Re: [Qemu-devel] [RFC PATCH 0/4] savevm: save vmsate with fixed size

[Pavel Hrdina <phrdina@redhat.com>]

On 03/04/2013 04:04 PM, Wenchao Xia wrote:
>
>>> You probably get some improvements of the file size when the migration
>>> takes a while, depending on how much of the memory actually has to be
>>> saved. You might however end up with a lot more small writes instead of
>>> some big ones before, which might hurt performance.
>>>
>>> Do you have any data about the resulting performance and file size?
>>>
>>    ah, an important issue I haven't test, thanks for tipping it, let
>> me add code for migration to file, and have a test. It also
>> can be optimized a bit in qemu_fseek(), but IMHO the optimization
>> for small writes would better goto block layer either in qemu
>> or underling components in system.
>>
> Hi,Juan
>   talking about performance, in migration there are two buffer used,
> one in qemu_file as static array, and one in migration as dynamic
> allocated buffer,
> should they be merged to avoid extra memcpy?
>

Hi Wenchao,

This is already posted on qemu-devel list,

http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg04119.html
http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg04222.html

Pavel