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Commit 4004e90c authored by Namjae Jeon's avatar Namjae Jeon Committed by Jens Axboe
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Documentation: update tunable options in block/cfq-iosched.txt 



Update tunable options in block/cfq-iosched.txt.

Signed-off-by: default avatarNamjae Jeon <linkinjeon@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2792d871

Documentation/block/queue-sysfs.txt

+64 −0
Original line number Original line Diff line number Diff line
@@ -9,20 +9,71 @@ These files are the ones found in the /sys/block/xxx/queue/ directory. 
Files denoted with a RO postfix are readonly and the RW postfix means

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

read-write.

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)

hw_sector_size (RO)

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

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

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

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)

max_hw_sectors_kb (RO)

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

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

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

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)

max_sectors_kb (RW)

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

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

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

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

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

size allowed by the hardware.

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)

nomerges (RW)

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

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

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

This enables the user to disable the lookup logic involved with IO
@@ -45,11 +96,24 @@ per-block-cgroup request pool. IOW, if there are N block cgroups, 
each request queue may have upto N request pools, each independently

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

regulated by nr_requests.

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)

read_ahead_kb (RW)

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

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

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

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

device.

device.





rotational (RW)

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

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

non-rotational type.



rq_affinity (RW)

rq_affinity (RW)

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

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

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

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