Date: Sat, 22 Jun 2002 12:46:15 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Mike Silbersack <silby@silby.com> Cc: Lucky Green <shamrock@cypherpunks.to>, freebsd-hackers@FreeBSD.ORG Subject: Re: LINT CPU features table Message-ID: <20020622174615.GA53971@dan.emsphone.com> In-Reply-To: <20020622115350.D43492-100000@patrocles.silby.com> References: <007d01c219c3$102d8150$206694d1@LUCKYVAIO> <20020622115350.D43492-100000@patrocles.silby.com>
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In the last episode (Jun 22), Mike Silbersack said: > On Sat, 22 Jun 2002, Lucky Green wrote: > > Let me turn my original inquiry into an offer: I volunteer to write > > the section for the Handbook or other documentation detailing the > > various CPU options in LINT if somebody who fully understands what > > these options do is willing to spend 30 minutes on the phone with > > me answering questions about the options. > > Despite your enthusiasm, it's still a rather pointless exercise. To > make explaining the cpu options worthwhile, you must show that only > specifying I686 is sufficiently more optimal than specifying > I686/I586/I486/I386. I think he's referring to the flotilla of CPU feature options, mainly aimed at AMD and old Cyrix processors. A while back I went through all the places the I?86_CPU defines were used and determined that the only option that degraded performace when added to a kernel that didn't need it was I386_CPU; due to the 386's lack of locking primitives. For 486 and higher chips it doesn't matter if you have all three I[456]86_CPU defined or just the one you need. Most of the code activated by the options are specialized bcopy routines accessed through an indirect pointer, or initialization code used only once during bootup. -- Dan Nelson dnelson@allantgroup.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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