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Date:      Tue, 6 Apr 1999 20:57:04 +0100 
From:      paul@originative.co.uk
To:        dillon@apollo.backplane.com, current@FreeBSD.ORG
Subject:   RE: EGCS optimizations
Message-ID:  <A6D02246E1ABD2119F5200C0F0303D10FE93@octopus>

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> -----Original Message-----
> From: Matthew Dillon [mailto:dillon@apollo.backplane.com]
> Sent: 06 April 1999 05:58
> To: current@FreeBSD.ORG
> Subject: EGCS optimizations
> 
> 

....

>     Compiling up /usr/src/usr.sbin with egcs and libc compiled with:
> 
> 	-O2				160 seconds
> 	-O2 -march=pentiumpro		162 seconds
> 	-Os				161 seconds
> 
>     Which leads me to believe that using -Os might be beneficial.
> 

If I'm reading that right you timed how long it took to build
/usr/src/usr.sbin using egcs and libc compiled with the above optimisations?

I doubt that that sort of benchmark is going to say an awful lot about the
performance of the optimisation levels since compiling /usr/sr/usr.sbin is
going to be affected by disk i/o performance far more than it would be by
cpu performance. The relative speed differences of the different egcs/libc
binaries is probably smoothed out by the i/o affects which is why the times
look so similar.

Something that is more cpu bound would be a better benchmark for comparing
the optimisation options.


Paul.


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