Xen devel - May 2006 - [Xen-ia64-devel] RE: Re: [PATCH] Disable auto-balloon on ia64

>From: Keir Fraser [mailto:Keir.Fraser@cl.cam.ac.uk]
>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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On Mon, 2006-05-22 at 21:33 +0800, Tian, Kevin wrote:
> 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?
   I agree, I think we can get by with only the ia64 changes in the
increase_reservation call.  The other option seems more fragile.  Keir,
would you include the first chunk of Kevin''s patch as a temporary
solution until we have better ballooning support on xen/ia64 (should be
soon)?  Thanks,

	Alex

-- 
Alex Williamson                             HP Linux & Open Source Lab


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