Recent performance regressions

Joachim Breitner mail at
Thu Aug 6 08:08:17 UTC 2015

Dear Developers,

yesterday, there were three commits showing up at
Author: Ben Gamari <bgamari.foss at>
Drop custom mapM impl for []

nofib/allocs/cryptarithm2   + 64.55%
nofib/allocs/k-nucleotide    - 5.03%
nofib/time/fannkuch-redux    - 3.62%

Did someone forget to run nofib here, or is this serious drop in
performance in one case expected and something we condone? In that
case, it should have been clearly noted in the commit message!
Author: RyanGlScott < at>

Make Exception datatypes into newtypes

nofib/time/cryptarithm1  + 7.22%

If you look at the graph, this is quite reproducible:;hl=b12dba78
but I have no idea how that change could have that effect. Maybe some
weird cache effect due to binary sizes or different code layout? It
would be great to understand that!
commit 22bbc1cf209d44b8bb8897ae7a35f9ebaf411b10
Author: Takano Akio <aljee at>

Make sure that `all`, `any`, `and`, and `or` fuse (#9848)

nofib/allocs/circsim 	 - 4.02%
nofib/allocs/multiplier  - 8.70%

At least I do not only have bad news...


Joachim “nomeata” Breitner
  mail at joachim-breitner.de
  Jabber: nomeata at  • GPG-Key: 0xF0FBF51F
  Debian Developer: nomeata at
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