From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/device-mapper/dm-queue-length.txt | 39 +++++++++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 Documentation/device-mapper/dm-queue-length.txt (limited to 'Documentation/device-mapper/dm-queue-length.txt') diff --git a/Documentation/device-mapper/dm-queue-length.txt b/Documentation/device-mapper/dm-queue-length.txt new file mode 100644 index 00000000..f4db2562 --- /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: [] + : 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: + : 'A' if the path is active, 'F' if the path is failed. + : The number of path failures. + : 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 -- cgit v1.2.3