sched_features disable GENTLE_FAIR_SLEEPERS
backport: smp: patches from mainline 3.5 to hopefully help with hotplug
Thomas Gleixner's generic-idle patches:

smp: Add task_struct argument to __cpu_up()
Preparatory patch to make the idle thread allocation for secondary
cpus generic.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=8239c25f47d2b318156993b15f33900a86ea5e17

smp: Add generic smpboot facility
Start a new file, which will hold SMP and CPU hotplug related generic
infrastructure.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=38498a67aa2cf8c80754b8d304bfacc10bc582b5

smp: Provide generic idle thread allocation
All SMP architectures have magic to fork the idle task and to store it
for reusage when cpu hotplug is enabled. Provide a generic
infrastructure for it.
Create/reinit the idle thread for the cpu which is brought up in the
generic code and hand the thread pointer to the architecture code via
__cpu_up().
Note, that fork_idle() is called via a workqueue, because this
guarantees that the idle thread does not get a reference to a user
space VM. This can happen when the boot process did not bring up all
possible cpus and a later cpu_up() is initiated via the sysfs
interface. In that case fork_idle() would be called in the context of
the user space task and take a reference on the user space VM.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=29d5e0476e1c4a513859e7858845ad172f560389

arm: Use generic idle thread allocation
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=84ec6d5796e095e2f8698bd2b5d33849ed26d9e2

ported from this commit:
https://github.com/motley-git/kernel-Nexus4/commit/792a9656ceb8212b7cc2efc5091f3bb39cc1aafd#diff-7

Conflicts:
	arch/Kconfig
	arch/arm/Kconfig
SAMSUNG OSRC exFAT File System support v1.2.4

-  Make exFAT integrated in kernel by default

Conflicts:
	arch/arm/configs/tuna-tw_defconfig
	arch/arm/configs/tuna_defconfig
Updated SAMSUNG OSRC exFAT File System support - v1.2.5
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>
ARM: SMP: use a timing out completion for cpu hotplug
    ARM: SMP: use a timing out completion for cpu hotplug

    Rather than open-coding the jiffy-based wait, and polling for the
    secondary CPU to come online, use a completion instead.  This
    removes the need to poll, instead we will be notified when the
    secondary CPU has initialized.

Change-Id: If0cb7c0905fbc22d1b552bc3da05f54f50c5c301
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
cfg80211: Fix memory leak

When a driver requests a specific regulatory domain after cfg80211 already
has one, a struct ieee80211_regdomain is leaked.

Change-Id: Id28fc9861b9c911a97bd242439eabca097d76258
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Git-commit: b7566fc363e23f0efd3fa1e1460f9421cdc0d77e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[mattw@codeaurora.org: trivially backport to the msm-3.4 kernel]
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
ARM: L1 cache optimization
mmc: disable crc for better performance
ARM: Add optimised swahb32() byteswap helper
scheduler: compute time-average nr_running per run-queue

Compute the time-average number of running tasks per run-queue for a
trailing window of a fixed time period. The detla add/sub to the
average value is weighted by the amount of time per nr_running value
relative to the total measurement period.

Change-Id: I4b1fa8fee82a549889560ceded4b94bdb811671d
Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com>
Reviewed-on: http://git-master/r/108070
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Ryan Wong <ryanw@nvidia.com>
Tested-by: Ryan Wong <ryanw@nvidia.com>
writeback: fix occasional slow sync(1)
In case when system contains no dirty pages, wakeup_flusher_threads() will
submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits
immediately without doing anything, even though there are dirty inodes in
the system.  Thus sync(1) will write all the dirty inodes from a
WB_SYNC_ALL writeback pass which is slow.

Fix the problem by using get_nr_dirty_pages() in wakeup_flusher_threads()
instead of calculating number of dirty pages manually.  That function also
takes number of dirty inodes into account.

Change-Id: Ic90f80a31bb866b7628143b8b013871f83d05c13
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Paul Taysom <taysom@chromium.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 readahead: Optimize divide/multiply by power of 2 using L/R shift - Thanks Ramgear
---anarkia1976
locking, rwsem: Annotate inner lock as raw

There is no reason to allow the lock protecting rwsems (the
ownerless variant) to be preemptible on -rt. Convert it to raw.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
rwsem-spinlock: Implement writer lock-stealing for better scalability

We (Linux Kernel Performance project) found a regression
introduced by commit:

  5a505085f043 mm/rmap: Convert the struct anon_vma::mutex to an rwsem

which converted all anon_vma::mutex locks rwsem write locks.

The semantics are the same, but the behavioral difference is
quite huge in some cases. After investigating it we found the
root cause: mutexes support lock stealing while rwsems don't.

Here is the link for the detailed regression report:

  https://lkml.org/lkml/2013/1/29/84

Ingo suggested adding write lock stealing to rwsems:

    "I think we should allow lock-steal between rwsem writers - that
     will not hurt fairness as most rwsem fairness concerns relate to
     reader vs. writer fairness"

And here is the rwsem-spinlock version.

With this patch, we got a double performance increase in one
test box with following aim7 workfile:

    FILESIZE: 1M
    POOLSIZE: 10M
    10 fork_test

 /usr/bin/time output w/o patch                       /usr/bin/time_output with patch
 -- Percent of CPU this job got: 369%                 Percent of CPU this job got: 537%
 Voluntary context switches: 640595016                Voluntary context switches: 157915561

We got a 45% increase in CPU usage and saved about 3/4 voluntary context switches.

Reported-by: LKP project <lkp@linux.intel.com>
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Alex Shi <alex.shi@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: paul.gortmaker@windriver.com
Link: http://lkml.kernel.org/r/1359716356-23865-1-git-send-email-yuanhan.liu@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Revert "lib/rwsem.c: steal writing sem for better performance fixed for 3.0.y"

This reverts commit 8331f7086aa9cbfd71ac3fbaf68baa10721fc8dd.
rwsem: Implement writer lock-stealing for better scalability

Commit 5a505085f043 ("mm/rmap: Convert the struct anon_vma::mutex
to an rwsem") changed struct anon_vma::mutex to an rwsem, which
caused aim7 fork_test performance to drop by 50%.

Yuanhan Liu did the following excellent analysis:

    https://lkml.org/lkml/2013/1/29/84

and found that the regression is caused by strict, serialized,
FIFO sequential write-ownership of rwsems. Ingo suggested
implementing opportunistic lock-stealing for the front writer
task in the waitqueue.

Yuanhan Liu implemented lock-stealing for spinlock-rwsems,
which indeed recovered much of the regression - confirming
the analysis that the main factor in the regression was the
FIFO writer-fairness of rwsems.

In this patch we allow lock-stealing to happen when the first
waiter is also writer. With that change in place the
aim7 fork_test performance is fully recovered on my
Intel NHM EP, NHM EX, SNB EP 2S and 4S test-machines.

Reported-by: lkp@linux.intel.com
Reported-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Alex Shi <alex.shi@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: paul.gortmaker@windriver.com
Link: https://lkml.org/lkml/2013/1/29/84
Link: http://lkml.kernel.org/r/1360069915-31619-1-git-send-email-alex.shi@intel.com
[ Small stylistic fixes, updated changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
rwsem: make the waiter type an enumeration rather than a bitmask

We are not planning to add some new waiter flags, so we can convert the
waiter type into an enumeration.

Background: David Howells suggested I do this back when I tried adding
a new waiter type for unfair readers. However, I believe the cleanup
applies regardless of that use case.

Signed-off-by: Michel Lespinasse <walken@google.com>
rwsem: shorter spinlocked section in rwsem_down_failed_common()

This change reduces the size of the spinlocked and TASK_UNINTERRUPTIBLE
sections in rwsem_down_failed_common():

- We only need the sem->wait_lock to insert ourselves on the wait_list;
  the waiter node can be prepared outside of the wait_lock.

- The task state only needs to be set to TASK_UNINTERRUPTIBLE immediately
  before checking if we actually need to sleep; it doesn't need to protect
  the entire function.

Signed-off-by: Michel Lespinasse <walken@google.com>