Nicholas Piggin fd851a3cdc
spin loop primitives for busy waiting ...
Current busy-wait loops are implemented by repeatedly calling cpu_relax()
to give an arch option for a low-latency option to improve power and/or
SMT resource contention.
This poses some difficulties for powerpc, which has SMT priority setting
instructions (priorities determine how ifetch cycles are apportioned).
powerpc's cpu_relax() is implemented by setting a low priority then
setting normal priority. This has several problems:
- Changing thread priority can have some execution cost and potential
impact to other threads in the core. It's inefficient to execute them
every time around a busy-wait loop.
- Depending on implementation details, a `low ; medium` sequence may
not have much if any affect. Some software with similar pattern
actually inserts a lot of nops between, in order to cause a few fetch
cycles with the low priority.
- The busy-wait loop runs with regular priority. This might only be a few
fetch cycles, but if there are several threads running such loops, they
could cause a noticable impact on a non-idle thread.
Implement spin_begin, spin_end primitives that can be used around busy
wait loops, which default to no-ops. And spin_cpu_relax which defaults to
cpu_relax.
This will allow architectures to hook the entry and exit of busy-wait
loops, and will allow powerpc to set low SMT priority at entry, and
normal priority at exit.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org >
Signed-off-by: Nicholas Piggin <npiggin@gmail.com >
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au >
2017-06-28 22:49:11 +10:00
2017-05-04 16:08:52 +05:30
2017-05-08 17:15:13 -07:00
2017-04-25 09:04:29 +02:00
2017-05-23 20:32:10 +02:00
2017-04-12 18:51:01 +02:00
2017-02-20 12:16:11 +01:00
2017-01-25 11:51:39 +05:30
2017-01-09 10:04:09 +09:00
2017-03-23 12:22:32 -07:00
2017-04-08 17:45:28 +02:00
2017-05-04 12:05:32 -07:00
2017-05-02 11:02:41 +02:00
2017-03-13 20:42:34 +00:00
2017-04-05 08:52:33 -07:00
2017-05-09 12:51:49 +02:00
2017-04-21 10:45:01 -04:00
2017-03-28 23:33:30 +05:30
2017-05-08 19:03:25 -07:00
2017-05-08 17:15:13 -07:00
2017-05-24 15:43:57 -04:00
2017-04-24 21:49:15 +02:00
2017-05-11 10:44:22 -07:00
2017-05-15 12:51:38 +02:00
2017-05-16 10:24:27 +02:00
2017-04-11 16:29:54 +01:00
2016-12-14 10:49:33 -08:00
2017-05-02 17:59:33 -07:00
2017-05-11 11:12:26 -07:00
2017-05-01 12:37:29 +02:00
2017-05-04 12:31:02 -04:00
2017-04-30 22:17:36 +09:00
2017-03-28 17:58:07 -07:00
2017-05-08 17:15:15 -07:00
2017-05-10 15:33:45 +02:00
2017-04-26 15:58:22 +01:00
2017-04-27 18:00:16 -04:00
2017-05-23 11:01:28 -04:00
2017-05-09 15:15:47 -07:00
2017-05-09 15:15:47 -07:00
2016-12-05 14:31:24 -05:00
2016-12-22 22:58:37 -05:00
2016-12-01 14:45:08 +01:00
2017-02-08 14:54:12 +00:00
2017-02-16 10:08:41 +05:30
2017-04-28 18:09:59 -04:00
2016-12-15 12:13:31 +00:00
2017-03-30 09:35:54 +02:00
2017-05-02 10:16:05 -04:00
2017-03-02 08:32:46 +01:00
2017-04-20 12:09:55 -06:00
2017-04-20 12:09:55 -06:00
2017-03-03 01:45:23 +01:00
2017-05-01 14:09:21 -07:00
2017-02-10 15:52:24 -05:00
2017-04-08 11:25:38 -06:00
2017-03-29 11:25:48 -06:00
2017-02-27 20:54:05 +02:00
2017-05-22 20:50:11 +02:00
2017-05-12 15:43:10 -07:00
2017-02-02 10:20:16 -07:00
2017-01-25 13:17:47 -05:00
2017-04-11 14:38:43 -04:00
2017-05-11 14:19:00 -04:00
2017-02-12 21:52:19 -05:00
2017-04-11 14:38:43 -04:00
2017-03-13 21:51:49 -07:00
2017-01-27 15:08:35 -07:00
2017-04-26 23:54:06 -04:00
2017-03-30 09:37:20 +02:00
2016-12-22 09:25:45 -08:00
2017-04-05 21:57:07 +08:00
2017-03-21 06:44:32 +01:00
2017-02-14 08:29:56 -07:00
2017-01-10 11:14:27 -05:00
2017-01-10 11:14:27 -05:00
2017-04-11 09:06:17 +09:00
2017-05-01 13:52:24 -07:00
2017-04-02 14:31:49 -06:00
2017-05-01 16:15:18 -07:00
2017-04-20 14:56:58 +02:00
2017-04-18 20:41:12 +02:00
2017-04-20 12:09:55 -06:00
2017-05-03 08:50:52 -07:00
2017-03-01 20:32:25 +01:00
2017-02-27 23:09:29 -08:00
2016-12-21 10:16:05 -08:00
2017-04-18 18:01:52 +02:00
2017-01-14 19:32:40 -05:00
2017-03-16 09:51:10 +01:00
2017-03-02 08:42:40 +01:00
2017-04-17 18:37:27 +02:00
2017-04-11 16:29:54 +01:00
2017-01-31 08:32:13 +11:00
2017-05-08 17:15:11 -07:00
2017-04-11 08:57:54 +09:00
2017-05-08 17:15:11 -07:00
2017-03-02 08:42:31 +01:00
2017-04-10 19:17:27 +08:00
2017-03-24 22:02:56 +08:00
2017-05-13 17:52:16 -07:00
2017-03-02 08:42:24 +01:00
2017-03-07 14:15:27 -08:00
2016-12-05 19:01:16 -05:00
2017-04-08 17:59:23 +02:00
2017-01-20 14:32:39 -08:00
2017-03-03 01:45:28 +01:00
2017-03-06 22:06:59 +01:00
2017-05-05 15:54:45 +08:00
2017-04-12 12:42:14 +09:00
2017-05-05 18:49:20 -07:00
2017-03-16 16:56:19 -07:00
2017-04-26 23:57:53 +02:00
2017-04-20 13:47:46 +05:30
2017-02-24 17:46:55 -08:00
2017-03-17 23:51:36 +05:30
2017-04-18 11:42:36 -07:00
2017-05-04 18:06:17 +02:00
2017-04-20 16:31:06 +02:00
2017-01-31 09:03:20 +05:30
2017-03-02 08:42:38 +01:00
2016-12-25 11:04:12 +01:00
2017-04-10 17:15:02 +02:00
2017-04-05 12:27:25 +02:00
2017-04-05 12:27:28 +02:00
2017-05-04 08:24:40 -06:00
2017-05-08 17:15:11 -07:00
2017-03-02 08:42:36 +01:00
2017-03-21 18:44:17 -07:00
2017-03-12 23:54:07 -07:00
2017-03-09 16:39:58 -08:00
2017-02-03 08:28:25 -08:00
2017-04-04 11:22:42 +09:00
2017-05-03 10:04:56 -07:00
2017-03-03 01:45:28 +01:00
2017-04-27 05:13:04 -04:00
2016-12-05 19:01:16 -05:00
2017-05-25 13:44:28 -04:00
2017-03-29 14:50:21 -06:00
2017-03-01 20:32:25 +01:00
2017-05-12 15:57:15 -07:00
2017-01-31 13:23:09 -05:00
2017-04-30 01:26:34 -04:00
2017-05-04 11:44:37 -04:00
2017-05-04 11:44:41 -04:00
2017-02-10 15:19:48 +01:00
2016-12-05 15:13:58 +01:00
2017-02-06 08:54:01 +01:00
2017-02-20 13:51:07 +01:00
2017-04-10 17:37:36 +02:00
2016-12-05 18:58:32 -05:00
2017-05-08 17:15:13 -07:00
2016-12-25 17:21:22 +01:00
2017-03-29 00:00:29 +02:00
2017-04-21 14:17:27 -06:00
2017-05-03 15:52:10 -07:00
2017-03-21 10:15:47 +02:00
2017-04-08 15:13:36 +01:00
2017-03-25 16:32:24 +00:00
Merge branches 'for-4.11/upstream-fixes', 'for-4.12/accutouch', 'for-4.12/cp2112', 'for-4.12/hid-core-null-state-handling', 'for-4.12/hiddev', 'for-4.12/i2c-hid', 'for-4.12/innomedia', 'for-4.12/logitech-hidpp-battery-power-supply', 'for-4.12/multitouch', 'for-4.12/nti', 'for-4.12/upstream' and 'for-4.12/wacom' into for-linus
2017-05-02 11:01:10 +02:00
2017-03-21 15:24:01 +01:00
2017-04-05 18:11:48 +02:00
2017-04-14 21:49:56 +02:00
2017-02-24 17:46:54 -08:00
2017-03-09 11:48:47 -08:00
2017-04-02 07:01:53 -07:00
2017-05-04 19:15:35 -07:00
2017-05-03 12:38:20 -07:00
2017-04-20 12:16:10 -06:00
2017-02-13 21:44:03 -05:00
2017-04-28 12:28:45 +02:00
2017-04-27 16:34:29 -04:00
2017-01-27 11:32:26 -05:00
2017-02-11 20:59:41 -05:00
2017-02-11 20:59:41 -05:00
2017-05-24 16:27:14 -04:00
2016-12-20 09:48:44 -08:00
2017-04-04 09:48:23 -06:00
2017-03-28 22:32:42 -07:00
2017-05-03 08:50:52 -07:00
2017-03-24 20:51:49 -04:00
2017-03-22 15:42:17 +01:00
2017-04-18 13:40:00 -05:00
2017-04-19 13:58:51 -05:00
2017-04-25 13:20:46 -07:00
2017-05-04 18:06:17 +02:00
2017-02-24 17:46:56 -08:00
2017-03-23 00:06:17 +01:00
2017-05-08 17:15:12 -07:00
2017-01-05 15:01:55 -06:00
2017-03-22 14:20:54 -07:00
2017-02-20 10:52:23 -08:00
2017-03-06 14:40:04 +00:00
2016-12-24 11:46:01 -08:00
2017-05-03 15:52:09 -07:00
2017-05-08 17:15:10 -07:00
2017-01-12 14:33:16 +01:00
2017-03-07 09:37:28 -08:00
2017-03-31 17:13:30 -07:00
2017-04-23 15:51:26 +09:00
2017-02-27 18:43:47 -08:00
2016-12-14 16:04:08 -08:00
2017-02-01 09:13:58 +01:00
2017-05-02 15:53:46 -07:00
2016-12-27 14:49:03 -05:00
2017-05-08 17:15:11 -07:00
2017-04-04 14:10:11 -07:00
2017-04-04 14:10:12 -07:00
2017-03-02 08:42:28 +01:00
2017-01-19 12:45:33 +01:00
2017-03-22 20:11:35 -06:00
2017-05-17 21:50:27 -04:00
2017-05-08 17:15:14 -07:00
2017-05-03 15:52:10 -07:00
2016-12-12 18:55:06 -08:00
2016-12-25 17:21:23 +01:00
2017-05-10 11:29:23 -07:00
2017-04-19 20:27:50 +02:00
2017-03-08 21:10:01 +01:00
2017-02-21 17:21:32 -08:00
2017-05-04 14:01:24 -07:00
2017-04-16 10:06:25 -06:00
2017-03-09 13:27:17 -08:00
2017-02-03 16:35:42 -05:00
2017-03-08 09:38:43 +01:00
2017-01-23 11:37:13 -08:00
2017-03-16 09:57:07 +01:00
2017-03-02 12:17:22 -08:00
2017-03-28 11:05:14 +11:00
2017-02-24 17:46:57 -08:00
2017-02-02 22:05:28 -05:00
2017-01-14 11:31:50 +01:00
2017-01-04 13:22:38 -07:00
2017-02-07 10:51:46 -05:00
2016-12-06 11:05:46 +01:00
2017-04-05 18:26:50 +01:00
2017-05-03 15:52:11 -07:00
2017-02-03 14:13:19 -08:00
2017-02-24 17:46:56 -08:00
2016-12-12 18:55:07 -08:00
2017-01-24 12:23:35 -05:00
2017-01-27 11:10:50 -05:00
2017-05-03 15:52:10 -07:00
2017-02-23 09:54:19 -08:00
2017-02-24 17:46:54 -08:00
2017-03-03 01:45:25 +01:00
2017-03-13 14:59:22 +01:00
2017-05-08 17:15:13 -07:00
2017-04-13 18:24:21 -07:00
2017-05-08 17:15:10 -07:00
2017-04-11 14:18:35 -05:00
2017-05-03 19:12:27 -07:00
2017-04-04 16:54:21 +01:00
2017-02-02 04:36:12 +13:00
2017-04-24 14:30:46 -04:00
2017-01-18 15:43:59 -05:00
2017-01-12 16:48:26 -05:00
2017-02-23 11:53:22 -08:00
2017-02-20 13:23:30 -08:00
2017-04-21 14:05:36 -04:00
2017-05-10 21:46:22 -07:00
2017-04-17 13:01:48 -04:00
2017-04-14 10:05:36 +02:00
2017-05-11 21:30:57 -04:00
2016-12-06 21:48:21 +01:00
2016-12-06 21:42:16 +01:00
2017-05-03 09:51:24 -04:00
2017-01-24 12:50:47 -05:00
2017-05-10 13:03:38 -07:00
2017-04-26 13:03:04 -04:00
2017-04-21 10:45:01 -04:00
2017-05-08 19:01:06 -04:00
2017-03-03 01:43:38 +01:00
2016-12-24 11:23:24 -08:00
2017-05-20 10:11:34 -06:00
2017-04-04 09:48:23 -06:00
2017-02-22 13:34:00 -07:00
2017-04-21 16:41:47 +02:00
2017-05-09 15:15:47 -07:00
2017-05-09 22:55:58 +10:00
2017-04-07 12:23:29 +02:00
2017-02-15 08:53:32 -06:00
2017-02-10 14:54:37 +01:00
2017-05-11 10:26:22 -05:00
2017-03-24 12:51:04 -07:00
2017-03-14 15:10:11 -05:00
2017-05-22 18:01:46 +02:00
2017-05-05 11:36:44 -07:00
2017-02-28 09:08:33 -08:00
2017-03-02 08:42:29 +01:00
2016-12-29 11:03:15 -08:00
2017-05-08 17:15:10 -07:00
2017-03-28 08:23:27 +02:00
2017-02-03 16:35:42 -05:00
2016-12-06 10:17:03 +02:00
2017-04-28 10:23:19 -05:00
2016-12-06 13:45:48 -06:00
2017-04-18 14:21:04 -05:00
2017-04-11 14:18:36 -05:00
2017-04-11 14:18:37 -05:00
2017-04-11 14:18:37 -05:00
2017-05-26 10:51:18 -07:00
2017-04-04 17:49:49 +01:00
2017-03-22 19:18:43 -07:00
2017-01-14 11:14:35 +01:00
2017-03-16 09:57:08 +01:00
2017-03-30 09:55:35 +02:00
2017-03-02 08:42:36 +01:00
2017-02-24 17:46:54 -08:00
2017-01-25 14:40:19 -05:00
2017-04-26 22:39:08 -04:00
2017-02-24 17:46:56 -08:00
2017-03-02 08:42:38 +01:00
2017-05-09 10:01:15 -07:00
2017-02-09 22:52:17 +01:00
2017-03-03 00:43:11 +01:00
2016-12-13 11:42:18 -08:00
2017-05-05 22:54:28 +02:00
2017-02-06 11:25:55 -07:00
2017-04-25 13:20:46 -07:00
2017-01-14 11:14:53 +01:00
2017-04-17 12:52:22 -04:00
2017-04-14 21:49:54 +02:00
2017-04-14 21:49:56 +02:00
2017-03-03 01:43:47 +01:00
2016-12-27 12:30:56 +01:00
2017-05-08 17:15:11 -07:00
2016-12-13 16:07:55 -08:00
2017-05-08 17:15:12 -07:00
2017-06-28 22:49:11 +10:00
2017-03-29 00:00:29 +02:00
2017-03-07 14:01:02 -08:00
2016-12-12 19:56:15 -08:00
2017-05-09 16:43:23 +03:00
2017-05-23 07:40:44 -05:00
2017-03-10 20:55:09 +01:00
2017-01-30 09:36:42 +01:00
2017-01-04 18:36:41 +00:00
2017-03-28 16:03:21 -05:00
2016-12-19 08:23:53 -08:00
2017-04-19 14:21:23 +02:00
2017-02-13 21:44:09 -05:00
2017-01-27 14:25:06 -05:00
2017-03-28 08:54:48 +02:00
2016-12-20 09:48:47 -08:00
2017-02-24 17:46:57 -08:00
2017-04-18 11:38:20 -07:00
2017-05-02 06:29:22 -07:00
2017-03-09 13:27:17 -08:00
2017-04-19 09:29:18 -07:00
2017-03-02 08:42:24 +01:00
2017-05-10 10:30:46 -07:00
2017-04-21 05:59:27 -07:00
2017-04-21 05:59:27 -07:00
2017-02-01 09:17:51 +01:00
2017-03-13 07:41:08 +01:00
2017-02-03 12:34:59 +01:00
2017-01-30 14:18:54 -08:00
2017-02-26 22:43:44 +01:00
2017-04-04 17:36:10 +02:00
2017-05-01 16:22:40 -04:00
2017-05-01 10:26:40 -04:00
2017-05-03 15:52:10 -07:00
2016-12-12 11:26:47 -08:00
2017-05-03 15:52:09 -07:00
2017-01-18 10:43:15 -08:00
2017-04-09 14:45:21 -07:00
2017-04-14 14:06:52 -06:00
2017-05-05 18:16:23 -07:00
2017-02-19 18:17:59 -05:00
2017-03-28 11:05:14 +11:00
2017-02-23 11:55:41 -07:00
2017-05-08 17:15:12 -07:00
2017-05-18 17:38:24 +02:00
2017-04-08 18:51:57 +02:00
2017-01-19 14:17:05 +01:00
2017-03-25 10:37:26 -07:00
2017-02-24 17:46:56 -08:00
2017-03-03 01:43:48 +01:00
2017-04-17 21:53:19 -05:00
2017-03-02 08:42:29 +01:00
2017-01-09 13:58:57 -05:00
2017-05-02 16:40:27 -07:00
2017-04-18 11:42:36 -07:00
2017-02-22 16:41:27 -08:00
2017-03-26 15:09:45 +02:00
2017-03-23 17:01:02 -07:00
2017-01-09 16:07:38 -05:00
2017-01-12 09:33:39 +01:00
2017-01-12 09:33:39 +01:00
2017-01-12 09:33:39 +01:00
2016-12-26 23:53:46 -05:00
2017-01-25 11:48:03 +01:00
2017-04-18 11:38:23 -07:00
2017-04-26 11:23:28 -07:00
2017-04-26 11:23:28 -07:00
2017-04-26 16:32:17 -07:00
2017-03-08 09:18:02 +01:00
2017-04-03 01:06:00 -04:00
2017-03-22 12:15:15 -07:00
2017-05-05 18:49:20 -07:00
2017-05-05 22:54:28 +02:00
2017-02-22 16:41:30 -08:00
2017-05-03 15:52:11 -07:00
2017-01-06 13:00:01 -05:00
2017-03-02 20:51:15 -05:00
2017-04-16 23:42:49 -05:00
2017-03-24 20:34:39 -06:00
2017-03-02 08:42:29 +01:00
2017-04-26 14:44:39 -04:00
2017-03-09 15:42:33 +01:00
2017-01-04 12:47:28 +08:00
2017-05-02 10:45:15 -07:00
2017-03-23 02:12:14 +01:00
2017-05-08 17:15:15 -07:00
2016-12-25 11:04:12 +01:00
2016-12-25 11:04:12 +01:00
2017-04-14 21:49:55 +02:00
2017-03-03 01:45:39 +01:00
2017-01-10 18:31:55 -08:00
2017-04-03 22:46:02 +03:00
2017-03-24 20:51:50 -04:00
2016-12-09 09:13:30 -05:00
2017-04-10 15:22:17 -04:00
2017-05-18 17:38:24 +02:00
2017-04-19 09:29:17 -07:00
2017-05-08 17:15:14 -07:00
2017-04-01 20:11:36 -07:00
2017-04-08 18:13:27 +02:00
2017-04-02 12:10:47 -04:00
2016-12-11 18:01:51 -08:00
2017-04-18 16:54:19 +02:00
2017-03-06 15:26:37 -06:00
2017-03-09 17:01:10 -08:00
2017-02-10 16:34:17 +00:00
2016-12-01 10:40:05 -07:00
2017-05-02 23:41:43 +03:00
2017-01-20 11:01:17 -05:00
2017-05-02 23:41:43 +03:00
2017-04-24 12:35:56 -04:00
2017-05-09 16:43:22 +03:00
2017-05-03 15:52:08 -07:00
2017-03-02 08:42:25 +01:00
2017-05-12 15:57:15 -07:00
2017-03-17 15:10:49 +09:00
2017-02-03 11:49:06 +01:00
2017-01-14 09:54:13 +01:00
2017-03-08 10:36:03 -08:00
2017-02-24 14:00:23 -08:00
2017-04-15 12:20:53 +02:00
2017-03-22 20:11:33 -06:00
2017-01-14 12:11:59 +01:00
fd851a3cdc