Date: Fri, 23 Mar 2001 20:11:03 +0100 From: Adrian Chadd <adrian@FreeBSD.ORG> To: Robert Watson <rwatson@FreeBSD.ORG> Cc: "Alexey V. Neyman" <avn@any.ru>, "Michael C . Wu" <keichii@peorth.iteration.net>, fs@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: tuning a VERY heavily (30.0) loaded s cerver Message-ID: <20010323201103.A5828@roaming.cacheboy.net> In-Reply-To: <Pine.NEB.3.96L.1010323083844.26010C-100000@fledge.watson.org>; from rwatson@FreeBSD.ORG on Fri, Mar 23, 2001 at 08:44:09AM -0500 References: <Pine.BSF.4.33.0103230044500.11016-100000@srv2.any> <Pine.NEB.3.96L.1010323083844.26010C-100000@fledge.watson.org>
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On Fri, Mar 23, 2001, Robert Watson wrote: > > On Fri, 23 Mar 2001, Alexey V. Neyman wrote: > > > On Thu, 22 Mar 2001, Michael C . Wu wrote: > > > > >(Why is vfs.vmiodirenable=1 not enabled by default?) > > By the way, is there any all-in-one-place description of sysctl tuneables? > > Looking all the man pages and collecting notices about MIB variables seems > > rather tiresome and, I think, pointless. I doubt if they are all > > documented in man pages. > > sysctl(3) describes a number of the constant-named sysctl variables, and a > number of sysctl's are described in the man pages associated with the > features tweaked by the sysctl's. For example, the jail(8) man page > describes the jail.* namespace. However, you're right that there are vast > hoards of under-documented sysctl's. That said, probably only the > "tweakable" (writable) sysctl's need to be documented in the general case, > since many are used for the sole purpose of exporting kernel data for > supported interfaces, whereas the sysctl's are subject to change. For > example, a large number of read-only sysctl's were introduced to support > the non-setgid-kmem operation of top, systat, and various other *stat's > recently. Also, many sysctl's are "self-documenting", in that the > declaration of the sysctl macros in-kernel include a description field. I > don't think sysctl(8) currently knows how to read that field, but if you > look at the SYSCTL definitions in the kernel source, they're probably a > decent starting point. A magic script to extract the sysctl names, types, > and descriptions might be useful.. A while back I started running through the undocumented sysctls and documenting them. I didn't get through all of them, and the main reason I stopped was because there wasn't a nifty way to extract the sysctls short of writing a script to extract them from /usr/src. Someone did point out that you could stuff the sysctl's into an elf segment and only load it when needed, but I don't know much about elf. If someone would like to do this, I'm sure a small group of us (Asmodai? :-P) could walk the sysctl tree again and figure out what the undocumented sysctls are. :-) adrian -- Adrian Chadd "Programming is like sex: <adrian@freebsd.org> One mistake and you have to support for a lifetime." -- rec.humor.funny To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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