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

[Rusty Russell <rusty@xxxxxxxxxxxxxxx>]

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?
Rusty.
PS. I really must revise my "paravirt-ops counter" patch which tallies
how much each op is getting called.



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