On 17 February 2016 at 07:40, Evan Laforge
My impression from the reddit thread is that three things are going on:
1 - cabal has quite a bit of startup overhead 2 - ghc takes a long time on certain inputs, e.g. long list literals. There are probably already tickets for these.
In my experience GHC startup overhead (time) has increased quite a lot somewhere in 7.x. I don't know if it's the cause, but perhaps dyn libs may be part of the reason. I'm not sure because I once (7.8 I believe) tried to build without dynlink support and couldn't measure a substantial improvement. So, if you start ghc(i) for the first time from a spinning disk, it's very noticeable and quite a delay. Once it's cached, it's fast, so I think it's primarily due to reading stuff from disk. Just to mention the ideal overhead: anything below 400ms is small enough to not disrupt the flow and feels responsive. Go over 1s and it breaks.