Re: [Xen-ia64-devel] Regression: [IA64] Saner dom0 memory and cpudefaults

[Alex Williamson <alex.williamson@xxxxxx>]

On Wed, 2007-09-05 at 10:20 +0900, Isaku Yamahata wrote:
> 
> How about this option?
> - Allocate pseudo physical contiguous region from the end of 
>   conventional memory and relinquish at somewhere of the booting
>   process. It would be almost the same effect ot reduce dom0 size by xen.

   I'm not sure I see where the advantage is here.  If xen doesn't have
enough free memory to allocate the contiguous region, how does moving
dom0 memory help that?  It might make sense to do this from the
standpoint of preserving low memory and making it more likely that a
contiguous region for low memory can be created, but I don't see the
advantage in the case where xen is already under memory pressure.  Can
you explain?

>   Probably at the time dom0 switching from the init bootmem allocator to
>   the buddy allocator or before the swith.
>   With the buddy allocator it would be somewhat difficult.
> 
> 
> I missed the trivial option.
> - Xen parses dom0 command line looking for "swiotlb=", and
>   reduce dom0 size more. Too easy/hacky?

   Yeah, we have to know too much about the dom0 kernel to make this
work right.  If the user doesn't specify a swiotlb=, we'd have to assume
64MB, which would be incorrect if booting on a system with a hardware
iommu.  Default sizes could change, etc...  It seems a little messy.
Good idea though.  Thanks,

        Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.


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