This series consolidates the documentation for /sys/block/<disk>/queue/
into Documentation/ABI/, where it is supposed to go (as per Greg KH:
https://lore.kernel.org/r/[email protected]).
This series also updates MAINTAINERS to associate the block
documentation with the block layer.
This series applies to linux-block/for-next.
Changed v2 => v3:
- Improved documentation for stable_writes and virt_boundary_mask.
- Added more Reviewed-by tags.
Changed v1 => v2:
- Added patch which moves the documentation to the stable directory.
- Added Reviewed-by tags.
Eric Biggers (8):
docs: sysfs-block: move to stable directory
docs: sysfs-block: sort alphabetically
docs: sysfs-block: add contact for nomerges
docs: sysfs-block: fill in missing documentation from queue-sysfs.rst
docs: sysfs-block: document stable_writes
docs: sysfs-block: document virt_boundary_mask
docs: block: remove queue-sysfs.rst
MAINTAINERS: add entries for block layer documentation
Documentation/ABI/stable/sysfs-block | 676 ++++++++++++++++++++++++++
Documentation/ABI/testing/sysfs-block | 346 -------------
Documentation/block/index.rst | 1 -
Documentation/block/queue-sysfs.rst | 321 ------------
MAINTAINERS | 2 +
5 files changed, 678 insertions(+), 668 deletions(-)
create mode 100644 Documentation/ABI/stable/sysfs-block
delete mode 100644 Documentation/ABI/testing/sysfs-block
delete mode 100644 Documentation/block/queue-sysfs.rst
base-commit: 2a7f2f5e3f0a18344b1a5d4ffa9307ffc9cbeee2
--
2.34.1
From: Eric Biggers <[email protected]>
This has been replaced by Documentation/ABI/stable/sysfs-block, which is
the correct place for sysfs documentation.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/block/index.rst | 1 -
Documentation/block/queue-sysfs.rst | 321 ----------------------------
2 files changed, 322 deletions(-)
delete mode 100644 Documentation/block/queue-sysfs.rst
diff --git a/Documentation/block/index.rst b/Documentation/block/index.rst
index 86dcf7159f990..3a41495dd77b5 100644
--- a/Documentation/block/index.rst
+++ b/Documentation/block/index.rst
@@ -20,7 +20,6 @@ Block
kyber-iosched
null_blk
pr
- queue-sysfs
request
stat
switching-sched
diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
deleted file mode 100644
index 3f569d5324857..0000000000000
--- a/Documentation/block/queue-sysfs.rst
+++ /dev/null
@@ -1,321 +0,0 @@
-=================
-Queue sysfs files
-=================
-
-This text file will detail the queue files that are located in the sysfs tree
-for each block device. Note that stacked devices typically do not export
-any settings, since their queue merely functions as a remapping target.
-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 turn off the disk entropy contribution. Default
-value of this file is '1'(on).
-
-chunk_sectors (RO)
-------------------
-This has different meaning depending on the type of the block device.
-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.
-
-dax (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.
-
-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_hw_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_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.
-
-discard_max_bytes (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.
-
-discard_zeroes_data (RO)
-------------------------
-Obsolete. Always zero.
-
-fua (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.
-
-hw_sector_size (RO)
--------------------
-This is the hardware sector size of the device, in bytes.
-
-io_poll (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.
-
-io_poll_delay (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.
-
-io_timeout (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.
-
-iostats (RW)
--------------
-This file is used to control (on/off) the iostats accounting of the
-disk.
-
-logical_block_size (RO)
------------------------
-This is the logical block size of the device, in bytes.
-
-max_discard_segments (RO)
--------------------------
-The maximum number of DMA scatter/gather entries in a discard request.
-
-max_hw_sectors_kb (RO)
-----------------------
-This is the maximum number of kilobytes supported in a single data transfer.
-
-max_integrity_segments (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.
-
-max_active_zones (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.
-
-max_open_zones (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.
-
-If the host attempts to exceed this limit, the driver should report this error
-with BLK_STS_ZONE_OPEN_RESOURCE, which user space may see as the ETOOMANYREFS
-errno.
-
-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 elements in a DMA scatter/gather list that is submitted
-to the associated block driver.
-
-max_segment_size (RO)
----------------------
-Maximum size in bytes of a single element in a DMA scatter/gather list.
-
-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
-merging requests in the block layer. By default (0) all merges are
-enabled. When set to 1 only simple one-hit merges will be tried. When
-set to 2 no merge algorithms will be tried (including one-hit or more
-complex tree/hash lookups).
-
-nr_requests (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.
-
-nr_zones (RO)
--------------
-For zoned block devices (zoned attribute indicating "host-managed" or
-"host-aware"), this indicates the total number of zones of the device.
-This is always 0 for regular block devices.
-
-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
-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).
-
-scheduler (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.
-
-write_cache (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.
-
-write_same_max_bytes (RO)
--------------------------
-This is the number of bytes the device can write in a single write-same
-command. A value of '0' means write-same is not supported by this
-device.
-
-wbt_lat_usec (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.
-
-throttle_sample_time (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.
-
-write_zeroes_max_bytes (RO)
----------------------------
-For block drivers that support REQ_OP_WRITE_ZEROES, the maximum number of
-bytes that can be zeroed at once. The value 0 means that REQ_OP_WRITE_ZEROES
-is not supported.
-
-zone_append_max_bytes (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.
-
-zoned (RO)
-----------
-This 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".
-
-zone_write_granularity (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.
-
-independent_access_ranges (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/<device>/queue/independent_access_ranges/
- /sys/block/<device>/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.
-
-Jens Axboe <[email protected]>, February 2009
--
2.34.1
From: Eric Biggers <[email protected]>
/sys/block/<disk>/queue/stable_writes is completely undocumented.
Document it.
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/ABI/stable/sysfs-block | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index de3b86a3dfa55..288626e8cb532 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -516,6 +516,23 @@ Description:
scheduler module, if it isn't already present in the system.
+What: /sys/block/<disk>/queue/stable_writes
+Date: September 2020
+Contact: [email protected]
+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: [email protected]
--
2.34.1
From: Eric Biggers <[email protected]>
Include Documentation/block/ and Documentation/ABI/stable/sysfs-block in
the "BLOCK LAYER" maintainers file entry.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
MAINTAINERS | 2 ++
1 file changed, 2 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 360e9aa0205d6..19db69dda15af 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3380,6 +3380,8 @@ M: Jens Axboe <[email protected]>
L: [email protected]
S: Maintained
T: git git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git
+F: Documentation/ABI/stable/sysfs-block
+F: Documentation/block/
F: block/
F: drivers/block/
F: include/linux/blk*
--
2.34.1
From: Eric Biggers <[email protected]>
/sys/block/<disk>/queue/virt_boundary_mask is completely undocumented.
Document it.
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/ABI/stable/sysfs-block | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index 288626e8cb532..8dd3e84a8aade 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -544,6 +544,18 @@ Description:
CONFIG_BLK_DEV_THROTTLING_LOW is enabled.
+What: /sys/block/<disk>/queue/virt_boundary_mask
+Date: April 2021
+Contact: [email protected]
+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: [email protected]
--
2.34.1
From: Eric Biggers <[email protected]>
sysfs documentation is supposed to go in Documentation/ABI/.
However, /sys/block/<disk>/queue/* are documented in
Documentation/block/queue-sysfs.rst, and sometimes redundantly in
Documentation/ABI/stable/sysfs-block too.
Let's consolidate this documentation into Documentation/ABI/.
Therefore, copy the relevant docs from queue-sysfs.rst into sysfs-block.
This primarily means adding the 25 missing files that were documented in
queue-sysfs.rst only, as well as mentioning the RO/RW status of files.
Documentation/ABI/ requires "Date" and "Contact" fields. For the Date
fields, I used the date of the commit which added support for each file.
For the "Contact" fields, I used linux-block.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/ABI/stable/sysfs-block | 482 +++++++++++++++++++++------
1 file changed, 381 insertions(+), 101 deletions(-)
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index c70fce6b76c17..de3b86a3dfa55 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -46,7 +46,7 @@ Description:
The value type is unsigned int.
Cf. Documentation/block/stat.rst which contains a single value for
requests in flight.
- This is related to nr_requests in Documentation/block/queue-sysfs.rst
+ This is related to /sys/block/<disk>/queue/nr_requests
and for SCSI device also its queue_depth.
@@ -134,207 +134,487 @@ Description:
same as the format of /sys/block/<disk>/stat.
+What: /sys/block/<disk>/queue/add_random
+Date: June 2010
+Contact: [email protected]
+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 <[email protected]>
Description:
- chunk_sectors has different meaning depending on the type
+ [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.
+ 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/dax
+Date: June 2016
+Contact: [email protected]
+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 <[email protected]>
Description:
- 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.
+ [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 <[email protected]>
Description:
- Devices that support discard functionality may have
- internal limits on the number of bytes that can be
- trimmed or unmapped in a single operation. Some storage
- protocols also have inherent limits on the number of
- blocks that can be described in a single command. 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.
+ [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: [email protected]
+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 <[email protected]>
Description:
- Will always return 0. Don't rely on any specific behavior
+ [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/fua
+Date: May 2018
+Contact: [email protected]
+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: [email protected]
+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: [email protected]
+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: [email protected]
+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: [email protected]
+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 <[email protected]>
Description:
- 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.
+ [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: [email protected]
+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 <[email protected]>
Description:
- This is the smallest unit the storage device can
- address. It is typically 512 bytes.
+ [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 <[email protected]>
Description:
- For zoned block devices (zoned attribute indicating
+ [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: [email protected]
+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: [email protected]
+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: [email protected]
+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 <[email protected]>
Description:
- For zoned block devices (zoned attribute indicating
+ [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.
+ 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: [email protected]
+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: [email protected]
+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: [email protected]
+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 <[email protected]>
Description:
- 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.
+ [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: [email protected]
Description:
- 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.
+ [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: [email protected]
+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 <[email protected]>
Description:
- 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.
+ [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 <[email protected]>
Description:
- 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.
+ [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 <[email protected]>
Description:
- 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.
+ [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: [email protected]
+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: [email protected]
+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: [email protected]
+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: [email protected]
+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/throttle_sample_time
+Date: March 2017
+Contact: [email protected]
+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/wbt_lat_usec
+Date: November 2016
+Contact: [email protected]
+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: [email protected]
+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 <[email protected]>
Description:
- Some devices support a write same operation in which a
+ [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.
+ 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 <[email protected]>
Description:
- 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.
+ [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: [email protected]
+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: [email protected]
+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 <[email protected]>
Description:
- 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".
+ [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
--
2.34.1
From: Eric Biggers <[email protected]>
Sort the documentation for the files alphabetically by file path so that
there is a logical order and it's clear where to add new files.
With two small exceptions, this patch doesn't change the documentation
itself and just reorders it:
- In /sys/block/<disk>/<part>/stat, I replaced <part> with <partition>
to be consistent with the other files.
- The description for /sys/block/<disk>/<part>/stat referred to another
file "above", which I reworded.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/ABI/stable/sysfs-block | 385 ++++++++++++++-------------
1 file changed, 203 insertions(+), 182 deletions(-)
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index b16b0c45a272e..9febd53a5ebe8 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -1,31 +1,37 @@
-What: /sys/block/<disk>/stat
-Date: February 2008
-Contact: Jerome Marchand <[email protected]>
+What: /sys/block/<disk>/alignment_offset
+Date: April 2009
+Contact: Martin K. Petersen <[email protected]>
Description:
- The /sys/block/<disk>/stat files displays the I/O
- statistics of disk <disk>. They contain 11 fields:
+ 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.
- == ==============================================
- 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
+What: /sys/block/<disk>/discard_alignment
+Date: May 2011
+Contact: Martin K. Petersen <[email protected]>
+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 <[email protected]>
+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
@@ -44,26 +50,12 @@ Description:
and for SCSI device also its queue_depth.
-What: /sys/block/<disk>/diskseq
-Date: February 2021
-Contact: Matteo Croce <[email protected]>
-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>/<part>/stat
-Date: February 2008
-Contact: Jerome Marchand <[email protected]>
+What: /sys/block/<disk>/integrity/device_is_integrity_capable
+Date: July 2014
+Contact: Martin K. Petersen <[email protected]>
Description:
- The /sys/block/<disk>/<part>/stat files display the
- I/O statistics of partition <part>. The format is the
- same as the above-written /sys/block/<disk>/stat
- format.
+ 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
@@ -74,6 +66,15 @@ Description:
E.g. T10-DIF-TYPE1-CRC.
+What: /sys/block/<disk>/integrity/protection_interval_bytes
+Date: July 2015
+Contact: Martin K. Petersen <[email protected]>
+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 <[email protected]>
@@ -91,21 +92,6 @@ Description:
512 bytes of data.
-What: /sys/block/<disk>/integrity/device_is_integrity_capable
-Date: July 2014
-Contact: Martin K. Petersen <[email protected]>
-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/protection_interval_bytes
-Date: July 2015
-Contact: Martin K. Petersen <[email protected]>
-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/write_generate
Date: June 2008
Contact: Martin K. Petersen <[email protected]>
@@ -114,16 +100,6 @@ Description:
generate checksums for write requests bound for
devices that support receiving integrity metadata.
-What: /sys/block/<disk>/alignment_offset
-Date: April 2009
-Contact: Martin K. Petersen <[email protected]>
-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>/<partition>/alignment_offset
Date: April 2009
@@ -136,76 +112,6 @@ Description:
indicates how many bytes the beginning of the partition
is offset from the disk's natural alignment.
-What: /sys/block/<disk>/queue/logical_block_size
-Date: May 2009
-Contact: Martin K. Petersen <[email protected]>
-Description:
- This is the smallest unit the storage device can
- address. It is typically 512 bytes.
-
-What: /sys/block/<disk>/queue/physical_block_size
-Date: May 2009
-Contact: Martin K. Petersen <[email protected]>
-Description:
- 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/minimum_io_size
-Date: April 2009
-Contact: Martin K. Petersen <[email protected]>
-Description:
- 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/optimal_io_size
-Date: April 2009
-Contact: Martin K. Petersen <[email protected]>
-Description:
- 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/nomerges
-Date: January 2010
-Contact:
-Description:
- 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>/discard_alignment
-Date: May 2011
-Contact: Martin K. Petersen <[email protected]>
-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>/<partition>/discard_alignment
Date: May 2011
@@ -218,6 +124,30 @@ Description:
partition is offset from the internal allocation unit's
natural alignment.
+
+What: /sys/block/<disk>/<partition>/stat
+Date: February 2008
+Contact: Jerome Marchand <[email protected]>
+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/chunk_sectors
+Date: September 2016
+Contact: Hannes Reinecke <[email protected]>
+Description:
+ 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/discard_granularity
Date: May 2011
Contact: Martin K. Petersen <[email protected]>
@@ -231,6 +161,7 @@ Description:
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 <[email protected]>
@@ -247,6 +178,7 @@ Description:
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 <[email protected]>
@@ -254,6 +186,111 @@ Description:
Will always return 0. Don't rely on any specific behavior
for discards, and don't read this file.
+
+What: /sys/block/<disk>/queue/io_timeout
+Date: November 2018
+Contact: Weiping Zhang <[email protected]>
+Description:
+ 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/logical_block_size
+Date: May 2009
+Contact: Martin K. Petersen <[email protected]>
+Description:
+ 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 <[email protected]>
+Description:
+ 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.
+
+
+What: /sys/block/<disk>/queue/max_open_zones
+Date: July 2020
+Contact: Niklas Cassel <[email protected]>
+Description:
+ 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/minimum_io_size
+Date: April 2009
+Contact: Martin K. Petersen <[email protected]>
+Description:
+ 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:
+Description:
+ 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_zones
+Date: November 2018
+Contact: Damien Le Moal <[email protected]>
+Description:
+ 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 <[email protected]>
+Description:
+ 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 <[email protected]>
+Description:
+ 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/write_same_max_bytes
Date: January 2012
Contact: Martin K. Petersen <[email protected]>
@@ -267,6 +304,7 @@ Description:
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 <[email protected]>
@@ -280,6 +318,7 @@ Description:
write_zeroes_max_bytes is 0, write zeroes is not supported
by the device.
+
What: /sys/block/<disk>/queue/zoned
Date: September 2016
Contact: Damien Le Moal <[email protected]>
@@ -297,50 +336,32 @@ Description:
zone commands, they will be treated as regular block
devices and zoned will report "none".
-What: /sys/block/<disk>/queue/nr_zones
-Date: November 2018
-Contact: Damien Le Moal <[email protected]>
-Description:
- 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/max_active_zones
-Date: July 2020
-Contact: Niklas Cassel <[email protected]>
-Description:
- 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.
-
-What: /sys/block/<disk>/queue/max_open_zones
-Date: July 2020
-Contact: Niklas Cassel <[email protected]>
+What: /sys/block/<disk>/stat
+Date: February 2008
+Contact: Jerome Marchand <[email protected]>
Description:
- 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.
+ The /sys/block/<disk>/stat files displays the I/O
+ statistics of disk <disk>. They contain 11 fields:
-What: /sys/block/<disk>/queue/chunk_sectors
-Date: September 2016
-Contact: Hannes Reinecke <[email protected]>
-Description:
- 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.
+ == ==============================================
+ 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)
+ == ==============================================
-What: /sys/block/<disk>/queue/io_timeout
-Date: November 2018
-Contact: Weiping Zhang <[email protected]>
-Description:
- 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.
+ For more details refer Documentation/admin-guide/iostats.rst
--
2.34.1
From: Eric Biggers <[email protected]>
The nomerges file was missing a "Contact" entry. Use linux-block.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
Documentation/ABI/stable/sysfs-block | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index 9febd53a5ebe8..c70fce6b76c17 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -242,7 +242,7 @@ Description:
What: /sys/block/<disk>/queue/nomerges
Date: January 2010
-Contact:
+Contact: [email protected]
Description:
Standard I/O elevator operations include attempts to
merge contiguous I/Os. For known random I/O loads these
--
2.34.1
On Wed, Dec 08, 2021 at 04:38:25PM -0800, Eric Biggers wrote:
> This series consolidates the documentation for /sys/block/<disk>/queue/
> into Documentation/ABI/, where it is supposed to go (as per Greg KH:
> https://lore.kernel.org/r/[email protected]).
>
> This series also updates MAINTAINERS to associate the block
> documentation with the block layer.
>
> This series applies to linux-block/for-next.
>
> Changed v2 => v3:
> - Improved documentation for stable_writes and virt_boundary_mask.
> - Added more Reviewed-by tags.
>
> Changed v1 => v2:
> - Added patch which moves the documentation to the stable directory.
> - Added Reviewed-by tags.
Jens, any interest in applying this series?
- Eric
On Tue, Dec 21, 2021 at 09:41:47AM -0600, Eric Biggers wrote:
> On Wed, Dec 08, 2021 at 04:38:25PM -0800, Eric Biggers wrote:
> > This series consolidates the documentation for /sys/block/<disk>/queue/
> > into Documentation/ABI/, where it is supposed to go (as per Greg KH:
> > https://lore.kernel.org/r/[email protected]).
> >
> > This series also updates MAINTAINERS to associate the block
> > documentation with the block layer.
> >
> > This series applies to linux-block/for-next.
> >
> > Changed v2 => v3:
> > - Improved documentation for stable_writes and virt_boundary_mask.
> > - Added more Reviewed-by tags.
> >
> > Changed v1 => v2:
> > - Added patch which moves the documentation to the stable directory.
> > - Added Reviewed-by tags.
>
> Jens, any interest in applying this series?
>
> - Eric
Ping.
On Mon, Jan 03, 2022 at 09:06:18AM -0600, Eric Biggers wrote:
> On Tue, Dec 21, 2021 at 09:41:47AM -0600, Eric Biggers wrote:
> > On Wed, Dec 08, 2021 at 04:38:25PM -0800, Eric Biggers wrote:
> > > This series consolidates the documentation for /sys/block/<disk>/queue/
> > > into Documentation/ABI/, where it is supposed to go (as per Greg KH:
> > > https://lore.kernel.org/r/[email protected]).
> > >
> > > This series also updates MAINTAINERS to associate the block
> > > documentation with the block layer.
> > >
> > > This series applies to linux-block/for-next.
> > >
> > > Changed v2 => v3:
> > > - Improved documentation for stable_writes and virt_boundary_mask.
> > > - Added more Reviewed-by tags.
> > >
> > > Changed v1 => v2:
> > > - Added patch which moves the documentation to the stable directory.
> > > - Added Reviewed-by tags.
> >
> > Jens, any interest in applying this series?
> >
> > - Eric
>
> Ping.
Jens, any reason you haven't applied this series yet? It looks like you've been
applying other patches. To be clear, I've been expecting that this would go in
through the block tree, rather than the docs tree.
- Eric
On 1/6/22 13:41, Eric Biggers wrote:
> Jens, any reason you haven't applied this series yet? It looks like you've been
> applying other patches. To be clear, I've been expecting that this would go in
> through the block tree, rather than the docs tree.
We are close to the v5.17 merge window so this is not a good time for a maintainer to
apply a large patch series. If Jens does not reply I propose to repost this patch
series after the v5.17 merge window has closed (three weeks from now?).
See also https://lore.kernel.org/lkml/CAHk-=wg=3dEpPGhz8YvJUDWhFW_GUeASBGmqyw3aPQRfB3ki9w@mail.gmail.com/
Thanks,
Bart.
On 1/7/22 1:58 PM, Bart Van Assche wrote:
> On 1/6/22 13:41, Eric Biggers wrote:
>> Jens, any reason you haven't applied this series yet? It looks like you've been
>> applying other patches. To be clear, I've been expecting that this would go in
>> through the block tree, rather than the docs tree.
>
> We are close to the v5.17 merge window so this is not a good time for a maintainer to
> apply a large patch series. If Jens does not reply I propose to repost this patch
> series after the v5.17 merge window has closed (three weeks from now?).
I'm fine with it, but it should probably just go through the doc tree.
--
Jens Axboe
On Sun, Jan 09, 2022 at 10:01:11AM -0700, Jens Axboe wrote:
> On 1/7/22 1:58 PM, Bart Van Assche wrote:
> > On 1/6/22 13:41, Eric Biggers wrote:
> >> Jens, any reason you haven't applied this series yet? It looks like you've been
> >> applying other patches. To be clear, I've been expecting that this would go in
> >> through the block tree, rather than the docs tree.
> >
> > We are close to the v5.17 merge window so this is not a good time for a maintainer to
> > apply a large patch series. If Jens does not reply I propose to repost this patch
> > series after the v5.17 merge window has closed (three weeks from now?).
>
> I'm fine with it, but it should probably just go through the doc tree.
I think it makes much more sense for subsystems to be responsible for their own
documentation; that's why patch 8 in this series adds the block layer
documentation to the block layer MAINTAINERS entry. Do you disagree with that?
- Eric
On 1/9/22 2:25 PM, Eric Biggers wrote:
> On Sun, Jan 09, 2022 at 10:01:11AM -0700, Jens Axboe wrote:
>> On 1/7/22 1:58 PM, Bart Van Assche wrote:
>>> On 1/6/22 13:41, Eric Biggers wrote:
>>>> Jens, any reason you haven't applied this series yet? It looks like you've been
>>>> applying other patches. To be clear, I've been expecting that this would go in
>>>> through the block tree, rather than the docs tree.
>>>
>>> We are close to the v5.17 merge window so this is not a good time for a maintainer to
>>> apply a large patch series. If Jens does not reply I propose to repost this patch
>>> series after the v5.17 merge window has closed (three weeks from now?).
>>
>> I'm fine with it, but it should probably just go through the doc tree.
>
> I think it makes much more sense for subsystems to be responsible for
> their own documentation; that's why patch 8 in this series adds the
> block layer documentation to the block layer MAINTAINERS entry. Do
> you disagree with that?
I agree, but then we often end up with merge conflicts between the doc
tree and others. That's why it's usually punted there. As a maintainer,
any conflicts is a pain in the butt to deal with, something the
contributor doesn't necessarily see or understand.
If there are no conflicts this time around, I can queue them up.
--
Jens Axboe
On Wed, 8 Dec 2021 16:38:25 -0800, Eric Biggers wrote:
> This series consolidates the documentation for /sys/block/<disk>/queue/
> into Documentation/ABI/, where it is supposed to go (as per Greg KH:
> https://lore.kernel.org/r/[email protected]).
>
> This series also updates MAINTAINERS to associate the block
> documentation with the block layer.
>
> [...]
Applied, thanks!
[1/8] docs: sysfs-block: move to stable directory
commit: ae7a7a53498f452eb927cd4b4eed0bccded85ebf
[2/8] docs: sysfs-block: sort alphabetically
commit: 07c9093c429361dd405499b1e433e4170b81551f
[3/8] docs: sysfs-block: add contact for nomerges
commit: 8b0551a74b4a9396a7f6ddb0c5f6f3c8465e9d45
[4/8] docs: sysfs-block: fill in missing documentation from queue-sysfs.rst
commit: 849ab826e10531f106846e8e9eeae8d00a198f6e
[5/8] docs: sysfs-block: document stable_writes
commit: 1163010418a7f0c60c309743498cb6c5cd828ecc
[6/8] docs: sysfs-block: document virt_boundary_mask
commit: 8bc2f7c67061cb39e317a45ad9870f529b1fb190
[7/8] docs: block: remove queue-sysfs.rst
commit: 208e4f9c0028e9181220460600b1df0bc677e796
[8/8] MAINTAINERS: add entries for block layer documentation
commit: f029cedb9bb5bab7f1bb3042be348f2dac0ee66e
Best regards,
--
Jens Axboe
Jens Axboe <[email protected]> writes:
> On 1/9/22 2:25 PM, Eric Biggers wrote:
>> I think it makes much more sense for subsystems to be responsible for
>> their own documentation; that's why patch 8 in this series adds the
>> block layer documentation to the block layer MAINTAINERS entry. Do
>> you disagree with that?
>
> I agree, but then we often end up with merge conflicts between the doc
> tree and others. That's why it's usually punted there. As a maintainer,
> any conflicts is a pain in the butt to deal with, something the
> contributor doesn't necessarily see or understand.
>
> If there are no conflicts this time around, I can queue them up.
[Docs maintainer not copied on any of this, but you can't escape :)]
Maintaining docs is a bit of a challenge for the reason Jens mentions:
everybody puts their fingers into it, and the result is lots of merge
conflicts. For that reason, I'd prefer that big changes go through the
docs tree. Changes to directories like Documentation/ABI can be
especially prone to conflicts, FWIW.
I also tend to be a bit more attentive to things like the addition of
docs-build warnings than maintainers from other subsystems.
That said, the real goal is to get more and better documentation merged,
and it often does make the most sense for docs changes to go through
other trees. Forcing the separation of documentation changes from the
code changes they reflect would be kind of silly at best, for example.
So if the block tree is the best path for these changes, then all I can
say is:
Acked-by: Jonathan Corbet <[email protected]>
Thanks,
jon