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linux-imx/Documentation/ABI/testing/sysfs-block-dm
Mike Snitzer 17e149b8f7 dm: add 'use_blk_mq' module param and expose in per-device ro sysfs attr 
Request-based DM's blk-mq support defaults to off; but a user can easily
change the default using the dm_mod.use_blk_mq module/boot option.

Also, you can check what mode a given request-based DM device is using
with: cat /sys/block/dm-X/dm/use_blk_mq

This change enabled further cleanup and reduced work (e.g. the
md->io_pool and md->rq_pool isn't created if using blk-mq).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-04-15 12:10:17 -04:00

1.6 KiB
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What: /sys/block/dm-/dm/name Date: January 2009 KernelVersion: 2.6.29 Contact: dm-devel@redhat.com Description: Device-mapper device name. Read-only string containing mapped device name. Users: util-linux, device-mapper udev rules

What: /sys/block/dm-/dm/uuid Date: January 2009 KernelVersion: 2.6.29 Contact: dm-devel@redhat.com Description: Device-mapper device UUID. Read-only string containing DM-UUID or empty string if DM-UUID is not set. Users: util-linux, device-mapper udev rules

What: /sys/block/dm-/dm/suspended Date: June 2009 KernelVersion: 2.6.31 Contact: dm-devel@redhat.com Description: Device-mapper device suspend state. Contains the value 1 while the device is suspended. Otherwise it contains 0. Read-only attribute. Users: util-linux, device-mapper udev rules

What: /sys/block/dm-/dm/rq_based_seq_io_merge_deadline Date: March 2015 KernelVersion: 4.1 Contact: dm-devel@redhat.com Description: Allow control over how long a request that is a reasonable merge candidate can be queued on the request queue. The resolution of this deadline is in microseconds (ranging from 1 to 100000 usecs). Setting this attribute to 0 (the default) will disable request-based DM's merge heuristic and associated extra accounting. This attribute is not applicable to bio-based DM devices so it will only ever report 0 for them.

What: /sys/block/dm-/dm/use_blk_mq Date: March 2015 KernelVersion: 4.1 Contact: dm-devel@redhat.com Description: Request-based Device-mapper blk-mq I/O path mode. Contains the value 1 if the device is using blk-mq. Otherwise it contains 0. Read-only attribute.