First, see this question about space usage on Stack Overflow: http://stackoverflow.com/questions/3254758/memory-footprint-of-haskell-data-... Next, apply this knowledge not only to Ints, but also to tuples and lists. There's your memory usage. - Jake On Wed, Feb 1, 2012 at 10:29 AM, Johan Brinch wrote:

Here's the example program: https://gist.github.com/1cbe113d2c79e2fc9d2b

When I run the program (which maintains a list inside an STM TVar), I get the following statistics:

...

./Test +RTS -s     176,041,728 bytes allocated in the heap     386,794,976 bytes copied during GC      69,180,224 bytes maximum residency (7 sample(s))      42,651,080 bytes maximum slop             179 MB total memory in use (0 MB lost due to fragmentation)

                                   Tot time (elapsed)  Avg pause  Max pause  Gen  0       336 colls,     0 par    0.44s    0.44s     0.0013s    0.0033s  Gen  1         7 colls,     0 par    0.39s    0.40s     0.0570s    0.1968s

 INIT    time    0.00s  (  0.00s elapsed)  MUT     time    0.23s  (  0.23s elapsed)  GC      time    0.83s  (  0.84s elapsed)  EXIT    time    0.00s  (  0.00s elapsed)  Total   time    1.06s  (  1.07s elapsed)

 %GC     time      77.9%  (78.3% elapsed)

 Alloc rate    749,153,093 bytes per MUT second

 Productivity  22.1% of total user, 22.0% of total elapsed

How come this program uses 179 MB of memory? I'm on a 64-bit machine where 2'000'000 integers uses 32 MB. Where does the overhead come from?

-- Johan Brinch

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