linux-kernel - Re: [PATCH 10/28] i386: map enough initial memory to create lowmem mappings

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Message-ID: <462FC8CD.1030505@goop.org>
Date:	Wed, 25 Apr 2007 14:31:57 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Chuck Ebbert <cebbert@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zach@...are.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 10/28] i386: map enough initial memory to create lowmem
 mappings

Eric W. Biederman wrote:
> Jeremy did your kernel have PAE enabled?
>
> It just occurred to me that we have at all of the memory below 1M (say about
> 512K) mapped and available to setup new mappings.
>
> The only way I can see a page fault happening is if you were using a PAE
> enabled kernel (so you were not updating the current page tables) and
> you have more than 256M of low memory, and we don't get any much extra
> from always mapping 4M at a time.

Yes, that's the situation.  PAE enabled, ~768MB of memory and a large
kernel which mostly fills the 8M mapping.

    J
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