[GHC] #8027: Adding one call to getNumCapabilities triggers performance nose dive (6X slowdown)

[GHC]

#8027: Adding one call to getNumCapabilities triggers performance nose dive (6X
slowdown)
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  Reporter:  rrnewton                 |          Owner:                  
      Type:  bug                      |         Status:  closed          
  Priority:  normal                   |      Milestone:                  
 Component:  Runtime System           |        Version:  7.6.3           
Resolution:  wontfix                  |       Keywords:                  
        Os:  Unknown/Multiple         |   Architecture:  Unknown/Multiple
   Failure:  Runtime performance bug  |     Difficulty:  Unknown         
  Testcase:                           |      Blockedby:                  
  Blocking:                           |        Related:                  
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Comment(by simonpj):

 I think you are saying that ''inlining a single function, not in an inner
 loop, has a 6x effect on runtime''.  That seems very odd to me.  The only
 examples I've seen with this kind of behaviour is are when a tight loop
 calls an overloaded arithmetic function; inlining it make it turn into a
 few machine instructions.  But `getNumCapabilities` doesn't seem to be
 that kind of beast.

 So I'm still puzzled

 S

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/8027#comment:8>
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