#15938: Hadrian's recompilation check is extremely slow -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.8.1 Component: Build System | Version: 8.6.2 (Hadrian) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Looking at the eventlog under threadscope suggests that we are hitting some very peculiar GC behavior. Hadrian is linked against the threaded, profiled, eventlog-enabled RTS but with `+RTS -N1`. From t=1 until around t=22 seconds we have very frequent GCs, with time roughly roughly evenly between major and minor collections. The productivity during this period is roughly 20%. Intriguingly, increasing the allocation area size to 30MB reduces the start-up GC time to around 1.5 seconds, with mutator time remaining around 12 seconds (a productivity of roughly 90%). By the way, I am bootstrapping and building Hadrian with GHC 8.4.3. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15938#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler