Optimizationn questions?

[youshi10 at u.washington.edu]

On Thu, 15 Mar 2007, Danny Pansters wrote:

> On Thursday 15 March 2007 02:16, Gary Kline wrote:
>> 	Two quick one for kernel and/or compiler wizards:  first, is
>> 	a 400Mz processor considered a 586 (for my KERNELCONF file)?
>
> Think its 686 (but really, leaving 486 and 586 in isn't going to slow down
> booting or anything!) I always say: Use GENERIC unless you have a good reason
> not to.
>
>> 	Second, is it safe to do a buildworld with -O3?  If there are
>
> No. It's not supported if things break.
>
>> 	stability concerns, I'll go with the default when I rebuild my
>> 	6.2 systems.
>
> The defaults should be fine. Also, like I said consider just using GENERIC and
> load the odd kmod if needed. Generally it's less headache and equal
> performance.
>
>> 	thanks in advance,
>>
>> 	gary
>
> Cheers,
>
> Dan

As Dan and Gary said -O3 isn't supported, and in many cases that "level of optimization" gets filtered out while compiling sections of FreeBSD.

Besides, I've compiled stuff with -O3 and various optimizations in Gentoo Linux before, and let me say that it caused a great deal of headaches... that's why I stick with -O2 now, because it's better to have something in executable shape and a bit slower (arguably because some optimizations slow things down) than it is to have something run fast and break all the time.

Some food for thought :).

-Garrett