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

[Dulloor <dulloor@xxxxxxxxx>]

On Mon, Nov 9, 2009 at 7:57 AM, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:
>>>> Dulloor <dulloor@xxxxxxxxx> 09.11.09 11:35 >>>
>>-  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
>>valid.
>
> Pseudo-consistent at best - there's no reason to believe that the node
> a physical page appears to live on (by looking up its address in the SRAT)
> has any relationship to the node it really lives on.
>
> And even if that was the case, you could easily end up with many (up to
> all but one) nodes appearing unpopulated (due to dom0_mem=).

Agreed pseudo-consistent (offseted by alloc_spfn). But, even with the
dom0_mem set,
the numa ranges are silently clipped, so the mappings are still
(almost)consistent.

>
>>- 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.
>
> That doesn't help you with the node ID issue: The tools can make
> meaningful use of Xen node IDs; if you want to do this in the kernel
> you'll have to establish a kernel<->Xen translation of node IDs.
>
For other guest domains, we will need translation (part of my next patches).
But, for dom0, translation is implicit due to shared acpi tables.

I could work on a patch to make mappings fully consistent (by rigging the
slit/srat values as seen by dom0), inertia being an interface acceptable to
Linux folks. Do we need that ?

> Jan
>
>

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