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Diffstat (limited to 'Documentation/block/queue-sysfs.txt')
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diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt deleted file mode 100644 index 7d2d046c265f..000000000000 --- a/Documentation/block/queue-sysfs.txt +++ /dev/null @@ -1,138 +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 are 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 trun off the disk entropy contribution. Default -value of this file is '1'(on). - -discard_granularity (RO) ------------------------ -This shows the size of internal allocation of the device in bytes, if -reported by the device. A value of '0' means device does not support -the discard functionality. - -discard_max_bytes (RO) ----------------------- -Devices that support discard functionality may have internal limits on -the number of bytes that can be trimmed or unmapped in a single operation. -The discard_max_bytes parameter is set by the device driver to the maximum -number of bytes that can be discarded in a single operation. Discard -requests issued to the device must not exceed this limit. A discard_max_bytes -value of 0 means that the device does not support discard functionality. - -discard_zeroes_data (RO) ------------------------- -When read, this file will show if the discarded block are zeroed by the -device or not. If its value is '1' the blocks are zeroed otherwise not. - -hw_sector_size (RO) -------------------- -This is the hardware sector size of the device, in bytes. - -iostats (RW) -------------- -This file is used to control (on/off) the iostats accounting of the -disk. - -logical_block_size (RO) ------------------------ -This is the logcal block size of the device, in bytes. - -max_hw_sectors_kb (RO) ----------------------- -This is the maximum number of kilobytes supported in a single data transfer. - -max_integrity_segments (RO) ---------------------------- -When read, this file shows the max limit of integrity segments as -set by block layer which a hardware controller can handle. - -max_sectors_kb (RW) -------------------- -This is the maximum number of kilobytes that the block layer will allow -for a filesystem request. Must be smaller than or equal to the maximum -size allowed by the hardware. - -max_segments (RO) ------------------ -Maximum number of segments of the device. - -max_segment_size (RO) ---------------------- -Maximum segment size of the device. - -minimum_io_size (RO) --------------------- -This is the smallest preferred io size reported by the device. - -nomerges (RW) -------------- -This enables the user to disable the lookup logic involved with IO -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. - -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. - - - -Jens Axboe <jens.axboe@oracle.com>, February 2009 |