Merge branch 'perf/urgent' into perf/core

Description:

		Control the power of camera module. 1 means on, 0 means off.

What:		/sys/devices/platform/ideapad/fan_mode

Date:		June 2012

KernelVersion:	3.6

Contact:	"Maxim Mikityanskiy <maxtram95@gmail.com>"

Description:

		Change fan mode

		There are four available modes:

			* 0 -> Super Silent Mode

			* 1 -> Standard Mode

			* 2 -> Dust Cleaning

			* 4 -> Efficient Thermal Dissipation Mode

<constant>V4L2_TUNER_CAP_NORM</constant> flags can't be used.</para>

<para>If multiple frequency bands are supported, then

<structfield>capability</structfield> is the union of all

<structfield>capability></structfield> fields of each &v4l2-frequency-band;.

<structfield>capability</structfield> fields of each &v4l2-frequency-band;.

</para></entry>

	  </row>

	  <row>

biodoc.txt

	- Notes on the Generic Block Layer Rewrite in Linux 2.5

capability.txt

	- Generic Block Device Capability (/sys/block/<disk>/capability)

	- Generic Block Device Capability (/sys/block/<device>/capability)

cfq-iosched.txt

	- CFQ IO scheduler tunables

data-integrity.txt

	- Block data integrity

deadline-iosched.txt

	- Deadline IO scheduler tunables

ioprio.txt

	- Block io priorities (in CFQ scheduler)

queue-sysfs.txt

	- Queue's sysfs entries

request.txt

	- The members of struct request (in include/linux/blkdev.h)

stat.txt

	- Block layer statistics in /sys/block/<dev>/stat

	- Block layer statistics in /sys/block/<device>/stat

switching-sched.txt

	- Switching I/O schedulers at runtime

writeback_cache_control.txt

CFQ (Complete Fairness Queueing)

===============================

The main aim of CFQ scheduler is to provide a fair allocation of the disk

I/O bandwidth for all the processes which requests an I/O operation.

CFQ maintains the per process queue for the processes which request I/O

operation(syncronous requests). In case of asynchronous requests, all the

requests from all the processes are batched together according to their

process's I/O priority.

CFQ ioscheduler tunables

========================

controller or for storage arrays), setting slice_idle=0 might end up in better

throughput and acceptable latencies.

back_seek_max

-------------

This specifies, given in Kbytes, the maximum "distance" for backward seeking.

The distance is the amount of space from the current head location to the

sectors that are backward in terms of distance.

This parameter allows the scheduler to anticipate requests in the "backward"

direction and consider them as being the "next" if they are within this

distance from the current head location.

back_seek_penalty

-----------------

This parameter is used to compute the cost of backward seeking. If the

backward distance of request is just 1/back_seek_penalty from a "front"

request, then the seeking cost of two requests is considered equivalent.

So scheduler will not bias toward one or the other request (otherwise scheduler

will bias toward front request). Default value of back_seek_penalty is 2.

fifo_expire_async

-----------------

This parameter is used to set the timeout of asynchronous requests. Default

value of this is 248ms.

fifo_expire_sync

----------------

This parameter is used to set the timeout of synchronous requests. Default

value of this is 124ms. In case to favor synchronous requests over asynchronous

one, this value should be decreased relative to fifo_expire_async.

slice_async

-----------

This parameter is same as of slice_sync but for asynchronous queue. The

default value is 40ms.

slice_async_rq

--------------

This parameter is used to limit the dispatching of asynchronous request to

device request queue in queue's slice time. The maximum number of request that

are allowed to be dispatched also depends upon the io priority. Default value

for this is 2.

slice_sync

----------

When a queue is selected for execution, the queues IO requests are only

executed for a certain amount of time(time_slice) before switching to another

queue. This parameter is used to calculate the time slice of synchronous

queue.

time_slice is computed using the below equation:-

time_slice = slice_sync + (slice_sync/5 * (4 - prio)). To increase the

time_slice of synchronous queue, increase the value of slice_sync. Default

value is 100ms.

quantum

-------

This specifies the number of request dispatched to the device queue. In a

queue's time slice, a request will not be dispatched if the number of request

in the device exceeds this parameter. This parameter is used for synchronous

request.

In case of storage with several disk, this setting can limit the parallel

processing of request. Therefore, increasing the value can imporve the

performace although this can cause the latency of some I/O to increase due

to more number of requests.

CFQ IOPS Mode for group scheduling

===================================

Basic CFQ design is to provide priority based time slices. Higher priority

Files denoted with a RO postfix are readonly and the RW postfix means

read-write.

add_random (RW)

----------------

This file allows to trun off the disk entropy contribution. Default

value of this file is '1'(on).

discard_granularity (RO)

-----------------------

This shows the size of internal allocation of the device in bytes, if

reported by the device. A value of '0' means device does not support

the discard functionality.

discard_max_bytes (RO)

----------------------

Devices that support discard functionality may have internal limits on

the number of bytes that can be trimmed or unmapped in a single operation.

The discard_max_bytes parameter is set by the device driver to the maximum

number of bytes that can be discarded in a single operation. Discard

requests issued to the device must not exceed this limit. A discard_max_bytes

value of 0 means that the device does not support discard functionality.

discard_zeroes_data (RO)

------------------------

When read, this file will show if the discarded block are zeroed by the

device or not. If its value is '1' the blocks are zeroed otherwise not.

hw_sector_size (RO)

-------------------

This is the hardware sector size of the device, in bytes.

iostats (RW)

-------------

This file is used to control (on/off) the iostats accounting of the

disk.

logical_block_size (RO)

-----------------------

This is the logcal block size of the device, in bytes.

max_hw_sectors_kb (RO)

----------------------

This is the maximum number of kilobytes supported in a single data transfer.

max_integrity_segments (RO)

---------------------------

When read, this file shows the max limit of integrity segments as

set by block layer which a hardware controller can handle.

max_sectors_kb (RW)

-------------------

This is the maximum number of kilobytes that the block layer will allow

for a filesystem request. Must be smaller than or equal to the maximum

size allowed by the hardware.

max_segments (RO)

-----------------

Maximum number of segments of the device.

max_segment_size (RO)

---------------------

Maximum segment size of the device.

minimum_io_size (RO)

--------------------

This is the smallest preferred io size reported by the device.

nomerges (RW)

-------------

This enables the user to disable the lookup logic involved with IO

each request queue may have upto N request pools, each independently

regulated by nr_requests.

optimal_io_size (RO)

--------------------

This is the optimal io size reported by the device.

physical_block_size (RO)

------------------------

This is the physical block size of device, in bytes.

read_ahead_kb (RW)

------------------

Maximum number of kilobytes to read-ahead for filesystems on this block

device.

rotational (RW)

---------------

This file is used to stat if the device is of rotational type or

non-rotational type.

rq_affinity (RW)

----------------

If this option is '1', the block layer will migrate request completions to the