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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!howland.erols.net!bloom-beacon.mit.edu!senator-bedfellow.mit.edu!usenet From: ghudson@mit.edu (Greg Hudson) 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: 04 Jan 1997 23:57:12 -0500 Organization: Massachusetts Institute of Technology Lines: 36 Sender: ghudson@the-light-fantastic.MIT.EDU Message-ID: <x7dhgkwius7.fsf@the-light-fantastic.MIT.EDU> References: <6OBgx1wrNgB@me-tech.PFM-Mainz.de> <1997Jan4.095835.23223@wavehh.hanse.de> NNTP-Posting-Host: the-light-fantastic.mit.edu In-reply-to: cracauer@wavehh.hanse.de's message of Sat, 4 Jan 97 09:58:35 GMT X-Newsreader: Gnus v5.1 Xref: euryale.cc.adfa.oz.au comp.unix.bsd.misc:1872 comp.unix.bsd.bsdi.misc:5508 comp.unix.bsd.freebsd.misc:33556 comp.unix.bsd.netbsd.misc:5055 Here's a (very recent) correction to your comparison web page: > * You loose pages in swap space when you fork under certain conditions > of heavy memory load. The parent process grows. This can be a major > problem for long-running self-forking daemons like sendmail and INN. > This problem is supposed to be fixed in OpenBSD (in FreeBSD anyway). A fix for this problem, in the NetBSD VM, was developed by an OpenBSD developer (Niklas Hallqvist, niklas@appli.se). It's been in OpenBSD for a while, but until quite recently it had a bug which could cause systems to crash under heavy load (a VM object is freed while still in use). Around Christmas, Niklas developed a fix for the crashing bug, and it was committed to NetBSD-current on January 3. In terms of releases, NetBSD 1.2 still has the swap leak problem, while I believe OpenBSD 2.0 has the crashing bug instead. > OpenBSD is supposed to have some performance fixes, although still > far away from FreeBSD's memory performance. There was a performance fix bandied about for low-swap conditions. Unfortunately, my memory is fuzzy here, but I believe it was committed to both NetBSD and OpenBSD, possibly in slightly different forms. There may be other things OpenBSD has done to speed up the VM system, but I haven't heard about them. > 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.