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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!uunet!in2.uu.net!199.94.215.18!news.bbnplanet.com!cam-news-hub1.bbnplanet.com!howland.erols.net!blackbush.xlink.net!fu-berlin.de!irz401!orion.sax.de!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc,comp.arch,comp.benchmarks Subject: Re: benchmarking discussion at Usenix? Date: 18 Jan 1997 15:22:23 GMT Organization: Private BSD site, Dresden Lines: 39 Message-ID: <5bqprf$oar@uriah.heep.sax.de> References: <5am7vo$gvk@fido.asd.sgi.com> <5aonle$8lr@uriah.heep.sax.de> <32D18190.369A6C81@informatik.tu-muenchen.de> <5av0jb$aus@uriah.heep.sax.de> <32DAD3AF.15FB@nas.nasa.gov> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34184 comp.arch:62505 comp.benchmarks:18959 Hugh LaMaster <lamaster@nas.nasa.gov> wrote: > > > Another part is exception and interrupt handling. > > > Hmm. This can't be expressed in a benchmark, hardly. OTOH, if the > > system keeps reasonable statistics, the effect of interrupt and > > exception handling should be forseeable. I estimate this being less > > than ~ 10 % of the total time on a modern machine. > > I guess it depends on whether or not you have to drive > dumb ugly serial ports and such like. You can spend That's why i wrote ``on a modern machine''. :-) > a lot of time handling interrupts with such devices. > One paper at Usenix showed Linux on a Pentium dropping > interrupts/data when driving a 115 Kbps serial port... Hmm, there are perhaps better estimations for interrupt overhead. :) Simply run it on a sufficiently slow machine, and see where the throughput backs off. My old 386sx/16 notebook (with an older version of FreeBSD) has only an on-board 16450-style UART. I can run it up to 38400 bps without flow control, meaning a constant interrupt rate of ~ 4 kHz (3.8 kHz from the serial port, 100 Hz from the system timer, 128 Hz from the statclock) doesn't saturate it. I can increase the baud rate using hardware flow control up to 115 kbps, and this will yield an effective throughput of ~ 75 % of the raw bitrate. This means, the system levels out at ~ 8 kHz maximal interrupt rate. (Needless to say, the clock seriously loses interrupts then.) As i wrote, that's a rough estimation. It's always good to keep a slow machine around for testing. :-)) -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)