Performance regression GHC 7.8.4 to GHC HEAD

Testing with HEAD 02343998

Baseline: GHC 7.8.4

ghc-config 7.8.4
cabal unpack haskell-src-exts
cd haskell-src-exts-1.16.0.1/
cabal install --dependencies-only
time (cabal clean && cabal build)

real	2m38.696s
user	5m17.256s
sys	3m44.732s

Test : GHC HEAD

ghc-config 7.11.20150112

cabal install --dependencies-only
time (cabal clean && cabal build)

real	3m35.027s
user	6m45.664s
sys	5m15.220s

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	hvr
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

It would be helpful if someone felt able to characterise this more. For example:

• Do the two invocations of cabal install compile exactly the same number of modules, each containing exactly the same code?
• Which modules take longer to compile? Or does everything take a little longer?

Thanks

Simon

Maybe another example to investigate is cabal install attoparsec, which went from 30 secs on GHC 7.4 to 90 secs on GHC 7.10:

attoparsec-0.10.4.0	GHC-7.10.0.20141227 text-1.2.0.4 # 92668ms
attoparsec-0.10.4.0	GHC-7.8.4	    text-1.2.0.4 # 65736ms
attoparsec-0.10.4.0	GHC-7.6.3	    text-1.2.0.4 # 27520ms
attoparsec-0.10.4.0	GHC-7.4.2	    text-1.2.0.4 # 31303ms

PS: the numbers above may be a bit distorted; I just re-timed a reinstall of only attoparsec-0.10.4.0:

attoparsec-0.10.4.0	GHC-7.10.0.20141227 # 29s
attoparsec-0.10.4.0 	GHC-7.8.4	    # 26s
attoparsec-0.10.4.0	GHC-7.6.3	    # 13s
attoparsec-0.10.4.0	GHC-7.4.2	    # 14s

Trac metadata

Trac field	Value
TypeOfFailure	OtherFailure → CompileTimePerformance

added Pnormal label