#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 slyfox): I think it's expected if you have GC work imbalance. Some GC work-stealing threads sit in yield loop at: http://git.haskell.org/ghc.git/blob/HEAD:/rts/sm/GC.c#l981 Imbalance can be seen seen as: '''+RTS -sstderr''' shows it as '''Parallel GC work balance: 80.03% (serial 0%, perfect 100%)'''. and can be tuned by heap size or allocation area ('''-A'''). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9221#comment:70 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler