Tejun Heo 1ed1328792 sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem
Note: This commit was originally committed as d59cfc09c32a but got
      reverted by 0c986253b939 due to the performance regression from
      the percpu_rwsem write down/up operations added to cgroup task
      migration path.  percpu_rwsem changes which alleviate the
      performance issue are pending for v4.4-rc1 merge window.
      Re-apply.

The cgroup side of threadgroup locking uses signal_struct->group_rwsem
to synchronize against threadgroup changes.  This per-process rwsem
adds small overhead to thread creation, exit and exec paths, forces
cgroup code paths to do lock-verify-unlock-retry dance in a couple
places and makes it impossible to atomically perform operations across
multiple processes.

This patch replaces signal_struct->group_rwsem with a global
percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader
side and contained in cgroups proper.  This patch converts one-to-one.

This does make writer side heavier and lower the granularity; however,
cgroup process migration is a fairly cold path, we do want to optimize
thread operations over it and cgroup migration operations don't take
enough time for the lower granularity to matter.

Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/g/55F8097A.7000206@de.ibm.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
2015-09-16 12:53:17 -04:00
..
2015-09-01 13:00:04 -07:00
2015-06-25 11:49:31 +03:00
2015-09-10 16:42:49 -07:00
2015-09-04 11:46:02 -07:00
2015-09-09 08:33:31 -07:00
2015-09-09 08:33:31 -07:00
2015-06-03 14:13:41 +09:00
2015-09-08 16:33:16 -07:00
2015-09-01 13:00:04 -07:00
2015-09-09 08:33:31 -07:00
2015-05-13 12:04:55 -05:00
2015-03-25 20:28:11 -04:00
2015-08-03 12:01:54 -04:00
2015-08-06 16:17:25 -04:00
2015-06-01 14:35:56 -06:00
2015-09-01 15:52:41 +02:00
2015-09-04 16:54:41 -07:00
2015-02-12 18:54:15 -08:00
2015-09-08 15:35:28 -07:00
2014-12-19 22:55:06 +01:00
2015-01-21 19:21:30 +01:00
2015-08-20 10:20:11 +03:00
2014-12-31 13:06:50 -05:00
2015-06-24 17:49:45 -07:00
2015-07-17 08:41:53 -06:00
2015-05-12 10:46:53 +02:00
2015-06-01 14:33:35 +02:00
2015-06-19 15:18:28 +02:00
2015-09-08 15:35:28 -07:00
2015-09-08 15:35:28 -07:00
2015-03-16 21:45:54 +11:00
2015-05-05 13:40:42 -06:00
2015-08-27 19:40:58 -04:00
2015-08-06 00:14:59 +02:00
2015-06-25 12:06:45 +02:00
2015-08-18 15:49:15 -07:00
2015-07-28 08:50:42 +01:00
2015-09-06 16:27:10 +02:00
2015-04-29 17:17:17 -05:00
2015-01-04 23:11:43 -05:00
2015-04-14 16:49:05 -07:00
2015-06-24 17:49:41 -07:00
2015-09-11 16:42:39 -07:00
2015-09-08 14:35:59 -07:00
2015-07-21 10:39:05 -07:00
2015-06-25 04:20:04 -04:00
2015-08-17 13:32:56 -05:00
2015-08-18 11:56:13 -06:00
2015-07-01 19:40:18 -07:00
2015-03-11 17:56:28 -04:00
2015-09-10 13:29:01 -07:00
2015-09-10 13:29:01 -07:00
2015-09-10 13:29:01 -07:00
2015-09-08 15:35:28 -07:00
2015-04-12 21:03:31 +02:00
2015-01-25 23:17:28 -05:00
2015-06-19 01:18:14 +02:00
2015-08-17 15:40:20 +02:00
2015-06-10 19:14:04 +08:00
2015-05-27 12:58:04 -07:00
2015-05-26 15:23:23 +02:00
2015-06-25 01:13:43 +02:00
2015-02-13 21:21:41 -08:00
2015-04-11 15:53:35 -04:00
2015-06-25 17:00:40 -07:00
2015-06-25 17:00:39 -07:00
2015-08-17 11:25:28 -07:00
2015-07-22 15:27:29 -07:00
2015-08-28 16:27:27 -07:00
2015-04-11 22:29:44 -04:00
2015-04-14 18:06:47 -07:00
2015-06-12 17:26:57 -07:00
2015-03-24 09:48:14 -07:00
2015-09-08 15:35:28 -07:00
2015-09-10 13:29:01 -07:00