thread-compression.txt
> 
> diff --git a/docs/multi-thread-compression.txt b/docs/multi-thread-compression.txt
> new file mode 100644
> index 0000000..3bbc641
> --- /dev/null
> +++ b/docs/multi-thread-compression.txt
> @@ -0,0 +1,141 @@
> +Use multiple thread (de)compression in live migration
> +======================================================
> +Copyright (C) 2014 Intel Corporation

You may want to include 2015 now.


> +Introduction
> +============
> +Instead of sending the guest memory directly, this solution will
> +compress the ram page before sending; after receiving, the data will

s/ram/RAM/

> +be decompressed. Using compression in live migration can help
> +to reduce the data transferred about 60%, this is very useful when the
> +bandwidth is limited, and the migration time can also be reduced about
> +70% in a typical case.

Of course, that's all dependent on memory having compressible contents.
 An application that reads /dev/hwrng into a large amount of memory will
not be that compressible :)


> +
> +When to use the multiple thread compression in live migration
> +==============================================================

off-by-one on the divider length


> +Usage
> +=====
> +1. Verify both the source and destination QEMU are able
> +to support the multiple thread compression migration:
> +    {qemu} info_migrate_capablilites

s/capablilites/capabilities/

> +    {qemu} ... compress: off ...
> +
> +2. Activate compression on the souce:

s/souce/source/

> +    {qemu} migrate_set_capability compress on
> +
> +3. Set the compression thread count on source:
> +    {qemu} migrate_set_paramter compress_threads 12

s/paramter/parameter/


> +
> +The following is the default setting:

s/is...setting/are...settings/

> +    compress: off
> +    compress_threads: 8
> +    decompress_threads: 2
> +    compress_level: 1 (which means best speed)
> +
> +So, only the first two steps are required to use the multiple
> +thread compression in migration. You can do more if the default
> +setting is not appropriate.

s/setting is/settings are/

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


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