mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-14 06:24:53 +08:00
3850e13f28
User space may want to know how to align their buffers to avoid bouncing. Export the queue attribute. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220610195830.3574005-4-kbusch@fb.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
735 lines
26 KiB
Plaintext
735 lines
26 KiB
Plaintext
What: /sys/block/<disk>/alignment_offset
|
|
Date: April 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Storage devices may report a physical block size that is
|
|
bigger than the logical block size (for instance a drive
|
|
with 4KB physical sectors exposing 512-byte logical
|
|
blocks to the operating system). This parameter
|
|
indicates how many bytes the beginning of the device is
|
|
offset from the disk's natural alignment.
|
|
|
|
|
|
What: /sys/block/<disk>/discard_alignment
|
|
Date: May 2011
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Devices that support discard functionality may
|
|
internally allocate space in units that are bigger than
|
|
the exported logical block size. The discard_alignment
|
|
parameter indicates how many bytes the beginning of the
|
|
device is offset from the internal allocation unit's
|
|
natural alignment.
|
|
|
|
|
|
What: /sys/block/<disk>/diskseq
|
|
Date: February 2021
|
|
Contact: Matteo Croce <mcroce@microsoft.com>
|
|
Description:
|
|
The /sys/block/<disk>/diskseq files reports the disk
|
|
sequence number, which is a monotonically increasing
|
|
number assigned to every drive.
|
|
Some devices, like the loop device, refresh such number
|
|
every time the backing file is changed.
|
|
The value type is 64 bit unsigned.
|
|
|
|
|
|
What: /sys/block/<disk>/inflight
|
|
Date: October 2009
|
|
Contact: Jens Axboe <axboe@kernel.dk>, Nikanth Karthikesan <knikanth@suse.de>
|
|
Description:
|
|
Reports the number of I/O requests currently in progress
|
|
(pending / in flight) in a device driver. This can be less
|
|
than the number of requests queued in the block device queue.
|
|
The report contains 2 fields: one for read requests
|
|
and one for write requests.
|
|
The value type is unsigned int.
|
|
Cf. Documentation/block/stat.rst which contains a single value for
|
|
requests in flight.
|
|
This is related to /sys/block/<disk>/queue/nr_requests
|
|
and for SCSI device also its queue_depth.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/device_is_integrity_capable
|
|
Date: July 2014
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Indicates whether a storage device is capable of storing
|
|
integrity metadata. Set if the device is T10 PI-capable.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/format
|
|
Date: June 2008
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Metadata format for integrity capable block device.
|
|
E.g. T10-DIF-TYPE1-CRC.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/protection_interval_bytes
|
|
Date: July 2015
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Describes the number of data bytes which are protected
|
|
by one integrity tuple. Typically the device's logical
|
|
block size.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/read_verify
|
|
Date: June 2008
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Indicates whether the block layer should verify the
|
|
integrity of read requests serviced by devices that
|
|
support sending integrity metadata.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/tag_size
|
|
Date: June 2008
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Number of bytes of integrity tag space available per
|
|
512 bytes of data.
|
|
|
|
|
|
What: /sys/block/<disk>/integrity/write_generate
|
|
Date: June 2008
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Indicates whether the block layer should automatically
|
|
generate checksums for write requests bound for
|
|
devices that support receiving integrity metadata.
|
|
|
|
|
|
What: /sys/block/<disk>/<partition>/alignment_offset
|
|
Date: April 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Storage devices may report a physical block size that is
|
|
bigger than the logical block size (for instance a drive
|
|
with 4KB physical sectors exposing 512-byte logical
|
|
blocks to the operating system). This parameter
|
|
indicates how many bytes the beginning of the partition
|
|
is offset from the disk's natural alignment.
|
|
|
|
|
|
What: /sys/block/<disk>/<partition>/discard_alignment
|
|
Date: May 2011
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
Devices that support discard functionality may
|
|
internally allocate space in units that are bigger than
|
|
the exported logical block size. The discard_alignment
|
|
parameter indicates how many bytes the beginning of the
|
|
partition is offset from the internal allocation unit's
|
|
natural alignment.
|
|
|
|
|
|
What: /sys/block/<disk>/<partition>/stat
|
|
Date: February 2008
|
|
Contact: Jerome Marchand <jmarchan@redhat.com>
|
|
Description:
|
|
The /sys/block/<disk>/<partition>/stat files display the
|
|
I/O statistics of partition <partition>. The format is the
|
|
same as the format of /sys/block/<disk>/stat.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/add_random
|
|
Date: June 2010
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This file allows to turn off the disk entropy contribution.
|
|
Default value of this file is '1'(on).
|
|
|
|
|
|
What: /sys/block/<disk>/queue/chunk_sectors
|
|
Date: September 2016
|
|
Contact: Hannes Reinecke <hare@suse.com>
|
|
Description:
|
|
[RO] chunk_sectors has different meaning depending on the type
|
|
of the disk. For a RAID device (dm-raid), chunk_sectors
|
|
indicates the size in 512B sectors of the RAID volume stripe
|
|
segment. For a zoned block device, either host-aware or
|
|
host-managed, chunk_sectors indicates the size in 512B sectors
|
|
of the zones of the device, with the eventual exception of the
|
|
last zone of the device which may be smaller.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/crypto/
|
|
Date: February 2022
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
The presence of this subdirectory of /sys/block/<disk>/queue/
|
|
indicates that the device supports inline encryption. This
|
|
subdirectory contains files which describe the inline encryption
|
|
capabilities of the device. For more information about inline
|
|
encryption, refer to Documentation/block/inline-encryption.rst.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/crypto/max_dun_bits
|
|
Date: February 2022
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This file shows the maximum length, in bits, of data unit
|
|
numbers accepted by the device in inline encryption requests.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/crypto/modes/<mode>
|
|
Date: February 2022
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] For each crypto mode (i.e., encryption/decryption
|
|
algorithm) the device supports with inline encryption, a file
|
|
will exist at this location. It will contain a hexadecimal
|
|
number that is a bitmask of the supported data unit sizes, in
|
|
bytes, for that crypto mode.
|
|
|
|
Currently, the crypto modes that may be supported are:
|
|
|
|
* AES-256-XTS
|
|
* AES-128-CBC-ESSIV
|
|
* Adiantum
|
|
|
|
For example, if a device supports AES-256-XTS inline encryption
|
|
with data unit sizes of 512 and 4096 bytes, the file
|
|
/sys/block/<disk>/queue/crypto/modes/AES-256-XTS will exist and
|
|
will contain "0x1200".
|
|
|
|
|
|
What: /sys/block/<disk>/queue/crypto/num_keyslots
|
|
Date: February 2022
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This file shows the number of keyslots the device has for
|
|
use with inline encryption.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/dax
|
|
Date: June 2016
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This file indicates whether the device supports Direct
|
|
Access (DAX), used by CPU-addressable storage to bypass the
|
|
pagecache. It shows '1' if true, '0' if not.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/discard_granularity
|
|
Date: May 2011
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] Devices that support discard functionality may internally
|
|
allocate space using units that are bigger than the logical
|
|
block size. The discard_granularity parameter indicates the size
|
|
of the internal allocation unit in bytes if reported by the
|
|
device. Otherwise the discard_granularity will be set to match
|
|
the device's physical block size. A discard_granularity of 0
|
|
means that the device does not support discard functionality.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/discard_max_bytes
|
|
Date: May 2011
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RW] While discard_max_hw_bytes is the hardware limit for the
|
|
device, this setting is the software limit. Some devices exhibit
|
|
large latencies when large discards are issued, setting this
|
|
value lower will make Linux issue smaller discards and
|
|
potentially help reduce latencies induced by large discard
|
|
operations.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/discard_max_hw_bytes
|
|
Date: July 2015
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[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_hw_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_hw_bytes` value of 0 means that the device does not
|
|
support discard functionality.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/discard_zeroes_data
|
|
Date: May 2011
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] Will always return 0. Don't rely on any specific behavior
|
|
for discards, and don't read this file.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/dma_alignment
|
|
Date: May 2022
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
Reports the alignment that user space addresses must have to be
|
|
used for raw block device access with O_DIRECT and other driver
|
|
specific passthrough mechanisms.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/fua
|
|
Date: May 2018
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] Whether or not the block driver supports the FUA flag for
|
|
write requests. FUA stands for Force Unit Access. If the FUA
|
|
flag is set that means that write requests must bypass the
|
|
volatile cache of the storage device.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/hw_sector_size
|
|
Date: January 2008
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This is the hardware sector size of the device, in bytes.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/independent_access_ranges/
|
|
Date: October 2021
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] The presence of this sub-directory of the
|
|
/sys/block/xxx/queue/ directory indicates that the device is
|
|
capable of executing requests targeting different sector ranges
|
|
in parallel. For instance, single LUN multi-actuator hard-disks
|
|
will have an independent_access_ranges directory if the device
|
|
correctly advertizes the sector ranges of its actuators.
|
|
|
|
The independent_access_ranges directory contains one directory
|
|
per access range, with each range described using the sector
|
|
(RO) attribute file to indicate the first sector of the range
|
|
and the nr_sectors (RO) attribute file to indicate the total
|
|
number of sectors in the range starting from the first sector of
|
|
the range. For example, a dual-actuator hard-disk will have the
|
|
following independent_access_ranges entries.::
|
|
|
|
$ tree /sys/block/<disk>/queue/independent_access_ranges/
|
|
/sys/block/<disk>/queue/independent_access_ranges/
|
|
|-- 0
|
|
| |-- nr_sectors
|
|
| `-- sector
|
|
`-- 1
|
|
|-- nr_sectors
|
|
`-- sector
|
|
|
|
The sector and nr_sectors attributes use 512B sector unit,
|
|
regardless of the actual block size of the device. Independent
|
|
access ranges do not overlap and include all sectors within the
|
|
device capacity. The access ranges are numbered in increasing
|
|
order of the range start sector, that is, the sector attribute
|
|
of range 0 always has the value 0.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/io_poll
|
|
Date: November 2015
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] When read, this file shows whether polling is enabled (1)
|
|
or disabled (0). Writing '0' to this file will disable polling
|
|
for this device. Writing any non-zero value will enable this
|
|
feature.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/io_poll_delay
|
|
Date: November 2016
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] If polling is enabled, this controls what kind of polling
|
|
will be performed. It defaults to -1, which is classic polling.
|
|
In this mode, the CPU will repeatedly ask for completions
|
|
without giving up any time. If set to 0, a hybrid polling mode
|
|
is used, where the kernel will attempt to make an educated guess
|
|
at when the IO will complete. Based on this guess, the kernel
|
|
will put the process issuing IO to sleep for an amount of time,
|
|
before entering a classic poll loop. This mode might be a little
|
|
slower than pure classic polling, but it will be more efficient.
|
|
If set to a value larger than 0, the kernel will put the process
|
|
issuing IO to sleep for this amount of microseconds before
|
|
entering classic polling.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/io_timeout
|
|
Date: November 2018
|
|
Contact: Weiping Zhang <zhangweiping@didiglobal.com>
|
|
Description:
|
|
[RW] io_timeout is the request timeout in milliseconds. If a
|
|
request does not complete in this time then the block driver
|
|
timeout handler is invoked. That timeout handler can decide to
|
|
retry the request, to fail it or to start a device recovery
|
|
strategy.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/iostats
|
|
Date: January 2009
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This file is used to control (on/off) the iostats
|
|
accounting of the disk.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/logical_block_size
|
|
Date: May 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] This is the smallest unit the storage device can address.
|
|
It is typically 512 bytes.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_active_zones
|
|
Date: July 2020
|
|
Contact: Niklas Cassel <niklas.cassel@wdc.com>
|
|
Description:
|
|
[RO] For zoned block devices (zoned attribute indicating
|
|
"host-managed" or "host-aware"), the sum of zones belonging to
|
|
any of the zone states: EXPLICIT OPEN, IMPLICIT OPEN or CLOSED,
|
|
is limited by this value. If this value is 0, there is no limit.
|
|
|
|
If the host attempts to exceed this limit, the driver should
|
|
report this error with BLK_STS_ZONE_ACTIVE_RESOURCE, which user
|
|
space may see as the EOVERFLOW errno.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_discard_segments
|
|
Date: February 2017
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] The maximum number of DMA scatter/gather entries in a
|
|
discard request.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_hw_sectors_kb
|
|
Date: September 2004
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This is the maximum number of kilobytes supported in a
|
|
single data transfer.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_integrity_segments
|
|
Date: September 2010
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] Maximum number of elements in a DMA scatter/gather list
|
|
with integrity data that will be submitted by the block layer
|
|
core to the associated block driver.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_open_zones
|
|
Date: July 2020
|
|
Contact: Niklas Cassel <niklas.cassel@wdc.com>
|
|
Description:
|
|
[RO] For zoned block devices (zoned attribute indicating
|
|
"host-managed" or "host-aware"), the sum of zones belonging to
|
|
any of the zone states: EXPLICIT OPEN or IMPLICIT OPEN, is
|
|
limited by this value. If this value is 0, there is no limit.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_sectors_kb
|
|
Date: September 2004
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[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.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_segment_size
|
|
Date: March 2010
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] Maximum size in bytes of a single element in a DMA
|
|
scatter/gather list.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/max_segments
|
|
Date: March 2010
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] Maximum number of elements in a DMA scatter/gather list
|
|
that is submitted to the associated block driver.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/minimum_io_size
|
|
Date: April 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] Storage devices may report a granularity or preferred
|
|
minimum I/O size which is the smallest request the device can
|
|
perform without incurring a performance penalty. For disk
|
|
drives this is often the physical block size. For RAID arrays
|
|
it is often the stripe chunk size. A properly aligned multiple
|
|
of minimum_io_size is the preferred request size for workloads
|
|
where a high number of I/O operations is desired.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/nomerges
|
|
Date: January 2010
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] Standard I/O elevator operations include attempts to merge
|
|
contiguous I/Os. For known random I/O loads these attempts will
|
|
always fail and result in extra cycles being spent in the
|
|
kernel. This allows one to turn off this behavior on one of two
|
|
ways: When set to 1, complex merge checks are disabled, but the
|
|
simple one-shot merges with the previous I/O request are
|
|
enabled. When set to 2, all merge tries are disabled. The
|
|
default value is 0 - which enables all types of merge tries.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/nr_requests
|
|
Date: July 2003
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This controls how many requests may be allocated in the
|
|
block layer for read or write requests. Note that the total
|
|
allocated number may be twice this amount, since it applies only
|
|
to reads or writes (not the accumulated sum).
|
|
|
|
To avoid priority inversion through request starvation, a
|
|
request queue maintains a separate request pool per each cgroup
|
|
when CONFIG_BLK_CGROUP is enabled, and this parameter applies to
|
|
each such per-block-cgroup request pool. IOW, if there are N
|
|
block cgroups, each request queue may have up to N request
|
|
pools, each independently regulated by nr_requests.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/nr_zones
|
|
Date: November 2018
|
|
Contact: Damien Le Moal <damien.lemoal@wdc.com>
|
|
Description:
|
|
[RO] nr_zones indicates the total number of zones of a zoned
|
|
block device ("host-aware" or "host-managed" zone model). For
|
|
regular block devices, the value is always 0.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/optimal_io_size
|
|
Date: April 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] Storage devices may report an optimal I/O size, which is
|
|
the device's preferred unit for sustained I/O. This is rarely
|
|
reported for disk drives. For RAID arrays it is usually the
|
|
stripe width or the internal track size. A properly aligned
|
|
multiple of optimal_io_size is the preferred request size for
|
|
workloads where sustained throughput is desired. If no optimal
|
|
I/O size is reported this file contains 0.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/physical_block_size
|
|
Date: May 2009
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] This is the smallest unit a physical storage device can
|
|
write atomically. It is usually the same as the logical block
|
|
size but may be bigger. One example is SATA drives with 4KB
|
|
sectors that expose a 512-byte logical block size to the
|
|
operating system. For stacked block devices the
|
|
physical_block_size variable contains the maximum
|
|
physical_block_size of the component devices.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/read_ahead_kb
|
|
Date: May 2004
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] Maximum number of kilobytes to read-ahead for filesystems
|
|
on this block device.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/rotational
|
|
Date: January 2009
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This file is used to stat if the device is of rotational
|
|
type or non-rotational type.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/rq_affinity
|
|
Date: September 2008
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] If this option is '1', the block layer will migrate request
|
|
completions to the cpu "group" that originally submitted the
|
|
request. For some workloads this provides a significant
|
|
reduction in CPU cycles due to caching effects.
|
|
|
|
For storage configurations that need to maximize distribution of
|
|
completion processing setting this option to '2' forces the
|
|
completion to run on the requesting cpu (bypassing the "group"
|
|
aggregation logic).
|
|
|
|
|
|
What: /sys/block/<disk>/queue/scheduler
|
|
Date: October 2004
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] When read, this file will display the current and available
|
|
IO schedulers for this block device. The currently active IO
|
|
scheduler will be enclosed in [] brackets. Writing an IO
|
|
scheduler name to this file will switch control of this block
|
|
device to that new IO scheduler. Note that writing an IO
|
|
scheduler name to this file will attempt to load that IO
|
|
scheduler module, if it isn't already present in the system.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/stable_writes
|
|
Date: September 2020
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This file will contain '1' if memory must not be modified
|
|
while it is being used in a write request to this device. When
|
|
this is the case and the kernel is performing writeback of a
|
|
page, the kernel will wait for writeback to complete before
|
|
allowing the page to be modified again, rather than allowing
|
|
immediate modification as is normally the case. This
|
|
restriction arises when the device accesses the memory multiple
|
|
times where the same data must be seen every time -- for
|
|
example, once to calculate a checksum and once to actually write
|
|
the data. If no such restriction exists, this file will contain
|
|
'0'. This file is writable for testing purposes.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/throttle_sample_time
|
|
Date: March 2017
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] This is the time window that blk-throttle samples data, in
|
|
millisecond. blk-throttle makes decision based on the
|
|
samplings. Lower time means cgroups have more smooth throughput,
|
|
but higher CPU overhead. This exists only when
|
|
CONFIG_BLK_DEV_THROTTLING_LOW is enabled.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/virt_boundary_mask
|
|
Date: April 2021
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This file shows the I/O segment memory alignment mask for
|
|
the block device. I/O requests to this device will be split
|
|
between segments wherever either the memory address of the end
|
|
of the previous segment or the memory address of the beginning
|
|
of the current segment is not aligned to virt_boundary_mask + 1
|
|
bytes.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/wbt_lat_usec
|
|
Date: November 2016
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] If the device is registered for writeback throttling, then
|
|
this file shows the target minimum read latency. If this latency
|
|
is exceeded in a given window of time (see wb_window_usec), then
|
|
the writeback throttling will start scaling back writes. Writing
|
|
a value of '0' to this file disables the feature. Writing a
|
|
value of '-1' to this file resets the value to the default
|
|
setting.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/write_cache
|
|
Date: April 2016
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RW] When read, this file will display whether the device has
|
|
write back caching enabled or not. It will return "write back"
|
|
for the former case, and "write through" for the latter. Writing
|
|
to this file can change the kernels view of the device, but it
|
|
doesn't alter the device state. This means that it might not be
|
|
safe to toggle the setting from "write back" to "write through",
|
|
since that will also eliminate cache flushes issued by the
|
|
kernel.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/write_same_max_bytes
|
|
Date: January 2012
|
|
Contact: Martin K. Petersen <martin.petersen@oracle.com>
|
|
Description:
|
|
[RO] Some devices support a write same operation in which a
|
|
single data block can be written to a range of several
|
|
contiguous blocks on storage. This can be used to wipe areas on
|
|
disk or to initialize drives in a RAID configuration.
|
|
write_same_max_bytes indicates how many bytes can be written in
|
|
a single write same command. If write_same_max_bytes is 0, write
|
|
same is not supported by the device.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/write_zeroes_max_bytes
|
|
Date: November 2016
|
|
Contact: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
|
|
Description:
|
|
[RO] Devices that support write zeroes operation in which a
|
|
single request can be issued to zero out the range of contiguous
|
|
blocks on storage without having any payload in the request.
|
|
This can be used to optimize writing zeroes to the devices.
|
|
write_zeroes_max_bytes indicates how many bytes can be written
|
|
in a single write zeroes command. If write_zeroes_max_bytes is
|
|
0, write zeroes is not supported by the device.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/zone_append_max_bytes
|
|
Date: May 2020
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This is the maximum number of bytes that can be written to
|
|
a sequential zone of a zoned block device using a zone append
|
|
write operation (REQ_OP_ZONE_APPEND). This value is always 0 for
|
|
regular block devices.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/zone_write_granularity
|
|
Date: January 2021
|
|
Contact: linux-block@vger.kernel.org
|
|
Description:
|
|
[RO] This indicates the alignment constraint, in bytes, for
|
|
write operations in sequential zones of zoned block devices
|
|
(devices with a zoned attributed that reports "host-managed" or
|
|
"host-aware"). This value is always 0 for regular block devices.
|
|
|
|
|
|
What: /sys/block/<disk>/queue/zoned
|
|
Date: September 2016
|
|
Contact: Damien Le Moal <damien.lemoal@wdc.com>
|
|
Description:
|
|
[RO] zoned indicates if the device is a zoned block device and
|
|
the zone model of the device if it is indeed zoned. The
|
|
possible values indicated by zoned are "none" for regular block
|
|
devices and "host-aware" or "host-managed" for zoned block
|
|
devices. The characteristics of host-aware and host-managed
|
|
zoned block devices are described in the ZBC (Zoned Block
|
|
Commands) and ZAC (Zoned Device ATA Command Set) standards.
|
|
These standards also define the "drive-managed" zone model.
|
|
However, since drive-managed zoned block devices do not support
|
|
zone commands, they will be treated as regular block devices and
|
|
zoned will report "none".
|
|
|
|
|
|
What: /sys/block/<disk>/stat
|
|
Date: February 2008
|
|
Contact: Jerome Marchand <jmarchan@redhat.com>
|
|
Description:
|
|
The /sys/block/<disk>/stat files displays the I/O
|
|
statistics of disk <disk>. They contain 11 fields:
|
|
|
|
== ==============================================
|
|
1 reads completed successfully
|
|
2 reads merged
|
|
3 sectors read
|
|
4 time spent reading (ms)
|
|
5 writes completed
|
|
6 writes merged
|
|
7 sectors written
|
|
8 time spent writing (ms)
|
|
9 I/Os currently in progress
|
|
10 time spent doing I/Os (ms)
|
|
11 weighted time spent doing I/Os (ms)
|
|
12 discards completed
|
|
13 discards merged
|
|
14 sectors discarded
|
|
15 time spent discarding (ms)
|
|
16 flush requests completed
|
|
17 time spent flushing (ms)
|
|
== ==============================================
|
|
|
|
For more details refer Documentation/admin-guide/iostats.rst
|