[GHC] #8158: Replace IO manager's IntMap with a mutable hash table

[GHC]

#8158: Replace IO manager's IntMap with a mutable hash table
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        Reporter:  bos         |            Owner:  AndreasVoellmy
            Type:  feature     |           Status:  patch
  request                      |        Milestone:  7.8.1
        Priority:  high        |          Version:  7.7
       Component:              |         Keywords:
  libraries/base               |     Architecture:  Unknown/Multiple
      Resolution:              |       Difficulty:  Easy (less than 1 hour)
Operating System:              |       Blocked By:
  Unknown/Multiple             |  Related Tickets:
 Type of failure:  Other       |
       Test Case:              |
        Blocking:              |
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Comment (by AndreasVoellmy):

 In GHC.Event.IntTable.grow, why is a new bucket created, with Arr.write
 called for each item in the bucket?  Couldn't you copy the bucket with a
 single write, copying the bucket in the old array to the new array? I see
 that you want to know the number of items in the bucket, but couldn't you
 count this but avoid the many writes?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8158#comment:16>
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