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diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block new file mode 100644 index 000000000000..cd14ecb3c9a5 --- /dev/null +++ b/Documentation/ABI/stable/sysfs-block @@ -0,0 +1,734 @@ +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 |