linux-kernel - Re: PAE/NX without performance drain?

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Date:	Sun, 10 Dec 2006 15:56:26 -0500
From:	John Richard Moser <nigelenki@...cast.net>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: PAE/NX without performance drain?

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Arjan van de Ven wrote:
>> Too bad PAE can't be detected at boot time; someone else mentioned that
>> some recent Pentium M laptops (and anything older than PPro) don't boot
>> if PAE is on.
> 
> even Windows has 2 kernel binaries for this case btw, it's really really
> really hard.
> 

Yeah, I've been told Windows has 4 kernels (SMP/UP x PAE/NonPAE).  In
the case of a microkernel it'd be trivial; in the case of a monolith,
you'd basically be shoehorning uK behavior in, probably by compiling
both sets of functions and linking the appropriate set just-in-time
(i.e. before entering protected mode).  This would be an ugly hack.

>> I want my hardware NX bit working in Ubuntu without having to recompile
>> my kernel dammit.
> 
> other distros ship a PAE enabled kernel, and use that for NX enabled
> machines (all NX capable machines support PAE obviously). I'm surprised
> Ubuntu doesn't, maybe ask them? (Or use a distro that does have this)
> 

OpenSuSE and Fedora Core 6 both fail this; I checked the .config for the
default kernels (by proxy on OpenSuSE 10.2; I asked someone) and ran my
test case on FC6 (LiveCD from
http://www.fedoraunity.org/news-archives/fedora-core-6-zod-live-spins-released).



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