xen discuss - Aug 2009 - xVM domU and pagesize

Hi all,

I have a quick question.

Observationally, it appears the pagesize a domU sees (at least with OpenSolaris
on EC2) is 4KB.  Is this always the case?  Does the dom0 perform some kind of
small domU to large dom0 page magic?

I ask because I have an application which will use large pages if available, and
I plan to run it on EC2.

Thanks in advance,

- Matt
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This message posted from opensolaris.org

Anyone?
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This message posted from opensolaris.org

Matt Ingenthron wrote:
> Hi all,
> 
> I have a quick question.
> 
> Observationally, it appears the pagesize a domU sees (at least with
OpenSolaris on EC2) is 4KB.  Is this always the case?  Does the dom0 perform
some kind of small domU to large dom0 page magic?
> 
Yes currently Xen is only set up to allocate and manage 4k pages for all 
guest domains DomU and Dom0.  I am not positive, but I think that HVM 
DomU''s may be able to use aggregated large pages if the hardware 
platform supports HAP.  However while there is some bnefefit to HAP 
assisted large pages if the underlying pages are not really contiguous 
then the TLB still maps things 4k at a time.

> I ask because I have an application which will use large pages if
available, and I plan to run it on EC2.
> 
> Thanks in advance,
> 
> - Matt