WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] What's the different for "dom0_max_vcpus=4 dom0_vcpus_pi

On Fri, May 21, 2010 at 11:51:34PM +0800, lei yang wrote:
>    On Fri, May 21, 2010 at 11:46 PM, Pasi Kärkkäinen <[1]pasik@xxxxxx> wrote:
> 
>      On Fri, May 21, 2010 at 11:39:50PM +0800, lei yang wrote:
>      >    On Fri, May 21, 2010 at 2:57 PM, Keir Fraser
>      >    <[1][2]keir.fraser@xxxxxxxxxxxxx> wrote:
>      >
>      >      On 21/05/2010 04:09, "lei yang" <[2][3]yanglei.fage@xxxxxxxxx>
>      wrote:
>      >
>      >      > Hi experts,
>      >      >
>      >      >
>      >      > Q1:What's the different for "dom0_max_vcpus=4 dom0_vcpus_pin"
>      and
>      >      > "dom0_max_vcpus=4" ? which will get better performance
>      >
>      >      The former restricts Xen to only run Dom0 VCPUs 0-3 on physical
>      CPUs
>      >      0-3.
>      >
>      >
>      >    dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3?
>      >
> 
>      Yes.
>      > can it be 3 4 5 6?
>      >
> 
>      Yes, modify the pinning when the system has booted up using "xm
>      vcpu-pin".
> 
> 
> 
>    if I don't use "xm vcpu-pin" does it will use core 0 1 2 3 by default not
>    can use 3 4 5 6?
>

Yes, it'll use 0 1 2 3 as a default. It cannot be changed, unless you do 
custom pinning after the system has started.

>    if so, does core 0-4 just can used by dom0? domU can't use it?
> 

domU can (and will) use them, so you need to also pin the domUs so that they 
won't
try to use the dom0 cores, if you absolutely want to dedicate 4 cores only for 
dom0.

Just play with "xm vcpu-pin" and "xm vcpu-list" and you'll figure it out.

-- Pasi

>    Thanks
>    Lei
> 
> 
>      >    if remove "dom0_vcpus_pin" just use "  dom0_max_vcpus=4 " can it be
>      3 4 5
>      >    6 ?
>      >
> 
>      Yes, set up the pinning yourself.
> 
> 
>    again. if just use "dom0_max_vcpus=4" not use "dom0_vcpus_pin"  and I
>    don't use "xm vcpu-pin", can 't be 3 4 5 6,
> 
>    Thanks
>    Lei
> 
> 
>      -- Pasi
>      >
>      >      It's not really a performance thing, but instead is to mean that
>      some
>      >      things
>      >      like cpufreq management can work directly from dom0. We don't
>      really use
>      >      the
>      >      dom0_vcpus_pin option much.
>      >      > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0"
>      or
>      >      means "4
>      >      > cores(not dedicate cores) will be used by dom0, eg: core2-5 or
>      >      core3-6?
>      >
>      >      Dom0's VCPUs can be scheduled on any physical CPU at any time,
>      unles
>      >      dom0_vcpus_pin is specified.
>      >      > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one
>      >      core????if so,
>      >      > can we specify the use different core. eg: dom0=core2
>      domU=core3? xen
>      >      will use
>      >      > just one core?
>      >
>      >      It brings Xen up on the boot CPU only. Nothing in the system will
>      use
>      >      the
>      >      other CPUs. You don't want to use this option really.
>      >       -- Keir
>      >
>      >    --
>      >    "We learn from failure, not from success!"
>      >
>      > References
>      >
>      >    Visible links
>      >    1. mailto:[4]keir.fraser@xxxxxxxxxxxxx
>      >    2. mailto:[5]yanglei.fage@xxxxxxxxx
>      > _______________________________________________
>      > Xen-devel mailing list
>      > [6]Xen-devel@xxxxxxxxxxxxxxxxxxx
>      > [7]http://lists.xensource.com/xen-devel
> 
>    --
>    "We learn from failure, not from success!"
> 
> References
> 
>    Visible links
>    1. mailto:pasik@xxxxxx
>    2. mailto:keir.fraser@xxxxxxxxxxxxx
>    3. mailto:yanglei.fage@xxxxxxxxx
>    4. mailto:keir.fraser@xxxxxxxxxxxxx
>    5. mailto:yanglei.fage@xxxxxxxxx
>    6. mailto:Xen-devel@xxxxxxxxxxxxxxxxxxx
>    7. http://lists.xensource.com/xen-devel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel