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Re: [Qemu-devel] Problems about "live backup vm" patch, which is issued


From: Liu Ji
Subject: Re: [Qemu-devel] Problems about "live backup vm" patch, which is issued by Wenchao Xia.
Date: Wed, 20 Feb 2013 23:16:57 +0800

Hi, Wenchao

In order to determine whether my test method or my system environment have problems, 
I want to test the patch on the qemu version which you used. 
You can give me a rough version number.

You told me that patch is based on the version before qemu-1.3. But in your patch, 
there is a diff:
    --- a/savevm.c
    +++ b/savevm.c
    @@ -698,7 +698,7 @@ int qemu_get_byte(QEMUFile *f)
         return result;
     }

    -static int64_t qemu_ftell(QEMUFile *f)
    +int64_t qemu_ftell(QEMUFile *f)
     {
         return f->buf_offset - f->buf_size + f->buf_index;
     }
    @@ -2061,32 +2061,10 @@ out:
         return ret;
     }
But before qemu-1.3, the "qemu_ftell" function is not a static function.
In qemu-1.3 and the following version, the "qemu_ftell" function is change 
to a static function. So I'm not sure which version you used.


Which tool you used to connect the VM, Spice, VNC or others?
When I use the Spice, after I "loadvm" the snapshot which is create by 
the "migrate image:" command, the qemu-kvm will be error or crash. 
But when I use VNC, it is OK.
How do you think this issue? Please give me some suggestion.

And can you give me the detailed "qemu-kvm" command, which you used to start the VM.
I want compare your "qemu-kvm" command and my.


Best Regards

Liu Ji


-----------------------------------------------------

2013/2/19 Wenchao Xia <address@hidden>
Hi, Liu Ji
  Thanks for trying my trival patch. That patch is based on the version
before qemu-1.3, and since qemu have important change about migration
from Juan after that, So I think it would not work since 1.3.

  I am trying to fix the size problem now, and then reimplement a formal
patch of "live savevm" after that, as part of the incremental backup
enhancement, you can take a look of the plan at:
http://wiki.qemu.org/Features/VMSnapshotEnchancement
  Pls forgive me about the latency of the work, I have just come back
from vacation.:)

> Hello Wenchao Xia,
> I am very interested in your "live backup vm" patch of qemu, which have
> been sent to qemu-devel mail-list in "8 Dec 2012".
> http://lists.gnu.org/archive/html/qemu-devel/2012-12/msg00800.html
>
> I have test your patch in qemu-1.3.1, but I have two problems:
>
> 1) After I exec the "migrate image:" command, although the CPU of VM is not
> suspended, the running of VM is very slow. It is very difficult to operate
> the VM
>
> by Spice.
> 2) When I "loadvm" the snapshot which is create by the "migrate image:"
> command, the Qemu output error. I change the version of qemu to 1.3.0, the
> "loadvm"
>
> caused a crash.
> Could you tell me which baseline version of qemu you used? And do you have
> the same problems?
> Do you have optimized the patch, and can you provide the latest patch for
> me?
>
> Thanks.
>


--
Best Regards

Wenchao Xia



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