Date: Sat, 9 Aug 2008 09:12:33 +1000 From: Peter Jeremy <peterjeremy@optushome.com.au> To: freebsd-stable@freebsd.org Subject: Re: i386 vs amd64? Message-ID: <20080808231232.GK64458@server.vk2pj.dyndns.org> In-Reply-To: <200808081236.m78CagPH015579@lurza.secnetix.de> References: <1EE0EC59-C48C-4B07-B08E-77BE388BBDE1@develooper.com> <200808081236.m78CagPH015579@lurza.secnetix.de>
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--cz6wLo+OExbGG7q/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2008-Aug-08 14:36:42 +0200, Oliver Fromme <olli@lurza.secnetix.de> wrote: >For example, in amd64 mode there are twice as many CPU >registers available, enabling better optimizations for >the C compiler. Furthermore those registers are twice >as long, which means that 64bit quantities can be handled >with single processor instructions. OTOH, this means roughly 4 times as much processor state to save and restore on a context switch. It also means that longs and pointers are 64-bits instead of 32-bits, which makes executables larger (if you compare executables and libraries on disk between FreeBSD/i386 and FreeBSD/amd64, the latter are 10-15% larger). The VSZ of amd64 executables _appears_ significantly larger due to a bug in binutils and our rtld but this space is never referenced. >That doesn't necessarily mean that code will always run >faster in amd64 mode. There have been reports of certain >edge cases. But in general, amd64 code is faster. As always, the best benchmark is your own application mix. >Bottom line: Install FreeBSD/amd64, unless you have >_specific_ reasons to stay with i386. Keep in mind that, for most things, FreeBSD/amd64 can happily run 32-bit Linux and FreeBSD/i386 executables (though there's no easy way to build FreeBSD/i386 executables on FreeBSD/amd64). This does not extend to KLDs so 3rd-party 32-bit KLDs (eg the nVIDIA graphics driver). --=20 Peter Jeremy Please excuse any delays as the result of my ISP's inability to implement an MTA that is either RFC2821-compliant or matches their claimed behaviour. --cz6wLo+OExbGG7q/ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) iEYEARECAAYFAkic0uAACgkQ/opHv/APuIfZmACeJniSOtR+N1249Wb+d6go7M6H LHQAniwiTItV4IlZ34ZyZLqB4K9sRgdW =72pY -----END PGP SIGNATURE----- --cz6wLo+OExbGG7q/--
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