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.

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>
jiffies conversions: Use compile time constants when possible

Date	Fri, 04 Jan 2013 13:15:43 -0800

Do the multiplications and divisions at compile time
instead of runtime when the converted value is a constant.

Make the calculation functions static __always_inline to jiffies.h.

Add #defines with __builtin_constant_p to test and use the
static inline or the runtime functions as appropriate.

Prefix the old exported symbols/functions with __

Signed-off-by: Paul Reioux <reioux@gmail.com>
drivers/exfat: add Samsung's open source exFat module version 1.2.4

Signed-off-by: Paul Reioux <reioux@gmail.com>
drivers/Makefile: add exFat support

Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:
	drivers/Makefile

Change-Id: Id42ab7ef3a3294c519f4b7284651bb5bed2ead8a
CHROMIUM: mm: Fix calculation of dirtyable memory

The system uses global_dirtyable_memory() to calculate
number of dirtyable pages/pages that can be allocated
to the page cache.  A bug causes an underflow thus making
the page count look like a big unsigned number.  This in turn
confuses the dirty writeback throttling to aggressively write
back pages as they become dirty (usually 1 page at a time).

Fix is to ensure there is no underflow while doing the math.

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Puneet Kumar <puneetster@chromium.org>

BUG=chrome-os-partner:16011
TEST=Manual; boot kernel, powerwash, login with testaccount and
make sure no jank occurs on sync of applications

Change-Id: I614e7c3156e014f0f28a4ef9bdd8cb8a2cd07b2a
Reviewed-on: https://gerrit.chromium.org/gerrit/37612
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Commit-Ready: Puneet Kumar <puneetster@chromium.org>
Reviewed-by: Puneet Kumar <puneetster@chromium.org>
Tested-by: Puneet Kumar <puneetster@chromium.org>
sync: don't block the flusher thread waiting on IO

When sync does it's WB_SYNC_ALL writeback, it issues data Io and
then immediately waits for IO completion. This is done in the
context of the flusher thread, and hence completely ties up the
flusher thread for the backing device until all the dirty inodes
have been synced. On filesystems that are dirtying inodes constantly
and quickly, this means the flusher thread can be tied up for
minutes per sync call and hence badly affect system level write IO
performance as the page cache cannot be cleaned quickly.

We already have a wait loop for IO completion for sync(2), so cut
this out of the flusher thread and delegate it to wait_sb_inodes().
Hence we can do rapid IO submission, and then wait for it all to
complete.

Effect of sync on fsmark before the patch:

FSUse%        Count         Size    Files/sec     App Overhead
.....
     0       640000         4096      35154.6          1026984
     0       720000         4096      36740.3          1023844
     0       800000         4096      36184.6           916599
     0       880000         4096       1282.7          1054367
     0       960000         4096       3951.3           918773
     0      1040000         4096      40646.2           996448
     0      1120000         4096      43610.1           895647
     0      1200000         4096      40333.1           921048

And a single sync pass took:

  real    0m52.407s
  user    0m0.000s
  sys     0m0.090s

After the patch, there is no impact on fsmark results, and each
individual sync(2) operation run concurrently with the same fsmark
workload takes roughly 7s:

  real    0m6.930s
  user    0m0.000s
  sys     0m0.039s

IOWs, sync is 7-8x faster on a busy filesystem and does not have an
adverse impact on ongoing async data write operations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
sched: Implement smarter wake-affine logic

The wake-affine scheduler feature is currently always trying to pull
the wakee close to the waker. In theory this should be beneficial if
the waker's CPU caches hot data for the wakee, and it's also beneficial
in the extreme ping-pong high context switch rate case.

Testing shows it can benefit hackbench up to 15%.

However, the feature is somewhat blind, from which some workloads
such as pgbench suffer. It's also time-consuming algorithmically.

Testing shows it can damage pgbench up to 50% - far more than the
benefit it brings in the best case.

So wake-affine should be smarter and it should realize when to
stop its thankless effort at trying to find a suitable CPU to wake on.

This patch introduces 'wakee_flips', which will be increased each
time the task flips (switches) its wakee target.

So a high 'wakee_flips' value means the task has more than one
wakee, and the bigger the number, the higher the wakeup frequency.

Now when making the decision on whether to pull or not, pay attention to
the wakee with a high 'wakee_flips', pulling such a task may benefit
the wakee. Also imply that the waker will face cruel competition later,
it could be very cruel or very fast depends on the story behind
'wakee_flips', waker therefore suffers.

Furthermore, if waker also has a high 'wakee_flips', that implies that
multiple tasks rely on it, then waker's higher latency will damage all
of them, so pulling wakee seems to be a bad deal.

Thus, when 'waker->wakee_flips / wakee->wakee_flips' becomes
higher and higher, the cost of pulling seems to be worse and worse.

The patch therefore helps the wake-affine feature to stop its pulling
work when:

	wakee->wakee_flips > factor &&
	waker->wakee_flips > (factor * wakee->wakee_flips)
The 'factor' here is the number of CPUs in the current CPU's NUMA node,
so a bigger node will lead to more pulling since the trial becomes more
severe.

After applying the patch, pgbench shows up to 40% improvements and no regressions.

Tested with 12 cpu x86 server and tip 3.10.0-rc7.

The percentages in the final column highlight the areas with the biggest wins,
all other areas improved as well:

	pgbench		    base	smart

	| db_size | clients |  tps  |	|  tps  |
	+---------+---------+-------+   +-------+
	| 22 MB   |       1 | 10598 |   | 10796 |
	| 22 MB   |       2 | 21257 |   | 21336 |
	| 22 MB   |       4 | 41386 |   | 41622 |
	| 22 MB   |       8 | 51253 |   | 57932 |
	| 22 MB   |      12 | 48570 |   | 54000 |
	| 22 MB   |      16 | 46748 |   | 55982 | +19.75%
	| 22 MB   |      24 | 44346 |   | 55847 | +25.93%
	| 22 MB   |      32 | 43460 |   | 54614 | +25.66%
	| 7484 MB |       1 |  8951 |   |  9193 |
	| 7484 MB |       2 | 19233 |   | 19240 |
	| 7484 MB |       4 | 37239 |   | 37302 |
	| 7484 MB |       8 | 46087 |   | 50018 |
	| 7484 MB |      12 | 42054 |   | 48763 |
	| 7484 MB |      16 | 40765 |   | 51633 | +26.66%
	| 7484 MB |      24 | 37651 |   | 52377 | +39.11%
	| 7484 MB |      32 | 37056 |   | 51108 | +37.92%
	| 15 GB   |       1 |  8845 |   |  9104 |
	| 15 GB   |       2 | 19094 |   | 19162 |
	| 15 GB   |       4 | 36979 |   | 36983 |
	| 15 GB   |       8 | 46087 |   | 49977 |
	| 15 GB   |      12 | 41901 |   | 48591 |
	| 15 GB   |      16 | 40147 |   | 50651 | +26.16%
	| 15 GB   |      24 | 37250 |   | 52365 | +40.58%
	| 15 GB   |      32 | 36470 |   | 50015 | +37.14%
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51D50057.9000809@linux.vnet.ibm.com
[ Improved the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Paul Reioux <reioux@gmail.com>
msm: move printk out of spin lock low_water_lock

cpu3 stuck in printk more time in spin lock low_water_lock cause cpu0
get spin lock fail and system crashed.

CRs-Fixed: 521570
Change-Id: I75356a4b4171ae2888ce6cce792f569b5ca8cdcf
Signed-off-by: Tingting Yang <tingting@codeaurora.org>
sched: Micro-optimize the smart wake-affine logic

Smart wake-affine is using node-size as the factor currently, but the overhead
of the mask operation is high.

Thus, this patch introduce the 'sd_llc_size' percpu variable, which will record
the highest cache-share domain size, and make it to be the new factor, in order
to reduce the overhead and make it more reasonable.

Tested-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Link: http://lkml.kernel.org/r/51D5008E.6030102@linux.vnet.ibm.com
[ Tidied up the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Paul Reioux <reioux@gmail.com>
mm/slub: Use kmem_cache for the kmem_cache structure

Do not use kmalloc() but kmem_cache_alloc() for the allocation
of the kmem_cache structures in slub.

Reviewed-by: Glauber Costa <glommer@parallels.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
backported for Linux 3.4

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: Reduce overestimating rq->avg_idle

Date	Thu, 29 Aug 2013 13:05:34 -0700

When updating avg_idle, if the delta exceeds some max value, then avg_idle
gets set to the max, regardless of what the previous avg was. This can cause
avg_idle to often be overestimated.

This patch modifies the way we update avg_idle by always updating it with the
function call to update_avg() first. Then, if avg_idle exceeds the max, we set
it to the max.

Signed-off-by: Jason Low <jason.low2@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
hwrng: add randomness to system from rng sources

When bringing a new RNG source online, it seems like it would make sense
to use some of its bytes to make the system entropy pool more random,
as done with all sorts of other devices that contain per-device or
per-boot differences.

Signed-off-by: Kees Cook <keescook@chromium.org>

Signed-off-by: Paul Reioux <reioux@gmail.com>
fs/sync: Make sync() satisfy many requests with one invocation

Dave Jones reported RCU stalls, overly long hrtimer interrupts, and
amazingly long NMI handlers from a trinity-induced workload involving
lots of concurrent sync() calls (https://lkml.org/lkml/2013/7/23/369).
There are any number of things that one might do to make sync() behave
better under high levels of contention, but it is also the case that
multiple concurrent sync() system calls can be satisfied by a single
sys_sync() invocation.

Given that this situation is reminiscent of rcu_barrier(), this commit
applies the rcu_barrier() approach to sys_sync().  This approach uses
a global mutex and a sequence counter.  The mutex is held across the
sync() operation, which eliminates contention between concurrent sync()
operations.  The counter is incremented at the beginning and end of
each sync() operation, so that it is odd while a sync() operation is in
progress and even otherwise, just like sequence locks.

The code that used to be in sys_sync() is now in do_sync(), and sys_sync()
now handles the concurrency.  The sys_sync() function first takes a
snapshot of the counter, then acquires the mutex, and then takes another
snapshot of the counter.  If the values of the two snapshots indicate that
a full do_sync() executed during the mutex acquisition, the sys_sync()
function releases the mutex and returns ("Our work is done!").  Otherwise,
sys_sync() increments the counter, invokes do_sync(), and increments
the counter again.

This approach allows a single call to do_sync() to satisfy an arbitrarily
large number of sync() system calls, which should eliminate issues due
to large numbers of concurrent invocations of the sync() system call.

Changes since v1 (https://lkml.org/lkml/2013/7/24/683):

o	Add a pair of memory barriers to keep the increments from
	bleeding into the do_sync() code.  (The failure probability
	is insanely low, but when you have several hundred million
	devices running Linux, you can expect several hundred instances
	of one-in-a-million failures.)

o	Actually CC some people who have experience in this area.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Curt Wohlgemuth <curtw@google.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: linux-fsdevel@vger.kernel.org

Signed-off-by: Paul Reioux <reioux@gmail.com>
random: mix in architectural randomness in extract_buf()

Mix in any architectural randomness in extract_buf() instead of
xfer_secondary_buf().  This allows us to mix in more architectural
randomness, and it also makes xfer_secondary_buf() faster, moving a
tiny bit of additional CPU overhead to process which is extracting the
randomness.

[ Commit description modified by tytso to remove an extended
  advertisement for the RDRAND instruction. ]

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: DJ Johnston <dj.johnston@intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
dts: re-add GPU Overclocking up to 600MHz (steps: 200/320/450/487.5/533/600)

Change-Id: If6425a3997b300e70080801e67ddf33b333150d7
mmc: core: enable async suspend

Enables the asynchronous suspend of card and class device.
This would enable both these devices to suspend in separate
respective threads, thus allowing other devices to suspend
concurrently.

CRs-fixed: 634333
Change-Id: Ic73022ef777b4fae4b1065f92cfa19da51a99634
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:
	drivers/mmc/core/bus.c
mmc: sdhci-msm: enable async suspend

This is aimed to reduce the suspend time of sdhci-msm device.
The suspend of this device would be carried out in a separate
thread and other devices may suspend concurrently. This is
required since the mmc sub-system contributes to the major
chunk of suspend latency.

CRs-fixed: 634333
Change-Id: I7bdead2deacd96aec5201d82b143b07c470b3892
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
USB: serial: enable async suspend for usb serial port device

Usb serial port device is child of its usb interface device, so
we can enable async suspend of usb serial port device to speedup
system suspend.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Conflicts:
	drivers/usb/serial/usb-serial.c

Change-Id: I987895586320405ab53b73bc3bad96f54b8bdc2f
TTY: msm_smd_tty: Fix simultaneous open/close race condition

smd_tty_close currently has a variable that depends on a race
condition with tty_port_open. This causes a null-pointer dereference
when the same port is simultaneously being opened/closed.

Use data from a static array instead of the variable to eliminate
the race condition.

CRs-Fixed: 624398
Change-Id: Ie55d37feaadd3a15f64e18501cd3af19145dbc8e
Signed-off-by: Steven Cahail <scahail@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
sched/fair: Optimize cgroup pick_next_task_fair()

Since commit 2f36825b1 ("sched: Next buddy hint on sleep and preempt
path") it is likely we pick a new task from the same cgroup, doing a put
and then set on all intermediate entities is a waste of time, so try to
avoid this.

Measured using:

  mount nodev /cgroup -t cgroup -o cpu
  cd /cgroup
  mkdir a; cd a
  mkdir b; cd b
  mkdir c; cd c
  echo $$ > tasks
  perf stat --repeat 10 -- taskset 1 perf bench sched pipe

PRE :      4.542422684 seconds time elapsed   ( +-  0.33% )
POST:      4.389409991 seconds time elapsed   ( +-  0.32% )

Which shows a significant improvement of ~3.5%

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>

Backported for Linux 3.4 kernel

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:
	kernel/sched/fair.c

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>