Gary Kline wrote:
On Wed, Mar 14, 2007 at 08:19:49PM -0700, [EMAIL PROTECTED] wrote:
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 :).
--Food for thought and a chuckle too! (not to mention that
it's waaay early, the chickens are still snoring, and I've
only had *one* cup of joe)... I've done some investigation
with optimizing my own code, usually < 1000 lines, and haven't
seen much gain between -O2 and -O3. Loop-unrolling may be
different; one trick that compiler hackers at supercomputer
companies use by default in to unroll small loops. Cray is
one example. Soooo, to get any real gain is going to mean
going thru the most freq used tools (*grep, find, ls) and
hand-tweak. Might buy 5 - 7%.
have a good one,
gary
-Garrett
No problem. -funroll-loops might not buy you too much other than a few
less instructions overall but I'm not sure how intelligent gcc is at
unrolling loops. It seemed like there was a difference between
optimizations in the 4.x branch compared to the 3.4.x sub branch. They
made a lot of improvements in the 4.x branch though.. it's just that
some of those improvements broke code, so that's probably why FreeBSD
doesn't have gcc-4.x in the base system.
Cheers :).
-Garrett
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