[Haskell-cafe] Memory

Bernie Pope bjpop at csse.unimelb.edu.au
Tue Feb 17 00:46:00 EST 2009

On 17/02/2009, at 3:56 PM, Jeff Douglas wrote:

> 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?

I don't think there should be a space leak in the code you posted.

On my mac, OS X 10.5.6, GHC version 6.8.3, it appears to run in  
constant space with or without optimisation.

GHCi seems to gobble a little bit of memory (but that could be  

My terminal application does gobble memory for a while (and then frees  
it), but that is presumably because it is hammering the buffer (and it  
nearly sets my lap on fire when running).

Perhaps you could post more details about how it is compiled, and what  
versions of things are being used.

How are you detecting the leak (via top?).


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