xen: avoid hypercalls when updating unpinned pud/pmd

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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@citrix.com>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

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This commit is contained in:

Jeremy Fitzhardinge 2008-05-31 01:24:27 +01:00 • committed by Ingo Molnar

parent 15ce60056b

commit e2426cf85f

3 changed files with 50 additions and 11 deletions

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14

arch/x86/xen/enlighten.c

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39

arch/x86/xen/mmu.c

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8

arch/x86/xen/mmu.h

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