[Xen-ia64-devel] RE: [Xen-devel] Re: [PATCH] Disable auto-balloon on ia64

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: 2006年5月22日 17:51
>To: Keir Fraser
>
>>>     We just need to reverse the whole change for ia64, since both
>domU
>>> and domVTI are insert a hole by this auto-balloon patch. Due to
>>> missing balloon support on xen/ia64 as you said, both domU and
>domVTI
>>> failed due to this change.
>>
>> The first patch that you work around seems okay to me. That is, it
>> seems correct that we make initial reservation exclude
>> 'getDomainMemory headroom'. Shouldn't ia64 reserve extra memory
>as it
>> needs it, as x86 does,  rather than up front?
>>
>> The second bit of your workaround, which applies to
>getDomainMemory:
>> I'll wait and see if Charles has anything to say, but otherwise I'll
>> remove the code that adds the extra slack entirely.
>
>Thinking about it, that slack might have been added to give enough
>space for shadow page tables for live migration. Also, it shouldn't
>give you any problems if you weren't allocating headroom up front -- if
>you can fix ia64 to allocate the extra memory as needed then you
>shouldn't need either of your workarounds?
>
>  -- Keir

OK, the question by far is that ia64 describes the memory hierarchy 
presented to domain by d->max_pages. Before balloon is ready, we at 
least need to ensure all frames covered by d->max_pages allocated for 
target domain. Then there're two alternatives:
        - Keep the first piece of change on increase_reservation, which 
ensures all pages including extra spaces allocated immediately.
        - Pass the extra memory size to xen at arch_set_info_guest, and 
then change xen/ia64 to only tell domain maximum pfns as 
d->max_pages-extra_size

Both need to be changed again later if balloon is ready. So I prefer to 
option I which is simpler and can help Alex to do sync quickly. How do 
you think?

Thanks,
Kevin

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