[Xen-users] Re: how to congure dom0 to 1G, and domU to 1G

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, May 20, 2010 at 04:59:00PM +0800, lei yang wrote:
>    On Thu, May 20, 2010 at 2:04 PM, Pasi Kärkkäinen <[1]pasik@xxxxxx> wrote:
> 
>      On Thu, May 20, 2010 at 01:59:16PM +0800, lei yang wrote:
>      >    Hi Experts,
>      >
> 
>      I removed xen-devel from CC since this is a very basic question,
>      and not related to Xen development.
>      >    I want to configure dom0 to 1g and dom0 to 1g ?
>      >
>      >    I know dom0_mem=1024M can do it for dom0, how about domU?
>      >
> 
>      Uhm.. for domU you specify:
> 
>      memory = 1024
> 
>      in the domU configuration file (/etc/xen/<guest>).
>      >    My machine has 8 cores
>      >    how to  specify xen to 4 cpus?
>      >
> 
>      Xen is the *hypervisor*, so it has to use ALL the physical CPUs/cores,
>      to be able to schedule vcpus!!
> 
>    Do you mean we can't specify xen to 4 cpus, and if we specify "nosmp" what
>    does it mean
>    it will use *just* one physical core to schedule vcpus? and dom0 and domU
>    just can use one core?
> 

Depends where you specify "nosmp", for Xen or for dom0 kernel.

Xen *has* to have access to all the physical cpus/cores you want to use
for your guest, including dom0.

See Xen vcpu pinning for more information.

> 
> 
>      >    how to specify dom0 4 cpus
>      >
> 
>      dom0_max_vcpus=4 for xen.gz in grub.conf.
> 
> 
> 
>   Specified options "dom0_max_vcpus=2" and "dom0_vcpus_pin".
>   Specified option "dom0_max_vcpus=2".
> 
>  what's the difference? which performance will be higher?
> 

Adding dom0_vcpus_pin will automatically pin the dom0 vcpus to matching 
physical cpus.
That might not make a difference alone.. you need/want to pin the other guest 
vcpus aswell,
depending what kind of configuration you want to get.

-- Pasi


> 
>  Thanks
>  Lei
> 
>      >    how to specify domU 5 cpus ?
>      >
> 
>      vcpus = 5
>      >    can we specify dom0 to 1 cpu, at same time domU to 6 cpu
>      >
> 
>      dom0_max_vcpus=1 dom0_vcpus_pin
> 
>      in grub.conf for xen.gz.
>      >    can we specify nosmp to xen, and then specify dom0 cpu > 1?
>      >
> 
>      No.
> 
>      See: [2]http://wiki.xensource.com/xenwiki/XenBestPractices
>      and: [3]http://wiki.xensource.com/xenwiki/XenCommonProblems
>      -- Pasi
>      >
>      >
>      >    Thanks
>      >    Lei
>      >
>      >    --
>      >    "We learn from failure, not from success!"
> 
>    --
>    "We learn from failure, not from success!"
> 
> References
> 
>    Visible links
>    1. mailto:pasik@xxxxxx
>    2. http://wiki.xensource.com/xenwiki/XenBestPractices
>    3. http://wiki.xensource.com/xenwiki/XenCommonProblems

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