slow execution of built executables on a Mac

Eric Seidel eric at
Fri Oct 26 21:30:13 UTC 2018

rts_dist_HC is where it builds the various versions of the RTS, right? I noticed a similar slowness building the RTS at ICFP on my MacBook Pro (macOS 10.12). I don't think my battery lasted long enough to get to stage 2.

I'm afraid I don't have any clue why it's gotten so slow, but you're not alone! I did notice that it seems to build many more variants of the RTS than before, but I haven't tried to build GHC in a long time.

On Fri, Oct 26, 2018, at 14:32, Richard Eisenberg wrote:
> Hi devs,
> I have a shiny, new iMac in my office. It's thus frustrating that it 
> takes my iMac longer to build GHC than my trusty 28-month-old laptop. 
> Building devel2 on a fresh checkout takes just about an hour. By 
> contrast, my laptop is done after 30 minutes of work (same build 
> settings). The laptop has a 2.8GHz Intel i7 running macOS 10.13.5; the 
> desktop has a 3.5GHz Intel i5 running macOS 10.13.6. Both bootstrapped 
> from the binary distro of GHC 8.6.1.
> Watching GHC build, everything is snappy enough during the stage-1 
> build. But then, as soon as we start using GHC-produced executables, 
> things slow down. It's most noticeable in the rts_dist_HC phase, which 
> crawls. Stage 2 is pretty slow, too.
> So: is there anything anyone knows about recent Macs not liking locally 
> built executables? Or is there some local setting that I need to update? 
> The prepackaged GHC seems to work well, so that gives me hope that 
> someone knows what setting to tweak.
> Thanks!
> Richard
> _______________________________________________
> ghc-devs mailing list
> ghc-devs at

More information about the ghc-devs mailing list