Date: Sat, 28 Sep 2013 09:34:25 -0500 (CDT) From: Nathan Whitehorn <nwhitehorn@anacreon.physics.wisc.edu> To: Peter Jeremy <peter@rulingia.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Mixing amd64 kernel with i386 world Message-ID: <alpine.BSF.2.00.1309280933350.65859@anacreon.physics.wisc.edu> In-Reply-To: <20130928103758.GC27231@server.rulingia.com> References: <20130928103758.GC27231@server.rulingia.com>
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On Sat, 28 Sep 2013, 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. > For whatever it is worth, I have done this running a ppc32 userland with a ppc64 kernel (that is how ppc64 was first developed actually, before the 64-bit userland existed) and it worked just fine. -Nathan
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