Changes between Version 8 and Version 9 of Status/Nov07

Dec 4, 2007 2:15:36 PM (7 years ago)



  • Status/Nov07

    v8 v9  
    120120Roshan James did an internship at MSR in 2006 during which he and I (Simon M) worked on parallelising the major collections in GHC's generational garbage collector.  We had a working algorithm, but didn't observe much speedup on a multi-processor.  Since then, I rewrote the implementation and spent a large amount of time with various profiling tools, which uncovered some cache-unfriendly behaviour.  We are now seeing some speedup, but there is more tweaking and measuring still to be done. 
    122 This parallel GC is likely to be in GHC 6.10.  If you have enough cores and your program does enough GC, you might even see a speedup for purely single-threaded Haskell programs. 
     122This parallel GC is likely to be in GHC 6.10.  Note that parallel GC is independent of whether the Haskell program itself is parallel - so even single-threaded Haskell programs (e.g. GHC itself) should benefit from it. 
    124124The other side of the coin is to parallelise the ''minor'' collections.  These are normally too small and quick to apply the full-scale parallel GC to, and yet the whole system still has to stop to perform a minor GC.  The solution is almost certainly to allow each CPU to GC its own nursery independently.  There is existing research describing how to do this, and we plan to try applying it in context of GHC.