Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.
1 dm-queue-length 2 =============== 3 4 dm-queue-length is a path selector module for device-mapper targets, 5 which selects a path with the least number of in-flight I/Os. 6 The path selector name is 'queue-length'. 7 8 Table parameters for each path: [<repeat_count>] 9 <repeat_count>: The number of I/Os to dispatch using the selected 10 path before switching to the next path. 11 If not given, internal default is used. To check 12 the default value, see the activated table. 13 14 Status for each path: <status> <fail-count> <in-flight> 15 <status>: 'A' if the path is active, 'F' if the path is failed. 16 <fail-count>: The number of path failures. 17 <in-flight>: The number of in-flight I/Os on the path. 18 19 20 Algorithm 21 ========= 22 23 dm-queue-length increments/decrements 'in-flight' when an I/O is 24 dispatched/completed respectively. 25 dm-queue-length selects a path with the minimum 'in-flight'. 26 27 28 Examples 29 ======== 30 In case that 2 paths (sda and sdb) are used with repeat_count == 128. 31 32 # echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \ 33 dmsetup create test 34 # 35 # dmsetup table 36 test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128 37 # 38 # dmsetup status 39 test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0