[GHC] #6104: Regression: space leak in HEAD vs. 7.4

[GHC]

#6104: Regression: space leak in HEAD vs. 7.4
---------------------------------+------------------------------------------
    Reporter:  simonmar          |       Owner:  simonpj                     
        Type:  bug               |      Status:  new                         
    Priority:  highest           |   Milestone:  7.6.1                       
   Component:  Compiler          |     Version:  7.5                         
    Keywords:                    |          Os:  Unknown/Multiple            
Architecture:  Unknown/Multiple  |     Failure:  Compile-time performance bug
  Difficulty:  Unknown           |    Testcase:                              
   Blockedby:                    |    Blocking:                              
     Related:                    |  
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Comment(by simonpj):

 Interface file size:
 {{{
 GHC 7.4.1 -O     -rw-rw-r-- 1 simonpj GHC  5983 Jul 16 15:21 T6104.hi
 HEAD             -rw-rw-r-- 1 simonpj GHC 10487 Jul 16 14:08 T6104.hi
 }}}
 So, yes, the interface file is a lot bigger. Looking more closely, this
 seems largely accidental.  The code in HEAD is broken into more functions,
 each of which is individually small enough to be below the inlining-
 creation threshold.

 I compiled Cabal with -O, and compared the total size (with `ls -l`) of
 the `.o` files and `.hi` files with both compilers:
 {{{
                    HEAD change over 7.4.1
 .o file size            -6%
 .hi file size           +8%
 }}}
 So yes, interface file size is up, but not massively, and .o file size is
 down.

 This does not seem to account for the originally-reported doubling of
 residency! And (I've checked) that doubling is still happening.

 Conclusion: I don't think it's just bigger interface files. I there is
 some other space leak too.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6104#comment:9>
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