Hey, when going through Simon-nofib-notes, I stumbled over this thread from March 2017, when I hadn't yet subscribed to this list: https://mail.haskell.org/pipermail/ghc-devs/2017-March/013887.html. Joachim and Simon were trying to pin-point seemingly random regressions and improvements of ~5% to `binary-trees`. It's hard to say in retrospect, but I suspect this is the same effect I experienced in #15333 and I'm about to fix in #15999, e.g. that small changes to allocations lead to big, uncorrelated jumps in runtime performance due to GC. Just wanted to record this here for posterity. Cheers Sebastian Hi,

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* > But: binary-trees runtime increases by 5%. *> >* David: might you look to see if there is any obvious reason for this *>* regression? We could just accept it, but it's always good to know *>* why, and to document it.

Am Dienstag, den 07.03.2017, 22:55 +0000 schrieb Simon Peyton Jones via ghc-devs: * Turns out that my commit Add rule mapFB c (λx.x) = c fixed that regression:https://perf.haskell.org/ghc/#revision/2fa44217c1d9722227297eefb0d6c6aed7e12...

Maybe there is just a performance cliff there, and these jumps don’t really mean anything.

Greetings, Joachim