[Qemu-devel] Re: Live migration broken when under heavy IO

[Anthony Liguori <aliguori@us.ibm.com>]

Avi Kivity wrote:
> Yes, that's even better (though without linux-aio, it's equivalent).

Not absolutely equivalent.  There many be queued requests that haven't 
yet been dispatched to the thread pool, but yeah, I understand what you 
mean.

>>
>> The tricky bit is that this has to happen at the device layer because 
>> the opaques cannot be saved in a meaningful way.
>>
>
> Do you mean the device has to record all cancelled requests and replay 
> them?  I think we can do it at the block layer (though we have to 
> avoid it for nested requests).

In order to complete the requests, you have to call a callback and pass 
an opaque with the results.  The callback/opaque cannot be saved in the 
block layer in a meaningful way.

-- 
Regards,

Anthony Liguori