[GHC] #9520: Running an action twice uses much more memory than running it once

[GHC]

#9520: Running an action twice uses much more memory than running it once
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              Reporter:  snoyberg    |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:  Linux       |     Architecture:  x86_64 (amd64)
       Type of failure:  Runtime     |       Difficulty:  Unknown
  performance bug                    |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Comment (by snoyberg):

 As pointed out by Bryan Vicknair in the cafe thread, my first example in
 my previous comment does not always leak memory. In particular, I had to
 turn on optimizations (either `-O` or `-O2`) to get it to happen.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9520#comment:6>
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