[GHC] #9221: (super!) linear slowdown of parallel builds on 40 core machine

[GHC]

#9221: (super!) linear slowdown of parallel builds on 40 core machine
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        Reporter:  carter            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.8.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #910, #8224       |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 > Ideally I'd like to put GHC in a debugging mode were the first time a
 thread blocks on a black hole the program crashes with a stack trace ;-).
 Edit rinse repeat until they're all gone.

 You may be interested in Phab:D1216, which builds on the the DWARF-based
 statistical profiling support that I have [[DWARF/80Status|in the works]]
 for provide profiling of black-hole entry events. As-written this patch
 only captures the head of the stack, although this could be changed to
 provide a deeper stacktrace.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9221#comment:52>
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