[mythtv] Compiling with -Os is better than -O3

Kristian Kalweit kalweit at exorpro.de
Wed Jan 18 06:36:46 UTC 2006

Daniel Kristjansson schrieb:
> The Northwood has a 512KB L2 cache, which should be sufficient for
> -O2/-O3 to be faster than -Os. Generally the script is supposed to use
> -Os for processors with 256 KB or smaller L2/L3 cache and -O2/-O3 for
> ones with a 512KB or larger cache. The benchmarking I did for that
> decision was with gcc 3.x. P4 based cores don't really need some
> of the -O2/-O3 optimizations, like aligning jump targets, but some
> of the newer processors like the Pentium-M and the Athlon chips do
> benefit from the alignment; but they didn't seem to hurt with gcc 3.x.
I have a Via c3-2 cpu and configure is always creating a generic config 
(pentiumpro + O3). Now I found out you have to use manually 
"--enable-proc-opt" to enable the cpu specific flags. What is the cause 
of this? 


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