[GHC] #7602: Threaded RTS performing badly on recent OS X (10.8?)

[GHC]

#7602: Threaded RTS performing badly on recent OS X (10.8?)
-------------------------------+--------------------------------------------
    Reporter:  simonmar        |       Owner:  thoughtpolice
        Type:  bug             |      Status:  new          
    Priority:  normal          |   Milestone:  _|_          
   Component:  Runtime System  |     Version:  7.7          
    Keywords:                  |          Os:  MacOS X      
Architecture:  x86_64 (amd64)  |     Failure:  None/Unknown 
  Difficulty:  Unknown         |    Testcase:               
   Blockedby:  7678            |    Blocking:               
     Related:                  |  
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Comment(by thoughtpolice):

 OK. Clang is kind of being an issue at the moment so my patch is on hold
 (see #7678.) Right now my change is localized in ```GCTDecl.h``` behind an
 ```#ifdef``` so it's nothing more than a configurable performance
 optimization on Darwin.

 I think first I will just look at the raw differences between:

   * clang, with the slow, non-inline pthread calls.
   * clang, using this change to steal an inline TLS variable
   * gcc 4.7.2, using register variables.

 (I don't particularly care about llvm-gcc too much - it's already slow
 whether or not it's using clang or llvm-gcc, and llvm-gcc will be removed
 anyway.)

 Afterwords, we can look at what storing the TLS variable in a local will
 save us performance wise, and decide on a default.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7602#comment:17>
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