Add git-review

Change-Id: Ibba55a635b1bf0f1c246a6028540f97945560eaa
Some cleanup + add README

Change-Id: I6df2459be0b4a92eb61dbeae83135cafe8654f41
Liquify

Change-Id: Ib1d9c343bbfe8d91a73cbd6e1ec129ea58f996d7
ARM: Use -mcpu=cortex-a15 when targeting MSM Krait CPUs

Enable compiler optimizations specific to the Cortex-A15
processor when targeting MSM Krait CPUs. This is necessary
take advantage of the UDIV/SDIV instructions supported by
these processors. To accomplish this, we need to remove the
-march=armv7-a ISA restriction from the compiler options
because 'cortex-a15' is a superset of 'armv7-a'.

Change-Id: I6215aecc11fb4f77c971de7b84f68649ef234357
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
lib/string: use glibc version

the performance of memcpy and memmove of the general version is very
inefficient, this patch improved them.

Signed-off-by: Miao Xie <miaox*******>

Conflicts:

	lib/string.c
Signed-off-by: flar2 <asegaert@gmail.com>
lib/memcopy: use glibc version

the kernel's memcpy and memmove is very inefficient. But the glibc version is
quite fast, in some cases it is 10 times faster than the kernel version. So I
introduce some memory copy macros and functions of the glibc to improve the
kernel version's performance.

The strategy of the memory functions is:
1. Copy bytes until the destination pointer is aligned.
2. Copy words in unrolled loops.  If the source and destination are not
   aligned in the same way, use word memory operations, but shift and merge
   two read words before writing.
3. Copy the few remaining bytes.

Signed-off-by: Miao Xie <miaox*******>

Conflicts:

	lib/Makefile
Signed-off-by: flar2 <asegaert@gmail.com>
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>
Signed-off-by: flar2 <asegaert@gmail.com>
writeback: fix writeback cache thrashing

Consider Process A: huge I/O on sda
        doing heavy write operation - dirty memory becomes more
        than dirty_background_ratio
        on HDD - flusher thread flush-8:0

Consider Process B: small I/O on sdb
        doing while [1]; read 1024K + rewrite 1024K + sleep 2sec
        on Flash device - flusher thread flush-8:16

As Process A is a heavy dirtier, dirty memory becomes more
than dirty_background_thresh. Due to this, below check becomes
true(checking global_page_state in over_bground_thresh)
for all bdi devices(even for very small dirtied bdi - sdb):

In this case, even small cached data on 'sdb' is forced to flush
and writeback cache thrashing happens.

When we added debug prints inside above 'if' condition and ran
above Process A(heavy dirtier on bdi with flush-8:0) and
Process B(1024K frequent read/rewrite on bdi with flush-8:16)
we got below prints:

[Test setup: ARM dual core CPU, 512 MB RAM]

[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56064 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56704 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 84720 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 94720 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   384 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   960 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92160 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   256 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   768 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   256 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   320 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92032 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 91968 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =  1024 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   576 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 84352 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   512 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92608 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92544 KB

As mentioned in above log, when global dirty memory > global background_thresh
small cached data is also forced to flush by flush-8:16.
If removing global background_thresh checking code, we can reduce cache
thrashing of frequently used small data.
And It will be great if we can reserve a portion of writeback cache using
min_ratio.

After applying patch:
$ echo 5 > /sys/block/sdb/bdi/min_ratio
$ cat /sys/block/sdb/bdi/min_ratio
5
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56064 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56704 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  84160 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  96960 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  94080 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93120 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93120 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  91520 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  89600 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93696 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93696 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  72960 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90624 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90624 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90688 KB

As mentioned in the above logs, once cache is reserved for Process B,
and patch is applied there is less writeback cache thrashing on sdb
by frequent forced writeback by flush-8:16 in over_bground_thresh.

After all, small cached data will be flushed by periodic writeback
once every dirty_writeback_interval.

Suggested-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
Signed-off-by: flar2 <asegaert@gmail.com>
writeback: fix race that cause writeback hung

There is a race between mark inode dirty and writeback thread, see the
following scenario.  In this case, writeback thread will not run though
there is dirty_io.

__mark_inode_dirty()                                          bdi_writeback_workfn()
	...                                                       	...
	spin_lock(&inode->i_lock);
	...
	if (bdi_cap_writeback_dirty(bdi)) {
	    <<< assume wb has dirty_io, so wakeup_bdi is false.
	    <<< the following inode_dirty also have wakeup_bdi false.
	    if (!wb_has_dirty_io(&bdi->wb))
		    wakeup_bdi = true;
	}
	spin_unlock(&inode->i_lock);
	                                                            <<< assume last dirty_io is removed here.
	                                                            pages_written = wb_do_writeback(wb);
	                                                            ...
	                                                            <<< work_list empty and wb has no dirty_io,
	                                                            <<< delayed_work will not be queued.
	                                                            if (!list_empty(&bdi->work_list) ||
	                                                                (wb_has_dirty_io(wb) && dirty_writeback_interval))
	                                                                queue_delayed_work(bdi_wq, &wb->dwork,
	                                                                    msecs_to_jiffies(dirty_writeback_interval * 10));
	spin_lock(&bdi->wb.list_lock);
	inode->dirtied_when = jiffies;
	<<< new dirty_io is added.
	list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
	spin_unlock(&bdi->wb.list_lock);

	<<< though there is dirty_io, but wakeup_bdi is false,
	<<< so writeback thread will not be waked up and
	<<< the new dirty_io will not be flushed.
	if (wakeup_bdi)
	    bdi_wakeup_thread_delayed(bdi);

Writeback will run until there is a new flush work queued.  This may cause
a lot of dirty pages stay in memory for a long time.

Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.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. 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.

CC: stable@vger.kernel.org
Reported-by: Paul Taysom <taysom@chromium.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Cristoforo Cataldo <cristoforo.cataldo@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
AIO: Don't plug the I/O queue in do_io_submit()

Signed-off-by: flar2 <asegaert@gmail.com>
readahead: make context readahead more conservative

This helps performance on moderately dense random reads on SSD.

Transaction-Per-Second numbers provided by Taobao:

		QPS	case
		-------------------------------------------------------
		7536	disable context readahead totally
w/ patch:	7129	slower size rampup and start RA on the 3rd read
		6717	slower size rampup
w/o patch:	5581	unmodified context readahead

Before, readahead will be started whenever reading page N+1 when it happen
to read N recently.  After patch, we'll only start readahead when *three*
random reads happen to access pages N, N+1, N+2.  The probability of this
happening is extremely low for pure random reads, unless they are very
dense, which actually deserves some readahead.

Also start with a smaller readahead window.  The impact to interleaved
sequential reads should be small, because for a long run stream, the the
small readahead window rampup phase is negletable.

The context readahead actually benefits clustered random reads on HDD
whose seek cost is pretty high.  However as SSD is increasingly used for
random read workloads it's better for the context readahead to concentrate
on interleaved sequential reads.

Another SSD rand read test from Miao

        # file size:        2GB
        # read IO amount: 625MB
        sysbench --test=fileio          \
                --max-requests=10000    \
                --num-threads=1         \
                --file-num=1            \
                --file-block-size=64K   \
                --file-test-mode=rndrd  \
                --file-fsync-freq=0     \
                --file-fsync-end=off    run

shows the performance of btrfs grows up from 69MB/s to 121MB/s, ext4 from
104MB/s to 121MB/s.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Tested-by: Tao Ma <tm@tao.ma>
Tested-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: flar2 <asegaert@gmail.com>
block: Reserve only one queue tag for sync IO if only 3 tags are available

In case a device has three tags available we still reserve two of them
for sync IO. That leaves only a single tag for async IO such as
writeback from flusher thread which results in poor performance.

Allow async IO to consume two tags in case queue has three tag availabe
to get a decent async write performance.

This patch improves streaming write performance on a machine with such disk
from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of
streaming writer improves from 8 to 12 transactions per second so sync
IO doesn't seem to be harmed in presence of heavy async writer.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: flar2 <asegaert@gmail.com>
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: flar2 <asegaert@gmail.com>
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: flar2 <asegaert@gmail.com>
sched: reinitialize rq->next_balance when a CPU is hot-added

Reinitialize rq->next_balance when a CPU is hot-added.  Otherwise,
scheduler domain rebalancing may be skipped if rq->next_balance was
set to a future time when the CPU was last active, and the
newly-re-added CPU is in idle_balance().  As a result, the
newly-re-added CPU will remain idle with no tasks scheduled until the
softlockup watchdog runs - potentially 4 seconds later.  This can
waste energy and reduce performance.

This behavior can be observed in some SoC kernels, which use CPU
hotplug to dynamically remove and add CPUs in response to load.  In
one case that triggered this behavior,

0. the system started with all cores enabled, running multi-threaded
   CPU-bound code;

1. the system entered some single-threaded code;

2. a CPU went idle and was hot-removed;

3. the system started executing a multi-threaded CPU-bound task;

4. the CPU from event 2 was re-added, to respond to the load.

The time interval between events 2 and 4 was approximately 300
milliseconds.

Of course, ideally CPU hotplug would not be used in this manner,
but this patch does appear to fix a real bug.

Nvidia folks: this patch is submitted as at least a partial fix for
bug 1243368 ("[sched] Load-balancing not happening correctly after
cores brought online")

Change-Id: Iabac21e110402bb581b7db40c42babc951d378d0
Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Cc: Peter Boonstoppel <pboonstoppel@nvidia.com>
Reviewed-on: http://git-master/r/208927
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Peter Zu <pzu@nvidia.com>
Reviewed-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
GVS: Gerrit_Virtual_Submit
Tested-by: Peter Zu <pzu@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>
Signed-off-by: flar2 <asegaert@gmail.com>
mm: slub: Default slub_max_order to 0

To avoid locking and per-cpu overhead, SLUB optimisically uses
high-order allocations up to order-3 by default and falls back to
lower allocations if they fail. While care is taken that the caller
and kswapd take no unusual steps in response to this, there are
further consequences like shrinkers who have to free more objects to
release any memory. There is anecdotal evidence that significant time
is being spent looping in shrinkers with insufficient progress being
made (https://lkml.org/lkml/2011/4/28/361) and keeping kswapd awake.

SLUB is now the default allocator and some bug reports have been
pinned down to SLUB using high orders during operations like
copying large amounts of data. SLUBs use of high-orders benefits
applications that are sized to memory appropriately but this does not
necessarily apply to large file servers or desktops.  This patch
causes SLUB to use order-0 pages like SLAB does by default.
There is further evidence that this keeps kswapd's usage lower
(https://lkml.org/lkml/2011/5/10/383).

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: flar2 <asegaert@gmail.com>
decompressor: add LZ4 decompressor module

Add support for LZ4 decompression in the Linux Kernel.  LZ4 Decompression
APIs for kernel are based on LZ4 implementation by Yann Collet.

Benchmark Results(PATCH v3)
Compiler: Linaro ARM gcc 4.6.2

1. ARMv7, 1.5GHz based board
   Kernel: linux 3.4
   Uncompressed Kernel Size: 14MB
        Compressed Size  Decompression Speed
   LZO  6.7MB            20.1MB/s, 25.2MB/s(UA)
   LZ4  7.3MB            29.1MB/s, 45.6MB/s(UA)

2. ARMv7, 1.7GHz based board
   Kernel: linux 3.7
   Uncompressed Kernel Size: 14MB
        Compressed Size  Decompression Speed
   LZO  6.0MB            34.1MB/s, 52.2MB/s(UA)
   LZ4  6.5MB            86.7MB/s
- UA: Unaligned memory Access support
- Latest patch set for LZO applied

This patch set is for adding support for LZ4-compressed Kernel.  LZ4 is a
very fast lossless compression algorithm and it also features an extremely
fast decoder [1].

But we have five of decompressors already and one question which does
arise, however, is that of where do we stop adding new ones?  This issue
had been discussed and came to the conclusion [2].

Russell King said that we should have:

 - one decompressor which is the fastest
 - one decompressor for the highest compression ratio
 - one popular decompressor (eg conventional gzip)

If we have a replacement one for one of these, then it should do exactly
that: replace it.

The benchmark shows that an 8% increase in image size vs a 66% increase
in decompression speed compared to LZO(which has been known as the
fastest decompressor in the Kernel).  Therefore the "fast but may not be
small" compression title has clearly been taken by LZ4 [3].

[1] http://code.google.com/p/lz4/
[2] http://thread.gmane.org/gmane.linux.kbuild.devel/9157
[3] http://thread.gmane.org/gmane.linux.kbuild.devel/9347

LZ4 homepage: http://fastcompression.blogspot.com/p/lz4.html
LZ4 source repository: http://code.google.com/p/lz4/

Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com>
Signed-off-by: Yann Collet <yann.collet.73@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
lib: add support for LZ4-compressed kernel

Add support for extracting LZ4-compressed kernel images, as well as
LZ4-compressed ramdisk images in the kernel boot process.

Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Yann Collet <yann.collet.73@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
lib: add lz4 compressor module

This patchset is for supporting LZ4 compression and the crypto API using
it.

As shown below, the size of data is a little bit bigger but compressing
speed is faster under the enabled unaligned memory access.  We can use
lz4 de/compression through crypto API as well.  Also, It will be useful
for another potential user of lz4 compression.

lz4 Compression Benchmark:
Compiler: ARM gcc 4.6.4
ARMv7, 1 GHz based board
   Kernel: linux 3.4
   Uncompressed data Size: 101 MB
         Compressed Size  compression Speed
   LZO   72.1MB		  32.1MB/s, 33.0MB/s(UA)
   LZ4   75.1MB		  30.4MB/s, 35.9MB/s(UA)
   LZ4HC 59.8MB		   2.4MB/s,  2.5MB/s(UA)
- UA: Unaligned memory Access support
- Latest patch set for LZO applied

This patch:

Add support for LZ4 compression in the Linux Kernel.  LZ4 Compression APIs
for kernel are based on LZ4 implementation by Yann Collet and were changed
for kernel coding style.

LZ4 homepage : http://fastcompression.blogspot.com/p/lz4.html
LZ4 source repository : http://code.google.com/p/lz4/
svn revision : r90

Two APIs are added:

lz4_compress() support basic lz4 compression whereas lz4hc_compress()
support high compression or CPU performance get lower but compression
ratio get higher.  Also, we require the pre-allocated working memory with
the defined size and destination buffer must be allocated with the size of
lz4_compressbound.

[akpm@linux-foundation.org: make lz4_compresshcctx() static]
Signed-off-by: Chanho Min <chanho.min@lge.com>
Cc: "Darrick J. Wong" <djwong@us.ibm.com>
Cc: Bob Pearson <rpearson@systemfabricworks.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Herbert Xu <herbert@gondor.hengli.com.au>
Cc: Yann Collet <yann.collet.73@gmail.com>
Cc: Kyungsik Lee <kyungsik.lee@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>