Bug 888380

Description of problem:
Top shows nearly 100% system time on all CPUs, some commands like 'ps auxw' or 'cat /proc/1234/cmdline' hang in an unkillable state.  Running 'perf top' shows this:

Samples: 10M of event 'cycles', Event count (approx.): 1034786006755                                                       
 82.37%  [kernel]                      [k] _raw_spin_lock_irqsave
  8.60%  libjvm.so                     [.] SpinPause
  2.97%  libjvm.so                     [.] ParallelTaskTerminator::offer_termination(TerminatorTerminator*)
  2.32%  [kernel]                      [k] compact_zone
  1.35%  [kernel]                      [k] migrate_pages
  0.67%  [kernel]                      [k] compact_checklock_irqsave.isra.15
  0.54%  [kernel]                      [k] __zone_watermark_ok
  0.19%  [kernel]                      [k] isolate_migratepages_range
  0.17%  [kernel]                      [k] _raw_spin_unlock_irqrestore
[...]

Version-Release number of selected component (if applicable):
kernel-3.6.9-2.fc17.x86_64

How reproducible:
Not very.  Our server is running Java processes with UJMP, doing multi-threaded matrix calculations and gets into this state every half an hour or so and then many processes freeze (e.g., 'pstree -a' does but 'pstree -p' does not, memtester hangs failing to mlock, etc.) until the Java jobs are killed.

If it was easy to reproduce it would be a nice DOS attack.

The processes are big, allocating around 20GB of virtual memory, 10GB resident according to top, five or six threads each, but the machine has plenty of RAM, disk, and CPU.
  
Actual results:
All CPUs (24 with dual hexa-core processors and hyperthreading) are showing 99.7%sy (or similar) in 'top' and many processes freeze in kernel calls.

Expected results:
Not hanging!