Date: Sat, 19 Mar 2005 16:27:29 -0800
From: "David S. Miller" <davem@davemloft.net>
To: davidm@hpl.hp.com
Cc: davidm@napali.hpl.hp.com, rohit.seth@intel.com, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org
Subject: Re: [patch] arch hook for notifying changes in PTE protections bits
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On Sat, 19 Mar 2005 12:30:05 -0800
David Mosberger <davidm@napali.hpl.hp.com> wrote:

> I agree about your concern about cost.  Accessing the page_map is
> expensive (integer division + memory access) and we have to do that in
> order to find out if the page is i-cache clean.

First, it's a multiply by reciprocol.  At least on sparc64 I get
this emitted by the compiler.

Secondly, if you're willing to sacrifice 8 bytes per page struct
simply define WANT_PAGE_VIRTUAL and page struct will be exactly
64 bytes and thus the divide a will turn into a simple shift.
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