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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mira.net.au!news.netspace.net.au!news.mel.connect.com.au!news.syd.connect.com.au!phaedrus.kralizec.net.au!news.mel.aone.net.au!grumpy.fl.net.au!news.webspan.net!www.nntp.primenet.com!nntp.primenet.com!news.maxwell.syr.edu!cpk-news-hub1.bbnplanet.com!cam-news-hub1.bbnplanet.com!news.bbnplanet.com!howland.erols.net!newsxfer.itd.umich.edu!uunet!in3.uu.net!192.244.176.52!news.iij.ad.jp!news.CET.CO.JP!usenet From: Michael Hancock <michaelh@cet.co.jp> Newsgroups: comp.programming.threads,comp.unix.bsd.freebsd.misc Subject: [??] pure kernel vs. dual concurrency implementations Date: Thu, 20 Feb 1997 16:04:52 -0800 Organization: CET Lines: 35 Message-ID: <330CE6A4.63B0@cet.co.jp> NNTP-Posting-Host: chaos.cet.co.jp Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (WinNT; I) Xref: euryale.cc.adfa.oz.au comp.programming.threads:3243 comp.unix.bsd.freebsd.misc:35789 I've been talking to some people who are pro pure kernel threading vs. a dual kernel and userland model when it comes to implementation on a traditional Unix kernel design like FreeBSD. Assuming a well designed strict kernel implementation and a well designed dual concurrent model, say like Digital UNIX, both using FreeBSD as a starting point, which is the way to go? Pro strict kernel people say: * simpler model, less complicated scheduler * high concurrency Dual concurrency people say: * better concurrency * less kernel resource usage problems In DEC's model it doesn't look like you need to worry about converting blocking calls to non-blocking calls as in other userland implementations. Instead they have some kind of upcall mechanism that supplies a new kernel execution context to the userland process so that another thread can be scheduled if the current one is blocked. Pure kernel proponents say that in the time all that was done a new kernel thread could have been switched in. I'm still sitting on the fence. Comments? Regards, Mike Hancock