diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-24 10:26:54 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-24 10:26:54 -0700 |
commit | c3cb5e193937c7aa50c323e7933507020bd26340 (patch) | |
tree | ea36213ccd29dc4caf2f729fd51b2d489b591a31 /Documentation/device-mapper/dm-queue-length.txt | |
parent | ea94b5034bbebc964115f119d6cd330757fce7f9 (diff) | |
parent | f40c67f0f7e2767f80f7cbcbc1ab86c4113c202e (diff) |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm
* git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm: (48 commits)
dm mpath: change to be request based
dm: disable interrupt when taking map_lock
dm: do not set QUEUE_ORDERED_DRAIN if request based
dm: enable request based option
dm: prepare for request based option
dm raid1: add userspace log
dm: calculate queue limits during resume not load
dm log: fix create_log_context to use logical_block_size of log device
dm target:s introduce iterate devices fn
dm table: establish queue limits by copying table limits
dm table: replace struct io_restrictions with struct queue_limits
dm table: validate device logical_block_size
dm table: ensure targets are aligned to logical_block_size
dm ioctl: support cookies for udev
dm: sysfs add suspended attribute
dm table: improve warning message when devices not freed before destruction
dm mpath: add service time load balancer
dm mpath: add queue length load balancer
dm mpath: add start_io and nr_bytes to path selectors
dm snapshot: use barrier when writing exception store
...
Diffstat (limited to 'Documentation/device-mapper/dm-queue-length.txt')
-rw-r--r-- | Documentation/device-mapper/dm-queue-length.txt | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/device-mapper/dm-queue-length.txt b/Documentation/device-mapper/dm-queue-length.txt new file mode 100644 index 00000000000..f4db2562175 --- /dev/null +++ b/Documentation/device-mapper/dm-queue-length.txt @@ -0,0 +1,39 @@ +dm-queue-length +=============== + +dm-queue-length is a path selector module for device-mapper targets, +which selects a path with the least number of in-flight I/Os. +The path selector name is 'queue-length'. + +Table parameters for each path: [<repeat_count>] + <repeat_count>: The number of I/Os to dispatch using the selected + path before switching to the next path. + If not given, internal default is used. To check + the default value, see the activated table. + +Status for each path: <status> <fail-count> <in-flight> + <status>: 'A' if the path is active, 'F' if the path is failed. + <fail-count>: The number of path failures. + <in-flight>: The number of in-flight I/Os on the path. + + +Algorithm +========= + +dm-queue-length increments/decrements 'in-flight' when an I/O is +dispatched/completed respectively. +dm-queue-length selects a path with the minimum 'in-flight'. + + +Examples +======== +In case that 2 paths (sda and sdb) are used with repeat_count == 128. + +# echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \ + dmsetup create test +# +# dmsetup table +test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128 +# +# dmsetup status +test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0 |