theory one:

are you setting the intree gmp flag? and/or dont have gmp the library installed? maybe your ghc is using integer simple!

theory two: dont set -j greater than about 8 or perhaps 16? (some parts of ghc are slower on too paralle a setup?)

those are my two off the cuff guesses

you could also look at system monitor to see if your'e being IO bound or memory or CPU bound

(possible failure siutation: the repo is under dropbox or something and dropbox is eating your memory bandwidth trying to sync stuff?)

On Fri, Oct 26, 2018 at 2:33 PM Richard Eisenberg <rae@cs.brynmawr.edu> 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
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