#8224: Excessive system time -- new IO manager problem? -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Runtime System | Version: 7.7 Resolution: | Keywords: IO Manager, Operating System: Linux | System Time Type of failure: Runtime | Architecture: x86_64 (amd64) performance bug | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------- Comment (by AndreasVoellmy): Even with MVars removed and each thread simply waiting (see attached program) it takes 200ms system time with -N32. Here is a perf recording with call stack info; here is most of the first entry: {{{ # Events: 1K cycles # # Overhead Command Shared Object Symbol # ........ ............... .................. ................................... # 51.37% excessive_syste [kernel.kallsyms] [k] __ticket_spin_lock | --- __ticket_spin_lock | |--88.44%-- _raw_spin_lock_irq | | | |--89.17%-- get_signal_to_deliver | | do_signal | | do_notify_resume | | int_signal | | | | | |--94.68%-- __lll_lock_wait_private | | | | | --5.32%-- epoll_wait | | | | | |--67.64%-- 0x7ff06806d533 | | | 0x8758b4830558b48 | | | | | |--18.03%-- 0x7ff06806690b | | | 0x8758b4830558b48 | | | | | --14.33%-- 0x7ff068062b2b | | 0x8758b4830558b48 | | | |--8.08%-- acct_collect | | do_exit | | do_group_exit | | get_signal_to_deliver | | do_signal | | do_notify_resume | | int_signal | | __lll_lock_wait_private | | }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8224#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler