On Mon, 2006-01-16 at 20:55 -0700, John P Poet wrote: > Is there an easy way to configure Myth such that it builds with -Os > instead of -O3? I have been editing the configure script before > running it, but was wondering if there is a better way.
> My frontend machine has a Intel Northwood 3.2GHz HT P4 and 512MB of > RAM. With this configuration, I have found that compiling myth with > -Os is better than -O3. Have you changed your compiler? 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. gcc 4+ does some additional optimization at -O2 and -O3 which may be hurting you as far as cache performance is concerned. You might want to try disabling the new optimizations in -02... See http://gcc.gnu.org/onlinedocs/gcc-4.0.2/gcc/Optimize-Options.html And http://gcc.gnu.org/onlinedocs/gcc-3.3/gcc/Optimize-Options.html -- Daniel _______________________________________________ mythtv-dev mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
