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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!spool.mu.edu!uwm.edu!newsfeeds.sol.net!hammer.uoregon.edu!arclight.uoregon.edu!super.zippo.com!zdc!szdc!szdc-e!news From: "John S. Dyson" <dyson@freebsd.org> Newsgroups: comp.unix.bsd.misc,comp.unix.bsd.bsdi.misc,comp.unix.bsd.freebsd.misc,comp.unix.bsd.netbsd.misc Subject: Re: Differences between BSDI, FreeBSD and NetBSD? Date: Sun, 05 Jan 1997 14:16:54 -0500 Organization: John S. Dyson's home machine Lines: 31 Message-ID: <32CFFE26.41C67EA6@freebsd.org> References: <6OBgx1wrNgB@me-tech.PFM-Mainz.de> <1997Jan4.095835.23223@wavehh.hanse.de> <x7dhgkwius7.fsf@the-light-fantastic.MIT.EDU> 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.misc:1883 comp.unix.bsd.bsdi.misc:5527 comp.unix.bsd.freebsd.misc:33683 comp.unix.bsd.netbsd.misc:5090 Greg Hudson wrote: > > > For example, I wrote above that the filesystem buffer cache of > > FreeBSD is better, because it can grow dynamically. > > It's worth noting that historically most operating systems initially > become much slower, for normal applications, when they integrate the > VM and buffer cache. Typically what happens is that one side of the > cache starves the other for pages, and some frequent operation becomes > very slow. Proper tuning can solve the problem, but don't assume that > an integrated buffer cache necessarily means improved performance; it > just means more flexibility for the system at runtime. > The FreeBSD merged VM/Buffer Cache scheme was written understanding the limitations of the older schemes. I think that you'll find that there are few, if any negative effects of the FreeBSD scheme. However, there are substantial positive effects. It is relatively easy to do a merged VM/Buffer Cache scheme so that you don't have the negative consequences. You just need to know how to handle the memory competition, and how to allocate the memory effectively. A good example of the effectiveness of the FreeBSD scheme is the response to the "sync bomb". FreeBSD is barely affected by it compared to other OSes. NetBSD isn't affected much, of course, because the buffer cache is so small and limited in size. John dyson@freebsd.org