#9221: (super!) linear slowdown of parallel builds on 40 core machine -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #910, #8224 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonmar): Yes, perhaps we should default to -qb0 when -A is larger than some threshold. The mutator parallelism looks not too bad (3.24 out of 4). Was there enough parallelism in the program you were compiling to do better than that? The `MVar`s are probably just the compilation manager: it fires up a thread for every module, and they wait on the results of compiling the modules they depend on. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9221#comment:56 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler