inbuninbu:
Hello All,
The kind people at #haskell suggested I come to haskell-cafe for questions about haskell performance issues. I'm new to haskell, and I'm having a hard time understanding how to deal with memory leaks.
I've been playing with some network server examples and I noticed with each new connection, the memory footprint increases by about 7k However, the leaks don't seem to have anything to do with the networking code. Actually I get a huge leak just from using using 'forever'.
import Control.Monad import System.IO
main = forever $ putStrLn "hi"
When I run it for a few seconds with profiling...
total time = 0.36 secs (18 ticks @ 20 ms) total alloc = 54,423,396 bytes (excludes profiling overheads)
Can this be right?
did you compile with optimisations on? $ ghc -O2 A.hs --make $ time ./A +RTS -sstderr 17,880 bytes maximum residency (1 sample(s)) 18,984 bytes maximum slop 1 MB total memory in use (0 MB lost due to fragmentation) Generation 0: 9951 collections, 0 parallel, 0.07s, 0.07s elapsed Generation 1: 1 collections, 0 parallel, 0.00s, 0.00s elapsed INIT time 0.00s ( 0.00s elapsed) MUT time 4.45s ( 16.08s elapsed) GC time 0.07s ( 0.07s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 4.52s ( 16.16s elapsed) %GC time 1.5% (0.5% elapsed) Alloc rate 1,173,414,505 bytes per MUT second Productivity 98.5% of total user, 27.5% of total elapsed ./A +RTS -sstderr 4.52s user 10.61s system 93% cpu 16.161 total So it's allocating small cells, frequently, then discarding them -- and running in constant space. Looking further, forever :: (Monad m) => m a -> m b forever a = a >> forever a Well, here, the result is thrown away anyway. And the result is (), so I'd expect constant space. Looks good to me. Did you run it without optimisations, on , perhaps? -- Don