#8224: Excessive system time -- new IO manager problem? -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Runtime System | Version: 7.7 Resolution: | Keywords: IO Manager, | System Time Operating System: Linux | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #9221 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): In reply to comment:31
Hi, as a developer on 48-core machine, I upvote the issue. I can reproduce it with many programs, e.g. this trivial one:
It is far from clear to me that we should expect the program you cited to run well with `-N`. It allocates heavily and `-N` will use parallel GC on a heavily imbalanced heap. Looking at the eventlog confirms that nearly all of the cores are simply waiting for GC. As expected disabling parallel GC with `+RTS -qg` drastically reduces system time due to reduced synchronization overhead. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8224#comment:33 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler