On 8 June 2012 01:39, Andrew Myers
Hi Cafe, I'm working on inspecting some data that I'm trying to represent as records in Haskell and seeing about twice the memory footprint than I was expecting.
That is to be expected in a garbage-collected language. If your program requires X bytes of memory then allocators will usually trigger garbage collection once the heap reaches a size of 2X bytes. If it didn't do this then every allocation would require a GC. You can change this factor with +RTS -F option. E.g., +RTS -F1.5 should reduce this to only 50% overhead, but will trigger more frequent garbace collections. To find the actual residency (live data) see the output of +RTS -s There may still be room for improvement. For example, you could try turning on the compacting GC -- which trades GC performance for lower memory usage. You can enable it with +RTS -c The reason that -hc runs slowly is that it performs a GC every 1s (I think). You can change this using the -i option. E.g. -i60 only examines the heap every 60s. It will touch almost all your live data, so it is an inherently RAM-speed bound operation. HTH, / Thomas