Re: What's the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?

[lei yang <yanglei.fage@gmail.com>]

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On Fri, May 21, 2010 at 11:46 PM, Pasi Kärkkäinen <pasik@iki.fi> 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]keir.fraser@eu.citrix.com> wrote:
> >
> >      On 21/05/2010 04:09, "lei yang" <[2]yanglei.fage@gmail.com> 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?
if so, does core 0-4 just can used by dom0? domU can't use it?

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:keir.fraser@eu.citrix.com
> >    2. mailto:yanglei.fage@gmail.com
>
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel
>
>


-- 
"We learn from failure, not from success!"

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