Date: Mon, 2 Dec 1996 21:17:34 -0500 From: "David S. Miller" <davem@jenolan.rutgers.edu> To: jkh@time.cdrom.com Cc: dyson@FreeBSD.org, dennis@etinc.com, kpneal@pobox.com, hackers@FreeBSD.org, torvalds@cs.helsinki.fi, lm@engr.sgi.com, iain@sbs.de, sparclinux@vger.rutgers.edu Subject: Re: TCP/IP bandwidth bragging Message-ID: <199612030217.VAA18178@jenolan.caipgeneral> In-Reply-To: <7184.849578160@time.cdrom.com> (jkh@time.cdrom.com)
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Date: Mon, 02 Dec 1996 17:56:00 -0800 From: "Jordan K. Hubbard" <jkh@time.cdrom.com> Which is a rather porous argument, to say the least. Morons: "We've proven that our car goes much faster than the competition's does when we have all 4 doors open, due to the superior wind-resistance characteristics of our door design." Competition: "Why in god's name would you want to optimize for that? Who in their right mind would drive with all the doors open?" Morons: "You're just jealous. Beat our open-door numbers or shut up." The situation is not the same. Likewise, testing things like loopback vs actual transmission performance or no-load machine response is just as silly as optimizing for the corner case of driving with your doors open. Who bloody *cares* what the results of a meaningless benchmark are, and why would you ever want to get "better numbers" in an area of trivial measurement where the only real result is to look better on some marketdroid's tally sheet, no doubt obfuscating the code in question and perhaps even degrading performance for the cases your users actually *do* care about. You assertion poorly assumes that all of us agree that the benchmarks in question are in fact meaningless. Many people (people in the "real world") will disagree with you. And as for the marketdroid's tally sheet, that sells machines pinhead. If you think it does not, why does the government spec lmbench numbers for all purchases these days? What concrete numbers are you able to put on that tally sheet? None, because whatever benchmarks the freebsd people are using to perform their improvements are under lock and key, most likely because once the Linux crowd had these at their disposal, we'd fix the problems they show because they'd be trivial. I'm not concerned. I think it is funny how the Linux crowd brags about numbers that anyone can grab the sources for and run for themselves. Whereas the freebsd people brag about performance characteristics that they claim _they_ can test and get numbers for, but the rest of the world has to wonder whether such benchmarks even exist. Those tactics might sound good to Microsoft or (though I hope not) Linux, but the fact that many people use FreeBSD in *real world* situations where performance under extreme load (>1000 users) is paramount means that optimizing for these scenarios counts for far more than chasing some micro-benchmark, and this is what has led John to focus on specific types of performance over others. We wouldn't have it any other way, and you tell me - which is better for us, making thousands of simultaneous TCP/IP connections work properly or shaving another microsecond off a meaningless latency benchmark? I'll give you an hour to answer that question, and you may use a calculator. I prefer the abacus, but thanks. As for scalability. I have numbers (available upon request) where I ran 100 streaming tcp connections between two (very low end) machines in parallel, and the bandwidth and latency numbers scaled very nicely with a variance that was all lost in the noise. Perhaps I should post those results to usenet as well. Also, SparcLinux pushes ~17MB/s over _software_ RAID, thats close to the theoretical maximum for 16-bit synchronous WIDE scsi. I'll be running numbers with 50 or so workstations pummeling a web server over 3 or 4 100baseT lines and 4 10baseT lines, we'll see if your arguments hold. And if they do, I have to thank you, because you have shown me a way in which my system can be improved. And my systems are used in real world high stress situations as well mind you. High load news servers run SparcLinux with zero problems, and performance that blows SunOS/Solaris out of the arena (I can put people in touch with the people who are running these systems if they want verification). So my performance translates into real world, so I don't want to hear your whining over this matter any more. Oh yes, and our main Linux mail server btw runs SparcLinux, over a 100 lists, the most active ones (say 10 or so) have many thousands of subscribers. It is multiuser, holds all my CVS sources, has a full FTP archive, and runs an actively used web server. Oh and btw, this is a dinky 40MHz SparcClassic (4k I and D caches, thats it) with 40MB of ram and two SCSI disks. The load never goes over 4. ---------------------------------------------//// Yow! 11.26 MB/s remote host TCP bandwidth & //// 199 usec remote TCP latency over 100Mb/s //// ethernet. Beat that! //// -----------------------------------------////__________ o David S. Miller, davem@caip.rutgers.edu /_____________/ / // /_/ ><
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