[GHC] #8224: Excessive system time -- new IO manager problem?

[GHC]

#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):

 Good idea. I still see about the same amount of system time. The
 {{{__ticket_spin_lock}}} is still at the top:

 {{{
  Events: 1K cycles
 #
 # Overhead          Command       Shared Object
 Symbol
 # ........  ...............  ..................
 ...................................
 #
     34.41%  excessive_syste  [kernel.kallsyms]   [k] __ticket_spin_lock
     11.94%  excessive_syste  [kernel.kallsyms]   [k]
 default_send_IPI_mask_sequence_phys
      4.48%  excessive_syste  [kernel.kallsyms]   [k] update_sd_lb_stats
      3.39%  excessive_syste  [kernel.kallsyms]   [k] native_write_msr_safe
      1.86%  excessive_syste  [kernel.kallsyms]   [k] __slab_free
      1.85%  excessive_syste  [kernel.kallsyms]   [k] idle_cpu
      1.55%  excessive_syste  libc-2.15.so        [.] 0x7e175
      1.39%  excessive_syste  [kernel.kallsyms]   [k] perf_event_alloc
      1.36%  excessive_syste  [kernel.kallsyms]   [k] dequeue_task_fair
      1.21%           :47802  [kernel.kallsyms]   [k] page_remove_rmap
      1.09%  excessive_syste  [kernel.kallsyms]   [k] mmap_region
      0.99%  excessive_syste  [kernel.kallsyms]   [k] __init_waitqueue_head
      0.94%  excessive_syste  [kernel.kallsyms]   [k] memset
      0.92%  excessive_syste  [kernel.kallsyms]   [k] do_futex
      0.90%  excessive_syste  [kernel.kallsyms]   [k] perf_event_mmap_ctx
      0.89%  excessive_syste  [kernel.kallsyms]   [k]
 kmem_cache_alloc_trace
      0.87%  excessive_syste  libpthread-2.15.so  [.] __deallocate_stack
      0.86%  excessive_syste  excessive_system    [.] waitCondition
      0.86%  excessive_syste  [kernel.kallsyms]   [k] __rwsem_do_wake
      0.85%  excessive_syste  [kernel.kallsyms]   [k]
 get_page_from_freelist
      0.84%  excessive_syste  [kernel.kallsyms]   [k] find_vma
      0.84%  excessive_syste  excessive_system    [.] s6t3_info
      0.83%  excessive_syste  [kernel.kallsyms]   [k] sys_read
      0.82%  excessive_syste  [kernel.kallsyms]   [k] kfree
      0.78%  excessive_syste  [kernel.kallsyms]   [k]
 __raw_write_unlock_irq.constprop.31
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8224#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler