[PATCH, v9] cgroups: introduce timer slack controller

Changelog:

v9:
 - update documentation
 - minor cleanup
v8:
 - change hiearchy rules
 - introduce timer_slack.effective_slack_ns
 - get_task_timer_slack() -> task_get_effective_timer_slack()
 - task_get_effective_timer_slack() splited in separate patch
 - implement PR_GET_EFFECTIVE_TIMERSLACK
v7:
 - totally reworked interface and rewritten from scratch
   (See Documentation/cgroups/timer_slack.txt for more information)
v6:
 - add documentation
 - use notifier_call_chain() instead of check hook
 - fix validate_change()
 - cleanup
v5:
 - -EBUSY on writing to timer_slack.min_slack_ns/max_slack_ns if a child has
   wider min-max range
v4:
 - hierarchy support
 - drop dummy_timer_slack_check()
 - workaround lockdep false (?) positive
 - allow 0 as timer slack value
v3:
 - rework interface
 - s/EXPORT_SYMBOL/EXPORT_SYMBOL_GPL/
v2:
 - fixed with CONFIG_CGROUP_TIMER_SLACK=y
v1:
 - initial revision

---

[PATCH, v9 1/3] hrtimer: introduce effective timer slack

task_get_effective_timer_slack() returns timer slack value to be used
to configure per-task timers. It can be equal or higher than task's
timer slack value.

For now task_get_effective_timer_slack() returns timer_slack_ns of the
task. Timer slack cgroup controller will implement a bit more
sophisticated logic.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

---

[PATCH, v9 2/3] hrtimer: implement PR_GET_EFFECTIVE_TIMERSLACK

PR_GET_EFFECTIVE_TIMERSLACK allows process to know its effective timer
slack value.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

---

[PATCH, v9 3/3] cgroups: introduce timer slack controller

Every task_struct has timer_slack_ns value. This value uses to round up
poll() and select() timeout values. This feature can be useful in
mobile environment where combined wakeups are desired.

Originally, prctl() was the only way to change timer slack value of
a process. So you was not able change timer slack value of another
process.

cgroup subsys "timer_slack" implements timer slack controller. It
provides a way to set minimal timer slack value for a group of tasks.
If a task belongs to a cgroup with minimal timer slack value higher than
task's value, cgroup's value will be applied.

Timer slack controller allows to implement setting timer slack value of
a process based on a policy. For example, you can create foreground and
background cgroups and move tasks between them based on system state.

Idea-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>

---

kernel/cgroup_timer_slack.c: fix compile error

kernel/cgroup_timer_slack.c:41: error: implicit declaration of
function 'ERR_PTR'

Signed-off-by: Boy Petersen <boypetersen@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>

Conflicts:
	include/linux/cgroup_subsys.h
ARM: support XZ compressed kernels

Wire up support for the XZ decompressor

Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
writeback: fix writeback cache thrashing

From: Namjae Jeon <namjae.jeon@samsung.com>

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>

The original code has been modified to compile on this Kernel version.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
writeback: increase bdi_min_ratio to 5 in light of the latest writeback commit.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
writeback: I believe these defines were calculated with HZ=1000 in mind. Since our devices are HZ=100 I hardcoded the values on this constants. I'm not 100% sure if this code was made for HZ with 1000 but I couldn't track it to understand clearly. Although I didn't see any drawback of using this as it is now. If anyone knows the answer please chime in.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
freezer: shorten freezer sleep time using exponential backoff

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
ARM: 7583/1: decompressor: Enable unaligned memory access for v6 and above

Modern GCC can generate code which makes use of the CPU's native
unaligned memory access capabilities.  This is useful for the C
decompressor implementations used for unpacking compressed kernels.

This patch disables alignment faults and enables the v6 unaligned
access model on CPUs which support these features (i.e., v6 and
later), allowing full unaligned access support for C code in the
decompressor.

The decompressor C code must not be built to assume that unaligned
access works if support for v5 or older platforms is included in
the kernel.

For correct code generation, C decompressor code must always use
the get_unaligned and put_unaligned accessors when dealing with
unaligned pointers, regardless of this patch.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Input: Send events one packet at a time

On heavy event loads, such as a multitouch driver, the irqsoff latency
can be as high as 250 us.  By accumulating a frame worth of data
before passing it on, the latency can be dramatically reduced.  As a
side effect, the special EV_SYN handling can be removed, since the
frame is now atomic.

This patch adds the events() handler callback and uses it if it
exists. The latency is improved by 50 us even without the callback.

Change-Id: Iebd9b1868ae6300a922a45b6d104e7c2b38e4cf5
Cc: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Tested-by: Ping Cheng <pingc@wacom.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

Input: Improve the events-per-packet estimate

The events-per-packet estimate has so far been used by MT devices
only. This patch adjusts the packet buffer size to also accomodate the
KEY and MSC events.  Keyboards normally send one or two keys at a
time. MT devices normally send a number of button keys along with the
MT information.  The buffer size chosen here covers those cases, and
matches the default buffer size in evdev. Since the input estimate is
now preferred, remove the special input-mt estimate.

Reviewed-and-tested-by: Ping Cheng <pingc@wacom.com>
Tested-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Fix section mismatches

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