Compiled code performance worsens when module names are long enough

Attached to this report is an example where by simply renaming a module, performance degrades 2.5 times.

#diff long-modname-ver.hs short-modname-ver.hs
2c2
< import VeryLongModuleName
---
> import ShortM

#diff VeryLongModuleName.hs ShortM.hs
1c1
< module VeryLongModuleName
---
> module ShortM

#ghc --make -O2 -Wall long-modname-ver.hs

#ghc --make -O2 -Wall short-modname-ver.hs

#time -p ./long-modname-ver > /dev/null
real 55.90
user 55.17
sys 0.51

#time -p ./short-modname-ver > /dev/null
real 22.23
user 21.97
sys 0.10

According to some measures by dons, the threshold seems to be at module length 10 (see attached graph).

Some further disussion on this thread http://thread.gmane.org/gmane.comp.lang.haskell.glasgow.user/16037.

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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