Re: [Xen-devel] [PATCH] x86: use 'dom0_mem' to limit the number of pages for dom0

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Aug 15, 2011 at 07:08:33PM +0100, David Vrabel wrote:
> # HG changeset patch
> # User David Vrabel <david.vrabel@xxxxxxxxxx>
> # Date 1313404957 -3600
> # Node ID 1ec6c392d40f37032b0c845094c7ee6ba69740fd
> # Parent  8d6edc3d26d26931f3732a2008fb4818bc7bab2d
> x86: use 'dom0_mem' to limit the number of pages for dom0
> 
> Use the 'dom0_mem' command line option to set the maximum number of
> pages for dom0.  dom0 can use then use the XENMEM_maximum_reservation
> memory op to automatically find this limit and reduce the size of any
> page tables etc.

So .. I was actually curious about this -how did this use to work
with 2.6.18? In there, if you did 'dom0_mem=max:2GB' it would limit the
amount of memory - so how does it do that?

> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> 
> diff -r 8d6edc3d26d2 -r 1ec6c392d40f xen/arch/x86/domain_build.c
> --- a/xen/arch/x86/domain_build.c     Sat Aug 13 10:14:58 2011 +0100
> +++ b/xen/arch/x86/domain_build.c     Mon Aug 15 11:42:37 2011 +0100
> @@ -254,6 +254,8 @@ static unsigned long __init compute_dom0
>      }
>  #endif
>  
> +    d->max_pages = min(max_pages, avail);
> +

don't you need the amount of p2m as well? Or is that all limited
by d->max_pages?

>      return nr_pages;
>  }
>  
> 
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