Re: [PATCH 1/4] Pte drop ptep_get_and_clear paravirt op.patch

[Jeremy Fitzhardinge]

Zachary Amsden wrote:
> In shadow mode hypervisors, ptep_get_and_clear achieves the desired
> purpose of keeping the shadows in sync by issuing a native_get_and_clear,
> followed by a call to pte_update, which indicates the PTE has been
> modified.
>
> Direct mode hypervisors (Xen) have no need for this anyway, and will trap
> the update using writable pagetables.
>   

Jan Beulich just posted a patch for Xen/linux which specialzes
ptep_get_and_clear, which apparently improves kernel-compile performance
by 25-30% on some configurations.  I think we'll want to keep this.

    J
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