Marc:
Here are the results on my Mac Mini: Intel Core 2 Duo, 2.4 GHz, 3 MB L2 Cache, 8 GB RAM, 1.07 GHz bus speed, Mac OS X 10.6.8,
[Media-Mac-mini-3:gambit-2/gambit/bench] lucier% gsi -v v4.6.6 20130104183242 i386-apple-darwin10.8.0 "./configure 'CC=/pkgs/gcc-4.7.2/bin/gcc -march=core2 -fschedule-insns -frename-registers' '--enable-single-host' '--enable-multiple-versions'"
My observations:
I dismissed any differences that were < 20%.
Under that criteria, the new default did not lead to the best performance for dynamic, early, paraffins and nboyer, for which the old benchmarks setting of 10,000K minimum heap won.
The new default heap size beat the old benchmark setting of 10,000K minimum heap for cpstak, diviter, divrec, mbrot, sumfp, and string.
For no programs did the old default heap size beat the other settings.
Perhaps you could characterize the programs that have each property. My guess is that the new default heap size beats -:m10000 for programs that allocate a lot of memory but have few objects survive each GC, while -:m10000 wins for programs that allocate a lot of memory and have a lot of objects live at the end of each GC.
Brad