Date: Tue, 14 Mar 2006 09:27:00 -0300 From: JoaoBR <joao@matik.com.br> To: ray@redshift.com Cc: kono@kth.se, freebsd-amd64@freebsd.org Subject: Re: amd64 slower than i386 on identical AMD 64 system? Message-ID: <200603140927.00320.joao@matik.com.br> In-Reply-To: <3.0.1.32.20060314034932.00ae9678@pop.redshift.com> References: <200603140740.38388.joao@matik.com.br> <3.0.1.32.20060314034932.00ae9678@pop.redshift.com>
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On Tuesday 14 March 2006 08:49, ray@redshift.com wrote: > At 12:38 PM 3/14/2006 +0100, Alexander Konovalenko wrote: > | On Tuesday 14 March 2006 11:40, JoaoBR wrote: > | > so where is your comparism? My point was that the same hardware is > | > faster running i386 > | > > | I have experienced that -O3 and -ffast-math optimizations flags on AMD64 > | might cause degrade in performance, meaning that -O2 is the fastest. Wh= en > | you compile your ports what opt. flags do you use? Try to reinstall > | ubench with different flags. Also code produced with gcc4.x is faster > | then system compiler and has no degrade effect. Some time ago I was > | interested in fast scientific computations and did some primitive > | benchmark tests > | (http://daemon.nanophys.kth.se/~kono/testfcpu) > | > | I just wonder what will happen if you run ubench (compiled for i386) on > | AMD64, will performance overcome amd64 ubench? > | and what would be the point here?=20 the amd64 systems I checked are running amd64 the i386 systems I checked are running i386 and entirely I mean > > I'm just coming in on the tail end of the message (missed the previous > stuff). I recently did some benchmarks between AMD64 and i386 (version 5.= 4) > on the same hardware. I initially saw that the i386 ran faster also.=20 > However, after searching a bit further, I discovered that I had made an > error: the i386 kernel has the SMP stuff compiled into the generic kernel > by default, while the AMD64 (at least on 5.4) does not. It has a separate > kernel file called SMP (as I recall), which adds the SMP line and then do= es > an include for the rest of the generic kernel config file (or something to > that effect). > > Anyway, if you are testing back and forth, it's easy to forget that and e= nd > up accidently testing an i386 with SMP against an AMD64 without SMP. > obviously I checked UP kernels against UP and SMP against SMP but anyway running SMP kernel on single processor systems should not affect= =20 this tests Jo=E3o A mensagem foi scaneada pelo sistema de e-mail e pode ser considerada segura. Service fornecido pelo Datacenter Matik https://datacenter.matik.com.br
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