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Is 7G memory good enough for current PAE HVM guest
xiaohui.xin at intel
Nov 30, 2006, 11:08 PM
Post #1 of 2 (41 views)
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Some background:

We are now debugging the Qemu map cache issue for HVM PAE guest on PAE
host.



We found that a hardcode limit for shadow2 which we can only support
about 7G memory for HVM PAE guest.

With the attached workaround and the Qemu map cache patch, we can now
support almost 16G memory PAE guest.

But it does of course decrease the virtual address space which Xen can
map.

So it is a question now: Is 7G memory good enough for current PAE HVM
guest?

And by the way, if a guest requests too much memory, Xen should check it
first before creation.





Thanks

Xiaohui/Dexuan

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Re: Is 7G memory good enough for current PAE HVM guest [ In reply to ]
keir at xensource
Dec 1, 2006, 1:08 AM
Post #2 of 2 (42 views)
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On 1/12/06 6:08 am, "Xin, Xiaohui" <xiaohui.xin@intel.com> wrote:

> Some background:
> We are now debugging the Qemu map cache issue for HVM PAE guest on PAE host.
>
> We found that a hardcode limit for shadow2 which we can only support about 7G
> memory for HVM PAE guest.
> With the attached workaround and the Qemu map cache patch, we can now support
> almost 16G memory PAE guest.
> But it does of course decrease the virtual address space which Xen can map.
> So it is a question now: Is 7G memory good enough for current PAE HVM guest?
> And by the way, if a guest requests too much memory, Xen should check it first
> before creation.

We should simply check against the 7G limit. Making the memory hole bigger
breaks ABI compatibility.

I see there are other fixes and cleanups in the patch so I think the bulk of
it should be applied anyway.

-- Keir

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