Re: [Xen-devel] Re: [patch 05/24] Xen-paravirt_ops: Add pagetable accessors to pack and unpack pagetable entries

Rusty Russell wrote:
On Wed, 2007-02-21 at 23:15 +0100, Andi Kleen wrote:

On Wednesday 21 February 2007 21:52, Jeremy Fitzhardinge wrote:

Add a set of accessors to pack, unpack and modify page table entries
(at all levels). This allows a paravirt implementation to control the
contents of pgd/pmd/pte entries. For example, Xen uses this to
convert the (pseudo-)physical address into a machine address when
populating a pagetable entry, and converting back to pphys address
when an entry is read.

Do you have some lmbench numbers before/after this change?
iirc at least fork and exit do a lot of pte accesses in various forms.
If it's measurable it might be needed to patch those for the native case.


Yes, __mkpte must be patched to avoid performance embarrassment.

Jeremy, did you want me to do this, or are you happy to?

I'm working on it now. I'll mail out a proposal in a little bit.

J
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