[GHC] #4965: 60% performance regression in continuation-heavy code between 6.12 and 7

[GHC]

#4965: 60% performance regression in continuation-heavy code between 6.12 and 7
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    Reporter:  bos               |        Owner:                         
        Type:  bug               |       Status:  new                    
    Priority:  high              |    Milestone:  7.2.1                  
   Component:  Compiler          |      Version:  7.0.1                  
    Keywords:                    |     Testcase:                         
   Blockedby:                    |   Difficulty:                         
          Os:  Unknown/Multiple  |     Blocking:                         
Architecture:  Unknown/Multiple  |      Failure:  Runtime performance bug
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Comment(by bos):

 I checked with HEAD, and performance is back to 6.12.3 levels: allocation
 is about the same, and performance is too, even on the large input.

 However, I notice that -hT doesn't seem to be counting wall clock time
 properly as of 7.0.3, and this persists in HEAD too. Look at the PDFs I
 attached to this bug: the first (with 6.12.3) counts time correctly, while
 the second and third under-count by a large amount. For example, the
 actual wall-clock time for HEAD was the same as 6.12.3, about 15 seconds,
 but the X axis in the chart only runs up to 5 seconds. Weird.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4965#comment:12>
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