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Diffstat (limited to 'Documentation/block/queue-sysfs.rst')
| -rw-r--r-- | Documentation/block/queue-sysfs.rst | 42 |
1 files changed, 37 insertions, 5 deletions
diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst index 4dc7f0d499a8..3f569d532485 100644 --- a/Documentation/block/queue-sysfs.rst +++ b/Documentation/block/queue-sysfs.rst @@ -4,7 +4,7 @@ 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 are a remapping target. +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 @@ -40,10 +40,11 @@ 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_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. +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) ---------------------- @@ -286,4 +287,35 @@ 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 <jens.axboe@oracle.com>, February 2009 |