Re: [Qemu-devel] [RFC PATCH RDMA support v5: 03/12] comprehensive protocol documentation

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 04/14/2013 07:59 AM, Michael S. Tsirkin wrote:
> On Fri, Apr 12, 2013 at 04:43:54PM +0200, Paolo Bonzini wrote:
>> Il 12/04/2013 13:25, Michael S. Tsirkin ha scritto:
>>> On Fri, Apr 12, 2013 at 12:53:11PM +0200, Paolo Bonzini wrote:
>>>> Il 12/04/2013 12:48, Michael S. Tsirkin ha scritto:
>>>>> 1.  You have two protocols already and this does not make sense in
>>>>> version 1 of the patch.
>>>> It makes sense if we consider it experimental (add x- in front of
>>>> transport and capability) and would like people to play with it.
>>>>
>>>> Paolo
>>> But it's not testable yet.  I see problems just reading the
>>> documentation.  Author thinks "ulimit -l 10000000000" on both source and
>>> destination is just fine.  This can easily crash host or cause OOM
>>> killer to kill QEMU.  So why is there any need for extra testers?  Fix
>>> the major bugs first.
>>>
>>> There's a similar issue with device assignment - we can't fix it there,
>>> and despite being available for years, this was one of two reasons that
>>> has kept this feature out of hands of lots of users (and assuming guest
>>> has lots of zero pages won't work: balloon is not widely used either
>>> since it depends on a well-behaved guest to work correctly).
>> I agree assuming guest has lots of zero pages won't work, but I think
>> you are overstating the importance of overcommit.  Let's mark the damn
>> thing as experimental, and stop making perfect the enemy of good.
>>
>> Paolo
> It looks like we have to decide, before merging, whether migration with
> rdma that breaks overcommit is worth it or not.  Since the author made
> it very clear he does not intend to make it work with overcommit, ever.
>
That depends entirely as what you define as overcommit.

The pages do get unregistered at the end of the migration =)

- Michael