RE: [Xen-ia64-devel][PATCH][RFC] Task: support huge pageRE:[Xen-ia64-devel] Xen/IA64 Healthiness Report -Cset#11460

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Hi Magnus,

>From: Magnus Damm [mailto:magnus@xxxxxxxxxxxxx]
>Sent: 2006年9月29日 16:22
>To: Xu, Anthony
>Cc: Isaku Yamahata; Tristan Gingold; Alex Williamson;
>xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: RE: [Xen-ia64-devel][PATCH][RFC] Task: support huge 
>>
>> Maybe we can postpone this.
>> Creating/Destroying domain frequently in XEN/IA64 may be not the case.
>> It may be not important as it seems in XEN/IA64.
>
>I think it is difficult to implement defragmentation unless you are able
>to migrate pages. And I'm not sure how easy it is to implement such a
>feature on top of xens current memory model.
So we can postpone defragmentation.
As yamahata-san pointed out, if fail, Xen fall back to allocate normal page 
size(16K),
Fail again, and then creating domain fails due to no enough memory, in the same 
time XEN should print some information to notify user this domain may be slow.

>
>And by that, do you mean that all memory belonging to a domain should be
>contiguous, or just that the large pages should be allocated from a page
>pool based on contiguous large pages?
>
For instance, if a domain has 4G, XEN allocates 16 256M contiguous memory 
chunks to this domain, thus whatever tlb entry Guest wants to insert, if page 
size is less then 256M, Xen can insert it into machine TLB or VHPT, and there 
is no breaking.


>> That's Ok.
>> As Ian talked in Xen summit, XEN/IA32 may need to support huge page, there 
>> are also
>huge pages in IA32, 4M and 2M.
>
>ia32 is an environment that I'm much more familiar with, so I would be
>happy doing some work on that side.
Sorry, I don't know when XEN/IA32 will start to discuss this.

>
>I'm not sure if the dual address space idea is good or not, but it may
>be worth thinking about anyway. I agree with yamahata-san that a first
>step probably should be to use one type of large page per domain.
Agree,


>
>Have a nice weekend!
Thanks

>
>/ magnus

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