lib: Add lz4 compressor module

From	Chanho Min <>

This patch adds support for LZ4 compression in the Linux Kernel.
LZ4 Compression APIs for kernel are based on LZ4 implementation
by Yann Collet and changed with 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.

Signed-off-by: Chanho Min <chanho.min@lge.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
crypto: Add lz4 Cryptographic API

From	Chanho Min <>

This patch adds support for lz4 and lz4hc compression algorithm
using the lib/lz4/* codebase.
Signed-off-by: Chanho Min <chanho.min@lge.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
lib/lz4/lz4_compress: fix macro usage error

Signed-off-by: Paul Reioux <reioux@gmail.com>
LZ4: compression/decompression signedness mismatch (v2)

LZ4 compression and decompression functions require different
in signedness input/output parameters: unsigned char for
compression and signed char for decompression.

Change decompression API to require "(const) unsigned char *".

v2: minor coding style fix.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
UPDATE: zram_drv.c
staging: zram: add per-cpu support to Crypto

Date	Tue, 30 Jul 2013 14:30:49 +0200

Since original zram code did not implement any per-cpu operations,
my previous patch (staging: zram: add Crypto API support) did not
include them either.

This patch complements the first one with per-cpu support for Crypto,
allocating tfms buffer separately for each online processor.
Changes are based on zswap and zcache per-cpu code.

Basic tests (concurrent writing several 10-40MB chunks to zram) performed
on an ARM-based EXYNOS4412 Quad-Core showed that per-cpu code provides
noticeable time saving, ranging between 30-40% for LZO and LZ4 compressors.
Sample data (LZO): writing 160MB, 40MB per thread took 0.60s with per-cpu
code included and approximately 0.80s without per-cpu support.

Signed-off-by: Piotr Sarna <p.sarna@partner.samsung.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

backported to Linux 3.4 by faux123
Signed-off-by: Paul Reioux <reioux@gmail.com>
zram_drv: switch default compressor to new lz4

Signed-off-by: Paul Reioux <reioux@gmail.com>
zcache-main.c: use MACRO define instead of hardcoded default of lzo

Signed-off-by: Paul Reioux <reioux@gmail.com>
zcache-main: switch to lz4 as default

Signed-off-by: Paul Reioux <reioux@gmail.com>
drivers/input/evbug.c: silence annoying dmesg log spam

Signed-off-by: Paul Reioux <reioux@gmail.com>
drivers/misc/pm8xxx-vibrator-pwm.c: disable meaningless dmesg log spam
AIO: Don't plug the I/O queue in do_io_submit()

Asynchronous I/O latency to a solid-state disk greatly increased between the
2.6.32 and 3.0 kernels. By removing the plug from do_io_submit(), we observed
a 34% improvement in the I/O latency.

Unfortunately, at this level, we don't know if the request is to
a rotating disk or not.

Change-Id: I7101df956473ed9fd5dcff18e473dd93b688a5c1
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: linux-aio@kvack.org
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jeff Moyer <jmoyer@redhat.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched/rt: Remove redundant nr_cpus_allowed test

Date    Fri, 4 Oct 2013 14:24:53 -0500

From: Shawn Bohrer <sbohrer@rgmadvisors.com>

In 76854c7e8f3f4172fef091e78d88b3b751463ac6 "sched: Use
rt.nr_cpus_allowed to recover select_task_rq() cycles" an optimization
was added to select_task_rq_rt() that immediately returns when
p->nr_cpus_allowed == 1 at the beginning of the function.  This makes
the latter p->nr_cpus_allowed > 1 check redundant and can be removed.
Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com>

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

Signed-off-by: Paul Reioux <reioux@gmail.com>
SELinux: include definition of new capabilities

The kernel has added CAP_WAKE_ALARM and CAP_EPOLLWAKEUP.  We need to
define these in SELinux so they can be mediated by policy.

Change-Id: I8a3e0db15ec5f4eb05d455a57e8446a8c2b484c2
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
[sds: rename epollwakeup to block_suspend to match upstream merge]
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
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>
softirq: reduce latencies

Date    Thu, 03 Jan 2013 23:49:40 -0800

In various network workloads, __do_softirq() latencies can be up
to 20 ms if HZ=1000, and 200 ms if HZ=100.

This is because we iterate 10 times in the softirq dispatcher,
and some actions can consume a lot of cycles.

This patch changes the fallback to ksoftirqd condition to :

- A time limit of 2 ms.
- need_resched() being set on current task

When one of this condition is met, we wakeup ksoftirqd for further
softirq processing if we still have pending softirqs.

Using need_resched() as the only condition can trigger RCU stalls,
as we can keep BH disabled for too long.

I ran several benchmarks and got no significant difference in
throughput, but a very significant reduction of latencies (one order
of magnitude) :

In following bench, 200 antagonist "netperf -t TCP_RR" are started in
background, using all available cpus.

Then we start one "netperf -t TCP_RR", bound to the cpu handling the NIC
IRQ (hard+soft)

Before patch :

RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
RT_LATENCY=550110.424
MIN_LATENCY=146858
MAX_LATENCY=997109
P50_LATENCY=305000
P90_LATENCY=550000
P99_LATENCY=710000
MEAN_LATENCY=376989.12
STDDEV_LATENCY=184046.92
After patch :

RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
RT_LATENCY=40545.492
MIN_LATENCY=9834
MAX_LATENCY=78366
P50_LATENCY=33583
P90_LATENCY=59000
P99_LATENCY=69000
MEAN_LATENCY=38364.67
STDDEV_LATENCY=12865.26

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Miller <davem@davemloft.net>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
workqueue: remove HTC's incompatible workqueue debug

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