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Date:      Sun, 29 Sep 2013 01:29:09 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        Ian Lepore <ian@freebsd.org>
Cc:        "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject:   Re: Mixing amd64 kernel with i386 world
Message-ID:  <CAJ-VmomDMY=UPbHC_fHrGwbvAVoi4-2QBajQ9nVKVR4coJpDgg@mail.gmail.com>
In-Reply-To: <1380376595.1197.309.camel@revolution.hippie.lan>
References:  <20130928103758.GC27231@server.rulingia.com> <1380376595.1197.309.camel@revolution.hippie.lan>

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+1.


On 28 September 2013 06:56, Ian Lepore <ian@freebsd.org> wrote:

> On Sat, 2013-09-28 at 20:37 +1000, Peter Jeremy wrote:
> > I have a system with 4GB RAM and hence need to use an amd64 kernel to use
> > all the RAM (I can only access 3GB RAM with an i386 kernel).  OTOH, amd64
> > processes are significantly (50-100%) larger than equivalent i386
> processes
> > and none none of the applications I'll be running on the system need to
> be
> > 64-bit.
> >
> > This implies that the optimal approach is an amd64 kernel with i386
> > userland (I'm ignoring PAE as a useable approach).  I've successfully
> > run i386 jails on amd64 systems so I know this mostly works.  I also
> > know that there are some gotchas:
> > - kdump needs to match the kernel
> > - anything accessing /dev/mem or /dev/kmem (which implies anything that
> >   uses libkvm) probably needs to match the kernel.
> >
> > Has anyone investigated this approach?
> >
>
> Why are you ignoring PAE?  It's been working for me for years.
>

Yeah, if there's PAE issues in -HEAD (read: there are, and we should fix
the bugs that alfred/andre's autotuning stuff introduced) then we should
fix it.

PAE should still be working!



-adrian



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