Re: [Xen-ia64-devel] [PATCH] Use saner dom0 memory and vcpu defaults, don't panic on over-allocation

[Jarod Wilson <jwilson@xxxxxxxxxx>]

Jarod Wilson wrote:
> Isaku Yamahata wrote:
>> On Tue, Jul 31, 2007 at 10:43:44PM -0600, Alex Williamson wrote:
>>>> +       /* maximum available memory for dom0 */
>>>> +       max_dom0_pages = avail_domheap_pages() -
>>>> +                        min(avail_domheap_pages() /
>>>> +                        16UL, 512UL << (20 - PAGE_SHIFT)) ;
>>>    I assume this heuristic came from Akio's patch in the thread you
>>> referenced; can anyone explain how this was derived and why it's
>>> necessary?  It looks like a fairly random fudge factor.  Thanks,
>> I guess it comes from compute_dom0_nr_pages() under arch/x86.
>> However I don't know why compute_dom0_nr_pages() is so.
>> Anyway It should be different for ia64. While I'm guessing the most
>> dominant factor is the p2m table, domain0 building process should
>> be revised for the correct estimation.
> 
> The version above does seem to work well for me on all the boxes I've
> tested it on, but I'm definitely all ears for how exactly to obtain a
> better calculation. I'm not familiar enough with the memory layout to
> easily come up with it myself, so anyone else has a suggestion there,
> please do speak up.

Still reading over code, but throwing this idea out there... Would it
make sense to use efi_memmap_walk() to determine max_dom0_size? And if
so, should the size of the xenheap be subtracted from that?

-- 
Jarod Wilson
jwilson@xxxxxxxxxx

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