[Haskell-cafe] Memory usage with TVar?

[Jake McArthur]

First, see this question about space usage on Stack Overflow:

http://stackoverflow.com/questions/3254758/memory-footprint-of-haskell-data-types

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 <brinchj at gmail.com> 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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