From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] xen: avoid hypercalls when updating
	unpinned pud/pmd
Date: Mon, 2 Jun 2008 13:25:08 +0200
Message-ID: <20080602112508.GD18586@elte.hu>
References: <48409ABB.20301@goop.org>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
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* Jeremy Fitzhardinge <jeremy@goop.org> 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@citrix.com>
> Cc: Jan Beulich <jbeulich@novell.com>

applied to tip/x86/xen, thanks Jeremy.

	Ingo