Re: [Qemu-devel] [RFC][PATCH 10/16 v6] run dump at the background

[Jan Kiszka]

On 2012-02-15 10:22, Wen Congyang wrote:
> At 02/15/2012 05:07 PM, Jan Kiszka Wrote:
>> On 2012-02-15 04:47, Wen Congyang wrote:
>>> At 02/15/2012 02:27 AM, Jan Kiszka Wrote:
>>>> On 2012-02-14 19:05, Jan Kiszka wrote:
>>>>> On 2012-02-09 04:28, Wen Congyang wrote:
>>>>>> The new monitor command dump may take long time to finish. So we need 
>>>>>> run it
>>>>>> at the background.
>>>>>
>>>>> How does it work? Like live migration, i.e. you retransmit (overwrite)
>>>>> already written but then dirtied pages? Hmm... no.
>>>>>
>>>>> What does background mean then? What is the use case? What if the user
>>>>> decides to resume the vm?
>>>>
>>>> OK, that is addressed in patch 15! I would suggest merging it into this
>>>> patch. It makes sense to handle that case gracefully right from the
>>>> beginning.
>>>
>>> OK, I will merge it.
>>>
>>>>
>>>> OK, now I have some other question: What is the point of rate-limiting
>>>> the dump? The guest is not running, thus not competing for bandwidth.
>>>
>>> I use bandwidth to try to control the writing speed. If we write the vmcore
>>> to disk in a high speed, it may affect some other appilications which use
>>> the same disk too.
>>
>> Just like the guest of that particular VM can do. I don't think we need
>> this level of control here, it will be provided (if required) at a
>> different level, affecting the whole QEMU process. Removing the vmcore
>> bandwidth control will simplify code and user interface.
> 
> OK. I will implementing it like this:
> 1. write 100ms
> 2. sleep 100ms(allow qemu to do the other things)
> 3. goto 1

Why? Just write as fast as possible.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux