[Xen-devel] Re: [PATCH] xen: avoid hypercalls when updating unpinned pud/pmd

[Ingo Molnar <mingo@xxxxxxx>]

* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

> When operating on an unpinned pagetable (ie, one under construction or 
> destruction), it isn't necessary to use a hypercall to update a 
> pud/pmd entry.  Jan Beulich observed that a similar optimisation 
> avoided many thousands of hypercalls while doing a kernel build.
>
> One tricky part is that early in the kernel boot there's no page 
> structure, so we can't check to see if the page is pinned.  In that 
> case, we just always use the hypercall.
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxxxx>

applied to tip/x86/xen, thanks Jeremy.

        Ingo

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