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Re: [Qemu-devel] [v4 12/13] migration: Add command to set migration para
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [v4 12/13] migration: Add command to set migration parameter |
Date: |
Tue, 03 Feb 2015 19:27:23 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 02/03/2015 06:26 PM, Li, Liang Z wrote:
>> Hmm - do we really need two parameters here? Remember, compress
>> threads is used only on the source, and decompress threads is used only on
>> the destination. Having a single parameter, 'threads', which is set to
>> compression threads on source and decompression threads on destination,
>> and which need not be equal between the two machines, should still work,
>> right?
>>
>
> Yes, it works. The benefit of using one parameter instead of two can reduce
> the QMP
> command count, and the side effect of using the same thread count for
> compression
> and decompression is a little waste if the user just want to use the default
> settings,
> you know, decompression is usually about 4 times faster than compression.
> Use more
> decompression threads than needed will waste some RAM which used to save data
> structure related to the decompression thread, about 4K bytes RAM per thread,
> is it
> acceptable?
The default setting is no compression. The user already has to
configure things on both sides to get compression, so it is not a burden
to ask them to configure thread count on both sides correctly.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- Re: [Qemu-devel] [v4 11/13] migration: Add interface to control compression, (continued)