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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.cs.su.oz.au!metro!metro!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!news.ececs.uc.edu!news.kei.com!news.mathworks.com!howland.erols.net!newspump.sol.net!newsfeeds.sol.net!hammer.uoregon.edu!zephyr.texoma.net!uunet!in3.uu.net!192.207.105.50!prodigy.com!darkstar.prodigy.com!davidsen From: davidsen@tmr.com (bill davidsen) Newsgroups: comp.os.linux.networking,comp.unix.bsd.bsdi.misc,comp.unix.bsd.misc Subject: Re: Linux vs BSD Date: 11 Feb 1997 21:10:04 GMT Organization: TMR Associates, Schenectady NY Lines: 32 Message-ID: <5dqn7c$459u@usenet1y.prodigy.net> References: <32DFFEAB.7704@usa.net> <87d8uqu5vt.fsf@localhost.xs4all.nl> <5daqts$1f74@usenet1y.prodigy.net> <5dd8mp$la7@cynic.portal.ca> NNTP-Posting-Host: darkstar.prodigy.com Originator: davidsen@darkstar.prodigy.com Xref: euryale.cc.adfa.oz.au comp.os.linux.networking:68496 comp.unix.bsd.bsdi.misc:6006 comp.unix.bsd.misc:2507 In article <5dd8mp$la7@cynic.portal.ca>, Curt Sampson <cjs@cynic.portal.ca> wrote: | In article <5daqts$1f74@usenet1y.prodigy.net>, | bill davidsen <davidsen@tmr.com> wrote: | > | >In user or kernel space you should be able to drive the hardware to | >it's limits, and that's what counts. | | With NFS in user space you are in the kernel when you receive an | NFS request. You must then leave the kernel to start processing | the request, re-enter the kernel to do the disk I/O, return to | userland to finish processing the request, and re-enter the kernel | again to send the data. These transitions are expensive, and that | is why an in-kernel implementation of NFS is theoretically more | efficient than an equivalant user-land implementation of NFS. I don't disagree that it can be more efficient, but to blame the user mode nfs for poor performance on a dedicated server over 10Mbit ethernet doesn't seem likely. Your technical point is totally correct, but I think my comment about the use of user space being inherently the cause of slow NFS, as was discussed in earlier posts, is still valid; good user mode code should swamp the transport medium. At the cost of more CPU, absolutely. Any actual measurements tending to prove me wrong are welcome, the only servers I can really load are on TokenRing, and I don't think that's a good place to make the text. -- bill davidsen (davidsen@tmr.com) Company policy prevents me from commenting on the performance of this distributed database. However, the machines on which it runs are called bottleneck and roadblock.