Reset swappiness
Revert UKSM incorrectly applied
UKSM 0.1.2.2
mutex: Make more scalable by doing less atomic operations

Date	Thu, 4 Apr 2013 10:54:16 -0400

In the __mutex_lock_common() function, an initial entry into
the lock slow path will cause two atomic_xchg instructions to be
issued. Together with the atomic decrement in the fast path, a total
of three atomic read-modify-write instructions will be issued in
rapid succession. This can cause a lot of cache bouncing when many
tasks are trying to acquire the mutex at the same time.

This patch will reduce the number of atomic_xchg instructions used by
checking the counter value first before issuing the instruction. The
atomic_read() function is just a simple memory read. The atomic_xchg()
function, on the other hand, can be up to 2 order of magnitude or even
more in cost when compared with atomic_read(). By using atomic_read()
to check the value first before calling atomic_xchg(), we can avoid a
lot of unnecessary cache coherency traffic. The only downside with this
change is that a task on the slow path will have a tiny bit
less chance of getting the mutex when competing with another task
in the fast path.

The same is true for the atomic_cmpxchg() function in the
mutex-spin-on-owner loop. So an atomic_read() is also performed before
calling atomic_cmpxchg().

The mutex locking and unlocking code for the x86 architecture can allow
any negative number to be used in the mutex count to indicate that some
tasks are waiting for the mutex. I am not so sure if that is the case
for the other architectures. So the default is to avoid atomic_xchg()
if the count has already been set to -1. For x86, the check is modified
to include all negative numbers to cover a larger case.

The following table shows the scalability data on an 8-node 80-core
Westmere box with a 3.7.10 kernel. The numactl command is used to
restrict the running of the high_systime workloads to 1/2/4/8 nodes
with hyperthreading on and off.

+-----------------+------------------+------------------+----------+
|  Configuration  | Mean Transaction | Mean Transaction | % Change |
|		  |  Rate w/o patch  | Rate with patch  |	   |
+-----------------+------------------------------------------------+
|		  |              User Range 1100 - 2000		   |
+-----------------+------------------------------------------------+
| 8 nodes, HT on  |      36980       |      148590      | +301.8%  |
| 8 nodes, HT off |      42799       |      145011      | +238.8%  |
| 4 nodes, HT on  |	 61318       |      118445      |  +51.1%  |
| 4 nodes, HT off |     158481       |      158592      |   +0.1%  |
| 2 nodes, HT on  |     180602       |      173967      |   -3.7%  |
| 2 nodes, HT off |     198409       |      198073      |   -0.2%  |
| 1 node , HT on  |     149042       |      147671      |   -0.9%  |
| 1 node , HT off |     126036       |      126533      |   +0.4%  |
+-----------------+------------------------------------------------+
|		  |              User Range 200 - 1000		   |
+-----------------+------------------------------------------------+
| 8 nodes, HT on  |      41525       |      122349      | +194.6%  |
| 8 nodes, HT off |      49866       |      124032      | +148.7%  |
| 4 nodes, HT on  |	 66409       |      106984      |  +61.1%  |
| 4 nodes, HT off |     119880       |      130508      |   +8.9%  |
| 2 nodes, HT on  |     138003       |      133948      |   -2.9%  |
| 2 nodes, HT off |     132792       |      131997      |   -0.6%  |
| 1 node , HT on  |     116593       |      115859      |   -0.6%  |
| 1 node , HT off |     104499       |      104597      |   +0.1%  |
+-----------------+------------------+------------------+----------+
AIM7 benchmark run has a pretty large run-to-run variance due to random
nature of the subtests executed. So a difference of less than +-5%
may not be really significant.

This patch improves high_systime workload performance at 4 nodes
and up by maintaining transaction rates without significant drop-off
at high node count.  The patch has practically no impact on 1 and 2
nodes system.

The table below shows the percentage time (as reported by perf
record -a -s -g) spent on the __mutex_lock_slowpath() function by
the high_systime workload at 1500 users for 2/4/8-node configurations
with hyperthreading off.

+---------------+-----------------+------------------+---------+
| Configuration | %Time w/o patch | %Time with patch | %Change |
+---------------+-----------------+------------------+---------+
|    8 nodes    |      65.34%     |      0.69%       |  -99%   |
|    4 nodes    |       8.70%	  |      1.02%	     |  -88%   |
|    2 nodes    |       0.41%     |      0.32%       |  -22%   |
+---------------+-----------------+------------------+---------+
It is obvious that the dramatic performance improvement at 8
nodes was due to the drastic cut in the time spent within the
__mutex_lock_slowpath() function.

The table below show the improvements in other AIM7 workloads (at 8
nodes, hyperthreading off).

+--------------+---------------+----------------+-----------------+
|   Workload   | mean % change | mean % change  | mean % change   |
|              | 10-100 users  | 200-1000 users | 1100-2000 users |
+--------------+---------------+----------------+-----------------+
| alltests     |     +0.6%     |   +104.2%      |   +185.9%       |
| five_sec     |     +1.9%     |     +0.9%      |     +0.9%       |
| fserver      |     +1.4%     |     -7.7%      |     +5.1%       |
| new_fserver  |     -0.5%     |     +3.2%      |     +3.1%       |
| shared       |    +13.1%     |   +146.1%      |   +181.5%       |
| short        |     +7.4%     |     +5.0%      |     +4.2%       |
+--------------+---------------+----------------+-----------------+
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
mutex: restrict mutex spinning to only one task per mutex

Date	Thu, 4 Apr 2013 10:54:17 -0400

The current mutex spinning code allow multiple tasks to spin on a
single mutex concurrently. There are two major problems with this
approach:

 1. This is not very energy efficient as the spinning tasks are not
    doing useful work. The spinning tasks may also block other more
    important or useful tasks from running as preemption is disabled.
    Only one of the spinners will get the mutex at any time. The
    other spinners will have to wait for much longer to get it.

 2. The mutex data structure on x86-64 should be 32 bytes. The spinning
    code spin on lock->owner which, in most cases, should be in the same
    64-byte cache line as the lock->wait_lock spinlock. As a result,
    the mutex spinners are contending the same cacheline with other
    CPUs trying to get the spinlock leading to increased time spent
    on the spinlock as well as on the mutex spinning.

These problems are worse on system with large number of CPUs. One way
to reduce the effect of these two problems is to allow only one task
to be spinning on a mutex at any time.

This patch adds a new spinner field in the mutex.h to limit the
number of spinner to only one task. That will increase the size of
the mutex by 8 bytes in a 64-bit environment (4 bytes in a 32-bit
environment).

The AIM7 benchmarks were run on 3.7.10 derived kernels to show the
performance changes with this patch on a 8-socket 80-core system
with hyperthreading off.  The table below shows the mean % change
in performance over a range of users for some AIM7 workloads with
just the less atomic operation patch (patch 1) vs the less atomic
operation patch plus this one (patches 1+2).

+--------------+-----------------+-----------------+-----------------+
|   Workload   | mean % change   | mean % change   | mean % change   |
|              | 10-100 users    | 200-1000 users  | 1100-2000 users |
+--------------+-----------------+-----------------+-----------------+
| alltests     |     -0.2%       |     -3.8%       |    -4.2%        |
| five_sec     |     -0.6%       |     -2.0%       |    -2.4%        |
| fserver      |     +2.2%       |    +16.2%       |    +2.2%        |
| high_systime |     -0.3%       |     -4.3%       |    -3.0%        |
| new_fserver  |     +3.9%       |    +16.0%       |    +9.5%        |
| shared       |     -1.7%       |     -5.0%       |    -4.0%        |
| short        |     -7.7%       |     +0.2%       |    +1.3%        |
+--------------+-----------------+-----------------+-----------------+
It can be seen that this patch improves performance for the fserver and
new_fserver workloads while suffering some slight drop in performance
for the other workloads.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
mutex: dynamically disable mutex spinning at high load
Date	Thu, 4 Apr 2013 10:54:18 -0400

The Linux mutex code has a MUTEX_SPIN_ON_OWNER configuration
option that was enabled by default in major distributions like Red
Hat. Allowing threads waiting on mutex to spin while the mutex owner
is running will theoretically reduce latency on the acquisition of
mutex at the expense of energy efficiency as the spinning threads
are doing no useful work.

This is not a problem on a lightly loaded system where the CPU may
be idle anyway. On a highly loaded system, the spinning tasks may be
blocking other tasks from running even if they have higher priority
because the spinning was done with preemption disabled.

This patch will disable mutex spinning if the current load is high
enough. The load is considered high if there are 2 or more active tasks
waiting to run on the current CPU. If there is only one task waiting,
it will check the average load at the past minute (calc_load_tasks).
If it is more than double the number of active CPUs, the load is
considered high too.  This is a rather simple metric that does not
incur that much additional overhead.

The AIM7 benchmarks were run on 3.7.10 derived kernels to show the
performance changes with this patch on a 8-socket 80-core system
with hyperthreading off.  The table below shows the mean % change
in performance over a range of users for some AIM7 workloads with
just the less atomic operation patch (patch 1) vs the less atomic
operation patch plus this one (patches 1+3).

+--------------+-----------------+-----------------+-----------------+
|   Workload   | mean % change   | mean % change   | mean % change   |
|              | 10-100 users    | 200-1000 users  | 1100-2000 users |
+--------------+-----------------+-----------------+-----------------+
| alltests     |      0.0%       |     -0.1%       |    +5.0%        |
| five_sec     |     +1.5%       |     +1.3%       |    +1.3%        |
| fserver      |     +1.5%       |    +25.4%       |    +9.6%        |
| high_systime |     +0.1%       |      0.0%       |    +0.8%        |
| new_fserver  |     +0.2%       |    +11.9%       |   +14.1%        |
| shared       |     -1.2%       |     +0.3%       |    +1.8%        |
| short        |     +6.4%       |     +2.5%       |    +3.0%        |
+--------------+-----------------+-----------------+-----------------+
It can be seen that this patch provides some big performance
improvement for the fserver and new_fserver workloads while is still
generally positive for the other AIM7 workloads.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
modified for tuna kernel from LKML

Signed-off-by: Paul Reioux <reioux@gmail.com>
slub: fix a possible memory leak

Memory allocated by kstrdup should be freed,
when kmalloc(kmem_size, GFP_KERNEL) is failed.

Signed-off-by: Joonsoo Kim <js1304@gmail.com>
slub: remove unused argument of init_kmem_cache_node()

We don't use the argument since commit 3b89d7d881a1dbb4da158f7eb5d6b3ceefc72810
('slub: move min_partial to struct kmem_cache'), so remove it

Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Enable UKSM in captivate
Staging: zram: Remove useless offset calculation in handle_uncompressed_page()

The offset of uncompressed page is always zero: handle_uncompressed_page()
doesn't have to care about it.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
sw_sync: export sw_sync API

Needed to let modules link against sw_sync.

Change-Id: I71d3e52677ef21b6e1ecdb84f831491be1f4fbe6
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 8786b6f2b985dd3dcfbb3716b67c4453e79d74dc)
sync: reorder sync_fence_release

Previously fence's pts were freed before the were the fence was removed from the
global fence list.  This led to a race with the debugfs support where it would
iterate over sync_pts that had been freed.

Change-Id: Ia3ddbf77de42ca593fc2dc353b5d04e42ddf3946
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 4128cda08565638abecc8011329b008928a0e3c4)
sync: optimize fence merges

If the two fences being merged contain sync_pts from the same timeline,
those two pts will be collapsed into a single pt representing the latter
of the two.

Change-Id: Iced7ebb7e5a17a0c8b1a2969ba3388a4edb9ecaf
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit c588a0d05b516a8ee2c69d7d4209680fc948d395)
sync: add internal refcounting to fences

If a fence is released while a timeline that one of it's pts is on is being
signaled, it is possible for that fence to be deleted before it is signaled.
This patch adds a refcount for internal references such as signaled pt
processing.

Change-Id: Ie8605e6fd2ac026c207220a03d84e1c1078ec719
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 0e4f6675f8b443cf5d68d36a67f1c7ef4c04cef2)
sync: add reference counting to timelines

If a timeline is destroyed while fences still hold pts on it, the reworked
fence release handler can cause the timeline to be freed before all it's points
are freed.

Change-Id: I1cd8ddb638eded7db9db446ff6b37f3dd165d6c4
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 7d709710624275322b9411179ab45c5fd255cbd1)
sync: Fix error paths

Check the return value of get_unused_fd to make sure a valid
file descriptor is returned.

Make sure to call put_unused_fd even if an error occurs before
the fd can be used.

Change-Id: I0fe8f78d9e30ecfc4d271c5d875424543dae2d0f
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
(cherry picked from commit 3b5577e15de9521563715e4d26f99dfd19a56141)
sw_sync: Fix error paths

Check the return value of get_unused_fd to make sure a valid
file descriptor is returned.

Make sure to call put_unused_fd even if an error occurs before
the fd can be used.

Change-Id: Ibbf55caebc2f8ee6a03f298eb0ae0189c7d10b5c
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
(cherry picked from commit 5be5b6a568e5cf6dd13049e42a0b3b3a34d8f79d)
sync: change wait timeout to mirror poll semantics

Change-Id: Ib38e6d339d41885a33027752690d65a52b6897f6
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit cd2982e667f1799bcb00267b1f004dca821d2c68)
sync: fix erase-o in sync_fence_wait

Change-Id: I189707cf658a9f1f2943515c891b43961994e774
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 7020483263826ed2257a350c01fffa7514c0bf0b)
sync: clean up compiler warnings

Change-Id: I8a2ec5db652c61fd04571402067b37273b91e78f
Signed-off-by: Erik Gilling <konkers@android.com>
(cherry picked from commit 699d59e6719a890112a1fbbed69b16ddd4375712)