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Re: [Xen-devel] [PATCH 1/2] PV hugepages - Xen patch



Keir Fraser wrote:
Actually this is an interesting one. For a PV guest it may be in general
unsolvable, since the target machine may not have allocatable 2MB extents.
It may also screw live migration since 2MB is a very coarse granularity to
do dirty-page tracking. One option: perhaps the PV kernel could shatter and
then reconstruct (as best it can) superpage mappings across save/restore?

That means you need to notify the guest when you're starting a live migration, rather than just springing it on them at the last moment as we do now.

But shattering large pages all over the place is going to be pretty expensive, and possibly awkward if it suddenly needs to come up with a pile of pages for the new L1 entries.

   J

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