Date: Tue, 6 Feb 2001 06:57:48 +0000 (GMT)
From: Terry Lambert <tlambert@primenet.com>
To: dillon@earth.backplane.com (Matt Dillon)
Cc: tlambert@primenet.com (Terry Lambert), phk@critter.freebsd.dk (Poul-Henning Kamp), gibbs@scsiguy.com (Justin T. Gibbs), bright@wintelcom.net (Alfred Perlstein), rjesup@wgate.com (Randell Jesup), mjacob@feral.com (Matthew Jacob), msmith@FreeBSD.ORG (Mike Smith), des@ofug.org (Dag-Erling Smorgrav), dnelson@emsphone.com (Dan Nelson), tanimura@r.dl.itc.u-tokyo.ac.jp (Seigo Tanimura), arch@FreeBSD.ORG
Subject: Re: Bumping up {MAX,DFLT}*PHYS (was Re: Bumping up {MAX,DFL}*SIZ in i386)
Message-ID: <200102060657.XAA12458@usr08.primenet.com>
In-Reply-To: <200102060546.f165kHq58398@earth.backplane.com> from "Matt Dillon" at Feb 05, 2001 09:46:17 PM
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> I think the idea Poul originally articulated -- having simple information > like recommended I/O size, recommended cluster size, and/or maximum I/O > size, is the correct solution. Getting fancy might buy us a percent > or two... it isn't worth the effort. I thought Poul had discarded that idea as unworkable, after having tried to make it work; I got the impression that he still liked the idea, but that he didn't have a way to make it practical (Poul, please correct me if I am misinterpreting your last post). I can't see hints being much more useful than the seek optimization code, which was disabled as a pessimization for most ZBR drives, where the track boundaries were unknown back in the early fictional geometry days (predating SCSI II, where it could be fixed again). I would think that you would want your optimization to work at least 51% of the time for it to be worthwhile, or at least "mostly harmless", and I really have doubts that "hints" would be able to do that. You really don't want to end up with something that makes a microbenchmark run fast, at the expense of real system loads, like some of the stuff that happened in the buffer cache code, historically. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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