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Re: [Xen-users] how many VCPUs per physical CPU?

  • To: Siddharth Wagh <siddharth.wagh@xxxxxxxxx>
  • From: Peter Peltonen <peter.peltonen@xxxxxxxxx>
  • Date: Mon, 6 Jul 2009 17:22:18 +0300
  • Cc: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 06 Jul 2009 07:22:59 -0700
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Hi and thanks for your reply,

On Mon, Jul 6, 2009 at 4:47 PM, Siddharth Wagh<siddharth.wagh@xxxxxxxxx> wrote:
> The Xen document specifies that upto 32 VCPUs may be allocated to a single
> domU. But it is recommended that one allocates the same number of VCPUs or
> less than the number of logical CPUs on your machine, for optimum
> performance. Since, you have a quad-core processor, the maximum number of
> VCPUs you could allot to each domU w/o compromising on performance is 4.

But what is the benefit of having more VCPUs in a logical CPU?

In what kind of cirumstances does a domU perform better with a 4 VCPUs
than with 1 VCPU?

I don't undrestand the difference, as in the end there is just one
logical CPU doing all the work.


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