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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #9370
Closed
Open
Issue created Jul 27, 2014 by Carter Schonwald@carterDeveloper

unfolding info as seen when building a module depends on flags in a previously-compiled module

I've observed a blowup in ghc memory usage when invoked with parallel build flags.

to reproduce

cabal get xmlhtml-0.2.3.2
cabal install xmlhtml-0.2.3.2 --only-dependencies
cd xmlhtml-0.2.3.2 

then

 cabal clean ; cabal configure --ghc-options="-j4" ; time cabal build -j4 -v3

will take quite a while and use > 1gb of ram

whereas

 cabal clean ; cabal configure --ghc-options="-j1 ; time cabal build -j1  -v3

will use < 150mb of ram.

Based upon the output of cabal build -j4 -v3, it looks like the parallel build is spending a lottt more time in the simplifier passes. I'm not sure what changes between the parallel and sequential builds to change this. I'll try to dig into this more in a few days, but recording this problem now before i forget. (though of course any insights would be appreciated)

Trac metadata
Trac field Value
Version 7.8.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
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Blocking
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Operating system
Architecture
Edited Mar 09, 2019 by rwbarton
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