Re: [Qemu-devel] virtio-serial-pci very expensive during live migration

[Paolo Bonzini <pbonzini@redhat.com>]

Il 19/06/2014 17:19, Chris Friesen ha scritto:
> On 05/09/2014 02:19 AM, Paolo Bonzini wrote:
>> Il 09/05/2014 02:53, Chris Friesen ha scritto:
>>>
>>>
>>> Turns out I spoke too soon.  With the patch applied, it boots, but if I
>>> try to do a live migration both the source and destination crash.  This
>>> happens for both the master branch as well as the stable-1.4 branch.
>>
>> The destination doesn't crash, it simply stops because it got an
>> incomplete migration stream.  Thanks for the report, the patch seems
>> correct so it's worthwhile looking at it more closely.
>>
>>> If I back out the patch, it works fine.  If I leave the patch in and
>>> disable kvm acceleration it works fine.
>>
>> Indeed, non-KVM doesn't use ioeventfd at all.
>
> Did anyone ever figure out why wrapping the whole thing in
> memory_region_transaction_begin()/memory_region_transaction_commit()
> caused problems?

No, sorry, I didn't have time.  On the other hand patches went in that 
avoided unnecessary work on ioeventfds, so you may want to test again 
with the latest master branch.

Paolo