[GHC] #13586: ghc --make seems to leak memory

[GHC]

#13586: ghc --make seems to leak memory
-------------------------------------+-------------------------------------
           Reporter:                 |             Owner:  (none)
  MikolajKonarski                    |
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Linux
       Architecture:  x86_64         |   Type of failure:  Compile-time
  (amd64)                            |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #13379
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 (This is probably not reproducible with a small example.) When I build
 this project with `cabal build`

 https://github.com/LambdaHack/LambdaHack/commit/138123ab13edd4db6c8143720af68b6ec4a1726e

 the peek memory, as observed with `top`, is 10G*. When I instead interrupt
 the compilation with `^C` at the following point (compilation of this file
 take a couple of minutes, so it's easy to interrupt):

 {{{
 [123 of 123] Compiling
 Game.LambdaHack.SampleImplementation.SampleMonadServer (
 Game/LambdaHack/SampleImplementation/SampleMonadServer.hs,
 dist/build/Game/LambdaHack/SampleImplementation/SampleMonadServer.o )
 }}}

 and then restart and continue to the end, peek memory usage in either of
 the two compilation parts is 5G*. So it seems `ghc --make` keeps some data
 that is either eventually not used or could as well be read on demand
 instead of kept in memory. Confirmed with 8.2.1-rc1 as well, but it's not
 trivial to compile due to restrictive upper bounds of many packages.

 *exact numerical values are made up

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13586>
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