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To: Andrew <andrew@ugh.net.au>
cc: questions@freebsd.org
Subject: Re: Compiling kernel with optimisation 
In-reply-to: Your message of "Mon, 13 Jan 1997 03:32:44 +1100."
             <Pine.BSF.3.95.970113032400.1179D-100000@mopsy.hobart.tased.edu.au> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Sun, 12 Jan 1997 09:24:20 -0800
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>I just noticed that when compiling a kernel it is done with the -O flag.
>Would there be much speed improvement in the sytem if it was done with
>-O3? Would this break the kernel or is the added time it takes to compile
>not worth the benfits?

   It has very little effect on performance and optimizations levels > "-O"
have traditionally been broken in gcc.

>I'd try myself but it takes me 4.5 hours just to do the kernel with -O :-(

   Then you need to add some memory, then. It shouldn't be anywhere near that
slow.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project