marlowsd: > On 28/04/2009 17:25, Johannes Waldmann wrote: >> Thanks for your comments. >> >> >>> Check whether it is GC-bound by using +RTS -sstderr. >> >> Well yes, it does a lot of GC (there's no way for the compiler >> to optimize away the list of primes) because that was the point >> of the example: to confirm (or disprove) >> that GC hurts parallelism (at the moment). >> >> >> INIT time 0.00s ( 0.00s elapsed) >> MUT time 13.23s ( 7.98s elapsed) >> GC time 14.12s ( 14.11s elapsed) >> EXIT time 0.00s ( 0.00s elapsed) >> Total time 27.35s ( 22.09s elapsed) >> >> %GC time 51.6% (63.9% elapsed) >> >> >>> Try a recent HEAD snapshot if you can, or wait for 6.12.1. >> >> I did with 6.11.20090425 and it coredumps with +RTS -N2 (on x86_64) > > That's worrying, but I don't see a core dump here. Here are my results: > > GHC 6.11.20090429 -N1: > > INIT time 0.00s ( 0.00s elapsed) > MUT time 13.52s ( 13.64s elapsed) > GC time 21.25s ( 21.23s elapsed) > EXIT time 0.00s ( 0.00s elapsed) > Total time 34.76s ( 34.87s elapsed) > > GHC 6.11.20090429 -N2 -qg0 -qb: > > INIT time 0.00s ( 0.00s elapsed) > MUT time 14.40s ( 7.21s elapsed) > GC time 18.35s ( 9.22s elapsed) > EXIT time 0.00s ( 0.00s elapsed) > Total time 32.75s ( 16.44s elapsed) > > which, if I'm not mistaken, is super-linear speedup :-) > > Don't forget the -qg0 -qb flags with HEAD, these flags usually give the > best parallel GC performance at the moment. For the release this might > be the default, I still have to do some more experiments.
I've added this interesting bit of info to the par perf. wiki: http://haskell.org/haskellwiki/Performance/Parallel _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users