linux-kernel - Re: [patch 15/26] Xen-paravirt_ops: Add apply_to_page_range() which applies a function to a pte range.

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Date:	Fri, 16 Mar 2007 10:08:43 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	Christoph Lameter <clameter@....com>
Subject: Re: [patch 15/26] Xen-paravirt_ops: Add apply_to_page_range() which
 applies a function to a pte range.

Ingo Molnar wrote:
> nice one! I suspect we could simplify some of the less 
> performance-critical open-coded pagetable walker loops in the kernel 
> with this? (i'm not even sure it's all that much of a performance loss 
> to pass a function pointer around - would be nice to convert say 
> mprotect() to this and see the performance difference?)
>   

apply_page_to_range has the side-effect of allocating all the pagetable
levels for the address range it walks.  Xen uses this to populate
pagetables (for example, build out the pagetable, and let the hypervisor
plug a mapping into the pte page).

If that's OK for the other uses, then it should be good.

    J
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