#10818: GHC 7.10.2 takes much longer to compile some packages -------------------------------------+------------------------------------- Reporter: kazu-yamamoto | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by j.waldmann): Here is some more timing info for travis: I added "time" measurements around the cabal commands https://travis-ci.org/jwaldmann/haskell-tpdb/builds/109678365 So the timing they are showing is indeed wallclock. Still, sometimes "user time" was larger than "real time". I suspect this is because cabal uses `-j $ncpus` by default. I think for `cabal install --dependencies` this means to compile them in parallel, which is OK, but for `cabal build` this means to pass `-j $ncpus` to ghc, which decreases performance, and sometimes drastically so. So, I put explicit `-j 1` for these commands, https://travis-ci.org/jwaldmann/haskell-tpdb/builds/109683703 and now the timings look at least somewhat reasonable. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10818#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler