Is anything being done to remedy the soul crushing compile times of GHC?

Ben Gamari ben at
Tue Feb 16 15:28:56 UTC 2016

Eric Seidel <eric at> writes:

> On Tue, Feb 16, 2016, at 05:49, Simon Peyton Jones wrote:
>> * We discussed it in our weekly GHC Skype chat yesterday.  One thing that
>>   would really help is to make it laughably easy to track
>>    - Micro: whether my commit made anything significantly worse
>>       (compile time/allocs, run time/allocs, binary size)
>>    - Our current perf tests only complain when you go outside
>>      a window, but 90% of the lossage might have been from other
>>      patches, which demotivates dealing with it
> It might be useful it phabricator ran the perf tests / nofib for every
> patch and displayed a warning (think a lint warning) if any of the
> metrics got worse. The warning would foster discussion about what caused
> the perf regression and whether it needs to be fixed *before* merging
> the patch.
Indeed we do already run the performance tests but at the moment you
only get a thumbs-up or thumbs-down. One of my tasks for this week is
to try adding better reporting of compiler performance in the testsuite


- Ben
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