Date: Sun, 12 Jan 1997 20:31:17 -0200 (EDT) From: Joao Carlos Mendes Luis <jonny@mailhost.coppe.ufrj.br> To: dg@root.com Cc: andrew@ugh.net.au, hackers@freebsd.org Subject: Re: Compiling kernel with optimisation Message-ID: <199701122231.UAA22599@gaia.coppe.ufrj.br> In-Reply-To: <199701121724.JAA25580@root.com> from David Greenman at "Jan 12, 97 09:24:20 am"
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#define quoting(David Greenman) // >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. Well, the NetBSD team has managed to compile their kernel with -O6 and -Wall, but they had to change lots of things.. I don't know what do you call "little effect on performance", but 5% gain would be enough to make me think about. Unfortunately, I don't have any measurements (and even don't know how to do them). I tried -O6 once, and 2 files were broken in compile time !!! (Wow) I did dare once more, fixing those files and running that kernel. Panic in 5 seconds. :( I'm now trying -m486, and found no problem 'til now. Jonny -- Joao Carlos Mendes Luis jonny@gta.ufrj.br +55 21 290-4698 ( Job ) jonny@cisi.coppe.ufrj.br Network Manager UFRJ/COPPE/CISI Universidade Federal do Rio de Janeiro
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