Date: Fri, 12 Mar 2004 14:01:50 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-amd64@FreeBSD.ORG Subject: Re: Peer review of AMD64/FreeBSD article Message-ID: <200403121301.i2CD1oQC076505@lurza.secnetix.de> In-Reply-To: <4051A841.9020205@thejemreport.com>
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Jem Matzan <valour@thejemreport.com> wrote: > I've just finished writing this article comparing performance between an > Athlon64 in 32-bit and 64-bit mode using FreeBSD: > > http://www.thejemreport.com/lab64/amd64vsi386.php > > (this is a temporary address which will later redirect to the published > article) > > I've checked it over twice for fact accuracy, but I would like other > eyes to look at it before it goes to press. I haven't spell-checked it > yet, so don't worry about that... I just want to make sure I haven't > made any factual errors. I like the article very much. Well done. I also appre- ciate the fact that you refrained from spoiling the compa- rison with colorful graphics. :-) There are just two things which seem a bit unclear to me. In the very first paragraph it sounds like hyperthreading would always be a performance win, but that's not the case. I've had applications that ran slightly faster when hyper- threading was turned off. If I remember correctly, soft- ware that does many concurrent things and I/O benefits most from hyperthreading, while pure numbercrunching jobs run faster with hyperthreading switched off. (I'm not saying that you should repeat all your benchmarks with hyper- threading off, mind you. I just think that the remark in the first paragraph sounds a little bit misleading. YMMV.) The second point is that the gcc "benchmark" seems a bit unfair for me, because you're really measuring _different_ things when compiling something for i386 and for amd64. The compiler is producing different code, it has to opti- mize differently (particularly because of the different register sets of the processors), so you can't really compare the results. Also take into account that the amd64 code generation engine of gcc is rather new, while the i386 code generation is very mature. Apart from that, I would rather call this "benchmark" synthetic, because nobody buys an Opteron to compile things all day long. Well, except for the FreeBSD package building people, maybe. :-) In relation to that, the oggenc benchmark is certainly much more realistic. It would have been nice to have some video decoding / encoding benchmarks, too (e.g. mplayer / menco- der, transcode, ffmpeg, whatever). Well, just my 2 cents. :-) Regards Oliver -- Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things." -- Doug Gwyn
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