[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 hvr):

 Replying to [comment:40 bgamari]:
 > I really wish that the build system could record RTS statistics on a
 per-file basis (e.g. perhaps just emitting a log file per GHC process).
 That would make collecting this sort of thing much easier.

 We already emit some extra output (mostly for debugging purposes) to
 `-dumpdir dir`, so there'd be precedent to use output files for logging
 data, rather than dump it to stdout only. So one way would be to extend
 `-Rghc-timing` to optionally take a filename, e.g. `-Rghc-timing=rts-
 stats.log`; similarly for other statistics David pointed out (e.g.
 optimiser stats).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13426#comment:41>
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