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Re: gzip performance test

On Friday 25 May 2001 04:06, David Edelsohn wrote:
> gzip built with which options?  gzip-1.2.4a CFLAGS seems to
> default to -O.
> 	I tried gzip-1.2.4a on powerpc-ibm-aix4.3.3.0.  The results depend
> on the options:
> With -O2, gcc-3.0 prerelease is slightly faster, matching your results.
> With -O3 -funroll-all-loops, gcc-2.95 is slightly faster.
> With -O3 -funroll-all-loops -fstrict-aliasing, they're statistically
> identical.
> David

I certainly wouldn't want to use unroll-all-loops on a genral basis since the 
increase in TLB and  cache consumption plus swapping can degrade instead of 
improving performance.


1)  gzip spends a fair share of its time in glibc.  If you don't use 
different glibcs (through LD_LOAD_PATH) your results will be flattened
and could look not significative

2)  Part of gcc 3.0 improvement will be due to additional optimizations.  
Until -O2 is redefined to include them you will not be getting them so it 
is unfair to compare -O2 with -O2

3)  At least with the Byte benchmark the unholy gcc 2.96 provides code 
significantly faster than gcc 2.95 so if gcc 3.0 id not better than gcc 2.95 
it means it is worse than the evil gcc 2.96


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