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Re: [Xen-users] Release 0.8.9 of GPL PV drivers for Windows

  • To: "jim burns" <jim_burn@xxxxxxxxxxxxx>
  • From: "Todd Deshane" <deshantm@xxxxxxxxx>
  • Date: Wed, 7 May 2008 00:06:41 -0400
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 06 May 2008 21:07:11 -0700
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

On Tue, May 6, 2008 at 11:53 PM, jim burns <jim_burn@xxxxxxxxxxxxx> wrote:
> On Tuesday May 06 2008 11:13:36 pm Todd Deshane wrote:
>  > I think that your experience (allowing Xen to do the scheduling itself is
>  > most efficient and only try to tweak the scheduling in very special cases
>  > and/or you really know what you are doing) should be considered
>  > conventional wisdom.
>  >
>  > Can you refresh me on the recommendations of the Xen developers that you
>  > are referring to?
>  I was responding to Pasi's comment:
>  On Tuesday May 06 2008 03:21:29 am Pasi Kärkkäinen wrote:
> > I think you should re-test with vcpu=1.
>  >
> > Configure dom0 for 1 vcpu and domU for 1 vcpu and pin the domains to have a
>  > dedicated core. This way you're not sharing any pcpu's between the domains.
>  > I think this is the "recommended" setup from xen developers for getting
>  > maximum performance.
>  >
>  > I think the performance will be worse when you have more vcpus in use than
>  > your actual pcpu count..
In our Running Xen book [1] chapter 12 "Managing Guest Resources" it says:

"If you are planning on having a substantial number of guests running, we
recommend sticking with the default VCPUs. The only place that VCPU
pinning may be advantageous is to restrict a CPU to run only for Domain0.
Each guest relies on the services Domain0 offers ..."

It goes on to talk about especially heavy I/O etc. etc.

I bring this up since a lot of thought went into the details of the book. Not
that we will always be right, but continuing to sharpen our knowledge and
working through the details can only help future versions etc.


[1] http://runningxen.com

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