[GHC] #5259: Heap used by compacting collector larger than heap used without.

[GHC]

#5259: Heap used by compacting collector larger than heap used without.
-----------------------------+----------------------------------------------
  Reporter:  r6              |          Owner:  simonmar
      Type:  bug             |         Status:  closed  
  Priority:  high            |      Milestone:  7.2.1   
 Component:  Runtime System  |        Version:  6.12.3  
Resolution:  worksforme      |       Keywords:          
  Testcase:                  |      Blockedby:          
Difficulty:                  |             Os:  Linux   
  Blocking:                  |   Architecture:  x86     
   Failure:  None/Unknown    |  
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Changes (by simonmar):

  * status:  new => closed
  * resolution:  => worksforme


Comment:

 I suspect this is fixed.  Your program didn't work, because `[0..]` has
 type `[Word8]` and thus only has 256 elements, so I had to modify it
 slightly:
 {{{
 l = map (BS.replicate (1024^2 `div` 2) . fromIntegral) [(0::Int)..]
 }}}

 with this change, I get the same behaviour with and without `-c`.  First,
 with `+RTS -M100m -c -s`:

 {{{
 eap exhausted;
 Current maximum heap size is 104857600 bytes (100 MB);
 use `+RTS -M<size>' to increase it.
      155,883,256 bytes allocated in the heap
      103,920,168 bytes copied during GC
      103,930,080 bytes maximum residency (9 sample(s))
          878,368 bytes maximum slop
              105 MB total memory in use (0 MB lost due to fragmentation)
 }}}

 and with `+RTS -M100m -s`:

 {{{
 Heap exhausted;
 Current maximum heap size is 104857600 bytes (100 MB);
 use `+RTS -M<size>' to increase it.
      155,883,256 bytes allocated in the heap
      162,745,832 bytes copied during GC
      103,930,064 bytes maximum residency (9 sample(s))
        1,046,320 bytes maximum slop
              105 MB total memory in use (0 MB lost due to fragmentation)
 }}}

 I got the same results with 7.0.3 and the current master.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5259#comment:4>
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