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Re: [Xen-devel] numa=on broken


  • To: Ryan Harper <ryanh@xxxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Sun, 01 Apr 2007 09:29:03 +0100
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Sun, 01 Apr 2007 09:29:15 +0100
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acd0N83pDFaxTuArEdu2qAAWy6hiGQ==
  • Thread-topic: [Xen-devel] numa=on broken

On 1/4/07 06:20, "Ryan Harper" <ryanh@xxxxxxxxxx> wrote:

>>> I'm getting ready to re-submit patches to export the topology information
>>> so the userspace tools can use that info to make intelligent selections.
>>> This was available back in October, but was never picked up, or even
>>> commented upon.
>> 
>> But can tools make sane automatic decisions on domain creation? And if tools
> 
> I don't think the tools would do any worse than what an admin would do:
> keep the domains within a node.

Well, for example it's not really going to work with the default memory
allocation policy where dom0 takes all memory and then auto-balloons itself
down as domains are created. In this situation the domU will end up with
whatever dom0 happens to have freed up: there's no guarantee of locality.

I don't think that auto-ballooning is a particularly sensible setting for
serious use of Xen. I'd always advise to work out how much memory your dom0
actually needs and make that a static allocation at boot time. But it is our
out-of-the-box default: another thing that needs explicit changing (via
dom0_mem= in this case).

 -- Keir



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