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Re: [Xen-devel] Xen-devel [XEN PATCH] [Linux-PVOPS] ballooning on numa

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen-devel [XEN PATCH] [Linux-PVOPS] ballooning on numa domains
From: Dulloor <dulloor@xxxxxxxxx>
Date: Mon, 9 Nov 2009 05:35:17 -0500
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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- Xen guest domains can't read the numa acpi tables and this patch (in
the current state) is a no-op for them.

-  dom0 can read the numa tables (same as xen). Also, the memory map
for dom0 is (currently) set in a way that the numa ranges are
consistent. I don't see that changing, so I feel the assumption is

- XENMEMF flags are indeed meant for xen tools. But, ballooning is
completely xen specific too ... it is a xen tool, except that it
resides in domain's kernel/tree.

Please let know your take on this.


On Mon, Nov 9, 2009 at 4:03 AM, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:
>>>> Dulloor <dulloor@xxxxxxxxx> 09.11.09 08:40 >>>
>>Problems :
>>* With ballooning, the mfns could change underneath and the numa
>>mappings could get distorted (even for domains with the actual
>>physical memory map).
> Besides being unsure about the idea as such (I don't think Xen kernels
> have been knowing much about NUMA characteristics of the underlying
> machine), you're assuming that node IDs in kernel and hypervisor are
> identical, which I don't think is generally valid; XENMEMF_node(), afaict,
> is presently meant to be used by the Xen tools (and hypervisor internal
> users) only.
> Jan

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