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r: 322227
b: refs/heads/master
c: 4004e90
h: refs/heads/master
i:
  322225: 899b83c
  322223: 87ec1ac
v: v3
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Namjae Jeon authored and Jens Axboe committed Aug 9, 2012
1 parent c824c4a commit 884d9d1
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2 changes: 1 addition & 1 deletion [refs]
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---
refs/heads/master: 2792d8719393a518a847769d36a080ade4273e6b
refs/heads/master: 4004e90cfa4488cf99798b1138183158b64f4a42
64 changes: 64 additions & 0 deletions trunk/Documentation/block/queue-sysfs.txt
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Expand Up @@ -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
Expand All @@ -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
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