Re: [Qemu-devel] broken incoming migration

[Peter Lieven]

Am 09.06.2013 um 06:12 schrieb liu ping fan <address@hidden>:

> Hi Peter,
> 
> Is it that sending zero page mostly service the first iteration, ie
> bluk-stage? And for the subsequent iteration, dirty pages are normally
> not zero.
> 

Yes most Zero Pages are sent during bulk stage except for busy windows guests 
or linux with page sanitization.
In these cases freed Memory is zeroed.

Peter

> Thanks
> 
> On Wed, Jun 5, 2013 at 2:09 PM, Peter Lieven <address@hidden> wrote:
>> 
>> Am 05.06.2013 um 05:37 schrieb Alexey Kardashevskiy <address@hidden>:
>> 
>>> On 06/05/2013 05:15 AM, Peter Lieven wrote:
>>>> 
>>>> Am 04.06.2013 um 17:17 schrieb Paolo Bonzini <address@hidden>:
>>>> 
>>>>> Il 04/06/2013 16:48, Peter Lieven ha scritto:
>>>>>> Still using 3.2, but strange enough the above example is also not
>>>>>> increasing RSS size for me.
>>>>>> 
>>>>>> Can you try the following:
>>>>>> qemu git master with 1G of memory (hanging in bios with no boot device)
>>>>>> and migrate it. Before migration RSS Size os somewhat
>>>>>> around 16MB. After migration its RSS size is in the order of 1G.
>>>>> 
>>>>> That may be a kernel bug.  The kernel did not do the copy-on-write trick
>>>>> on huge zero pages.  It was fixed last year, maybe 3.2 is not enough.
>>>>> Try adding a MADV_HUGEPAGE madvise to the testcase and see if it 
>>>>> reproduces.
>>>> 
>>>> that's it. thanks for the pointer. the huge zero page was introduced in 
>>>> 3.8.
>>>> 
>>>> paolo, alexey: can you please verify the following works for you:
>>>> https://github.com/plieven/qemu/tree/fix-migration
>>> 
>>> These two?
>>> 848b796 Tue Jun 4 14:43:04 2013 +0200 Peter Lieven migration: do not
>>> overwrite zero pages
>>> 2206ac8 Tue Jun 4 14:25:33 2013 +0200 Peter Lieven Revert "migration: do
>>> not sent zero pages in bulk stage"
>> 
>> Yes, sorry forgot to mention this.
>> 
>>> 
>>> That works for me (qemu 1.5, kernel 3.9-rc2).
>>> Tested-by: Alexey Kardashevskiy <address@hidden>
>> 
>> Thank you,
>> Peter