Re: [Xen-devel] [PATCH] (resent) NUMA node migration

Andre Przywara
Wed, 09 Jan 2008 14:35:49 -0000

John Levon wrote:
> On Fri, Dec 21, 2007 at 11:39:58PM +0100, Andre Przywara wrote:
>
>> accordingly. Only changes Python code in xend. I hope that the patch
>> doesn''t break XenAPI compatibility (adding a parameter seems
fine?).
>>
>> # xm migrate --live --node=<nodenr> <domid> localhost
>> <nodenr> is the number as shown with ''xm info''
under node_to_cpu
>>
>> I am aware that using live migration isn''t the best approach
(takes
>> twice the memory and quite some time),
After thinking more about this, I came to the conclusion that this is
not entirely true. If you want to transfer the guest from one node (with
it''s own memory) to another node (with it''s own memory), then
you would
need to have this amount of memory available at the target anyway.
The performance problem can maybe overcome by not using TCP/IP to
loopback, but a more direct solution (or by reverting to a UNIX socket).

>>but it''s less intrusive and works
>> fine (given localhost migration stability...)
>
> Is this really using localhost live migration to move a domain from one
> NUMA node to another on the same host? Why isn''t there a simpler
way?
Well, Ian described the "simpler way" (thanks for that), I would call
it
more elegant and efficient, but simpler is not the word that comes to
mind...
One advantage of this solution is that the guest stays the same and
there is no interruption. Also one could think about migrating hot pages
  first and letting the rest be done in the background more slowly (this
is how VMware does this).


Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917
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