Date: Sat, 08 Apr 2000 11:18:37 -0400 (EDT) From: "Alexander N. Kabaev" <kabaev@mail.ru> To: "Alexey N. Dokuchaev" <danfe@inet.ssc.nsu.ru> Cc: freebsd-hackers@FreeBSD.ORG Subject: RE: What are the best gcc optimization options for Pentium 200 M Message-ID: <XFMail.000408111837.kabaev@mail.ru> In-Reply-To: <Pine.LNX.4.10.10004082114170.23805-100000@inet.ssc.nsu.ru>
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I doubt Mandrake gets any significant performance boost from using gcc with optimisation levels beyond -O. They just use this "super optimised" to stand out from all other Linux crowd rather than for any practical purpose. It has been reported several times that optimisation levels O2 ang higher are buggy and known to generate wrong code on several occasions. This was true for gcc 2.7.2.3 and it is still true for gcc 2.95.2. In other words, your attempt to squeese last drop of performance from your system in this way is futile :). The gain you will get is just not worth associated risks. On 08-Apr-00 Alexey N. Dokuchaev wrote: > Hi! > > AFAIK, Linux Mandrake has it's kernel and userland highly optimized for > Pentium architecture. However, they have additional gcc optimization > flags turned on by default, including -O3 and -mfast_math. > > I'm trying to achive maximum performance of my FreeBSD 4.0-RELEASE box, > and going to recompile kernel and world using -Os -pipe options. Is there > any additional flags I might consider turning on (like -mfast_math) to > make both kernel and world work at the top performance I can achieve? > > Of course, I could just man gcc and turn every option I find useful, but I > don't have _that_ much experience with gcc as (I am sure) certain people > on this maillist have. So not to run into any problems in the future > caused by my 'overoptimized' system, I would like to get deep and full > answer here. Thank you in advance. > > System is: genuine intel Pentium 200 MMX proc, 64M memory, FreeBSD 4.0-R > > P.S. Please cc me directly, since I am not the member of this list. > > > Cheers, > > /* Alexey N. Dokuchaev, more commonly | */ > /* known as DAN Fe | mailto:danfe@inet.ssc.nsu.ru */ > /* | ICQ UIN: 38934845 */ > /* Novosibirsk State University | http://inet.ssc.nsu.ru/~danfe/ */ > /* Scientific Study Center Computer Lab | */ > > [Team Assembler] [Team BSD] [Team DooM] [Team Quake] > > -----BEGIN GEEK CODE BLOCK----- > Version: 3.12 > GCS d-@ s+: a--- C++(+++) UBL++++$ P++>$ L+ > E-- W++ N++ o? K? w-- O- M V- PS PE Y+ PGP+ > t+ 5+ X+ R- !tv b++ DI+ D+++ G++ e h !r !y+ > ------END GEEK CODE BLOCK------ > > Microsoft: Where do you want to go today? > Linux: Where do you want to go tomorrow? > FreeBSD: Are you guys coming or what? > > Microsoft: What are we going to rip off today and claim as our own? > > Microsoft: Where do you want to be taken today? > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message ---------------------------------- E-Mail: Alexander N. Kabaev <kabaev@mail.ru> Date: 08-Apr-00 Time: 11:07:16 ---------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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