[GHC] #13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC 8.2

[GHC]

#13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC
8.2
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        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3399,
       Wiki Page:                    |  Phab:D3400, Phab:D3421
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Comment (by dfeuer):

 I made the big hammer smaller (see Phab:D3606). Things don't go utterly
 disastrous, but there are still a few modules over a gigabyte (max
 somewhere around 1700M). I'm not sure exactly which ones; is there a way
 to find out without doing a single-threaded build? I'll try to do some
 profiling and see if I can figure out what's going wrong, exactly.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13426#comment:39>
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