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


From: Wenchao Xia
Subject: Re: [Qemu-devel] [RFC PATCH 0/4] savevm: save vmsate with fixed size
Date: Wed, 06 Mar 2013 09:25:01 +0800
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130215 Thunderbird/17.0.3

于 2013-3-5 20:04, Pavel Hrdina 写道:
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

  Great, hope this can be upstream fast, thanks for tipping it.

--
Best Regards

Wenchao Xia




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