#7257: Regression: pinned memory fragmentation
-------------------------------------+--------------------------------------
 Reporter:  jwlato                   |          Owner:                  
     Type:  bug                      |         Status:  new             
 Priority:  normal                   |      Component:  Compiler        
  Version:  7.6.1                    |       Keywords:                  
       Os:  Unknown/Multiple         |   Architecture:  Unknown/Multiple
  Failure:  Runtime performance bug  |       Testcase:                  
Blockedby:                           |       Blocking:                  
  Related:                           |  
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 In certain cases, ghc-7.6.1 seems to have much worse memory behavior than
 7.4.  I have attached a simplified program that I believe demonstrates the
 problem.

 {{{
 -- compiled with ghc-7.4.2 -rtsopts -O2
 ./Foo  +RTS -s
 200001
    3,549,666,928 bytes allocated in the heap
       55,512,376 bytes copied during GC
      335,555,096 bytes maximum residency (10 sample(s))
        3,787,576 bytes maximum slop
              453 MB total memory in use (0 MB lost due to fragmentation)
 }}}

 {{{
 -- compiled with ghc-7.6.1 -rtsopts -O2
    2,699,298,272 bytes allocated in the heap
       55,077,544 bytes copied during GC
      327,246,968 bytes maximum residency (11 sample(s))
        3,767,408 bytes maximum slop
              858 MB total memory in use (398 MB lost due to fragmentation)
 }}}

 One of our applications uses 3-4GB more RAM when compiled with ghc-7.6.1
 compared to 7.4, all due to memory fragmentation issues.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7257>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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