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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!feed1.news.erols.com!super.zippo.com!zdc!szdc!news From: "John S. Dyson" <dyson@freebsd.org> Newsgroups: comp.unix.bsd.freebsd.misc,comp.unix.bsd.bsdi.misc,comp.sys.sgi.misc Subject: Re: no such thing as a "general user community" Date: Wed, 02 Apr 1997 08:09:44 -0500 Organization: John S. Dyson's home machine Lines: 40 Message-ID: <33425A98.167EB0E7@freebsd.org> References: <331BB7DD.28EC@net5.net> <5hnam9$393@hoopoe.psc.edu> <5hp7p3$1qb@fido.asd.sgi.com> <33402E4E.6937@indy.celebration.net> <5hso11$4ji@fido.asd.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (X11; I; FreeBSD 3.0-CURRENT i386) Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:38307 comp.unix.bsd.bsdi.misc:6552 comp.sys.sgi.misc:29619 Steve Alexander wrote: > > In article <33402E4E.6937@indy.celebration.net>, > John S. Dyson <dyson@indy.celebration.net> wrote: > >A read/write system call is not null unless it is special cased. > > I agree that this test is not well named, but I have to side with Larry in that > it is a much more representative measure than say, getpid(). > My argument isn't that the measurement isn't relevent, it is that the LMBENCH suite doesn't always measure what it implies. Additionally, it requires understanding what it is really doing, and it's limitations in order to interpret it's results. For me, it is a very valuable tool, but it is difficult to draw conclusions about real world behavior from it, without understanding what it is. I think that the community is being done a disservice when even the numbers are posted, without a disclaimer that the LL benches are limited in scope. BOGOMIPS is also a LL benchmark, and of course LMBENCH is much more comprehensive and complete (and frankly accurate), but one needs to recognize that the benchmarks are of the same kind. (I know, I know, BOGOMIPS is practically a CPU only benchmark, but the question that I am posing is "how does it relate to application performance?") So, when you say "more representative measure", I am going to ask, "measure of what?" Don't get me wrong, as a developemnt tool and as a measure of the efficiency of non-scaled kernel performance or light load kernel performance, it is a valuable tool. Note that it is difficult from the benchmark results themselves to determine if the kernel performance will have any impact on application performance. If OS(1) is two times faster at a given operation than OS(2) on a single application, non scaled operation, and both of the LL performance figures are in the very low percents of overhead, then what value are the results for those who are running applications, when the higher load results are vastly different? John