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Date:      Tue, 06 Apr 1999 06:51:29 +0000
From:      Pavel Narozhniy <pasha@sim.net.ua>
To:        current@FreeBSD.ORG
Subject:   Re: EGCS optimizations
Message-ID:  <3709AEF1.446B9B3D@sim.net.ua>
References:  <Pine.BSF.4.05.9904052216100.55808-100000@zippy.dyn.ml.org> <199904060525.WAA04269@apollo.backplane.com>

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Matthew Dillon wrote:
> 
> :Totally informally, I replaced libc (compiled with -O2) with one compiled
> :with -mpentiumpro and -O6, and compiling kdebase seemed to run a bit
> :slower (GNU make took longer to traverse directories and egcs took a bit
> :longer to run).
> :
> :>     Which leads me to believe that using -Os might be beneficial.
> :
> :Have you tried anything beyond -O2?
> :
> :- alex
> 
>     There is nothing beyond -O2.  Well, there's -O3, which tries to
>     inline static functions, but that typically isn't beneficial because
>     it really bloats up the code and subroutine calls on intel cpus are
>     very fast.
> 
>     The only other optimization that might be useful is -fomit-frame-pointer,
>     but it makes debugging impossible.
I don't have oppurtunity to use CURRENT, but on 3.1-RELEASE and 2.2.8
-fomit-frame-pointer applied to kernel compilation leads to system
crash.
 If you want to reproduce this, compile kernel with -O
-fomit-frame-pointer, reboot, and try, for example, to build kernel with
make -j 16 ;)


>                                         -Matt
>                                         Matthew Dillon
>                                         <dillon@backplane.com>

-- 
Pavel Narozhniy
nic-hdl: PN395-RIPE
http://www.sumy.net


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