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Documentation: update tunable options in block/cfq-iosched.txt

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

Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Namjae Jeon 2012-08-09 15:28:05 +02:00 committed by Jens Axboe
parent 2792d87193
commit 4004e90cfa
1 changed files with 64 additions and 0 deletions
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64
Documentation/block/queue-sysfs.txt
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@ -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
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
@ -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
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