Hello Simon, Friday, June 16, 2006, 3:48:06 PM, you wrote:
char *ghc_rts_opts = "-A10m"; Do you have some evidence that -A10m is a good default? Better than -A6m, or -A16m, for example? GHC currently runs with -H6m by default.
of course, "-a6m" is not worser than "-a10m". but "-h" is not a good alternative because after memory usage grows above 6 mb, ghc starts to do minor GCs after each 256 kb allocated. with "-A6m" number of minor GCs will be dramatically cut off i just quickly tested non-optimized compilation of my program with "-A6m" and with "-H6m" (ghc 6.4.2.20060609) - wall clock time of compilation was 63 seconds against 76 seconds, while memory usage was 70 mb against 68 mb btw, now i use "+RTS -c" in my compilations - it works fine. i'm happy :)
2) i propose to write "L2 cache size detection" code and use it in GHC 6.6 RTS to setup initial value of "-A" option. in order to allow program tune itself to any cpu architecture, with cache sizes ranging from 128kb to 4mb. this will allow low-level cpus to run significantly faster on some algorithms (up to 2x, as i said above) and can give 5-10% speedup for high-level cpus, that is also not so bad :)
That sounds like a good plan. I've been experimenting with PAPI recently (http://icl.cs.utk.edu/papi/) which can tell you the size of your caches, but it requires kernel patches.
for me, Windows compatibility is most important issue :) -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com